Riddle me this

Discussion in 'Steyr' started by RobF, Jan 7, 2016.

  1. RobF

    RobF Administrator Staff Member

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    We change the transfer port to a 4mm to increase flow... and it seems to work. But the hole it connects to in the cocking bolt is less than 4mm and never changes... :confused:
     
  2. fireblade2

    fireblade2 Master Yoda AA FT TEAM

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    The air flow is only constricted once instead of twice?
     
  3. handbylt

    handbylt New Member

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    Check out..BERNOULLI PRINCIPLE...relating to fluid and gas flow..it may help you to understand why:)
     
  4. RobF

    RobF Administrator Staff Member

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    Sure, the narrowing increases the speed... but why does that change where the restriction is or is that just a fluke?
     
  5. Tench

    Tench WHFTA World Champion 2016.

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    Shortening of the restricted length?
     
  6. RobF

    RobF Administrator Staff Member

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    yeh, could be... i hadn't really thought that the restriction would improve things, and that removing it made sense... i just had one of those "wait a minute..." moments...

    now where's that drill? :D
     
  7. dave croucher

    dave croucher FT, the sport where simple becomes complicated

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    It just does
     
  8. RobF

    RobF Administrator Staff Member

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    Thanks Dave. Your scientific prowess is infinite :lev:D
     
  9. AndyIoW

    AndyIoW Member

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    Note sure why but Held at the club changed the transfer port from a green to black as an experiment. He was getting some wild fluctuations at the muzzle with over +/- 30fps from a nominal 770fps.

    Once changed his average fps went to nearly 880 but with about +/-5fps variations. Taken down to 780 with the same 5fps variation.
     
  10. Lol Moore

    Lol Moore Banned

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    Length

    I think Tench has it - the length of a restriction to flow is just as important as its diameter.

    There are all sorts of things going in in relation to whether the flow is linear or turbulent, the thickness of the frictional barriers at the edges of the restriction, the turbulence set up in the transition from the transfer port fitting/O ring to the bolt, I would think the fluid dynamics at that point are extremely complex.

    All that said I have a spare bolt and may try a bigger hole myself, or maybe just profile the inlet of the hole first :D

    The springer boffins will be along soon as they have years of experience "fettling their holes" :D:D
     
  11. RobF

    RobF Administrator Staff Member

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    That could have been serendipity with it sealing better after being changed.
     
  12. hmangphilly

    hmangphilly The Doctor

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    they look smaller than they are



    [​IMG]

    [​IMG]
     
  13. RobF

    RobF Administrator Staff Member

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    Thats blown the thread then. Lol.
     
  14. blacklab

    blacklab Member

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    bolt

    how do we know that the hole in the bolt lines up with the transfer port, that could make a difference in the flow of air
     
  15. hmangphilly

    hmangphilly The Doctor

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    all you can do is fiddle with barrel position and transfer port height .

    a little chamfer on the hole in the bolt may help minor misalignment , but i wouldn't worry too hard about it .
    the 2 parts dont meet metal to metal , there will be a small void due to the o ring .

    the air flow properties are pretty pants if you think about it as the air has to turn 180 degrees in about 1/2 inch. with right angles every where
     
  16. blacklab

    blacklab Member

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    180 degree

    how much more efficient would the gun be if the blast of air was directly behind the pellet can,t think of any that are
     

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