Howdy,
How can I know that the valve closes before projectile leaves the barrel. Is there any way to check it empirically?
How can I know that the valve closes before projectile leaves the barrel. Is there any way to check it empirically?
Closing the valve before projectile leaves the barrel
- Thread starter Seeker
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Any time you get over 1.0 fpe/ci you're doing around 50-60% of the barrel. 1.3~ fpe/ci is around 30% of the barrel.
To calculate that use http://calc.sikes.us/1/
Although you need to make sure you stay above regulator pressure if regulated to keep that calculation accurate as it does not account for it.
To calculate that use http://calc.sikes.us/1/
Although you need to make sure you stay above regulator pressure if regulated to keep that calculation accurate as it does not account for it.
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There is fancy way of doing it and then there is a simpler way of doing it.
https://youtu.be/VjqD-eQwyHo
this video from Ted IMHO is one of the best airgun tuning videos of all time regardless of the gun brand.
https://youtu.be/VjqD-eQwyHo
this video from Ted IMHO is one of the best airgun tuning videos of all time regardless of the gun brand.
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This is why I like the FX Impact. A lot of adjustments for fine-tuning. Key word is "fine-tuning"
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Is the dry fire sound significant over the pellet fired sound? I am not sure how to.measure, other than by sound output.
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I can't tell with the sound of a dry fire. Only when a projectile is leaving the barrel can I hear when nirvana arrives.
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Because that is how the math generally works out with pneumatic air guns and efficiency with air, the difference in stroke (barrel length) and efficiency change proportionally. Ergo, there is a PEAK efficiency (2.5~ fpe/ci), where it doesn't matter HOW long the barrel is, you nip the valve to where it closes before the pellet even begins to move, the peak efficiency of power you can attain from that burst of air is gonna remain, the length of barrel used will bet the same regardless.
Calculate the air usage by volume, and compare it to your barrel volume. If you release 5 cc of air, and your barrel is a total of 10 cc's, the valve is remaining open until the pellet is approximately half way or 50% down the barrel since the volume use is half that of the barrel volume.
You will need the following formula to get the new volume of the air column that has left your air tank into the barrel.
v2 = (v1*p1) / p2
Where v = volume and p = pressure
v1 = plenum volume
p1 = plenum pressure
v2 = new volume in barrel (which can determine % of barrel used)
p2 = pressure present at pellet base
To get pressure 2, you need to account for pressure drop, which depends on your plenum volume. If you release 5cc from a 50cc plenum, that is 10% pressure drop, if you release 5cc from a 25cc plenum, that is a 20% pressure drop...and so on. There is also "wasted volume" one must account for which is the empty volume between base of pellent and valve seat, quit commonly around .5-1cc...so if you have a 50 cc plenum, that would be a 2% drop on top of the additional 10% drop if you were to release 5cc before the pellet even sees any pressure, for a total of 12% loss. Using that, if I were regulated at 2000 psi, that is 240 psi less at the pellet, at 1760 psi.
Taking the above example of 1760 psi, with 2000 regulated pressure and 5 cc volume released into a 10 cc barrel.
v2 = (v1*p1) / p2
(5*2000) / 1760 = 5.68
Therefore v2 = 5.68 CC, 5.68 cc / 10 cc = 56.8%.
Hope this helps..
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Hammer bounce is a more common source of wasted air, Imho. But I am not any kind of expert.
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Hammer bounce definitely wastes air so free floating hammer system like the ones in FX guns are extremely efficient. That or a hammerless system like L2.
you can’t tell the difference with dry firing, you need to be shooting pellets or slugs to hear when you are in the right zone because the muzzle report is distinctively different. Along with the sound if you are a little below the knee of power curve should get you there.
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There is most definitely an audible difference but it's not a trivial matter to communicate to someone how to recognize it to any meaningful degree of precision. Meanwhile tuning to a percentage of the maximum velocity is super easy and precise for anyone with a chronograph...or the price of a couple of tins of pellets for anyone currently without this indispensable tool.
https://www.aliexpress.com/item/1005001316179856.html
https://www.amazon.com/VIKKA-Precision-Chronograph-Velocimetry-Chargeable/dp/B08DRJ3JW7
https://www.aliexpress.com/item/1005001316179856.html
https://www.amazon.com/VIKKA-Precision-Chronograph-Velocimetry-Chargeable/dp/B08DRJ3JW7
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Ernest roux also has a very nice video for tuning the impact.
he does it very similarly. But he takes it a step farther and also tunes the valve.
he does it very similarly. But he takes it a step farther and also tunes the valve.
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Another tell tale sign is when I see a giant can on the end of any gun .25 and smaller, I know that guys gun is wasting air. When you get a gun sipping air, it doesn’t take much to keep it quiet.
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Another +1 for this. Best money I have spent to date for my airguns. Have owned one for over 2 years. It is accurate and has never failed to give a reading.
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You can achieve this with a good balance between hammer spring tension and regulator pressure.
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