Inspired by the thread Stew posted, I decided to try making one of Elmer's rocking piston engines. As usual, I just couldn't leave good enough alone, and made some of my own changes. The most obvious one was to bore the cylinder through, and add an end cap like Mklotz of HMEM did. The cap is actually 2 pieces, with the tube threaded into the end of the cap. The second was because I didn't have any flat head screws, so I bored out the crank and used a button head. The base is not attached by a screw, but press fit and cold riveted over. I also soldered the bushing into the side, after running it and finding it flopping all over.
My first running engine, which happily ticks over on less than 1 P.S.I. I can actually keep it going on lung power alone, but that will make you dizzy in short order. At 20-25 P.S.I. it screams along like a weed wacker.
I only had to remake 2 parts, which is astounding in itself. The first was the shaft, because I tried to use drill rod, and snapped the tap off in the end. Remade in brass. The other was the inlet tube, which I single point threaded 6-32. When I drilled the through hole, it broke through the minor diameter of the threads. So, I refaced it, and cut the threads to 8-32 instead.
Runs pretty nice (sounds exactly like Stew's in his video), and was a big hit this afternoon with the neighborhood kids. They especially liked it when I ran it wide open on 25 P.S.I. I'm pretty impressed that I got the whole thing done so quickly, and that it ran right away.
