Currently building vertical steam engine number 3. First was a scratch built 2x version of one of Rudy K's design having a Delrin cylinder and piston without rings in a close fitting bore that runs fine on CA, 2nd is a bottle style frame engine with a cast iron cylinder, Delrin piston without rings that also runs fine. Both engines have enough torque to require a firm hand grip to stop rotation, 3rd engine I am building is also a vertical frame(stewart) type design also having cast iron bore with a Delrin piston with a 1/8th dia. O ring on the piston. As this is my first attempt at an O ring piston I could use any advise from others who have experienced this type of combination cylinder and piston. Any rule of thumb as to what depth of groove is suitable for the piston with the O ring? First trial O ring fit is with the O ring extending into the cylinder about .005 larger diameter than the piston. Fit in the cylinder seems adequate, question is will that provide enough compression to run the engine on Compressed air?
When you cut the groove in the piston for an O ring is it advisable to use a rounded radius tool or use a flat tool for a flat groove, or does it matter? How much under bore size should the piston be with an O ring type piston. Any thoughts and experience on O rings and piston clearance would be appreciated.
Thanks.
Bob