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Recycling pilot volume

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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Recycling pilot volume

Unread postAuthor: DrKavorkien » Wed Aug 06, 2014 10:50 pm

So, I have a question and would like to know if anyone has had any experience with the subject. So I have a pilot actuated (sprinkler) piston valve, and what I was wondering if there would be any gains (I know, probably not substantial) from recycling the vented pilot volume back into the chamber when it's exhausted. Any help is appreciated.
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Re: Recycling pilot volume

Unread postAuthor: jrrdw » Thu Aug 07, 2014 4:31 am

Might make your cannon honk like a goose after you fire it.....maybe.

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Re: Recycling pilot volume

Unread postAuthor: Gun Freak » Thu Aug 07, 2014 9:22 am

Redirecting it to the barrel would be a better idea. Opening up the pilot to the chamber would cause the valve to stay closed because a piston valve needs a high pressure differential to open. Routing the pilot volume to the barrel however might give the projectile a little push before the chamber volume hits it... although I doubt this would give you any real gain in performance.

What's interesting is, if the piston valve stays open long enough to let a little bit of air out, and then the chamber equalizes the pilot, the valve would close and you would have a near full chamber of air. Then you could vent between the pilot valve and the chamber, and restart the process, giving you semi-auto firing. Its funny you ask, because when I was a n00b, I thought that was actually how piston valves worked.
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Re: Recycling pilot volume

Unread postAuthor: noname » Thu Aug 07, 2014 12:06 pm

Personally I'd use the air to cycle a magazine; redirecting it to the chamber or barrel wouldn't do anything productive enough. The small pilot volume would be adequate to drive an air cylinder/piston rod though and that could translate to a magazine's elevator or ejecting an old shell and chambering a new one, etc.
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Re: Recycling pilot volume

Unread postAuthor: mobile chernobyl » Thu Aug 07, 2014 12:55 pm

The invert mini (Paintball scale, but uses a common "chamber sealing" piston design @ 280-320psi) uses it's pilot volume to push it's bolt forward in a "blow foward" fashion.

http://www.zdspb.com/media/tech/animati ... _16fps.gif

Pretty nifty really.

For those that haven't seen it lately - ZDSPB.com has completely revamped it's paintball marker animations page - there are A LOT of new mechanisms listed, all of which should be great inspiration to those in the pneubmatic side of spudding!

http://www.zdspb.com/tech/misc/animations.html
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Re: Recycling pilot volume

Unread postAuthor: Technician1002 » Thu Aug 07, 2014 2:18 pm

Remember anything producing a back pressure on the pilot will tend to either hold the piston closed, or cause it to close early while reducing the rate it will open. This could reduce the power of the shot.

In Paintball this is OK as the object is not the highest possible power, but a controlled speed under 300 FPS.
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Re: Recycling pilot volume

Unread postAuthor: DrKavorkien » Fri Aug 08, 2014 12:59 am

I'm actually a paintballer, and know how the "mini" works, I like the idea of cycling a magazine though. I hadn't thought of that.
I guess I mis-elaborated on the idea of recycling the pilot volume though, as I had originally thought of it as a means to initially open the main valve, with the main volume of air finishing the job. My idea is to use 100% of the air pumped into the cannon, thus making it completely efficient, instead of exhausting a percentage of it as a pilot.
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Re: Recycling pilot volume

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Re: Recycling pilot volume

Unread postAuthor: jackssmirkingrevenge » Thu Aug 14, 2014 8:41 am

DrKavorkien wrote:My idea is to use 100% of the air pumped into the cannon, thus making it completely efficient, instead of exhausting a percentage of it as a pilot.


A noble quest but honestly, the difference in performance will not be measurable.

I had imagined its implementation here.

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Re: Recycling pilot volume

Unread postAuthor: mobile chernobyl » Thu Aug 14, 2014 9:33 am

jackssmirkingrevenge wrote:......

I had imagined its implementation....

Image


Beautifully simple design! Another one is the sacrificial QDV style valve that Tech made popular - instead of having the balanced spool as the valve move backwards, have it move forwards... and continue down the barrel as the projectile! The name of it alludes me at the moment (Starts with a "P" I believe) but I'm sure JSR knows!
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Re: Recycling pilot volume

Unread postAuthor: jackssmirkingrevenge » Thu Aug 14, 2014 10:58 am

mobile chernobyl wrote:Another one is the sacrificial QDV style valve that Tech made popular - instead of having the balanced spool as the valve move backwards, have it move forwards... and continue down the barrel as the projectile! The name of it eludes me at the moment (Starts with a "P" I believe) but I'm sure JSR knows!


Did it even have a name? I just know it as the "valveless" concept :D Some links:

forums/valveless-pellet-gun-t8912.html

forums/valveless-launcher-patent-t12569.html

forums/valveless-popoff-concept-t18271.html

forums/valveless-cartridge-concept-t21364.html

Of course if this is for paintballs it won't really work to use the projectile to block the breech unless you're using very low pressure levels. On the otherh and, the extreme efficiency of going "valveless" means that you don't need as much pressure.
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