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Piston Valve Question

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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Piston Valve Question

Unread postAuthor: PAspuder » Wed Apr 18, 2007 9:58 pm

I am designing a piston valve for a upcoming launcher and i was wondering if anyone that has build a successful piston valve could give me some pointers on how to build the actual piston. My idea was to use a lathe and grove the piston for o-rings but i would like to know how others are doing it. Any input would be greatly appreciated.
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Unread postAuthor: homedepotpro » Wed Apr 18, 2007 11:56 pm

just look around
there are almost hundreds of examples on this site
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Unread postAuthor: TalonXxX » Thu Apr 19, 2007 12:54 am

The actual piston doesn't have much to it... there are a few variations such as choosing between PVC rod, or turning down a fitting on a lathe to use that. I prefer the latter as it allows for a lighter piston. You then simply plug the ends with spigot plugs. Another plus with the fittings is you can implement a built-in check valve to increase performance. Use two o-rings near the rear end for sealing and stabilization.

For the sealing face I like to use a fender washer the diameter of the piston against the spigot plug, followed by a nice thick piece of neoprene rubber, followed by another washer just smaller than the inner diameter of the seat of the piston, all of which is of course held in place by a bolt.

That's just the way I build my pistons... there are many different methods and like homedepotpro said, just look around... good luck.
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Unread postAuthor: chaos » Thu Apr 19, 2007 1:38 am

how big are you making it??

i put a piece of Al rod in the drill press, got the 4" grinder out and cut groves with a turbo disk. pretty simple. but yer for the final version it will be lathed.
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Unread postAuthor: PAspuder » Thu Apr 19, 2007 12:59 pm

TalonXxX thanks for your response i like your idea of using a check valve that is integrated in the piston but where would i be able to get something like that. By the way i am building it in a 2inch tee just as my first one to see how it works out.
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Unread postAuthor: spudthug » Thu Apr 19, 2007 2:00 pm

u cant put a check valve into a piston lol...all u do is dril a hole throguh it or file a slot in it for the air to go through....make it out of hotglue if its ur first piston..
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4" piston valved cannon-half done..( i spilt my cement...)

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Unread postAuthor: surfbum » Thu Apr 19, 2007 2:37 pm

spudthug wrote:u cant put a check valve into a piston lol


yes you can...

check out this thread:
http://www.spudfiles.com/forums/semi-auto-t160.html
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Unread postAuthor: TalonXxX » Thu Apr 19, 2007 3:22 pm

lol uhhhh ya dumbass... you can implement a check valve into a piston... do a little looking around or better yet, use your imagination before you laugh at my idea. :D

and wtf? hot glue piston? what is this 2nd grade? lol
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Unread postAuthor: AmYisroelChai » Thu Apr 19, 2007 4:38 pm

Ok boys (and Girls) Chizzle wizzle....and read the post carefully...

SpudThug probably meant -was you cant INSERT a check valve into the housing of a piston -waste of money and time.

Hot Glue Pistons are easy and reliable - that was the request of the thread.
:lol:
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Unread postAuthor: lukemc » Thu Apr 19, 2007 4:42 pm

i beg to differ AYC hot glue pistons are not the easyest piston
1 they are heavy (and performance suffers)
2 they are dificult to mold properly
3 you can get the same thing for most chambers just by using a smaller end cap with some duct tape and rubber
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Unread postAuthor: pyromaniac » Thu Apr 19, 2007 5:40 pm

I was wondering since thsi is about pistons would it be possible to uve the butt of a schrrader as the sealing face?
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Unread postAuthor: lukemc » Thu Apr 19, 2007 6:13 pm

well just about anything rubber like with some ability to indent for a seal wokks but i dont know that specific kind of rubber
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Unread postAuthor: AmYisroelChai » Thu Apr 19, 2007 7:14 pm

i beg to differ AYC hot glue pistons are not the easyest piston
1 they are heavy (and performance suffers)
2 they are dificult to mold properly
3 you can get the same thing for most chambers just by using a smaller end cap with some duct tape and rubber

lukmc - if that is so I stand corrected.

PA spudder - try a end cap with tape :)
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Unread postAuthor: PAspuder » Thu Apr 19, 2007 9:54 pm

Guys thanks for the helpful responses i got a good plan in my head that im going to build off of. I will definatly post pics and some solid works models of the valve when i get time to start working on it.
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Unread postAuthor: scatdawg » Thu Apr 19, 2007 10:08 pm

pa spuder, on my current piston which is 2.5 in diameter plastic uhmw i just bolted on a 1/8 inch thick rubber flap with two 3/32 inch equilization holes thru the piston. it works beautifully.
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