Jim wrote, re Royce's problem:- > You're correct Royce, that O rings are designed to fit in xx" groove, there > are charts available to tell you EXACTLY what groove to make. But I think > Peter's spot on with the piston idea, you're only changing the size of the > oring a few thou and that should not be a show stopper. Experiment and run > under air for an hour or so to see how that oring seats.
For the last 15 years, I've been fitting O rings as follows:- 1. The groove must be one and a half times wider than the O ring to allow it to roll. 2. The depth of the groove must allow an interference fit of about 0.004" to 0.006" to provide a good seal at the pressures we use for our small locos. This works! Note that the actual diameters of the piston or cylinder are not critical - it is the difference between them that needs to be spot on. The O ring will expand or be compressed to fit (within reason.) Mike
