Author Topic: Making a small marine steam engine the beginners way.  (Read 12487 times)

Offline Gas_mantle

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Re: Making a small marine steam engine the beginners way.
« Reply #15 on: February 20, 2016, 02:49:10 PM »
Having now just about completed another little engine I've been working on I've now been able to get at bit more to this project. I had originally thought about doing the cylinder end cover next but instead made the pistons and just about completed one of the valve chests.

I needed to plug 2 holes leading from the valve cylinder to the long transfer passages and settled on making 3mm aluminium plugs to be hammered in and sealed with a drop of Loctite 638, once filed down flush they seem to offer a good seal that is hardly noticeable - they can just about be seen on the left hand one.

]



I decided to open out the existing 3mm transfer passage to 4mm and also drill a shallow 5mm diameter cavity at either end - this will allow me to add a sealant where the passage bridges the gap into the cylinder flange. I also reamed out the 8mm valve cylinder at the same time.



My original intention for securing the valve chest to the cylinder was to use 8 M2.5 bolts but I find them a bit unreliable when tapping small holes into aluminium where the threaded hole isn't going to be very deep - I've decided I can just about get away with M3 but will use studs as I think there will be less chance of damaging the threads in the cylinder wall. Now that the air passages are located inside the valve chest a really close airtight fit isn't essential but M3s should give me a suitably secure fit.



So far so good, just need now to drill the cylinder, secure the chest then drill the flanges and seal so ought to
have one cylinder / valve assembly completed tomorrow.

And there we have it  - looking rather like a small aluminium toilet bowl  :)



Peter.

Online Kim

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Re: Making a small marine steam engine the beginners way.
« Reply #16 on: February 20, 2016, 03:58:08 PM »
Nice work on the plugs Peter, hardly noticeable at all!
Your tiny toilet bowl looks great to me! :)
Kim

Offline Gas_mantle

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Re: Making a small marine steam engine the beginners way.
« Reply #17 on: February 21, 2016, 08:11:33 PM »
Hi,

I've managed to get a little bit further and so far so good.

It was my intention to drill and tap the cylinders the secure the chest with bolts but after a rethink I decided to cut the heads off some bolts to make studs and Loctite them into the cylinder. I want the cylinder / valve to be a permanently attached fully airtight 1 piece unit once completed.

I did drill for 8 studs but even with 4 and Loctite it is incredibly strong fit so I'll stay with 4 and use dummy studs in the other 4.



Now with the valve chest fixed in place the next job was to make an airtight seal at the join between the chest and cylinder flange, I've never used JB Weld before but after reading good reviews I gave it a try. Having plugged both ends with the epoxy mix once hardened it was a simple matter to reopen the steam passage and cut a small groove leading to the cylinder bore. The JB weld was more runny than I expected and I did worry that it would flow all the way down the passage and block the small hole into the valve bore. Fortunately this didn't happened and after a few tests flushing air / water through it I'm satisfied there is an unobstructed flow through out.

I cut the passage to the cylinder using my trusty old 10 Woolworths dremmel type tool so it's not particulary attractive but should be functional and hopefuuly means I've now got my one piece leakproof valve / cylinder assemply.



Next task was the simple enough cylinder covers, I want to dispense with crosshead guides so have opted to have the piston rods passing right through the cylinders - It's not intended to be any kind of replica engine so I'm not concerned if it gives a slightly unusual appearance - the moving piston rods may even add a bit of visually interest when the engine is running.

I wasn't really sure of the best order to machine the covers but wanted the piston hole drilled from the same lathe setting as the cylinder locating spigot so settled on doing the outside face first.

The next image will become the top of the cylinder head but because I want the piston rod hole drilled from the other side Ive only gone in about half the required depth to take an M8 thread for the piston rod guide.



Having now parted off and turned the part round I can turn the spigot side. At this point I drilled through and reamed to 4mm for the piston rod and hopefully if I set it up right it will meet the hole on the other side centrally. I'd be interested how other more experienced members would have made this part as I'm sure there must be an easier way to do it.



