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O-ring friction issue

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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O-ring friction issue

Unread postAuthor: wyz2285 » Thu Apr 16, 2015 2:23 pm

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.
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Re: O-ring friction issue

Unread postAuthor: Brian the brain » Fri Apr 17, 2015 2:37 pm

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!!
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Re: O-ring friction issue

Unread postAuthor: wyz2285 » Fri Apr 17, 2015 2:45 pm

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!
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Re: O-ring friction issue

Unread postAuthor: Brian the brain » Fri Apr 17, 2015 3:00 pm

Two O-rings will keep the lube in.
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Re: O-ring friction issue

Unread postAuthor: wyz2285 » Fri Apr 17, 2015 3:04 pm

Exactly my thought, just seemed a bit skeptical about it, wasn't sure if pro> con
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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