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Semi-auto piston valve gun

Posted: Tue Aug 22, 2006 10:42 pm
by alkalineall
I've been browsing this forum for a couple weeks now, and have wanted to build a pneumatic cannon for years. I knew what type of valve I needed, but never knew where to find one. Well, I'm most of the way finished with my project and will have some pics real soon but Ive noticed an interesting phenomenon in firing. I built my cannon with chamber to spare to make sure that pressure was mantained until projectile left the barrel and when I fire with just momentary trigger pull on the blowgun I can get two good shots out of one fill. This is with first shot at about 60 psi and the second at about 30 psi. The second is a bit weaker , but both crumple up coffee cans with just balls of tape. This gives me some ideas , what does everybody think? . If this topic has been discussed at length I apologize although I ve already tried to search it with no luck.

Posted: Tue Aug 22, 2006 10:55 pm
by saladtossser
i can get 3 shots out of 100 psi, my chamber is very very small, i dont think there is a practical way to maintain the power because once air is gone, its gone... or else u basically have energy out of nowhere, even with a volume reducing piston... i thing there is a garden hose fitting that is a three way ball valve, try making a double barreled shotgun, or a small magazine that only fits one ammo (one in barrel, one in mag)

sgort (was it?) also invented a system that allowed 3 shots... i forgot

Posted: Tue Aug 22, 2006 10:59 pm
by Atlantis
You could try my idea to bring the pressure back up without adding air.

http://www.spudfiles.com/forums/viewtopic.php?t=3050&

Posted: Tue Aug 22, 2006 11:19 pm
by Brian the brain
Try one of your ideas yourself for a change!

Posted: Wed Aug 23, 2006 1:27 am
by alkalineall
Oh Ok I get the idea. So the volume is getting smaller and smaller with succesive shots right? I'm almost done with my project, I was working on it just now (and every night for the last week and a half), but I'm stuck on what to use for a pistol grip mount for my blowgun. Any recommendations? The setup is like a shoulder fired rocket launcher with a shoulder rest and side rails that I riveted together (aluminum). The pistol grip containing blowgun goes in front of shoulder rest. I almost bought one of those cheap pistol looking blowguns but I didn't like the looks and consruction of it. I'm almost thinking that I could sandwich the blowgun between two halves of something but I'm stuck on what. I should go look at cheap toy guns at Wal-Mart.

Posted: Wed Aug 23, 2006 1:22 pm
by saladtossser
you could use a push button valve instead of a blowgun for a pilot, with it, you can easily attach it to a peice of pipe for a handle, or a toy gun

Posted: Thu Aug 24, 2006 7:44 pm
by alkalineall
Huh, I don't recall ever seeing a push button valve, except for the valve thats underneath a blowgun's lever. Can you give me an example of the type that you mean? Thanks a lot.

Posted: Fri Aug 25, 2006 5:59 am
by L.J.R
I have a small push button valve that i stole from the side of a blowgun but i have never been able to find them sold separately so I am gathering that they may be rare.

Posted: Fri Aug 25, 2006 2:58 pm
by Bluetooth
Search mcmaster,

Posted: Fri Aug 25, 2006 3:00 pm
by saladtossser
search for a local pneumatic part supplier, if you find the right one, they will have everything