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QEV size/barrel diameter relationship

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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QEV size/barrel diameter relationship

Unread postAuthor: Ianbuckwell » Wed Jul 30, 2014 12:06 pm

Hi, For my gun I am using a 12mm (just under 0.5") inside diameter along with a Parker 3/4" QEV. I have no complaints about the performance ( it is stunning imo). My only complaint is it has a large body diameter which limits my options to making it look like a gun.

Would a decent 1/2" qev limit/restrict the current performance or is it still suitable? Otherwise I will have a smaller diameter barrel and make a completely new gun, I may do this anyway.

Just wanted anyone's thoughts of what QEV size suits what barrel diameter? Is barrel length a factor?
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Re: QEV size/barrel diameter relationship

Unread postAuthor: jrrdw » Wed Jul 30, 2014 2:39 pm

Matched porting would be fine.
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Re: QEV size/barrel diameter relationship

Unread postAuthor: noname » Thu Jul 31, 2014 2:39 pm

A sprinkler valve can launch a golf ball pretty well; that's about a 1:2 ratio between the valve and barrel sizes. As long as the valve is decent, half the barrel size seems to work pretty well for casually chucking stuff.
If you're aiming for high velocities of course you would want a bigger and better valve, but otherwise it's not that big of a deal.
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Re: QEV size/barrel diameter relationship

Unread postAuthor: jackssmirkingrevenge » Wed Aug 06, 2014 9:23 am

Bigger is always better if power is what you're after - as always, GGDT is a good way to have an idea of how a flow restriction will affect performance with all other things being equal. Model your launcher and play with the "valve seat diameter" parameter.
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