As it happened it turned out quite well, the central hole lines up nicely and at least now the locating spigot should ensure it runs true to the cylinder centre line.

Overall I'm reasonably happy with it, the flanges and cylinder covers are maybe a bit on the thick side but I'll have to get used to it. What was looking like an aluminium toilet is now resembling a fire hydrant !



With a bit of luck I might be able to try it connected to an airsupply tomorrow and see if the piston will respond to the valve in one direction at least.

Peter.





Offline Gas_mantle

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Re: Making a small marine steam engine the beginners way.
« Reply #18 on: February 23, 2016, 10:24:52 PM »
Hi,

Having now made both cylinder covers and the 'dogbone' spool valve for one of the cylinders the next job was to fit the covers and give the assembly a crude test on my airbrush compressor. I would have made sense to make 4 covers etc at the same time but I wanted to see how the cylinder performed before going further.

Without a rotary table or dividing head I used a crude method with a spirit level and surface gauge on the jaws of my 3 jaw chuck to get the 60* spacing for 6 retaining holes - Ive settled on M2.5 with enough room to go to M3 if need be later.



I made 2 brass piston rod guides that will retain PTFE tape to give an airtight seal and added paper gaskets.



With a few temporary bolts holding everything together I've been able to test it and pleased to say it works well without leaks and responds to the valve very well  :)



Satisfied it will work ok I can now concentrate on completing the second cylinder assembly.

Peter.




Offline Gas_mantle

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Re: Making a small marine steam engine the beginners way.
« Reply #19 on: March 01, 2016, 12:56:52 PM »
Hi all,

I've now managed to almost complete the 2nd cylinder and valve assembly and all the need now is the plumbing fixtures and a bit of final tidying up. It seemed logical to next make the supporting plate for them to attach to.

I've only ever used my faceplate once before to practice on a bit of scrap so this was actually the first proper use of it and found it awkward although things did ultimately turn out well. I settled on using a piece of 6mm thick steel 140mm long it only just cleared the lathe bed when the offset was positioned - a bit of steel bar worked well as a wobbler bar for centering but getting the dial indicator positioned to miss the mounting hardware proved awkward.



Once bored out and mounting holes drilled everything seems to be looking ok.



So far I'm quite pleased with the result, they both work well on an airline so hopefully these 2 bad boys will have a bit of guts when running  :)



I'll possibly make a start on the crank shaft tomorrow.

Peter.

Offline Gas_mantle

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Re: Making a small marine steam engine the beginners way.
« Reply #20 on: March 05, 2016, 07:43:19 PM »
Hi,

With the cylinder / valve assemblies now almost complete I decided to make 2 simple brass valve guides and set about making the crankshaft. I don't have the experience to make the shaft from a solid piece so I've opted to make one from 10mm silver steel and EN1a steel webs.

With 50mm dia webs and a 20mm throw I had to make do with 6 mm cranks pins although 8mm might have been better, I had originally turned to size 2 of the discs then decided for the remaining 2 I'd mount them all on the shaft and turn them together, my thinking was to ensure they are all exactly the same and enable accurate drilling later.




Although it eventually worked well I did seem to make more work for myself



With them all exactly the same and bolted together I was able to drill all the crank pin holes together.



All I need to do now is mark out and cut the webs to create a weighted side and secure them nearer to completion. I'm not sure wether the proportions of this project are working out right but it's starting to take shape and too late to alter things.

Finally a shot showing the work so far with the valve rod guides in place  :)

]

Peter.


« Last Edit: March 05, 2016, 08:02:46 PM by Gas_mantle »

Offline burnit0017

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Re: Making a small marine steam engine the beginners way.
« Reply #21 on: March 05, 2016, 08:00:13 PM »
Hi, thanks for posting. I am learning a lot. Thanks again.

