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Leak problem

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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Leak problem

Unread postAuthor: jitup » Wed Dec 31, 2008 3:27 pm

Hello I built the below cannon recently, and was not planning to unvail it until it was 100% finished, but I have come for help. the problem I a having is that I keep developing a leak between the end of the barrel and the end cap. I first used solvent glue to bond it, but it started to leak. Than I put a generous layer of JB weld on and then it did not leak for about 5 shots. after that I lightly snaded down that layer of weld and added a second over top of that. After 10 shots the leak came back. Please help me! I will also include a damage photo. the tin was only shot once from about 10-20 ft away, with a 1" potato slug (this was before I found the BB gun scope in my basement) it is very powerful using a Diaphram valve with an opening distance of 1/4 inch (at least that is what it is when not under pressure!)
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Attachments
barrel leak.jpg
here you can see the problem area
vulcan 22.jpg
tin shot 2.jpg
tin shot.jpg
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Unread postAuthor: FishBoy » Wed Dec 31, 2008 3:37 pm

I would get rid of most of the jb weld, and put some epoxy on it, it tends to do a better job of getting in to the little cracks, etc. that cause leaks. Plus the jb weld is ugly.
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Unread postAuthor: frankrede » Wed Dec 31, 2008 3:50 pm

FishBoy wrote:I would get rid of most of the jb weld, and put some epoxy on it, it tends to do a better job of getting in to the little cracks, etc. that cause leaks. Plus the jb weld is ugly.
jb weld IS epoxy.
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Unread postAuthor: Big Boom » Wed Dec 31, 2008 3:57 pm

I'm assuming that you let it cure for long enough? - I looked it up on their website and it says that it cures fully in 15-24 hours. Other than that, I don't really know.
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Unread postAuthor: jitup » Wed Dec 31, 2008 6:02 pm

I let it cure for 2 days, just incase. I would clean the JB weld up with sand paper before I paint. this is raw still. any other suggestions would be nice
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Unread postAuthor: Daltonultra » Wed Dec 31, 2008 11:48 pm

I'd suggest scrapping the jerried-up end caps and using some bushings in there instead. Use a Dremel or file to grind out the lip that keeps the pipe from sliding through.
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Unread postAuthor: ThumbzUpTheoden » Thu Jan 01, 2009 9:18 pm

If that is an end cap(which it looks like one) cut it of get a reducer bushing(looks like it is 2" to 1") and put the barrel in that. Then it won't leak.
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Unread postAuthor: jook13 » Thu Jan 01, 2009 10:07 pm

I say scrape away the jb weld. Then make sure it is clean and sandpaper the whole area to roughen it up. Then go to a store that sells epoxy and look for some epoxy that says it works with plastic. Most epoxy states on the package what type of materiels it bonds with.

Basically try again, but with a different type of epoxy. I have found that JB weld doesnt do so well with pvc, but maybe that is just me.
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Unread postAuthor: FishBoy » Thu Jan 01, 2009 10:13 pm

frankrede wrote:
FishBoy wrote:I would get rid of most of the jb weld, and put some epoxy on it, it tends to do a better job of getting in to the little cracks, etc. that cause leaks. Plus the jb weld is ugly.
jb weld IS epoxy.


Very true, I should have been more clear. Get some sort of marine or other typical expoxy, many stores sell 5-min epoxy in small double-syringes for cheap. The idea is that JB weld doesn't flow very well, so it wont get down into the small hole and seal it up, that's the problem.
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Unread postAuthor: jitup » Sat Jan 03, 2009 3:36 pm

Thanks for all the suggestions. I will try and use some plastic epoxy, and if that dosen't due the trick I will use a bushing
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