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Closing slam on seal

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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Closing slam on seal

Unread postAuthor: tghhs » Mon Sep 28, 2009 6:31 pm

Hey people,

So i just finished my coaxial (i'll post it when it's working) it's 1/4inch barrel and 40mm pn 12 chamber.

my problem is that when i pressurize, the piston slams extremely hard against the barrel, which is pushing it through the front cap. This is caused because when it fires the piston moves back into the slightly smaller diameter of the pipe in the end cap, creating a seal and jammed. So in order for me to close the piston i need the same amount of pressure that my last shot had.

I normally use it at 100 psi so; 2*pi*.728 (area of piston face) = 4.571 inch squared.
4.571*100psi = 457.1 pounds of force (not calculating weight of piston)

this force is just stripping the epoxy from the sanded barrel to the end cap, What can i use/make that would solve this?

Edit: spell check :oops: , and i'm really sorry about the many posts! it wouldn't load so i refreshed.
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Last edited by tghhs on Mon Sep 28, 2009 6:50 pm, edited 1 time in total.
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Unread postAuthor: Mr.Sandman » Mon Sep 28, 2009 6:37 pm

Dude be careful when hitting submit. You just posted 4 topics.
Also dude spell check? Come on it looks like you put in no effort to even give a damn about spell check. How is your barrel connected to the chamber?
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Yeah, it's that important.
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Unread postAuthor: tghhs » Mon Sep 28, 2009 6:51 pm

The barrel is pushed through a hole in the end cap then epoxyed in
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Unread postAuthor: Mr.Sandman » Mon Sep 28, 2009 7:04 pm

Why not just make an epoxy end cap? just cut off a section of the chamber and barrel then make an epoxy endcap. Its very simple as your barrel wont survive for long like this.
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Unread postAuthor: tghhs » Tue Sep 29, 2009 2:55 am

Well i'm making a Solid teflon plug, i'll wrap it in telfon tape to plug it in and screw it in around the sides. And for looks i'll put a PVC cap over the top.
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Unread postAuthor: Crna Legija » Tue Sep 29, 2009 3:09 am

I just made my coaxial to. I cut groves into the barrel only .5 mm deep and welded a washer on the barrel to stop the epoxy leaking around. Try that or if its pvc you can use pvc primer/cement a bigger pipe over the top if its copper use solder.
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Unread postAuthor: tghhs » Tue Sep 29, 2009 7:18 am

Yeah good thinking! It's a copper barrel so i'll put a ring of solder just before the endcap? I've already made the teflon plug so i'll use both :)
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Unread postAuthor: Crna Legija » Tue Sep 29, 2009 9:45 am

I was thinking solder a bigger pipe over the the barrel like 1cm from the end and fill with epoxy
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Unread postAuthor: tghhs » Tue Sep 29, 2009 8:04 pm

Argh i see what u mean, yeh i reckon that'd hold it :)
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