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Air Used Per Shot

Discussion in 'Technical' started by sagalout, Jan 24, 2021.

  1. sagalout

    sagalout What a plinker!

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    Bit of deja vu? :D
     
  2. BallisticBill

    BallisticBill Too much keyboard, not enough action!

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    Too right! :p

    Get it running right off reg first. :up:

    @td_boy, @jesim1, I think the approach is to see what's happening in the regulated pressure range but taking the regulator action out of the equation so @sagalout can see exactly what the action is doing.
     
    Last edited: Jan 24, 2021
    td_boy, cloverleaf and sagalout like this.
  3. sagalout

    sagalout What a plinker!

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    That wouldn't tell me anything. Look at shot 10 of chart 2:
    Screenshot 2021-01-24 082446.jpg
    I would expect the MV of that shot to be higher (forming part of the curve) not dropping. Up until this playtime serious research I had not tied a "drop" shot to air usage. I know they are happening but this is an interesting development for me. So now I am looking for what has caused that air usage drop? Hammer strike? Poppet tilt? Hammer/EV spring balance? Gamma rays leaking through my tin foil hat?
     
    jesim1, td_boy and BallisticBill like this.
  4. td_boy

    td_boy Donator

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    That chart doesn't tell you anything either only that the regulator isn't working :D.
     
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  5. jesim1

    jesim1 Kit bitch to the Stars

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    This one looks better, I'm not too OTT on this, but 30fps spread is quite a lot, half that is fine though as you will not see the POI shift at normal ranges :thumb:

    When I do a bit shot string I use weighed pellets to avoid the peaks and troughs unsorted ones can throw up.
     
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  6. jesim1

    jesim1 Kit bitch to the Stars

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    Meeow - and I though I was pushing it :laff:
     
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  7. td_boy

    td_boy Donator

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    Wasn't supposed to come across as bitchy - just an observation that may or may not be correct?
    I readily accept I'm no expert, but I wouldn't expect to see a curve like that...
     
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  8. sagalout

    sagalout What a plinker!

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    Not when the gun is off reg :facepalm:, I could keep shooting and get down to 0fps and have a 700+ fps spread.

    What it has shown me is that when I get a "spurious" MV it corresponds to a low air volume being used. I didn't know that before.
     
    BallisticBill and Autodidact like this.
  9. td_boy

    td_boy Donator

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    Ah, now we're getting somewhere, thank you :up:

    A couple of more questions then...

    With a starting pressure of 110 bar and an end pressure of around 70 bar presumably only something like the first quarter of the results is in the regulated pressure range? Or is the regulator set to 70 bar?

    Secondly, while the first results show a reduction in air used per shot with the BT over the unregulated setup - how does that information help when the regulated setup will presumably show a similar reduction per shot?

    I'd like to understand, but at the moment it just seems like comparing apples with oranges.
     
  10. sagalout

    sagalout What a plinker!

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    Working in such a narrow band does not necessarily show all the effects of the alterations I am playing with researching. Here's two successive strings after some alterations. The breadth of flat spot is quite broad.

    Screenshot 2021-01-25 061951.jpg
     
  11. jesim1

    jesim1 Kit bitch to the Stars

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    I still struggle with this TBH, to me it's only 15/16 good shots before it's dropping off the reg by 20+fps in the next couple of shots, it just seems so restrictive when other light weight guns will give you 50+ shots with a better curve straight out the box, this is the reason I binned my Ultra, 25/30 shots was about all it was good for if memory serves me, I was always out of air :oops:
     
  12. sagalout

    sagalout What a plinker!

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    It's never on reg during these tests, the reg set pressure is 130 bar I am only filling to 110 bar. The string in post #19 is 50 shots (230 bar down) on reg at under 10fps.
     
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  13. sagalout

    sagalout What a plinker!

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    @BallisticBill

    Here are the tamed and untamed strings taken this morning in the f-f-f-freezing cold!
    Screenshot 2021-01-25 114003.jpg Screenshot 2021-01-25 114504.jpg Screenshot 2021-01-25 114934.jpg

    Shot 10 on the second chart is interesting in WTF kind of way. I thought it was an error by the moron on the pen but the shots either side look correct. I did a second BT string that also has some interesting results.

    It seems that the BT does raise the MV.
     
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  14. jesim1

    jesim1 Kit bitch to the Stars

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    Sorry bud, I've obviously misinterpreted the info :thumb:
     
    sagalout likes this.
  15. BallisticBill

    BallisticBill Too much keyboard, not enough action!

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    Try charting the MV data on a single chart, and the dB data on another single chart, so you are comparing BT and NBT on the same scale. Or I'll do it if you send me the data.

    I'm not too worried about a shift in MV caused by the BT at the moment... more interested in the variations and trends in each string. The extreme cold and temperature changes between strings may have significant effect on MV - not so much shot to shot, but possibly significant between strings, perhaps within a single string (which unfortunately would 6u99er any conclusions).

    I think you are going to have to be very careful with temperature and pellet weights... and look for other anomalies like that shot #10.

    Hopefully @sagalout's subsequent posts have made it clear. All the shots are off reg, as the reg set point is set higher than both the test range and the optimum for the hammer/valve/TP setup. The reg pressure being too high results in the climb in power after the gun comes off reg. The purpose of doing it this way rather than taking the reg out is this:
    (1) the plenum and the restricted flow though the inlet changes the shape and position of the peak of the unregulated curve. If there is no plenum, or the plenum chamber has a wide opening to the cylinder, the pressure drop behind the exhaust valve is less so the valve will close more quickly, especially at high cylinder pressure.
    (2) If the comparisons are done on reg, there is no easy way of establishing if any variations are due to inconsistency in the regulator operation or inconsistency the BT and hammer action.

    If the BT shows a consistent reduced air usage around the intended reg pressure - say, 90 bar (the peak of the present unregged curve) - it indicates both how much air is being wasted, how many more shots might be available and, importantly, that the blast tamer is operating consistently and reliably. If the blast tamer is found to be inconsistent, causing variable amounts of air being release each shot, then it might be better to compromise on air efficiency and go for better MV consistency.
     
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  16. sagalout

    sagalout What a plinker!

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    I'll do it when I get a moment, I did put all 4 on one chart but that just looked a mess.
     
  17. td_boy

    td_boy Donator

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    Thank you for taking the time to explain that, but I'm still mystified as to why one would pick air efficiency over MV consistency - surely the latter is the holy grail of airgun shooters?
     
  18. BallisticBill

    BallisticBill Too much keyboard, not enough action!

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    The objective is to have both. The question: is that possible?
     
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  19. td_boy

    td_boy Donator

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    Is that not attainable purely by control of the regulator where one is fitted?
     
  20. sagalout

    sagalout What a plinker!

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    I don't think so. Lane talks states you can't have both, you can have high operating pressure, low spread and shot count OR low operating pressure, wide spread and shot count.

    The regulator is just a pressure valve, pure and simple. It is not a magic bullet [pun] for air guns.

    If you haven't seen the useful links thread it's worth a look. If you want to skip to shot count versus efficiency watch :
     
    _foxbat_ and td_boy like this.

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