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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: gsw2 » Thu Jul 07, 2011 3:03 am

Thanks for all your help. I bought everything today except the QEV which I'm getting tomorrow, will put it all together in a day or so.
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Unread postAuthor: Crna Legija » Thu Jul 07, 2011 5:08 am

cannon monkey wrote:Sorry to thread jack but. What size home made piston valve will give the same performance power as a 3/4 qev??? Thanks and sorry for small thread jack


I say a well built 1/2'' piston valve would out preform a 3/4'' qev.
in my experience with QEVs the barrel port is way smaller then it could be.
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Unread postAuthor: gsw2 » Thu Jul 07, 2011 5:30 am

I must be a real bugger... but...
I was just thinking, when the pressure equalizes in the chamber and pilot chamber, will the gun spontaneously fire?? Because the piston inside the QEV wont be pressured against the barrel anymore?!
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Unread postAuthor: Crna Legija » Thu Jul 07, 2011 5:42 am

gsw2 wrote:I must be a real bugger... but...
I was just thinking, when the pressure equalizes in the chamber and pilot chamber, will the gun spontaneously fire?? Because the piston inside the QEV wont be pressured against the barrel anymore?!


nope, there's more surface area on the back of the piston then the front.
that's how I figure it works at lest. :lol:
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Unread postAuthor: gsw2 » Thu Jul 07, 2011 6:13 am

Awesome! Thanks a lot Crna. Your a gold mine of information!
Can't wait to start building this thing. :)
Does it pressurize immediately or does the leaking past the QEV take a while?
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Unread postAuthor: Crna Legija » Thu Jul 07, 2011 8:22 am

gsw2 wrote:Awesome! Thanks a lot Crna. Your a gold mine of information!


thanks!

gsw2 wrote:Can't wait to start building this thing. :)
Does it pressurize immediately or does the leaking past the QEV take a while?


not with qevs, their piston is like a one way valve so flow in very good but with tight fitting home made piston that are solid you can get a delay. i had the problem with my one gets annoying if you use pre-pressurized air but filling with a fridge compressor its fine as the flow is pretty sh!t
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Unread postAuthor: gsw2 » Thu Jul 07, 2011 9:14 pm

What is your preference a QEV or a home made piston? They both seem to be good, except with a home made piston you have more control.
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Unread postAuthor: saefroch » Thu Jul 07, 2011 9:25 pm

Homemade piston valve is usually better. As Crna said before... QEVs typically have an undersized port.
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Unread postAuthor: gsw2 » Fri Jul 08, 2011 12:57 am

Ok I'll remember that for the next build. Making a piston just sounds hard though... Finally got my QEV, putting it all together now. The blowgun is going to be a bit tricky because the thread is so small no one stocks adapters for it! Still thinking about it.
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Unread postAuthor: Gun Freak » Fri Jul 08, 2011 1:14 pm

What kind of blowgun is it? They always have 1/4" and 1/8" threads.
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Unread postAuthor: gsw2 » Fri Jul 08, 2011 9:09 pm

The blowgun problems gone and my cannon is complete :D
But the QEV is letting air down the barrel? and because of this it doesn't pump up. What is the problem? It really blows to have finished a build and find out something is wrong..
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Unread postAuthor: jackssmirkingrevenge » Fri Jul 08, 2011 9:11 pm

Where are you filling from?

Pics/diagrams?
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Unread postAuthor: gsw2 » Fri Jul 08, 2011 9:34 pm

Image
Intake point is where I'm filling from (obviously)[/img]
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Unread postAuthor: saefroch » Fri Jul 08, 2011 10:03 pm

I think JSR is looking more for a picture of the setup so he can verify that you have the QEV connected correctly...
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Unread postAuthor: gsw2 » Fri Jul 08, 2011 10:21 pm

Image
Image

The PVC is temporary as I wanted to find out how a QEV + Blowgun setup worked without spending to much money.
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