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Balanced Hammer Valves

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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Re: Balanced Hammer Valves

Unread postAuthor: Skywalker » Sun Apr 07, 2019 1:02 pm

These are cool, but can they be re-arranged to look more like the typical piston gun, where the porting is full-bore straight into the breach? I guess you'd need an awkward hammer that pulls, rather than pushes, the stem.
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Re: Balanced Hammer Valves

Unread postAuthor: jackssmirkingrevenge » Mon Apr 08, 2019 8:13 am

Skywalker wrote:I guess you'd need an awkward hammer that pulls, rather than pushes, the stem.


This is more or less how the Beeman P17 works, here's the valve assembly:

Image

The hammer pulls it open:

Image

In the world of spuds, it's more or less the "QDV" that's been spring-loaded.
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Re: Balanced Hammer Valves

Unread postAuthor: Skywalker » Mon Apr 08, 2019 8:47 pm

Interesting -- so it's a dump valve, though. Looks to me like the unbalanced force is going to blast it open and keep it that way, just like the QDV.

I sketched up an idea for a balanced version of the AirForce Condor. The basic idea is to transfer the hammer strike through a movable cylinder to the valve face, launching the valve open. I didn't draw the return spring on the valve-pusher cylinder b/c it was getting busy in the diagram.

Edit: answered my own dumb question.
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Balanced Condor valve
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Re: Balanced Hammer Valves

Unread postAuthor: jackssmirkingrevenge » Tue Apr 09, 2019 5:54 am

Skywalker wrote:Interesting -- so it's a dump valve, though. Looks to me like the unbalanced force is going to blast it open and keep it that way, just like the QDV.


Yes, it's a single stroke pneumatic so no point in keeping any air in the chamber after firing.

I sketched up an idea for a balanced version of the AirForce Condor. The basic idea is to transfer the hammer strike through a movable cylinder to the valve face, launching the valve open.


That actually looks pretty good. Hmmm...

You're still going to need a heck of a hammer to open it for a big bore though, even though there might be no pressure differential, o-ring friction is going to be very significant for larger diameters. I think a hammer-piloted piston valve would be a more practical idea:

Image
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Re: Balanced Hammer Valves

Unread postAuthor: Skywalker » Tue Apr 09, 2019 8:43 am

I'd been ignoring friction for the most part. Friction isn't an entirely bad thing for this design, though: the valve-pusher cylinder should *not* travel with the poppet valve -- it needs to stay behind so that the poppet unseats. The whole train of (hammer --> breach slide --> valve pusher --> poppet) needs to act like a Newton's cradle. The valve pusher should only have 1mm possible travel before the ring (which the breach slide impacts) touches the sleeve that the pusher rides in. Additionally, the seals around the push could be made relatively loose/leaky, because the flared end of the pusher could seal against the interior of the 'T', so that the sliding seal is only needed for an instant when the pusher is in motion. In fact, if the sealing material had some give, and the pusher didn't move too far, then this face seal would never even be broken.

I can't think of a reason to prefer the design I drew over the hammer-piloted resetting piston valve you drew, though. In fact, it seems to really just clutter up the breach area -- which is one thing people complain about with the Condor: it has to be manually loaded, and the space is small enough to be difficult for folks with large hands. (Not to mention you are sticking your fingers in the path of the hammer....)

Perhaps the amount of wasted air would be slightly smaller with this design... although the trade-off is increased dead space in the breach between the valve and the pellet.
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