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Piston Valve Design

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 Design

Unread postAuthor: Mr.Tallahassee » Sun Jul 10, 2011 9:36 pm

I've been doing research while trying to figure out a new valve for my airguns. I thought about it and put a QDV design together with a regular pilot actuated piston valve design. How well might this work? I'm not certain if this is a QDV or a QEV.
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Unread postAuthor: saefroch » Sun Jul 10, 2011 9:40 pm

It's not a QDV. It is quite a bit like the piston I built for my Trident (link in my sig, if you're interested).
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Unread postAuthor: Mr.Tallahassee » Sun Jul 10, 2011 9:46 pm

I just realized I did not need a check valve on this design :oops:
This would still be an efficient valve though, right?
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Unread postAuthor: Gun Freak » Sun Jul 10, 2011 9:56 pm

The valve won't work. Assuming your piston is airtight because of the check valve, upon filling, your piston would just move back and the fill air would go out the barrel. If you want a check valve piston, you have to fill pilot. Other than that, it's just a normal piston valve, no resemblance to a qdv.
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Unread postAuthor: Mr.Tallahassee » Sun Jul 10, 2011 10:02 pm

I realized that after I posted it. It won't have a check valve in the real thing. Could I melt scrap HDPE for a piston? I'm on a very tight budget with this project.
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Unread postAuthor: jackssmirkingrevenge » Sun Jul 10, 2011 10:13 pm

Ditch the o-rings and the check valves and put a spring behind the piston and you'll be fine.

I'm on a very tight budget with this project.


Let binary adhesives into your life ;)
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Unread postAuthor: Mr.Tallahassee » Sun Jul 10, 2011 10:46 pm

I would love to use epoxy but it's a bit expensive to use for making a 2'' pistons. :? I thought about using wood disks bolted together in the way shown in the pic. It's for my newest PVC gun http://www.spudfiles.com/forums/second-pnuematic-launcher-t23007.html
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Unread postAuthor: Technician1002 » Sun Jul 10, 2011 11:01 pm

Mr.Tallahassee wrote:I realized that after I posted it. It won't have a check valve in the real thing. Could I melt scrap HDPE for a piston? I'm on a very tight budget with this project.


To save you the trouble, I was on a budget when I built a competition t shirt launcher. Melting milk jugs and such is a waste of time. Just before it it hot enough to burn, it becomes the consistancy of gummy bears. It forms into a solid mass much the same as a bowl of gummy bears.

I did use some sheets of HDPE and used heat and LOTS of pressure to clamp them together. This worked OK but it is more difficult than it is worth.
Photos and how to do this is on this page from the contest.

https://inteltrailblazerschallenge.wikispaces.com/The+brag+zone
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Unread postAuthor: jackssmirkingrevenge » Mon Jul 11, 2011 12:00 am

Mr.Tallahassee wrote:I would love to use epoxy but it's a bit expensive to use for making a 2'' pistons :?


If the piston is built up as opposed to being cast as a solid block, you're not going to use much. Some cheap filler like sawdust will make it even more economical.
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Unread postAuthor: Gun Freak » Mon Jul 11, 2011 9:31 am

Or you could make it cup shaped to decrease weight.
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