Valve suggestions

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
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danielrowell
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Mon Sep 12, 2011 3:14 pm

Hey guys, this will be my first post.

I am a big fan of powerful pneumatic cannons. I currently plan on building a relatively simple, but very powerful pneumatic cannon. It will have an 8 foot, 1 1/2" PVC barrel (pressure-rated pipe, of course), with an 8 foot, 3" PVC air tank underneath the barrel. (I wish I could make it 10 feet long, but I have limited storage at my house.) I plan to launch large projectiles out of it, weighing up to a pound. As such, I need a valve that can handle the release of large ammounts of air, but I don't want to bother with building or buying a piston valve.

My question is, can anybody reccommend a ball or butterfly valve to me that can handle such a job? Also, does anybody have any suggestions on modifying a ball or butterfly valve (ex. making a ball valve spring-loaded)? Thanks for the input.
jsefcik
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Mon Sep 12, 2011 3:23 pm

My opinion, would be trying using metal, can handle much higher pressures

valve wise. even thought you may not want to still lean towards a piston valve, if you use pvc, piston, you might end up breaking the housing
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Alster370
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Mon Sep 12, 2011 3:24 pm

Any ball valve should be fine, they all have pretty much the same flow. What pressures will you be working with?
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danielrowell
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Mon Sep 12, 2011 3:34 pm

I'll be using up to 130 psi. That's as far up as my compressor can go and still below the working pressure of the PVC.

P.S. I should have done more research before I posted. Butterfly valves are too expensive for me. :( That said, does anybody have any examples of modifying a ball valve to make it open faster, ex. spring-loading it etc. Or, would just using a lubed ball valve be fine? Thanks.
jazzman56
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Mon Sep 12, 2011 3:53 pm

From my experience, you cannot spring load a PVC ball valve as there way to stiff. SO just oil the crap out of it, and flick your wrist to open it as fast as you can.
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mattyzip77
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Mon Sep 12, 2011 3:55 pm

You can get a qev valve for 20 or 30 dollars and in my opinion they are just as good as a piston valve. And so you know, 8 feet of 3 inch for a chamber is way overkill. you could get away with probably less than half of that without losing performance. good luck!!
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nathanhd123
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Mon Sep 12, 2011 4:15 pm

I would definitely use a QEV. Much better performance and are not hard to find.

Also I would also recommend using metal, just to be on the safe side. 8)
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danielrowell
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Mon Sep 12, 2011 7:49 pm

Thanks a lot guys! I'll definitely look into purchasing a metal QEV valve and will reduce the tank size in my plans to 2" or 1 1/2" pipe.
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jackssmirkingrevenge
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Mon Sep 12, 2011 11:38 pm

relatively simple, but very powerful pneumatic cannon
http://www.spudfiles.com/spud_wiki/inde ... Burst_disk
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jhalek90
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Tue Sep 13, 2011 1:20 am

A burst disk would be your best option. Get a 2" PVC union...place it between your chamber and barrel. Use the union to hold a bust disk (a few layers of aluminum foil would be fine) and add pressure.

Once you apply more pressure than your disk can hold, the disk will break and the cannon will fire.

Burst disks are also the fastest type of valve, as they have virtually zero opening time, and provide full flow.
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warhead052
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Tue Sep 13, 2011 10:39 am

I don't think anyone suggested it yet, but an ASCO quick exhaust valve (qev). Or a 1 1/2" quick exhaust valve. Pricey, but worth it according to other members.
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Crna Legija
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Wed Sep 14, 2011 1:41 am

if its purely for power then your much better off with a burst disc valve, they are much cheaper and have the best flow/opening time.
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danielrowell
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Sun Sep 18, 2011 7:39 pm

My cannon is finished! Check it out in the showcase. It's called the Large Object Launcher. I decided to make it convertible between a 1.5" ball valve and a 1.5" PVC union.
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