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Thread: Of 'Cocker Valves and Flow Restrictions

  1. #11
    Insider imped4now's Avatar
    Join Date
    Feb 2015
    I'd think those fins just provide extra area for pressure to work against, aiding in close force.

  2. #12
    Actually, i believe the fins help maintain placement so the stem, so that it does not wander and thus not seal fully against the valve body.

    edit:on second thought, it may help with the closing pressures. I do knownthat on the empire balance valves; they worked much better when there was a DIY (believe it was a spyder valve guide) fin used on them.
    Last edited by Nobody; 12-05-2017 at 06:51 AM.

  3. #13
    Join Date
    May 2012
    Quote Originally Posted by Menace View Post
    Again, thank you.

    Can you say a bit more about how those fins help with closing time?

    Do they create a kind of force differential in that they don't contribute to opening force when the poppet is sealed up, but add to closing force when the poppet is open?

    Just a guess, so do pardon if that's silly.
    This is my belief - they created a "drag" force only in flowing fluid

  4. #14
    That was my thinking.

    They work like a sail. When poppet is sealed up, there is no flow, and pressure is equalized on both sides of the fins. And because they aren't part of the sealing face they contribute nothing to the closing force.

    But when the poppet opens the pressure now works on that additional surface area, helping it to close faster.

    However, there has to be something in the fact that the fins touch the bore walls.

    The Bob Long Cyclone valve had a similar design, though I don't know if those brass fins touched the bore walls. That wouldn't be too good for the finish.

    The Palmer's valves, for instance, have a much larger than necessary cup seal head which should work in the same way, but at some point you get into serious flow restriction.

    I'm guessing that because the inlet port on the Tornado is so huge, it matters a lot more that the cup seal is perfectly square to it, as this would decrease the time necessary to fully seat it.

    I've got two RAT valves here, one a 1st gen, and the other a prototype 3rd gen, and both of them very clearly could benefit from stabilization. Honestly, in comparison to other valves I've seen, they look like they were designed not to seal up quickly without a lot of persuasion.

    Huge amount of stem wiggle in the valve body, both in the heavily used older one, and in the newer one that looks never to have been used.

  5. #15
    Join Date
    May 2012
    I haven't thought too much about stabilization in this implementation, though it's clearly important.

    "Stem Wiggle" seems like a fairly insane problem to have, though it's definitely a thing. I suppose that's one of the nice things about the shielded valve concept - it's naturally collimated and in double shear. Adding an o-ring to the stem is tricky business, since the hammer hits there - don't forget the fillets on the groove.

    I actually played around in the "leprechaun" project on mcarterbrown with a concept that uses the dynamic restriction (same principle as the eigenring active devolumizer I made in ~2008) to close more quickly. More generally I think the OG Matrix slambolt did something similar)

    It really lowered velocity, and we never really tuned it to the utmost, but the proof of concept at least is there. Were I to iterate on this I'd probably suggest a short but heavier mainspring, minimum 90 duro seal, and more valve lift to be as aggressive opening as possible. It's tricky in a pump system because you're constrained by static balances.
    "So you've done this before?"
    "Oh, hell no. But I think it's gonna work."

  6. #16
    Join Date
    Apr 2012
    Knoxville, TN
    There was a time when the Spyder cupseal had a thin metal guide in them to stablize them, to stop 'Stem wobble', and the AKA valve was designed to do it with the valve seal material, because that was a better sliding material. If you read the patent the purpose of the stems was stabilization.

    After that, the extra valve material did help close the valve by catching the air movement to help close the valve.

    I was going to play around with some of the moment stems on the Planet guns or otherwise to see if I could replicate that action there. Just a couple discs on the stem. I have it as an add on for one of my other bolt designs, to assist in closing.
    Josh Coray
    J4 Paintball
    Lead Design

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