My stirling engine school project

[User1]

He seems to do it alright:
https://www.youtube.com/watch?v=lvvyjJ8wz3Y<
https://www.youtube.com/watch?v=Cf81MzO6Zj0

[User1]

Also, I'm not looking to make a fast or efficient engine, I am making it for a project where I am going to show people that the Stirling engine actually exists and works.

[Ian S C]

A good demo motor would be one third of the motor in the video, it's hard to know what is possible in another country, most of my work is done with found materials, a few bits are bought in, quite often I make my own bolts and nuts if I don't have the right size.
Obviously if you can't make a fitting piston, a diaphragm is the way too go, I like the ones in the vid.
Ian S C

[User1]

If I switch do diaphragm, would I have to shorten the cylinders? What should it look like? Does the Diaphragm just substitute the piston?

[Ian S C]

If you can't machine, or other wise form two cylinders and fitting pistons I would suggest forgetting the ALPHA type motor, and build a GAMMA motor in which the power piston can be replaced with a diaphragm. The ALPHA motor does need a bit of extra work.

Ian S C

[User1]

Would a Gamma Stirling engine have to resemble this?

[Ian S C]

Roughly, the displacer is 1.5 times the power cylinder ie a ratio that you will come across if you read much on Stirling Engines ( 1.5 : 1), In this form it is as simple as it gets, and the power piston can be replaced with a diaphragm. With tin can motors the displacer is usually a bit bigger than the 1.5 : 1 ratio to allow the motor to run on lower heat. On your diagram the power cylinder with the diaphragm can be much shorter. Where the rod comes out of the displacer cylinder there needs to be a seal to restrict air leakage, if you have not done it yet, read Boydhouse's simple motor plans in the thread at the top of the index page of the forum.

Ian S C

[User1]

Is that okay?

[Ian S C]

That looks ok, but you may find it easier to heat the hot end if you lay it down so that the displace is horizontal, or even a bit further so that the displacer is hanging down, and you can put the heat source under the end. The last way does make the crankshaft rather high, but if you look for pictures of the old motors this is how they were built so they could have a coal, or wood fire under them.
Ian S C

[MikeB]

That diagram still shows a large space behind your diaphram, which will be detrimental to the performance of the engine - make that as small as possible, so that the pipe essentially just goes straight onto the back of the diaphram.

[User1]

I'm planning on my engine to have 2 sets of cylinders(2x Power, 2x displacer), i have a question about the crankshaft.

Should I offset 1 of the cylinders by 180 degrees?

[User1]

This is what I've had in mind

[User1]

Front view

[Ian S C]

Looks a nice compact design.
Ian S C