SpudFiles

Hello spudfiles i just have a quick question about a valve that I bought. My understanding of qevs is that they have a small spring inside them to push the piston back into place after the air reservoir has been released. so it came as a surprise when i could not find a spring in the valve and could push the piston back with my finger without it returning back to it's original place. i was wondering if this is okay or if i should see about getting another valve. The valve i bought is a simple 3 way qev that i have seen on several other projects.

-Madmarcs

While I'm sure QEVs with springs exist, I think they more typically work like this:
In any case, you should just test it. If it works? Great! If not... less great.

Most QEVs don't have springs inside them, You only need one if you plan on semi auto, However there are much more efficient ways of accomplishing that.

Mine has semi auto and no spring...

thanks for the info and the speedy replies. The cannon i am building will be bolt action and will dump the reservoir for each shot bet will be hooked up to a co2 regulator and bottle so refilling the reservoir will be a snap.

PaperNinja wrote:Mine has semi auto and no spring...

"However there are much more efficient ways of accomplishing that."

More efficient semi auto than QEV with a spring, without a spring or both?

If you're pressurising the system from the pilot side, there is no need for a spring. If on the other hand you're filling from the chamber side, you need to add a spring and make some sort of equalisation hole.