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QEV vs Spring Ball Valve Performance Thread

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 vs Spring Ball Valve Performance Thread

Unread postAuthor: boyntonstu » Sat May 15, 2010 10:34 am

http://www.airgununiverse.net/community ... 154.0.html

"All right, I got the ball valve pilot chronographed at 400 psi - 538.8 fps, a 22.8 fps increase over the ball valve. That translates to 2 fpe increase in energy. This again is using the exact same chamber, barrel, ammo, and patch used with my .40 ball valve airgun. Whether or not this is a true improvement is the real question. The qev has a decent amount of internal volume, almost like a coaxial piston valve has. This volume would be easily roughly equal to another inch or more of the copper chamber. I'm kinda disappointed in the results, after spending $50, I hoped the qev would blow the ball valve out of the water. Sad At the same time, it is interesting to see actual experimentation debunk conventional wisdom. I guess I'll have to do a video on this experiment when I have some down time.

At any rate, these qev valves are amazing. They will discharge even with one stroke of a shock pump. You are probably looking at 1 or 2 psi over atmospheric pressure. The pistons they use are simple and very effective. The only real downfall to their design is the 1.5 or so inches of dead volume. This could be eliminated by using a barrel that slides into the valve, in effect making a true barrel sealing valve."
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Re: QEV vs Spring Ball Valve Performance Thread

Unread postAuthor: velocity3x » Sat May 15, 2010 10:56 am

boyntonstu wrote: The only real downfall to their design is the 1.5 or so inches of dead volume.

Actually, QEV's have more limitations that just one. They are a great valve when used within their designed limits. In a high pressure / high volume flow application, a ball valve is hard to beat.
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Unread postAuthor: Technician1002 » Sat May 15, 2010 11:16 am

The flow coefficient is another very important valve parameter besides speed. Trading one for the other may provide limited performance gains. Improving both at the same time makes big changes.

A QEV is faster. A ball valve has better flow. Which is better?

It depends on your pressure, barrel, and projectile, and to some extent, your skill ( how fast can you turn the valve )
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