Finding and sealing piston leak

Cannons powered by pneumatic pressure (compressed gas) using a valve or other release.
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boyntonstu
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My gun was leaking.

I pressurized it to 100 psi and dipped the muzzle into a bucket or water.

Nice bubbles.

I surmised that the leak was through the machine screw threads holding the rubber washer to the Oak piston.

A little dab of $3.75

Image

Problem solved.

BoyntonStu
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roboman
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That stuff works so much better than Teflon tape... the only problem is, it doesn't dry, and is very sticky. One time, I took a simple pneumatic to the beach, and the entire rear end was covered in sand, after only a few hours.
ilovetoblowthingsup wrote: The yellow/orange back fits super snugly, very nice in fact, but the head does not fit.
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boyntonstu
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roboman wrote:That stuff works so much better than Teflon tape... the only problem is, it doesn't dry, and is very sticky. One time, I took a simple pneumatic to the beach, and the entire rear end was covered in sand, after only a few hours.
I applied it inside the gun.

Did you wipe off all the excess that showed?

After you screw everything together, you shoudn't see any of it.
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qwerty
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Seems good im suprised it worked on wood might have to get me some of that stuff :) as it seems that teflon tape can be a bit hard to get to seal.
I visit occasionally to make unrelated posts.
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roboman
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boyntonstu wrote:
roboman wrote:That stuff works so much better than Teflon tape... the only problem is, it doesn't dry, and is very sticky. One time, I took a simple pneumatic to the beach, and the entire rear end was covered in sand, after only a few hours.
I applied it inside the gun.

Did you wipe off all the excess that showed?

After you screw everything together, you shoudn't see any of it.
I got as much of it as I could, but it seems to have left a sticky film on all of my threaded parts.

Now, I need to wash off my cannon. :?
ilovetoblowthingsup wrote: The yellow/orange back fits super snugly, very nice in fact, but the head does not fit.
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inonickname
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I use a teflon tape rated for gas (OMFGWTFBBQ NOTHING IS RATED FOR GAS) and it states 2 overwrap for 1/2" and under, and 6 for 3/4" and over. I find 2 doesn't work, so I use a lot on anything that has to be leakfree. It's rated to 2.6 mpa working pressure (380 psi) and seems to work fine at 400 just as long as it is overlapped enough.

I've never found pipe dope anywhere near me, but there is loctite thread lockers and retaining compound which is nearly permanent.
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Ragnarok
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roboman wrote:... and the entire rear end was covered in sand, after only a few hours.
Must quote to stop Jack deciding to give his commentary on this double entendre.
inonickname wrote:I've never found pipe dope anywhere near me.
Try the man on the street corner.
Does that thing kinda look like a big cat to you?
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boyntonstu
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qwerty wrote:Seems good im suprised it worked on wood might have to get me some of that stuff :) as it seems that teflon tape can be a bit hard to get to seal.
I did not try it as a seal primarily to the wood.

A machine screw goes through the wood and through a rubber washer.

The dope was used to seal the screw threads and the nut to the rubber.

However, you may be correct in that it may also seal to the wood.

I purchased it at Home Depot.

Try it and let us know.
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