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O-ring friction issue

Posted: Thu Apr 16, 2015 2:23 pm
by wyz2285
Long time no see guy, hope you all well.
I have been into small bore pneumatic a lot lately and I was making sort of balanced hammer valve (pic 1).
The problem I'm having is with the green o-ring, it jams sometimes.
The valve stem is smooth when no pressure is applied and during the first couple shots it's all good to. But once the lub wear off (I guess with each burst of air dries it a bit), sometimes it gets stuck. I gave tried various valve stem diameter and several sized o-rings, some of them last longer some not really.
I still haven't yet tried free floating o-ring (haven't found the right sized o-ring). I'm about to order the o-rings so I have a question: for a good, long lasting seal and low friction, should I use thicker o-rings or thin ones? (example, the port is 6.5mm, I have the choice of 6.5mm OD 1mm cross section o-ring or up to 2mm cross section o-ring). Thinner o-rings requires a more precise machined piston so it wouldn't get blow out but I tired one and it works nice though.

Re: O-ring friction issue

Posted: Fri Apr 17, 2015 2:37 pm
by Brian the brain
Use two O-rings, each in their own groove.
Make sure they are not squached against the outer wall by the bottom of the O-ring groove.
That would be too tight.
They should touch the wall because of their size, not because they are pressed against the surface.

It worked on mine.
And...don't stay away too long!!

Re: O-ring friction issue

Posted: Fri Apr 17, 2015 2:45 pm
by wyz2285
Why two o-rings? I did just made one before seem your post but I'm king of worried about "double" the friction.
Free floating is the key looks like, time to lathe a couple to test out!

Re: O-ring friction issue

Posted: Fri Apr 17, 2015 3:00 pm
by Brian the brain
Two O-rings will keep the lube in.

Re: O-ring friction issue

Posted: Fri Apr 17, 2015 3:04 pm
by wyz2285
Exactly my thought, just seemed a bit skeptical about it, wasn't sure if pro> con