check valve

[Mini Khan]

is it posible to use a check valve for a primary valve? Exuse the bad spelling.

[carlbelcher]

No you can’t use a check valve as a “primary valve”. Check valves are designed to let air though only one way and there is no way the control the flow in that one direction, so you can't use them as a \"primary valve\" assuming that you’re referring to the main air valve on a pneumatic cannon. You should check out the spud wiki it has a great section on valves.

[CS]

Normally no, but Ive always wanted to try a method of using them. Simply connected a bolt via a coupling nut on the threaded piston in the check. It would work like a mortar. When projectile hit bolt it would shoot projectile like a mortar.

[carlbelcher]

Hey that's about the best idea I've heard all day. The only problem is that the instant the projectile left the bolt the valve would close.

[Shrimphead]

I could see it working on a small cannon.

[frogy]

Hey that's about the best idea I've heard all day. The only problem is that the instant the projectile left the bolt the valve would close.

I'm not sure that's true... Once the valve is open the piston's equalization area would be drained already so it would let all the air out, I'm not sure if you understand this because I'm tired and I forgot what you call the equalization area

[carlbelcher]

If you look at the way check valves work the flow of water in one direction would force the valve open, but water flowing the other way would slam the valve shut. The same applies for the cannon, except the water that would normally flow to push the vales open is a projectile hitting the check plate, ball, or door. So when the projectile hits the check plate, ball, or door it opens it monetarily just enough for the air to start flowing past the check plate, ball, or door as the air does this it forces the check plate, ball, or door closed just like water would. And that is if the projectile has enough force and or mass to push the check plate, ball, or door open against the air pressure in the chamber anyway. I included some pics of different PVC check valve for examples.

[noname]

If you had a large, fast closing check valve and a big chamber you could pretty much have a mortar.Just keep dropping stuff down and it would lose air a little bit at a time unless you ran a compressor with it. Hey that's a good idea.

[carlbelcher]

I still think the biggest problem is forcing open the check valve against the pressure. Just think, say the check valve only has a 1 inch check plate or door and you have a chamber with 90psi in it.


pi x .5 inches = 1.57 square inches x 90psi = 141.3 pounds of force


That means to force the check vale open it would take 141 POUNDS OF FORCE

[Mini Khan]

thanks for ruining my dream carlbelcher, but what if u had an exuast valve at the back of the chamber?

[carlbelcher]

Sorry, but I don't think that wouldn't work ether because you would have exhaust all the air from the chamber to open the check valve.

[Mini Khan]

well than how bout if i put it at soo much psi it blows the valve, that would work!!!

[carlbelcher]

I guess that's one way to do it! LOL!

[noname]

And then your wasting a buttload of cash. At the local hardware store near me, the smallest check valves they have are 1/2", and just those are $7.50! I could use them in diaphram guns though. Just drill a few holes and extend the valve out the the exhaust.