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Coaxial piston valve problem

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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Coaxial piston valve problem

Unread postAuthor: Tom » Sun Oct 07, 2007 12:27 pm

I have some problems with my piston valve, it´s a coaxial barrel sealing. The problem is that when I charge the valve and let the pilot air go the piston wont move(just a little bit). What can be the problem, i had some things in mind like; charge from the pilotspace instead of the chamberspace, more air presure. Then I'm wondering could the problem be lying by the spring, the spring is not very strong but just good enouch to make a good seal.
GR.Tom
EDIT: I'm using PVC 32MM, the piston is made from melted glue sticks and a sheet of PVC.
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Unread postAuthor: hi » Sun Oct 07, 2007 12:38 pm

im want to laugh. your idea of possibly "charging from the pilot space" is exactly the problem. you must charge from the pilot space or it wont seal. you could try all day to fill from the chamber and it would never work.

try filling from the pilot area and i can almost garentee that will fix the problem.

good luck.
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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: clide » Sun Oct 07, 2007 1:48 pm

hi wrote:im want to laugh. your idea of possibly "charging from the pilot space" is exactly the problem. you must charge from the pilot space or it wont seal. you could try all day to fill from the chamber and it would never work.


Unless he has a spring...which he does.

Sounds to me like your piston has too much flow past it or you pilot valve isn't big enough. What are you using to vent the pilot area?
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Unread postAuthor: Tom » Sun Oct 07, 2007 1:55 pm

Whel gentleman, my piston seals olmostly perfect with some vaseline. I just made a new barrel inside because there would be 3 MM space between barrel and housing(not ideal for a coaxial :D ). Tomorrow I will test the valve filling from the pilot space.
GR.Tom
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Unread postAuthor: Brian the brain » Sun Oct 07, 2007 2:00 pm

Clide is right.
To fix this problem, get a bigger ( or faster) exhaust valve and make sure the piston has a very narrow fit.
Then fill from the pilot side.( better, although not neccesary when using a spring)

32 mm indicates you are using regular ( thickwalled perhaps) pvc.

This stuff WILL blow up! maybe not the first time, but it defenitely will.
Order pressre rated pvc and dump the normal stuff!!!
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: Tom » Sun Oct 07, 2007 2:13 pm

The man that helped me at the shop told me that the pipe was pressure rated to a maximum of 80 PSI(I wont need more). I will order a better pipe if it isn't working good.
GR.Tom
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Unread postAuthor: Brian the brain » Sun Oct 07, 2007 2:24 pm

If it isn't working well, it will blow up.
Sending scrapnel into your face or possibly your nuts!!...You want to risk that??

You can order ( in holland) at www.bouwplastics.nl
I believe they have the biggest stock and best price.
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: Tom » Sun Oct 07, 2007 2:37 pm

@BTB
What is the shippings price, i can't found it at the website.
GR.Tom
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