Model Engine Maker

Engines => Your Own Design => Topic started by: gary.a.ayres on April 27, 2020, 12:11:04 AM

Title: A Simple Uniflow Engine
Post by: gary.a.ayres on April 27, 2020, 12:11:04 AM
Hello All.

It has been a while, what with everything that is going on.

Hope you are all ok...

Finally and at last, I have made a start on my second engine. A slightly unusual one, this.

First of all, the 'simple' in the title of the thread refers to the simplicity of the concept of the engine. It does not mean that I think I'll find this build simple.

The design upon which I am basing the working heart of the engine is by Stan Bray. It's 'Clarence - a clapper valve engine'' from his book on building simple model steam engines:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/859112.jpg)

I don't like the sound of 'clapper valve', so I'm describing my version as a 'uniflow', which I believe it is, albeit a simple example of the type. I am taking the basic working concepts and the relative dimensions of the working parts from the book. There, however, the similarity will end - mine will have a very different look, and it will be at least three times the size of the original, which has only a 10 mm bore.

Essentially this engine will be scratch built. I have an overall idea in my mind but I'll let it unfold as the thread progresses rather than set it all out here, particularly as the plan will most likely change as I go along.

I decided to start with the flywheel - or I should say flywheels. I have had these two brass discs in my parts box for some time. They are about 11.5 cm in diameter. Originally I had thought of somehow joining them to make one chunky flywheel, but I have now decided that the engine will have twin flywheels. This, along with my idea for a frame, will have implications for some of the engineering further down the line. For the crankshaft, the bigger of the two pieces of precision ground mild steel is a bit heavier than I would have chosen, but I have it in my shop and I fancy pursuing a 'use what you have' aesthetic as far as possible with this build:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/859113.jpg)

The flywheels will be composite in nature, each having a central boss  made from a separate piece of brass. They will also have a pattern of holes so I had to drill out and bore the centres so that they will fit the small four-jaw chuck which is mounted on my rotary table:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/859114.jpg)

So, a small start has been made.

This will be a fairly chunky engine and it will need a fairly powerful boiler to run it. More of that later...


Title: Re: A Simple Uniflow Engine
Post by: MJM460 on April 27, 2020, 01:19:49 PM
Hi Gary, good to see you building another engine.  I am looking forward to seeing what you will do to put your mark on this one.

The design seems to have much in common with the principles used in a high speed hydroplane which was written up in the magazine.  However that was was a very highly developed performance monster. Yours looks much more reasonable, but who knows where it will lead.

K.N Harris mention the uni flow principle in his book.  You might be interested to know that that is the one that really got me interested in applying thermodynamics (which was central to my working life) to understanding in some detail how this helped understanding our models, and ultimately lead to my Talking Thermodynamics thread.

So not really sitting back, as I seem to be busier than ever these days, but looking forward to following along with your new build.

By the way, how is your flash steam plant going? 

MJM460
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 27, 2020, 10:49:46 PM
Hi MJM, and thanks.

My hunch  is that if I make a reasonable job of this it will be a fast runner. I have the K.N. Harris book, and yes, the uniflow engines he describes seem to be of more complex designs.

I haven't progressed the flash steam generator for quite some time as I got 'diverted' into building a brake drum forge. I always considered the flash generator to be something of a side project anyway. That said, I have a sense that something of the sort could be well suited to this engine though I have a feeling I'd need a bigger coil, which would be easy enough to do.

However, I also have other plans when it comes to boilers. Not going to say any more about that at the moment as I don't want to jinx it!   ;)

Hope you are doing ok with the challenges of the pandemic. Are you still in lockdown in Australia?

Cheers,

Gary
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on April 28, 2020, 08:19:19 AM
Hi Gary, the engine you are making is very similar in principle to that high speed hydroplane, Pisces, that I mentioned, though yours will be a more appropriately gentle one to tame.  The hydroplane had the principle refined, and the manufacture developed way beyond anything I could imagine doing.

The K.N. Harris design was closer to yours in performance, but added the ďuni flowĒ exhaust ports to a more conventional engine, to get more power output.

Yours will be quite economical on steam as the inlet port will only be open briefly, thus allowing for plenty of work to be developed through expansion.  It will be happier running faster, and the overall performance will be interesting to look forward to.  Most simple engines, the inlet valve is open for longer, so they do admit more steam, then simple exhaust it to atmosphere rather than achieving so much expansion.  In the end it is all about valve port timing and there is a big variation between different designs.

With that design, the inlet port opens before dead centre, so this limits how long it can remain open after dead centre without becoming too difficult to start.  You will need to flick the flywheel, to start it, but t should run well.

I assume you will make provision to collect the exhaust steam, and not just have the port to atmosphere as per Stanís book.

Looking forward to following your boiler exploits.

Still in lock down here.  Work is acceptable here for those who canít work from home, but people in our age range are advised to stay home apart from a daily walk, which we are making the most of.  We both have hobbies that we are enjoying being able to spend more time on.  I think my wife misses company much more than I, but we both miss the social aspects of family and friends, but managing well and keeping happy.  Technology is a big help but does not entirely replace human contact, and never will.  The different approaches taken by different countries and even different states are interesting and will provide a quite good data set for the next time.

Time in the workshop is filling in the gaps left by other activities that have to be on hold, so busier than ever.  But no point making face masks at this stage as our medical authorities are not recommending them for general use.  Obviously the jury is still out on that one too, and those who analyse this stuff later will eventually work out which way we should all go.  Or will it depend on which combination of other measures are in place?

So going well here.  I hope you are also managing ok in this world that is so different from what it was less than two months ago.

MJM460
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 29, 2020, 10:09:50 AM
MJM - I will look for some information on the Pisces engine as I may be able gain some ideas from it.

Thanks for your explanation on anticipated performance - it's encouraging!

On the exhaust ports - yes, my plan is to collect the exhaust steam and route it to wherever. Stan Bray advises that if his design is scaled up, extra ports should be drilled rather than enlarging the single one in his version, so that's what I'll do. My thought is to make a manifold to gather the exhaust from the ports and direct it into a single pipe. Could look pretty cool too if I make a decent job of it. That feels aeons away at this point though!

The lockdown where I am has been partly eased, i.e. tradesmen who work outdoors are now back at work provided they socially distance. Otherwuse it's still the same - one walk a day, and so on. I live on an island which has managed the situation pretty well and the curve here has been pretty much flattened. They are doing much better here than they are in the UK mainland (where my daughter works as a nurse...), and I think they will ease the lockdown carefully, measuring as they go.

I'm lucky in terms of the work side of things. As a psychotherapist in independent practice my business took a bit of an initial hit, but it has picked up again in virtual form so I'm actually quite busy. My partner is a teacher and she is working from home, setting work for her students online. Not everyone is so fortunate though.

Taking a day off today to spend some time in the shop though!

Great that you are able to do the same. What are you working on?

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 30, 2020, 12:09:32 AM
A bit of progress today in the form of drilling holes in the two flywheels and turning one of the bosses.

The flywheel blanks are just brass discs (albeit quite thick ones) so they need to be fitted with a boss each so that they can be secured to the shaft. I only had a small piece of brass bar in my box so I didn't have the luxury of extra length to hold with the chuck. The solution was to use a 'superglue arbour', which was an idea that I first came across on Clickspring's youtube channel. This was the first time I have tried it and it worked really well. I cut the piece of bar into two with a parting tool and hacksaw to make the blanks for the bosses, cleaned them up and faced them and then drilled and reamed them to make a sliding fit on the shaft. I then found a piece of spare round bar in the scrap box which was slightly oversized for the hole so I turned it down to size and then fixed one of the boss blanks to it with superglue. This made easy work of what what would have been a problematic turning operation:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/859632.jpg)

Once the job was done, a bit of heat from a small blowlamp destroyed the superglue, allowing the workpiece to be removed from the arbour. Prior to this I had drilled a circle of five holes in each of the flywheel blanks. These were marked out on the rotary table with dividing plate and finished on the drill press. I thought I'd try a five hole pattern as it perhaps has a more dynamic feel to it than six does. I may enlarge these holes a bit later on - it depends how it looks when the engine starts to take shape. These will be very minimal flywheels - no recess, etc. The interest will lie in the fact that there will be two of them. Here they are at the end of today along with the boss that I made:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/859633.jpg)

It got quite late so I left the second boss set up with superglue arbour no. 2, ready for turning tomorrow evening. Here is the state of play so far, with the boss trial-fitted to one of the flywheels and mounted on the shaft:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/859634.jpg)

The bosses will be cross-drilled and threaded for grub screws then loctited into the flywheels.

gary





Title: Re: A Simple Uniflow Engine
Post by: MJM460 on April 30, 2020, 01:40:36 AM
Hi Gary, great progress on those flywheels, and it sounds like you have the exhaust arrangements sorted.

The different approaches to lockdown are interesting.  Our outdoor workers have continued through, though there is some grumbling on large construction sites about people not modifying procedures to institute social distancing.  Yet we have not just flattened the curve, but got it right down.  New Zealand had a more severe lockdown, and had a similar result.  I believe Italy and Spain might have much more severe lockdowns and still struggling.  It is becoming clear that ďgo hard, go earlyĒ is the critical component of the strategy, to get it under control before it is established in the community.   Along with lots of testing.  Some countries seem to have low totals, but are not testing anyone, some only count hospital cases, so it is really hard to compare different results.

But one thing that is very clear, the community and the media are both very black and white, with very little understanding of uncertainty and probability, and some understanding of both is critical in this sort of situation.

Glad you and your family are ok, being on an island with early lockdown is a huge advantage.

I am busier than ever with the combination of adapting to new ways of doing everything, which just shows how much energy our brain uses and why we quickly learn to do things on automatic.

Working on two projects, one ready for some tidying up of my notes (and coming soon to a forum near you, and the other just starting, along with iPad brackets for the camera tripod for zoom meetings and similar new requirements.

Keep sheltering keep happy and keep busy,

MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 30, 2020, 01:04:33 PM
Thanks for the encouragement, MJM.

Yes, strict and early lockdown seems to be the winning formula. They were a little bit slow on lockdown on this island but not so slow that they couldn't get on top of it. The mainland UK, on the other hand, have been outrageously slow, and the consequences speak for themselves.

Agreed - coming off auto-pilot is tricky and time-consuming. It would be nice to think that it won't be long before we have to do it again in the reverse direction.

Good to know that you are working on projects. Any chance you could give me a heads up when you post the forum thread?
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 01, 2020, 01:08:16 AM
This evening's efforts:
 
I made the second flywheel boss, and drilled and tapped (M6) the holes for the grub screws that will secure the flywheels to the shaft:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/859744.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/859743.jpg)

The bosses are not a tight fit in the main parts of the flywheels, so I used a generous amount of Loctite 638 to fix them in place:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/859742.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/859741.jpg)

If the rotational force of the flywheels appears likely to weaken the Loctite when in use and shear the bosses from the wheels, I'll have the option of putting a circle of small screws through the flange of each pulley into the wheels to secure them. I suspect that this won't be necessary though.
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on May 01, 2020, 01:53:57 AM
Hi Gary, good progress on those flywheels.

Your engine, by the nature of its valve operation, will tend to have a quite impulsive torque pattern rather than the smoother sine wave of a more conventional valve operation.  That will tend to stress the shear strength of your loctite connection.

And somewhat counter-intuitively, that loctite connection is near the section of the flywheel with the highest shear stress to transmit that torque.

A simple option would be to drill through the flange and wheel as you have suggested, but just insert good fitting pins, just loose enough to leave some room for the loctite, and loctite them in and file or machine flush when the loctite is set.

These pins will transfer the torque in shear, so you will be using the shear strength of the metal pins instead of the shear strength of the loctite, and the loctite only has to stop things falling off.  Easier to do than screws and tapping threads.

I know many people seem to have good experience with using loctite as glue, so it may be enough, but hard to confirm on theory alone.  The strength requires testing, as do so many theoretical issues, and so much will depend on how well you do the loctite joints with clearance, temperature, cleanliness etc.  The pins will be a better solution, and easier to fit than screws.

No problem on the heads up, but I donít have your email address.  I believe there are forum settings that cause the forum to send you notifications, so if you check those, you will get notice in your email.  But it is not far off, so if you remember to notice any little message flags when you check in to do your posts, I will send you a pm.  I donít think you get the message flags though, unless you sign in.  Unless I find your email visible in your profile.  I need to check that again too!

Keep up the good progress.

MJM460
Title: Re: A Simple Uniflow Engine
Post by: steam guy willy on May 01, 2020, 02:18:05 AM
Hi Gary , further to MJM's post I have used Sellick pins with good results...these are sometimes called roll pins and is a sort of sprung type of pin you can get them in lots of small sizes...good work going on here :)

Willy
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 02, 2020, 01:28:39 PM
Hi Both -

Well, I'm not here to ignore good advice. I haven't used Loctite many times but on the occasions that I have I've been amazed by its performance. That may actually have led me to wrongly believe that anything can be achieved with it, even though aesthetically in an ideal world I'd probably prefer not to use glue in engines at all. Rather than wait for things to go wrong and fix them later, I'll go with what you suggest and do a proper job now.

MJM - it is actually quite intuitive to me that the shearing torque will be higher nearer the centre and that the stress on the join between the bosses and the wheels will be high. I remember feeling sick on playground roundabouts as a kid and realising that if you had any chance at all of stopping it by putting your feet down it would be at the outside edge, not in the middle. In the present case, all the more so if the engine is a bit of a jerky runner. Tapping some holes wouldn't be a problem but I think I prefer your pins suggestion so I'll go with that. There would be something phoney about having screws that aren't actually acting as screws, after all. Pins will be more 'honest'.

SGW - I have seen that kind of pin before, when I dismantled an old car engine for fun and to get parts from to use in projects. They are really good and I can see that they would do the job very well. However, as I don't have any of them but do have some thin round silver steel bar, I'll use short lengths of that Loctited in as MJM suggests.

Thanks for your input, both.

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 05, 2020, 11:03:14 PM
I decided to make five holes through the boss and main body of each wheel to correspond with the five 'decorative' holes in the flywheels. To do this I mounted each flywheel in the small 4-jaw on the rotary table in the mill. I just used the setup as a circular vice, eyeballing the positions of the small holes, centre drilling then drilling them, and rotating the wheel by hand each time. I did it this way because I had to drill right through the wheel and If I had rotated the table I'd have fouled the chuck jaws with the drill.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/860613.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/860614.jpg)

The drill I used was chosen to allow an easy push fit of a spare piece of silver steel which I had in the shop:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/860616.jpg)

I cut the pins from the silver steel and then ground them roughly to length - or a little over - on the bench grinder, holding them in this vintage hand vice. I bought this vice in a second-hand emporium in Brighton while visiting my daughter there about a year ago. At the time I wondered if I would ever use it, and indeed I haven't used it a great deal but there are odd occasions like this where I wouldn't be without it:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/860618.jpg)

The pins in their rough form were fixed into the holes using Loctite 638...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/860624.jpg)

... and then the bosses were faced in the lathe:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/860626.jpg)

You will see from this last photo that there is still a lot of work in finishing these flywheels, with machining and chatter marks to face and polish out. However, the pinning operation completes them in their basic form, and overall I'm quite pleased with them. Much of the finishing will be done in situ on the crankshaft.

Meanwhile, I have been in planning mode, ordering some new tooling and making a list of materials that I'll need to continue with building the engine...
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on May 06, 2020, 07:16:30 AM
I'd have just stuck with the loctite unless your fit was really loose, plenty on here have made engines with bigger flywheels loctited together, often on crankshafts that also use loctite to make up the crankshafts or hold a crank disk to the shaft, in both cases the glue area is far smaller and stresses far higher
Title: Re: A Simple Uniflow Engine
Post by: Zephyrin on May 06, 2020, 08:12:37 AM
The annoying thing with these machining marks is that they tend to recur and even amplify on reworking.
you really have to change radically the machining routine, I suggest a very wide tool 10-12 mm and an ultra-slow speed, even turning by hand!

have fun with this new model!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 06, 2020, 08:21:29 AM
@ Jason. I get what you are saying, and the fit was not that loose so I may well have got away with just the Loctite.

When MJM raised the question of pins his point was that pins may be required, not that they definitely would be. I just decided to play it safe and put the pins in so I wouldn't have to go back and do remedial work later if the Loctite failed. As a relative beginner I have never used pins before so it was good experience anyway.

Thanks for your thoughts, which are always worth hearing. Will bear what you say in mind when it comes to the crankshaft.

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 06, 2020, 08:26:14 AM
@ Zephyrin - thank you for this.

I have been using indexable carbide-tippped tools at high speed. The material appears to be quite a hard brass and it rang like a bell.

I'll look out one of my old wide-tipped HSS tools and try what you suggest - it has to be better than hours with sandpaper and scotch-brite!
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on May 06, 2020, 11:09:05 AM
Hi Gary, going well.  So much to learn about getting good surface finish, I will let others advise you on that one

You have done a good job on the pins.  There are always more than one solution to these problems, some are better that others but several will work.  As you say, having done it well will mean you are unlikely to have to do it again.  And itís another technique in your tool box.

MJM460
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on May 06, 2020, 04:22:30 PM
Garry, you might like to try some CCGT inserts rather than the CCMT that it look like you are using. These work very well on non ferrous materials and can take a lighter fine cut. failing that some sharp HSS, largest tool cross section you can fit and minimal overhang.
Title: Re: A Simple Uniflow Engine
Post by: crueby on May 06, 2020, 04:32:28 PM
Is there a good reference chart for all the initials in inserts?
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on May 06, 2020, 04:37:59 PM
I like the one in the MSC catalogue, this is the UK one but expect their US site has similar, you want page 380 & 391

https://edition.pagesuite.com/html5/reader/production/default.aspx?pubname=&pubid=9c3eabd2-e3ba-4a9f-8bd3-aa6475bd6e37
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 06, 2020, 05:19:12 PM
Thanks Jason -

I actually have some of the inserts for non-ferrous metals. They are silver in colour - I suspect they are CCGT but I will check.

It was my intention to us them for the finishing cuts on the wheels anyway, so I will give them a go in the first instance.

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 06, 2020, 10:23:40 PM
Just checked and the other inserts I have are indeed CCGT.

Will load one of them up and try a finishing cut with them on the flyheels.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 11, 2020, 11:11:46 PM
Well, that was easy enough to sort out. A CCGT insert with the lathe running at high speed and slow tool feed brought up a nice finish. Before and after shot below. Still some very minor machining marks - nothing I couldn't live with but I think they will polish out quite easily anyway :

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/861635.jpg)

Now, this engine will be all about symmetry. It will have two flywheels so it will also have two pulleys. I have a thing about flat belts and pulleys (have a million year project of building a lineshaft in my workshop in France...) so I thought I'd allow that obsession some breathing space in miniature here. I ordered some half inch flat belting from PM Research - not very cheap, especially with the shipping cost, but hey... Two pulleys were turned from aluminium on a Superglue arbour. The curved profile between the boss and the main part was formed using a round-tipped carbide tool. Here is one of them in its initial form on the arbour ...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/861636.jpg)

... and here it is having the hole for the locating screw tapped:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/861638.jpg)

Simple stuff, I know, to many of you guys out there, but this serves as a record of my build if nothing else.

The last photo of this session shows a quick mockup of the way that the flywheels and pulleys will be arranged on the crankshaft, bearing in mind (no pun intended) that the second flywheel and pulley will be arranged as the mirror image of this pair, with the crank between the two pulleys. That isn't the crankshaft they are on, btw - it's the Superglue arbour, just for demo purposes.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/861637.jpg)

The pulleys will need to be each given a slight crown for belt tracking purposes. In fact I did so on one of them but then decided to pause on that until a later stage when everything is running true on the crankshaft. I know that in esoteric old tomes there are formulae for the steepness of the crown on flat belt pulleys, but I reckon on something this small a 'suck it and see' approach is the way forward.

Next up is the crankshaft. That will be challenging new territory for me. Exciting though! I'm waiting for materials to arrive, hopefully in the next couple of days...
Title: Re: A Simple Uniflow Engine
Post by: Johnmcc69 on May 11, 2020, 11:32:49 PM
 :ThumbsUp:
 Great work Gary! Nice finish on the flywheel!

 John
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 11, 2020, 11:44:37 PM
Thanks John - very kind of you.

gary
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on May 12, 2020, 07:19:15 AM
Best way to keep the crown even is to set your topslide over a couple of degrees each way and taper the edges leaving the middle 1/3rd untouched then blend with a file. Wider pullies are best done in 5 sections.

(https://img.photobucket.com/albums/v156/jasonballamy/Engineering/EastonandAnderson/IMAG0873.jpg)
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 12, 2020, 09:44:37 AM
Jason -

I had made a start on one of my pulleys, and maybe even finished it (time will tell). I scribed a centre line then a line on either side of that 2mm from the centre line, i.e. leaving an unmachined crown of 4mm, so that would be almost 1/3. I also set the angle of the topslide to what I judged by eye would be about right but the protractor on my lathe is hard to read so I'm not sure what the angle was. The result was a very slight crown on the pulley. Whether it will be enough remains to be seen. If it works I'll be able to repeat the angle because I 'saved'' it on a separate protractor with the angle as yet unread by me but locked in position. That said, I'll check that protractor and if it's less than 2 degrees it will be easy enough to reset the angle and shave a bit more off the pulleys. My aim is to finish the crowns in situ on the crankshaft, at the same time as a final truing up of the flywheels.

Thanks for your interest and advice - much appreciated.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 12, 2020, 10:52:37 PM
The order of materials arrived today. Treasure!

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/861722.jpg)

Given that apart from the basic dimensions and layout of the working parts this engine will be scratch built, I couldn't be too sure about the types and sizes of stock that I will need, so I ordered on the basis of a semi-educated guess while still leaving scope for making things up as I go along. For that reason I won't be too specific at this point about what I think I might use for which parts, except for the 12mm diameter silver steel 4th from the right, which will be the crankshaft.

There are also a couple of other pieces of stock on the way from another supplier, and of course I already have some stock that I will add in as required..

You can be sure that I'll seek your advice when I need to!

I deliberately ordered quite liberally to give me plenty of choices. Some of it I may not use at all, and I hope that following the build I will have quite a lot of this left over for other projects.

Some new gear is on its way - hopefully it will arrive tomorrow. When it does I'll post some photos and then move on to the next stage of the build.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 15, 2020, 12:05:57 AM
More stock arrived today:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/862072.jpg)

Cast iron square bar - a foot each of 50mm and 60mm. Totally over the top for my current requirements, but I would like to use cast iron for a couple of parts of this engine and I couldn't decide which size to buy, so...

There will be plenty left over for future projects. I now have enough square cast iron bar to last me the rest of my life, and that is a good thing. I like to overbuy a bit when ordering materials as a way of building up some stock for inspiration and use in future projects.

This next bit wasn't part of my original plan for the cast iron, but in this excellent little book...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/862070.jpg)

... Alex Weiss says that cast iron is great for bearings if it is running against a hard steel. This is echoed by various sources online, and no doubt some of you will have thoughts about this too. This engine - as I envisage it - will need to have a split big end bearing as it will have a double-webbed crankshaft which will be closed in at both ends by the frame. It occurs to me that it will be a lot easier to make a split plain bearing out of a bit of the square cast bar with the bearing surface being part of the iron itself rather than make one that is similar but with a split bush machined out of bronze and the two halves fixed into the housing. I envisage something like this:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/862071.jpg)

As you will see, sharpies, graph paper and a failure to engage with the conventions of either CAD or engineering drawing are about as hi-tech as I get when it comes to drawing up plans. My sketch is not to scale and the proportions aren't definitive, and that can all be played with as I go along. My question really is whether or not this is a reasonable approach for the bearing in question. The only issue I can foresee is that when the bearing eventually wears, the whole thing will have to be re-done rather than  just replacing a bush, but then it will probably never run for long enough for that to happen anyway. However, you may be able to see issues that I don't, so I'd be grateful for any thoughts you may have before I commit...

Finally - to help me with all this, these arrived today:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/862073.jpg)

Self-explanatory to you guys I am sure. I have had a bit of a splurge, indeed, but these things will help me to up my game.

Getting serious now...

 8)
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on May 15, 2020, 07:23:42 AM
What do you intend to assemble the crankshaft with?

Put an internal fillet on those side projections to reduce possibility of stress fracture and just so it looks nice.

Never a fan of big boxy big ends as there is a lot of unbalanced weight flying around so some shaping would not go amiss

I've only used CI as a bearing in slow speed applications so can't give first hand on running it fast.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 15, 2020, 09:27:25 AM
Jason -

Regarding the speed issue - thanks. I will do a bit more research and of course other forum members may have views too. If I don't hear anything to say that I shouldn't keep the bearing in cast iron, I'll give it a try as worst case scenario it could always be modified later with a bronze bush if it fails.

Great idea about the internal fillet.

Agreed re the boxiness, and good point re the unbalanced weight. The rectangular shape in the sketch is just a starting point really. For example, there is much more cast iron below the split than there is above it, so I'll be reducing the size below the split. Some kind of tapering on the bottom part might look good, and some rounding of the top part too. I reckon on starting with regtangular to the point at which it's functional, then do some shaping to finish.

For the crankshaft I have 12mm silver steel, and was thinking about using rectangular section EN3B for the webs. That said I have some 3/4" square EN1A which could be nice for the webs in terms of the look, though on reflection that might be too narrow. I wonder if you or anyone else have any thoughts about these materials. As it's my first proper crankshaft I'll probably not go for a press fit, so Loctite it will be, possibly with pins (I know you said previously that pins shouldn't be necessary, but this will be a fast runner and I like to know that things are rock solid).

Thanks once again, and have a good day.

 :ThumbsUp:

Title: Re: A Simple Uniflow Engine
Post by: Jasonb on May 15, 2020, 01:24:03 PM
EN£ and silversteel will be fine, as you won't be soldering then you can harden and temper the pin Ok though you could get away with leaving it as supplied.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 15, 2020, 01:32:39 PM
Jason -

by EN£ (possibly a typo) do you mean that EN3B will be fine, or that either of the EN steels I mentioned would be fine?

I did consider silver soldering the crankshaft together. It would be more pleasing to me to do that than to Loctite it. However, my concern would be whether that could risk distorting it with the heat. Do you have any thoughts on that?

Thanks for your interest,

gary
Title: Re: A Simple Uniflow Engine
Post by: Alyn Foundry on May 15, 2020, 01:51:56 PM
Hi Gary.

You don't have to worry about cast Iron bearing to Silver Steel crankshaft....

xnL8h1em45o
My Robinson is 31 years old and has run 1000's of hours. Nary a sign of wear in either of the " mating " surfaces. The engine can run up to 500 RPM too.

I prefer Silver soldered cranks too.... ;)

QwlmaAIzUMU

Cheers Graham.
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on May 15, 2020, 04:24:25 PM
What sort of speed are you hoping for, I got the impression you were after a bit of a goer with flash steam?

EN3B will be fine for the webs. Reason for asking about assembly method is that you can't really have a hardened pin and silver soldered joints as you want the assembled crankshaft to cool slowly which will not harden the pin. For slower speeds you don't really need to think about hardening.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 15, 2020, 04:31:31 PM
Thanks Graham.

What a great-looking engine! That big end bearing looks to be pretty much what I have in mind. Most encouraging...  :ThumbsUp:

In the book I cited earlier, Alex Weiss says:

'Because of its in-built graphite content, cast iron is an excellent bearing material. In use with a steel shaft, the surface of the cast iron gains a tough glazed surface that is very wear-resistant. An additional advantage is that cast iron bearings will continue to operate satisfactorily even in conditions of poor lubrication, though this is no excuse for failing to provide an adequate supply. A relatively unique property of the material is its ability to be used in conjunction with itself. Thus, the cast iron slides of machine tools may rub against cast iron mountings or gib strips of the same material.'

I'm definitely going to give it a go, and am looking forward to machining the bearing. Exciting!

Thanks also for the link to your video of silver soldering a crankshaft. I will definitely not rule that out, and look forward to watching the video - which I will do later this evening. Expect a couple of new comments on your youtube channel...  :)

Out for a walk in the sunshine now, though.

Cheers,

Gary
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 15, 2020, 04:38:25 PM
What sort of speed are you hoping for, I got the impression you were after a bit of a goer with flash steam?

EN3B will be fine for the webs. Reason for asking about assembly method is that you can't really have a hardened pin and silver soldered joints as you want the assembled crankshaft to cool slowly which will not harden the pin. For slower speeds you don't really need to think about hardening.

The speed: tbh Jason I don't really know. I may in due course run the engine on flash steam when eventually I get my flash steam boiler done, but prior to that I may run it on something else. Speed per se isn't the issue for me - I was just attracted to the design, mainly because of its simplicity for a beginner like me. However, I am given to understand that it will prefer higher speeds, so I'll just wait and see what emerges.  :)

EN3B: good to know, thanks.

Thanks for your advice about the crankshaft. Noted. I may yet use silver solder. Graham's video - which I will watch later - may help me make up my mind. I'll either be inspired or intimidated... and probably a bit of both! But nothing ventured, nothing gained...

Cheers,

gary
Title: Re: A Simple Uniflow Engine
Post by: Alyn Foundry on May 16, 2020, 03:20:45 PM
Hi Gary.

Thanks for your comments on my YouTube channel....  ;)

The Robinson replica is 1 1/2" bore and 2" stroke.

The crankshaft is first centre spotted at both ends. If you noticed we started heating the main shaft from both ends, effectively " stretching " the metal evenly. Then you start increasing the heat where the joints are. We apply,  liberally the flux. Having tried many over the years I can totally recommend Tenacity number 5 for this job. Specifically designed for Silver soldering Ferrous materials.

We cut small sections of the Silver solder and put them at each joint. You probably noticed that one dropped away so sometimes you have to manually apply a little more.

Once cold the " bridge " is cut out and the whole assembly put into an Acetic acid bath for 24 hours to remove the flux residue.

Because of the " spotting " you can now " true up " any discrepancies in the lathe.

Just for fun....

37u1WruBMgU
Cheers Graham.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 17, 2020, 09:54:48 AM
Graham -

Many thanks for your detailed description of how to silver solder the crankshaft.

I'll give some thought to the question of siver soldering mine vs using Loctite.

As you don't mention pins, I presume you don't use any.

That Robinson is a beauty!

Cheers,

Gary
Title: Re: A Simple Uniflow Engine
Post by: Alyn Foundry on May 17, 2020, 11:37:10 AM
Graham -

As you don't mention pins, I presume you don't use any.

That Robinson is a beauty!

Cheers,

Gary

No pins Gary.    :)
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 17, 2020, 12:47:04 PM
Cheers Graham.

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on May 17, 2020, 01:09:37 PM
And just when you thought you had decided what way to do it someone comes along and says they use pins as they like to apply the solder to one side of the joint only it makes it a bit hard to tell how deeply it has flowed.

http://www.modelenginemaker.com/index.php/topic,2160.msg39156.html#msg39156
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 17, 2020, 01:29:35 PM
Right! That's it! I'm going back to stamp collecting...  >:(


Thanks Jason. Great post and pictures, which will be an excellent resource for me if I decide to use silver solder.

Your Galloway thread as a whole will be worth reading, I have no doubt. I have kept the tab open for later... :popcorn:

Hope you are having a good weekend.

gary

 :ThumbsUp:

Title: Re: A Simple Uniflow Engine
Post by: MJM460 on May 17, 2020, 01:54:41 PM
Hi Gary, while you are thinking about silver soldering, I will make a few comments on the overall project.

It is important to separate the ideas of flash steam and high speed engines.  Of course, the two are often associated in a project, and for quite valid reasons, but it is not necessarily so.

A flash steam boiler, sometimes called a mono tube boiler, is a boiler configuration that provides a quite  large heat transfer area for steam raising, with quite low weight for the steam production achieved.  But at the end of the day, the amount of steam raised is determined mostly by the burner, and how much fuel can be burned, so long as you have enough heat transfer area.  I was tempted to include the word efficiently in that sentence, but not all projects are interested in efficiency.  If someone wants to break a record, they want maximum power, and if burning more fuel, even less efficiently, achieves more power, then they go for it.

Part of the low weight is achieved at the expense of water capacity.  There is effectively no water storage in a flash boiler, so they canít be operated like my little boilers by filling up with water then lighting the burner and start steam production.  Well perhaps they could, but it would be a quite short run.  They really need a feed pump, preferably driven by the engine, but again it is not the only way.  The preference is because both steam consumption and water requirement, the same thing really, are dependent on engine speed, so while it is still not easy to balance the two, it is easier than if a separate pump is used.

Of course, the high power to weight ratio is very desirable for high speed vehicles, whether land based or water, and when combined with a very big burner, can produce awesome power to drive the engine.

But it does not have to be so.  If you use a quite moderate burner then you produce only the proportionate amount of steam.  You could build a quite moderate steam plant for a model boat for very sedate performance.  This approach has its own chapter in Benson and Raymanís excellent book, even though the rest of the book is a fascinating look into the world of high speed hydroplanes.  I think I remember you buying it, so you will be aware of the valuable information there.

In addition, it is not necessary for there to be no water storage.  A moderate plant can include a pressurised water tank, with an air cushion over the water, between the water pump and the steam coil.  It will smooth out the flow and give a bit of a safety factor against water failures, which might allow you to bring a model back to extinguish the burner.  A separate tank like this can allow design of the plant with a much lower centre of gravity than a more conventional boiler design, which is good for stability of a model boat.  Of course the fire tube marine boiler also has a good low centre of gravity.

The engine is a quite separate issue.  An oscillating engine as you have already built can operate quite slowly when required, particularly a twin cylinder double acting design which does not have the dead spots that the flywheel must supply the energy to carry through.  Similarly a slide valve engine, or any of the other designs we usually see on this site.  The upper speeds are mostly limited by the quality of balancing achieved, not easy with heavy reciprocating parts.  My mill engine achieves around 2000 rpm unloaded with quite low steam pressure, with limited balancing, but I suspect that even at this speed, wear might become an issue if I pushed it that fast for long.  So hardened pins and more attention to bearings might be required.

Slow engines are generally characterised by long stroke compared with the bore, though not necessarily so.  More significantly the steam is admitted mostly after the top dead centre, even when a little is admitted before.  Your engine with the inlet valve operated by a peg on top of the cylinder has the steam admitted equally each side of top dead centre. (I wonder how a double acting engine would be implemented).  More likely a twin single acting, or better still a three or more cylinder configuration with the cranks spaced equally around the shaft.  Because of this necessarily early admission, the engine needs to get enough of a kick every steam admission to accelerate the flywheel to store the energy necessary to push the piston over the next top dead centre position.  Otherwise the engine might just oscillate back and forth through about 340 - 350 degrees.  The engine will be happier going faster for this reason, but it still does not require the extreme speed sought by the racing community, it just wonít run slowly like your little oscillator.  But a quite interesting design, well worth trying.

So while roaring blowlamps, extreme pressure and temperature steam conditions, and high speed racing hydroplanes, are typically based of a flash boiler, uniflow engines, and very highly developed material selection, and manufacturing techniques, there is no reason why you cannot run your simple flash plant with a more moderate burner and your current engine, which might run quite happily around 1500 - 2500 rpm (at a wild guess) but definitely not slow like your oscillator.  Mind you, an oscillator is also is no slouch if you give it enough steam, as the oscillating engine design involves a much smaller oscillating mass than a typical mill engine, in both reciprocating and rotary motions.  Mine go at 2000 rpm measured with a digital tacho when unrestrained and with only the little meths burner, and are really not fussed at this speed.  Much less vibration than the mill engine.

It is one of those things that has to be tried, but if you can tackle a little engine driven pump, perhaps with bought gears, there is no reason that you could not try your flash plant with this new engine.  Keep the burner relatively gentle until you get the feel of it.  But I really would not recommend the flash plant with a hand pump only, unless you have plenty of water capacity.  It all comes back to heat balance.

