SpudFiles

Fellow Spud-launchers,
I'm making my first pneumatic semi-auto potato cannon and I need to know more about these solenoid thingys. Any links would be greatly appreciated.
1.) How much air flow can they handle? For instance, my plans call for a 4" diameter chamber 12" long at 50-75 psi into a 1.5 diameter barrel ~9 feet long.
2.) How do I tweak a solenoid to get it to work?
3.) Is it best to go with a sprinkler solenoid or an actual air valve (I saw them on ebay for $15) ?

Any info and/or diagrams would be great, thanks!

Sprinkler soleniod valves can usaully handle 125psi max. Some are 2" and other are 1" input-outputs, so flow depends on size. To get best preformaence, get ones you can pnuematically mod, so not only will the valve open faster it will give you more of the cool trigger function. I am not sure what would be best for you on the 4" chamber, obviosly bigger valve the better, just wait for a more experienced spudder to answer.

i am trying my solenoid valve now but when i pump up the gun, the air just comes out the barrel. Any ideas would be greatly appreciated.

look for the little arrows on the side of the valve.screw it on so they point to the barrel,and away from the chamber

Would this work????
search "sprinkler solenoid"
<a href="http://www.homedepot.com/prel80HDUS/EN_ ... >Sprinkler Valve</a>

EDITED BY PIMPMANN22, BECAUSE LINK F*CKED THE FORMAT OF THE PAGE

i did that and used teflon tape and screwed it on and everything but it still doesn't close off the chamber. believe me, i did everything right.

a solenoid valve probably isnt your best bet for a semi auto launcher, i'd go with a piston or diaphragm valve with a fast opening and resetting time, and use a 3 way valve so you can dump the air, and at the same time cut off the air input (i'd use co2 or air compressor)

Where could I get a piston/diaphram valve?

You have to make them. The only commercially made ones that are useful to us are sprinkler valves, and quick exhaust valves (qev). Just go to the wiki and look up diaphragm and piston and read about them until you get how they work.

I will assume you are asking about modding the valve to make it open faster. To do this, you drill a whole in the top and tap it with a 1/4 NPT pipe tap. It must be a tap for pipe threads or it won't work right for this. Then you add a blow gun to this hole so it will vent the air above the diaphram and allow it to open due to the pressure differential.

One reason it may not be closing is you aren't getting the air in fast enough. I tried pumping my pneumatic up with a hand pump and it leaked. That's just the way sprinkler valve are I guess.

But, like its been said it would be better to go with a piston valve. More flow, cheaper, and will just work better for your application.

Sprinkler valves work fine in semi-autos in my experience spudshot.

Same here.

I can't believe I said what I said up there /\. Had to be one of my first posts.