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Sweated Copper Pressures

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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Sweated Copper Pressures

Unread postAuthor: chartreusesnot » Tue Jan 22, 2008 11:24 pm

After seeing the S400, I thought I have to make a Sniper and so I have been looking around at copper rifles, and it seems like they can hold pretty high pressures. How much pressure can a copper pipe hold alone? and is a sweated joint weaker than the pipe itself? I was thinking of using a shock pump with it.
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Unread postAuthor: Mitchza89 » Tue Jan 22, 2008 11:55 pm

I myself have been inspired by Chaos' S400 and the SSS. I also plan to use copper but I'm going to be using compression fittings aswell as brass fittings on the valve.

This is the overall look of the gun I hope to achieve. As much as I love Chaos's gun, I hate copying at all so I've given his design my own touch for what I think will suit me best.

Anyway back to your question, a shock pump will absolutely kill your arms if your planning something at the same scale as his. He has a mightly large air chamber so you might have to use what you have (eg a bike pump, compressor) or upgrade to making a high pressure pump or buying a commercial high pressure 260psi floor pump. I'm not overly sure about soldering, hence why I've gone with comp fittings. If you have the tools, soldering is a top way to go so best of luck with your build.

Hope this is some help to you.
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I plan to get 1/4 copper pipe and run that around so it's flush to gun from the piston valve to the blowgun, this picture does not show it.
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Unread postAuthor: SpudBlaster15 » Wed Jan 23, 2008 12:41 am

I've put 800PSIG in 3/4" Type L copper pipe for ~5ms.

For sustained pressures, 500PSIG would seem to be an acceptable limit.
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Unread postAuthor: Mitchza89 » Wed Jan 23, 2008 12:42 am

Thats quite a lot of pressure. Is that the same with comp fittings though?
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Unread postAuthor: Infernal Maveric » Wed Jan 23, 2008 10:44 am

I have had one compression fitting fail on me, as in, rip the Olive of from around the pipe. This was because the fitting wasn't tightened fully, and because i was using 400PSI.

Soldered/sweated fittings are much more robust in my experience.
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Unread postAuthor: jackssmirkingrevenge » Wed Jan 23, 2008 10:54 am

Have you considered using epoxy :D
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Unread postAuthor: Hotwired » Wed Jan 23, 2008 2:19 pm

Sweated/soldered/capillary fittings will take the same pressure as the pipe when connected properly.
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Unread postAuthor: DYI » Wed Jan 23, 2008 5:13 pm

Using 95/5 tin antimony solder and pressure fittings, copper joints between 1/8" and 1" are rated for 1090 psi. 1" Type M copper tube is rated for 580 psi, and bursts at somewhere well over 3kpsi. I don't know if they will survive the same pressure as the pipe, but, assuming Type M pipe, the joints are rated for more than the pipe itself.
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Unread postAuthor: chartreusesnot » Thu Jan 24, 2008 3:19 am

Thanks guys. This will really help. It seems as if a shockmate, which claims to go to 400 psi should work fine with copper. So shock pumps require lots of effort for a chamber that size? So maybe a high pressure pistol would be a better plan? Or a lower pressure sniper...
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Unread postAuthor: Infernal Maveric » Thu Jan 24, 2008 5:29 am

A high pressure sniper works very well. use a small chamber (3 cubic inces or less) and about 400 PSI.

It takes me about a minuite to get to 400PSI on my BB sniper. It has about 2" of 15mm pipe for the chamber. For larger volumes, expect alot more pumping.
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Unread postAuthor: Hailfire753 » Thu Jan 24, 2008 6:10 am

Hmm, so if I wanted to make a paintball Co2 reg, could I use copper with only screw-in fittings? I can not weld anything, so what metal do you recommend?
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Unread postAuthor: Ragnarok » Thu Jan 24, 2008 6:16 am

chartreusesnot wrote:So maybe a high pressure pistol would be a better plan? Or a lower pressure sniper...

Or a homemade pump, which is the perfect solution to all high pressure/mid volume situations.
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Unread postAuthor: nz_cannons » Thu Jan 24, 2008 4:15 pm

I made this test piece in a metalwork class. It is a few pipes welded/brazed together in various ways. The main body is just normal steel pipe, with a seam. The end bits on the wide pipe are just steel plate which has been butt welded, with a mixture of brass brazing and the others just melted steel/filler rod. One has a brass nut brazed onto the outside with Silfos, which is a faily low temp brazing product for brass and copper ( cant remember exactly which is used cus made it a while back) Up the top there is a copper pipe with a piece of flat copper butt brazed to the end of it, not a cap, just a flat piece of copper. It was dones with silfos, or silver solder, one of them lol.

Anyway, the thing was filled with water and a pump attaced to the brass nut. It was then pumped up to 1800psi, which is pretty high, the flat plates that were butt welded on all bowed out because of the pressure, but the thing held. Only had one tiny pinhole leak. Im not sure it it would be the same as with air, but I dont see why not. If done correctly, brazing/soldering creates a very strong joint. This was all done with a oxy acet torch.
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Unread postAuthor: chartreusesnot » Sat Jan 26, 2008 12:05 am

why won't it let me delete this message??
all I get are the quote and edit options...
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Last edited by chartreusesnot on Sat Jan 26, 2008 12:09 am, edited 2 times in total.
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Unread postAuthor: chartreusesnot » Sat Jan 26, 2008 12:07 am

Ragnarok wrote:
chartreusesnot wrote:So maybe a high pressure pistol would be a better plan? Or a lower pressure sniper...

Or a homemade pump, which is the perfect solution to all high pressure/mid volume situations.

and how might I do this safely?
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http://www.youtube.com/watch?v=wLNjMSGxp00
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