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Thread: Cocker Ram force

  1. #1

    Cocker Ram force

    Hello Everyone

    Just working on a personal project and I was wondering if anyone knew the average force that a cocker ram produces on its return stroke?

    Thanks in advance!

  2. #2
    What ram and what pressure?

    Pretty easy calculation once you decide a pressure as P=F/A

    Worked out the resultant surface area of the ram (remember to remove the cross sectional area of the shaft) and decide on what pressure you are using and it will give you an answer

  3. #3
    Insider PBSteve's Avatar
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    To add to what Simon said, it depends on a lot of things.

    You need enough force to overcome the mainspring (if you're not using an MQ) and reliably re-cock the marker with the IVG adjusted to hit your desired velocity. So how much force you need depends on your mainspring, which depends on your valvespring and valve selections.

    Aaaaand this is why you either love or hate autocockers :P
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  4. #4
    wow....... well looks like I'm going to be busting out the pencil and paper for this one. I was just asking because me and a local shop owner hatched a plan for a anti-chop bolt, and I thought varying paint would be the biggest calculation problem :$

  5. #5
    You trying to determine the spring rate for a sprung bolt? pbSteve is probably thinking something different because the hammer that rides in the lower tube (with the springs) has nothing to do with the ram forces on a cocker. The ram has a fixed area which is pretty easy to determine by taking one apart. Then you'd have to determine your LPR. That is the ~force, however you do have a frictional loss take-off to the effective rate at the bolt face.

    In reality look at the punkworks data for the force needed to break a shell. IIRC, it was somewhere around 30psi. Make your spring yield lower than the average shell yield and you'll be fine.

    Also, if it were me I'd prefer to have the parts coupled to reduce to possibility of any oscillation. I'd use a magnet probably with a very light spring rate (just enough to reset the magnet).

  6. #6
    JAM bolt basically.

    they work well in my experience, not sure why they never took off. they do lower efficiency a bit, and arnt the best for super fragile paint, but they work. a breakaway magnet instead of a spring would have been a better design.
    Last edited by cockerpunk; 02-12-2014 at 01:45 PM.
    social conservatism: the mortal fear that someone, somewhere, might be having fun.

  7. #7
    Thats actually exactly what I was trying to do, the shop owner who I was working working with is old school guy who's been playing since the 80's and is a cocker fanatic and he built himself one back in the day with just some parts from his bin, we where looking to refine it and make some for ourselves and maybe sell a couple to recoup costs. I definatly like the magnet idea much more though with just the spring for a reset. My largest fear on the sprung design was oscillation. But one thing I liked about the sprung design though is you had more adjustment for different paint (just change the spring). How could this be accomplished with a magnet? Could you just make an adjustment on distances? Thanks for all of the help guys!

  8. #8
    Quote Originally Posted by cockerpunk View Post
    JAM bolt basically.

    they work well in my experience, not sure why they never took off. they do lower efficiency a bit, and arnt the best for super fragile paint, but they work. a breakaway magnet instead of a spring would have been a better design.
    Have you put one under the highspeed camera? I suspect if you do you will see why they are not efficient.

    I did a bunch of testing on this concept with BT guns and found that the spring rate to avoid breaks and to not get blown open causing blow back and breaks from that is a very fine line, if it's possible...

    We almost always got the bolt being blown back and blowback issues.

    I ended up scrapping the concept because it didn't work reliably enough otherwise it would be in every rental gun KEE sold...

  9. #9
    Quote Originally Posted by Simon View Post
    Have you put one under the highspeed camera? I suspect if you do you will see why they are not efficient.

    I did a bunch of testing on this concept with BT guns and found that the spring rate to avoid breaks and to not get blown open causing blow back and breaks from that is a very fine line, if it's possible...

    We almost always got the bolt being blown back and blowback issues.

    I ended up scrapping the concept because it didn't work reliably enough otherwise it would be in every rental gun KEE sold...
    i have, and yes, that is why

    this is why a magnetic solution might be better, high force to move it a small amount, low force to move it a long amount. vs low force to blow it open, like a spring. and you hope that impulse would be low enough on the chop situation that it wouldn't break the ball.

    idk .. .the JAM in my angle works great, except that it does use more air.
    Last edited by cockerpunk; 02-12-2014 at 03:08 PM.
    social conservatism: the mortal fear that someone, somewhere, might be having fun.

  10. #10
    The issue of blowback is pretty easy to solve. If you create a piston on the moving section and drill a small hole down the center of the bolt, then you can pneumatically lock it for firing.

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