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Diaphragm Valve Pistol

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: noname » Thu May 24, 2007 10:29 pm

Hi, you don't need anything to hold a diaphragm in place. On my diaphragm <a href="http://www.spudfiles.com/forums/extreme-coaxial-now-with-stock-t2316.html">paintball gun</a>, it just sits in there and flexes back and forth by itself. It's just like a piston, except opens faster and is more compact.

By the way, love seeing great looking spare parts guns, awesome job with it.
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Unread postAuthor: Macgyver440 » Fri May 25, 2007 12:29 am

I will be painting the gun soon after I put an end cap on the bottom of the pistol grip to cover the sharp edges where I cut the pipe for the blowgun nozzle. Also the diaphragm is a disk I cut from some thin PVC sheet, glued to the back of the PVC pipe that makes up the air chamber. The end cap holds the tire valve and the hose barb fitting that links the blowgun nozzle. The tire valve also has a little piece of PVC glued to the inside to act as a check valve to keep air inside when the chamber is pressurized. The obvious sucky part is the idea that the cap is glued on so if something happens to the diaphragm in any way Ill have to cut the gun up to make any repairs then glue everything back together. But thats the cost of a spare parts gun. As far as buying the darts, go to http://www.coldsteel.com/blowguns.html or http://www.blowgunsnorthwest.com/62cal.htm
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Unread postAuthor: hi » Fri May 25, 2007 1:07 am

sorry, but i guess i dont understand. why doesnt the diaphragm get sucked into the barrel? on a sprinkler valve it is wedged between two peices. I know how a piston works and have built many, but i dont get how it wont get sucked into the barrel. does the diaphragm have a bolt on it or something?

please explain.
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Unread postAuthor: jackssmirkingrevenge » Fri May 25, 2007 6:50 am

The diaphragm is usually quite thick and wouldn't fit through the barrel anyway, and don't forget the friction caused by the pressure on the barrel edge.
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Unread postAuthor: hi » Fri May 25, 2007 8:44 am

so if i used a inner tube it would get sucked in, but if it was like 1/4'' thick it would be ok?
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Unread postAuthor: jackssmirkingrevenge » Fri May 25, 2007 8:58 am

hi wrote:so if i used a inner tube it would get sucked in, but if it was like 1/4'' thick it would be ok?


hexactly :)
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Unread postAuthor: noname » Fri May 25, 2007 7:11 pm

1/4" wouldn't be very flexibble so it would suck. I use 1/8" thick rubber, which is flexible, but there's no way you could ever fit in through the barrel, even if you rolled it up lengthwise. Try making a diaphragm valved gun, you'll find it easier than pistons (I really don't understand why people think diaphragms are so hard).
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Unread postAuthor: hi » Fri May 25, 2007 7:38 pm

i know how they work, i just thought that it had to be between a union or something.

so in a diaphram there is no need for a bumper is there?
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

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Unread postAuthor: noname » Fri May 25, 2007 10:31 pm

No, usually diaphragms are made out of what people use for bumpers. The force of a thin rubber circle smacking a piece of pipe won't do much.
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Unread postAuthor: hi » Fri May 25, 2007 10:39 pm

so does it also have to be perfectly round like piston? can i simply take the piston out of my gun and put in a diaphragm without changing anything else??
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Unread postAuthor: noname » Fri May 25, 2007 10:50 pm

The answer to both questions is yes. If you remove a piston and put in a diaphragm, there will be more pilot volume and you will probably have to replace the diaphragms every shot. This is because the diaphragm will fly off the barrel seat into the pilot area. Make sure the diaphragm is about 1/4" bigger (1/4" bigger for 2" PVC, use proportions) on each side, so that you ned to flex it inward to push it into the gun. Push it in, little by little, equally on all sides. If you're impatient, it'll spin sideway and make you remove it and put it in again.
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Unread postAuthor: hi » Fri May 25, 2007 10:55 pm

i see, thanks. i think im off to build i diaphragm valve now.
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Unread postAuthor: Macgyver440 » Tue May 29, 2007 2:53 am

I agree with Noname, I find diaphragm guns much easier to build than piston valve guns. Ive tried a few different approaches to the piston valve idea and had all of them fail. As for my diaphragm, its made of that thin (1/8") flexible PVC crap that is used for lining showers or something like that, you can get it in the plumbing section at home depot, cut from a roll and sold by the foot. I cut the disc and super glued it to the back of the 1 1/2" pipe, or in some of my other designs glued it to the rim of the threaded adapter before screwing on the end cap. Of course if it messes up Ill usually have to destroy the disc to get it off, but when you can buy a sheet of this stuff thats a foot by some four feet, the supply of diaphragm discs is almost endless.
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