This is my Moving cylinder Stirling engine based on the design by Hubert Stierhof. It's made from 18mm ply board, I cut the frame from the ply and used the inside cut out as the displacer (suitably tapered). I've had it producing a tiny amount of power by connecting a stepper motor to it, it could just about light a small led! The engine works by the tapered displacer which can tip to either side, hot or cold which causes the air to expand and contract. This forces the balloon in or out, causing the displacer to tip to the opposite side, restarting the cycle.
The frame and displacer
so the it fitted well. I then planed and sanded the taper on the displacer. There is no pivot bearings
although it would probably benefit from one. I just pivots on the end of the displacer which is curved.
I think that the engine is too thin because the heat transfers quickly to the cold side, even if the engine
isn't running. It should probably be 40 - 50mm thick.
The outer plates are 1.2mm aluminium from an old monitor.
Here's a video of it running :
Stirling engines >