FX FX Impact M3 experiments with valve dewel time

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mubhaur

mubhaur

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Nov 8, 2015
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In Impact we can limit the lift of the valve by adjusting the valve adjuster. The valve adjuster doesn't affect MUCH on dewel time.

As per my experiments the reduction of dewel time is often very important for shot cycle, efficiency and consistency.

The standard valve spring is made of wire of around 1mm thickness and is not hard enough to limit the dewel time. However, the lift of valve can be controlled even with the valve springs of thinner wires.

I had very short time as I am not feeling well, I just tried following springs as valve return springs while the regulator was at 125 bars.

Following is OEM spring.

20241125_174317.jpg
20241125_174336.jpg


Following are two harder springs.

20241125_174154.jpg
20241125_174203.jpg
20241125_174243.jpg
20241125_174355.jpg
20241125_174409.jpg


Shot cycle and efficiency of the gun has been improved.

I couldn't test more.

Bhaur
 
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I was also playing this spring force on my Crown- The original spring is equal to approx. 1/10 of the air pressure force closing the valve at 130 bar.
Unfortunately I found that the original spring was giving the best results on my Crown. I tried both increasing and decreasing spring force in steps with + / - 50% of the original spring. Reducing spring force slowed speed a lot - I guess the valve was open to long time, due to longer closing time for the valve. (equal to hit the hammer too hard - over the knee problem). At a point I was afraid that the pressure with the open valve would keep the valve open. But I did not face that problem..... Harder spring also slowed speed... so I have now a small collection of springs, and that is of course always nice :)
 
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engfred said:
I was also playing this spring force on my Crown- The original spring is equal to approx. 1/10 of the air pressure force closing the valve at 130 bar.
Unfortunately I found that the original spring was giving the best results on my Crown. I tried both increasing and decreasing spring force in steps with + / - 50% of the original spring. Reducing spring force slowed speed a lot - I guess the valve was open to long time, due to longer closing time for the valve. (equal to hit the hammer too hard - over the knee problem). At a point I was afraid that the pressure with the open valve would keep the valve open. But I did not face that problem..... Harder spring also slowed speed... so I have now a small collection of springs, and that is of course always nice :)
Click to expand...
Playing with the spring force is much easier in Impact.

So far installing a harder spring has made the sound snappier.

It's consistent and I can leave the regulator pressure high for both calibers .22 and .25

Accuracy has yet to be known.
 
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Troy Bakel said:
1. How are you physically measuring dwell time?
Click to expand...
I can't physically measure the dewel time but I understand from my past experience that when a harder valve return spring is applied, valve takes less time to shut down.

The force of hard valve spring is very low as compared to the regulator pressure force but once the valve is opened, the hard valve spring plays it's role in shutting the valve quickly as during dewel time the force of regulated air on valve is greatly decreased.

The sound of the gun tells the story.
 
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mubhaur said:
In Impact we can limit the lift of the valve by adjusting the valve adjuster. The valve adjuster doesn't affect MUCH on dewel time.

As per my experiments the reduction of dewel time is often very important for shot cycle, efficiency and consistency.

The standard valve spring is made of wire of around 1mm thickness and is not hard enough to limit the dewel time. However, the lift of valve can be controlled even with the valve springs of thinner wires.

I had very short time as I am not feeling well, I just tried following springs as valve return springs while the regulator was at 125 bars.

Following is OEM spring.

View attachment 515532View attachment 515531

Following are two harder springs.

View attachment 515533View attachment 515534View attachment 515537View attachment 515535View attachment 515536

Shot cycle and efficiency of the gun has been improved.

I couldn't test more.

Bhaur
Click to expand...
Thanks, Feel better.
 
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mubhaur said:
I can't physically measure the dewel time but I understand from my past experience that when a harder valve return spring is applied, valve takes less time to shut down.

The force of hard valve spring is very low as compared to the regulator pressure force but once the valve is opened, the hard valve spring plays it's role in shutting the valve quickly as during dewel time the force of regulated air on valve is greatly decreased.

The sound of the gun tells the story.
Click to expand...
How did you determine that : "The valve adjuster doesn't affect MUCH on dewel time."?
 
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