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How small could I go?

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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How small could I go?

Unread postAuthor: )DEMON( » Thu Jul 05, 2007 12:59 pm

Question

How small do you think could I make the air chamber of a pneumatic cannon if it has a 1'' modified sprinkler valve with a 2'' barrel roughly 1-1/2' long and still achieve decent velocities of around the 250fps margin while running at around 50-70psi? :?

I have been wanting to build a launcher for paintball use for a long time but have always come up with these criteria that could prove problematic for the design:

1) Must be compact (as small as possible)
2) Must be able to load quickly (breach design done, perfect seal)
3) Must be able to recharge quickly (pump connected onto chamber)*
4) Must achieve decent velocity of around 250fps (for distance)
5) Must be low pressure
6) Can't spend heaps of cash
7) Must be as simple as possible (for best reliability)

*possible mini compressor fitted onto chamber

Trying to combine speed, power and reliability is not easy :shock:
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Unread postAuthor: noname » Thu Jul 05, 2007 1:06 pm

A 1 foot long 3" chamber could probably do it, and isn't too huge.
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Unread postAuthor: Fnord » Thu Jul 05, 2007 1:11 pm

Well, from my ggdt results, you're not going to get much better than 230 fps with an 18ing barrel at 70 psi.
Also what is your projectile weight? I just used 50 grams.
Are you going to be using co2? it would be a lot more stealthy than a compressor.
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Unread postAuthor: )DEMON( » Thu Jul 05, 2007 2:09 pm

That should be ok. I will fiddle around a little with the ggdt now that I have the values for the valve and such. Never figured those out before.

You left inner diameter of reservoir as 0 in your ggdt.

um, a quick question, what should I put as dead volume for the valve?
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Unread postAuthor: WOW!! » Thu Jul 05, 2007 2:18 pm

A coxial? 2'' chamber and 1'' barrel and then have your 2'' pipe screw on to the front. Use a 1 1/4'' end cap for the piston. It should work but you might lose a little pressure from the space of the 1'' barrel to the 2''. Ill draw a picture of it.

What are you planing to shoot?


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Unread postAuthor: )DEMON( » Thu Jul 05, 2007 2:28 pm

No, too much dead space.

I am planning to shoot multiple paintball rounds, no need for nerf rockets cause we don't have tanks.

Oh, inner diameter is for a coaxial :P I didn't know that. Sorry. This cannon is going to be an over and under.
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Unread postAuthor: WOW!! » Thu Jul 05, 2007 2:47 pm

I got a really good idea, but I am still working on it. You take 2-3 3/4''CPVC and put together and slip it inside of some bugger PVC and then expoxy them in there, and then atach it to the valve like a regular barrel but now you can load 5-6 paintballs each "mini barrel" so you get a good amount of paint.

Ill try and make a drawing of it.
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Unread postAuthor: )DEMON( » Thu Jul 05, 2007 3:09 pm

Yeah a drawing would help.

You guys are going to like my breech design :D
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