Yorky's Twin Cylinder Beam Engine

[Yorky]

Here we go.

A friend of mine decided to make a Sterling Engine, we talked about it a few times and I started reading up on the subject. I was quickly hooked.

I have always had the desire to build a Steam Engine of some sort but lacked the skills, resources and finances to bring it to reality. I quickly realised that using the Sterling Engine I could build something that looked like a Steam Engine at a reasonable cost with my hand tools and lots of stuff from my "Really Useful Box Of Bits".

I settled on making a twin cylinder walking beam engine.

Taking the symmetry from the hugely popular tin can engine as a basis of a design, and for materials my complete lack of cans is made up by a reasonable supply of 2" and 2.1/2" copper pipe which is left over from a previous project.

Never one to take the simple route I always seen to end up over thinking problems and making them a lot more complicated than they should be. This project has started off being no exception. It seems obvious to me that the displacement cylinder should be made in three bits; hot cap, cold cap and pressure take off - then bolting them together. Using this philosophy if my cold water jacket does not function a I hope it will then I all I have to do is replace the water cooled cold cap with an air-cooled one - simple.

So I cut the 2" copper pipe into suitable lengths annealed the ends by heating them to cherry red and quenching tem in cold water and then formed the flanges.

This post is basically to prove that I have started. I already have lots of questions, but more about them tomorrow.

Toodlepip

Yorky

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[Yorky]

On the off chance that someone is thinking "how did he do that - here's how"

I took a 20mm platic chopping board and;
1) cut it into squares
2) cut a hole in them
3) glued them together to form a large block
4) cut the block in half
5) bolted them back together

The ones in the pictures are for 2.1/2"

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[Ian S C]

Yorky, interesting form of construction, I'll follow along as you build your motor.
Copper is not really the ideal material, it conducts hear too fast from the hot end to the cold end. Also when heated it looses it's strength, also with heating it corrodes and flakes of copper oxide come off it, both outside, and inside.
Well built it should work.
Ian S C

[Yorky]

Ian -Thanks for the feed back.

The conductivity of copper is one of the reasons I picked it.

I am a novice at these engines and I am relying on posts here and else where on the Web, many of which seem contradictory. However, one statement seemed consistant; namely, keep the hot end hot and the cold end cold.

The main reason for the three piece construction was to provide the option of one or two thermal break(s) between the two ends and reduce the amount of heat transfer that you describe. To help achieve this I am intending to add some form of thermal insulation each side of the power take off.

To me copper seemed a favourite choice, allowing the maximum heat conduct into hot end of the displacement cylinder and the maximum amount of heat to pass through the walls of the cold end into the water cooling jacket.

I will bear in mind all that you say and I appreciate the time you take to respond. To negate the fact that copper may not as succesful as I hope, I have already put the word out for paint cans.

Question - Anybody have a good sugesstion for a good material/thickness for the insulation at the thermal breaks?

Toodlepip

Yorky

[Ian S C]

The ideal metal for the hot cap is stainless steel, heat conduction is no problem, it's only got to go the few thou, the thickness of the cap, the thing you don't need is the conduction of heat length wise toward the cold end. With a steel/stainless steel hot cap I use no insulation between the hot cap and the cold end. Any insulation between the hot cap of your motor, and the next stage will need to cope with fairly high temperatures.
You have a wee problem with design (ideal design), the displacer should be vertical to allow heating the end with out the copper distorting, ie a horizontal one will droop with heating, even a stainless one will eventually. The other problem is the heat conduction, if the displacer hangs down vertically the heat rises, but this is about the only way to have it if you are heating with meths or similar. My favoured way is vertical with the displacer pointing up, and fired with gas.
This is my free piston motor, with the heater at the top of the displacer cylinder.
Ian S C
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[Yorky]

My initial research was very narrow and I only looked into builds that I wanted my engine to look like - Victorian beam engine and slow running - calm and peaceful.

My two favourites have a displacers made of balsa and florists foam wrapped in aluminium foil. They seem to be working OK maybe it will be for a limited time?

I cannot see me ever having a gas fired engine or building a high reving motor. I am working with basic hand tools only, thats what I enjoy.

My reading scope is now expanding and have started to take an interest in other types of Sterlin Motors. I think can just about make out some of the important bits on yours but where is the Flywheel?

