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Posted: Thu Jul 07, 2011 3:03 am
by gsw2
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.
Posted: Thu Jul 07, 2011 5:08 am
by Crna Legija
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.
Posted: Thu Jul 07, 2011 5:30 am
by gsw2
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?!
Posted: Thu Jul 07, 2011 5:42 am
by Crna Legija
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.
Posted: Thu Jul 07, 2011 6:13 am
by gsw2
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?
Posted: Thu Jul 07, 2011 8:22 am
by Crna Legija
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
Posted: Thu Jul 07, 2011 9:14 pm
by gsw2
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.
Posted: Thu Jul 07, 2011 9:25 pm
by saefroch
Homemade piston valve is usually better. As Crna said before... QEVs typically have an undersized port.
Posted: Fri Jul 08, 2011 12:57 am
by gsw2
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.
Posted: Fri Jul 08, 2011 1:14 pm
by Gun Freak
What kind of blowgun is it? They always have 1/4" and 1/8" threads.
Posted: Fri Jul 08, 2011 9:09 pm
by gsw2
The blowgun problems gone and my cannon is complete
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..
Posted: Fri Jul 08, 2011 9:11 pm
by jackssmirkingrevenge
Where are you filling from?
Pics/diagrams?
Posted: Fri Jul 08, 2011 9:34 pm
by gsw2
Intake point is where I'm filling from (obviously)[/img]
Posted: Fri Jul 08, 2011 10:03 pm
by saefroch
I think JSR is looking more for a picture of the setup so he can verify that you have the QEV connected correctly...
Posted: Fri Jul 08, 2011 10:21 pm
by gsw2
The PVC is temporary as I wanted to find out how a QEV + Blowgun setup worked without spending to much money.