This is a pretty cool stirling motor. I started wondering what it would take to model the curved spokes of the flywheel. Once I figured that out, the other pieces were pretty easy so I just went ahead and modeled the whole thing. The material requirements are pretty simple. Just some 1/4" 1/8", and 1/16" aluminum flat stock and common hardware.
The only tricky part is the acrylic displacement cylinder. The stuff is about $45/foot on McMaster Carr. I was thinking I could cut a glass jar if I could find one the right diameter. This will require a modification to the design because the original author had the screws holding the top and bottom plate going directly into the acrylic. Instead, the plates would have to be enlarged to allow the screws to go outside the glass similar to how I've shown it in the model.
I've been hunting around for glass jars. A wine bottle, even a magnum, is too small. A one-gallon pickle jar from Sam's club is big enough and at only $4.50 (including the pickles) is a real bargain. But it's quite a bit bigger and would require the top/bottom plates and the inside components to be upsized. A coleman lantern globe is almost exactly the right diameter. They're about $9 at Walmart so I might try cutting one of those.
File:Assembly.fcstd This is the freecad assembly file. It's useful for exploring the model but not for making changes. Each of the subcomponents is in its own file and then exported as a .stp file to make this assembly. I'll upload the subcomponents if anyone wants them