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Leaks...

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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Unread postAuthor: Counterstriker » Fri Mar 28, 2008 8:03 pm

I am pretty pissed.. I just got done everything for my piston cannon, But I am running in to problems.. If you don't what cannon I'm talking about look at the link in my sig. Ok so the piston was set and I put the seeling face on it, I epoxied the barrel to the reducer, And I attached the multiple pieces with teflon tape.. But everytime I pump it up there is a new leak..the teflon tape is not doing squat. I keep taking the leaking part off and applying more or less tape to it but then there seems to be a new leak.. Any help? Is there a "right" way to teflon tape stuff? I am gonna guess you will say.. epoxy but I didn't want it to be permanent.

Thanks 8)
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Unread postAuthor: Brian the brain » Fri Mar 28, 2008 8:08 pm

Hold the piece you want to tape in your left hand, the threads pointing to the right.Roll the tape on OVER ( NOT UNDER!)the threads and make it stretch as much as you can without breaking it.After you have aplied 3-4 layers, break the tape.
Rub it on with your thumb, again, OVER the threads.

This should ensure the tape doesn't unwind as you thread it in.
I use tha technique and do not experience leaks at 900 psi...
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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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Unread postAuthor: DYI » Fri Mar 28, 2008 8:14 pm

What BtB said is the correct method.

How are you tightening the threads? With an 18" or larger pipe wrench turning, and braced against the floor with another wrench, you should be able to exert more than enough force to adequately seal the threads.

I've never had any problems with 35 bar nitrogen, and BtB is using ~63 bar, so the quality of the threads certainly isn't the problem.
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Unread postAuthor: Counterstriker » Fri Mar 28, 2008 8:23 pm

Thanks for the responses. I will retry what you say BtB, And DYI the pipe is 3/4" and I tighten it holding it in a vice then with a wrench.
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Unread postAuthor: DYI » Fri Mar 28, 2008 8:29 pm

I tighten it holding it in a vice then with a wrench.


Well there's your problem... :roll:
You do know that in general, the correct usage of pipe wrenches (it'd better be a pipe wrench) is to grip the pipe or fitting with one, and then grip the part that you're turning with the second one, and tighten it with the first wrench braced against the floor, right? Vises are only useful if you have hex fittings, and even then it's kind of dubious.
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Unread postAuthor: Counterstriker » Fri Mar 28, 2008 8:33 pm

How do I grip the chamber? It's a round 3/4 nipple.

(Btw do they sell springs at homedepot?)
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Unread postAuthor: DYI » Fri Mar 28, 2008 8:37 pm

How do I grip the chamber? It's a round 3/4 nipple.


:shock: If it wasn't for my current projects, that one would be going in my sig.

What's so difficult about gripping a 3/4" pipe nipple with a pipe wrench? Is this nipple some sort of ridiculously soft plastic that the teeth slip through, or what?
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Unread postAuthor: MrCrowley » Fri Mar 28, 2008 8:37 pm

Counterstriker wrote:How do I grip the chamber? It's a round 3/4 nipple.

(Btw do they sell springs at homedepot?)

With one of these:
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Unread postAuthor: Counterstriker » Fri Mar 28, 2008 8:42 pm

Yes I own one. I didn't want to ruin the smooth finish on the tank.. but what ever.
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Unread postAuthor: DYI » Fri Mar 28, 2008 8:43 pm

A cloth between the teeth of the wrench and the pipe/fitting could help with the aesthetics, but it won't do wonders for the grip.
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Unread postAuthor: MrCrowley » Fri Mar 28, 2008 8:44 pm

The vice would ruin the 'smooth finish' anyway.

The plumbing wrench's aren't too bad with teeth marks. If you're that paranoid just wrap it in a towel and stick it in the vice.


Edit: <A HREF="http://www.youtube.com/watch?v=bSOYvDZ_jIw">F*cking eh</a>, beaten again :shock:
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Unread postAuthor: D_Hall » Fri Mar 28, 2008 8:47 pm

If you don't want to use a pipe wrench, sometimes you can get away with a strap wrench.... but don't bet on it.

Also, something to keep in mind with teflon tape. Strictly speaking it is NOT a thread sealant like so many folks seem to think it is. It is a LUBRICANT. It allows you to tighten the connection to the extent that the threads do what they're supposed to do all on their own... seal!

So why can't you use oil instead of teflon tape? It would, after all, eliminate the worry about the correct way to use it.

Answer: You can!

Teflon tape is popular in the world because it's safe and non-toxic and all that jazz which means it's ideal for plumbing (tap water is going to be consumed and all that). But for a spud gun - where you aren't going to be eating stuff that passes through the pipe? A light oil will work too.



edit: Oh, and if you're working metal/metal? The BEST thing I've ever seen is blue Loc-Tite. While wet it acts as a weak lubricant but when it cures it acts as a sealant. Don't use it on plumbing and such (there's that whole toxicity thing), but for spud guns of metal construction it simply can't be beat. I have NEVER seen a joint that used Loc-Tite leak. NEVER.
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Unread postAuthor: Counterstriker » Fri Mar 28, 2008 9:52 pm

Ok thanks guys. I am pretty sure problem is solved for now.

Does anyone know if they selled springs at homedepot?
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Unread postAuthor: starman » Fri Mar 28, 2008 10:32 pm

Counterstriker wrote:Does anyone know if they selled springs at homedepot?


Some few, not a very good selection however. Check in the hardware (screws and nails) section. Some gate and screen door closer hardware have some springs included that might be useable. If I remember correctly most are tension rather than compression springs.

You may have more luck at your local hobby shop where they specialize in model airplanes/cars/trains.
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Unread postAuthor: BigGrib » Sat Mar 29, 2008 6:25 am

My two cents, umm, first I agree use a strap wrench. I do and it works great. You gotta get the crafstman ones though. Other ones suck. As far as the leaking, ever hear of RTV/silicone? I use black rtv. works great. just coat the threads and screw together. i like it especially for going from pvc to metal.
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Yea, that's definitely going to get you at least a tazer.

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