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Piston shuttle pilot sealer?

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 shuttle pilot sealer?

Unread postAuthor: boyntonstu » Mon Sep 14, 2009 7:48 am

Would 2 seals be better than 1?

The piston would seal the barrel upon pressurizing the chamber.

When the pilot opens the piston would shuttle from sealing the barrel to sealing the pilot.

Just thinking out loud.
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Unread postAuthor: qwerty » Mon Sep 14, 2009 7:59 am

QEVs seal after the pilot so does the piston in my small coaxail its just the rubber wheel pressing againt the coupler. So yes it would be better because you wont loose any air out of the pilot.
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Unread postAuthor: Technician1002 » Mon Sep 14, 2009 8:31 am

Just my take, In testing I have removed the barrel and capped the valve to see the discharge time in comparison to a normal discharge. This was done as part of my safety tests to be sure the bumper would handle a very high force without failure.

On my valves, the pilot leakage takes several seconds to bleed off the pressure. When fired normaly the event is over in less than 20ms or 0.02 seconds. This indicates that less than 1% of the air escapes out the pilot, so I don't worry about it. It's not enough to even enough to feel blowing out when operating them.

A small eq port is all that is needed for low pilot losses.
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Unread postAuthor: MRR » Mon Sep 14, 2009 11:34 am

The loss of pressure through the pilot is no big deal when you use a very small equalization hole.

But, when you build on a bigger scale and fill from the pilot it is pretty annoying to wait for the chamber to be filled (with compressor or tank). That's why I prefer floating o-rings or build in check valves.

You simply can't do anything wrong with it.
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Unread postAuthor: Technician1002 » Mon Sep 14, 2009 12:19 pm

MRR wrote:The loss of pressure through the pilot is no big deal when you use a very small equalization hole.

But, when you build on a bigger scale and fill from the pilot it is pretty annoying to wait for the chamber to be filled (with compressor or tank). That's why I prefer floating o-rings or build in check valves.

You simply can't do anything wrong with it.


True. One of my earlier cannons had two fill valves. A quick shot to the pilot closed it and created the initial pressure to hold it closed and then it could be filled directly into the chamber.

Since then I moved to another style valve that is closed by hand and only filled in the chamber at any delivery rate I can get. I second your preference for floating o rings.
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