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Vibration proof hinge and lock

  1. Jan 4, 2016 #1
    Hi All.

    I am stuck in a problem.
    Please check the image attached.
    It's part of a foldable mechanism of a quad copter arm.
    The red part is fixed to the body, the grey part is fixed to arms. The transparent part is a threaded collar/sleeve.
    The yellow part is a stopper. The hinge is a connecting rod between the grey and red part, not shown here.
    The red part has external thread on which the yellow stopper mates.
    The yellow part acts as a stopper to the transparent sleeve so that the sleeve doesn't come out. The sleeve gets lockedin between stopper and the red side.
    The transparent sleeve also has internal thread which can be engaged with the grey part.
    When the mechanism is in lock position, the transparent sleeve is engaged with threads on grey part and is also in contact with the red side through stressed contact with the yellow stopper (there is a flange on the transparent sleeve).
    Hope the description is clear enough.
    Now my concerns:
    There will be vibration in the mechanism (motor and prop wash vibrations causing vibrations in the arm).
    My concern is if due to vibrations mechanism may come off (threads may get disengaged). This can be sorted by having a very fine pitch. Secondly I can add a spring/lock washer between sleeve and stopper.

    Another concern is the radial fitment between the transparent sleeve and the yellow stopper. There will be minor gaps (even if they are at micron level) and this will leave the mechanism a bit unconstrained , hence vibration.

    Solution:
    Line the stopper with rubber, such that the transparent sleeve is force to slide over the stopper.
    My problem is what type of rubber should I use, too hard and it will be difficult to slide over. Too soft and the mechanism will not have sufficient stiffness.
    Beside the transparent sleeve will have threading in the inside which will in time "eat" the rubber out.

    Any other ideas to solve this problem? I have also looked at other locking mechanisms (one very similar to
     

    Attached Files:

  2. jcsd
  3. Jan 4, 2016 #2

    JBA

    User Avatar

    Another solution to your clearance problem might be to make the flange to sleeve contact face cone shaped rather than flat.
     
  4. Jan 4, 2016 #3
    That's exactly what I was thinking.
    Now to just figure out how to add some spring action in it
     
  5. Jan 5, 2016 #4

    JBA

    User Avatar

    How much spring action is needed and what is its primary purpose?

    If it is only to make the joint more secure, you might consider 3 or 4 evenly spaced longitudinal slots in the sleeve section surrounding the flange.

    Another joint option you might consider is to extend a tapered end on the red part beyond the flange face and machine an internal mating taper into the end of the gray mating part.. By this method you can have a very shallow and long mating taper angle to align and lock the two components together.
     
  6. Jan 11, 2016 #5
    @JBA
    Thanks for the reply
    It's for a foldable arm of a quadcopter.

    I found out rough costing for the above parts and it seems I can't really afford it. Hence I am changing my design
     
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