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All Springer/NP/PCP Air Gun Discussion General > Engineering- Research & Development

Valve Design

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sb327:

--- Quote from: CableStop on July 07, 2022, 07:36:13 PM ---
--- Quote from: MJP on July 07, 2022, 04:24:18 AM ---Looking at the design, I would say it's a dump valve.
O ring at the barrel end has more surface area than the stem so once open it blows completely open and stays that way until reservoir pressure times surface area is below the spring pressure.

Marko

--- End quote ---

I think it should work like any other valve, the poppet sits on a seat like normal it's just that after the air passes by it, it turns 180 degrees and flows out the front.  The green circle near to the stem is the inlet hole that lets air flow into the pass through, when the valve is shut that hole is covered.

--- End quote ---

I mostly agree that it will act MOSTLY like a dump valve…. But…. If you consider that oring on the right will see pressure on both sides during the shot cycle, it MAY behave depending on how large the projectile and other factors. If a very light projectile or dry fire, it’s probably gonna be a toss up.

Also note though, Airforce guns can get uncontrollable given certain conditions as well.

A larger stem could be a tuning option to get it to behave though.

Dave

CableStop:
I mean if the front o-ring is in an ID groove in the valve body wouldn't that solve any issues with the air pressure?  I don't think you could groove the poppet outlet tube because the walls need to be fairly thin to allow as much airflow as possible. 

sb327:
I mean the piston effect located at the area of the right side oring. This is a force that acts to ‘open’ the valve.

Dave

MJP:
You have surface area before the feed hole, and it is limited to the o ring, pressure is pushing on that area.
Air is expanding after that feed hole as the projectile is moving out the barrel.
It is reducing pressure in the barrel, and the feed hole is a choke point, pressure is higher before that point.
If the valve is still open when the bullet is gone, it won't close, flow is keeping enough pressure differential to keep it open.
Bigger stem and the problem goes away.
I would suggest a different approach, barrel type valve that selects the bore you want to shoot, and one valve that feeds both barrels.

Marko

sb327:
As drawn, the small port shown in the poppet would be a choke point. But I don’t assume these type of drawings to be to scale or ultimately the final design.

That port can be made larger to equal full bore.

Other tidbits need to be considered as well but that would be further into developing the idea on paper.

Dave

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