Offline Gas_mantle

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Re: Making a small marine steam engine the beginners way.
« Reply #22 on: March 08, 2016, 09:11:10 PM »
Hi all,

I decided to leave the cutting of the crank webs for now till I have a think about the proportions and how to mark them out so instead I set to work making the crossheads and big end bearings.

For the crossheads I used 15mm square steel bar and began with cutting a small raised top and small chamfers then drilling and tapping a 4mm thread.



I didn't make a very good job of chain drilling the slot and left myself with a lot more filing than I should have.



With 15mm dia filing buttons made I set about radiusing the ends and opening out the central slots, fortunately things turned out reasonably well.





Next, on to the big end bearings.

Since it is a closed crankshaft I need split bearings and wasn't really sure of the best way of going about it but started with 5/16 x 1" steel for the top.



When it came to turn it around to face the other end parallel I didn't leave much to hold onto.



2 pieces of  5/16 square brass will form the bearing halves and another piece of steel for the foot so onto the drilling.



While checking the alignment with silver steel rods I decided I'd thread them as the final fixings rather than M3 bolts that I had originally intended.



The intention next is to turn the 4 bolted together parts in the lathe as 1 item to achieve even radiused sides but I forgot to mark the centre line of the steel foot and the sides are uneven hacksaw cut edges. The only way I could see to find the centre line with some degree of accuracy was by supporting the whole assembly on a close fitting rod then mark as best I can where I estimate the centre to be with a scribing block.



Again using the scribing block and the estimated centreline I'm hoping it's positioned right to turn the sides and part off from the waste material in the chuck.



With the centre hole drilled and reamed I got there in the end :-)

Just needs a bit of fine filing to ensure the side faces are perfectly even when positioned it the crank web and all seems ok.



I'm sure there must have been an easier and more accurate way of doing it - now just got to complete the second one tomorrow.

Peter.









Offline Gas_mantle

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Re: Making a small marine steam engine the beginners way.
« Reply #23 on: March 16, 2016, 12:24:17 PM »
Hi,

Over the last few days I made a start on the crank webs and crankshaft bearings, what started out ok is now turning out not so good  :(

For the crank webs I wanted a weighted design, I guess on a small engine like this it probably won't make a lot of difference to it's running and I can only make a guess as to what shape they need to be but I thought they'd make the engine look a bit more attractive.

I started off by roughly marking out the profile and drilling holes for the radiused corners, getting the proportions to look acceptable took a few goes and I wanted to make sure the crank pin side was at least as wide as the big end bearing, so after a lot of guess work I decided this was about as good as I was likely to get



So I drilled the remaining discs and filed them as a single unit bolted together.





After a lot more filing I arrive at this quartet, they still need a bit of slightly evening up and the finishing improving but I'm reasonably happy with the result and if they do actually assist in the balancing of the engine it's a bonus.



With webs about done I'm now in a position to determine roughly how high the crankshaft needs to be and set about making the 4 supporting bearings and it all goes downhill from here  >:(

I really had no idea how best to go about making them but as it is a closed crankshaft I wanted split bearings and was mindful of getting them all exactly the same height. Settling on 5/16 steel for the bases I roughly turned part of the sides parallel and made a centre mark as a future reference should I need it later.



Doing all 4 bases the same way I turned them round in the chuck and faced off the other ends in one go to hopefully get them all exactly the same height.



With hindsight I should have realised this probably isn't going to be the best way of doing it but it seemed ok at the time, the intention was to get 4 bases having both ends parallel, the sides radiused part way and all the same size to hold in the chuck later (these radiused sides are ultimately to be waste material and only to aid centring in the chuck).



Once drilled and 5/16 brass bearing blocks added it should now be a simple matter to turn the sides parallel. With the steel bearing top centre drilled and the other end of the work piece held by the machined radiused waste not much can go wrong, or so I thought.



Clearly I've gone wrong some where at the finished article looks like the Leaning tower of Pisa.