By the way, stamp collecting is only allowed during the current lockdown situation, and there is another current thread where that can be included.  In the mean time you have an an engine and flash boiler to complete!

MJM460

Title: Re: A Simple Uniflow Engine
Post by: Jasonb on May 17, 2020, 02:27:04 PM
But I bet Garry has his heart set on a flash steam setup like this :LittleDevil:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/44290/860506.jpg)

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 17, 2020, 04:43:47 PM
I do  indeed, Jason.

But I also have my heart set on far too many other things. Funnily enough, stamp collecting hasn't featured among these for more decades than I care to remember. And flower pressing has never been on my list.

But yes - I would love to build a kickass flash steam plant. Equally, I would like to build a big, slow, lazy mill engine. And a beam engine. Maybe with a bit of a contemporary feel to the styling. And perhaps one or two bigger boilers.That's already quite a list alongside a bunch of other, non-steam related pipedreams.

But right now my heart is set on some ice cold cider and some burning BBQ charcoal, so to do MJM's post justice I shall read and respond to it later.

Cheers Guys, and thanks for your support.

 :cheers:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 18, 2020, 10:06:54 AM
Hi Gary, while you are thinking about silver soldering, I will make a few comments on the overall project.

It is important to separate the ideas of flash steam and high speed engines.  Of course, the two are often associated in a project, and for quite valid reasons, but it is not necessarily so.

A flash steam boiler, sometimes called a mono tube boiler, is a boiler configuration that provides a quite  large heat transfer area for steam raising, with quite low weight for the steam production achieved.  But at the end of the day, the amount of steam raised is determined mostly by the burner, and how much fuel can be burned, so long as you have enough heat transfer area.  I was tempted to include the word efficiently in that sentence, but not all projects are interested in efficiency.  If someone wants to break a record, they want maximum power, and if burning more fuel, even less efficiently, achieves more power, then they go for it.

Part of the low weight is achieved at the expense of water capacity.  There is effectively no water storage in a flash boiler, so they canít be operated like my little boilers by filling up with water then lighting the burner and start steam production.  Well perhaps they could, but it would be a quite short run.  They really need a feed pump, preferably driven by the engine, but again it is not the only way.  The preference is because both steam consumption and water requirement, the same thing really, are dependent on engine speed, so while it is still not easy to balance the two, it is easier than if a separate pump is used.

Of course, the high power to weight ratio is very desirable for high speed vehicles, whether land based or water, and when combined with a very big burner, can produce awesome power to drive the engine.

But it does not have to be so.  If you use a quite moderate burner then you produce only the proportionate amount of steam.  You could build a quite moderate steam plant for a model boat for very sedate performance.  This approach has its own chapter in Benson and Raymanís excellent book, even though the rest of the book is a fascinating look into the world of high speed hydroplanes.  I think I remember you buying it, so you will be aware of the valuable information there.

In addition, it is not necessary for there to be no water storage.  A moderate plant can include a pressurised water tank, with an air cushion over the water, between the water pump and the steam coil.  It will smooth out the flow and give a bit of a safety factor against water failures, which might allow you to bring a model back to extinguish the burner.  A separate tank like this can allow design of the plant with a much lower centre of gravity than a more conventional boiler design, which is good for stability of a model boat.  Of course the fire tube marine boiler also has a good low centre of gravity.

The engine is a quite separate issue.  An oscillating engine as you have already built can operate quite slowly when required, particularly a twin cylinder double acting design which does not have the dead spots that the flywheel must supply the energy to carry through.  Similarly a slide valve engine, or any of the other designs we usually see on this site.  The upper speeds are mostly limited by the quality of balancing achieved, not easy with heavy reciprocating parts.  My mill engine achieves around 2000 rpm unloaded with quite low steam pressure, with limited balancing, but I suspect that even at this speed, wear might become an issue if I pushed it that fast for long.  So hardened pins and more attention to bearings might be required.

Slow engines are generally characterised by long stroke compared with the bore, though not necessarily so.  More significantly the steam is admitted mostly after the top dead centre, even when a little is admitted before.  Your engine with the inlet valve operated by a peg on top of the cylinder has the steam admitted equally each side of top dead centre. (I wonder how a double acting engine would be implemented).  More likely a twin single acting, or better still a three or more cylinder configuration with the cranks spaced equally around the shaft.  Because of this necessarily early admission, the engine needs to get enough of a kick every steam admission to accelerate the flywheel to store the energy necessary to push the piston over the next top dead centre position.  Otherwise the engine might just oscillate back and forth through about 340 - 350 degrees.  The engine will be happier going faster for this reason, but it still does not require the extreme speed sought by the racing community, it just wonít run slowly like your little oscillator.  But a quite interesting design, well worth trying.

So while roaring blowlamps, extreme pressure and temperature steam conditions, and high speed racing hydroplanes, are typically based of a flash boiler, uniflow engines, and very highly developed material selection, and manufacturing techniques, there is no reason why you cannot run your simple flash plant with a more moderate burner and your current engine, which might run quite happily around 1500 - 2500 rpm (at a wild guess) but definitely not slow like your oscillator.  Mind you, an oscillator is also is no slouch if you give it enough steam, as the oscillating engine design involves a much smaller oscillating mass than a typical mill engine, in both reciprocating and rotary motions.  Mine go at 2000 rpm measured with a digital tacho when unrestrained and with only the little meths burner, and are really not fussed at this speed.  Much less vibration than the mill engine.

It is one of those things that has to be tried, but if you can tackle a little engine driven pump, perhaps with bought gears, there is no reason that you could not try your flash plant with this new engine.  Keep the burner relatively gentle until you get the feel of it.  But I really would not recommend the flash plant with a hand pump only, unless you have plenty of water capacity.  It all comes back to heat balance.

By the way, stamp collecting is only allowed during the current lockdown situation, and there is another current thread where that can be included.  In the mean time you have an an engine and flash boiler to complete!

MJM460


Thank you for this, MJM.

Although I was aware that the uniflow engine could be appropriately paired with a flash boiler (and have indeed considered that option), I didn't choose to build this engine with that specifically in mind. Another - quite separate - boiler development is on the cards. More of that later.  ;) 
However, irrespective of that, it would make sense for me to try running the engine on the flash boiler once they are both complete, but with the following caveats:

First - I may be wrong, but I have a feeling that the engine may require a bigger coil in the flash boiler than the current one as the cylinder bore will be either 30 or 35 mm. Fairly chunky. That said, I understand that coils are considered to be a consumable, and it wouldn't cost much in terms of time or money to twist up a bigger one.

Secondly (and this is a somewhat bigger issue) - I have gathered from the literature that a displacement lubricator won't work with flash steam as superheated steam is too hot to condense within the lubricator and will go straight through to work its mischief on an unlubricated piston and cylinder.  The thing is that I'm not really sure that I want to put my energy into building a mechanical lubricator, at least at this point. One could then legitimately ask why I decided to start building a flash steam boiler if  this is the case. The answer would be that the flash boiler is really a kind of side project for me, something that is motivated more by in-the-moment curiosity than by a clear sense of purpose, built as cheaply as possible and to fill gaps between other projects over a longer period of time. One of those, you know...

I have no plans to build model boats or vehicles - it's stationary engines and boilers that most interest me (though to build an engine that would drive a real small boat would be exciting!). However, I do like the idea of using the pressurized reservoir with air cushion, as mentioned by you  above and as we discussed at the start of my flash boiler thread. That said, unless there is a way round the oil pump vs displacement lubricator issue (and if anyone knows of such it will be yourself!) then the likelihood is that I won't be running anything on flash steam any time soon and that another boiler will be used to drive the uniflow engine on non-superheated steam in the first instance.

I suppose I could always hire out the flash boiler (in its semi-complete state) to philatelists looking for more efficient ways of steaming stamps off envelopes. Or if not more efficient, certainly more powerful ... :Lol:

Thanks as always for your very knowledgeable input.

gary

Title: Re: A Simple Uniflow Engine
Post by: MJM460 on May 20, 2020, 10:12:13 AM
Hi Gary, I would not want to discourage you from your intended course, and I look forward to seeing the new boiler develop.  These are after all, affairs of the heart, and no one else can dictate where we should go. 

However, in the interests of increasing understanding, I hope you will bear with me while I explore some of the issues in your caveats.

The first one introduces a whole bagful of interesting issues.

First, how much steam will your uniflow engine actually need?  The valve principle is actually very different from oscillating or slide valve engines we all normally think about.  The valve is only open for the short time the piston crown is touching that peg which protrudes into the cylinder.  And there is a whole chain of dimensions determining that time, each with its own tolerance, which can accumulate to make the actual time difficult to determine, however, that is not the aspect I mean.

When the usual valve first opens there is an initial inrush of steam to equalise the pressures, then the continuing downward travel of the piston under the influence of the steam pressure, does the work that turns the engine.  But consider the uniflow!  When the valve opens, the piston is travelling up!  Still might be that initial inrush, or might not if the steam remaining in the cylinder after the exhaust closes off is compressed up to pressure by the time the inlet valve opens, but then the engine does work on the steam (it comes from the flywheel slowing) for fully half the time the valve is open.  Think of that for a moment, for fully half the valve opening time, the volume in the cylinder is reducing and only the pressure balances with that in the boiler.  Then steam enters through the now fully open valve and while the pistons goes down until the valve closes, I assume at about 1/4 of the stroke, quite early cut off for any engine, and then takes advantage of the expansion of the steam in the rest of the stroke until the exhaust opening lets enough steam out to lower the pressure again for the return stroke.  Because this engine really does utilise the steam expansion, so I expect it will be quite miserly in its steam consumption.  It is that requirement for the flywheel to do the work before top dead centre that is why the engine will probably need to run faster than typical on this site.  The flywheel needs plenty of stored energy for the non-power parts of the cycle.  Similarly you might need a bit higher steam pressure than is required to run your oscillator.

The next issue is how much coil length to generate the required amount of steam?  Again, first it is important to recognise that the steam produced by a boiler is fundamentally determined by the heat released by the burner.  The efficiency of the boiler is a secondary, but still important consideration.  That efficiency is again determined primarily by the heat transfer area, with other arrangement factors secondary.  My little boilers seem to run at around 60 to 70% for example.  The amount lost goes mostly up the stack in the heat of the flue gas, and is unavoidable.  A much smaller amount is lost from the casing, and this can be minimised by insulation.  There is a lot of variation in the acceptable heat transfer area, but if you calculate it for your vertical boiler, it will give you an idea.  If your coils has less heat transfer area, more heat will be lost up the chimney in the form of higher flue gas temperature, but if more area, then less loss, but it is diminishing returns.  As the steam gets hotter so the temperature difference from the flue gas gets less, you need increasingly more area to get the next little bit of improvement.

As for the coil being disposable, I think that is probably more in the context of those extreme hydroplanes, where they melt copper tubing so have to go to stainless steel, and quite likely push the limits of that.  A more moderate firing rate should allow copper to last as well as your vertical boiler.  But you are also right in assessing that a new coil costs a lot less in material and effort than a conventional boiler, and that is part of the attraction of the concept for moderate applications, while the light weight relative to the steam produced is a major factor for chasing speed.  If you put a little meths burner under your coil, it will not melt the copper, and the displacement lubricator will work just as on my pot boiler.  There is a lot of space between those extremes.

So quite a lot in that first caveat

The second point, about lubrication, is also important and has to be taken into account also for air running if long running hours are required.  It is true that if the displacement lubricator gets too hot, the steam does not condense, and no oil is displaced into the steam pipe.  However, while the jump to an oil pump is necessary for the chasers of extreme, and I am told that the little oil pumps are not very difficult, though I have not yet tried one, there are also a few tricks you can do with a displacement lubricator in a moderate plant if the degree of superheat prevents the lubricator from working.  If you use a steel washer in the connection between the lubricator and the steam pipe, it conducts a little less heat than brass in contact.  And a fibre washer even better.  You can also add some cooling fins to the lubricator body to increase the heat loss.  These require a bit of trial and error with only short runs until you are getting an amount of water accumulating in the lubricator.  Certainly we overlook lubrication at our peril, and as the burner gets bigger, the pump solution becomes preferred.

Regarding your last comments, who among us has not at some time felt ďso many projects, so little timeĒ, and those high speed hydroplanes look like wild beasts.  But I suspect we both need to learn a lot more about more moderate plants before we chase that dream too far.  But one day.....

So donít let me deflect your plans, but it is always useful to have a few more ideas in the tool box for the day they might come in handy, they arenít very heavy.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 21, 2020, 12:30:54 AM
MJM -

Indeed, ideas are not too heavy to carry around. What you have said about ways to make a displacement lubricator work with a monotube boiler (I won't use the term 'flash' here because I understand that the coil can deliver steam at lower temperature) is encouraging, and I will plooter away with the flash/monotube boiler over time alongside other developments. I have no major objection to the idea of building an oil pump other than time and how I want to spend it, but it's nice to know that there are other options too. I had a feeling you would come up with something!

If I understand you correctly, it would seem that the uniflow engine may not demand much steam but that the steam it does use will need to be at high pressure. How that would translate into performance on the coil I have already made will be (for me at least) a matter of trial and error. I take your point about these coils only being a consumable when pushed to the extreme - that makes sense. However, if I found that I needed a bigger coil it wouldn't be a big job to make one. Which I suppose could in turn require a more powerful lamp... we shall see.

All this said, another boiler solution is waiting in the wings. It may seem unnecessarily coy but I'd rather not explain until it's a reality. It will certainly make a difference to he options for running this and other engines though.  Which doesn't mean that the flash boiler will be cast aside unfinished, but it does mean that I'll be able to take my time with it.

 :)
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 21, 2020, 01:02:00 AM
Started work on the two main bearings between the crankshaft and the sides of the frame. Still very much a beginner but now learning to up my game by using my new 4-jaw independent chuck clocked with a DTI to minimise runout instead of the 3-jaw and crossed fingers:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/863202.jpg)

Hopefully this will result in a better engine at the end of the day.

I have also just accquired two of these for parting off - one 2mm and one 3mm:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/863203.jpg)

The 2mm tool sliced through the bronze with very little effort and minimal anxiety on my part! Very nice to use, but counterintuitive how that insert stays in place I reckon.

gary

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 04, 2020, 12:33:21 AM
Unfortunately I had a dig-in and mangled the first of the two main bearings, so I put the stock for the bearings aside and ordered some tooling to make the job easier. I switched my attention to making two bronze collars (yay! for ER-32 collet blocks!) ...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/865622.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/865623.jpg)

... and two cast iron thrust collars:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/865624.jpg)

Here they are, temorarily rigged up on the crankshaft-to-be for demo purposes:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/865625.jpg)

Outboard of each flywheel the cast iron thrust collar will run against the bronze face of the main bearing. The bronze collars are situated between the pulleys and the crank webs, mainly just for the look. I somehow managed to screw up the crank webs by making holes that are out of parallel, so the ones you can see in the picture are destined for the scrap bin and new ones will be made.

Pausing there while waiting for more steel, I began work on the cylinder, which will be of cast iron. I started by squaring a block of the stuff with a facemill and a large endmill:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/865626.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/865627.jpg)

The cylinder block was then chucked in my new self-centring 4-jaw and clocked in as closely as I could get it (with the aid of a rubber mallet):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/865628.jpg)

This was my first ever experience with a self-centring 4-jaw and I was impressed by how solidly it holds a square workiece.

The cylinder bore was then started with a centre drill and a succession of twist drills...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/865629.jpg)

... and then bored to size (35 mm):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/865630.jpg)

It remains chucked in the lathe as I type. The bore still needs a finishing cut, after which it will be honed. The outside of the block will be given some profiling and the surface finish will need more work.

All in all, some progress, despite a couple of frustrations...

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 08, 2020, 10:06:37 PM
The basic bore of the cylinder is now complete. 35 mm (approximately):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/866414.jpg)

The picture below shows the bore, with the cylinder silhouetted against the evening sky. There are obvious machining marks. I don't know what you guys will think, but I feel quite pleased with the internal finish given that I used a toolpost-mounted boring bar, albeit a fairly rigid one. The marks are not deep and the pattern is regular. I have ordered a cylinder hone and some honing oil and I'm hoping that will take care of the internal surface:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/866413.jpg)

I'm hoping that the hone arrives tomorrow. The external surface of the block needs more work.

So, in the absence of a hone, I then started on the cylinder end cap. This will also be square-ish in form and will be bolted to the cylinder but will be visually continuous with it. It will be bolted in situ when I profile the outside of the cylinder block so that the two parts can be milled to shape simultaneously. The cap will have a raised boss on the inside to locate it in the end of the cylinder. It will be drilled and tapped in the centre to accept the steam inlet valve. In this photo I have made a start on turning it down but I thought I'd better stop for the night as the neighbour's kids are probably trying to sleep.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/866412.jpg)

I enjoy machining cast iron but it's a messy old game. Major cleanup required...

Cheers,

gary
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 16, 2020, 12:16:49 AM
While waiting for the cylinder hone, I made a start on making some new crank webs. The ones I made before were no good as the holes were out of parallel. I will have to find out where the origin of that problem lies. Meanwhile, though, I have decided to try making a new pair on the mill. I used superglue to fix two pieces of the steel bar together so that they can both be drilled and reamed at the same time:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/867313.jpg)

In the picture it looks like they are not fixed together, but they are. The effect is just because the ends hadn't been squared off when I took the photo. Both ends of the temporary assembly have now been milled square ready for drilling and reaming in the mill. Once that is done I'll use heat to break the superglue bond.

However, these arrived today...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/867312.jpg)

... so it's back to the cylinder. I have never set eyes on this type of hone before, and the stones on the hone are much smaller than I thought they would be, but no problem. I made a start with the honing, the hone being held in a hand drill and the cylinder in the vice:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/867311.jpg)

The bore is coming up with a nice satin finish, but some machining marks are still visible and there is a bit of surface unevenness about halfway down the bore that I can actually feel with my fingertip, albeit slightly. I don't know how much of an issue this is as I'm hoping it will hone out, but I decided to pause with the honing and make a dummy piston out of a piece of scrap brass to test the overall straightness and regularity of the bore. There's no point in further obsessing with the hone until I have checked that the bore is basically true and parallel, and I think the dummy piston will be a good way to gauge that.

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 16, 2020, 10:18:59 PM
The next step was to finish the basic form of the cap. It has a spigot which fits the bore fairly snugly. The cap will be bolted to the end of the cylinder and the edges will be milled in situ to create visual continuity between the cylinder block and cap:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/867401.jpg)

In his design, Stan Bray suggests a shop made ball-bearing type check valve as the main steam inlet valve to the cylinder.  I'm not such a purist that I feel compelled to make fittings of this kind when they can be bought from a supplier. I'm using a ready-made check valve sized for 1/4" OD pipe. The cap will be drilled and tapped for this valve, but the photo below shows a mockup of the arrangement just to give an idea:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/867404.jpg)

It was then time to test the cylinder. I turned down a piece of brass on a superglue arbour (yay, Clickspring!) to make a dummy piston:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/867403.jpg)

Then, with my heart in my mouth I anointed it with steam oil and pushed it into the bore:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/867402.jpg)

Amazing! My fears of a crooked bore and jamming were unfounded. The dummy piston behaved in the cylinder just like a real piston should. Smooth action (well, just a couple of very minor tight spots but these will disappear). When I put my hand over the open end where the cap will be, the piston pulled a formidable vaccuum.  :cartwheel:

Well pleased with that and tbh I don't feel inclined to obssess much more about the finish of the bore. Once I have drilled the steam exhaust ports I'll give the bore another quick go with the hone and try to achieve the desired cross-hatch pattern, but I'm pretty sure the thing would run fine as it is. In fact I think  that the real piston can afford to be a tiny bit bigger in diameter for even better performance.

The exterior of the cylinder requires more work, mainly of a cosmetic nature. More of that later...

Now, a question: can any of you advise me on my choice of material for the piston? I have round bar of sufficient diameter in cast iron and free machining stainless . I'd be happy to buy something else if needs be, but I suspect I don't need to. I'm aware that cast iron is an exception to the rule about using dissimilar metals together, and I also understand that stainless works fine with cast iron too. Which would you guys recommend?

Also, I'll be quite happy not to use ring(s) of any kind on the piston, though wouldn't mind cutting an oil groove or two in it. However, I'm happy to change my mind in response to advice. Any thoughts?

gary
Title: Re: A Simple Uniflow Engine
Post by: john mills on June 17, 2020, 12:07:21 AM
you have a cast-iron cylinder then the material to use is cast iron .
Title: Re: A Simple Uniflow Engine
Post by: Johnmcc69 on June 17, 2020, 01:34:21 AM
you have a cast-iron cylinder then the material to use is cast iron .
But wouldn't SS be better for corrosion resistance?

 My edit: Nice work Gary!

 John
Title: Re: A Simple Uniflow Engine
Post by: john mills on June 17, 2020, 06:51:35 AM
the cylinder is already cast iron so the same care for the cylinder already if you don't want corrosion then cylinder out of bronze  piston bronze too soft packing will serve well .with cast iron then cast iron piston rings rusting is can be a problem.   
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 17, 2020, 10:45:48 PM
Thank you both.

I think I'll probably go with a cast iron piston. As john mills notes the cylinder is cast iron so it will be vulnerable to corrosion anyway. I'll just have to keep it dry and oiled when not in use.

I'd rather get away without piston rings if possible. Would just having a plain cast iron piston with maybe oil grooves but no rings be viable or would the absence of rings have a very detrimental effect? If any rings are necessary I'd prefer to go with silicone or viton ones (whichever it is), but would prefer not to use them if possible. I'd welcome any further thoughts on this. The cylinder bore is about 36 mm.

Meanwhile, this evening - a fair bit of thinking done but only modest progress in practical terms. I drilled two exhaust ports through the cylinder walls into the bore, then gave the bore a light honing to remove any burrs, after which I marked out (by hand) and punched for a bolt circle to which the cap will be fixed in due course:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/867600.jpg)

 This is a x 3.5 scale-up from Stan Bray's plans, but his small original version has one exhaust port of the same size as these. His advice is to keep the same size of exhaust port in scaled up versions but to make more of them, so I stuck to his original size but drilled two of them, one on each side of the cylinder. If these turn out to be insufficient I can always drill a third one on the top of the cylinder. The idea is to eventually make a manifold of some kind to connect the exhaust ports together.

Regarding the bolt circle, the bottom right punch mark in the photo is a bit out of alignment. I fixed that after the photo was taken.
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on June 18, 2020, 07:10:14 AM
If you are not going to put the engine to much work then you can run it without rings, easy enough to enlarge one of the oil grooves for a Viton ring if you find you want one at a later date.

Not enlarging the holes is probably more to do with timing so you could put them side by side which may help reduce the number of pipes to couple them up
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 18, 2020, 08:32:36 AM
Great idea on the viton ring, Jason. Thanks. Not sure how much work it will do, but I'd like it to do some I think. One step at a time as you suggest sounds sensible.

I have already drilled the exhaust holes on opposite sides of the cylinder with the possibility of a third one on top. I'm ok with that though as I have a half-formed picture in my mind of a funky-looking manifold that could be quite a visual feature if I get it right.

Any advice from anyone on depth, width, number, spacing and profile of oil grooves in the piston would be welcome.
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on June 18, 2020, 10:06:00 AM
I usually do 3 @ about 0.5mm deep equally spaced along the piston
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 18, 2020, 10:07:14 AM
Ok ta.

Maybe with a parting off tool?
Title: Re: A Simple Uniflow Engine
Post by: john mills on June 18, 2020, 10:46:28 AM
hi Gary

i would make the grooves a little deeper ,they will work to reduce leakage and the engine will run.I have an engine running with a larger bore has been running with out rings just the grooves and it runs 0k.you can always try running and add rings latter  .    I would use a grooving tool you have that will let you fit number of grooves across the piston if it is a parting tool that would do.
             John
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on June 18, 2020, 11:15:08 AM
Hi Gary, another vote for no rings, just plain grooves.  I have done this on each of my engines and they all run quite well.

In large compressors, there is one at least one brand of oil free reciprocating compressors which has no rings even for high pressure hydrogen.  They have a series of square grooves with no rings or packing.  Admittedly more rings than you would want, but the principle is called a labyrinth compressor.

Basically, the gas or steam passing between the piston and cylinder reaches a groove, it expands into the groove, with a consequent pressure loss.  It then has to accelerate into the passage again.  So generally more resistance, and consequently less bypass than a plain piston.

I tend to use about 1.5 mm wide and deep, as I have a suitable tool for those.  And two or three depending on the length of your piston and what will fit.  Whether it is really the labyrinth effect, or the effect on the oil film, or even if a plain piston would be just as good, I donít really know.  It would probably be necessary to rig up some sort of flow test, but it would need quite accurate instrumentation.

I always have it in mind to add some graphiteís yarn some time to see if this makes a difference, but my observation so far is that the engines run well without it. 

The same principle where the piston rod passes through the gland, though there, I generally return and add theming of graphited yarn, which definitely reduces the leakage.  Just the annulus between the piston and cylinder has a larger cross sectional area for flow than the gap around the piston rod.

With your nicely fitting piston, I would just cut the grooves and not worry further.

MJM460
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on June 18, 2020, 01:20:06 PM
For smaller engines I use vee grooves, same as found on thousands of Stuart 10 series engines so proven to work.


Most of the 24mm ones I have been designing over the last few years have a single O ring groove cut but have not found the need to fit the actual rings ( do on the IC engines)
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 18, 2020, 09:14:20 PM
Thank you guys - that gives me plenty to go on.

 :ThumbsUp: :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 28, 2020, 09:39:18 PM
Meanwhile, still on the cylinder.

Eight holes for the bolt circle were drilled and tapped M5, and transfer screws were used to mark out their positions on the inside of the cap:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/869030.jpg)

The edges of the cap were milled to size in situ on the cylinder body:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/869029.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/869028.jpg)

I think (hope!) that the cylinder would be functional in its present state with the addition of the valve, but there is still a fair bit of work of a cosmetic nature to be done on the outside of the cylinder block.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 29, 2020, 11:37:45 PM
A corner-rounding endmill was used to...er... round the corners:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/869192.jpg)

Sorry about the grainy picture quality there.

This was done with the cap in situ. Some sanding was then carried out using 180 grit wet and dry paper with cutting oil on the surface plate. This made a difference quite quickly:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/869191.jpg)

There is stilll more sanding to go to achieve the finish I want.

Now, once again, I seek your advice. I do not wish to paint this engine. How realistic is it to leave the cylinder  (cast iron as it is) untreated and just given an occasional light smear of oil to keep it from rusting? If that's not a good idea, I wouldn't mind blackening it with the chemical product called 'Black-it', though that's quite an expensive option. Do any of you know of any other ways to treat cast iron? I would be happy to hear of anything innovative to give it an interesting surface patina or colour...
Title: Re: A Simple Uniflow Engine
Post by: Admiral_dk on June 30, 2020, 11:49:04 AM
You are doing good so far  :ThumbsUp:

Have a look at how Chris Nickle plate iron - simple and without any problematic chemicals.

Best wishes

Per
Title: Re: A Simple Uniflow Engine
Post by: crueby on June 30, 2020, 02:53:07 PM
I have electroplated nickel onto steel, never tried it on cast iron, seems like that would work too. It would not give the black color you want, though.
Title: Re: A Simple Uniflow Engine
Post by: Johnmcc69 on June 30, 2020, 08:49:43 PM
Over at the "other place" (HMEM)  :paranoia: there is a fellow building G. Britnell 's beautiful Holt model. He has been using some gun bluing solutions from "Brownells" with some really stunning results....
 Not sure how those solutions work with CI, or cost, but it adds an aged patina that looks great on that engine.

 Additionally, bead/sand blasting adds a nice "as cast" appearance.

 Nice work on that cylinder Gary!

 John
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 30, 2020, 10:50:03 PM
Many thanks Gentlemen.

@Chris - would you mind telling me which thread of your prolific output contains the nickel plating? I'm not necessarily seeking a black finish.

@John - beadblasting... now that has some appeal, for sure.

Will think about the options...

gary

 :ThumbsUp: :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: crueby on June 30, 2020, 11:12:04 PM
It was over on the Marion Valve Engine build thread, here:
Started here, with link to the instructions I followed:
https://www.instructables.com/id/High-Quality-and-safe-Nickel-Plating/
http://www.modelenginemaker.com/index.php/topic,9312.msg210244.html#msg210244 (http://www.modelenginemaker.com/index.php/topic,9312.msg210244.html#msg210244)
More a few posts after that one, and here too
http://www.modelenginemaker.com/index.php/topic,9312.msg210244.html#msg210244
Its quite easy to do, I recommend getting a variable power supply if possible so you can adjust the voltage - higher is quicker, but rougher finish, around 6 volts is good. The distance to the part changes it too, the closer the faster/rougher. Distilled water, non-iodized salt, a Nickel rod/plate for a source, and a plastic container are the only other parts you need. No nasty acids involved, and you can re-use the solution so a lidded container is handy to store it in. I've since done a bunchof knobs for the Lombards up at the museum, as well as parts for several models. After plating, you can buff the plating to shine it up.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 30, 2020, 11:22:45 PM
Over at the "other place" (HMEM)  :paranoia: there is a fellow building G. Britnell 's beautiful Holt model. He has been using some gun bluing solutions from "Brownells" with some really stunning results....
 Not sure how those solutions work with CI, or cost, but it adds an aged patina that looks great on that engine.

 John

John - I had a look and I think I found it - about half way down this page (by Mark T, or 'dnalot'):

https://www.homemodelenginemachinist.com/threads/marks-holt-75.31650/page-11

Very handsome it certainly is. Might well be worth  investigating gun bluing solution...

 :ThumbsUp:

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 30, 2020, 11:28:51 PM
It was over on the Marion Valve Engine build thread, here:
Started here, with link to the instructions I followed:
https://www.instructables.com/id/High-Quality-and-safe-Nickel-Plating/
http://www.modelenginemaker.com/index.php/topic,9312.msg210244.html#msg210244 (http://www.modelenginemaker.com/index.php/topic,9312.msg210244.html#msg210244)
More a few posts after that one, and here too
http://www.modelenginemaker.com/index.php/topic,9312.msg210244.html#msg210244
Its quite easy to do, I recommend getting a variable power supply if possible so you can adjust the voltage - higher is quicker, but rougher finish, around 6 volts is good. The distance to the part changes it too, the closer the faster/rougher. Distilled water, non-iodized salt, a Nickel rod/plate for a source, and a plastic container are the only other parts you need. No nasty acids involved, and you can re-use the solution so a lidded container is handy to store it in. I've since done a bunchof knobs for the Lombards up at the museum, as well as parts for several models. After plating, you can buff the plating to shine it up.

Chris - thanks for this. Yes, it looks good. And that engine it's on is a beauty. Not sure if nickel plating is for this here cylinder of mine, though not ruling anything out at this stage...

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: crueby on July 01, 2020, 12:50:45 AM
This conversation got me curious about whether the plating would work on cast iron - so, took the piece of Durabar that I have, stood one end into the container and hooked it up for a while:
(https://i.postimg.cc/y8bQJGHv/IMG-7277.jpg)
Thats an official 'Yup - it works!'. Shows the angle it was at in the liquid nicely! Raw iron on the left, nickel plated on the right.
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on July 01, 2020, 08:10:55 AM
Wipe down with an oily rag after running and drying will do unless you store the engine in adverse conditions. After all the inside is bare iron and won't be getting any additional coatings.

Biggest problem I can see if plating the cylinder is keeping the bore free of plating.
Title: Re: A Simple Uniflow Engine
Post by: crueby on July 01, 2020, 01:17:42 PM
Wipe down with an oily rag after running and drying will do unless you store the engine in adverse conditions. After all the inside is bare iron and won't be getting any additional coatings.

Biggest problem I can see if plating the cylinder is keeping the bore free of plating.
Vinyl tape on any portion keeps it clear of plating, could put a piece over the ends of the bore to seal it off. Or put the cylinder caps on.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 01, 2020, 01:33:01 PM
Well, guys - this is exactly the kind of discussion I was hoping for when I asked the question.

Chris - your nickel plating looks great and clearly works on cast iron. I'll keep the idea in mind for future projects. However, I have decided to give the gun blue (as suggested by John) a go as it's more what I'm aiming for in this application, so I ordered a tub of this:

https://www.amazon.co.uk/Bisley-Gun-Blue-75g-Tub/dp/B00H5LRDKC/ref=sr_1_1_sspa?dchild=1&keywords=gun+blueing&qid=1593606391&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUE1SExURE4ySkpMR1omZW5jcnlwdGVkSWQ9QTAxODY1ODkyWDIzRTMyRk0yMFAmZW5jcnlwdGVkQWRJZD1BMDQ4NDQzNjNOVFlDVVA5NjQ1T0Umd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl

It should be easy enough to manage as it comes in the form of a gel, and at less than a tenner a tub it doesn't represent a big risk.
Title: Re: A Simple Uniflow Engine
Post by: crueby on July 01, 2020, 03:55:40 PM
Looking forward to seeing how it looks. As I recall blueing chemicals work on iron and steel, not well on most stainless steel. Great way to get the color without adding thickness.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 01, 2020, 08:30:08 PM
Yeah - it will be interesting. I get the impression that the colour ranges from dark blue to black, depending on number of applications, etc.

Will be pleased if I can hold it to a nice dark blue but we shall see...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 05, 2020, 10:18:38 PM
Drilling and tapping the cylinder cap for the valve.

This obviously had to be concentric with the bore. After remounting the cylinder in the lathe and watching it wobbling around, I decided to do it in the mill instead.
 I used a new toy - a coaxial centre indicator - for the first time:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/869932.jpg)

Before plugging it into the mill spindle, I opened the box and showed it to my good lady, who said 'it looks like a piece of medical equipment'. I agreed with her on that point, and quickly took it back to the workshop so as not to further alarm her. It worked well. The hole for the valve was found with the cylinder cap removed and the extension of the indicator inside the open cylinder. The cap was then put back in place and centre-drilled, drilled and tapped. The thread was tested by screwing in the valve. I am using an off-the-shelf check valve because work (hopefully) smarter not harder:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/869931.jpg)

Nice solid connection.

However, just to keep things tight and pleasing, I wanted the internal end of the valve to be flush with the inside of the cylinder cap, so I counterbored the hole using the biggest endmill I have, to create a recess:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/869954.jpg)

I was pleasantly surprised to find that my measurements were pretty decent:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/869953.jpg)

And so, state of the art so far:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/869952.jpg)

It's starting to look like something - maybe not an engine yet, but at least a cylinder.

Now, another question for you guys: will this uniflow cylinder (about 36mm diameter) require drain cocks? And if so, where should they be positioned?

gary

Title: Re: A Simple Uniflow Engine
Post by: Jasonb on July 06, 2020, 07:02:24 AM
well it's quite a solid lump so will be prone to condensation, the drains can be used to remove that and also to allow steam to be blown through teh engine to warm the cylinder.

Ideally put the holes at the holes so they break into the bore as low down as possible, (can be drilled from the side if that suits) and as close to the ends as possible. But the steam is likely to carry condenste with it where ever the holes are places.
Title: Re: A Simple Uniflow Engine
Post by: simplyloco on July 06, 2020, 08:23:55 AM

Uniflow engines are not my game, but cylinder drain cocks are useful in preventing a hydraulic lock on startup.
John
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 06, 2020, 09:58:22 AM
Jason and John - thanks.

Drain cocks it is.

 :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on July 06, 2020, 11:44:57 AM
Hi Gary, thinking in particular about the ďuniflowĒ engine layout, I have to agree with the recommendations for condensate drains.  But where to put them is an interesting question.

