I wrote :

"Thanks for responding, Peter. The groove as designed by Gordon Watson, is smaller than the ID of the Oring. This led me to believe that it is undesirable to not allow compression (from contact with the bore of the cylinder) to the inside of the Oring. By increasing the groove OD to enlarge the Oring OD, you capture the Oring between ID and OD. It is my understanding (and I could be wrong) that this is not the way Orings are designed to work, as it would increase friction unecessarily. But if this is OK, then you bet, I'll make new pistons rather than new cylinders.

PS. the Orings supplied by Gordon Watson (viton) were the correct OD (.438). I bought some Buna-N orings at the local tool supply store and they are undersize. I concluded that they wouldn't work UNLESS the OD of the piston groove were increased to bring the OD up to .438. Again, I ruled this out based on the logic above. But if it is OK to capture the Oring, please let me know before I make new cylinders. "

Thanks to Clark, Harry etc on other issues raised . . . .  .
but does anyone have any thoughts on the above problem ?

royce



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