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Big Enough Air Chamber

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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Big Enough Air Chamber

Unread postAuthor: sfmm19 » Wed Jan 14, 2009 7:04 pm

Hi, I'm building cannon using 1" PVC, a .5" barrell and PCGUY's breech loading mechanism. I plan on using a modded sprinkler valve.

If I use the 1" PVC and make a moderate sized stock with it, will it hold enough air for a good number of shots?

If So about how many shots?

And if not what do you suggest as a way to hold more air
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Unread postAuthor: sputnick » Wed Jan 14, 2009 7:43 pm

Spudguns aren't designed for multiple shots, you would only get 1 shot.
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Unread postAuthor: Cosmic Muffin » Wed Jan 14, 2009 9:15 pm

it will hold one shot like sputnik said.
if you dont mod the valve and hook up a momentary switch to the solenoid then you could get about 2 good shots.
but moding a valve will increase the guns overall performance. so go with that if you want something worth shooting :P
more air-just have a secondary tank, regulated CO2 or a portable compressor
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Unread postAuthor: inonickname » Wed Jan 14, 2009 9:35 pm

With a modified sprinkler valve you will only get 1 shot. The best way for multi shot is a hammer valve or blow forward (JSR's design) breech or a blowback breech.
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Unread postAuthor: suburban spudgunner » Thu Jan 15, 2009 4:53 am

For multiple shots, you'd need a different setup, like what is mentioned above.
The efficiency of each shot would also depend on the length of the barrel you want to use; if it's too short, very little pressure will build up behind the projectile; if it's too long the projectile will slow down upon exit.
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Unread postAuthor: psycix » Thu Jan 15, 2009 9:35 am

People have been using sprinklers to get multiple shots out of large chambers though.
Maybe using a hammer valve to pilot it would help it.

Though getting multiple shots from the same chamber is kinda lame as the first shot is powerful and every shot after that becomes weaker.
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Unread postAuthor: Hubb » Thu Jan 15, 2009 9:45 am

Try to aim for about a 1:1 ratio (chamber volume to barrel volume). For your application (if I understand correctly, a rifle type), this would be ideal, but only yield one good shot per chamber fill.

You could hook up a constant air source to your camber, which would fill the chamber after each shot and give the appearance of multiple shots from the chamber.
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Unread postAuthor: sfmm19 » Thu Jan 15, 2009 4:43 pm

Thanks for the quick replies, im a noob at this.

If i used a small air compressor or attach a pump that would give me the ability to shoot multiple shots?
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Unread postAuthor: JDP12 » Thu Jan 15, 2009 4:46 pm

well...technically no it would't give your more shots, because the chamber is still having to fill. If your compressor is very large, there wouldn't be much of a delay.

There would be a pump delay though because you'd have to pump it
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Unread postAuthor: Hubb » Thu Jan 15, 2009 5:07 pm

If you connected the compressor to remain on the gun, it would give the appearance of multiple shots.

What I mean is this: You're building a rifle using a 1" chamber and a 1/2" barrel, so chances are the chamber is going to "smaller than average". Once the round is fired, the chamber will automatically refill. By the time you breech another round, the chamber should be filled and another shot can follow.
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Unread postAuthor: sfmm19 » Thu Jan 15, 2009 6:32 pm

Ive been surfing the web and I am having trouble finding a small enough compressor to mount on a gun.

Do they make them?
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Unread postAuthor: Hubb » Thu Jan 15, 2009 6:35 pm

Your best bet (for portability) would be to get a compressed air or CO2 bottle and hook it up to a regulator.
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Unread postAuthor: sfmm19 » Thu Jan 15, 2009 7:35 pm

ok I'm gunna try it, thanks for your help
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Unread postAuthor: tghhs » Mon Jan 19, 2009 4:51 am

sputnick wrote:Spudguns aren't designed for multiple shots, you would only get 1 shot.


yeah thats what i thought, till i made my coaxial, but i found that i can get a couple of shots if i pump it to 80psi (not much but to hard to pump, lol).
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Unread postAuthor: psycix » Mon Jan 19, 2009 5:39 am

You COULD do it with a 12 volt compressor. But they dont last very long.
I mean those tiny things to have in your car as emergency pump to fill your tires. They also pump very slow.
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