Jaxa Low Temperature Differential Free Piston Stirling

This was a kit that required no machine work, but it was fun anyway. It runs on a cup of coffee:

The box came straight from Japan via eBay...

Pretty simple set of parts. The celluloid plastic are "springs"...

It was running, but the camera stopped it. Click for a QuickTime movie...

If you want one, search for Free Piston Stirling on this eBay Store