The exhaust is wide open when the piston is at the bottom centre, but of course it is closed when the piston approaches the top, to condensate has no where to go.  The valve cannot lift to open to the exhaust as with a slide valve engine.  And of course the inlet valve has steam pressure holding it closed, and further more it is not at the bottom for easy flow of condensate.

If the cylinder is horizontal, then at the bottom, but very close to the top head, so condensate outlet is facilitated by gravity as the piston approaches the top dead centre.  (Away from the crank shaft.)

If the cylinder is vertical, then the condensate drains should be at the top, near the head, but at any orientation that suits the rest of the arrangement.

Itís looking good so far.

MJM460
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 07, 2020, 04:33:31 PM
Hi, and thank you MJM.

The cylinder will be horizontal.

I have ordered two drain cocks today - Stuart Models type.

I reckon one should go as you and Jason have suggested, and the other just in front of where the face of the piston will be at bottom dead centre. They will both be on the same side of the cylinder and as low in the bore as I can get away with.

Is that a  reasonable plan?

gary
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 07, 2020, 10:56:54 PM
Returning to the crank webs: my previous efforts to make these in the lathe using the 4-jaw independent chuck were not successful. For reasons that I have not yet figured  out, the holes were out of parallel, which would have put the journal out of parallel with the main shaft. So I tried a different tack. I glued the two rough-cut pieces of steel for the webs together with superglue (as on page 4 of this thread), and squared them off in the mill. The holes were then drilled and reamed with the two webs glued together. At one point the heat generated by the drilling destroyed the superglue and the webs came apart but I managed to rescue that and glue them back together again.

Next - with them still glued together - I rounded the corners with a corner-rounding endmill...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870114.jpg)

... after which - with them still glued together - I tidied the milled corners up a bit with a file...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870113.jpg)

... before using a small blowlamp to break the superglue bond and separate the webs. You know when the glue is about to give when it starts to smoke, and believe me you do not want to be breathing that smoke. There is still a bit of filing and polishing to do on the webs, but mission accomplished - the holes are all parallel and the webs sit nice and square on what will be the shaft and journal:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870112.jpg)

And here is the story so far:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870115.jpg)

Thanks for all your help and advice to date...

gary



Title: Re: A Simple Uniflow Engine
Post by: simplyloco on July 07, 2020, 11:43:58 PM
I look forward to seeing this run!
John
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 07, 2020, 11:49:25 PM
Thanks John.

So do I, even though it will be a while.

My main anxiety at this point is about whether or not these two flywheels are big and heavy enough.

There's only one way to find out though...
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on July 08, 2020, 01:14:21 PM
Hi Gary, crankshaft looks like you solved the problem.

With the drain cocks, the issue is that the condensed water is virtually not compressible, so when the piston approaches the top head, very large forces are created in bringing everything to a very sudden halt if there is no where for the condensate to go, and of course, gravity has already made sure it is on the bottom, so that is the best place for the drain valve.

At the Botton centre, I am not sure that the drain is really necessary, as the piston does not trap the condensate at that end.  In part it depends on where the exhaust port is, usually on the bottom with a horizontal cylinder, so any condensate goes out with the exhaust steam.  Otherwise any condensate formed when the engine is running can be a problem.  And you donít normally leave the condensate drains open once the engine has warmed up and is running.

I canít really see any reason not to put a drain at the bottom, I am just not sure what it will achieve.  I would save the extra valve for the next project.  If the exhaust is actually at the top, even a small port at the bottom, piped into your separator, will do the job as an auxiliary exhaust, and do no harm as it is closed off by the piston once it is on the way back to the top.  A peculiarity of the uniflow design.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 08, 2020, 10:27:23 PM
Thanks MJM - you have given me food for  thought regarding the cylinder drain cocks and the exhaust. I may come back to you on that for further advice when I get back to working on the cylinder.

Meanwhile, a little bit of progress with the crankshaft this evening. The webs were given a further clean up using my cheapo Dremel copy with a small flap wheel. There is still some way to go to make them look really nice but that can be done once the crankshaft is finished.

I decided to use the Loctite and pins approach given that this is my first proper crankshaft. In the photo below, the journal has been fixed into the webs with 638. The actual shaft is still loose and is just in situ to keep everything in line:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870213.jpg)

Tomorrow night I'll Loctite the shaft in and all being well will do the pins at the weekend.

Maybe my next crankshaft will be silver soldered...  :)
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 12, 2020, 10:26:45 AM
Time for another bit of state-of-the-art CAD:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870414.jpg)

It's a peculiarity of mine that I prefer to express metric measurements in centimetres rather than millimetres.

This is an actual size drawing of the cylinder based on the original plans by Stan Bray scaled up to x3.5, along with the piston. Note the length of the piston, which removes the need for a piston rod and crosshead guide. This is taken from the plans. Because nature is notoriously reluctant to be scaled, I am a little concerned that the much greater mass of this piston (in the original the diameter is only 10mm)  could make it difficult to drive. I initally considered modifying the design with a shorter piston, piston rod, crosshead and guide, but have decided to stick with the plans as it is one of the characteristics of the design. Having never made a crosshead guide etc. before, I would have liked the challenge, but there will be plenty of opportunities for that in the future.

Should the weight of the piston turn out to be a problem I'll just have to modify it, either as above or perhaps by making it hollow. But to be honest I can't really see it being a problem, as this engine will run on a really good boiler. More of which in due course...  ;)
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 12, 2020, 10:20:24 PM
Pinning the crankshaft. Being a novice I needed guidance, and found it in a youtube video by Keith Appleton. The photos below don't need much in the way of comment:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870503.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870502.jpg)

I drilled the holes with some trepidation for fear that the bit would wander when it hit the silver steel bar...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870505.jpg)

... no problem though. Four good holes:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870504.jpg)

Matching various diameters of thin silver steel with various small drill bits left me only one option. Fortunately I had just enough of this diameter to make four pins...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870508.jpg)

... at which point a slight annoyance occurred. I had tested the drill and silver steel rod on a piece of scrap steel and the result was a pin that was satisyingly tight and had to be tapped in with a hammer (as recommended by Keith Appleton). However, in making the actual crankshaft I 'pecked' with the drill to clear swarf. This enlarged the hole a small amount and as a result the pins were much less tight in the holes - not rattling, but a sliding fit. However, I poured plenty of Loctite into the holes before pushing in the pins. I suspect it will be ok. If it isn't, it will just have to be fixed later. The crankshaft in progress will now be left for a couple of days to let the Loctite harden properly.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870507.jpg)

I then made a start on the piston. All I have to cut cast iron with is a small angle grinder, and this made such a rough cut that when I tried to face the end of the bar the tool kept catching and pulling the bar out of true. Fixed steady to the rescue! First time I have used it in ages:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870506.jpg)

It did the trick, and I faced both ends of the bar and spotted them with a centre drill, then removed the fixed steady, put the live centre in the tailstock and began turning the bar down towards diameter before calling it a night.

gary





Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 14, 2020, 11:25:37 PM
The redundant part of shaft between the crank webs was cut away, and the protruding ends of the remaining shaft and the ends of the pins were filed flat. This gives me something which bears some resemblance to a crankshaft:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870745.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870744.jpg)

I hope it runs true! Haven't tested it for that in the lathe yet...

It still needs a bit of shaping, tidying up and polishing, for which this toy - ordered a couple of days ago and still to arrive - should prove invaluable:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870742.jpg)

30mm belt, variable speed. Looks good to me, but another thing to find space for. Space that I don't have.

I then switched back to the piston. An indexable round-tipped carbide tool seems to create the best finish on the cast iron. I am creeping down to diameter taking very fine cuts with it, alternating with a piece of wet and dry paper wrapped around a square block of wood moving evenly back and forth across the surface, and using the cylinder as a gauge:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870743.jpg)

Nerve-racking stuff, for fear of overshooting. It's almost there, but the hour was late so I decided to call it a night and leave the final diameter to another day...
Title: Re: A Simple Uniflow Engine
Post by: Johnmcc69 on July 15, 2020, 02:02:56 AM
 :ThumbsUp:
 Nice work Gary!
 No rush, take your time, it's all coming together nicely!
 :popcorn:
 John
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 15, 2020, 08:20:15 AM
Thanks for your positive words John.

I have often been inclined  to rush things, but this pastime is teaching me to take my time...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 15, 2020, 10:27:32 PM
I have often been inclined  to rush things, but this pastime is teaching me to take my time...

Argh. I should have sufficient self knowledge by now to be aware that when I say something like that I am tempting providence.

The piston makes a nice sliding fit in the bore, and pulls a good vacuum with steam oil. And I'm pleased with that radius at the shoulder, which wasn't in the original plans:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870787.jpg)

However, as we see more of the piston, machining marks become apparent...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870785.jpg)

... and the more of the piston we see, the more apparent the marks become (and in the next photo they are actually more apparent than they are when the piston itself is inspected)....

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870786.jpg)

... until we look at the top, say, quarter of the piston and the marks become less apparent again:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870784.jpg)

I did exactly what John counselled me not to do: I failed to take my time. The piston is now a good fit, but I came too close to overshooting with the tool and it left me with machining marks along the bottom 3/4 of the piston which - if I were to polish out - would probably leave me with the piston too loose in the cylinder. For all I know, the machining marks may not make a difference in functional terms, and the engine may run fine as is. However, at bottom dead centre quite a length of this piston will be visible and it will pain me to see those marks.

I have a few different ideas for possible fixes for this, ranging from leaving it alone through various other options to making a whole new piston. I won't go into these here because I'm going to live with this for now to see what emerges when I eventually run the engine with it in situ before making any modifications. If you have any ideas yourself, please feel free to post them and I'll let you know whether or not they are the same as mine. Remember that as it is this is a long piston which obviates the need for a piston rod, and the connecting rod joins to a hole drilled through the boss at the back end of the piston.

However, there is another isssue: I centre-drilled a small hole in the back end of the piston so that the tailstock centre would hold it true while I turned the piston. This hole may be a bit too deep to the point that it may well encroach on the hole for the wrist pin. I could get round this by - as per plans - milling a slot down the centre of the boss at the back end of the piston to effectively create a fork on the end of the piston which would be drilled through for the wrist pin. The too-deep centre-drilled hole would become history that way. But I really like the idea of having the fork on the connecting rod and a single flatted projection on the back of the piston sitting between the two 'prongs' of the connecting rod fork. In this latter scenario the centre-drilled hole may make mischief with the bearing, unless I shorten the whole thing a bit which I may do but I would prefer not to mess with the original proportions. .

If you get my drift...

Will evaluate both of these issues when deciding whether or not to try to salvage this piston or make a new one.

Suggestions welcome...



Title: Re: A Simple Uniflow Engine
Post by: Jasonb on July 16, 2020, 07:06:43 AM
If you do make a new one don't use that round insert tool as they will tend to get pushed off the work trying to take fine cuts or risk chatter on heavier ones (your marks look like chatter) Either switch to sharp HSS or a **GT insert with 0.2 or 0.4 tip rasius for the last millimeter.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 16, 2020, 08:14:52 AM
I found the round tool was fine on the deeper cuts but it did start to chatter on the final fine ones.

Advice noted, though! Will try what you suggest.

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 20, 2020, 09:45:27 AM
I almost wish this chatter-marked piston wasn't such a good fit in the cylinder bore so I wouldn't be in a dilemma over whether to keep it, modify it or make a new one!

However, I have decided to press on with it for the time being rather than end up chasing my tail. Decisions on what to do about it will be made later in the build. To be honest, the photos make the marks look worse than they actually are, even though they do remain an issue.

Here, a flat is being milled for the 'crosshead' hole. I used the rotary table with dividing plate and its tailstock as an easy way of flipping the part 180 degrees to ensure parallelism of the two flats:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/871242.jpg)

Both sides done. A light touch with the new belt sander (when it arrives) will tidy things up, but overall I am pleased with this bit:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/871241.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/871240.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/871239.jpg)

Then - after marking out the distance from the top end of the piston to the centre of the hole using a height gauge on the surface plate, back into the mill setup to find the centre in the lateral orientation:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/871238.jpg)

I did also get the hole drilled and reamed but my camera ran out of battery so more to follow...
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on July 20, 2020, 12:49:19 PM
Hi Gary, more good progress.

Personally, I would not worry about those chatter marks if you are happy with the fit.  There is just a possibility that they will carry a little oil and help with lubrication and sealing of the cylinder.  A bit of a wild guess, but interesting things happen on that scale.   Keep with it until you find a problem.

When it is all complete and working, if you still want to, that is the time to consider making a second one.  My little cylinders seem to work quite well with just a good fit, and a couple of ring grooves which, rightly or wrongly, I consider as labyrinth grooves which help reduce the steam bypassing the piston.  Your marks are a much finer scale, where different hydrodynamic issues rule.  All interesting learning.

MJM460


Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 20, 2020, 12:57:47 PM
Thanks MJM.

Pretty much how I see it too. I'm sure the piston will work fine as is so it would be disheartening to get bogged down with it at this point.

It had also occurred to me that the marks may help carry some oil.

The thing that annoys me is that with this long piston (which removes the need for a crosshead and guide) some of the marks will be visible at all but top dead centre.

But never mind - as you say I'll come back to it at the end and if all works fine and the marks still bug me I can always make a new one at that point, or possibly modify this one.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 26, 2020, 12:40:33 AM
Have been painting the exterior of the house all week, so progress has been slow for the past few days.

Fortunately it rained today. Returning to the main bearings, which are made of bronze:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/871862.jpg)

A rough trial assembly of the crankshaft with flywheels, pulleys, collars and bearings in situ:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/871861.jpg)

A close-up of one of the bearings in incomplete state:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/871860.jpg)

The part on the left is the bearing itself, drilled and reamed to a nice sliding fit on the shaft. It has two diameters - the flange at left, and the main part of the bearing adjoining it. This narrower part will pass through the frame of the engine and then through the retaining collar as you can see here. A circle of small screws will pass through the flange, the frame and part way through the retaining collar, holding the bearing in position in the frame. The surplus length of bearing (just to the left of the cast iron collar) will be turned flush with the bearing retaining collar once I have gauged the final size using a piece of frame material between the flange and the retaining collar as a guide. The bearing at the other end of the crankshaft will be a mirror image of this one, and the frame will also be symmetrical.

Finally, I decided today that the connecting rod will be a composite structure. The main length of rod will be 12mm EN8 steel, but - like the big end - the crosshead end (including the fork) will be of cast iron. The components will be joined together with M12 threads and Loctite thread seal. The picture below shows that a start has been made on the crosshead end and that there is still quite a way to go with this part. The fork has to be milled and drilled and the whole part will need considerable shaping to make it look leaner and more elegant:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/871859.jpg)

In the lathe chuck the steel rod awaits a corresponding thread to connect it to the crosshead.

Weather due to improve tomorrow, so it's looking like I'll be back on painting duty again...  >:(



Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on August 17, 2020, 12:26:24 AM
 It has been a while.

Spent the last few weeks painting the outside of the front of the house, waterproofing a section of flat roof, going on a campervan staycation and doing an exotic post-steampunk makeover on our bedroom:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/873697.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/873696.jpg)

Oh - and working.

Finally got back into the shop this weekend though. Made a start on the connecting rod and crosshead.The rod part is bronze; the crosshead and big end will be cast iron:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/873694.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/873695.jpg)

The whole thing will end up much slimmer and will hopefully be given some reasonably elegant shaping. The bronze section will be quite short as the whole assembly from hole to hole is only 16cm. Remember this engine has no piston rod, just an extended piston.

I paused there and swapped jobs to avoid having to do too much changing of setups in the mill.

The new belt sander has arrived:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/873693.jpg)

It's much smaller than I imagined it would be. This is a mixed blessing because I have very little room to spare in my shop but was still able to find a bit of bench space to fix it to. On the other hand the limited capacity means that there are things you can't do with it. It's a neat little tool - variable speed. I got it on Amazon and when it arrived the power unit was lifeless. I contacted the suppliers and they replaced it in double-quick time all the way from China and as compensation for having sent me something that didn't work they also gave me an extra set of belts and a refund of £30 of the cost of the machine! The belt sander enabled me to get the crankshaft to this point:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/873700.jpg)

By no means perfect but starting to look reasonable. I'll leave the final cleanup till the end of the build.

Small flats were then milled on the crankshaft - one for each component that will  be mounted on it:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/873702.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/873699.jpg)

I used the dividing setup to rotate the shaft 180 degrees after milling each flat so that alternate flats would be on opposite sides of the shaft. I was thinking about strength and the avoidance of warping the shaft by not having all the flats on one side, but I suspect it wouldn't have been an issue really. The flats are only 0.5 mm deep. The flywheels, pulleys and collars are held in place by stainless steel grub screws which are supplied with flat ends which will of course bear against the flats on the shaft, providing a nice positive drive. This took me to this point (though here the grub screws arent tightened and the components aren't aligned:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/873698.jpg)

Looks not bad, but then I chucked it up in the lathe using an ER32 collet chuck to see how true it would run:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/873701.jpg)

Visually everything is fine apart from one of the flywheels, which has a distinct wobble of about 0.5 mm or maybe even a bit  more. Damn!

I'm pretty sure the problem lies in the flywheel itself. If I can I''ll true it up in situ on the shaft, and it's all set up ready to go tomorrow. However, I suspect it will ring like a bell and make pretty patterns in the brass, especially as I'll need to work at the tailstock end for one side of the pulley. If that happens I may take it off and turn it on a short mandrel,  but then it may still not run true when it's back on the shaft again and still require to be finished in situ. The other thing about this that's bothering me is that this will not only shave thickness off the offending flywheel, but also off the other one so that they are in balance with each other. The weight of these flywheels concerns me even as they are, as they seem pretty light relative to the long cast iron piston. Ultimately if they prove to be too light I'll either have to modify them somehow or make new, bigger ones. I'd definitely prefer not to have to do either of these things, though...



Title: Re: A Simple Uniflow Engine
Post by: crueby on August 17, 2020, 12:50:05 AM
Nice progress Gary!  For the wobble on the flywheel, one thing you could try is to put two more grub screws in, so that they are spaced evenly 120 degrees apart. That way you can tighten/loosen them to take up any play on the shaft, which is likely the source of the problem - a tiny bit of play at the hub magnifies out to a noticeable wobble at the rim. When it will fit in the space available, I've switched to using a taper-lock setup on all my flywheels, runs much truer and is still removeable - just showed that over on the Mann truck thread. May not be room for that on your engine, so the other grub screws would do the same job. You would not need more flats on the shaft, the one is fine to give it grip, the others are just for alignment. A little Loctite Blue on final assembly will keep everything in place but still allow removal if need be.

Oh, and watch how much you drink before bed, you might get nightmares of being caught in a giant machine with that paint job!   :LittleDevil:
 :cheers:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on August 17, 2020, 01:02:54 AM
Or maybe drink more to suppress the terror of it...?   :wine1: :wine1: :wine1:  ;)

No, tbh we spent quite a long time on marking out that big purple gear and its geometry has a surprisingly calming effect.  8)

Great idea with the extra grub screws Chris. Definitely worth a try, especially if it lets me avoid whittling down those flywheels. Will give it a try.

Was planning to look at your thread in a minute anyway, so will do so. I'm interested to see your taper-lock flywheels.

Cheers!

 :cheers:
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on August 17, 2020, 01:34:17 PM
Hi Gary, more good progress.  I would not worry too much about the flywheels being too light, it is very difficult to get a feel for how much rotational inertia is required for an engine, so I would always recommend trying it out before you decide on whether they are adequate.

Remember that flywheels are inherently balanced unless you go out of your way to give them some unbalance.  Certainly the piston mass will be the main cause of engine unbalance, but that has to be compensated for partly by adding weights, usually on the crank webs opposite the crank pin (not in line with it).  Even that only balances the forces due to the crank and big end being off the centreline.  Balancing the reciprocating mass of the piston requires a more complex arrangement.  The more important issue for this engine is the flywheel inertia required store enough energy to drive the piston over top dead centre against the incoming steam, once the peg opens the inlet valve, as the piston will still be moving towards the top dead centre, unlike your oscillating engines or a slide valve engine, where the valves normally do not open until the piston reaches top dead centre.  If the flywheels are inadequate itís slowest running speed might be quite high. Adding some mass to the rims might allow it to run a bit slower if necessary.   But again, now they are made, apart from thinking about truing them up, wait until you have the engine running to see what it will do.

Did you ream the bores of the flywheels?  Have you investigated to see if the bore is really out of line or just a bit loose?

That sander looks like a handy item, and the seller obviously treated you well.  Worth remembering for when you next need something.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on August 17, 2020, 11:43:22 PM
An evening of fretting, pondering and measuring as the inevitable mid-build crisis intensifies.

@Chris - I really hoped that your diagnosis was correct, but in this case I do not think it was. Everything runs reasonably true on that shaft apart from the flywheel in question. I loosened it and spun it on an unflatted part of the shaft - still the wobble. I swapped the two flywheels over - still the wobble on that same wheel. There is a very slight wobble on some of the other parts, including the other flywheel, but it is almost liveable with and will probably be fixable either by your three-screw method or a very minor skimming, or both. But the wobble on the wobbly wheel is in another league.

@MJM - the bore of the flywheels were indeed reamed and they make a nice sliding (almost piston and cylinder-like) fit on the shaft. I took the offending flywheel off and went on a measuring spree with the surface plate, height gauge and micrometer. The bore appears to be concentric with the outside of the central boss, but the outer parts of the wheel are out of true. The micrometer showed me that there is a variation in thickness of about a maximum of 0.4 mm around the wheel. That, I think, is what I'm seeing when I spin the shaft in the lathe.

I originally turned the flywheel+boss assemblies on a superglue arbour held in the ER-32 collet chuck, both sides in one setting. That should have left them true and of even thickness. However, I used the wrong tool and got a poor surface finish. Following advice on the forum here I put them back in the lathe and gave them a finishing cut on each side. I can't remember how I held them for this, but it's possible that I got sloppy and just put them in the three jaw and turned them over after finishing each side. I can think of no other reason why there would be variations in thickness at different points round this flywheel. If so, maybe I just got lucky with the other one.

I reckon the easiest fix will be to set up another superglue arbour and re-face the wheel both sides in one setting. If it ends up looking thinner than the good wheel, then the good wheel will get the same treatment. In theory (ha!) they should both run true after that. Any minor wobble at that point could - I guess - be rectified by the three-screw treatment.

I also have to confess that there is a very small visible runout in the crankshaft itself. I don't think that this is wholly due to runout in the lathe spindle. I trued up the lathe as best I could before beginning this build and it's not perfect but probably as good as can be expected from a standard import machine which is a few years old. But I did obsess over the lengths of silver steel bar that I bought to make the shaft with  and it seemed to me that none of them were perfectly straight. I didn't see any point in ordering more that would be the same, so I just used the best ones. We're not talking major runout here, but it is just visible in the lathe even with the tailstock centre holding it. However, in the finished engine the shaft will be held by a fairly robust bearing at each end and I'm guessing that this will stabilise it. I'll make a new crankshaft if  have to, but I think the inaccuracy is minor enough to get away with. We shall see...

Re-machining that flywheel will be starting point, at the very least.

@MJM - absolutely. I have no clue how this engine will perform or whether the flywheels will be adequate. I certainly won't be making any changes to them until I have seen it under air or steam. Preferably the latter!

Thank you both for your input. Even more so if you have read this lengthy post! If you think I'm missing something, please let me know...

 :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on August 18, 2020, 08:43:07 AM
On reflection - apologies for the length of the above post. This is pretty routine stuff really, and hopefully easily rectifiable. Hardly a 'crisis'! Have decided to true up the wobbly pulley not on a superglue arbour but fixed with the grub screw on a short arbour with a flat to mimic the shaft. Any residual wobble on it or any of the other components on the shaft can then be given a final truing up in situ.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on August 24, 2020, 12:20:20 AM
I trued up the wonky flywheel on a short mandrel milled with a flat to mimic the crankshaft.This helped a great deal and brought it to the condition that one would expect from a new flywheel before final truing up. The other flywheel was also skimmed to keep them the same size. Not a huge amount of metal needed to be removed, though it remains to be seen later in the build whether the two flywheels are heavy enough.

I then followed Chris' advice and made two extra holes in the bosses of both flywheels and pulleys. Blithely ignoring the wisdom of generations of engineers I did not drill the holes at an angle and consequently had to use my small Bahco adjustable spanner as a tap wrench due to lack of room for anything else. It went ok though. Keith Appleton would be proud of me.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/874274.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/874273.jpg)

For some reason I got mixed up and drilled and tapped the extra holes in the pulleys M5 instead of M6, but no  matter - I'll get some M5 grub screws and do the final truing up with them when the crankshaft is mounted in the frame. I also put a crown on the second pulley.

Truth to tell, there is a very slight but visible runout on the crankshaft. As noted previously, it may have been there in the silver steel bar from the start. Or perhaps in my lathe. I'm reasonably hopeful that the frame and bearings will accomodate this. If they don't, I'll make a new crankshaft - but fingers crossed...

With the crankshaft pretty much done for now, I went back to the connecting rod to set up for milling a slot to create the crosshead fork which will accomodate and articulate with the tab on the end of the piston. The tab on the piston is 9mm wide so figuring that an endmill will cut a little wider than its actual diameter I'm starting with an 8.5 for the slot but will swap this for a 9 if the slot isn't wide enough. You can always take away more but you can't put it back.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/874272.jpg)

This is not workholding at its finest, but I couldn't think of a better way to do it with the gear that I have. Still, it's cast iron and quite easy to machine so I'm hopeful that if I take light cuts with high cutter speed it won't move in the chuck. The fork will be radically slimmed down and shaped but I'm leaving that until it's functional for ease of workholding.

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on August 30, 2020, 11:43:53 PM
A reasonably good session this evening.

The chuck on the rotary table held the part perfectly firmly and allowed me to mill the slot for the fork without any movement:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/874892.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/874891.jpg)

Of course some metal has to be removed from both parts to allow the crosshead to articulate. I started with the 'tab' (don't know what else to call it) on the end of the piston:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/874890.jpg)

As you can see I used my 'one size fits all' corner-rounding endmill for this, so called because it's the only one I have. Every rounded corner on this engine will have the same radius!

It turned out not too badly:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/874895.jpg)

Should be fine with a minimal amount of tidying with a file or the belt sander.

It was then time to cross-drill the fork. I used my new electronic edge finder and the DRO to find the centre of the part:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/874894.jpg)

If you don't have an electronic edge finder, you want one. You really do. As soon as the sprung ball at the bottom of the probe touches the metal, the thing beeps and the red LED lights up. Way better than peering at a conventional finder...

The cross-hole was drilled and reamed 8mm to match the hole in the piston tab. Here you can see the piston temporarily connected to the fork with a bolt and dome nut:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/874893.jpg)

In due course I'll turn a bronze pin. There is still quite a bit of shaping to do on that fork, not least milling off those corners which are still preventing the joint from articulating adequately. After that it will be shaped for aesthetic reasons, as will the bronze connecting rod.

There is a small amount of lateral play between the cylinder tab and the fork. I suspect it doesn't matter, but if it does I can always widen the slot a bit and shim it with bronze washers. Hope not to have to do that though...

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 01, 2020, 11:22:19 PM
In order to allow sufficient travel, the corners of the crosshead fork were milled away using - you guessed it - my solitary corner-rounding endmill, which I have to say is a surprisingly versatile tool given that it only does one thing (does that make sense?!).

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/875091.jpg)

This still doesn't enable it to swing all the way round, but not an issue as it allows for an arc that is way wider than it needs to be to take the stroke.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/875090.jpg)

The crosshead is now functional though it needs a proper pin and it still has to be shaped and tidied up in the interests of elegance. However, before I do the latter I'm going to move on and start on the big end, which I suspect will be the trickiest component of the build.
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on September 02, 2020, 02:56:12 AM
Hi Gary,

More good progress.  Glad to hear the rounding over cutter is working well.  Much better to have one item that does its job well than several that do a bit of everything but all badly.

MJM460
Title: Re: A Simple Uniflow Engine
Post by: crueby on September 02, 2020, 03:26:35 AM
Very good! Watching along with the elves and popcorn...   :popcorn:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 02, 2020, 08:36:55 AM
Many thanks guys.

It's great to have your encouragement, which - combined with a sprinkling of magic dust from Chris' elves - will help me through this build...

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 06, 2020, 11:53:09 PM
Started on the big end.

Slow progress as there's always too many other things that need to be done, the result being a not-very-exciting post here.

Two pieces of square cast iron bar:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/875461.jpg)

Unfortunately I have no room for a bandsaw so the best tool I have for cutting this kind of stock is a humble angle grinder, which results in such a rough cut that I have to spend a fair bit of time facing the blanks. I cut the small piece first, then realised that it wasn't big enough so I cut a piece off the larger bar and decided to put it down to experience. However, it occurred to me that if I use the smaller piece to make the cap for the big end bearing it will save me from having to cut the bearing with a slitting saw. So, using my cheap bangood facemill (which seems to work fine) I am in the middle of milling the blanks to so that they more or less match each other as a starting point. There's quite a lot of iron there so it will take a fair bit of machining to get the big end to the desired final size and shape.

As you will know, while cast iron is easy to machine it is a grimy old process. The swarf gets everythere and it is a pain to clean up.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/875460.jpg)

Ah well... it's a wonderful metal nonetheless.

One step at a time...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 16, 2020, 11:15:27 PM
So...

...the two pieces of cast iron were milled to roughly the size and shape of generous blanks for the big end and bearing cap. Then two 6mm holes were drilled through the cap and counterbored. These were used to spot the locations through on to the main part of the big end, which was then drilled and tapped M6. The two parts were then fixed together with shortened M6 cap head screws and the assembly was put back in the mill and squared up:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/876150.jpg)

The hole for the bearing was then drilled and reamed to 12mm:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/876149.jpg)

This looks not bad, though the assembly is still massive and there is a lot of cast iron yet to be removed. Potentially more seriously, though - there is a very slight runout in that main hole. It may have happened because I forgot to lock the z axis of the mill before I drilled the hole, though I'm not sure. It is miniscule, and my instinct tells me that I'll get away with it, but I'm not experienced enough yet to have a sense of what the tolerances are and it is a pretty intergral component (well, aren't they all?!).

If it does turn out to be a problem, I wonder if putting a spring washer in each of the cap counterbores would give the bearing a bit of adjustability and wiggle room while everything beds in during the first few runs of the engine. Any thoughts on this would be most welcome, as would any alternative tips as I'd rather not have to remake the big end.

Overall, though, I am daring to hope that the runout is too slight to be an issue over the short length of the crank journal.

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 17, 2020, 11:24:16 PM
The connecting rod will screw into a hole at the bottom of the big end. This evening I drilled and tapped the hole. The big end was held in the milling vice and centred in both axes using the DRO. This mill is quite small and doesn't have the capacity for a piloted spindle held in the drill chuck with workpieces over a certain (and not very great) height, so I put the first tap straight into the drill chuck and used 'tapping mode' to start the thread. Most of you will know this function on some of these import mills, but if you don't, there's a green button on the end of each arm of the downfeed handle which changes the chuck direction with a single press when tapping mode is activated so you can withdraw the tap every few revolutions to clear the chips. It's pretty handy:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/876214.jpg)

State of that mill but I see no point in cleaning it all up when I'm going to be milling more cast iron over the next few sessions.

Unfortunately in this particular instance tapping mode didn't work very well as the tap kept turning in the chuck, but it did manage enough threads to give me a perpendicular start, after which I was able to hand tap it in the bench vice without worrying about an off-centre thread. No big deal; a routine operation, but hey - I like pictures  :) :

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/876213.jpg)

All good - looks nice and straight when the blank for the connecting rod is screwed in. Still loads of swarf to make getting that big end down to a reasonable size and shape though:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/876217.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/876216.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/876215.jpg)

Cheers,

gary
Title: Re: A Simple Uniflow Engine
Post by: propforward on September 20, 2020, 12:40:39 PM
Hi Gary,

Some excellent work here as always. I think you are very critical of your own work. Itís all looking like great progress to me. Is that piston made from a cast iron bar, or is that steel?
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 20, 2020, 01:11:40 PM
Thanks Stuart - very kind of you.

It's cast iron, as are the cylinder, the crosshead and the big end.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 21, 2020, 11:25:24 PM
There will be a spigot protruding from each side of the big end, the faces of which will run against the crank webs. The lines scribed on the assembly in the photo below are set apart at a distance which is a little bit wider than the final overall width of the big end from the face of one spigot to that of the other:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/876506.jpg)

I milled down to these lines with the face mill, then again with the height gauge and surface plate marked out the final width of the big end minus the length of the spigots. You can probably just about make out these two new lines in the photo below. The assembly was transferred to the independent 4-jaw chuck in the lathe. A short length of 12mm silver steel bar was held in the tailstock chuck and pushed through the split bearing in order to help with centring, to lend rigidity to the setup and to test whether or not the miniscule degree of runout in the bearing hole (discussed a few posts back) was likely to cause problems. I'm pleased to report that as far as I can now ascertain the amount of runout over the short length in question is insignificant.

A turning operation was then embarked upon to narrow down the body of the big end while leaving the spigot on each side standing proud of the face:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/876505.jpg)

I'm using a circular carbide tool to leave a radius where the spigot will meet the face. This should look good but it will also be stronger than would a ninety degree angle, as per a suggestion from Jason further back in this thread.

This turning operation is not one to rush, what with the unbalanced weight of cast iron spinning in the chuck, so it is taking a while to do, over several sessions...


Title: Re: A Simple Uniflow Engine
Post by: propforward on September 22, 2020, 06:47:01 PM
Nice. Looks like a solid approach - excellent finishes too.

I suppose you could have opted for a faceplate mounting, then added some balance weight if you had really need to go with higher rpm's, but this set up looks like it worked out really well for you. Easier than setting up on  a face plate for a start.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 22, 2020, 08:14:06 PM
Hi Stuart - yes, I did consider using the faceplate but on balance (no pun intended) I decided to just go with the 4-jaw. It's a slow job but there's no rush really. I'm away from home until Friday but hope to make a bit more progress over the weekend...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 28, 2020, 12:09:38 AM
The main body of the big end in progress has now been more or less slimmed down to final width, though the 'spigots' projecting from the sides still need to be brought to final dimensions. After that there is still more work to be done on the overall shape of the part, both for weight reduction reasons and for looks:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/876999.jpg)
Title: Re: A Simple Uniflow Engine
Post by: crueby on September 28, 2020, 12:23:13 AM
Nicely done, coming along great!
Title: Re: A Simple Uniflow Engine
Post by: propforward on September 28, 2020, 01:17:09 AM
Nice work Gary!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 28, 2020, 10:05:13 AM
Many thanks guys.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 28, 2020, 11:14:26 PM
In order to check that the two spigots were the same length, I clamped a couple of parallels on to the assembly and measured the gaps with the inside jaws of the calipers:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/877081.jpg)

The difference was negligible so I considered the part to be symmetrical. Measurement of the overall width told me that I needed to remove 3mm for the assembly to fit between the crank webs, so I took facing cuts with an endmill to reduce each side by 1.5mm. I will confess to you that I have a photo of this operation but the mill is so covered in cast iron swarf at this point that I'm ashamed to show it. I am, however, pretty pleased with the result, which is a smooth-running fit, snug but not tight:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/877080.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/877079.jpg)

I'm quite pleased with this, but you can see that even when I have reduced the size of the big end (which is the next step), the flywheels will still be quite small by comparison. As discussed somewhere above, I have no clue as to whether or not this will be a problem. The plan is to press on with the build and find out when I first test the engine on air. If I have to enlarge them I will do so.

Meanwhile - iron age digital compact camera?

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/877078.jpg)

There's a lot of cast iron yet to remove from the big end, and even these rounded corners may yet disappear with some closer machining to reduce the size. But still, progress...

