Don't want to hijack here so Stew, send me elsewhere if it is! David, no. not a diaphragm, it's a just a big square displacer cylinder.
My daughter and I tried getting the smaller one running -- it has sat unused for about 3 years I reckon. After fiddling around with it, we took it apart finally, and substituted the old foam displacer, and got it running again.
It has mostly aluminum sliding parts, and they were definitely not running together well. I didn't build this one, and it looks like it could really use a "David style" rebuild. The gland leaks for sure, and the aluminum power piston in aluminum cylinder just isn't good -- I did find a good sized divot in the inside of the cylinder near the top -- must have always been that way -- anyway filed it down. We did get it running -- but it could be a lot better.
Maybe I will work on that big one -- you guys are getting me caught up in this, too! Getting the first one running brought back some of the fascination with seeing something sit on top of a cup of hot water running for a half hour. It's weird to walk away from something like that, forget about it for awhile, and come back in the room and see it is still running.
