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1st Pneumatic Rifle

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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Unread postAuthor: jackssmirkingrevenge » Sat Jul 09, 2011 12:11 am

QEV connected the right way round but your pilot volume is the size of a shoe bomber's stride, you're getting pressure into it fast enough and even if you do it will be horribly inefficient.

You should be aiming for something like this:
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Unread postAuthor: gsw2 » Sat Jul 09, 2011 12:32 am

Haha! Good way to put it. Ok thanks I'll make it as small as possible.
and thanks for the diagram.

EDIT: I've fixed the pilot chamber area, I couldn't make it any smaller, and sure enough it works great. Although I'm getting HORRIBLE performance out of it. i.e shooting a marble goes around 4 meters at 30psi. I am going to be changing the design to copper but until I can get the money I'm stuck with this. Can anyone spot a flaw or an area where I can increase output. I'm thinking of changing the barrel to a smaller size, at the moment it is 15mm.
Thanks

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Unread postAuthor: Mr.Tallahassee » Thu Jul 14, 2011 3:01 am

Your pilot needs to be MUCH smaller to be efficient enough to fire with any real power. The faster you can vent the pilot and the less volume you are venting, the more efficient and powerful the gun is. You could probably switch the blow gun and schrader valve and put a ball valve directly off of the tee going to the stock strictly for filling. That should cut your pilot to a third of its original volume.
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Unread postAuthor: jackssmirkingrevenge » Thu Jul 14, 2011 3:09 am

gsw2 wrote:I've fixed the pilot chamber area, I couldn't make it any smaller, and sure enough it works great.


Your pilot volume is still far too large, probably larger than your actual chamber! Can't you get a small metal tee? One end in the QEV exhaust, Schrader on the opposite end and blowgun coming down the bottom.

Alternatively, connect the blowgun directly to the QEV, and to the blowgun outlet connect a schrafer valve with the inner core removed.

When filling you have to keep the blowgun open which is a bit inconvenient but power will be much, much, much better.
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