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(plz help me w/) my 1" 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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(plz help me w/) my 1" piston

Unread postAuthor: FishBoy » Mon Jun 16, 2008 8:22 pm

Ok, i'm in the process of making a piston-valve pneumatic, and I have a question. First I will explain my valve, The piston itself consists of a slightly sanded 1" x 2" wooden dowel, a bolt, 3 small washers, a nut, and a 1 1/4" neoprene washer with a 1" neoprene washer on top of it as the sealing face. When the piston is in the housing, the sealing face is to big to fit into the 1" pipe, so it stays in the gap in the middle of the 1" tee with the dowel extending into the 1" pipe leading to the pilot. Anyway, my question was, do i need any kind of bumper sice (i think; correct me if i'm wrong) the piston will not leave the tee.

edit Ok, i'm changing this, all i care about now is since this won't work, how can i fix it?? :(
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1inPiston.jpg
A simple diagram
T.jpg
This is what it looks like
Last edited by FishBoy on Tue Jun 17, 2008 8:10 am, edited 2 times in total.
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Unread postAuthor: elitesniper » Mon Jun 16, 2008 8:47 pm

barrel needs to be smaller then the sealing face, there no pressure acting on the piston from the front, so it wont actuate.
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Unread postAuthor: FishBoy » Mon Jun 16, 2008 8:50 pm

sorry, could you explain that again?
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Unread postAuthor: elitesniper » Mon Jun 16, 2008 8:55 pm

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Unread postAuthor: FishBoy » Mon Jun 16, 2008 9:58 pm

ya, if you look @ my diagram, you can see how the piston seats onto the 1" pipe going to the barrel (however i may remove the front, small, neoprene washer)
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Unread postAuthor: MrCrowley » Mon Jun 16, 2008 11:38 pm

The barrel needs to be a smaller diameter then the tee socket. There has to be a gap between the seat (where piston seals against the barrel) and the tee. There needs to be a pressure on the front of the piston, in your diagram because the barrel is the same diameter, there is no force acting on the front of the piston.
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Unread postAuthor: daxspudder » Tue Jun 17, 2008 12:20 am

yes you need a bumper, and the pilot volume needs to be as small as will still allow air to be released, which I might be wrong but only need to move 1/4 of the T diameter.

your diagram is alright, but has already been shown a ton of times on this site, I personally have posted an animation that shows it off quite well... MRC=Diagram Nazi
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pistonvalve.swf [ 2.81 KiB | Viewed 579 times ]

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Unread postAuthor: MrCrowley » Tue Jun 17, 2008 12:25 am

Sure am dax :wink:

Here's a How-To I forgot to link in my above post:
http://www.instructables.com/id/Golfbal ... That-Shoo/

It's not for 1" but it shows the principles well enough.
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Unread postAuthor: daxspudder » Tue Jun 17, 2008 12:32 am

Nice how-to, I read your post, and had not seen this until now.... you need a spud tattoo on your forehead, I love this stuff but try not to obsess... like somone MRC
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Unread postAuthor: mega_swordman » Tue Jun 17, 2008 12:40 am

Here is a basic diagram of what is being said.
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Unread postAuthor: FishBoy » Tue Jun 17, 2008 7:33 am

wait I have 1" pipe going to a 1" x 3/4" female adaptor (i wanted interchangeable barrels). Will my piston not work like this?
And if not, how can i fix it?? :(
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Unread postAuthor: jackssmirkingrevenge » Tue Jun 17, 2008 9:42 am

If the outer diameter of your piston is the same as your barrel, your piston will never work, A solution would be to find some (say, 3/4" inner diameter) pipe and epoxy it inside your adaptor in such a way that the piston seats against it.
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Unread postAuthor: FishBoy » Tue Jun 17, 2008 9:50 am

ok, thanks, i'll try it
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Unread postAuthor: jackssmirkingrevenge » Tue Jun 17, 2008 9:57 am

Just to clarify:
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Unread postAuthor: psycix » Tue Jun 17, 2008 3:09 pm

Just learn that pistons always have to be larger then the pipe they seal against and your fine. :D
The only reason for this is that frontal area is needed.
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