Admittedly there is the waste material to take of the bottom and reface it and I can thin down the top steel bar a bit but there is still a slight skew. I should imagine it would still run ok as the crankshaft does turn nicely and the hole does appear nicely parallel to the sides and base but I'm reluctant to use the same method to make the other 3.



It's not the end of the world and it is a learning curve but if anyone has any comments or ideas of how to go about making the other 3 I'd be really grateful as at the moment I'm completely stuck..

Many thanks
Peter.




« Last Edit: March 16, 2016, 03:55:43 PM by Gas_mantle »

Offline Gas_mantle

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Re: Making a small marine steam engine the beginners way.
« Reply #24 on: April 08, 2016, 03:31:34 PM »
Hi,

Having been a tad under the weather recently I haven't gotten as much done as I would have liked nor have I taken many photos but for the benefit of anyone following this simple build I thought I'd update it with the progress so far.

I decided to abandon the crank bearings I was making and after a bit of advice from other members I opted to remake them a lot shorter and improve on the accuracy. The second attempt is a vast improvement :-



With the crank fitted next job was to start on the 6 supporting pillars, I've done 3 so far and at least it gives me some idea of how the model is starting to look - the following 2 photos show the progress to date and so far I'm reasonably happy with how it's taking shape.

I'd have liked it to be a bit shorter but with hindsight I think I should have made the pistons stroke smaller - it's a bit late now so I'll have to learn to live with it.

It looks like the cylinders don't sit right but it is just that they weren't secured in place when I took the photos and I had noticed they weren't seated correctly.





The cylinders operate nicely on an airline and the crank turns nicely so I'm hoping with a few minor adjustments nearer to completion it should be a runner :-)

Peter.

Offline sbwhart

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Re: Making a small marine steam engine the beginners way.
« Reply #25 on: April 14, 2016, 06:46:41 AM »
That's coming on well Peter i like how you made the bearings and crank shaft.

 :ThumbsUp: :ThumbsUp: :ThumbsUp:

Keep up the good work

Stew
A little bit of clearance never got in the way

Offline zeeprogrammer

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Re: Making a small marine steam engine the beginners way.
« Reply #26 on: April 14, 2016, 11:06:51 AM »
Glad you're feeling better Peter.

I like those columns. (Whole thing looks good.)
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Zee-Another Thread Trasher.

Offline Gas_mantle

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Re: Making a small marine steam engine the beginners way.
« Reply #27 on: April 14, 2016, 11:21:37 AM »
Thanks for the feedback guys  :)

It does turn with quite a bit of power on an airline but there are still a few tight spots to sort out, I may have to remake one of the crossheads which is causing some of the tightness if I can't correct things with a bit of filing.

It's funny you mention the supporting pillars, I thought the were too plain and wanted to make tapered ones but the topslide on my little machine doesn't have enough travel and I wasn't confident I could make a decent job using other methods.

I've made the rest of the pillars now and will update it in a few days time when I've got somewhere with the flywheel or the eccentrics ( not yet decided what to do next)

Peter.

Offline cfellows

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Re: Making a small marine steam engine the beginners way.
« Reply #28 on: April 14, 2016, 03:07:22 PM »
Nice looking build, Peter.  You do some nice work.

Chuck
So many projects, so little time...

Offline Bikerbob

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Re: Making a small marine steam engine the beginners way.
« Reply #29 on: April 27, 2016, 04:43:54 PM »
Peter

I am in the process of designing a model engine and found your approch to the steam chest appealing. Could you sketch all the passages in the steam chest and email to me <email address removed>
Thank you
Bikerbob

Edit Jo: Bob please send Peter a PM with your Email address rather than posting it openly on the forum. Web bots have a nasty habit of picking up Email addresses printed in the open and sending you lots of spam  :ShakeHead:
« Last Edit: April 27, 2016, 05:27:35 PM by Jo »
Bikerbob