Counter balanced hammer valve issue

[wyz2285]

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So I built a fairly well made counter balanced valve.
Exhaust 7mm diameter with 9mm piston. Then I compared it to a conventional hammer valve with 6mm exhaust diameter and a shaft of 4mm.
Turns out the balanced valve was weaker. My hypothesis is once the valve is cracked open, the pressure builds up behind the projectile, therefore pressure acts on the 9mm piston instead of the 2mm diameter difference. While the conventional one is harder to open, once opened the pressure only act on the 4mm shaft. So the traditional hammer valve was able to be held open for longer.
Dry fire was very different though, since there is not pressure build up on the exhaust side, the balanced valve was considerably louder.

[hectmarr]

I agree with your analysis. This way you won't have the problem, but an o'ring is necessary.

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[hectmarr]

I don't know if I understood your drawing correctly....

[jackssmirkingrevenge]

There are different configurations for balanced valves, this post should be of interest if you haven't seen it already. Most of them have the opposite problem of not reclosing. The solution for that is the same as the spirit of Hector's suggestion, bleeding air from the transfer port in order to force an imbalance while the valve is open.

[wyz2285]

The bleeding will not be possible in my case, I don't have the space for that.
Must say I'm stunt with this. I removed the return spring and the balanced valve would still close and no power increase at all. In fact I'm getting half the power compared to the normal valve

[hectmarr]

You could try a mechanical lock.

[hectmarr]

There are different configurations for balanced valves, this post should be of interest if you haven't seen it already. Most of them have the opposite problem of not reclosing. The solution for that is the same as the spirit of Hector's suggestion, bleeding air from the transfer port in order to force an imbalance while the valve is open.

I wonder if the force of the seal against the seat can be greatly diminished.
Apparently, the question is: smoother to open vs less sealing pressure, with the risk of air leaking from the HPA reservoir.
I assume that there will be a balance, and that the seal material, which is normally hard for a common unbalanced pcp valve, in this case, as the force decreases, it should be softer.

[jackssmirkingrevenge]

In my experience of balanced valves it cannon be too unbalanced if you are using a material like delrin to seal.

[hectmarr]

In my experience of balanced valves it cannon be too unbalanced if you are using a material like delrin to seal.

Sorry, but I did not quite understand what you say.
On the other hand, is there a commercially available pcp weapon with this type of unbalanced valve? I mean, do you make something like that?

[jackssmirkingrevenge]

There are some commercially available valves as upgrade parts like the Cothran Powerhouse, I had made an animation of how it functions. That particular valve adds a floating element to regulate the "bleed" and therefore valve reclosing, though I'm not sure how much of a difference it actually makes compares to a narrow bore port.

There are some variations available in production models, for example the valve in the Huben K1 uses a different kind of balance and is biased towards opening, being held shut by a mechanical sear. The hammer valve on the Weihrach HW40/Beeman P3 is a balanced spool and in fact uses a rubber o-ring for sealing.

In my own projects the "Caselboy" and Cane Gun upgrade are two examples where hammer strength was a limiting factor and I used balanced valves for higher performance.

[hectmarr]

Okay. Thanks for the info. I'm going to be curious about this.