Title: Re: A Simple Uniflow Engine
Post by: crueby on September 28, 2020, 11:37:06 PM

.......
Meanwhile - iron age digital compact camera?
(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/877078.jpg)

Mil-Spec iPhone! 
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 28, 2020, 11:40:50 PM
 :)
Title: Re: A Simple Uniflow Engine
Post by: propforward on September 29, 2020, 12:02:54 AM

.......
Meanwhile - iron age digital compact camera?
(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/877078.jpg)

Mil-Spec iPhone!


 :ROFL:   :lolb:

I literally LOLíd at that.  :facepalm2:
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on September 29, 2020, 12:07:36 AM
Hi Gary, more great progress.

The main effect of the size of that big end is on engine balance, and as I believe it will be a relatively high speed engine, a large unbalance will get exciting.  However, the big end mass can be balanced by weights added to either the crank webs or a smaller mass at the rim of the flywheels, and then it just adds to the moment of inertia of the flywheels.  If my memory serves me the maths says you balance the weight of the big end plus about one third of the connecting rod as a starting point.  You would divide this and put half each end of the crankshaft.

However, as you add your trademark wonderful artistic touches, it is worth considering detail that  reduces the remaining mass in your design. 

For my part, the best piece of material to use is one you already have, or can easily source, that is big enough and regular in shape so it is easy to hold while you drill and tap for the securing bolts and that all important bore.  Then you can make as much swarf as you fancy in trimming away the bits you donít need.

It appears that in doubling the original plan size, you have also doubled the bearing cap bolts and spacing.   As it is not a scale model, you probably could have got away with leaving some of those details a bit smaller, but that is an idea for the next engine, no need to change now.  I find that each successive engine, I am prepared to makes bolts a little smaller and clearances between features a little tighter, though having tried 2 mm bolts, I think further progress in that direction will be limited, and I prefer 2.5 mm and larger.  Not sure that I will ever get to 1 mm like others on this forum.  They show amazing skill that I can only admire.

MJM460
Title: Re: A Simple Uniflow Engine
Post by: steam guy willy on September 29, 2020, 02:20:55 AM
Hi Gary, Talking about nuts and bolts... here in The Uk we have EKP Supplies that make BA nuts and bolts with a smaller head size... This gives you a larger stronger thread with a more scale size bolt head,  these bolts go down to 10 BA with 12 BA heads. here is a small part from the catalogue !!

Willy
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on September 29, 2020, 08:26:24 AM
@ Stuart - glad you liked it. The viewfinder works fine but I'm now trying to figure out how to get it to take pictures.

@ SGW - thank you. I tend to work in metric and most of my tooling reflects that, but good to know nonetheless. All good info for future use.

@ MJM - on weight and balance: yes, I can imagine that if that big end were to be left as is the engine would be bouncing all over the place, and no great benefit in bolting it to the bench as it would probably take the bench with it. My plan at this stage is to carve away at the big end to lighten it as much as possible (hopefully in a way that looks good too), then see what I'm left with. Making the flywheels bigger and heavier will be a second step to be taken only if required.

Your point about scaling - yes, absolutely. This engine is 3.5 times the size of the original plans, and most of the main dimensions (bore, stroke, throw, combined mass of flywheels, etc) reflect that. In terms of finer details, though (e.g. the size and spacing of the screws for the big end cap) - it was pretty much guesswork. I am aware that I have a general tendency to over-engineer things, though, and you make a very good point about not needing to scale everything up. As you say, a learning point for next time...

Thanks all.

 :ThumbsUp: :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 05, 2020, 10:56:50 PM
Slow but steady progress... and a disaster!

I roughed out the rest of the main form of the big end by drilling and milling, but decided to finish it the old-fashioned way - with files. It's taking shape, though there is still a way to go to get the shape right. It's still going to be quite hefty but it's smaller than it was:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/877797.jpg)

Work in progress.

But a very bad thing happened this weekend. I got an e-mail from one of the neighbours at my place in France to tell me that the huge gales they have been having there have removed one third of my workshop roof. He will cover the machines inside in plastic sheeting when the weather dries up but he can't climb over the wall so will have to wait till he receives the keys which I posted today. I'm keeping my fingers crossed that my builder friend who lives several hundred kilometres away in another part of France will be able to drive up and put on a new roof for me. However, he (rightly) can't do this straight away because his first grandchild is due to be born any time now! Ordinarily I would go over but due to covid there would be quarantine on my return for both me and my partner and we are both up to our eyeballs in work which can't be sidelined.

So basically I have to just swallow the fact that my lovely machines (some vintage in excellent condition) are going to be rained upon - possibly numerous times - before anything can be done about it. My neighbour took photos.

The exterior of the building, showing the missing roof section:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/877796.jpg)

The view down through the gap where the roof used to be:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/877795.jpg)


Utterly bleak.

 :disappointed:
Title: Re: A Simple Uniflow Engine
Post by: crueby on October 05, 2020, 11:23:54 PM
Oh no! I hope it can get protected well enough.  :(
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 05, 2020, 11:28:29 PM
Yes... thanks Chris.

My friend will hopefully be able to go there to put on a new roof in the not too distant future, but it all takes time and being the Autumn it will rain regularly before that happens.

And when it rains in France, it can really rain...
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on October 06, 2020, 12:23:30 AM
Sorry to hear about the workshop roof Gary.  Hopefully those keys will arrive, and the neighbour will be able to secure some waterproof sheets over the machines.  Thank goodness for good neighbours.  At least you have been alerted so can start making arrangements to get repairs started.

I wonder if it would be worth arranging for the neighbour to have some WD40 or Innox to spray over the machine surfaces when the keys arrive.  WD 40 might also be worthwhile in the electrical parts, but I expect others will also have good ideas to minimise the damage and what to inspect and do when you are at last able to return.

The big end is looking good.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: propforward on October 06, 2020, 02:18:02 AM
Gary, I'm heartbroken to see this. I hope your neighbour can help you out. WD-40 is a good idea in my view - tarps and WD-40 will go a long way to help protect those machines.

Best of luck to you!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 06, 2020, 08:40:47 AM
Thank you both for your empathy.

Indeed, WD40 is part of the plan. I'm hoping that if the rain abates for a few days my neighbour will drench the machines in WD40 then cover them in plastic sheets, pending (hopefully) the arrival of my builder friend to redo the roof. Once the new roof is on, the plastic can come off the machines to let everything breathe. No doubt there will be restoration work to do at some indeterminate point in the future.

One good thing is that before shutting the place down every Autumn I have liberally sprayed everything with WD40 as one of the last jobs before I leave, the last time being October 2019. Fingers crossed that will help a bit.

We put on the existing roof about 7 years ago. This time we'll have to find a way to make it stronger...
Title: Re: A Simple Uniflow Engine
Post by: Ramon on October 06, 2020, 11:27:16 AM
Gary - my sincere sympathy for this dreadful situation. I can't even begin to imagine what you must be feeling right now especially as you have to rely on others to do what I'm sure you would rather be doing yourself. Hopefully your friends will do you proud.

I do hope it will not be as bad as it could be and that you will be able to get it all back to order without too much lasting damage.

The best of luck with it all

Regards - Tug
Title: Re: A Simple Uniflow Engine
Post by: Jo on October 06, 2020, 11:47:28 AM
 :o Nasty.

It looks like asbestos roofing sheets - they normally last forever  :thinking: You have less battens under the sheets to secure the sheets to than I would have expected. A few more wouldn't hurt. I assume that is the corner for the prevailing wind. Might be worth doubling up on the fixings if that is so. 

It should be an easy fix for a builder to do, won't take long  :ThumbsUp: (once they arrive   ::) )

Jo
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 06, 2020, 04:55:05 PM
@ Tug - thank you. I sense your understanding. Fingers crossed...

@ Jo - it's not asbestos even though it looks like it. It's 'fibro-ciment', a non-toxic asbestos lookalike. My place is in a green belt type location (a tiny hamlet with 200-year old houses) and the planning laws are super-strict. When we went to replace the old broken asbestos roof about 7 years ago, they specified fibro-ciment as it looks identical to asbestos. You know, traditional quaint rustic asbestos...

The stupidity of bureacracy ...  :facepalm:

We dutifully put up the fibro-ciment, but the first time it rained it began to drip water. The damn stuff isn't even waterproof!!! So I had to coat it with several layers of some grey waterproofing stuff from a big drum.

Crazy! And now this...

We live and learn. This time there will be more woodwork and a more secure structure. And planning be damned, I won't be using fibro-ciment. Some of that square-cut corrugated aluminium like the stuff Stuart (Propforward) has on his workshop will be better. Don't want to have all this nonsense again...

Thanks both.

gary
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on October 07, 2020, 12:14:25 PM
Hi Gary, we used to use a lot of that fibro cement, possibly still do.  But it was found quite early on that it fails in a brittle manner, and there were several serious accidents from people walking on the roof and falling through.  The building regs were modified to require a steel mesh under the sheet so at least no one would fall through if it breaks.  Existing roofs had to have a fixed notice prohibiting walking on the roof.  Try as I will, I canít work out just what physical principles are involved in making the wind obey the notice.  I suppose it doesnít walk on the roof.  Perhaps thatís it.  Of course there are no easy solutions when these things are discovered after the materials have been extensively used.

I believe the other disadvantage of the stuff is that it shatters explosively when exposed to fire, so not great for fire protection either, so I am not sure it was ever a great step forward.  But I wouldnít go back to the asbestos sheet either.  If the heritage people really insist on fibro material, perhaps install a layer of the usual metal, then a ď cosmeticĒ layer of fibro on top as a compromise.  Interesting that you use aluminium, we tend to use galvanised steel, though these days various high tech paint coatings are replacing the gal.

I hope that it can all be fixed soon.

MJM460


Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 07, 2020, 03:53:50 PM
Thanks MJM.

Ah, so the horrible stuff has the same name in English, apart from that first 'e' which is an 'i' in French.

Brittle is the word, and the fact that water seeps right through it is just ridiculous! And maybe in France the wind does actually walk on the roof. It certainly seems that it did, before bad-temperedly throwing a third of the roof across my neighbour's garden. Fortunately it didn't hit anyone with it.

I think I might use the metal (you are right - it's steel, not Ali - I just revisited Stuart's workshop log thread) with the rectangular grooved profile, but good idea MJM - it can always be covered with something else if absolutely necessary. There is also another kind of corrugated fibrous material that feels and looks like a kind of hard (but slightly flexible) felt. I don't know what it's called, but I have seen it in dark green and maroon colours. That might be a good option too...

Just for the record, the machines in the most exposed position are:

A vintage flat belt French drill press with its companion bench grinder    :(  :( :(
A Centec 2A milling machine  (which was?) in excellent condition           :(  :(  :(  :(  :(
A Myford ML10 lathe (which was?) in practically mint condition              :(  :(  :(  :(
A rare Burke No 0 milling machine which I had previously restored        :(  :(  :(
A not very special mitre saw                                                               :(
A couple of vintage countershafts                                                        :(
A Lister D Stationary Engine                                                               :( :(

Also various bits of tooling (hopefully protected in the chests of drawers that they are in) and three old French anvils (which will probably survive the deluge).

But there is other gear in other parts of the shop which is also at risk from diagonal rain...

Thanks for listening, anyone who reads this. I feel better now. A bit...
Title: Re: A Simple Uniflow Engine
Post by: Bearcar1 on October 08, 2020, 04:12:48 AM
 :o :o :'( :'( :shrug:


Man, that would almost be worth having someone cut the door open, release the lock and enter. weld a patch back over the hole after covering your exquisite machines.


BC1
Jim
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 08, 2020, 07:59:00 AM
Hi Jim -

You are right, for sure. Suffice to say though that there are nuanced reasons in the area of 'village politics' which weigh against that. It's a fine balance, but given the machines will have already got wet and - hopefully - the keys will have arrived with my neighbour within a few more days, I have decided just to suffer it until they arrive. Also, when I last spoke to him the forecast was for rain and wind all this week, so he probably wouldn't have been able to cover the machines anyway.

I'm hoping that my builder friend will be able to go up in the not too distant future...

Thank you for your  interest!

gary
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 09, 2020, 11:40:43 PM
A bit of progress.

My neighbour in France has received the workshop keys. Very quick delivery by post. Kudos to the Post Office! He is going in to check out the state of play tomorrow morning and make a start on basic protection of the machines.

The weather there has picked up with a lovely sunny day today and a good forecast for tomorrow, so hopefully the machines will dry out, at least to some degree... it's the thought of water getting into all these bearings and slideways by capillary action that bothers me, but as my ever-optimistic other half reminds me, they are well lubricated.

My neighbour has been speaking to some other people we know who may be able to repair (or replace, hopefully) the roof sooner than my friend from down South would be able to...

Fingers crossed...

:insane:



Title: Re: A Simple Uniflow Engine
Post by: Bearcar1 on October 10, 2020, 04:14:33 PM
 :NotWorthy: Gary, my prayers are with you my friend.... damn, the thought of water damage to those machines makes me sick to death.    Best of luck and I hope all will be well.


BC1
Jim
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 11, 2020, 10:47:42 AM
Thank you Jim - that's very kind of you.

I know... it's a horrible thought and it will be on my mind until it's fixed and I can get over there to check them out. My neighbour has now been in and he sent more photos. The Myford ML10 seems to be the worst affected because it sits in the direction of the prevailing wind (which is Westerly, blowing in from the Atlantic and full of rain at this time of year). The lathe is wet, and now has surface rust on the slideways and chuck and goodness knows where else. I have asked my neighbour to go out and get loads of absorbent material such as rolls of paper towelling, a bunch of cans of WD-40 and plenty of plastic sheeting or tarpaulin. I am now waiting for an update from him.

Meanwhile, my builder friend (the original one) has committed to definitely going up to put on a new roof in the last week of this month, after his grandson is born. We are going to use corrugated iron - either the traditional kind (which would be galvanised) or the more modern box section type (pre-painted grey) - we haven't decided yet, but definitely NOT the dreaded 'fibro-ciment'! He is going to add more timber to the underlying structure, add some tie-down straps and use more fixings, and build a small parapet at the top of the wall to protect the edge of the roof from that prevailing wind (which was as high as 150 km/h at the time the roof section blew off). Hopefully that should do it! And hopefully my neigbbour's intervention will at least prevent things from getting worse until the new roof is on and the tarps can be taken off the machines, giving them a chance to dry out.

Cheers Jim, and the others of you who are being so supportive over this.

  :LittleAngel: :LittleAngel: :LittleAngel:
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on October 11, 2020, 01:21:58 PM
Hi Gary, itís good to hear that things are starting to move on the recovery front. 

With any luck, that visible rust will be superficial and relatively easy to polish off when you are able to get back.  The electrics are potentially more troublesome, but I will leave it to others to make more informed recommendations for what to think about there.  First thing is to get a roof on.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 11, 2020, 05:57:50 PM
Yes the electrics could well be an issue.  I'll probably not switch on any of the ones that have got wet until they have sat under the new roof for the whole (hopefully hot) Summer next year to give them a chance to dry out. If I do have to replace any motors it will be with 3-phase or treadmill type units with variable speed control, for sure.

Thank you...
Title: Re: A Simple Uniflow Engine
Post by: propforward on October 11, 2020, 08:13:29 PM
I am very glad to hear the keys got to your neighbour in a timely fashion, and I truly hope there is no damage.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 11, 2020, 11:04:05 PM
Many thanks for your supportive thoughts, Stuart.

Progress on the machine rescue front! My neighbour has been busy with WD-40 and the kind of plastic that is used to cover silage.

First, the Myford ML10:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878334.jpg)

Next, a cabinet containing various components (including a lovely old Brit indexing head with tailstock) and with a couple of countershafts on top:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878332.jpg)

And a vintage French drill press (L), a Centec 2A mill (C) and - half off camera -  a vintage American horizontal mill (R):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878333.jpg)

There's a Lister D stationary engine in the foreground of that one that he hasn't covered yet but I have asked him to. The other machines are all in dry areas I think. All in all, that will suffice until my builder friend arrives in a couple of weeks to put on a new roof.

Now, on with other things...

I have been using two milling vices - one is a tilt and swivel job that is really too big for the small mill I have here at home. The other is a nice old British precision vice which - alas - I overtightened and damaged last week (I know... what a week...). It's fixable but I don't want to put time into it right now, so these two vices will go into my 'take to France' collection and find homes on the soon-to-be-dry machines I have over there. They have been replaced in my workshop here at home by these:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878342.jpg)

The little beauty on the left can be taken off its tilt and swivel mount and fixed straight on the milling table if desired. The t-slot table can be fixed to the mount. Very nice. The one on the right is quite hefty and it has 'angle lock clamping' to prevent jaw lift. It can also be used vertically as well as horizontally which will be very handy for e.g. slitting saw work. A bit of retail therapy to ease my mind following the roof disaster...

So, finally back to the engine with some significant progress today. The crosshead, connecting rod and big end are finished, bar a bit of final polishing and fettling:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878345.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878344.jpg)

The threaded sections of the bronze connecting rod show significant runout which is far greater than would be caused by normal 3-jaw chuck inaccuracy. It may be that the forces involved in cutting the threads with a die upset them. However, as the motion is linear I'm hoping to get away with it. The two washers are included as shims because I was inaccurate with the length of the non-threaded section of the connecting rod. I can play with this as I go along and if it still seems that they are needed I can either replace them with something that looks better or tidy them up. When it's all finalized, some Loctite threadlocker will be applied. All in all, I'm happy with it. Sure, it's chunky, but it will probably be a fast engine and my aim is to run it on a fairly large boiler.

Finally, the parts so far roughly assembled for demo purposes:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878347.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878341.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878346.jpg)

As I've said a number of times previously, my main concern at this point is whether or not those flywheels are big enough. Time will tell, but meanwhile next up (after a shop clean and tidy-up) is the frame. Going 3D at last...! 

 :cartwheel:




Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 12, 2020, 09:01:39 PM
My neighbour has been doing more work today, wrapping more items in plastic sheeting. This includes the Lister engine I mentioned yesterday.

This picture truly conveys how exposed the machines were:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878407.jpg)

Good temporary remedial work, though, and I'm counting down now until my friend can put a new roof on the shop...
Title: Re: A Simple Uniflow Engine
Post by: propforward on October 12, 2020, 09:02:59 PM
Phew - it is great to have great neighbours!

Loving the engine work Gary - really superb finishes on those parts, they look amazing!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 12, 2020, 09:04:34 PM
You bet!

And good friends capable of re-roofing a workshop...

 :) :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 12, 2020, 09:05:57 PM

Loving the engine work Gary - really superb finishes on those parts, they look amazing!

Thanks Stuart - very kind of you.

I must admit it cheered me up to be able to assemble those parts like that.
Title: Re: A Simple Uniflow Engine
Post by: Johnmcc69 on October 12, 2020, 09:43:40 PM
Nice work Gary!
 Sorry to hear about the shop, at least maybe it was taken care of before more bad weather hits.

 Enjoying the build!  :popcorn:

 John
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 12, 2020, 09:59:44 PM
Thank you John.

There will inevitably be a fair bit of remedial work to do, but hopefully thanks to early intervention nothing will be irretrievably ruined. And - all being well - my shop will have a smart new roof which will be stronger than the one that blew off.

Glad you are enjoying the build efforts of a beginner like me.

 :ThumbsUp: gary
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on October 13, 2020, 12:07:29 PM
Hi Gary, good to see some protection in place.  At least no more should be able to get in now.

Good to see more progress on the engine.  I see what you mean about the flywheel appearance now they are lined up with the cylinder and control.  I am still inclined to see if it works, but it wonít be too difficult to make a separate rim and attach it if necessary.  A steel or better still, stainless steel rim, will make a nice two tone appearance. 

MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 13, 2020, 12:41:17 PM
Yes indeed, and bring on the new roof!

Agreed on the flywheels. I'll try running the engine with them as they are at first. I'll be starting on the frame very soon and will make sure that it's designed so that there's enough space around the flywheels to add steel rims if needs be. There's a small machine shop locally where the scrap bin often contains nice chunky steel discs (offcuts of large diameter bar) which would fit the bill nicely when bored to fit.

And yes - the two different metals would look good together.

We shall see if they are needed though ...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 14, 2020, 10:18:10 PM
Way back on page 5 of this thread there was some conversation about surface treatments for iron and steel. John suggested that I try gun blue, so I ordered some at the time. It didn't arrive, I got a refund, and ordered some more last week. Better luck this time, so last night I tried it out on some spare bits of cast iron and a piece of silver steel:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878498.jpg)

That was without much effort at all - just a rough and ready degrease with some meths and then a quick application of the blue before rinsing off under the tap and finishing off with a wipe of oil. Very effective and easy to use, and with a little bit more work would bring up an amazing finish. However, I don't think it's the right look for this engine. I was hoping a light smear of it might bring a subtle blue hue to the metal, but it's grey through to black all the way, which to my eye would look a bit too severe for the cylinder, big end and crosshead of this engine. Instead, I'll do as Jason suggested, just applying a light smear of oil and letting the cast iron speak for itself. I'm glad I now know about the gun blue, though, and I do think it could look good for smaller accents such as screw heads, etc. And on other builds I know it can look great on major components too. A useful thing to have in the shop, I reckon.

No doubt many of you will know this, but for those who don't it appears to only work on ferrous metals. I tried it on aluminium and brass with zero effect.

To progress this engine further I'll need to at least make a start on the frame, and according to the idea I have in mind, the frame will require a base to be functional. The main base will be made from two massive pieces of oak that were originally intended for another (non-steam related) project that got sidelined. Joined together and shaped somewhat, these will create a very solid base which will hopefully create significant stability for the engine, which by all accounts could turn out to be something of a bucking bronco. Attached to this will be the two symmetrical sides of the frame made from the 5mm aluminium plate which you can see here. A piece of this plate will also be fixed to the wooden base horizontally under the engine. The two sides will be joined by a number of cross pieces which will act as bracing struts to give the whole structure rigidity.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878497.jpg)

That's the plan. Still quite a lot of work ahead...
Title: Re: A Simple Uniflow Engine
Post by: crueby on October 14, 2020, 11:13:34 PM
A few years ago I tried a few different blueing compounds on a variety of steels, worked good on some alloys, not on others. Tough to predict.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 14, 2020, 11:21:22 PM
What kind of alloys Chris?
Title: Re: A Simple Uniflow Engine
Post by: crueby on October 14, 2020, 11:25:46 PM
What kind of alloys Chris?
Tried it on cold rolled, drill rod, couple stainless, forget the details. Its back on a thread. Somewhere. Bottom line, needs experimenting like you did, as I recall there was no predictable results.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 14, 2020, 11:29:45 PM
Ah ok.

I found that the silver steel responded better than the cast iron did. Very dark, even colour with almost zero effort.

Certainly warrants further exploration in due course though.
Title: Re: A Simple Uniflow Engine
Post by: Kim on October 15, 2020, 05:52:57 AM
There are various chemical blackening agents designed for brass also.  I've used them on other projects.  They also have varying results.  I found that I got the most consistent results by doing a thorough fairly careful process (a good cleaning of washing, then rinsing in acetone, allowing them to dry thoroughly (without touching), then submerged in thinned brass black for a specific amount of time, followed quickly by a gentle water rinse and allowed to dry).  With that process I got pretty consistent results on the brass.  I tried three different types of brass black to see what I liked.  Don't remember exactly what I ended up using, but if you're ever interested I could look it up.

Anyway, you're not trying to blacken brass, but since you tried your stuff on brass and found it didn't work, I wanted to let you know that they are available!

Kim
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 15, 2020, 11:03:00 PM
Hi Kim -

Thank you for this. I probably won't be looking to blacken brass in this build, but it's always a possibility in future projects. Now that I know that it exists, it might get my mind ticking over. I'll come back to you for advice on which one was best if and when I decide to try it.

All good info, for me and perhaps others looking in too!

I'd be very interested to know if there are any compounds out there that will impart colours other than black to metals (other than plating or anodising I mean).

I'd love to get into anodising aluminium, but I don't have room for the gear. Mind you, lack of space has never stopped me before...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 18, 2020, 11:19:20 PM
Made a start on the base today. The two big pieces of oak were joined together using jointing biscuits and exterior grade wood glue:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878732.jpg)

I love the smell of oak when it's being worked.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878731.jpg)

In the following photo the glue hadn't yet been applied - this was a trial fit to make sure the biscuits lined up:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878734.jpg)

It has now been glued up and laid somewhere flat indoors. I'll release the clamps tomorrow. The pieces of oak are the shape they are because they were initially intended for another project, for which they were mitred. The pointed ends will either be cut square or shaped in due course, though it may be useful to keep a bit of extra length so that accessories can be mounted on them.

I then began marking out the blanks for the sides of the engine frame on a piece of 5mm thick aluminium plate:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/878733.jpg)

The sides will be made from the narrow rectangle at each end of the sheet of plate. The sheet is very precisely cut as purchased, so the existing edges will be good as reference lines for machining. A lot of the machining will be on the two sides at the same time, bolted together.

There will be more than enough plate left in that middle section to make a piece which will be fixed flat to the oak base under the engine, like a floor.

It was late afternoon by this time so I decided to leave setting up the saw to cut the plate for another day. This evening, I did a thorough clean-up of the mill to get all the cast iron swarf off it. Pleased to say it scrubbed up nicely. The lathe will be getting the same treatment, probably tomorrow.

Title: Re: A Simple Uniflow Engine
Post by: MJM460 on October 19, 2020, 12:20:51 AM
Wow, Gary, that ought to be enough biscuits! 

A pity. That so much of the oak will be hidden, but it should definitely be heavy enough to hold the engine down.

Good to see the progress.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 19, 2020, 09:30:30 AM
Ha, yes... as I have previously admitted I do tend to somewhat over-engineer things. That said, these are big heavy pieces of wood, so better safe than sorry.

Agree that it's a shame to cover so much of the wood, but I'd rather any oil and water fall on to a metal surface. Also, the wooden base will be quite a bit wider than the frame so there will still be a fair amount of oak visible.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 28, 2020, 11:37:24 PM
Misery.

My builder friend and his colleague were due to go and make a start on replacing my French workshop roof on Sunday. However, France has just gone into another national lockdown, so it's not going to happen.

I won't whinge, because this is affecting millions of people in ways much worse than it's affecting me.

My neighbour will do what he can with plastic sheets, etc., but I dread to think what state these machines will be getting into as it has done nothing but rain there for the past two weeks.

No progress on the engine (and have fallen behind with other people's threads that I'm following) as I have been redecorating our bathroom all week...

Sometimes this is how it goes...

 ::)
Title: Re: A Simple Uniflow Engine
Post by: propforward on October 29, 2020, 12:45:41 AM
Gary,

I heard that on the news today. I'm so sorry. However, I think the tarps will do a lot for you. Fingers crossed.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on October 29, 2020, 10:23:49 AM
Many thanks Stuart.

I have just learned that essential trades (including building) are likely to be allowed to continue, so it may still be on.

More later...
Title: Re: A Simple Uniflow Engine
Post by: propforward on November 01, 2020, 12:27:23 PM
Thatís great news. Any further word on that? I see the UK is heading into lockdown again.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 01, 2020, 12:30:29 PM
Yay!  :cartwheel:

My good friend and his helper are driving up to my place in France tomorrow to put a new roof on the workshop. France is in lockdown, but builders can work as it's an essential trade.

We have decided to go for a strengthened roof structure (more wood work plus tie-down straps), 'corrugated iron' instead of the dreaded fibro-ciment and a raised blockwork parapet to deflect the wind.

I'm hoping he will send me a few pics of the work in progress and if he does I'll post a couple here.

Meanwhile, here at home, I have finished redecorating our bathroom so should be able to get back to the engine soon, or at least give my shop a much-needed cleanup.

Things are looking up...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 01, 2020, 12:31:30 PM
Thatís great news. Any further word on that? I see the UK is heading into lockdown again.

Stuart - yes - our posts crossed.

Yep, UK locking down again...

Title: Re: A Simple Uniflow Engine
Post by: propforward on November 01, 2020, 12:43:32 PM
Well thatís good news on the building front anyway! Glad to hear that at least.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 01, 2020, 12:50:16 PM
Cheers Stuart!

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 04, 2020, 10:27:04 PM
O Glorious Day!

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/880114.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/880115.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/880116.jpg)

And it looks like the insurance are going to pay...

 :)
Title: Re: A Simple Uniflow Engine
Post by: propforward on November 04, 2020, 10:39:51 PM
Wonderful news Gary! So glad to see that taken care of. Even better that the insurance will do what they are paid to do. Nice one!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 04, 2020, 10:51:24 PM
Thanks Stuart. Very kind of you!

It was a happy moment when these arrived in my inbox.

Title: Re: A Simple Uniflow Engine
Post by: john mills on November 04, 2020, 11:36:28 PM
thats great to see the work happening  it is always sad to see machinery in the weather .i would like to check wats under the plastic   see the wd40 is not drying out and moister forming .good luck in recovery of the machines .
iI worked in a factory which had an explosion which lifted the roof .i was not on that shift when it happened
but the resultant fire made a mess but a recovery firm recovered the machinery in the end they said it was not bad
as they often get.but it was amazing what could be done.good luck with yours hopefully not too much .
  John
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 05, 2020, 01:14:39 PM
Hi John - thanks for your comments.

My friends will take the plastic off the machines as soon as the new roof is finished (which it may be by now). The idea is to dry off any remaining visible water, let them dry in the air for a while, then spray them liberally with WD-40. That's the best that we can realistically do until I can get over there (hopefully next year), at which point I'll have some cleanup work to do.

I'm a bit worried about water that may have crept into bearings and slideways by capillary action, but fingers crossed these will already have some protection from their existing oil and grease, and perhaps some WD will also help to drive any water out.

I bet you are glad you weren't on shift when the explosion happened! I hope no-one was seriously hurt, though by the sounds of it that may be a bit optimistic.

Good that the machines were salvageable though...

Title: Re: A Simple Uniflow Engine
Post by: propforward on November 05, 2020, 01:53:30 PM
Good approach Gary. I would be concerned about that capillary action too - but WD40 is REALLY good stuff, and its very specific purpose in life is water displacement - hence WD of course, so I reckon it will also capillary itself into those ways and kick the water out of there. I think you're doing all you can reasonably do, and I reckon it will go a long way to saving those machines, and make getting them up and running a matter of clean up and fettle, rather than restoration. Great that you have good friends and neighbours, can't beat that.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 05, 2020, 08:46:35 PM
Cheers Stuart.

Yes, WD-40 is 'Hydrofuge', and I'm hopeful that it will work as you say.I didn't know that's what the 'WD' stood for though!

Yeah, they're doing a grand job it would seem. Feels reassuring!
Title: Re: A Simple Uniflow Engine
Post by: propforward on November 05, 2020, 10:20:37 PM
Yes I understand it stands for "Water Displacement - formula number 40". I guess 1 thru 39 didn't amount to much. I should look into that and see if it's an urban myth or something.
Title: Re: A Simple Uniflow Engine
Post by: john mills on November 05, 2020, 10:29:18 PM
Hi Gary

when the explosion happened they where  very lucky just people had moved at that time from and of the critical places  apiece of plaster board was stuck between the bench top and the steel frame just behind where the operator would stand at the lathe i operated the day shift person also was not there at that time only miner injuries to 2 people  could of been very different .as for the machines they were recovered .the recovery people told me they often recover machines be cause it was quicker than waiting for new replace ments i would think it would have been a good opportunity to replace old machines with new ones .   
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 06, 2020, 09:27:08 AM
I guess 1 thru 39 didn't amount to much. I should look into that and see if it's an urban myth or something.

I like it!  :Lol:

My only doubt is that I have heard that originally it's a German product. Don't know if that's true or not, and even if it is it may still have been named in English I guess...

@ John - glad to hear no-one was seriously hurt. One hears enough horror stories as it is these days.

Cheers guys.

 :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 07, 2020, 11:55:48 PM
Great progress, and quick too:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/880410.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/880411.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/880412.jpg)

No doubt the devil will be in the detail (as I'll discover when I can eventually go back to France), but from the photo here everything looks much better than I dared hope...

Back to the engine again soon, after this major diversion...
Title: Re: A Simple Uniflow Engine
Post by: Jo on November 08, 2020, 08:28:41 AM
Pleased to see the roof back on Gary  :ThumbsUp:

Now it can dry out and hopefully any surface rust can quickly be cleaned off  :)

Jo
Title: Re: A Simple Uniflow Engine
Post by: Admiral_dk on November 08, 2020, 09:50:39 AM
What a relief it must be for you to see those pictures of a nice roof on your workshop again  :LittleAngel:

I bet you will still be somewhat anxious when you finally get to see them in the flesh again, and start inspecting them for any damage ... but it should much better than without a roof ....

Best wishes

Per
Title: Re: A Simple Uniflow Engine
Post by: propforward on November 08, 2020, 03:31:40 PM
Much better! Looks great Gary, pleased to see that progress! Very nice workshop, too.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 08, 2020, 09:45:15 PM
Jo, Per, Stuart -

Thank you! Your support is much appreciated.

From this distance it all looks pretty much like it was before. It is of course very possible that there will be some damage at a more detailed level, and yes inevitably there will be some surface rust.

But I spoke to my builder friend on the phone today (he is back at home now) and he said that things aren't looking too bad and that he liberally sprayed all of the machines with WD-40 and something else similar, so they will now sit there for a few months like that, which - as you note, Per, is way better than them sitting exposed to rain! And the workshop now has a much better roof than it did before.

Stuart - glad you like my France workshop. It's pretty basic, rough and ready but it has soul! All I have done in there so far is work on machine restoration, which is something I enjoy. If one day I spend more time over there, the remit may broaden.


Now, at last, back to the engine:

No spectacular progress today but it was good to reconnect. The oak base was made in two halves which were fixed together with exterior grade wood glue and lots of jointing biscuits and clamped tightly while the glue set. Despite (or more likely because of) me having tried to make the thing bombproof, it ended up with something of a misalignment in that looked at from the end the two pieces would be seen as a very shallow v shape rather than a straight line. One one face of the assembly the pieces appear to meet nicely, but on the other (which for obvious reasons I have decided is the bottom) there is a narrow gap. This is annoying, but it's not a disaster as the faces can be planed flat, and it's plenty thick enough. This picture shows the underside as I 'm just about to start with the power planer:

(http://www.model-engineer.co.uk/sites/7/images/member_albums/173350/880521.jpg)

And this one shows the top of the base after an initial rough planing:

(http://www.model-engineer.co.uk/sites/7/images/member_albums/173350/880522.jpg)

Ideally this would be run through a thicknesser to make it flat and even. I have one as an attachment to my wood lathe but it's not big enough for this job. I'm sure that a local joinery would do it for me but I like to do things myself as far as possible so the next step will involve a hand plane and a sander, with repeated use of the straight edge  to check for high spots.

As I've mentioned somewhere above, the base will not end up this shape - it's only like this because the pieces were left over from a sidelined project.
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on November 09, 2020, 09:47:45 AM
Hi Gary, good to see that roof on again already.  Looks like it will be even better than brand new.

Now that the roof is good and the plastic covers off the machines, the WD40 will be evaporating clean away, hopefully along with the water.  (After all displacing it does not make it magically disappear.  I really donít know what happens to it in this situation.)    I would be thinking about a follow up protective spray.  Something that leaves a protective coating this time.  Here, suitable products would be CRC, which stands for corrosion resistant coating, or Innox.  I donít know how widespread these brands are, but there will be similar products available everywhere.  Of course this would depend on the help of your willing neighbour.

Other forum members might have better ideas.  And just having the roof repaired is excellent progress towards having it all in operation again.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 09, 2020, 11:45:11 PM
Hi MJM -

Yes, it looks to me much better than the roof it has replaced, even before it was broken.

