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Need answer ASAP

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: FishBoy » Wed Jul 02, 2008 10:33 pm

Ok, i have just completed this piston gun, it's a 1" barrel sealing piston with a 1/2" port and a 1/2" pilot, all the parts are pressure rated, I used extra-strength PVC cement, and all the bushings are in all the way. Anyway, my main question was- What would be a safe/reasonable max psi for this? I was thinking between 80 and 120.

Also- what are some ways to make a piston seal better? mine leaks a tiny bit
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Unread postAuthor: frankrede » Wed Jul 02, 2008 10:34 pm

it should be fine at 120psi
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Unread postAuthor: Launch-Tek » Wed Jul 02, 2008 10:39 pm

I try to never go over 120psi with my stuff unless I am trying to blow something up.
You should experiment. Depending on your design you may find a lower pressure that will perform about as good as full pressure and be safer.

Is your piston leaking around the face or the side?
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Unread postAuthor: FishBoy » Wed Jul 02, 2008 10:40 pm

any advice for seal issues???
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Unread postAuthor: Killjoy » Wed Jul 02, 2008 10:40 pm

I second what frank said... Nice build by the way.
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Last edited by Killjoy on Wed Jul 02, 2008 11:19 pm, edited 1 time in total.
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Unread postAuthor: FishBoy » Wed Jul 02, 2008 10:42 pm

*loudly and obnoxiosly clears throat* piston sealing advice????
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Unread postAuthor: brother361 » Wed Jul 02, 2008 10:47 pm

neoprene rubber,? there are alot of kinds of sealing faces bike innertube is realy cheap but not always the best
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Unread postAuthor: MrCrowley » Wed Jul 02, 2008 10:47 pm

It may seem it's leaking from the sealing face when it could be the bolt/washer. If you have a bolt and washer, epoxy it up and if the leaks continue try cleaning your sealing face, sand down the barrel seat (port) to make sure it's even and possibly try a different material.

Nice build btw, reminds me of my V.A.L except with a backward chamber and half the stock. :P
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Unread postAuthor: FishBoy » Wed Jul 02, 2008 10:48 pm

no, i have a neoprene sealing face already, it's just not sealing as well as i'd like it to
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Unread postAuthor: Hubb » Wed Jul 02, 2008 10:52 pm

Is the barrel cut flush? If it is leaking slightly, it could be just off a little. Try adding some soft material, such as cloth, between the seal face and piston.
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Unread postAuthor: Killjoy » Wed Jul 02, 2008 11:20 pm

Yeah I've had even the slightest imperfection on the barrel end result in a so-so seal.
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Unread postAuthor: mega_swordman » Thu Jul 03, 2008 12:51 am

Some grease on the end of the barrel might help a tad.
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Unread postAuthor: starman » Thu Jul 03, 2008 1:42 am

Nice gun...solid design. Next time use the Oatey Cleaner for your PVC cement priming. There is no need to use the purple stuff at all with our spud stuff...for building inspection purposes only. The Cleaner primes your joints just as well.

Good job!!
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Unread postAuthor: FishBoy » Thu Jul 03, 2008 7:34 am

really? so whats primer for then :?:
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Unread postAuthor: starman » Thu Jul 03, 2008 9:02 am

FishBoy wrote:really? so whats primer for then :?:


When buildings are inspected by the authorities, they specify that all PVC plumbing joints be primed before cemented. The only way they can ascertain if they have been primed is if they see the purple or blue stain in and around the joints. They will fail the plumbing job if they don't see the stain.

Here's a look at Oatey primer contents...
Image

and a look at Oatey Cleaner contents (in the yellow can)...
Image

Notice the Oatey Cleaner contains the identical active ingredients. It softens and cleans the joints exactly like the purple stuff and best of all, it's clear...perfect for PVC spud gun building. I use it exclusively.
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