I think I kind of got this thread hijacked and I did not mean to. If I should stop adding to this thread would someone let me know.
Anatol, Sometimes the rotary valve is part of the crank. In Rudy's case he called it ( the valve ) but I think of it as the rear half of the crank. On the twin cylinder that this thread featured I think of it as a camshaft with flats rather than lobes although the author said he filled the shaft rather than milled it. The seal is as good as you are at making a shaft a perfect fit in a bore. The materials can be different combinations. I typically use either steel/brass or brass/aluminum. My engines get very little running time and I would guess they have little to no wear. Did you mean to say Delrin piston. That engine is not mine but rather some other guys version of Dave's. I do use some of the high performance plastics for pistons on most of my engines because they are self lubricating but you do need to pay attention to their coefficient of thermal expansion so your engine won't seize when the room temperature rises. Teflon has the best coefficient of friction but the worst for expansion. I do not run any engines on steam.
terryp, If you are referring to the V-twin it is not a Elmer engine but rather David Kerzel's. Mine was copied from his plans but with many changes such as double scale, rotary valve, square cylinders and cylinders in line like a Harley rather than staggered like David's. Gary