Good suggestion re the protective sprays - I'll give it some time for the machines to dry out, then look into it.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 12, 2020, 10:23:35 PM
Seem to have been bogged down in lots of other stuff recently, with not much progress on the engine.

Four of these arrived today - a small step but better than nothing. Feet for the underside of the oak base, with threaded inserts to screw them into:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/880855.jpg)

They are quite substantial (the thread on the stud is M10), and I love the orange rubber pads!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 15, 2020, 10:22:09 PM
Squaring off the ends of two lengths of 40mm aluminium angle. These will be fixed to the oak base, one on each side of - and parallel to - the engine. Let's call them frame mounting bars. The two main sides of the engine frame will be fixed to the vertical face of these bars.

Not very exciting stuff, this, so apologies. However, I was just glad to get into the workshop this evening after being bogged down with fireplace problems, camper van problems, dishwasher problems, cracked bathroom floor tile problems, and writing a work-related article that I wish I hadn't agreed to. So happy to post a plain old shot of the mill set up to tidy up the ends of some unexciting aluminium angle. At least it shows my new vice, this being the first time I have used it:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/881146.jpg)

I thought I'd also let you see these in their unused state:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/881148.jpg)

They were cheap as chips on Amazon, so whether they will last longer than five minutes remains to be seen. But at the price it's not much of a risk. I like the fact that I'll be able to see how much oil is in them. They also each come with two interchangeable nozzles, and the pump mechanism does feel quite sturdy. Time will tell...
Title: Re: A Simple Uniflow Engine
Post by: propforward on November 16, 2020, 12:28:12 AM
Nice. A bit of workshop time is always good medicine to get the head straight around that "other stuff". One of the reasons I like model engineering, is because it does actually take some brain power, so good for getting your mind off every day things for a bit.

That is an immaculate mill! Always good to see a well looked after shoppe.

That's a good looking vice. I'm looking forward to seeing all manner of set ups with it.  :ThumbsUp: :ThumbsUp: :ThumbsUp: :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 16, 2020, 11:29:32 PM
Stuart - agreed, absolutely. I find that I get very frustrated when all of the other stuff (which I've had plenty of recently!) keeps me away from the shop. Another thing happened today... but no. Enough of that!

I wish I could tell you that my mill is always that clean though.

Normally it's anything but...

 ::)
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 22, 2020, 11:22:56 PM
Assembling flatpack shelving units, more work on the campervan, earning a living... oh - and drilling a few holes:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/881802.jpg)

These are drilled in the frame mounting bars so that they can be fixed to the oak base with wood screws. Modest progress, but now I can start on the two sides of the frame, so I'm at a significant stage of the build...
Title: Re: A Simple Uniflow Engine
Post by: propforward on November 22, 2020, 11:34:29 PM
Lovely work Gary. Good finishes - always enjoy seeing your posts.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 23, 2020, 08:07:42 AM
Cheers Stuart.

Hoping to make a bit of progress next weekend...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 24, 2020, 10:14:15 PM
Now... a template for the sides of the frame, cut out of thick paper:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/881909.jpg)

The two sides of the frame will be cut to this shape from 6mm aluminium plate. Two pieces will be bolted together to keep them both the same shape as they are cut with saws and finished on the large belt sanding attachment on my woodturning lathe. No CNC here! (maybe one day...). The aim is to end up with a simple but elegant curve on each side of the engine, forming the frame. These will be fixed to the frame mounting bars, which in turn will be fixed to the oak base. Holes will be drilled for the two main bronze bearings. These will be high enough so that I can increase the diameter of the flywheels if I need to for the engine to run (in the photo both the flywheels and the cylinder are temporarily shimmed with wood, for height). The whole structure will be braced by cross members made from round aluminium bar running between the two sides of the frame. Also, two shorter cross members will tie each frame side to the cylinder, which will be supported at centre height by an aluminium block. The roughly scribbled circles on the paper represent the fact that 'decorative' holes will be cut into the frame sides wherever they will look good and not interfere with the 'functional' holes for the bearings and cross members. A rectangular aluminium plate will be installed under the whole length of the engine so that oil and water will not drip on to the oak (which nevertheless will be treated with several coats of Danish oil).

That's the plan, anyway, subject to any changes of direction that may occur as I go.

Hope to start shaping these frame sides at the weekend.

And it looks like the insurance company are going to fork out for my French workshop roof...  :)
Title: Re: A Simple Uniflow Engine
Post by: propforward on November 24, 2020, 10:29:22 PM
Good news all round Gary.

Like your idea for the frame - should set the engine off nicely.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 24, 2020, 10:30:29 PM
Thanks Stuart.

Still a long way to go though...  ;)
Title: Re: A Simple Uniflow Engine
Post by: propforward on November 24, 2020, 10:38:01 PM
Always!  :ROFL:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 26, 2020, 10:32:23 PM
Onwards and upwards.

Cutting the blanks for the two sides of the frame from 6mm aluminium plate with my Evolution Rage circular saw:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882041.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882040.jpg)

First time in ages that I've used this saw. I'd forgotten how good it is. It sliced through the plate like a knife through butter:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882043.jpg)

The paper template was used to mark out the rough shape of the frame on one of the blanks:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882042.jpg)

The two blanks were clamped together, drilled at the four corners and fixed together with M6 cap head screws so that they can be machined together to make the two frame sides identical:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882044.jpg)

The only critical edge at this point for alignment of the two pieces of plate is the bottom one, facing the camera. I used the surface plate to align the blanks before clamping them together and on running my thumbnail across the two thicknesses it felt like just one piece of metal.

The next stage is drilling holes along the bottom of the blanks so that they can be fixed to the frame mounting bars. The four marks along the edge roughly indicate the positions of these holes. At this stage the only purpose of having the curved shape of the finished frame marked on the blank is to act as a guide for positioning these and other holes. Cutting the frame to shape is still several steps away...
Title: Re: A Simple Uniflow Engine
Post by: propforward on November 26, 2020, 11:01:34 PM
Very cool. That saw made short work of those plates.
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on November 27, 2020, 01:45:19 AM
Hi Gary, good to see you able to get back on the job.  Nice to see some progress again.

I like your unique take on the side frame plates.  Did you use a special blade on that saw for the aluminium?  Or is it a whole special saw?  Either way, it would have been noisy!

MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 27, 2020, 08:05:19 AM
Thanks guys.

The Evolution Rage blade easily cuts steel, aluminium, wood, wood with 6 inch (or even 9 inch 8) ) nails through it, plastic.... etc.

Amazingly good saws and not too expensive for what they are. Interestingly, the blade doesn't get hot as it cuts.

They make other types of saws too - I also have their smallest mitre saw which I have used and abused for several years now.

So yes, MJM - it's a whole special saw. But you are right - cutting the plate was a noisy affair!

 
Title: Re: A Simple Uniflow Engine
Post by: Admiral_dk on November 27, 2020, 11:23:57 AM
I have the bigger version - nessesary when building my Sister and Brother in Laws big hal 39x12x11 meters from steel profiles I welded together - and the Manufactor warns that the original blade MUST only cut steel and iron. They do sell another special blade for cutting Aluminium.
It cuts a big steel profile in a few seconds and yes it's rather noisy, but quick and the swarf is cool compared to all other methods

For daily use I wish that I had the smaller one you got, as it only a third of the weight => I rarely use it nowadays ....
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 27, 2020, 12:42:48 PM
Per - thanks for looking in.

The one that I have is advertised as being suitable for steel, wood, aluminium... and it cuts steel plate nicely too.

Different blade from yours maybe?
Title: Re: A Simple Uniflow Engine
Post by: Admiral_dk on November 27, 2020, 07:25:02 PM
They might have found a solution to improve how many different materials they support with a single blade - but since I expects many more years of use on the current one, I'm not looking to buy another yet (specially considered the price).
When I bought mine they strongly warned about aluminium would destroy the blade - but it's certainly the same brand and yours looks like a miniature version of mine.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 29, 2020, 11:18:57 PM
Per - yes, I guess they must have developed the blade over time.

After yet another weekend of domestic and automotive obligations (it has been a ridiculous few weeks!), I managed to squeeze in a little bit of shop time, as evidenced by this moody, atmospheric late-night still life of some aluminium, an automatic centre punch and a lens to peer through in the name of accuracy:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882412.jpg)

Sometimes I find it easier to use traditional manual marking out methods than to spend ages clocking in a workpiece (in this case just to drill four holes). The holes in question are along the bottom of the frame side plates, and the two plates were left fixed together for the drilling op, so it was eight holes for the price of four really. I used a wiggler in the mill to pick up the centre punch marks. No pictures of the drilled plates because all the photos tonight (except for the above) were blurry for some reason.

The next job will be to transfer the holes in the plates to the vertical side of each frame mounting bar, which will be a significant step towards building the main structure of the frame.
Title: Re: A Simple Uniflow Engine
Post by: propforward on November 29, 2020, 11:50:17 PM
Frustrating when you can only get small amounts of shop time in - but hopefully you can get back for extended sessions soon!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 29, 2020, 11:58:40 PM
 Cheers Stuart.

:ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 30, 2020, 11:40:54 PM
The two frame sides and the two frame mounting bars were all clamped together:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882475.jpg)

Remember that the uneven top edges of the plates don't matter - they will be trimmed off later. The bottom edges are nicely aligned, though, and the two screws at the top corners keep them that way.

The clamped assembly was then held in the milling vice ready for drilling the mounting holes in the support bars:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882474.jpg)

Since the side  plates were already drilled it was just a matter of spotting through the holes in them and drilling down through the two support bars. Because of this the holes in all four parts are aligned.

The frame sides were temporarily fixed to the support bars using stainless steel M6 cap head screws. This type of screw appeals to me for a contemporary style of engine, but I'll use shorter ones for the finished job:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882477.jpg)

Finally, a shot of the frames set up on either side of the main engine components:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882476.jpg)

This engine will be quite wide, but it will be slightly narrower than it looks here because the main bearings will be turned down a bit. Also, the frame sides will be reduced in size, shaped, and drilled with decorative holes. Although this evening's offering is not particularly glamorous, it's a significant stage  of the build because now that the sides can be attached to a temporary base, the next stage will be to drill the holes in the frame for the main bearings, so an initial mockup and perhaps an initial test on air are now on the horizon.

Title: Re: A Simple Uniflow Engine
Post by: crueby on November 30, 2020, 11:44:10 PM
Coming together well!   :popcorn: :popcorn: :popcorn:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on November 30, 2020, 11:48:00 PM
Thank you Chris.

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 01, 2020, 11:34:32 PM
Drilled a couple more holes tonight. The ones for the main bearings.

Getting ready:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882551.jpg)

I wanted to drill the holes 19.5mm and finish them with a reamer. However, my 20mm reamer has a MT2 shank, this mill is R8 and I don't have a suitable adaptor sleeve, so I just swapped to a 20mm drill as the last of four (including the centre drill) progressively increasing in size. The oil can contains some new (to me) cutting fluid called 'Molyslip'. It's a nice dark green colour and it seems to cut really smoothly. It has a nice viscosity to it so you can squirt it on to a spinning cutter and some of it sticks. Again the frame sides were bolted together and both were drilled in one operation.

The idea is that the bearing goes through the hole and the collar slips on to it from the other side of the plate, after which the components will be fixed together by a bolt circle that passes through the plate.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882550.jpg)

After drilling the 20mm holes tonight I discovered that the bearings are a fraction too big to go through them. Ideally I would have bored the holes a tiny bit wider at the same setting of the mill, but my boring head is also MT2, so same problem as above (I really need to get that sorted out!). Instead, I'll just turn the bearings down in the lathe. Not ideal because it risks a rattly fit between the bearings and the collars (and consequent inaccuracy in the crankshaft alignment). However, the amount that needs to be removed from the bearings is very small so as long as I'm careful it should all stay centred ok.

I couldn't resist a mockup showing the progress to date, despite the fact that the crankshaft is just sitting loosely in the holes without bearings:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882553.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882552.jpg)

To be honest the whole thing is riding a bit high in its frame at this point, but that was deliberate as I don't know yet whether or not I'll have to increase the diameter of these flywheels.

One step at a time...
Title: Re: A Simple Uniflow Engine
Post by: propforward on December 02, 2020, 12:34:09 AM
Good progress Gary! Like you say, one step at a time. Love the test assembly. Itís going to be a super engine.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 02, 2020, 08:56:41 AM
Cheers Stuart. It will be very interesting to see how it responds to an initial test. Not so far away now...

I'm fully prepared for the possibility that it may not run due to the flywheels being on the small side. If that happens I'll just have to increase their size.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 06, 2020, 10:49:28 PM
Drilling a 5-hole bolt circle in the bearing flanges using the small rotary table with dividing plate (there's a bit of a '5' theme to this engine):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882924.jpg)

Drilling a matching bolt circle in the bearing collars. These are blind holes which will be tapped M3:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882923.jpg)

Bearings and collars drilled. Still to be deburred, which I'll do once the collars have been tapped:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882926.jpg)

The holes in the collars still need to be tapped, and clearance holes still need to be drilled in the frame for the screws to pass through and join the bearings to the collars. However, I thought I'd give it another trial assembly to make an initial assessment of the bearings:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882925.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/882927.jpg)

All seems ok as far as I can ascertain at this stage. Crankshaft looks true and turns smoothly, cylinder 'breathing' as the piston pushes and pulls at it...

 :)

Title: Re: A Simple Uniflow Engine
Post by: crueby on December 06, 2020, 10:53:11 PM
 :popcorn: :popcorn: :popcorn: :popcorn: :popcorn:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 06, 2020, 10:56:42 PM
Cheers Chris.

 :ThumbsUp: :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: propforward on December 06, 2020, 11:35:12 PM
Ah excellent! Nice work. We both have crank success today!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 07, 2020, 10:53:03 AM
Yes indeed!

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 08, 2020, 10:35:22 PM
Tapping the holes in the bronze bearing collars M3:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883084.jpg)

The bearing assemblies (flange on outside of frame, collar on inside):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883083.jpg)

These are pretty much done, apart from drilling an oil hole in each, swapping the screws for better-looking ones and a bit of a general spit and polish along with all the other parts towards the end of the build.
Title: Re: A Simple Uniflow Engine
Post by: propforward on December 08, 2020, 11:09:46 PM
Really good Gary.

Tapping those small threads can be a tense moment. Although I haven't had too much issue in bronze. Looks like they cam out just fine and dandy!
Title: Re: A Simple Uniflow Engine
Post by: crueby on December 08, 2020, 11:16:18 PM
Gary, do you know which alloy of bronze you used?  They look great, the two halves clamp the side plates when bolted up?
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 08, 2020, 11:18:53 PM
Thanks Stuart.

Yes indeed! The only way to find out how far you can push small taps is by breaking one or two when you're just starting out.

Hopefully you and I are both past that stage, though I don't want to tempt providence...

I usually use a piloted spindle tap wrench but decided just to do it by eye and feel tonight and it came out ok.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 08, 2020, 11:25:38 PM
Gary, do you know which alloy of bronze you used?  They look great, the two halves clamp the side plates when bolted up?

Thanks Chris.

I'm pretty sure it's SAE660 from your friends GLR Kennions, which is where I usually order metal from.

Yes, the idea is as you say - they clamp the side plates. Hopefully tomorrow evening I'll drill the bolt circle holes in the plates for the screws to pass right through, which will take me a step closer to setting it all up unfinished as a test rig and trying the engine on air...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 09, 2020, 10:47:11 PM
The locations of the bolt holes in the bearing flange were transferred to the frame by clamping the frame to the mill table raised up on two blocks, dropping the bearing into the main hole, then finding each hole with the drill and drilling through. Dropping the screws into the holes one by one as I drilled them contributed to keeping the alignment. My pictures of this operation in progress turned out blurry so I didn't post them. Here are the resulting holes, though:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883137.jpg)

The bearings were then fitted to the frame with the bearing flange and the collar clamping the frame between them when the screws were tightened:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883136.jpg)

Later I'll change the screws for nicer ones and drill oil holes through the collars and bearings on the inside faces of the frame plates.

The engine was temporarily assembled once again but this time with the bearings properly installed:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883135.jpg)

This enabled me to measure what will be the width of the finished engine. I will now fix the frame sides to a temporary base in the form of this piece of plywood and fit bracing pieces to stabilise the whole thing in preparation for an air test. For this the end of the piston will need to be fitted with a pin which will open and close the valve.

As noted previously my only serious concern at this stage is whether or not the flywheels will have enough momentum to turn the engine over. If they don't, I'll just have to enlarge them...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 10, 2020, 09:47:42 PM
Nothin' much really.

Just marking out the temporary baseboard for the test setup:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883174.jpg)
Title: Re: A Simple Uniflow Engine
Post by: propforward on December 10, 2020, 09:54:13 PM
It's all time in the shop - and that's good time!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 10, 2020, 10:02:27 PM
All part of the process...

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 15, 2020, 11:38:30 PM
Frame mounting bars fixed to temporary base board and test assembly commenced:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883524.jpg)

I then turned my attention to the crosshead pin. I made this from an M8 stainless cap head bolt and it will be secured with a nyloc (is that how it's spelled?) nut. I appreciate that this solution won't be to everyone's taste but it suits my aesthetic just fine. To enable it all to work together neatly I milled a flat on one side of the crosshead...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883523.jpg)

... and made a counterbore on the other using an endmill:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883526.jpg)

I didn't have an endmill the right size so I turned down the head of the bolt so that it would fit neatly into the counterbore.

The unthreaded section of the bolt was longer than the width of the crosshead fork, so I turned a small bronze collar to take up lateral slack. The nyloc nut was then fitted and the surplus length was cut from the pin:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883525.jpg)

The connecting rod, big end and crosshead assembly almost complete (including a bronze spacer between the main connecting rod and the crosshead section, to get the length right):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883527.jpg)

All that remains is to drill an oil hole for the main bearing. This will be trickier than it sounds because I didn't take it into account at the design stage and the screws which secure the bearing cap are very much in the way. Something will work out, though... The only other job that remains on this assembly is to loctite the two threaded joints together, which will be done at the end.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 16, 2020, 02:25:25 PM
Birthday present from my daughter:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883556.jpg)

The sheer quality of Cherry Hill's work is jaw-dropping, but what most appeals to me is how utterly surreal some of her engines are (like the one shown on the cover).
Title: Re: A Simple Uniflow Engine
Post by: propforward on December 16, 2020, 02:58:20 PM
Hello Gary!

Great progress on your engine. I very much like the quality of finish you get.

I just purchased that book as well - it's astounding. The quality and intricacy of the models is second to none. Inspirational indeed.

And happy birthday to you! All the best - I do hope you are staying well.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 16, 2020, 03:07:16 PM
Aha - we are bibliographically attuned!

Thanks Stuart - all fine here.

gary
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 19, 2020, 06:16:58 PM
For the test setup, these two pieces of wood together bring the centre of the cylinder bore as close to the height of the centre of the crankshaft as makes no difference:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883821.jpg)

They are now glued and clamped together and will be left overnight for the glue to set.

Now, there is a glitch in Stan Bray's original  (and for the most part excellent) plans:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883820.jpg)

The dimension which I have marked 'A' (the length of the cylinder) is given as 35mm. The dimension 'B' is also given as 35mm despite the fact that it is clearly shorter in the drawing. The imperial version of the plans has the same issue so no help there. Clearly the distance between the crankshaft and the mouth of the cylinder needs to be correct or the timing could be affected or the engine may not run at all. I made a few calculations based on possible correct dimensions for B:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883819.jpg)

The 45mm that figures in these sums is the length of the gap in the frame that appears in the drawings. Bear in mind that my build is x3.5 scale to the drawings. Taking a ruler to the drawings suggested that 20mm is likely to be the correct dimension for 'B', which scaled up gives me a distance of 192.5mm between the cylinder mouth and the crank. I'll probably try that first, but it will be instructive to try at least a couple of the other dimensions too to see what difference it makes to how the engine performs.

Because of the type of valve the engine has, I'll have to make a different pin (to locate in the end of the piston for opening the valve) for each setting I try. Ah well.

Not much I can do until that wood glue is set, so time to light the fire and chill out for the evening with some cider...

 :cheers:
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on December 20, 2020, 03:02:06 AM
Hi Gary, there does indeed seem to be a dimension missing from that drawing, but dimension B is not very important in my view.  The critical dimension is the distance from the centre line of the crank to a suitable reference point on the cylinder.  To check this you need the crank throw (a bit too fuzzy to read on the posted photo), the length of the conrod, the length from the wrist pin in the piston to the top of the piston, the length of the cylinder, and the protrusion of the spigot on the cylinder head into the cylinder.

This allows you to check the clearance height (volume) with the piston at top dead centre, and I would also check that the piston clears the exhaust port with the crank at the bottom dead centre, and so locate the crankshaft centre line.  You can then calculate the appropriate reference dimensions on that side frame.

There is a current thread discussing the clearance volume on the MEM Corless engine, but yours is different.  On a normal slide valve engine I normally look for the piston at the dead centres to be about 1 mm, give or take, but on your engine, I suspect it will be better to have more, say up to 25% of the stroke as a guess for a starting point, just so the engine does receive some inlet steam after dead centre.  It will then expand that steam, contributing to the engine output, until the exhaust port opens.  In fact, the positive work by the steam entering the culinder while the pin is open, only equals the negative work required on the entering steam while the piston travels outward from when the pin open the valve.  So all of the net engine output is by expansion of the steam.  Hence my suggestion of making sure there is plenty.

An experimental plan to modify the performance of the engine could be a couple of extra cylinder heads with different length spigots to allow you to change the clearance volume.  Or maybe that is a step too far.

The other thing you have already mentioned is the facility to modify the pin length.  I suspect there is an optimum proportion for the pin length and clearance height (volume) for any given stroke to get maximum power output from the engine.  But clearly the first step and possibly the only step required, is to get it running.  We are all eagerly waiting to see that!

Great progress

MJM460
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 20, 2020, 02:22:32 PM
Hi MJM -

Thanks for this.

It's very possible that I am not understanding your points properly, but my take on it is as follows:

Agreed that dimension B is not important per se. In fact, on my build dimension B doesn't even exist. As I understand it, it's only important here because it determines the position of the crankshaft, which is at the midpoint of 'B' in the drawing. Taking the open end of the cylinder as the reference point, it's necessary to know the length of 'B' to know the position of the crankshaft, i.e. that critical dimension you refer to.

Bearing in mind that I have made everything so far to the dimensions of the drawings x3.5 (including the position of the exhaust ports), then as long as my estimate of 'B' is correct (and I do think it's probably meant to be 20mm in the original) and extrapolate from that to my scaled up version (as per my scribbled calculations above), presumably everything should fall into place as a scaled-up version of the original design. That would then just leave me the job of getting the pin to the length required for optimum valve lift.

I'm still of a mind to go with that, but the test rig will allow me to play around with things to find where the sweet spot actually lies (which I would have thought would correspond with the plans but of course may not).

Am I making sense here?
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 20, 2020, 09:50:41 PM
The following photo shows the position of the piston at top dead centre when everything is measured and laid out according to the hypothesis that 'B' in the plans is 20mm. It took only a very minor adjustment  from there to arrange things so that the back end of the piston is flush with the open end of the cylinder at top dead centre. That suggests to me that I may be on the right track. The broken centre drill and the two screws were intended to show the positions of (left to right) the top end of the interior of the cylinder, the end of the piston at top dead centre and the end of the piston at bottom dead centre. However they don't really succeed in doing this due to camera angle and parallax. In reality the piston opens and closes the exhaust ports as it travels back and forth, and there is a significant gap between the end of the piston and the end of the cylinder at top dead centre - maybe not the 25% of the stroke that MJM recommends, but a fair bit. So hopefully I'm on track.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883936.jpg)

So then it was drill press time:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883937.jpg)

I love using my floorstanding drill press which I converted to three-phase with variable speed control. OK - I'd rather have a big old camelback like the Rockwell I saw in France last year going for a song but had to walk away from due to not having any room for it...    :(

Not often I find a use for the random bits of metal I keep, but this time I did:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883938.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883939.jpg)

And finally a shot of the engine at top dead centre:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883940.jpg)

I think it looks pretty neat with the way that the back end of the piston is flush with the cylinder face at that stage of the cycle.

The four pieces of angle clamp the cylinder surprisingly tightly (and it looks like a mediaeval engine with that bare wooden temporary cylinder support!) but I will put some kind of securing strap over the top of the cylinder to make sure the cylinder doesn't fly off when I introduce some air. The only other thing I need to do before I test it is of course to make the pin to operate the valve.

Then we shall see if these flywheels are big enough...

Meanwhile, though, I couldn't resist oiling it all up and attaching a hand drill to the end of the crankshaft that protrudes through the bearing on the outside of the frame. The effect was formidable - it looked and sounded great with that cast iron piston pumping air through the cylinder, and the valve snapping open and shut... 

8)
Title: Re: A Simple Uniflow Engine
Post by: propforward on December 20, 2020, 10:05:11 PM
I think it looks pretty neat with the way that the back end of the piston is flush with the cylinder face at that stage of the cycle.


100% agree! I think it's looking wonderful!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 20, 2020, 10:12:31 PM
Cheers Stuart - very kind of you.

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 21, 2020, 07:56:19 AM

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/883820.jpg)


Duh!

Just looking at this again - the numbers at the bottom of the drawing give a clear indication of dimension 'B'.

Assuming dimension 'A' and the 45mm 'gap' are correct (which I did):

100-(35+45)=20

Instead of seeing what was staring me in the face, I took the long way round. Reassuring to know that I arrived at the right conclusion though.

Or at least I think I did...  :)
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on December 21, 2020, 11:00:49 AM
Hi Gary, I suggest that you were on the right track earlier using the crank throw, conrod length and piston dimensions to check the answer.  And the piston flush with the end of the cylinder is a nice touch even if not strictly necessary.  (The calculation in the more recent post does not check the dimension as it still requires that assumption.)

It is difficult to tell just how much clearance volume you need, 25% of stroke was a suggestion if all else failed to answer the question.  Donít worry if the dimensions are giving a different figure.

It can be altered either way by modifying or remaking the cylinder head if necessary, just easier to reduce the clearance volume by making a head with a spigot that extends further into the cylinder.

Looking good for a test in the near future.

MJM460




Title: Re: A Simple Uniflow Engine
Post by: pgp001 on December 21, 2020, 11:15:25 AM
Yet another perfect demonstration of why I NEVER use other peoples drawings without proving them first.

Years ago when I was looking to choose one to build from all the current model traction engine designs, it soon became apparent that they all had lots of errors that had never been corrected since they were published, the only way you found out was by scrapping lots of parts or occasionally seeing a correction update in Model Engineer magazine a few weeks later.

As a design engineer by trade that really frustrates me, if I operated like that in my job I would be sacked !!

So from then on I have always done my own drawings originally using Autocad, then in later years on Solidworks 3D CAD, even if I am just copying existing designs. That way I don't cut any metal until the plans are proven.

As for the 1/4 scale traction engine, I chose to model one that was unique, which was a Ruston Proctor SCD compound tractor that we used to own in full size. I used a combination of original manufacturers drawings backed up by loads of detailed measurements from the actual engine, followed by making all my own patterns for the castings. It was a mammoth project but no scrap parts were produced because of drawing errors.
I am doing exactly the same with "Agnes" at the moment, and that is why I am not the fastest engine builder around.  :)

I think the problem might be that some of the designs published in magazines have never actually been produced by the designer prior to issuing them.

Rant Over  >:D

Phil
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on December 21, 2020, 11:14:32 PM
@ MJM - putting it all together, I think that what I have ended up with does match the plans, scaled up x3.5. The back of the piston being flush with the cylinder face at top dead centre when the dimension of 20mm for 'B' on the drawing is followed (give or take a tiny adjustment) seems to me to confirm that I'm on the right track as I suspect the 'flush effect' is a deliberate design feature. You are right that there is no practical need for this effect but it does look pretty tidy.

But the proof of the pudding... not long now till I can air test it, then we shall see. One thing's for sure - it's not coming off that test rig until it works!

@ Phil - I take your point, and I am aware that plans often have glitches that can cause headaches, many I am sure much worse than the one discussed in this thread. But to be fair, as far as I can ascertain this one was a single typo, and it looks to me that all of the other dimensions for this engine make sense. Admittedly this should not happen in a published book (it's Stan Bray's 'Making Simple Model Steam Engines'), irrespective of whether the mistake was made by the author or someone else in the production line, but short of going through the whole book I do get the sense that it was a one-off typo. Unfortunately (unlike yourself) I don't use CAD - not yet, anyway - but a ruler laid on the drawing pretty much sorted this one out.

Cheers both.

gary
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 03, 2021, 09:10:03 PM
Hi...

Hope you all had a great Festive Season.

Progress on the engine has been slow. The cylinder is now held down on the test setup with a wooden strap and I don't think it's going anywhere:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/885172.jpg)

The piston has been fitted with a temporary pin:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/885173.jpg)

I used M3 galvanised threaded rod and drilled and tapped the end of the piston accordingly. I wouldn't use this material on the finished engine, but it was the only threaded bar of that size that I could find. I was keen to use a threaded pin at this stage so that it could be screwed in and out to adjust in order to set the correct length to lift the valve: At this length it achieves that, though whether it does so optimally I cannot yet say.

Then however, other priorities took over. For a long time my tiny shed workshop here has become increasingly messy, overstuffed and unworkable:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/885176.jpg)

Storage space is a major issue and the fact that the lathe was sitting on two workmates with dead space beneath didn't help, so a few weeks ago I ordered this:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/885175.jpg)

It arrived much sooner than expected, and the huge cardboard box had been sitting in the house (nowhere else for it!) for quite some time. The break between Christmas and New Year offered an opportunity to get some throughput going with it so the engine was temporarily put aside.

These things tend to get worse before they get better...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/885177.jpg)

... but eventually some order begins to crystallise out of the chaos...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/885178.jpg)

... and - with perseverance...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/885179.jpg)

... the workshop is in great shape!

The lathe and large drill press have swapped positions, and just about everything in the shop has been assigned a new storage space. It's still full to the brim, but not (at least for the moment) chaotic. Also (not in the photos) are two new and very bright LED work lights that flood whatever they're pointing at with serious illumination, and being cordless they can be easily moved around the shop as the needs of the job determine.

Back to the engine today, and all set up for an air test, I quickly discovered that I didn't have enough of the right kinds of connectors to make a working air line between my small compressor and the engine!

Oh well... out to the shops as soon as the coming week allows, and I'll probably also have to make a connector to connect other connectors together...

No rush, I guess...
Title: Re: A Simple Uniflow Engine
Post by: propforward on January 03, 2021, 09:34:30 PM
Great to hear from you Gary - Happy New Year to you! Good to see you posting again. The new bench addition looks great - a massive improvement! You must be well happy with that.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 03, 2021, 10:55:43 PM
Cheers, Stuart!

Yes, the new bench raises the tone somewhat.   :)
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on January 04, 2021, 10:54:31 AM
Hi Gary, a new chest of drawers with a nice bench top never seems a very exciting purchase when there are so many tools to buy, but it probably makes a bigger difference to all your projects than just about anything else, and gets used more than just about anything else.  Makes everything so much easier to find, so saves frustration all around. 

I went in to buy a small set a year or so ago, and the hardware store was clearing out the bigger industrial ones to concentrate on the smaller ones.  I bought the big one at a very reasonable price, and it has made a huge difference.  I went back recently and bought another one which would fit in another space I was not using well.

I am sure you will find that nice bench top great as well.

And good to see the progress towards a test of the main engine components.  Not far off now.

I hope the clearance where that pin goes through the cylinder head is not too tight, it might mushroom a bit with the hammering it will get.  When you have the length sorted, it might help to go for a tougher material, that can be hardened with appropriate tempering.  All steps to ponder for the future.


MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 04, 2021, 11:49:38 PM
Hi MJM.

Thanks for looking in once again.

Yes, good storage is absolutely invaluable, and tidiness in the shop can make the difference between enjoying the experience of being in it and that of just tolerating it!

I have indeed been thinking about that pin. The ball in the check valve would be easier to replace than the pin so there's no reason not to make the pin hard (unless the ball is swapped from the stainless steel one to a nitrile one). Even though there is enough clearance, mushrooming of the pin would change the length of it so it needs to be durable.

Food for thought, but I'll stay with that nasty galvanised one at this point for test purposes.

I remain very dubious about whether or not the engine will run without enlarging these flywheels, but it's definitely worth a try. Am hoping to get out to the shops for airline connectors tomorrow, but may not be able to find time to test the engine until next weekend. Work...!

Cheers,

gary
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 10, 2021, 09:36:11 PM
Hmmmmmmm.....

Got the connections for the air line sorted out - just had to drill and tap one part to take the ME thread on the valve:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/886011.jpg)

I then tried to run the engine in test assembly form on air, not expecting it to work. Sure enough it didn't.

I slackened some nuts and screws to loosen the assembly up as it was running a bit tight. For the same reason I attached a hand drill to the end of the crankshaft and spun it for a while. Back on the air and still nothing, even at 100 psi from my small compressor.

To make a start in testing out the 'flywheels too small' hypothesis, I fixed a lathe chuck to the end of the crankshaft to create more inertia:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/886012.jpg)

Still very, very little. You can feel it trying to turn over, but it's still light years away from running.

I have a small bunch of theories on this, some of them incompatible, though more than one may be correct:



At this point in time all I can do is fiddle about and test these parameters as far as possible.

Needless to say, if anyone has any comments on the above theories or other suggestions these will be most welcome at this stage...
Title: Re: A Simple Uniflow Engine
Post by: crueby on January 10, 2021, 10:19:41 PM
If it was a normal d-valve engine, I'd say loosen the screws on the cylinder end to see if the compressed-air and exhaust timing was right, and not coming in from both sides at once or not letting the exhaust out. Are you hearing any escaping air at all, anything going through the engine? Air passages large enough, not blocked by a gasket, timing, are all the usual suspects. Never done a uniflow so I dont have a good mental image of how they work. That chuck on the crankshaft should be plenty heavy if all else is okay.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 10, 2021, 10:32:29 PM
Actually Chris I have no gasket between the cylinder and the cylinder head - it's just screwed tightly on. I didn't notice any air escaping but I will check for that at my next shop session. My hunch is that won't fix it but it's definitely worth checking.

The timing will be determined by the amount of valve lift (i.e. length of the pin). I'll be playing around with that too.

Could be multifactorial...
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on January 11, 2021, 06:15:54 AM
Hi Gary, disappointing when we get to connect the air line and it doesnít run, but who among us havenít tried, just to see, before the engine is quite ready?  I am quite sure that it will run, we just have to see how well.

Thatís an intimidating list of potential problems.  Fortunately a number of them are quite low probability, so letís start with the more likely.

First the obvious errors as already mentioned by Chris, and no doubt others by the time I write this.  It is also worth trying to deal with whether it is just too tight before looking for anything more obscure.  These little engines donít produce a lot of power, and friction can easily absorb all they make and more.  If itís tight, apply a little more oil, then take out the wrist pin so you can check separately whether the crank shaft main and big end bearings are running freely, and if not, why are they binding?

Then try moving the piston to see if it is moving freely.

I would then check the air passages.  With the piston at bottom dead centre, the valve should be shut so no air flow. 

Then with the piston at the top, valve should be open, but again no air flow because the exhaust ports are closed.  Donít need much pressure, 2 -5 psi should be enough to tell, but not rip the flywheel out of your fingers.  Exhaust ports are obviously closed off by the piston, but much leakage around the piston means too loose.

If you then allow the flywheel to turn slowly still with very low pressure, you might feel the valve closure point, and then a pulse from the exhaust when the exhaust ports open.