[Ian S C]

A ha, Yorky, you missed the free piston bit, these motors have no crankshaft, the work from the power piston works against a spring, this can be a mechanical spring, or a gas spring, or as in this case using two magnets with like poles facing each other, at the base of the motor you can see the coils that form the linear alternator, and the transistor radio that it powers. The displacer works on the principal used in Ringbom motors.
Ian S C
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[Yorky]

My posts must seem mundane after reading about Gas and Magnetic springs, ringbom motors and linear actuators, but fly wheels hand carved from left over laminate flooring is the best that I can do.I will keep reading Ian - I promise. But I still think your engin would look better with a flywheel

Building the displacer cylinder came to a complete stop, the Aluminium offcuts that I was intending to use for the flange backing rings were not as big as I remembered. I have ordered some more sheet Aluminium and in the meantime started on the Flywheel.

Mum had a couple of sheets of flooring laminate left over from her kitchen makeover and I kept.

Decided to try a 10" flywheel. Armed with a coping saw and a couple of files; three evenings later.....................

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First go just looked like a piece of flooring laminate. so I cut a couple of doubler plates for the rim.

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With a paint job, it now has the possibility of looking like a flywheel.

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Currently hunting for some bearings locally, my town must be the only one in the UK that does not have a skate board shop.

Toodlepip

[Ian S C]

You can usually find 6 mm bearings in old VHS recorders, I suppose that they are, or have been chucked out over there. A source of 8 mm bearings (not the best bearings) is Fidgits, I got two for $NZ 1 each, less than 50 UK pence.
That fly wheel looks good, it should be quite adequate. I had a motor with old CDs for a fly wheel, my second motor used the hand wheel of an old sewing machine. Most of my fly wheels are made the same way as your one, except they are made of 8 mm steel plate.
Ian S C

[Yorky]

Great minds think alike.

While I was trolling the various one pound shops today, I stumbled on some "Fidgits" - roughly the same price that you paid, £0.50.

So for £0.50p I got;

1) One very spinnable 8mm bearing.
2) 3 x 8mm bearings that feel as if they are filled with gravel.
3) A ready made bearing housing - This is the best bit, keep it and throw the rest away if you like.

Within an hour of getting the fidgits home, I had a very workable test rig for balancing the flywheel. I could see the improvement for every adjustment I made. The wheel spins for longer and longer . I am seriously chuffed

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(edit) I forgot to mention I swapped the free spinning bearing with one of the grinding variety at the periphery.

[thanh-cuibap]

very nice .

[Ian S C]

That's a neat way of setting up your crankshaft. If you read a bit about building Stirling Engines, you will come across a bit about removing the shields on bearings, and washing out the grease, these bearing don't have grease. If need be some very light oil, just a very small drop can be used, but it all causes drag.

[Yorky]

I will risk not oiling them.

I sent my wife back to the shop and she bought me 10 more Fidgits. In the event that I damage the bearings I have 40 spares.

Toodlepip

[Ian S C]

There is a wide range of fits of the bearings, so you should be able to find a few good ones. One of the two stove top fan motors that I built has used skate board bearings that are so worn I afraid the balls might fall out. That motor is unusual as Stirling Engines go, it's too powerful, the gyro effect of the fan causes the motor to sit on the stove and bodily rotate, also it's a Ringbom motor(free displacer) the displacer makes quite a bit of noise.
Ian S C

[Yorky]

I had a couple of bits of 6mm aluminium in the shed.

Decided to carve them up and maker proper bearing blocks, it makes mounting and demounting the flywheel a lot easier.

Still work to do on them but getting there.

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I have been undecided about the method of making the piston. Today mum asked me to buy some denture cleaning tablets. The tube they came in is very nearly a perfect match for 1" copper patch. ( All UK sizes ). Basically scape off the paint and a quick rub with emery paper and the job is done.

I cut off 3/4"of the bottom of the tube, added a couple of 1/8" brass sleeves for the gudgeon pin, filled the piston with epoxy resin. The con rod is only a quick fix made from brake tubbing to allow me to lap the piston and cylinder.

It seems to do the job, the piston flys up and down the tube with very little huffing and puffing.

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Toodlepip