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My barrelsealing valve leaks in an odd place. Got any ideas?

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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My barrelsealing valve leaks in an odd place. Got any ideas?

Unread postAuthor: c19o » Wed Aug 01, 2007 11:06 pm

My barrel-sealing valve leaks in the spot shown in the picture. Ive tried sealing it with pvc cement, JB, and epoxy the leak still eventually comes back. Maybe its a flaw in my gluing? Im thinking of making a whole new valve, but before I do I'd like to see what you guys got to say.
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Where the leak is.
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Unread postAuthor: mopherman » Wed Aug 01, 2007 11:11 pm

Did you secure your female adapter with skrews? I would just remake the valve.
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Unread postAuthor: c19o » Wed Aug 01, 2007 11:13 pm

I glued the adapter into the tee and no I didn't use screws because i didnt need any there.
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Unread postAuthor: hi » Wed Aug 01, 2007 11:16 pm

have you tryed super glue?

you make just want to redue it because sometimes leaks mean it isnt a good solvent weld.
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Unread postAuthor: c19o » Wed Aug 01, 2007 11:18 pm

Nope i havent. I will tommorow after i scrape out all the JB.
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Unread postAuthor: noname » Wed Aug 01, 2007 11:43 pm

You can try to find a really strong spring, put it behind the piston to keep it sealed, make yourself a vacuum pump, put some sealant over the leak, and put a vacuum inside the chamber.
Or you could remake it.
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Unread postAuthor: c19o » Wed Aug 01, 2007 11:47 pm

Well if super glue doesnt work tomorrow ill try that. Thx
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Unread postAuthor: mopherman » Wed Aug 01, 2007 11:47 pm

noname wrote:You can try to find a really strong spring, put it behind the piston to keep it sealed.
Or you could remake it.

Couldnt you just remove the piston and cap the barrel? Good idea with the vacume though.
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Unread postAuthor: dongfang » Thu Aug 02, 2007 1:06 am

Ho Mopherman

From where will he apply the glue, then?

Nice valve. I had the same problem with my first one - but that was different because my valve seat is not solvent welded / glued into the tee, but just rests on the female adapter with some silicone in between. It worked fine, until I got a barrel pushed in too far... but then, I could just pull the piston and seat out the pilot end, and redo the seal.

I tried to solvent weld the seat on just like you in my first try, but that became a disaster: I had just assumed that the tee was perfectly straight, and that the tee should have 90.0000 degrees between front and sides.

EDIT:
and that the tee should have 90.0000 degrees between front and sides
I did mean the seat fitting, not the tee.

Not so. AND the solvent glue also tends to make things expand, pushing my valve seat down towards the chamber. I ended up with the piston hitting the seat at the bottom with still a 1 or 1.5 mm gap at the top.

If you have to redo, you can consider a seat that just rests on the adapter in the front. Just make sure that the barrel doesn't push it backwards.

My idea for a repair: Apply the glue from inside the valve. Maybe something like: Remove piston and anything fancy on the valve seat that it seals against. Fit a plug (wood and silicone, whatever) into the seat fitting. Rub some o-ring grease or hand soap on everything inside the valve that you don't want to be ruined by glue.

Locate the entrance end of your "leakage tunnel"; it must be at the end of the valve seat. Put a strip of slow glue (standard epoxy, not rapid) there (or apply plenty of it evenly all around the seat fitting) Put pilot cap on, pressurize a tiny bit, until you have it leak again. See from where glue was "consumed" and put some more there. Pressurize again, but now release air before it starts to leak again.

Wipe away the epoxy mess in the valve with rubbing alcohol. Cross fingers.

I wouldn't worry too much about a bad solvent weld on the seat, as long as the one of the adapter is good.

Regards
Soren[/quote]
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Unread postAuthor: c19o » Thu Aug 02, 2007 11:56 am

That would be kinda hard because that valve is the kind with a female adapter on the back and a reducer screwed into that. hmmm, I'll have a friend suck on the pilot ball valve and apply epoxy on the leak. At 100psi it loses at most 5psi a second.
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Unread postAuthor: dongfang » Thu Aug 02, 2007 12:06 pm

Ok, you have your friend suck ... when reporting back how it worked out, don´t need to go into as much detail as I did, hahaha

So you can´t remove the piston? That .. sucks.

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Unread postAuthor: c19o » Thu Aug 02, 2007 12:07 pm

I can, remove it the reducer is threaded. Ok then, I'll scrap off all the JB weld now....
lol what you said didnt sound right
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Unread postAuthor: dongfang » Thu Aug 02, 2007 12:15 pm

I´m working on my piston valve #2 right now, too. What a (strange) brotherhood we are....
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Unread postAuthor: dongfang » Thu Aug 02, 2007 12:22 pm

Oh, and if you feel sorry for your friend sucking (and possibly inhaling the fumes of your cement), consider a vacuum cleaner!

"Nothing sucks like an Electrolux", went the slogan of the Swedish appliance company as they tried their luck on the US market some decades back. Despite the attention they got, it wasn´t a great success....

(It´s a TRUE story .. in Swedish, there are no special connotations to that word; on their domestic market it was a perfectly good one. I remember seeing it in Danish, too. But they should have asked someone before that English translation...)

Regards
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Last edited by dongfang on Thu Aug 02, 2007 12:24 pm, edited 1 time in total.
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Unread postAuthor: c19o » Thu Aug 02, 2007 12:23 pm

Lol im glad i found a part to a vacume cleaner attatchment today.
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