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First piston valve (barrel sealing)

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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First piston valve (barrel sealing)

Unread postAuthor: whoa044 » Sun Apr 24, 2011 12:52 am

First off, I'd like to point out I'm aiming for operating pressures of 600-1000psi
I'm not sure whether or not there have been piston valve guns of this pressure before.

I will be trying to follow this youtube guide, but I'd like to know if hot glue, and a rubber washer as a bumber would be fine to use at pressures exceeding 600psi. I could also use epoxy and resin. Which would work better? If I use epoxy, should I try to have a lot of bubbles within the piston?[/url]
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 24, 2011 12:56 am

Hot glue is probably not going to survive. This was my HPA piston valve.
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Unread postAuthor: whoa044 » Sun Apr 24, 2011 1:10 am

Ahh high impact marine epoxy. Makes A LOT of sense..... "high imapact" haha.
I'm probably going to cast it using the fitting, which the piston travels through, as a mold.

Thanks man!

I see you've used CO2 (amirite?) in your gun.
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 24, 2011 1:19 am

whoa044 wrote:I see you've used CO2 (amirite?) in your gun.


Nope, HPA. I have two Ninja paintball tanks (13 ci and 48 ci) that I fill from my scuba tank.

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Unread postAuthor: Technician1002 » Sun Apr 24, 2011 6:08 am

I don't think the design in the youtube video is good for much over 100 PSI without a more substantial piston and the use of a proper bumper. At higher pressure an effective way to decelerate the piston without damage must be used.
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Unread postAuthor: jrrdw » Sun Apr 24, 2011 6:51 am

Technician1002 wrote:I don't think the design in the youtube video is good for much over 100 PSI without a more substantial piston and the use of a proper bumper. At higher pressure an effective way to decelerate the piston without damage must be used.


Coil spring prehaps...
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Unread postAuthor: MRR » Sun Apr 24, 2011 7:28 am

Since I am the author of the video and have some experience with hot glue pistons, I can say that they are very durable even under high pressure. There are different kind of hot glues on the market, the stuff that was used in the video is very tough.

With a reinforcing metal washer between the sealing gasket and the piston body (to redirect the forces to a bigger surface) I was able to take my launchers past 300 psi with no problems. The piston itself showed no deformation whatsoever after a longer time of use (using one rubber gasket as a bumper).

The only downside of hot glue pistons is that you can't use mineral oil based lubricants because it dissolves the surface of the piston and makes it sticky.
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