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Diaphragm vs. Piston

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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Unread postAuthor: noname » Sun Jul 01, 2007 8:32 pm

Yeah, pretty much. That diagram is a tiny bit misleading though, let me edit it so if you build one, the diaphragm will work....

Argh.
I edited the diagram and somehow deleted it. Just make sure that the diaphragm is about 1 1/8 the size of the pipe ID. For example, use a 2.5" diameter diaphragm if you're using 2" PVC as a chamber.
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Unread postAuthor: Pyro Ninja » Sun Jul 01, 2007 8:43 pm

got cha.. :).....I might make a air rifle pellet gun.....I feel so noobish :oops:
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Unread postAuthor: schismatized » Sun Jul 01, 2007 9:18 pm

to clarify, i will be using a 3" pvc schedule 40 endcap. If i cut say, 1 inch, off the opening to cut weight, will that help any?
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Unread postAuthor: hi » Sun Jul 01, 2007 9:27 pm

thats a piston, but yea it will reduce weight.
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Unread postAuthor: schismatized » Sun Jul 01, 2007 9:32 pm

any other tips to get a little better performance out of that style of piston? i plan on using a 1 inch sprinkler valve with it.
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Unread postAuthor: hi » Sun Jul 01, 2007 9:41 pm

lube it up really well and have a really good bumper.
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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 » Sun Jul 01, 2007 10:05 pm

Fill it with foam or something to reduce pilot volume without increasing piston weight.
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Unread postAuthor: schismatized » Sun Jul 01, 2007 10:34 pm

good ideas. keep em coming! im wondering what would be a decent bumper for 4"? i dont want anything ghetto like hose lol :x
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Unread postAuthor: hi » Sun Jul 01, 2007 11:00 pm

hose wouldnt work any way, you need to find something that will absorb all the energy from it though.
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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: chaos » Sun Jul 01, 2007 11:12 pm

what about those flotation pool noodle thingies? they might be 3" tho
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Unread postAuthor: spud yeti » Mon Jul 02, 2007 3:21 am

I have decided to start building a coaxial diaphram valve cannon since I have just finished my small piston cannon. I have never built a diaphram before :oops: so I have a question: How many layers of inner bike tube do you need for the diaphram? I am building 2" diameter.
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really good quote/phrase here
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Unread postAuthor: noname » Mon Jul 02, 2007 9:36 am

Don't use a bike inner tube. They are much too thin for this application. You need some tough 1/8" thick rubber sheet.
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Unread postAuthor: spud yeti » Mon Jul 02, 2007 9:41 am

OK thanks. Cant you just use 2 or 3 layers though??
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Unread postAuthor: noname » Mon Jul 02, 2007 10:39 am

You can, but either it'll pop, get sucked into the barrel, or only one layer will get sucked back into the pilot area.
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Unread postAuthor: spud yeti » Mon Jul 02, 2007 10:48 am

OK cool, I think I will just go look for some rubber at the store :wink: thanks for the help though.
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