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Increasing ball valve efficiency

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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Increasing ball valve efficiency

Unread postAuthor: Kilash » Sat May 11, 2013 12:19 pm

I know a lot of veteran spudders, like JSR, are edemically against use of ball valves due to their slow opening time. But i took a long look at my 3/4 brass , and a idea came to me. If i was to cast a small plug out of epoxy that fits into the hole of the valve's ball, it would form a rough seal of the ball valve as its opening, as the lip of the valve baffle's would keep the epoxy plug in place, until it opens fully. Once it does, the plug should fly out and release the pressure fully into the barrel. The seal of the plug doesnt have to be perfect, even if there is a minimum leak, the majority of pressure is being held back while the valve is taking that split second to open.

Course, yur dealing with a over complicated loading process everytime, but the method itself is super simplistic. Thoughts?
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Unread postAuthor: tigerblues28 » Sat May 11, 2013 1:28 pm

There is no reason to over think it dude. How about you take a look at burst disks. Just add one in in front of the ball valve somewhere in the barrel.
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Unread postAuthor: Technician1002 » Sat May 11, 2013 5:01 pm

A burst disk may pop before the ball valve is fully open. A sabot or other plug in the ball valve is determinately worth investigating.

I'm wondering what could be used that has much lower mass than epoxy. It needs to be non compressible so it does not change size under pressure and rigid so it won't blow out early or jamb. I may look into making some from HDPE.
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Unread postAuthor: Kilash » Sat May 11, 2013 5:57 pm

tigerblues28 wrote:There is no reason to over think it dude. How about you take a look at burst disks. Just add one in in front of the ball valve somewhere in the barrel.
Nick



Yea that would work too :P, but i never used burst disc material before, how reliable are they? I believe with the plug, it be more reliable.
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Unread postAuthor: jackssmirkingrevenge » Sun May 12, 2013 2:07 am

I had proposed this concept to Brian back on spudtech while discussing an efficient design for a marble machinegun, it's basically a variation of the "valveless" idea where the ball valve replaces the detent:

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Unread postAuthor: Kilash » Sun May 12, 2013 12:13 pm

Interesting JSR.

Going back to Technician, I think the epoxy would be fine if the pressure isn't too high. But if it is, then a plug could be cast from aluminum, machined to tolerance and drilled into the center to further reduce weight. That ought be rigid enough for the larger ball valves.

Main issue would be the reloading process. I would think that there would need to be stopper plate or obtrusion to stop the plug, or even a string on the plug. A gun using this would probably have to be a breech loader, I can't imagine trying to reset the plug into the valve from the muzzle end.

All in all, its an option for those who can't get or too lazy to make a quick release valve :P.
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Unread postAuthor: jackssmirkingrevenge » Sun May 12, 2013 5:32 pm

You might as well use a ball valve with a port the same diameter as your barrel and put your chosen projectile inside it, that stopper won't last more than a few shots.
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Unread postAuthor: Kilash » Sun May 12, 2013 6:50 pm

jackssmirkingrevenge wrote:You might as well use a ball valve with a port the same diameter as your barrel and put your chosen projectile inside it, that stopper won't last more than a few shots.


It would require maybe a buffer spring, but with the right material it would ber durable.
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Unread postAuthor: Lockednloaded » Sun May 12, 2013 9:29 pm

also, if you plan on "catching" this plug inside your barrel, the flow is going to be so poor that it will negate any benefits of the "faster" valve
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Unread postAuthor: Kilash » Sun May 12, 2013 10:14 pm

I thought about that, one way to get around that is using a 90 degree bend to the barrel, maybe a tee where the other end of the pipe is used to catch the plug.
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Unread postAuthor: jackssmirkingrevenge » Mon May 13, 2013 1:02 am

Kilash wrote:All in all, its an option for those who can't get or too lazy to make a quick release valve :P.


Don't underestimate the forces involved when it comes to stopping the plug.

Image

It's actually a pretty labour intensive option, and as LnL pointed out the flow restriction will most likely absorb any potential gain in performance.

I would either go "valveless" and use the projectile itself to seal the gap, which literally you can do without modification assuming ball valve port diamter = barrel diameter, or add a burst disk which would allow those crucial milliseconds needed for the ball valve to open further.
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