Author Topic: A Simple Uniflow Engine  (Read 9816 times)

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #15 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.


Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #16 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!

Online MJM460

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Re: A Simple Uniflow Engine
« Reply #17 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
The more I learn, the more I find that I still have to learn!

Offline Jasonb

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Re: A Simple Uniflow Engine
« Reply #18 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.

Offline crueby

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Re: A Simple Uniflow Engine
« Reply #19 on: May 06, 2020, 04:32:28 PM »
Is there a good reference chart for all the initials in inserts?

Offline Jasonb

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Re: A Simple Uniflow Engine
« Reply #20 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

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #21 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:

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #22 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.

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #23 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 :



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 ...



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



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.



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...

Offline Johnmcc69

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Re: A Simple Uniflow Engine
« Reply #24 on: May 11, 2020, 11:32:49 PM »
 :ThumbsUp:
 Great work Gary! Nice finish on the flywheel!

 John

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #25 on: May 11, 2020, 11:44:37 PM »
Thanks John - very kind of you.

gary

Offline Jasonb

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Re: A Simple Uniflow Engine
« Reply #26 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.

« Last Edit: May 12, 2020, 07:22:39 AM by Jasonb »

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #27 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.

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #28 on: May 12, 2020, 10:52:37 PM »
The order of materials arrived today. Treasure!



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.

Offline gary.a.ayres

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Re: A Simple Uniflow Engine
« Reply #29 on: May 15, 2020, 12:05:57 AM »
More stock arrived today:



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...



... 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:



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:



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)