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Looking for a part that can lock a spherical bearing.

  1. Aug 17, 2013 #1
    For context:
    I'm building a handle that needs to rotate in all directions.
    The handle will be placed inside the spherical bearing - and the bearing will allow it to rotate as it's required to.
    The handle will also need to be able to be locked in place at angles chosen by the user.
    Whatever it is that locks the bearing in place will need to be able to keep it in place against 500lbs of force.

    My best thoughts so far
    I'm considering a set screw. But I can't imagine the binding friction being enough to firmly secure the bearing in place. Also, because the bearing is spherical, a set screw with a flat tip probably wouldn't have full contact at certain angles (but I could be wrong)

    Questions
    Is there a way to lock a spherical bearing at a particular angle?
    Is there a part other than a spherical bearing that would provide the same function in this application that might be more appropriate?
     
  2. jcsd
  3. Aug 17, 2013 #2

    Baluncore

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    You understand what you want, but I can see too many interpretations in your problem description.

    Do you have a spherical roller bearing, or is it a ball joint that needs to be locked ?
    Is the handle completely inside the sphere? or does it stick out like an arm ?
    Is the 500 pound force acting axially?, as an axial torque? or on a long lever arm?
    Is the bearing surface required to survive significant movement when not clamped ?

    A ball joint without lubrication can be clamped by tightening the outer housing. A single screw would damage the surface of the ball. The size of the ball must be increased as much as possible as there will be very high shear forces where a 500 pound force arrives at a small spherical surface.

    Some ball joints are locked by twisting their handle which expands the ball in the fixed spherical socket.

    A better description of your geometry would help as there are many solutions to any possible situation.
     
  4. Aug 17, 2013 #3
    1. I looked around on the internet some more after posting the question, and a ball-joint is closer to what I'm looking for)
    2. The handle is inside the sphere completely.
    3. the force would be pushing against the handle on the inside.
    4. Significant movement: It needs to move freely and easily, but we're looking at about 1000 rotations/day, and they will be spread out over the course of the day.

    Do the ball joints you described have a name?

    Thanks for the help.
     
  5. Aug 17, 2013 #4

    Baluncore

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    Not that I know of.

    I am imagining a hollow sphere with a hole in it that you put your hand through. Across the inside of the sphere is a bar that is held by the hand. The orientation of that bar is adjustable and can be easily locked.

    I see a problem where the wrist passes through the hole in the spherical shell restricting movement, with possible injury.

    Is the 500 lb carried by the wrist in tension like the handle on a suitcase ?
    Or does someone hang by one arm from the handle ?
    If the wrist is in compression then why is a handle needed ?
    I still need more application information to make sense of this.
     
  6. Aug 19, 2013 #5
    What you are describing will be a mechanism not a bearing. No simple bearing will have been designed to be locked in various positions. You are looking to design a mechanism which uses bearings and something else in order to perform the requisite functions.
     
  7. Aug 19, 2013 #6

    Baluncore

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    I cannot help without some idea of the geometry.
    You have not communicated that clearly.
    If my guess is wrong then I cannot help.
     
  8. Aug 19, 2013 #7

    berkeman

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  9. Aug 19, 2013 #8

    Baluncore

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    Maybe. But if that was the case MichelKS could communicate it.

    By definition, a handle is held by a hand. You pull with your fingers, but push with your palm. The ball cannot be complete if you can get your hand inside it. The locking technique is dependent on push or pull and the degree of freedom required.

    There are too many open possibilities still to sensibly narrow the search tree. I am not going to list all 10 different ways of doing 10 different things, only to be told that I did not understand the question and that I should have considered an 11'th possibility.
     
  10. Aug 19, 2013 #9

    berkeman

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    Agreed. :smile:
     
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