Then, can you be a little more descriptive of what you mean by ďtrying to turn overĒ?  I am guessing you mean that when you pass over dead centre, it turns about 3/4 of a turn, then bounces back when the valve opens, rather than continuing over top dead centre for another revolution.  Probably the same effect no matter which way you allow it to start.  I believe that it should run either direction as the timing is quite symmetrical.

At this point, you have three variables, the air pressure, pin length and that inertia you are worried about.  Much more encouraging than 12, but I will explain more about why I consider the others less likely later.

For the engine to run successfully, when you flick the engine over top dead centre, it should take off for about half a rev to where the exhaust ports open.  They need to be large enough to reduce the pressure in the cylinder to nearly atmospheric pressure.

If the ports are too high in the cylinder, the expansion part of the stroke will be short, and not produce enough power, and if too small, they will not open enough to exhaust sufficient air, and the compression of this air after the ports close will absorb too much energy.

 During the power stroke, the flywheel has to pick up enough speed for the energy in the flywheel to compress that low pressure air remaining in the cylinder to the point where the pin touches the valve, and continue against the incoming air until top dead centre is reached, beyond which point, the air pressure and piston motion are in the same direction, so producing work which will accelerate the flywheel again. 

The principle is that the positive work produced by the air entering the cylinder after top dead centre, plus the work done during the subsequent expansion with the valve closed, must be more than the negative work required to compress the air remaining in the cylinder when the exhaust port closes, plus the work done against the incoming air once the pin starts opening the valve.

Air pressure is the easiest to experiment with.  I am not sure whether high or low is better, but more likely some intermediate pressure.

I am thinking the pin length is the most critical factor.  If the pin is too long, the negative work, before the piston reaches top dead centre might be too much.  You might expect that you will get it all back after top dead centre, but thermodynamics being what it is, dictates that you will get less back.  The positive work by the expansion of the air after the valve seats is likely to be more  than the compression work on the return stroke before the valve opens, as the pressure will be higher throughout the expansion process.  Hence, I suspect that a shorter pin, which opens the valve later might be the constructive direction to try.

The flywheel inertia might be troubling you here.  If it is too low, it would not store enough energy to drive that negative work part of the cycle.  However, a low inertia flywheel will accelerate quickly, and as the energy stored is proportional to speed squared, more speed easily can make up for less inertia, particularly if you start the engine with a really energetic flick.   If it is too low, it will take off for that first half a rev, then stop and bounce back when the pin hits the valve, or perhaps after a very small pulse of incoming air.

On the other hand a very heavy flywheel will not accelerate quickly with the low torque available, and the extra mass will introduce more bearing friction.  With a good flick to start, it might run a few revs then stop due to loosing more than it produces each revolution.  I think you will get an idea whether the flywheel is very lively due to being too light, or very sluggish, due to being too heavy.  But in reality, there is a very wide range of flywheel inertia that will operate quite satisfactorily.  You have covered a good range between your original flywheels and the lathe chuck.

So I am suggesting that the starting point is to try varying the pin length.  Either make up two or three, or remove the piston and adjust the pin, depending on the construction.

I am suggesting that the effect of the pin is all about timing of the opening, and the valve lift in itself is less significant.  I think I would try first a very short pin, that just allows a quick puff of air in each stroke.  Then try the effect of increasing the length of the pin, but that is getting ahead of myself.  The short puff of air means less work to get the piston to top dead centre, but not much effect on the work done during the expansion part of the stroke with the valve closed.

More than enough words for one post.  I hope that it is a help towards understanding how the engine works, and even better if you already have the engine running by the time you see this.  We all want to see the engine run.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 11, 2021, 11:18:00 PM
Hi MJM.

Thanks for this fabulous exposition, which I will copy, paste, print off and take out to the shop as a guide to my next attempt to get the engine running. You really 'get' this engine.

I have been busy working all day and into the evening, so no shop time unfortunately and it could well be the same tomorrow. However, last night (before you made your post) I took another look at the chapter in Stan Bray's book about building this engine and saw something that I had forgotten. He says if you make a scaled up version, don't scale up the valve lift. I take your point that pin length is not just about valve lift but also about timing, but SB's point above already had me thinking that I should shorten the pin. Your post this morning also steers me in that direction so it's the first thing I'll do.

If I recall correctly (without going and looking at the book again) he specifies 1/32" as the valve lift. Now, I have no idea what the valve lift on my engine currently is (very difficult to measure accurately) but some trial and error will be instructive I think. Fortunately I made a temporary pin out of threaded bar to enable me to adjust it by winding in and out if needs be. So tinkering with the pin will be the first thing I do, starting with minimal length and gradually increasing...

Also very interesting is your point that maximum pressure is not necessarily optimum. I had rather short-sightedly assumed that 'the more pressure the better', but I now understand from your description of positive and negative work that this may not be the case.

And then there's inertia. That lathe chuck... I suspect Chris is right in saying that ought to be plenty. I could take my three-jaw off the lathe and put it on the other end of the shaft, but no doubt that would be way over the top!

As for the exhaust ports, SB advises against making them bigger, but instead to drill two or more on bigger versions of the engine. Currently I have two, one on each side of the cylinder, positioned relative to the cylinder ends as per plans x 3.5.

You have given me lots to think about and a sense of how to proceed with tweaking the parameters. Much appreciated!

I'll get back to it as soon as I can...
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on January 12, 2021, 07:46:12 AM
I'd time it so the exhaust has opened  a little before the piston reaches the end of its stroke and onlt just gets to closed as the piston comes back to TDC. Air should  not be entering until exhaust has closed at  or just after TDC and have it shut off at 3/4 of travel at the most.

Pressure really only needs to be enough to overcome ant friction as you are not making it work at this stage, use something to control the flow once compressor regulator set to desired pressure
Title: Re: A Simple Uniflow Engine
Post by: Zephyrin on January 12, 2021, 08:18:18 AM
as the piston is also the valve, most probably timing is wrong...I don't see lot of possibilities !
air intake never opens, I would bet.
a piston extension pushes the intake valve, but if the air pressure is too high, or piston extension too short, it never happens.

moreover, the piston pin that pushes the valve also plugs the port, being of the same dia, no chance that it will work without some changes !
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 12, 2021, 08:32:36 AM
Thanks Jason and Zephyrin.

It all points to one thing, at least initially - experiment with the length of the pin/piston extension!

I'll start with the air pressure about 30 or 40 psi and fiddle with the length of the pin.

 :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: john mills on January 12, 2021, 09:38:28 AM
is  this design the type whern the pin opens the valve ,the inlet is only open for a short time.from when the pin hits the valve until  piston goes over top dead centre and to the position when the pin is no longer holding the vale open so the time is short and allows for expansion the port for the exhaust is only open when uncovered by the piston  so the ports need to be as much area as possible most of the remaining pressure hats get out while the ports are uncovered .the piston has to get to the valve to open it for the next cycle .it is meant to suit high pressure and speed  if it can get going .if the exhaust ports are to small and are not uncovered for long enough
for enough pressure to get out it will be in trouble .it should try to go as it comes over top dead centre while the
valve is open  after that it will depend on how much pressure got into the cylinder how  much it expands to get to the exhaust ports and how much gets out how much the pressure drops to see if it can get back to open the valve
again.     thats  what i think the disign is .      Is that what it is i have not seen your drawings.

interesting to see how you get on .    John
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 12, 2021, 10:40:33 AM
John - yes, that's exactly the kind of engine it is.

Indeed, the area of the exhaust ports did entail a bit of guesswork for me as I increased the scale from the drawings. If adjusting the pin length and the pressure don't get it running, thinking about the size of the exhaust ports could be a next step I guess.

Thanks for your input.

gary
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on January 12, 2021, 10:49:51 AM
Hi Gary, you are most welcome.  It does my old brain good to take on the challenge of understanding the physics that drives these engines, particularly ones like this one that are a little different.

It certainly looks like the consensus is to first try shortening the pin.  I think the screwed pin to allow adjustment is a good idea, but you might need a method of locking it in position.  I donít know if you have room for a lock nut, but the pin gets quite a hammering and this will loosen it quickly.  You donít want to repeat Rogers experiment with shortening a grub screw.

There are two separate factors involved with the valve and pin.  First, the length of the pin determines the timing.  But then the size of the hole in the head gives the flow area for the incoming charge of air.  Obviously the pin blocks part of the opening.  So a larger diameter pin will need a larger diameter hole.  Once the ball starts lifting off the seat, the flow area opened increases rapidly, though the passage that retains the ball is also important.  I donít know what shape you have.  It may be something to come back to, but first try and get the pin length for timing.

The exhaust ports are similar.  Timing and flow area have to be considered separately.  You donít want the exhaust open to early, as that will limit the expansion which is providing the power, but as John says, you do want them to open enough to let out as much air as possible, as once the port is closed, you have to compress any remaining air as the piston returns to where it opens the valves.  Extra holes as you say, is the way to go, but it makes collecting the exhaust a challenge.  No problem for air, but I believe that you want to run on steam eventually.

MJM460

PS I did make a small edit to yesterdayís post.  The energy stored by the flywheel is proportional to speed squared.  A smaller flywheel can store as much energy as a larger one by rotating a bit faster.  The torque available from the engine during that power stroke will accelerate a small flywheel to a higher speed than a larger one.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 12, 2021, 11:07:21 PM
MJM -

Good point re the thickness of the pin and how much room there is around it for the air/steam to flow. Again possibly something to play with and although I have now drilled and tapped a hole M3 in the piston, there's no reason why the projecting part of the pin couldn't be turned down a bit if needs be, leaving the part inside the hole M3.

I had thought of the potential problem of the pin winding in or out in use, effectively changing its length. That would inevitably happen, and the current setup is not a final one. My thinking was around some kind of adhesive but there are potential problems with that I'm sure, especially as yes - I do aim to run it on steam eventually. I hadn't thought of a lock nut, which would be better. Don't know if there's room for one - I'll check, hopefully tomorrow evening. However, the current setup is very temporary. As soon as the engine runs I'll be taking the test rig apart and moving on with finishing the engine, so the pin won't be subject to a huge amount of stress in its present form. A proper version can be developed later.

On the steam ports: apart from making fabricating an exhaust manifold more tricky, is there any other reason for not drilling more? In other words, is it necessary to make sure that there isn't too much exhaust/loss of pressure at that part of the cycle? Or is it a case of the more steam that is exhausted, the better? If the latter, I'm sure I could drill one or more extra ports and still be able to make a manifold of some kind. But I don't want to go making holes that I'd have to then plug up again!

Meanwhile, though - the pin!
Title: Re: A Simple Uniflow Engine
Post by: crueby on January 12, 2021, 11:13:42 PM
Hi Gary,
Are there any diagrams around for how this type of engine works? I'm baffled at the moment...  :headscratch:
Thanks,Chris
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on January 13, 2021, 02:54:45 AM
Hi Gary, it looks like you have the pin issues under control.

With regards to the exhaust ports, again there are the two functions, timing, and flow area. 

The exhaust ports must not be uncovered by the piston too early, as that reduces the useful work done, and you need all you can get.  But you want enough port area to get the pressure in the cylinder close as possible to atmospheric pressure before the piston closes them off on the return stroke.  So more holes is the way to go, so long as you leave enough metal for the cylinder to hold together.  Just how much is enough is a question more difficult to answer. 

In principal you can put the ports lower in the cylinder if you have more holes.  However, there is very little work done in the bottom few degrees of crankshaft rotation, as you can see if you look at sine tables near 90 degrees or closing near 0.  And you do have to uncover the port for long enough for the air to escape.  Not easy to tell of you have too little.  I suspect you would need to get it running, then drill an extra hole to see if it runs better and if so, drill another and so on.

Looking forward to the next tests,

MJM460

Title: Re: A Simple Uniflow Engine
Post by: Jasonb on January 13, 2021, 07:39:15 AM
Having had a google about I'm a bit clearer how this engine works now, must say it's crying out for an exhaust like we use on the CHUK engines which stops the rising piston from having to compress any trapped gasses

There is a good explanation over on HMEM of the fine line between too much and too little pressure if you search "tappet/clapper engine".
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 13, 2021, 01:55:41 PM
@ Chris -

Here's an overview of it, copied from Stan Braye's book:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/886242.jpg)

Pretty simple concept. The pin in the end of the piston opens the valve, and the incoming air or steam pressure closes it again. It exhausts through a port drilled through the cylinder wall (not shown in drawing). Interestingly though, apropos of MJM's point above, the diameter of the pin in the drawing allows no space around it for steam flow.

@ Jason -

Thanks for that - I'll check out the source you refer to. I'll be interested to see what the CHUK exhaust is and how it works, with a view to possibly incorporating similar on this engine.

@ MJM -

As always, there are parameters in mutual influence! I have already drilled two exhaust ports (positioned as per plans) so I'll go with them for now, and probably drill one or two extra in the same plane if it appears to be required later. Unless of course the exhaust that Jason suggests leads in a different direction altogether ...
Title: Re: A Simple Uniflow Engine
Post by: crueby on January 13, 2021, 02:15:35 PM
Thanks for the drawing Gary, now it makes sense to me. The length and clearance around the pin look like critical dimensions for air flow.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 13, 2021, 02:56:00 PM
You're welcome Chris.

Thank you for your interest and encouragement.

gary
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 13, 2021, 06:25:44 PM
Having had a google about I'm a bit clearer how this engine works now, must say it's crying out for an exhaust like we use on the CHUK engines which stops the rising piston from having to compress any trapped gasses

There is a good explanation over on HMEM of the fine line between too much and too little pressure if you search "tappet/clapper engine".

Jason - if you look in again on this here thread - I found the thread on HMEM. Thanks:

https://www.homemodelenginemachinist.com/threads/tappet-clapper-valve-steam-engine.26288/ (https://www.homemodelenginemachinist.com/threads/tappet-clapper-valve-steam-engine.26288/)

I also googled for the exhaust you refer to on the CHUK engines, but without success. Can you by any chance suggest where I might find info on this?
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on January 13, 2021, 06:49:32 PM
Thinking about it some more I don't think the exhaust will work as you will loose expansion as the cylinder fills.

What size hole is in the head where the pin goes in to meet the ball, does not look to be much clearance on that drawing.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 13, 2021, 07:10:35 PM
Ah ok... I'll stick with the original arrangement then.

Yes, in the drawing above it looks like there is no clearance at all. In the actual plans he gives the pin as 1.5mm diameter and it looks like the passage is 1.8mm diameter. So pretty close.

My engine is 3.5 times the size. I didn't measure for the valve - I just put an off-the-shelf clack valve in the end of the cylinder. Will need to check the size later, but it's large-ish. The temporary pin in mine is a piece of M3 threaded bar. Again, I'll have a look at the clearance when I go out to the shop shortly.

But suffice to say, while I have pretty much built the rest of the engine to plan, there was quite a bit of guesswork with the valve. I appreciate that this may come back to haunt me, but I'll start with other parameters, i.e air pressure and pin length, and see how I get on.

Cheers.

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: crueby on January 13, 2021, 07:59:23 PM
Two tests that I would suggest to narrow things down, going from your description that it does not seem to have much power on the piston.
 - Remove the piston but leave the clack valve in place, turn on the compressed air feed, and push a length of the rod in through the cylinder to open the valve, and see if you are getting a decent flow of air. If not, then something in the valve or rod passage itself is the issue, too small an opening around the valve or rod most likely.

- Opposite case - remove the clack valve but have the piston/conrod installed. When air is applied, it should push the piston down all the way and be hard to manually push it back. If not, then the rod may be closing up the passage too much. Also in this scenario with the air line disconnected the engine should turn over by hand relatively easy.

Hope drawing the fence on the problem like that will help narrow down where the issue is! 
 :cheers:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 13, 2021, 10:47:02 PM
Chris -

Yes. In fact I tried opening the valve manually with the piston out tonight using a couple of different long poky things, and there was a good airflow with the valve opening and closing as it should. This was with the compressor end of the air tube disconnected and me blowing through it with my mouth, in the interests of sensitivity. I didn't test this with a length of the pin material though because it was not to hand and the hour was late, so I will do so tomorrow night as priority. However, I think it will be ok because the pin appears to have a fair bit of clearance - the pin is M3 and I'd guess the valve bore at 4 or 4.5 mm.

I'll also try your second idea if I don't get it running soon. I'm fairly optimistic about that because the crankshaft and big end are running nice and free and air even at low pressure easily has the piston sliding. So yes - great ways to test the flow around the pin; thanks for that.

In addition to the above, I tried various lengths of pin but no joy. Then - at the end of the evening - it occurred to me that I have been stabbing wildly in the dark over this. The recommended valve lift is only 1/32 inch so the sweet spot (outside of which the engine probably won't run at all) is very small and I probably haven't been near it yet. Instead of wild guesswork, measurement is the key. This had me thinking that a digital depth micrometer would be great for this but a quick look at the prices put me off. Rather than spend a hundred quid or more (at least for now) I'll try to rig up another way of measuring to where the end of that pin should be at top dead centre. Digital caliper and some kind of jig...

Feeling fairly optimistic about it though. I don't think the engine is too shabbily made, so at this point I see no reason why it shouldn't run once the relevant parameters are in balance...

 :cheers:
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on January 14, 2021, 02:13:08 AM
Hi Gary, looks like the pin has enough clearance for flow to be a minor issue at most.

Donít worry about a depth mike, put some degree marks on your flywheel near top and bottom dead centre, and use them rather than the actual lift measurement.  You can calculate the height from the degree marks by geometry if you wish, but as degrees of rotation is a proxy for time open, it is probably more accurate than lift, as the lift varies so little near top and bottom dead centre, while the time of opening gives time for fluid flow.

Once you have a mark for the valve being just touched by the pin, an M3 thread is 0.5 mm pitch, so one turn changes the pin height by 0.5 mm.  A mark on the top of the piston will help you keep track of how far it has been turned.  I guess you have to grip it with pliers as you donít want a slot in the top to be hammered by that valve.  Or machine some spanner flats on the pin.

Does that check valve have a spring to hold the ball in place when there is no air pressure?  Just a little point to be aware of, if it does not appear to close properly when starting.

I am still thinking about whether the pressure can be too high.  Not necessarily a given.  But it will make it necessary to get the flywheel moving much faster to have the energy to drive the engine over top dead centre against the incoming air.  I have a vague memory of reading about starting the really high performance versions of the engine with a pull cord like starting a model marine diesel or glo plug.  But given a really energetic flick to start, it goes like the clappers.

Hmmmm...  Goes like the clappers, eh?  Sounds like there is something catching in the air at the moment.

MJM460


Title: Re: A Simple Uniflow Engine
Post by: steam guy willy on January 14, 2021, 03:00:16 AM
Hi ..could you make the push rod a more triangular shape   a bit like a safety valve ? this would give you a lot of air entering the cylinder ?? just a thought

Willy
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on January 14, 2021, 07:13:00 AM
If you put a small bit of rod into the air inlet and hold it against the ball you should be able to see how much it moves when the piston's pin moves the ball.

Have you tried the same test of the valve that you mention with it under air pressure, would give an idea of how much force the piston needs to open the valve.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 14, 2021, 01:22:06 PM
Lots of ideas there - thanks guys.

@MJM - Degree marks on the flywheel sounds like a good way of monitoring the valve. Will keep that in mind. Would like to see this engine going like the clappers (!) but a more sedate pace would be fine too. We shall see.

@Willy - good idea. I guess another way would just be to turn it down a bit. I still have to properly test the valve with a bit of pin material though - it may be ok as is. I should know by this evening...

@Jason - testing the valve lift with a bit of pin material pushed in from the other side. Absolutely pragmatic idea, and beautifully simple. Sometimes I despair of myself that I don't think of things like this. They seem obvious after I hear them from someone else! As for testing on the compressor - I made a start but a few air line issues arose so more testing to follow.

You have all given me much to consider and try - much appreciated.

Now, I'd better get back to my tax return...  ::)
Title: Re: A Simple Uniflow Engine
Post by: crueby on January 14, 2021, 04:02:34 PM
In looking at the diagrams, seems like the engine would be able to run the same in either direction, since it is just the piston movement controlling the valve directly??  Also, is this an engine that would run much better on steam, since it would be able to take a small charge of steam during a short valve opening which would then expand more during the stroke, more than compressed air would? A longer valve opening would seem to be counterproductive, since it would mean that pressure would be coming in longer during the piston-up travel. One of those designs that makes my head hurt!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 15, 2021, 12:57:04 AM
One of those designs that makes my head hurt!

Not as much as it's hurting mine!

To think I chose this because it's only my second engine (the first being an oscillator) and I thought it would be easier than something with a separate valve. Easier to build, perhaps, but...

I should probably have just gone for a Corliss or a triple expansion engine instead!   :lolb:

Yes, it should indeed run equally well in either direction, for the reason you give.

I have had the same thought about steam, and how its expansiveness would help in this engine. Unfortunately I do not have a boiler that would power it. Yet...  ;)

And yes, from all I have gleaned in this thread, I think a short sharp opening of the valve is what's required. In the book Stan Braye specifies a valve lift of 1/32" irrespective of whether or not the engine is scaled up.

I think it all points to it requiring very accurate adjustment to get everything in balance to get it to run at all. And I am a little haunted by the guy on youtube (same guy as in the thread Jason pointed me to) who says that he and his grandfather couldn't get theirs running for love nor money.

That said, they didn't have you guys to help them...   :)
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 15, 2021, 06:40:04 PM
I don't think the engine is too shabbily made, so...

Even as I typed that I had an uneasy sense it would come back to haunt me, and sure enough...

Some good bits first though. With you guys' encouragement I have now established that the pin leaves room for a good flow of air around it. I have also homed in on the pin length and located the small range between the point at which the pin just touches the ball and the point at which the pin pushes the ball too far so that the latter is rammed against the back of the valve. Within that range there is a smaller range  - a sweet spot - in which the valve action feels 'alive' and the piston gets a satisfyingly sharp kick from the incoming air from the compressor. So some progress there in figuring things out.

But now the not so good bit. Even with the pin optimized, the piston doesn't have enough momentum to even reach bottom dead centre never mind start a new stroke. It became clear that there isn't enough pressure to drive it. I was about to blame my bottom-of-the-range puny compressor, but then noticed that when the piston reaches top dead centre and opens the valve, there is a sharp spurt of air from the exhaust ports. Not good, I think, because the ports are meant to be closed at that point. I guess that even in an ideal situation there may be a tiny bit of leakage but this feels like more than that. From the bottom end, the piston looks to be a nice snug fit in the cylinder. I can't remember what the top end looks like but during the weekend I'll dismantle the setup and check and do some measuring. I'm concerned that there may be a taper in the equation, with either the piston being narrower at the top or (probably more likely) the cylinder wider at the top.

If this is the case, I don't relish the thought of making a new piston, and I REALLY don't relish the thought of boring a new cylinder! I'm thinking that a couple of rings (is viton the kind of rubber that is used?) may be the answer, but on this I am no expert. You'll recall it's quite a hefty piston (cast iron, 35mm diameter, and long):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/870786.jpg)

Will be most interested in your thoughts on whether piston rings may be the way forward here, and in any relevant issues around that...

I do have some graphite yarn which I could try but not sure I have enough of it for a piston this size. Also, given the choice I'd go for viton or some kind of rubber rings.

Trepidatiously,

gary

Title: Re: A Simple Uniflow Engine
Post by: Jasonb on January 15, 2021, 07:21:41 PM
Your ball movement issues are no doubt due to using a reversed clack valve as these tend to have a way of limiting the amount the ball will lift off of it's seat and that is what you can feel when the pin pushes the ball too far. It may be possible to get the valve apart and modify the internals.

At TDC there should be no or very little seepage out of the exhaust, once running a bit of loss may not matter but if you are getting a lot of air loss then you are loosing a lot of energy. Adding a ring will help with sealing but will also introduce friction which will need enough energy stored in the flywheels to overcome as the piston is carried back to TDC. It should be able to work with no rings but if needs be a single one that is only lightly compressed may be an option and you can always remove it if it causes too much friction and run with an empty groove in the piston.

There is also a message waiting for you.
Title: Re: A Simple Uniflow Engine
Post by: crueby on January 15, 2021, 08:12:44 PM
Seconding what Jason said, a viton ring will seal well, but does add friction. Sometimes just a layer of grease or oil on the piston will help a lot. A groove around the side of the piston will retain the oil better.
Title: Re: A Simple Uniflow Engine
Post by: Admiral_dk on January 15, 2021, 08:51:57 PM
I just had a look back in this thread and it's a VERY heavy piston + rod and I can only spot a very small hole on the side of the cylinder - absolutely not big enough to be the exhaust ....

Some years back there was a build here of a record breaking Flash Steam boat (actually not the boat itself - but the boiler and engine) and the engine was extremely similar to a Nitro burning racing two stroke Airplane engine - with the exception of the feed pump for the boiler being part of the engine.
His piston and rod weighted a few grams and the piston were (if memory serves) lapped into the cylinder, to get an extremely tight tolerance.
The exhaust port was just as big as the Nitro engine .... so probably 25-30 % of the diameter in with and a height of 20-40 % of the stroke ....

Since you aren't going after this kind of power - I would consider two ports opposite each other - each taking up a fourth of the circumference and start with 20 % of the stroke. You can divide into 3 or 4 ports instead.
But you still have a very heavy piston and rod arrangement for a small intake off steam (or worse air) .... has anybody had a runner out of this design yet ?

Sorry if I sound like a spoil sport - just thinking out loud here ....

Best wishes

Per
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 15, 2021, 09:55:46 PM
Gentlemen -

Thank you so much for all your input.

@ Jason - on your point about the valve: It may be that a longer lift than it currently allows would help. I'm not sure, as I wasn't looking for that today. I have a feeling that perhaps I'm getting enough lift but I can explore that a bit tomorrow. I'm sure you're right that the valve could be modified if needs be, or indeed I could have a go at making one.

On the viton ring - yes, that's the trouble. I'm not sure that the saving in pressure would compensate for the additional friction. However, as you say I can always experiment as even a groove may help if the ring doesn't. I guess I could always play around with graphite yarn too...

And thanks for the PM - will reply separately.


@ Chris - I have used some nice additive-free oil used to lubricate gardening machinery, and some thick, gloopy old steam cylinder oil in various combinations. Unfortunately without much success in terms of performance. In fact the steam oil adds drag and makes it worse! That's how bad it is. My sense is that the thinner oil is better for now, given this is a test situation. So yes, a groove will be good for that as well as to reduce steam escape.


@ Per - thanks for dropping by. This kind of design has produced at least this runner...

895q7D6v_84
... but it isn't scaled up like mine is. They say it's hard to scale nature.

The weight of the piston has been on my mind from the outset, having realised it would be heavy but - as a complete novice - not knowing what the tolerances in such things are or what to expect, I thought I'd try it as it is initially. I'm pretty sure I could cut a big slot in the back part of the piston (positioned so that it would not interfere with the exhaust events) which would reduce the weight while still keeping the piston long enough to avoid the need for a crosshead guide. I guess that might help a bit.

On the exhaust ports - there are actually two - one opposite the other. I'd probably go down the route of drilling additional ports rather than enlarge the existing - again something which I am aware I may need to do.

But you do not sound like a spoilsport! There's nothing wrong with a bit of realism. I will give this engine my best shot, but equally I don't want to spend the rest of my life struggling with it either. If it turns out to be a dead duck, I could always convert it to a mill engine - which would be another learning curve and another set of issues to grapple with!

Meanwhile, I need to have a closer look at that piston and cylinder and see if there are ways in which I can reduce that steam leak.


And finally guys - the garage where we take our van and car to be serviced is owned by a man who has a collection of model steam engines! So given he will be sympathetic I'm tempted to take this engine round there and ask him to hook it up to their airline and see what it does on some serious pressure...

Is that worth a try...?
Title: Re: A Simple Uniflow Engine
Post by: propforward on January 15, 2021, 10:43:46 PM
I admire your perseverance Gary. I don't think there's any harm in attempting to run on a bit higher air pressure - within sensible limits of course.
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on January 15, 2021, 10:51:10 PM
Hi Gary, good to see a successful engine on the design.  Interesting to note that despite the symmetry, it seems to run better in one direction than the other.  Manufacturing tolerances I suppose.  He did seem to be using a very small compressor, very encouraging.

So onward with the original design.  I know you have gone bigger but there is really nothing magic about the original size.  Start with the designers intended arrangement, and only change what doesnít work.

Speaking of which, clearly the design intent is that the piston provides a reasonable seal before the exhaust ports open.  So that needs to be attended to if it is leaking badly.

I would be concerned about rings or packings of any kind as they will likely be damaged as they cross the exhaust ports.  So I would suggest grooves.  You have plenty of length for several for a good labyrinth effect, and they will collect some oil, so improve the seal one way or the other.

Clearly, simple is a misnomer when it comes to understanding this little beast.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 16, 2021, 12:06:09 AM
@ Stuart -
Thank you sir. It's either perseverance or failure. If  I have to accept the latter I will, and call it a learning experience and lots of nice machined parts to customise for another engine.
But I'm not there yet, so perseverance it is...
I may well look to the garage airline if it doesn't work when I have tried everything else.

@ MJM -
Your point about scale is encouraging.  :ThumbsUp:
I know I often make observations retrospectively. When one is new to an area of knowledge one often intuits something but struggles to articulate it until someone more experienced does. So yes, it had occurred to me that erosion from these ports could bugger up rings!
I don't think the leak is catastrophic. Significant maybe, but hopefully not irredeemable. So I googled ( actually Duck Duck Go'ed, which doesn't exactly trip off the tongue) 'labyrinth piston grooves' and what I found was a series of concentric grooves creating a 'labyrinth' effect, as opposed to  what I imagined, i.e. a maze-like system of intersecting grooves.   :)
Is concentric grooves near the head of the piston what you meant?

And yes - simple in terms of parts machining; not so simple in coming to terms with the dynamics...


You guys are amazing. Without you I'd be despairing right now.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 16, 2021, 08:05:41 PM
Sitting in a bar for an early evening libation with my lovely lady this evening and I had a realisation.  :wine1:  :NewBrain:

If the steam leak around the piston is caused by a taper in the cylinder and can't be fixed by other means such as grooves in the piston, I could always try turning the cylinder round. All I'd need to do would be to drill and tap a bolt circle for the cap on the other end of the cylinder, and maybe plug the existing exhaust ports and drill new ones. If that worked, the rest would be cosmetic.

I'm a bit ahead of myself here and there are a couple of steps in between but at least it puts another option on the table to try if the other interventions don't fix things.
Title: Re: A Simple Uniflow Engine
Post by: crueby on January 16, 2021, 08:29:40 PM
Great that the drink loosened up the brain cells, but how much of her conversation did you miss while your brain drifted off to the shop? Hope no bar-stool-to-the-head repercusions...!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 17, 2021, 12:45:47 AM
Glad to tell you that she extremely tolerant and indulgent of my meanderings, ramblings and obsessions.

Lucky for me, I have to say...

 ;)
Title: Re: A Simple Uniflow Engine
Post by: Zephyrin on January 17, 2021, 09:50:23 AM
Hi,
it is often said that we cannot reduce the laws of physics to the scale of models, but it is true in the other direction too! I do not see this enormous piston moving lightly in a breath of air, not only the weight, but the dragging force on such surfaces too.

And yes, i agree, the exhaust port is much too small.
it seems to me that a uniflow engine (flash steam engine) works best with a large intake advance...

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 17, 2021, 11:04:32 AM
Hi Zephyrin -

Thanks for your honest view.

I appreciate that you may be correct.

However, I intend to persevere for the time being. Even before making the piston the possibility of having to remove some of its mass has been in my mind. It should be possible to do so by cutting one or more holes or slots which could also have the effect of reducing surface drag. The only criteria would be that it would not interfere with the exhaust action and that it would still have the length and rigidity to avoid the need for a crosshead guide. I accept that this may or may not be enough to make a difference, but there's only one way to find out...

Enlarging the exhaust ports (there are currently 2) or - more likely - drilling extra ones is no problem and is already on my 'to do' list.

My aim is to run the engine on steam rather than air (if it will run at all), and a flash steam boiler could be an option though the one I have started (in another thread) may possibly need a bigger coil to have a chance of running this.

Your point about a larger intake advance: in my position as a rank beginner I don't know what this means, so clearly I'll have to look into that. All guidance is welcome!

I'm not ignoring what you are saying, but having come this far it would be wrong to give up at this point or I would always wonder... so I'll carry on until every option has been explored. If at that point it won't run, even on flash steam, then at least I'll have learned a heck of a lot and will then have quite a few pre-made parts to use in future projects...

 :ThumbsUp:

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 17, 2021, 10:46:48 PM
 :cartwheel:

YPQMvaLH0Sk
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 17, 2021, 11:28:02 PM
 :pinkelephant:

Well, I wasn't expecting that!

It ran for a good two minutes or more, and when it finally petered out I did not get the feeling that it reflected issues in the engine per se. My sense is that either my budget compressor was having trouble keeping up, and/or the temporary pin was changing length due to just being threaded into the piston with nothing to lock it. Or both. However, if any of you think it may be otherwise, please feel free to say.

There are clearly changes and refinements to be made from this point on, but I think I can say the engine runs...

I made only two changes. Following MJM's advice I cut some grooves in the piston:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/886731.jpg)

These made a significant difference - the piston ran more freely and with some thick steam oil in the grooves there was hardly any air leaking from the exhaust ports. I was a little worried because I had used my only remaining decent parting off tool to cut these grooves and they are not far short of 3mm wide. I thought maybe I had overdone it but it would seem not. Later, I may experiment with some graphite yarn in the grooves but for now this is good.

The other change was made in response to a point made above by Jason, who wondered if the valve was getting enough lift. So I lengthened the valve by unscrewing it then making a spacer from brass which was tapped with a thread to match the valve. This made the valve 2 or 3 mm longer and gave the ball that much extra travel:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/886734.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/886733.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/886732.jpg)

What I did not do was reverse the cylinder, enlarge or add to the ports or remove metal from the piston to make it lighter. some of these things can be considered again a bit further down the line.

There will be many refinements and changes to make (including I suspect seriously enlarging the brass flywheels with steel rims so I can put that lathe chuck back on the lathe where it belongs).

Following another point made by MJM, I noticed that the crankshaft was indeed taking some punishment so in keeping with his suggestion I'm going to move the flywheels outboard of the frame to reduce the length of the centre section of the shaft. This will probably look better anyway, given that the frame as it presently is looks very wide. I don't think the crankshaft got bent in this run. I certainly hope it didn't but even if it did, making a new one at this point wouldn't seem like that much of a big deal now that this looks like it's going somewhere.

I may not have a lot of shop time this week, as I'll be busy with work, but at least I know that when I do get back to it I'll be moving on to a new - and very interesting - stage of the build.

Thanks so much for all your advice and encouragement so far.

 :LittleAngel:
Title: Re: A Simple Uniflow Engine
Post by: crueby on January 17, 2021, 11:47:05 PM
Awesome!!!    :whoohoo: :pinkelephant: :cartwheel:

If it indeed is the pin unscrewing (one way or the other), at least that is an easy adjustment. For things like that I like to install it with a drop of blue loctite, which will allow it to be adjusted while keeping enough friction on it to keep it from moving again. Unless there is room on the top of the piston for a lock nut without the nut hitting the end of the cylinder? That would be even easier.

Great that it got going, now you know its just fine tuning!   :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 17, 2021, 11:59:44 PM
Cheers Chris!   :cheers:

I have some blue loctite and was wondering if it might work in that way... and alternatively I haven't checked yet to see if there's room for a locknut but I suspect there probably is.

In any case, I can come back to that later, as now I know it runs the next step is to dismantle the test rig and work towards the final setup. Still quite a lot of work to go, but it will be happy work now that  he 'will it even run?' anxiety has passed.

Can't wait to run it on steam when the time comes...

