My first gun using QEV 20bar

[Brian the brain]

Can you explain the hold in the cylinder a little more, maybe add a picture or something. I just got the exact valve in the mail today and I'm interested in making the modification. Thanks

I don't understand the question..

[slugguy]

I misspelled the word "hole." I spelled "hold" by accident. On 8-8-12 at 15:52 you said to punch or drill a small hole in the piston of the qev. I didn't understand what you meant, where you meant, or what it is for. I'm just starting out with a qev myself and would like to make any modification that would help the gun. Thanks for your help.

[Brian the brain]

Don't puncture the middle part where it seals the out-port and don't get to close to the edge of the piston as it might tear by the repeated stress of firing.

It's that simple.
Air coming from the reservoir will repressurise the pilot area as soon as the pilotvalve is closed and the piston will be pushed back against the port and seal again.

Now..if you want to pressurise the gun ( pump, compressor,whatever)
directly into the reservoir( wich can't be done with an unmodded qev), you need to put a weak spring behind the piston or it will get blown open by the incoming air.

So a spring will enable you to fill "chamberside".
This will help reduce the numer of fittings on the pilotside.
less bulk and smaller pilotvolume wich helps performance.

The hole is what makes the valve able to "repeat".
If that hole becomes too large it will hurt performace as the air just rushes out the pilot through that hole.
Keep it small!!
about 2mm should work..

[slugguy]

Cool. Thanks so much for taking the time to go through all that.

[Brian the brain]

It you then use JUST a safety pop-off valve as a pilotvalve ( nothing more!!) and fill the chamber at high pressure and high flow and you get this:
( and build the blowback system to feed ammo offcourse)

Notice all I have to do is squeeze a blowgun to feed pressure into the chamber...and off she goes..

[GustavssonB]

BTW: with a well made hammervalve all your components should be able to handle 20 to 25 bar.

The gun has now been tested with 20 bars pressure:D and its still holding nicely:)

[truemanator]

How Did you make that adaptor for the extinguisher, and also, how do you fill it up, i cant see a filling valve anywhere?

[GustavssonB]

I welded the extinguisher to make it a different thread sice. The air is pumped on the pilot side of the qev, were the quick connect is:)

[truemanator]

y exactly did u repost that??

[GustavssonB]

Haha wtf, wasn't going to repost that... I tried to change the title, not sure on why that happned:/

[archie370]

This is pretty cool what kind of welder did you use for the fire extinguisher ... ?

[GustavssonB]

This is pretty cool what kind of welder did you use for the fire extinguisher ... ?

Thanks, i used i MiG welder for the extinguisher:)

[archie370]

Oh yeah you must be a pretty good welder for it to be safe ... i thought it would be a special welder for welding stainless but obviously its not stainless haha