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Thread: High failure rate of PMR bolts

  1. #31
    the omens feed system doesnt actually function like the deftek.
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  2. #32
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    I know how the omen feed system works.

  3. #33
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    Quote Originally Posted by cockerpunk View Post
    the OG deftek was the automag powerfeed.

    also jack, confirm or deny, the deftek was because someone missed a mm somewhere in the CAD/CAM in the 05 ....

    Deny. After spending many many MANY hours trying to remove ball breech bounce from e-cockers, it was a primary design consideration when it came to developing my own gun. It's simple and effective and adds zero production/manufacturing cost.

    Interestingly fact: our patent was denied on the deftek because of the Automag Powerfeed.
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  4. #34
    Quote Originally Posted by Jack Wood View Post
    Deny. After spending many many MANY hours trying to remove ball breech bounce from e-cockers, it was a primary design consideration when it came to developing my own gun. It's simple and effective and adds zero production/manufacturing cost.

    Interestingly fact: our patent was denied on the deftek because of the Automag Powerfeed.
    makes sense.

    ball breach bounce is a bitch. im surprised more guns don't use similar systems.
    social conservatism: the mortal fear that someone, somewhere, might be having fun.

  5. #35
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    Quote Originally Posted by Lurker27 View Post
    In the case of the gamma core, I'm guessing you increased the orifice linking the main chamber to the bolt front to eliminate oscillation/bounce.
    Quote Originally Posted by ironyusa View Post
    Increasing that hole seems the most reliable and predictable way of doing it. It seems to me to be the most logical. What would be the other 2 ways?
    You're both assuming the primary cause of the issue was residual/increased pressure in front of the bolt sail, I'm not convinced. If it really was as simple as making the hole to the bolt front a little larger fine, but I don't think the bolt is creating much of an increase in pressure in front of the sail just by geometry considerations. The ID in back is very large. Also worth noting the "venturi", which will give the bolt a forward bias at the cost of flow.

    At any rate I seriously doubt it's the issue with the matrix, which is venting through a rather large valve to atmosphere, and would never exceed LPR pressure.
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  6. #36
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    Depending on the geometry ahead of the sail and the exhaust/communication path into/out of that area and the bolt speed profile you can see massive spikes in pressure ahead of the sail. I'll see if I can host some transducer traces demonstrating it.
    Dear boy, I work at Planet Eclipse, don't you know..

  7. #37
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    OK, just look at the DARK blue trace and the RED trace.

    First of all, this is off a bolt system that didn't make production, but the bolt drive is similar to the Gamma Core. The front of the bolt is linked to a solenoid though, rather than to the valve chamber. That is the blue trace. Red trace is valve chamber.

    You can see the blue trace spike to way above its holding pressure when the bolt hits the second phase acceleration as the valve chamber opens up to the back of the bolt. You can then see the bolt bouncing back onto the main seal after the main valve opens, causing the valve chamber to spike again, then re-open and complete the dump. The combination of higher than expected pressure in front of the sail and the blowback on the face of the bolt push the bolt back onto the main seal.
    Dear boy, I work at Planet Eclipse, don't you know..

  8. #38
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    Jack, you're the man. Thanks for sharing!

    That's actually not the physics I was thinking of. (Mea culpa - I was wrong). There's a tiny uptick at the very end of bolt stroke, but not anything like what would be the primary cause of bolt bounce. Well, depends on transducer position I guess.

    The bolt compressing the air in front of the sail isn't spiking as I thought - it reaches a steady value described by the bolt velocity, bolt geometry,and restriction orifice. (The volumetric flow from the pneumatic sear is sail area * velocity).

    This plot has me wondering about those blowback forces - we obviously use them like crazy in the Paragon, but in our devotion to flow perfection never really considered trying to tame bolt oscillation by adding a venturi style face.

    Also fun on this trace - you can see the bolt movement in the chamber trace as the travel adds volume. We've used that to measure and tune bolt forward speed with our more shoestring instrumentation.

  9. #39
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    Actually the green trace is a corrected value. So you can see how high the pressure in front of the sail gets in relation to supply/valve pressure.

    Correct. The spike isn't a spike as such. Rather it shows that a pneumatic sear doesn't decay as many would imagine. The pressure in front of the sail is considerable, and a definite contributing factor in potential bolt oscillations and valve dynamics.

    And yes, you can tell an awful lot from just the valve chamber trace. Great piece of kit to have. That and a high speed camera.
    Dear boy, I work at Planet Eclipse, don't you know..

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