 :ThumbsUp: :ThumbsUp: :ThumbsUp:

Title: Re: A Simple Uniflow Engine
Post by: propforward on January 18, 2021, 12:04:20 AM
That's great Gary! What a great runner too - a joy to see it romping along!  :NotWorthy:

I'll enjoy watching progress as you fine tune it.  :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 18, 2021, 12:06:00 AM
Thank you Stuart!

 :LittleAngel:
Title: Re: A Simple Uniflow Engine
Post by: Kim on January 18, 2021, 05:28:48 AM
Congratulations, Gary!  It really runs well!  :ThumbsUp: :popcorn:
Kim
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on January 18, 2021, 06:01:06 AM
Hi Gary, congratulations, a great result.

As you say, now the fine tuning.  But first sit back and enjoy the success.  Great to know that there is nothing really wrong, and those first adjustments were successful.

Unfortunately I now see why everyone is talking about disappearing videos.  As already said, options are limited on an iPad despite regularly taking my tablets on time every time.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: Zephyrin on January 18, 2021, 07:29:41 AM
congratulations, bravo for your perseverance !
the flywheel looks hefty too !
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on January 18, 2021, 07:39:39 AM
Well that will save me having to try and sort out the poor original design for you :) Things can only get better now.

I'd asked Gary to send me the drawing so I could give him the angles that the inlet and exhaust open and close at but the drawing gives no length for the conrod so it's guess work as to how close the piston gets to the head and therefor how much it has to compress any remaining air/steam. At the other end there is no way of knowing when the exhaust starts to get uncovered.

Video here (https://www.youtube.com/watch?v=YPQMvaLH0Sk) for those still having problems viewing
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on January 18, 2021, 08:35:11 AM
Hi Jason, thanks for posting that link.  Great to see it running nicely.

MJM460
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 18, 2021, 09:20:34 AM
Thank you all - much appreciated.

@ Zephyrin - yes! The lathe chuck will disappear and I'll be rummaging in the scrap bin at the local machine shop looking for a couple of steel discs to beef up the existing flywheels.

@ Jason - yes, I guess it saves you a job! But many thanks for the offer anyway, and for posting the link to the video.

@ MJM - as you are probably aware, it'd due to a privacy setting in your own browser, as pointed out by Kim above.

It occurs to me that another reason for the engine stopping after 2 minutes or so could be because of the grooves losing steam oil steam over that period of time and causing a loss of pressure. If so, that would point to further work on the piston/cylinder. However, I'll come back to that later if it remains an issue. Having more work to do on specific areas feels much less onerous now that I know the engine will run.

 :ThumbsUp: :ThumbsUp: :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 18, 2021, 11:41:41 PM
And so beginneth this very eve the dismantlement of the test rig, in anticipation of the first steps upon the still long road towards the engine in its finished form. No pix.

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 19, 2021, 11:44:29 PM
Dismantling the test rig:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/886934.jpg)

Now, following a point made by MJM about how the long central section of the crankshaft could be liable to bending under the force from the connecting rod, it did occur to me that the crankshaft took quite a pounding when the engine was running. So this is the new configuration:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/886933.jpg)

I also think it looks better - the narrower frame will make the engine look leaner and meaner, and it also makes much more sense to have the pulleys outboard of the frame so that the whole thing doesn't need to be dismantled every time I want to put on or take off a belt.

The bad news is that the crankshaft is indeed bent. Stuck it in the lathe chuck and the runout was clearly visible. To be honest, I think it was bent before the test run, and that I was in denial mode at the time. It may or may not have been bent a little more by the test run but that's academic. So... I'll just have to make a new one. I may even make two in parallel; one loctited and the other silver soldered, and see how I get on. The prospect isn't too daunting at this stage, to be honest. But not yet! I now plan to get on and work towards the finished engine - the replacement crankshaft can be made as one of the last jobs of the build.

Onwards and (hopefully) upwards!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 20, 2021, 10:17:12 PM
I have a question: when I get back to making a replacement crankshaft, should I use precision ground mild steel or silver steel for the shaft itself? Or is is six and two threes?

These are the UK names for these steels, anyway - not sure if it's the same elsewhere.
Title: Re: A Simple Uniflow Engine
Post by: Jasonb on January 21, 2021, 07:37:52 AM
I generally use PGMS when building up a crankshaft. M-Machine pack it better than other suppliers.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 21, 2021, 01:19:53 PM
Great thanks Jason.
Will check them out for PGMS.

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 25, 2021, 10:16:39 PM
Bringing to dimension and squaring off the edges of the base plate in the mill:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/887389.jpg)

Haven't got much done in recent days as we have been somewhat overtaken by  events here. The small island on which I live went overnight on Friday from having been extremely well controlled for months, and life apparently back to normal, into a second hard lockdown following an unexpected spike in community-seeded covid cases.

Lots to organize, arrangements to make, meetings to reschedule... and while this is clearly a dark cloud that no-one wanted, the silver lining for me will be quite a bit of extra shop time over the next few weeks. If it's possible to find a little bit of positivity in a negative situation, then I say do so.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 28, 2021, 10:39:21 PM
Not very exciting stuff really, but...

... With one of the long sides of the base plate milled to a clean edge, the other edge was marked using a combination square. This left a narrow strip of uneven width between the rough-sawn edge of the plate and the scribed line. Rather than spend ages milling it down to the line, I decided to chain drill it and remove most of the metal that way. Because the strip was of uneven width I used a step drill to be able to optimise the size of the hole at any given point without having to change drill bits. The floorstanding drill press (which has been converted to 3-phase with variable speed and runs like a dream) made short work of this:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/887710.jpg)

The swivelling action of the bench vice was ideal for holding the plate for hacksawing between the holes:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/887709.jpg)

That done, the base plate is now back in the mill and clocked in. A couple of passes were taken before I called it a day, and the second edge should be clean and parallel to the first tomorrow or the day after.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on January 31, 2021, 11:15:26 PM
The baseplate has been squared up in the mill and the two sides offered up to get a sense of the layout. Because of the bend in the original crankshaft I have reverted to a piece of round bar of the same diameter to guide alignment of the frame sides on the baseplate:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/888019.jpg)

Once one side was aligned it was clamped  with toolmaker's clamps and taken to the mill to spot the holes in the frame support bars (aluminium angle) on to the base plate. A wiggler/wobbler/centre finder/whatever it's called with a ball end was used in the mill to locate the holes:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/888020.jpg)

That done, one side of the frame (still in the form of a blank) was fixed to the baseplate. All fixing hardware remains temporary at this point:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/888021.jpg)
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 01, 2021, 11:13:42 PM
The frame is now assembled in very basic form, with the two sides (which are still blanks due to be shaped later) attached to the base:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/888148.jpg)

Since the crankshaft is now a reject due to being bent, I just used some 12mm round bar to test the alignment, with a drill chuck attached to the end to make it easier to manipulate. It was hard to turn the shaft and at first I thought that the alignment was out, but then I realised that the sides are leaning inwards at the top to the tune of just over a milimetre. Pushing the sides apart at the top made it easier to turn the shaft. To remedy this I'll add two or three cross-braces between the frame sides at the top. These will widen the gap between the sides at the top, and will also make the structure more rigid.

Don't be confused by the belts and pulleys you can see in the photo - I just sat the assembly on top of the belt sander attachment of my woodturning lathe to take the picture.
Title: Re: A Simple Uniflow Engine
Post by: propforward on February 01, 2021, 11:18:38 PM
Looking good Gary! It's all progress.  :ThumbsUp: :ThumbsUp:

Those step drills are kind of fun. They definitely have their place, and it looks like you put it to good work.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 01, 2021, 11:27:42 PM
Thanks Stuart.

Yes - I don't use the step drills very often, but they were good in this application.

Forgot to mention that I now have a leak in my home workshop roof here in Guernsey! It's just a shed, but I'm a bit mystified because I just gave the roof a new coat of very sticky fibreglass stuff last Summer. It really shouldn't be leaking already, but it is... and now we're back in lockdown again here I can't go out and buy more of the stuff at this point in time. Fortunately the leak is just above an area of open floor, so a bucket under it will suffice for now. Not a good feeling though.

Never a dull moment...

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 02, 2021, 11:50:59 PM
Three cross-braces were made from aluminium round bar, each marked out with the surface plate and height gauge to a length corresponding to the distance between the inside faces of the frame sides at the bottom of the frame and turned to length on the lathe. The braces at each end of the frame were drilled, tapped and fixed by screws via holes which were pre-drilled in the frame sides. The one in the middle is just wedged into position:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/888268.jpg)

Together, these push the sides of the frame out sufficiently to bring them into parallel with each other. As a result, the test shaft rotates freely in the bearings, which with a little running in should allow the new crankshaft to turn just fine. A satisfying evening's endeavours.

The cross-braces will be kept when the frame sides are cut to a hopefully more elegant shape, and repositioned to do the same job as they are doing now.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 04, 2021, 11:49:27 PM
Starting on the structures which will anchor the cylinder in the engine frame.

Two lengths of 32mm aluminium round bar were cut to make cylinder support pillars. The pipe jaws on the vice are great for this kind of job:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/888475.jpg)

These were turned to length and drilled through with a 6mm clearance hole. They raise the cylinder so that the centre of the bore is at the same height as the centre of the crankshaft. Long M6 screws or studs will pass through the base plate, up through these pillars and will be screwed into blind tapped holes in the bottom wall of the cylinder. For aesthetic reasons I want the cylinder to sit horizontally rather than at an angle so that requires it to be raised up:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/888476.jpg)

I know this makes the cylinder sit quite high. This is because the crankshaft also sits quite high in the frame in order to be able to accommodate the flywheels. With only the two support pillars the cylinder wouldn't be anchored rigidly enough, so the plan is to bring in two cross-braces from each side of the frame to the corresponding side of the cylinder wall, again threaded into blind tapped holes. I suspect that arrangement will hold the cylinder firm, but if it doesn't I'll consider additional ways to secure it.

Meanwhile, here is the cylinder on its support pillars rougfhly positioned inside the frame, just to give an idea...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/888477.jpg)

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 06, 2021, 11:32:54 PM
Four cross-braces for the cylinder were turned to length from aluminium round bar. They will be drilled through with 6mm clearance holes and with M6 screws or studs will secure the cylinder at four points to the frame sides. Here is a lashup of them with no fixings:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/888593.jpg)

Even with them just wedged into the frame like this the cylinder sits pretty solidly in position. The braces are located two fore and two aft of the exhaust ports, so no interference there. Fingers crossed that when secured with fixings the whole assembly will be stable enough when the engine is running. I suspect it will be, but if it isn't I'll just have to find a way to add more anchoring elements.
Title: Re: A Simple Uniflow Engine
Post by: crueby on February 06, 2021, 11:44:07 PM
Looking good!  Will the side panels have designs pierced through them?


 :popcorn: :popcorn: :popcorn:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 06, 2021, 11:49:27 PM
Thanks Chris.

They will be cut to a curved shape and will have round holes of various sizes drilled through. I'd get into triangular holes etc. if I had CNC, but I don't. I suppose I could mill them in the conventional manner but it would be a long haul and risky of errors. Round holes will be fine this time though.

Hope to have CNC one day, but don't have it yet...

Cheers...

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: crueby on February 07, 2021, 12:01:58 AM
I did some clock plates once with angled and triangular holes, trick was to drill the corners first, and clamp the plates to a tooling plate on the rotary table to line up the sides of the openings for milling, like doing spokes on a gear or flywheel. The design you describe sounds like it will look great!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 07, 2021, 12:08:45 AM
Thanks Chris.

Yeah, I thought that it would be that kind of process.

I reckon the round holes will be ok for this engine, though you never know - I might decide to give it a go...
Title: Re: A Simple Uniflow Engine
Post by: crueby on February 07, 2021, 12:30:02 AM
Thanks Chris.

Yeah, I thought that it would be that kind of process.

I reckon the round holes will be ok for this engine, though you never know - I might decide to give it a go...
Good technique to practice on some scrap first.   :cheers:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 07, 2021, 10:11:53 AM

Good technique to practice on some scrap first.   :cheers:

Absolutely! But thinking more about it, I reckon round holes will do for this one...

 :cheers:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 09, 2021, 12:26:07 AM
Deja vu time.

Started working on the replacement crankshaft. The previous one was out of true because - if I remember rightly - I caught the end of it with a lathe tool.

Not that I really want to be repeating steps, but needs must. I chose two nice straight 12 inch pieces of 12mm precision ground mild steel, one for the shaft and one for the journal. The one for the journal will be kept long initially to test the parallelism of the holes in the webs, i.e. if the two bars are parallel when the webs are in situ then the holes are too (sorry - I'm sure you're well aware of that).

The photo below is of centre-drilling a small cone-shaped hole in the end of what will be the crankshaft to enable tailstock support at a later stage. It's not something you haven't seen a million times before but I find myself liking the photo for the motion blur on the end of the shaft and the lovely green colour of the cutting oil...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/888757.jpg)

Two pieces of rectangular EN3B steel were then cut for the webs. I was thinking of maybe silver soldering this crankshaft, but have decided to just use Loctite and pins again rather than venture into unknown territory at this stage. Silver soldering a crankshaft is hopefully something I'll have plenty of opportunities to try in the future.

 
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 09, 2021, 10:12:05 PM
A little more progress on the crankshaft remake this evening.

Blanks for the webs milled square, superglued together and left in the vice for tomorrow and a final truing up, rounding of the corners, and drilling and reaming the holes for the crankshaft and journal.

I won't bore you with a photo of two small rectangles of steel held in a vice, but basically I'm making this new crankshaft the same way as I made to old one (page 6 of this thread).
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 15, 2021, 11:33:21 PM
While giving the loctite on the new crankshaft extra time to set due to the cold, damp weather, I turned my attention to other things. This photo shows the approximate positions of the cylinder support pillars and the cylinder cross-braces:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889123.jpg)

Note that the cross-braces are higher than the centre line of the cylinder to increase the stability of the structure. The black flecks inside the cylinder are just bits of sawdust from another project - I swept up what I could, but after a certain point it's diminishing returns, especially after the sawdust gets oily and gets everywhere! The height of the cross braces was marked on the end of the cylinder.

The positions of the support pillars and cross-braces were then marked out on the cylinder using the surface plate and height gauge. The picture below shows the cylinder upside down, with the support pillars roughly in position:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889124.jpg)

The support pillars and cross-braces will all be drilled through with clearance holes for long M6 screws which will pass through the bottom and sides of the engine frame, through the pillars/braces, and into blind tapped holes in the cylinder wall. Lining all this up will be a challenge - I think transfer screws will be used for much of it. I then had to pause on this step because I'm waiting for the M6 screws (plus a drill and tap) to arrive in the post. A gratuitous shot of my bench showing the state of play follows:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889125.jpg)

I then started on a new flywheel. I'm pretty sure that the original brass flywheels are too light to run the engine. On the test rig I only got it going after I put my 4-jaw self-centring chuck on the end of the crankshaft. It may or may not be that one of the original flywheels still has a part to play, but clearly something heavier is needed. I had originally intended for this engine to be symmetrical, with twin flywheels, but that would have necessitated a trip to the local machine shop to rummage in the scrap bin and we are now back in lockdown here so I decided to use what I already have.

I surreptitiously borrowed the kitchen scales and weighed the 4-jaw chuck, which came in at 4 kilos:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889126.jpg)

It may be that the new flywheel doesn't have to be quite as heavy as that, but it gave me somewhere to start. I found a disc of EN8 steel which I have had for ages - it weighed 3.7 kilos. Some of this will be lost in machining, so I also selected a smaller piece of some other kind of steel, which weighs 1 kilo. If necessary, the two pieces can be combined in some way:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889128.jpg)

The good thing about the piece of EN8 is that it already has a spigot on it which made it very easy to mount in the 3-jaw chuck:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889127.jpg)

The plan is to face one side and even up the perimeter in the 3-jaw, then drill and ream it 12mm and turn the other side on a short mandrel made of the same diameter of steel as the crankshaft. This is as far as I got before calling it a night:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889129.jpg)

Cheers,

gary
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 17, 2021, 11:47:37 PM
As the second application of loctite continued to set on the new crankshaft, I carried on with the new flywheel:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889248.jpg)

Fortunately the piece of EN8 that I'm using came with a pre-machined boss on each side, and even the shallower of the two allowed me to hold it in the 3-jaw, so I was able to take the initial cuts on both faces plus the edge:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889247.jpg)

The plan is to use the other, smaller piece of steel to make an extended boss on the flywheel:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889249.jpg)

I'll attach it via a circle of M6 cap head screws with the holes counterbored for the heads. If the whole arrangement is too heavy it will be easy enough to reduce the weight by turning down, facing and/or drilling a circle of holes. I'll be very lucky if I don't have to do some final truing up on a mandrel to eliminate wobble. The trouble with that is that it tends to invite chatter.

Finally, a quick mock-up just to give an idea of the look of the flywheel mounted on the engine:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889250.jpg)

This will enable me to make final decisions from an aesthetic point of view about what shape the frame will be. In fact I'll probably just stick with my original template but I didn't want to commit until I had an idea of how big the final flywheel would be.
Title: Re: A Simple Uniflow Engine
Post by: crueby on February 17, 2021, 11:53:03 PM
 :ThumbsUp: :popcorn: :popcorn:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 17, 2021, 11:55:59 PM
 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 18, 2021, 11:37:38 PM
Here are the basic forms of the main part of the new flywheel and its boss:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889294.jpg)

They are sitting in front of the milling vice which is holding a hexagonal ER32 collet block which I was thinking of using to drill a 6-hole bolt circle with the collet holding a 'superglue arbour' because the rotary table with chuck didn't leave enough room in the mill. However, I have decided instead to use the DRO to make the bolt circle to enable more stable workholding and to stick to the original idea of five-hole patterns as a feature of this engine. I have never used the DRO for this before so it will be a learning experience for me.

The plan is to make a circle of clearance holes in the main wheel for M6 cap head screws. These will be counterbored so that the screw heads will be just below the surface of the wheel. A matching pattern of blind holes will be drilled in the boss and tapped M6. This will allow the main wheel and the boss to be bolted together. The assembly will then be chucked in the lathe and the diameter of the boss reduced to match the existing raised section on the main wheel. After that, further machining can be done to reduce the weight if required.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 22, 2021, 10:51:05 PM
Having thought about it I decided that M6 may be too flimsy for the screws which will hold the two parts of the flywheel together, so I rummaged through my 'miscellaneous' box (well, through one of them) and found five M10 stainless cap head screws:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889542.jpg)

Nice and chunky!

Now, as this was my first time using the DRO to make a pitch circle, just to be on the safe side I put a marker pen into the drill chuck and marked out the hole positions with it using the DRO:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889541.jpg)

This looked good to me, so I went round again with a small centre drill to make marks that would be insoluble in cutting oil  :) . Unnecessary really, but better safe than sorry:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889540.jpg)

The holes were then drilled using a larger centre drill and three drill bits to take them up to size. I found it more efficient to leave the table in position and swap the drills for one hole at a time than to go round all of the holes with each bit before swapping them:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889544.jpg)

A test fit of the screws:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889543.jpg)

The holes will be counterbored and the screw heads will sit 2mm beneath the surface of the wheel. However, I have in my possession neither a counterbore nor an endmill of  an appropriate size, so I am waiting for the mail before continuing with this part. Although the DRO would let me break down the setup, use the mill for something else and then set up again, I'd rather leave it undisturbed.

I appreciate that the content of this post may be old hat to many of you, but this was a first for me and I found using the DRO to make a pitch circle to be an absolute dream.

I am converted...

Title: Re: A Simple Uniflow Engine
Post by: crueby on February 23, 2021, 12:15:03 AM
Came out well!  And I agree, leave the setup till all the operations are done, always best.


 :popcorn: :popcorn: :popcorn:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 23, 2021, 10:25:21 AM
Thanks Chris.

Hope that counterbore arrives soon!
Title: Re: A Simple Uniflow Engine
Post by: propforward on February 23, 2021, 11:24:58 AM
Looking good Gary. Itís maddening waiting for a tool when you want to just crack on - but I admire your patience. Definitely best to leave the part set up. Nice job as always.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 25, 2021, 12:26:10 AM
Thanks Stuart.

Yes, it can be frustrating, but this week I seem to have plenty of other things to do, so as long as the post isn't too slow it will be ok. Am looking forward to continuing with it though - this flywheel is quite fun so far.

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 25, 2021, 01:54:09 PM
Some endmills arrived today but I reckon I'll hold out for the counterbore...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on February 26, 2021, 07:38:58 PM
G'dang!

The counterbore arrived today but the guide section on it is too big for the holes!

I thought that might happen, which is why I bought the endmills alongside. I'll just use one of them. Everything will be locked down tight so the counterbores they make *should* remain centred on the holes.

I don't want to open up the holes just to accept the counterbore guide as the screws make a neat fit in them as they are and I'd rather keep it that way...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 02, 2021, 12:18:28 AM
The counterbore which I didn't use as the guide was too big for the holes:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889961.jpg)

An endmill was used instead, which went ok (screws dropped in as I went along, to confirm the depth):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889960.jpg)

I used a piece of the same steel as used for the crankshaft as a gauge to locate the bore of the flywheel before taking down the setup. It's a nice bearing fit so I hoped it would be accurate enough. This was in order to keep the DRO at the same setting to make a corresponding bolt circle on the flywheel boss. To be honest I'd have been better just taking a note of the co-ordinates of the centre. Ah well...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889959.jpg)

The completed counterbores, just visible here:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889964.jpg)

The machining marks that are visible here look worse in the photo than in actuality. However, I will try to deal with these later.

The back of the flywheel, showing the M10 bolts protruding to attach the boss:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889963.jpg)

I couldn't resist another quick mockup of the unfinished flywheel on the unfinished engine frame:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889962.jpg)

The boss was then set up in the milling vice with its centre located using the same piece of bar as a gauge. Five holes were centre-drilled, drilled and tapped M10 using the same pitch circle setting on the DRO. The depth of these holes was measured in order that they would be blind but long enough to accommodate the screws. The photos of the drilling and tapping all came out blurry, so here's one of the initial centre-drilling. Nothing too exciting, I know, but all part of the process:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889967.jpg)

And then the moment of truth. I had tried to be careful so that no inaccuracies would creep in, but while I hoped this would be the case I did not expect it. Actually, I was fairly pleasantly surprised. On assembly, some of the screws were very tight and I thought I may have to widen the holes through the main flywheel to create some wiggle room. However, with a bit of perseverance they all went in, and to depth. There was a bit of inaccuracy, however. I found that in order to carry out the assembly, it helped to have a short piece of bar through the bore of both components. By the time the screws were tight, however, the bar was pretty well clamped due to a very slight misalignment between the bores. Some inaccuracy had indeed crept in. Overall, though, it's not a great deal and I suspect a pass with the reamer will sort it out. Or even better maybe take it apart, rotate the boss and reassemble a few times to see if there's one position that works best. I'm actually quite pleased with it as I was half-expecting it to be a whole lot worse. The joys of the DRO! The boss will still have to be turned down and probably also given another light facing cut. I aim to do this with the parts assembled, and I guess it can be treated a bit like a casting at this point:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889966.jpg)

Finally, the wheel was chucked in the 3-jaw, held by the shallow raised section on the front side of it:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/889965.jpg)

 There is a slight wobble and at this stage (which is where I left it for the night) I think that's largely down to the workholding. I don't think the 3-jaw is the way to go with this. The ER32 collet chuck and a superglued arbour may be better, but I need to sort out that slight misalignment in the bores first.



Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 02, 2021, 11:51:39 PM
So... I tried rotating the boss step by step and bolting it to the wheel in all five different alignments to see if any position would allow me to pass a length of the shaft material through the bore of the wheel/boss assembly:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890037.jpg) 

No joy. The shaft slips in neatly from the wheel side and the boss side but in either case it stops at the point where the wheel and boss meet. I returned it to what I feel may be the optimal position and the misalignment looks very slight - I suspect a reamer from the front of the wheel will sort out the bore. If this works it will put the bore of the boss slightly out of shape but it should leave the bore of the wheel part intact and as that will be the longer section of bore the whole thing *should* still run true on the shaft.

However, first I need to get the outside of the boss turned down to diameter in situ on the wheel. I took a short piece of shaft and superglued it into the flywheel to make an arbour:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890038.jpg)

This will be left to cure overnight and then held in the ER32 collet chuck so that the boss can be turned down to size and faced. The wheel is heavy and there will be a lot of shearing force on that glued join so I'll have to go very gently, especially as there are currently a couple of rogue notches on the outer surface of the boss which will in effect give me an interrupted cut initially. If the superglue arbour doesn't hold I'll have to try it another way. If it does, I'll be able to turn the boss down to size then reverse the assembly, hold it by the boss in the three jaw and ream the bore right through...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 04, 2021, 11:37:06 PM
With very careful turning I managed to true up the boss without breaking the join on the superglue arbour held in the ER32 collet chuck:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890132.jpg)

The problem (as described in the preceding post) is that there is a misalignment between the bores of the main part of the flywheel and the boss (which is on the right in the photo). The superglue arbour only reaches as far as the join between the flywheel and the boss - it will go no further. However, by turning down the boss in this setup I now have the outside diameter of the boss running concentrically with the superglue arbour and the bore of the main flywheel.

The next step is to remove the superglue arbour using heat, and hold the assembly by the boss in the three jaw. Here is a mockup of this with the arbour not yet removed:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890131.jpg)

The plan has worked so far, as the superglue arbour ran true in the mockup shown. My hope is that with the superglue arbour removed I'll be able to run the 12mm reamer through both components to create a continuous bore that will be concentric enough with the boss to function and run true. I appreciate that this may not happen - the existing misalignment could deflect the reamer and result in an irregular and unusable bore. If this happens, all is not lost - I'll open the bore up wide and put in a bush (maybe bronze) pre-bored to 12mm.

In any case, there is also currently a wobble on the widest part of the flywheel even with the bore centred. I'm not sure where that came from as I have somewhat lost track of the various steps I have taken. This is less of a concern because provided I get a decent bore through the whole assembly there is no shortage of material which can be removed in truing it all up.

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 09, 2021, 12:50:17 AM
The short superglue arbour was removed using heat:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890364.jpg)

The assembly was then mounted in the 3-jaw and the bore reamed right through to correct the misalignment between the main flywheel and the boss. This was a moment of truth, as if the misalignment was anything other than miniscule it wouldn't have worked. Fortunately the reamer went through with little resistance, suggesting that the misalignment was indeed tiny:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890363.jpg)

A piece of 12mm PGMS slid through nicely and showed no lateral play. The bore seems fine:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890366.jpg)

In theory, the bore was at this point concentric with the circumference of the boss, but there was a wobble on the main part of the wheel, so the assembly was again mounted in the 3-jaw for an initial rough truing up:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890365.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890368.jpg)

It was then mounted on a second superglue arbour, this time one which passed through the whole assembly:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890367.jpg)

This was allowed to cure overnight. The arbour was then mounted between the ER32 collet chuck and a revolving centre in the lathe tailstock, and the wobble was turned out of the front of the flywheel:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890369.jpg)

This done, the assembly was reversed and the back of the flywheel (including the boss) was also trued up:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890370.jpg)

Unfortunately a significant amount of chatter made its presence felt:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890372.jpg)

While this isn't wonderful, it is (honestly!) not as bad as it looks in the photo. Futhermore, it is mainly on the back of the flywheel and the boss, in which places it will be relatively hidden *if* I don't turn it off. That may depend on how true the wheel runs in its final position on the crankshaft. If it runs true, I may just leave it as overall the flywheel as a whole looks pretty presentable. If it needs further truing up, that may offer an opportunity to remove the chatter marks. In retrospect, I think the problem may have been due to a carbide insert getting blunt and rubbing instead of cutting. This was probably made worse by the fact that I had to angle the tool due to the diameter of the wheel stretching the capacity of my lathe.

Another factor is weight. The finished flywheel weighs in at a whisker or two below 4 kg - in other words, almost the same weight as the lathe chuck which served as a surrogate flywheel during the test setup and had the engine running. For that reason alone I'm reluctant to remove more weight from the wheel if I don't have to. Interestingly, machining the wheel removed approximately 0.8kg in the form of swarf. It was obvious that the machining would lose some mass, and that was why I was happy to start off with blanks whose combined weight was higher than my target of of 4kg. But the amount lost in swarf surpised me. You never really feel the weight of it in the form of swarf. I had been prepared to make a pitch circle of holes to reduce the flywheel's weight, but it appears that this won't be required.

The second superglue arbour was removed:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890371.jpg)

The flywheel was ten set up in the milling vice and the centre of the boss was located using an electronic edge finder and the half function of the DRO:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890374.jpg)

These gadgets make it effortless.   :)

This is quite a big flywheel so instead of a grub screw I'll be using an M6 cap head screw to secure it to the crankshaft. The position of the hole was centre drilled...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890373.jpg) 

Then drilled right through with the tapping drill:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890375.jpg)

The hole is stepped, and the section adjacent to the bore will be tapped M6. Above that, the hole has been widened to 10mm to give clearance to the head of the cap head screw. To do this I had to transfer the vice over to the floorstanding drill press as the length of the 10mm drill bit plus the height of the workpiece in the vice exceeded the capacity of the z axis of my small mill:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890376.jpg)

With the drilling done, the setup has been left in situ for tapping in the drill press tomorrow.

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 09, 2021, 11:09:04 PM
Tapping the boss M6 for the retaining screw (is that the correct term?) in the drill press using a piloted spindle tap wrench:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890426.jpg)

The stainless cap head screw sits neatly in the hole:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890425.jpg)

Mounted once again on a piece of 12mm PGMS with the screw tightened, it runs truer than I dared hope:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890424.jpg)

I'm very pleased with this flywheel in all respects apart from the machining marks in certain areas of its surface, and I'm calling it done for now. I don't want to carve away any more metal using a lathe tool, but am wondering how big a task it would be to polish the marks out using various grades of scotch-brite and/or wet and dry paper. If anyone looking in has any advice to offer on that (or any other abrasive that might work on EN8 steel without taking forever) I'd be grateful to hear it. Meanwhile, I need to top up my supply of scotch-brite and wet and dry anyway so I'll order some.

Next, though, on to another part of the build...

Title: Re: A Simple Uniflow Engine
Post by: john mills on March 09, 2021, 11:59:02 PM
Hi
Scotch brite wont remove much metal when i was working turning shafts the turner had 36 grit emery paper
for when he won'ted to remove metal .the finer grades will take a long time to remove much even a few thou
move on to finer grades to get a finer finish  try finer grit until you get the finish you want.
                John
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 10, 2021, 12:05:28 AM
That's great thanks John.

I will investigate that.

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: propforward on March 10, 2021, 02:58:38 AM
Looks great to me Gary, super job!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 11, 2021, 10:05:15 AM
Thanks Stuart. Very kind of you.

I'm pleased with it, but once I have seen it running true on the actual crankshaft I'll have a go at it with abrasives to try to get the machining marks out of it.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 16, 2021, 12:03:38 AM
On to the job of securing the cylinder to the frame.

The cylinder will be supported on the underside by two columns of round aluminium bar. These have already been drilled with a 6mm clearance hole through the centre. For each, a long M6 screw will pass through the base of the frame, up through the centre of the support column and fixed into a threaded blind hole on the outside of the cylinder.

Also, the cylinder will be anchored to the sides of the frame by four side braces - two on each side. These are thinner than the support columns but will be fixed in the same way.

Drilling the clearance holes through the side braces:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890765.jpg)

To install these columns and braces it was necessary to drill and tap six blind holes in the outer wall of the cylinder. This required quite a bit of care, as the last thing I wanted was to overshoot into the cylinder bore. In fact I erred on the side of caution, keeping the holes as shallow as I felt I realistically could. This meant that I had to optimise the amount of thread available in the holes for the screws to connect with, so the tooling sequence was centre drill, tapping drill for M6, 5 mm endmill to square the bottom of the hole, the usual three M6 taps and - to finish - an M6 tap ground square at the end to get a thread right into the bottom of the holes:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890761.jpg)

Tapping the hole for one of the the support column fixing screws in the drill press (as the mill doesn't have enough vertical clearance):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890760.jpg)

A fiddly marking out operation ensued for the position of the holes in the base of the frame for the cylinder support column fixing screws. I knew the distance between the face of the cylinder and the centre line of the crankshaft, so this was easy enough to measure and mark on the base of the frame. The cylinder was then aligned with this, allowing me to scribe the position of the back of it on the base as a visual reference. I then spent ages searching my shop for pieces of stock which could be used as guides to locate the cylinder centrally on the base in a lateral direction, finally settling on a parallel plus a piece of plastic bar  (visible in the photo) on each side to create a sliding fit between the cylinder and the frame support bars. Together, these steps enabled me to place the cylinder directly on to the base but in the correct position. Transfer screws were then put in the two threaded holes on the cylinder base. These can be seen at the bottom of the picture below. Ideally they shouldn't have stuck out so far but they wouldn't go in any further due to the shallow depth of the holes. However, with care it was possible to mark out the hole positions by holding the cylinder between the guides and carefully making a rocking, side-to-side scratching motion:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890762.jpg)

Al that was needed was to then scribe the centre line of the base to intersect with the marks made by the transfer screws:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890764.jpg)

The base was then transferred to the mill and clocked in:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890766.jpg)

The holes were drilled, using the DRO to double-check that the distance between them was the same as that between the two holes in the cylinder:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890767.jpg)

So, drilling these two holes was an evening's work. To be fair, they are important holes.

Aren't they all, though...?
Title: Re: A Simple Uniflow Engine
Post by: crueby on March 16, 2021, 12:15:24 AM
Great sequence and planning. And drilling towards the cylinder is always scary!


 :popcorn: :popcorn: :popcorn:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 16, 2021, 12:25:56 AM
Thank you Chris.

Scary indeed! The prospect of having to bore and otherwise machine a whole new piece of cast iron if things went wrong kept me on my toes though!

Doesn't bear thinking about...!   :o
Title: Re: A Simple Uniflow Engine
Post by: propforward on March 16, 2021, 04:19:35 PM
Well planned, and very well executed I would say Gary. It worked out very well for you. Great progress.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 18, 2021, 10:27:13 PM
Thank you Stuart!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 19, 2021, 12:01:23 AM
The cylinder and its support columns were bolted to the base:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890950.jpg)

The assembly feels completely rigid, which was a pleasant surprise given that the support columns are quite long. It needs to be rigid, though, given the weight of the piston and the probably high speed of the engine, so the cylinder side braces will further stabilize the structure. For this, clearance holes will have to be made in the frame sides. The approach will be similar to that used in marking and drilling the base for the support columns. Transfer screws were placed in the two blind holes in one side of the cylinder:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890946.jpg)

One of the frame support bars was reversed and fixed to one of the frame sides the wrong way round so that the frame side could be slid right up to the cylinder unimpeded. The appropriate area of the frame side was blued up:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890945.jpg)

With the base acting as quite a nice surface plate, the frame side was moved up towards the transfer screws. With the frame sides bolted to the frame support bar (which is made of aluminium angle), the sides are not perpendicular to the base, so I shimmed the support bar to correct this. You can see the top of the square that I used to visually check this in the foreground here:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890948.jpg)

For the record, when the frame is assembled, the frame sides are pulled into the vertical by the frame cross-braces.

With the longitudinal alignment of this setup confirmed by the position of the frame support bar relative to the base, I supported the cylinder (hidden by the frame side in this photo) with my left hand, and 'trepidaciously' gave the appropriate spot on the frame side a sharp tap with a rubber mallet.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890947.jpg)

This worked well - the transfer screws marked two small points on the frame side. These were opened up with an automatic centre punch, then a traditional centre punch to create marks which I'll be able to locate in the mill using a wiggler.

