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Homemade Diaphragm Valves

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Homemade Diaphragm Valves

Unread postAuthor: noob of noobs » Thu Jun 18, 2009 4:52 pm

So piston valves seem to be current standard of high quality spudding, and for good reasons. However, we don't see that many diaphragm valves, even though they're very similar to piston valves and probably easier to build.

Why is this?


The reason I ask is this: I'm making a paintball gun that's hooked up to a propane tank as its air source (CO2 and HPA are too expensive), and I'm considering using a homemade diaphragm valve because they're easy to fix and they rarely jam. This I figure is a decent compromise between the weak and reliant SV and the strong yet inconsistent Piston valve, but I'd like your opinion.

Thanks!
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Unread postAuthor: mobile chernobyl » Thu Jun 18, 2009 8:39 pm

Diaphragm valves were pretty common a few years ago. Spud-launching technology advances, and we have easy to build piston valves now.

Diaphragm valves also are usually limited to a coaxial design, or a "tee" design where the port must extend back pretty far - the piston valve allows more freedom with that.

And I don't get what you mean by "strong yet inconsistent piston valve" - Perhaps you are looking at the failures on here more than the success stories. A properly designed piston valve will operate flawlessly for hundreds to thousands of shots - depending on the media being shot (i.e. if your shooting liquids or sandy stuff, that can mess up the sealing surface).
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Unread postAuthor: noob of noobs » Thu Jun 18, 2009 10:35 pm

What I meant with the piston valve being inconsistent is just my own experience. I've always had problems with pistons getting jammed or not sealing properly, which has mostly been due to ill construction. I have a bad record with piston valves...

So diaphragm valves are inconviniently sized. Is there a noticeable inferiority to piston valves in power/speed?
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Unread postAuthor: Velocity » Thu Jun 18, 2009 11:48 pm

Diaphragm valves often have less power than piston valves. While the opening speed is superior due to the low weight of the diaphragm, the flow is restricted.
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Unread postAuthor: THUNDERLORD » Fri Jun 19, 2009 12:20 am

If it's inconsistent for you maybe keep trying (?)
Ball valves open pffftt...most diaphrams...bawhump... pistons... POP!!... burst discs... BLAM!!!
Or you can be scientific and check GGDT. :roll:

There have been lots of coaxials that used a large round piece of rubber to seal the barrel in the past.

Loading other than muzzle would be tricky, unless it had a Blow- forward bolt with magazine passing through the chamber, but then, how much pressure would the sheet of rubber hold(?)

Someone on here built a huge diaphram valve. ( :oops: who?)...
Anyway, if you come up with a new one, 8) 8)
EDIT: maybe some kevlar sheets coated in rubber would work (?)
(My M.C. has a kevlar/ rubber drive belt).
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Unread postAuthor: Technician1002 » Fri Jun 19, 2009 1:18 am

mobile chernobyl wrote:Diaphragm valves were pretty common a few years ago. Spud-launching technology advances, and we have easy to build piston valves now.

Diaphragm valves also are usually limited to a coaxial design, or a "tee" design where the port must extend back pretty far - the piston valve allows more freedom with that.

And I don't get what you mean by "strong yet inconsistent piston valve" - Perhaps you are looking at the failures on here more than the success stories. A properly designed piston valve will operate flawlessly for hundreds to thousands of shots - depending on the media being shot (i.e. if your shooting liquids or sandy stuff, that can mess up the sealing surface).


I second that. Other than the cracked PVC piston valves, mine have worked flawlessly. A clean and lube once in a while is all they need. The DWV ABS cannon is nearing a decade old and still used every year. My newest 2 are flawless in operation.
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