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Posted: Sun Aug 20, 2006 12:53 pm
by joannaardway
New WBl idea. Instead of using a sprinkler valve, you might want to consider use of a QEV:

http://www.airlines-pneumatics.co.uk/we ... de=S070139

A 3/4" QEV has more flow than a 1" Sprinkler valve, opens even faster, and based on UK costs, costs about the same as a 1" sprinkler valve.

It requires no electric parts and is completely mechanical in it's operation.

Posted: Sun Aug 20, 2006 1:41 pm
by Silence
Interesting. How would you compare QEV (perhaps a Quick ____ Valve, I really don't know) to a modified solenoid sprinkler valve? I don't know much about valves used in pneumatic applications, so how does this one work? Sounds interesting, at the very least.

Posted: Sun Aug 20, 2006 2:31 pm
by joannaardway
Quick Exhaust Valve.

A QEV should out do a modified sprinkler valve, both on flow co-efficent (about 25% higher) and opening time (50%-100% better). The typical rating on one of these is about 150 psi, against the 125 psi of a sprinkler valve.

As a very rough explanation, a QEV is basically a piston valve operated by venting the air space behind a "special" piston.

It's normally used to trigger pneumatic cylinders, for better actuation times.

I'm linking to some topics on another forum about QEV triggered launchers.

http://www.uksgc.co.uk/forums/index.php?showtopic=273

http://www.uksgc.co.uk/forums/index.php?showtopic=191

http://www.uksgc.co.uk/forums/index.php?showtopic=306

These are all low bore launchers (the first two are 20mm launchers, and the last started as a 13mm bore, but was changed to 20mm).

However, there should be no issues with using a valve like this on a 2" or 3" bore wbl.

You may remember me mentioning that my twin was building a new launcher that would chuck 20mm steel ball-bearings a 1/4 mile.

That's also going to be a low bore launcher, but using two of these valves for incredible performance levels (including firing frozen grapes at 2/3rds of the speed of sound).

However, with a single valve, a heavier projectile and a higher bore, muzzle velocities will not be that nasty.

Posted: Tue Aug 22, 2006 6:56 pm
by joannaardway
Quoting some figures off spudtech for a 3/4" Pneumatically modded sprinkler valve Vs a 1/2" QEV:

With a 40 CI chamber, 5' CPVC barrel, 100 PSI, shotgun slugs for projectiles (425 grains) the average muzzle velocities were as follows:

3/4" Sprinkler valve: 388.3 fps
1/2" QEV: 517.3 fps

So the QEV results in 33% more performance (129 fps more).

With regards to a 1" Sprinkler vs. a 3/4" QEV, I have no figures, but the greater efficency of the QEV's should allow use of lesser pressures for the same effect (meaning less effort pumping up the launcher)