The support bars and bearings were then removed from the frame sides...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890949.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890952.jpg)

... and the two sides were bolted together using the existing clearance holes...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/890951.jpg)

... which will enable me to drill the clearance holes for the fixing screws for the cylinder side braces through both frame sides at the same time.
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on March 19, 2021, 12:42:37 AM
More good progress Gary.  The flywheel came out well too.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 19, 2021, 12:59:07 AM
Thank you, MJM.

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 21, 2021, 11:51:04 PM
(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/891193.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/891192.jpg)

The crankshaft felt a little tight again though it eased off considerably after  some oil and a few turns.

The new steel flywheel was also put on as a trial fit though it's not visible in either of the two photos.

It's still the old crankshaft that can (almost!) be seen in the pictures. Probably due to my having reduced the width of the frame, there is no longer any visual sign of it running out. I reinstalled it because the replacement shaft isn't finished yet. Subject to further assessment, I may still be able to use the old one, thereby potentially freeing the incomplete new one for another project. We shall see...

Getting there! I'm starting to see the light at the end of the tunnel as opposed to the tunnel at the end of the light.

She's a bit of a beast...   8)

Main jobs remaining:

Shorten screws through cylinder side braces.
Shape frame sides and make decorative holes in them.
Cylinder drain cock.
Cylinder head gasket.
Exhaust pipes and manifold
Wooden base.[/list]
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 22, 2021, 12:14:09 AM
Title: Re: A Simple Uniflow Engine
Post by: Don1966 on March 23, 2021, 01:22:31 AM
Love the fabrication work Gary....... :Love:


 :cheers:
Don
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 23, 2021, 11:05:53 AM
Thanks Don.

 :cheers:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 24, 2021, 11:18:43 PM
The fixing screws for the cylinder cross-braces were cut to length and refitted, and the outline shape of the frame sides was roughly marked out, along with the positions for new holes for the frame cross-braces on the finished engine:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/891331.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/891332.jpg)

The flywheel is hidden at the other side of the frame in these photos. The brass disc that you can see was one of two flywheels which I originally made, but were too small. I'm thinking of cutting a groove round the perimeter of it to convert it to a pulley for a thin round section drive belt. That would give the engine two drive pulleys, the other one being the aluminium pulley beside it which is crowned for a flat belt. The different sizes of the pulleys could allow for two different speed ranges, depending on the sizes of the driven pulleys on whatever  it is that this engine will end up driving. I have some ideas about that but will keep them to myself for now...

Also, further to discussions further back in the thread about oil feed rate to the main bearings, I remembered I have these:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/891333.jpg)

I bought them from PM Research quite some time back for another project which I have not yet begun, so I'll probably use them on this engine and buy more later for the other project. They are very small but still too wide for the small space available above the bearings, but I think I have a way round that...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 26, 2021, 12:22:42 AM
I thought I'd give the engine a second test run before moving on to the final stages, given that since the first test I have properly installed the cylinder, reconfigured the frame and made a new flywheel.

The original crankshaft shows no sign of wobble (not sure what happened to that!) and the flywheel and pulleys appear to be running pretty true. A bit of lateral play can be seen in the crankshaft but that should be easy to fix. I played around with the timing a bit by winding the valve pin in and out, running the engine and measuring the protrusion of the pin. The clip below shows it performing quite well, I think, on my small compressor:

wU32XjxHvHs
Now, on to the final stages. Still quite a bit of time to go in this build, but it's definitely going in the right direction now.
Title: Re: A Simple Uniflow Engine
Post by: crueby on March 26, 2021, 01:00:55 AM
Running quite well at the slower speeds. The engine is quite a bit larger than I had thought, or that was a shop-elf-shoe in that one spot. At the higher speeds it shakes, but that is expected without balance weights on the crank.

Nice!
 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on March 26, 2021, 04:50:08 AM
Well done, Gary.  It runs quite nicely with the modifications and tuning you have done.  It will make the finishing details so much easier, now you know it runs well.

MJM460
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 26, 2021, 08:43:21 AM
Thanks guys.

@ Chris - it's a shop elf shoe - size 10, UK size (continental 44). Some elves have big feet!

It is indeed quite a large engine. Generally, I'm aiming to build as big as my machines will allow, and this is pretty much at that limit. I can only dream of a huge workshop with industrial scale machines... I'll post its dimensions and weight in this thread once it is finished. Yes, I should have expected it to shake, given the lack of counterweight on the crank. Another factor may be that currently (and temporarily) the engine is just sitting on the ends of the stainless steel screws that attach the frame sides to the base, and it was running on the smooth wooden floor of my shop. This may have made the shaking more visible as it skated back and forward with the stroke (though of course the shaking is still an issue). When it's done it will be fixed to a heavy slab of oak on rubber feet which I think will probably at least keep it in one place. If that doesn't keep it within reasonable limits, I may make another crankshaft with a counterweighted crank and swap them over... or I may just put it down to experience and put a counterweighted crank on my next engine if it needs one.

@ MJM - yes, it's motivating to see it run at this stage. Having the way ahead clear should make the remainder of the build a pleasure.

 :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 29, 2021, 11:51:56 PM
Only modest progress over the last couple of days.

Due to the trial and error that was required to get the conrod, piston and pin assembly to the optimum length for the engine to run, I had left the conrod unfinished so that if necessary it could be adjusted by screwing it in and out of the crosshead. Now that the engine is pretty much tuned, the length of the conrod has been determined. This, however, left a gap:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/891550.jpg)

I had a tiny piece of bronze bar which had previously been drilled to size. With a small amount of facing and turning, it would fit. I press-fitted it on to a piece of steel bar which acted as a mandrel, and turned and faced it to the required dimensions:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/891549.jpg)

I had previously made quite a deep undercut behind the threaded section of the bronze rod. This caused quite a bit of slop in the spacer ring once it had been passed over the threads, so I applied some Loctite 603 and made sure the spacer was centred until the adhesive set. I also used some red Loctite 542 threadlocker on the thread before reassembly:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/891552.jpg)

The slop in the spacer wasn't a major issue, but it wasn't ideal either. No big deal, but a learning point for next time: don't go mad with undercuts!

The finished connecting rod:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/891551.jpg)
Title: Re: A Simple Uniflow Engine
Post by: crueby on March 29, 2021, 11:59:20 PM
Nice solution!    :popcorn: :popcorn: :popcorn:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 30, 2021, 12:10:04 AM
 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: propforward on March 30, 2021, 01:43:09 AM
Good work Gary.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on March 30, 2021, 03:21:16 PM
Cheers Stuart!

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 05, 2021, 10:05:49 PM
And now for a shameless, off-topic diversion.

Easter holidays, and time for the annual Spring cleanup of the back yard in preparation for the warmer weather ahead (so a slight hiatus in the engine build). As long time outdoor cooking enthusiasts, this year we treated ourselves to one of these:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/891938.jpg)

It's an interesting bit of kit - it works on the rocket stove principle of extracting maximum energy from a small amount of wood in the form of long, thin sticks which are gradually fed into the two small combustion chambers. It is able to do this because of the phenomenal updraught created by the ten foot tall chimney. However, it's a bit of a hybrid because under the hob that you can see (behind the lettering) there is a shallow hollow chamber through which the flame and hot gases pass en route to the chimney, and this is where the hob - especially the two hotplates - gets its heat from. It's great for cooking with a wok, or a cast iron frying pan or a griddle, etc. The hotplates are adequate for most ordinary stove-top cooking, but for a stronger jag of heat you can take the hotplate lid off and sit your pan directly on the open flame.

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/891937.jpg)

Why am I telling you this?

Because when the hotplate lids are removed, these burners deliver a serious amount of heat out of a very small amount of fuel. And because the hole that you can see in the photo above is 7 inches in diameter. And because I have a piece of 8 inch diameter steel pipe (with a nice thick wall) which I bought a while back specifically to build a boiler with 'one day'. So I'm thinking that this may be an eco-friendly and cheap way to run an eight inch boiler capable of powering the uniflow and other larger engines. I'm thinking rolled-in copper tubes here...

More of this further down the line. But before that, I have another boiler solution in the pipeline. More of that further down the line too...

:)
Title: Re: A Simple Uniflow Engine
Post by: propforward on April 05, 2021, 10:36:21 PM
Two things Gary.

First - as I was reading your description I was thinking "this must surely be the basis of some new boiler". :D

Second - I like engines, but I also like eating. Inquiring minds want to know - what is the first gourmet treat off this apparatus?

Probably wouldn't take too long to get a tin of Beanz up to temp.
Title: Re: A Simple Uniflow Engine
Post by: crueby on April 05, 2021, 11:00:57 PM
Should be great for a boiler, but imagine the size of the Sterling engine that thing would power! Quite an interesting little stove, a long way ahead of the giant cast iron beasts of olde.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 05, 2021, 11:30:40 PM
@ Stuart: it was stir-fried noodles with onions, mushrooms, peppers and prawns with soya sauce... and local pork sausages.  :-)

@ Chris - yes. I've never seen one quite like it, but as soon as I saw them online it was a short step to 'I have to have one of these...'.

If it will run a boiler too, then even better, and I see no reason why it shouldn't. In due course, when I finally get round to building one...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 10, 2021, 11:58:42 PM
Two spacers were turned from cast iron. These go on the crankshaft immediately outboard of the bearing on each side of the engine. The purpose of these is to keep the flywheel on one side and the pulley on the other from fouling the heads of the screws which hold the bearings together, while at the same time reducing lateral play in the crankshaft:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892219.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892218.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892217.jpg)

Next, a small bronze collar was made to prevent lateral play in the crosshead pin (the pin having been made from a stainless steel cap head bolt). I had made a collar previously, but somehow managed to lose it. However, it wasn't a big job to make another one:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892221.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892220.jpg)

Next, I cut a groove in one of the brass pulleys. These were originally intended to be twin flywheels but they turned out to be too small and light:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892223.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892222.jpg)

This will be a light duty pulley which will run a small round-section belt, potentially to turn a small driven pulley very quickly. The aluminium pulley beside it will run a small flat belt which I have already purchased from PM research.

Next, the developing engine was dismantled (again...) ...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892225.jpg)

... and the two frame sides were bolted together for shaping by chain drilling and sanding of the edges, and so that most of the remaining 'functional' (as opposed to decorative) holes can be drilled in them:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892224.jpg)

But not this day...

Title: Re: A Simple Uniflow Engine
Post by: crueby on April 11, 2021, 12:28:03 AM


.... I had made a collar previously, but somehow managed to lose it.




Uh oh... Sure sign of a shop gnome infestation, stealing nice shiny parts for thier hoard.  Better put out some cookies as bribes and see if you can covert them to helpful shop elves. Or bait a mousetrap with chrome bearings!
 :Lol:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 11, 2021, 12:32:34 AM
Yeah, I was thinking that may be the problem.

Mousetrap with chrome bearings... I like that.

Would you recommend the trap be humane or 'traditional'...?
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 11, 2021, 10:40:38 PM
More irrelevance to start with but I couldn't resist it. Last year I found an old sack barrow in a skip. I dragged it home on the off-chance that the tyres may not be punctured and that it may be worth rehabilitating, and shoved it behind the shed where it made me feel guilty for months. Finally, last week, I got round to lugging it out and checking it over. Punctured tyres, rusty frame, not worth keeping. So off to the tip it went, apart from the wheels:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892273.jpg)

These are of pressed steel, in two halves bolted together, and when separated the tyres came off easily. Cleaned up, re-bushed and repainted, I reckon they will form the basis of a couple of nice little flat belt pulleys for some countershaft or other connected to my lineshaft project in France one day in about 1000 years time...

Meanwhile, back to the engine. After drilling the remaining holes for the frame cross-braces, I started chain-drilling a rough outline of the shape of the finished frame in the two frame sides (which were bolted together):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892272.jpg)

I know it's common practice to overlap the holes but I find that it's easier to keep control if they are slightly separate, even if it means more sawing and profiling later.

That done, the temporary assembly was held in the vice...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892271.jpg)

... and sawn...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892276.jpg)

... resulting in this:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892275.jpg)

Hedgehog engine? Steam-driven chainsaw...?

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892274.jpg)

Next up, the brutal job of smoothing out all these edges...
Title: Re: A Simple Uniflow Engine
Post by: propforward on April 11, 2021, 11:57:32 PM
Hmmmm. The drilled edging is an interesting look. If it wasnít so hazardous to arteries Iíd suggest leaving it for that ďsteampunkĒ look. But probably best to smooth it out and protect fingers.

Thatís a lot of drilling Gary, way to stay the course! Those plates will look great after clean up.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 12, 2021, 12:24:12 AM
Ah yes Stuart - it did occur to me this afternoon that I could make a deliberately spiky engine.  8)

The chain drilling is the easy bit, though. If I recall from the small oscillator that I made, smoothing out these edges is the worst bit - would take forever with a file; quicker with a belt sander but hot, messy work. Needs must though.

And then there will be 'decorative' holes to drill in the frame sides too...
Title: Re: A Simple Uniflow Engine
Post by: propforward on April 12, 2021, 12:30:53 AM
Time for a CNC? :D

The shape of the plates reminds me of a motorcycle fuel tank.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 12, 2021, 12:39:02 AM
Time for a CNC, yes, but no room for one! Not even room for a bandsaw. Not here, anyway.

I have a bit more room in my workshop in France, and have actually started restoring a mill over there which my eventual aim is to convert to CNC. I got as far as buying a new treadmill motor and variable speed controller for it, both of which got soaked when the roof blew off. Haven't yet been able to go over and assess the damage...  ::)

Yeah, I suppose it does look a bit like that now that you mention it. May look a bit less so when I have drilled lots of holes in it though...!
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on April 12, 2021, 01:10:04 AM
Hi Gary, still watching along.  Great progress.

Perhaps a bit of rotary table work for those smaller radii would reduce the filing required?  It will also work for some of the internal cutouts.

MJM460



Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 12, 2021, 10:09:45 AM
Hi MJM -

Thanks for this.

I guess that would be a good way to do it, but methinks I'll just freestyle it with either the small or (more likely) the large belt sander....
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 12, 2021, 11:39:40 PM
If it wasnít so hazardous to arteries Iíd suggest leaving it for that ďsteampunkĒ look.

Actually, Stuart, at this point it has now developed a look that's more dieselpunk than steampunk.  8)

I began on smoothing out the edges of the the two sides bolted together. This amounted to a 12mm thickness of aluminium plate, and I'm saddened to report that this here small belt sander gave up the ghost under the stress of it:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892317.jpg)

It may just be a fuse, but if it's the motor then so be it. It may make quite a nice little machine to power with a 35mm bore uniflow engine...

So then I tried the belt sanding attachment on my Coronet Major 'wood lathe and multi-function wood machining centre'. I love this vintage British machine and it has an exceptionally powerful motor. Perhaps I went at it a bit too enthusiastically because the still-jagged chain-drilled edges of the plate shredded the belt, which can be seen here lying under the machine:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892318.jpg)

Good job I have other belts for it.

Surprisingly, the best solution was a small drum sanding attachment held in the drill press:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892319.jpg)

I went through a few belts but it didn't take long (less than two hours) to get the sides pretty close to finished shape:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892320.jpg)

I'm really quite pleased with this. The edges may need a tiny bit more finessing but it's not too bad at all. It has a shape that evokes to me a butterfly's wing. This wasn't intentional - it just emerged from the process.

In order to take stock and make decisions about the placement of decorative holes in the frame, I reassembled the engine:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892323.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892324.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892322.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892321.jpg)

Before dismantling it yet again to drill the holes, I will also mark out the ends of the angled frame support bars so that they can be cut to follow the curve of the frame sides at the bottom.
Title: Re: A Simple Uniflow Engine
Post by: crueby on April 12, 2021, 11:45:38 PM
Love the shape - you have a great eye for swoopi-ness!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 13, 2021, 12:05:27 AM
Thanks Chris.

There are a couple of areas along that top curve that don't flow quite as I'd like them to, but they're pretty minor. The trouble is it can be a game without end trying to smooth these kind of bits out, so I may or may not go back to them.

It's amazing how sensitive the human eye is to even tiny glitches in a curve. Overall I'm happy though.

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: propforward on April 13, 2021, 01:04:39 AM
Looks pretty excellent to me Gary!
Title: Re: A Simple Uniflow Engine
Post by: Kim on April 13, 2021, 02:25:48 AM
Love the curvy frame, Gary!

Sorry about the belt sander and the chewed-up belt, etc... Glad you finally got there!

Kim
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 13, 2021, 09:52:50 AM
Many thanks guys.

@ Stewart - it's not too bad. Being picky with myself I can see a slightly clunky bit of the top curve at about two o'clock from the bearing hole. It's minor, but if it keeps bothering me I'll try to take it out later.

@ Kim - yes, some things turn out to be sacrificial. I did go in a bit recklessly, to be fair. I seem to remember that the drum sanders worked well on my oscillator too, so I should probably have re-read that thread before I started with this. But I do quite like the idea of driving the small sander with this engine if it can't be fixed...
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 17, 2021, 11:17:38 PM
I have two little drip-feed oilers that I bought from PM Research quite some time ago for another (as yet unstarted) project, so I thought I'd use them for the bearings of this engine. They have a 1/4 - 40 UST thread, which the PM Research website says is compatible with the UK 1/4 - 40 ME thread. I have a tap and tapping drill for the ME thread so I thought I'd test it on a piece of brass bar:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892579.jpg)

It fits fine. I also checked the oiler for oil feed rate:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892586.jpg)

It appears to give a good range according to adjustment.

Next up, the cylinder drain cock (only one as the engine is single-acting). The best place appeared to be in the cylinder end cap, as low down in the bore as I could reasonably get it. There wasn't much room for manoeuvre, but I'm happy with the position. The location was marked out using the digital height gauge, centre punched...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892581.jpg)

... centre drilled, drilled and tapped. The tapping operation was done using tapping mode on the mill, which is good for tapping open-ended holes once you get used to it. The drain cock was then given a trial fit:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892583.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892584.jpg)

Then - changing tack - the engine was taken apart yet again and the process of making the cutouts in the frame sides was begun, using hole saws. As luck would have it, the four hole saws that I keep in my shop were exactly the right sizes for the four main holes that I wanted to cut! So here goes...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892582.jpg)

More holes coming up...

Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 18, 2021, 09:29:51 PM
More holes:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892631.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/892630.jpg)

Just a lashup for the sake of the look. The next step is to shape the frame mounting bars to follow the curves of the side plates.
Title: Re: A Simple Uniflow Engine
Post by: crueby on April 18, 2021, 09:54:51 PM
Those curves are crying out for some pinstripes. Maybe some hotrod flames... Nice!!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on April 18, 2021, 11:29:27 PM
 :o :) :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 11, 2021, 11:00:47 PM
It has been a busy time recently - electric bikes, sheds, the back yard. And work.

So, not very much shop time at all, and only a small amount of progress and still quite a way to go, though I can just see the light glimmering at the end of the tunnel with this engine.

Shaping the ends of the frame support bars with a hacksaw, files and a drum sander so that they follow the line of the bottom corners of the frame sides:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/893893.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/893892.jpg)

This is quite a tedious job that takes a fair bit of time. Two down, two to go...
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on May 12, 2021, 11:44:07 AM
Hi Gary, good to see some progress.  I think we all have those other jobs which inevitably get in the way.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: propforward on May 12, 2021, 02:14:22 PM
Painstaking work for sure, but really good to see it moving along - it's a fascinating engine.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 13, 2021, 10:15:19 AM
Many thanks, guys.
 :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 17, 2021, 10:36:36 PM
Slow progress...

Not getting as much shop time as I'd like, so still working away at tidying up the bottom corners of the frame.

I took the cross-braces out and bolted the frame sides and support bars together so that I could work on them all as one so that they will match each other.

Filing, drawfiling, needle files, drum sanders, cheap Dremel clone, flap wheels... changing tools frequently as much to alleviate the tedium as anything else!

Heading in the right direction, but still quite a way to go:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894192.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894193.jpg)

Gonna get the hacksaw on to these square corners tomorrow to speed the process along a little.
Title: Re: A Simple Uniflow Engine
Post by: propforward on May 17, 2021, 11:10:53 PM
I admire your craftsmanship. It's very stylish - beyond my patience to be honest, but it's going to be a very unique and interesting engine for sure.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on May 17, 2021, 11:13:45 PM
Very kind of you Stuart - thank you.

It's certainly testing my patience - give me cast iron or even steel any day over aluminium to work with files!
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 03, 2021, 10:12:41 PM
Well, all that filing got me to a place I'm reasonably happy with. The bottom corners of the frame are looking ok, bar some final cleanup:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894877.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894876.jpg)

I'll also cut the base plate to length at each end for a tidier look.

The next step was the installation of drip feed oilers on the main bearings. I had two of these, bought from PM Research for another project:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894883.jpg)

Will have to order new ones for the other project but that's ok.

In order to keep the oilers parallel to each other, I decided to drill the holes for them in the bearings in situ, with the frame set up in the mill:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894879.jpg)

It's a small mill and a fairly large engine so it was a bit of a squeeze. Even with the drill bit held in the ER-32 collet chuck instead of a drill chuck I only just managed to get everything in.

I drilled with the tapping drill through the outer sleeve of each bearing (which sits on the inside of the frame) and into the inner parts of the bearings. The inner parts of the bearings were just spotted with the end of the drill. These holes were then finished with a much smaller bit. The oilers are adjustable, but if not enough oil finds its way through to the crankshaft, these smaller holes can always be opened up a bit:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894886.jpg)

The finished bearing assembly (one of two) with the oiler in situ...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894878.jpg)

... and the finished assemblies in situ on the frame:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894887.jpg)

In the interests of transparency I will confess: The two oilers are not in perfect alignment with each other. Don't know how it happened, but I have various theories, all of which boil down to carelessness or impatience (mainly the latter). The runout is not horrendous, but it's definitely noticeable. My sense is that when the crankshaft, big end, flywheel and pulleys are all installed, no-one will ever notice. No-one except me, that is. You know how it goes...

After that, it was back to cylinder duty. I opened up the two exhaust ports to partial depth and tapped them:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894885.jpg)

The inner parts of these ports remains narrow as before, but they can always be widened later if needs be.

Elbows were then installed so that piping can be added later when the engine is set up with a boiler:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894882.jpg)

The elbows came with black paint on the cast part but I removed this with acetone.

Next, a gasket was made from some orange coloured gasket paper. Amidst the clutter of this picture you can see the various items that were used in the process:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894881.jpg)

The gasket, partially done...

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894884.jpg)

... and the cylinder complete with gasket and exhaust connectors:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894888.jpg)

Not long to go now...



Title: Re: A Simple Uniflow Engine
Post by: crueby on June 03, 2021, 10:59:08 PM
        :popcornsmall:   
 :popcorn: :popcorn: :popcorn:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 06, 2021, 11:29:24 PM
Today, the ends of the base plate were cut with a hacksaw and milled square and to length:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894996.jpg)

This completes the four bottom corners of the frame, bar some final cleanup. I'm quite pleased with the result:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894995.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894994.jpg)

I then gave the parts a rough cleanup with acetone to remove most of the layout dye, then reassembled the engine. There are only a few jobs left to do, and the photos below give a good idea of what the finished engine will look like:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894997.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/894998.jpg)

I confess I am happy with the look...
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on June 07, 2021, 01:21:34 PM
Hi. Gary, looking great.  A very interesting design of the frame to match the interesting operating principle of the engine.

Looks like it could be the basis for a modular design which could accomodate different cylinders.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: propforward on June 07, 2021, 05:11:57 PM
Love it Gary, great looking engine - I always like following your progress.

I've been wondering where my marking blue went...................................
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 07, 2021, 09:27:37 PM
Thank you both, gentlemen.  :ThumbsUp: :ThumbsUp:

@ MJM - yes, I guess a cylinder with a slide valve or a piston valve could be slotted in there as an alternative with not too much overall modification.

@ Stuart - I'm sorry, ok? I have a thing for marking blue and I just couldn't resist raiding your stash. I'll pay you back as soon as I can... I'm expecting a cheque next week... honest!
You may have noticed I'm crazy for the red version too (less covering power, but man! The colour...).

Listen - if you ever get a chance to score some other colour - green, for example, I'll definitely be interested.
Title: Re: A Simple Uniflow Engine
Post by: propforward on June 07, 2021, 10:48:33 PM
 :ROFL:
Title: Re: A Simple Uniflow Engine
Post by: Admiral_dk on June 07, 2021, 10:52:36 PM
Quote
I confess I am happy with the look...

Well that is the most important critic you're satisfying  ;)

Congratulations are in order  :cheers:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 07, 2021, 11:08:41 PM
Per - you have a point!

 :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 16, 2021, 10:31:20 PM
It seemed to me that the big end needed an oil hole for lubrication of the bearing. I hadn't sufficiently taken this into account at the design stage so I was left with very few options for an oil hole that wouldn't foul either the threaded holes for the screws that hold the bearing cap in place or the probably over-deep hole into which the connecting rod is threaded:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895310.jpg)

My solution was to drill the oil hole at an angle from a point very close to the bearing cap screw hole through into the bearing. Here I am just about to make a start with a centre drill before swapping to a twist drill:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895312.jpg)

After centre drilling I started with a reasonably wide drill to create a small oil reservoir at the top end of the hole, then I changed to a much smaller drill and drilled though to the bearing surface. In practical terms this appears to have worked ok, but I am not happy with the way that the oil hole clashes with the cap screw hole:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895309.jpg)

It's not a great look but as I say I was limited for choice. The oil hole emerges quite pleasingly on the inside of the bearing, though:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895313.jpg)

Initial testing would suggest that the flow of oil into the bearing is not too fast. If in practice it turns out to be too slow, the hole can easily be opened up a little.

Note the weeds growing back between the slabs of my back yard after a recent weeding. Building engines is a more attractive pastime to me than weeding is.

That done, it was time to mill flats on the crankshaft to seat the flat-nosed grub screws which secure the flywheel and pulleys. I had already done similar before I changed the overall layout of the engine so there are now some redundant flats on the shaft as well as those which are in use. I don't think that's an issue, though. Marking out the positions of the flats with the shaft in situ:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895305.jpg)

Milling the flats (I find 0.5mm depth to be about right on this 12mm shaft):

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895306.jpg)

These jobs done, I completely dismantled the whole engine:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895311.jpg)

On reassembly, each part was cleaned as I added it. For the aluminium, I was not seeking a mirror finish, but more of a satin look, so I used steel wool then wiped with French 'alcool ŗ bruler' (basically methylated spirits). There are still some marks on the larger areas - a scratch here and there, even a couple of scribe lines. These do not bother me:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895308.jpg)

I also deburred the decorative holes in the frame where required.

The cast iron parts and the steel flywheel were also given the steel wool treatment, but the bronze collars and bearings and the brass pulley were spruced up with 'Autosol' metal polish:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895307.jpg)

Screws and other small parts were given a soak in the alcool ŗ bruler and brushed clean.

The newly cleaned-up engine was reassembled yet again, and this build is nearing its end. I shall post a couple of pictures of it sometime over the next day or two, along with some details of overall weight and dimensions.

All that remains now is to finish the oak base and mount the engine on it.

Title: Re: A Simple Uniflow Engine
Post by: crueby on June 16, 2021, 10:59:40 PM
Great journey so far, getting close!!   :popcorn: :popcorn: :popcorn:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 16, 2021, 11:01:03 PM
Yes!

Cheers, Chris!

 :cheers:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 20, 2021, 10:53:31 PM
The engine itself is finished:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895493.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895492.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895495.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895494.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895497.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895496.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895499.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895498.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895501.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895500.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895504.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895503.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895502.jpg)


Vital statistics (as seen here) -

Overall length:     450 mm / 17 5/8 inches

Frame width:     145 mm / 5 ĺ inches

Overall width (including crankshaft):     300 mm / 11 ĺ inches

Height:     203 mm / 8 inches

Bore:     35.7 mm / 1 7/16 inches

Stroke:     40 mm / 1 5/8 inches

Flywheel diameter:     157 mm / 6 3/16 inches

Large pulley (round belt) diameter:     112 mm / 4 7/16 inches

Small pulley (flat belt) diameter:     51 mm / 2 inches

Weight:     12.9 kg / 28.4 lbs


Materials -

Frame (including base):     aluminium

Cylinder:     cast iron

Piston:     cast iron

Crosshead:     cast iron

Connecting rod:     bronze

Big end:     cast iron

Crankshaft:     steel

Main bearings:     bronze

Flywheel:     steel

Large pulley:     brass

Small pulley:     aluminium

Bushes and collars: bronze and cast iron

Fixings:     stainless steel

All that remains is to finish the base, which is made of oak.

I got rid of my big old cheap table saw a couple of years ago as it was taking up too much room. Nowadays I set up an improvised arrangement featuring my Evolution Rage circular saw clamped upside down in a workmate with a joinery clamp holding the trigger in the Ďoní position. I am not advocating this practice, just describing what I do!

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895506.jpg)

The base was cut to its basic shape and worked with rasps, a planer, a scraper and sandpaper:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/895505.jpg)

Thereís still quite a bit of work in this as itís still quite rough. Definitely worth putting some time into though I reckon...
Title: Re: A Simple Uniflow Engine
Post by: propforward on June 20, 2021, 11:33:04 PM
Absolutely superb Gary! Really unique engine - great to see the finished article. Looking forward to seeing the engine on its base.
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on June 20, 2021, 11:45:24 PM
Thank you Stuart! Very kind of you, as always.

 :cheers:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 13, 2021, 11:49:13 PM
 The aluminium base plate of the engine was used to transfer hole positions on to the top of the wooden base:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/896546.jpg)

These were brought to size using various bits in the drill press:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/896539.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/896537.jpg)

Four holes were then drilled in the underside to take threaded inserts for the feet:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/896538.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/896545.jpg)

The gaps in the oak base where the two pieces of wood joined were then filled, and a fair amount of sanding was done. The wood was then treated with Danish Oil (natural, not coloured) - a total of six coats to protect it from oil, steam and water. The way that the first application of Danish Oil dramatically transforms the look of the wood is always a favourite moment of mine:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/896536.jpg)

The engine was then fixed to the wooden base with wood screws which passed through clearance holes in the frame side support bars and the base plate. Before doing so, I used a generous amount of silicone sealant round all the edges and screw holes to prevent water from seeping in between the engine and the wooden base.

Et voila! This engine is done:

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/896541.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/896540.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/896543.jpg)

(https://www.model-engineer.co.uk/sites/7/images/member_albums/173350/896542.jpg)

And finally, a short video. I deliberately made the base quite massive thinking that this - in combination with the orange rubber feet - would keep it stable when running. Not a bit of it, as you will see from the video. This thing is a bucking bronco, mainly due to that long cast iron piston. When it's in use, the feet will be removed and the engine will be bolted to my bench to hold it steady. The feet can go back on when it's on display.

https://www.youtube.com/watch?v=071Zh0OVfcU

I'll come back to this thread in the fullness of time when this engine is running on steam...  ;)

Many thanks to you all for the help, advice and encouragement that so many of you have given me along the way with this build.

And now on to the next one...

gary

Title: Re: A Simple Uniflow Engine
Post by: RReid on July 14, 2021, 12:46:59 AM
That looks really great, Gary! A fine runner, and it sounds good too! Congratulations!  :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: crueby on July 14, 2021, 12:59:20 AM
Wonderful!  Sounds great, looks great, runs well. Part of the movement was likely the uneven surface. Just wedge a shop gnome under that high corner...


 :cheers:
Title: Re: A Simple Uniflow Engine
Post by: propforward on July 14, 2021, 01:03:58 AM
Brilliant result Gary!

 :ThumbsUp: :ThumbsUp: :ThumbsUp: :ThumbsUp:
Title: Re: A Simple Uniflow Engine
Post by: MJM460 on July 14, 2021, 10:13:48 AM
Excellent result Gary.  Great to see it come to life.

Those flywheels donít look bad at all.  When we were talking about flywheels, I thought you were thinking of something much bigger.  Interesting strobe effects with the fixing screws and the camera.

Now to think of the next one.

MJM460

Title: Re: A Simple Uniflow Engine
Post by: Jasonb on July 14, 2021, 10:56:28 AM
Good to see it finished and running.

Adjusting the feet so all 4 are in contact with what's under it will help with the moving about but it it is still a bit lively you could think about balance weights on the crank or taking some metal out of one side of the flywheel rim.
Title: Re: A Simple Uniflow Engine
Post by: Zephyrin on July 14, 2021, 11:35:28 AM
nice to see your engine running that well... congratulations !
adding a counterweight on the flywheel would help with the jumping, something around the weight of the piston plus the conrod.
Title: Re: A Simple Uniflow Engine
Post by: ShopShoe on July 14, 2021, 12:47:05 PM
Congratulations.

A somewhat different design, but I like it.

It does sound nice.

I'll be watching for what's next.

Thank You for posting

ShopShoe
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 14, 2021, 11:13:32 PM
Many thanks all: Ron, Chris, Stuart, MJM, Jason, Zephyrin and Shopshoe.

@ Chris - good suggestion. However,  it appears that my shop gnomes read your post before I did, because when I went out to my shop this morning they had already called out NUGGETS (the National Union of Gnomes, Goblins, Elves, Trolls and Sprites). The rep met me at my shop door, his arms folded in determination, and the upshot of the ensuing discussions was that I agreed not to use any of the workers as living shims or packing, on the basis that the gnomes would ensure that the engine's feet are properly adjusted and locked at all times. It was also agreed that should this measure prove to be ineffective, a delegation of the workforce will remove the feet and bolt the engine on to my bench for further stability testing.

My view is that this was a satisfactory outcome. The question of balancing of the flywheel (as suggested by Jason and Zephyrin) was not discussed at the meeting but this can always be revisited at a future date should it prove to be necessary.
Title: Re: A Simple Uniflow Engine
Post by: Dave Otto on July 15, 2021, 01:16:32 AM
That's a really interesting design Gary, for the longest time I really had no idea where you were headed with this, and now I see that you had a plan the whole time. :)
Great project and great outcome, nicely done!

Dave
Title: Re: A Simple Uniflow Engine
Post by: crueby on July 15, 2021, 02:31:56 AM
Many thanks all: Ron, Chris, Stuart, MJM, Jason, Zephyrin and Shopshoe.

@ Chris - good suggestion. However,  it appears that my shop gnomes read your post before I did, because when I went out to my shop this morning they had already called out NUGGETS (the National Union of Gnomes, Goblins, Elves, Trolls and Sprites). The rep met me at my shop door, his arms folded in determination, and the upshot of the ensuing discussions was that I agreed not to use any of the workers as living shims or packing, on the basis that the gnomes would ensure that the engine's feet are properly adjusted and locked at all times. It was also agreed that should this measure prove to be ineffective, a delegation of the workforce will remove the feet and bolt the engine on to my bench for further stability testing.

My view is that this was a satisfactory outcome. The question of balancing of the flywheel (as suggested by Jason and Zephyrin) was not discussed at the meeting but this can always be revisited at a future date should it prove to be necessary.
:lolb: :lolb: :lolb: :lolb:
Title: Re: A Simple Uniflow Engine
Post by: gary.a.ayres on July 15, 2021, 02:06:15 PM
That's a really interesting design Gary, for the longest time I really had no idea where you were headed with this, and now I see that you had a plan the whole time. :)
Great project and great outcome, nicely done!

Dave

Thanks Dave - very kind of you.

I had a pretty clear view from the start as to where I wanted to go with it, though I may not have explained it very clearly. The one main mid-build change was that I had originally intended it to be symmetrical, with two pulleys inboard of the frame sides and twin brass flywheels. However, the two brass flywheels combined weren't heavy enough so I made one of them into a pulley and made a new and much bigger flywheel out of some steel that I had. The whole frame became narrower (and better-looking) because of that, which was a bonus. It also leaves me with two spare pulleys for a future project, which is nice. Other than that fairly major change it's as per my initial idea.

Cheers,

gary