This is a hot air engine I built for my father for his 83rd birthday several years ago.
Made from mostly stuff in the scrap bin, a piece of channel, a piece of square tube, a sink tailpiece, skate bearings, molten scrap aluminum, and some bits of brass.
But possibly more exotic is the graphite piston, and more unusual is the nearly zero connecting dead space between displacer chamber and power cylinder.
This last was achieved by offsetting the two cylinders until they were nearly tangent, with only a small overlap. Holes to fit the cylinders were stop drilled and bored into the massive aluminum rectangular heat sink. these two holes meet and stop in the middle of the sink. so the two cylinders bear against each other, and their axial overlap becomes the connecting passage of zero axial dimension.
There is still a little headspace at the top of the power piston and some around the displacer so I can't claim true zero dead space overall, but but there is none in passages.
Fun to work that out, anyway.
Ran really powerfully when I tried it out the night before I visited him down in Connecticut. And performed wonderfully at the birthday, party but I haven't run it since. So I can't give more performance details. He's not capable of running it himself any more. I also didn't take construction photos -- was in a rush to complete it in two weeks, working from early mornings into the wee hours every night.
Anyway, these are the photos I have.
