why chronos can be fooled...

Discussion in 'General Airgun Chat' started by RobF, Aug 16, 2011.

  1. RobF

    RobF Administrator Staff Member

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    this is why muzzle brakes, silcencers, moving the muzzle back from the sensor and putting bits of paper over the muzzle can all increase muzzle energy readings...

    http://www.youtube.com/watch?v=gWGLAAYdbbc

    and on a .44 rifle putting out around 600 ft-lb we're recording chrono readings at the club 6ft back from the chrono because of this effect... that and using IR so any light change isn't affecting the chrono...
     
  2. sportsmatch

    sportsmatch Member

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    I used chrono my 38 super in the good old days of pratical pistol with a pact chrono/timer around 5 ft from the muzzle to stop the gas pressure triggering the second sky screen before the bullet


    Gary
     
  3. Jon

    Jon Member

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    Its one of the reasons but there are others.

    Must get the CED out
     
  4. Jon

    Jon Member

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    Might be easier to understand off this 30.06 vid
    1min 20 sec in http://www.youtube.com/watch?v=kkSKIWAks4k&feature=related

    Question is, does this trip the first and second exit sensor before bullet reaches that first sensor, i would say it does or can.

    What about light playing havoc with the timing as proved time and time again over the years?
     
  5. RobF

    RobF Administrator Staff Member

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    From what i can work out, it bends the light to make the pellet appear further back than it was at the first sensor, or further forward at the second, thus stretching the apparent time it takes to cross them, thus reporting a slower speed.
     
  6. Jon

    Jon Member

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    If that were the case and it didnt appear to move the exit sensor it would give higher readings dependant up on the rifle.

    99% sure the BFTA ones have always been affected by the light which should be equal on both sensors.

    The only cheap way to go is CED M2, infra red and battery in an enclosed box.
     

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