This is a small Low Temperature Differential engine I made years ago.
It's admittedly not very pretty.  I just wanted to make one to see it run, since
I'd never seen one except in pictures, but I found plans for one on the web.  I
scaled this one down from those plans to fit the lathe.  It was hard to come up
with the materials the plans called for, so in place of the type of foam needed
for the large displacer, I used foam board, (the kind used for mounting photographs)
which is a little heavy for the purpose.  There
was no graphite to be found anywhere near where I live, either, so I used some
type of plastic for the power piston.  Nylon, UHMW, or what else, I don't know,
but it machined nice.  The clear cylinder wall is from a large plastic drinking
glass I picked up at the grocery store. 

So, I didn't use the right materials.  The silly thing still runs, although it needs
to start cold and will only run about five minutes at a stretch.  Then the  plastic
power piston starts dragging in its' cylinder and the engine stops.  Let it cool
and it will run again.  It's not as interesting as watching a steam engine run.  At
least not for me. 

This is the only one I ever made.

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Copyright  Dean Williams