How Can I Prevent Vibration-Induced Disengagement in a Quadcopter Arm Mechanism?

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Discussion Overview

The discussion revolves around preventing vibration-induced disengagement in a quadcopter arm mechanism. Participants explore various design considerations and potential solutions related to the locking mechanism of a foldable arm, focusing on the effects of vibrations from motors and prop wash.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes a mechanism involving a transparent sleeve, a stopper, and threaded connections, expressing concern about vibrations causing disengagement.
  • Another participant suggests making the contact face of the flange cone-shaped to address clearance issues.
  • A third participant agrees with the cone-shaped idea and raises the need for spring action in the design.
  • Further suggestions include adding longitudinal slots in the sleeve to enhance security and considering a tapered joint design for better alignment and locking.
  • One participant mentions budget constraints affecting the feasibility of proposed solutions, prompting a redesign of the mechanism.

Areas of Agreement / Disagreement

Participants present multiple competing views on how to address the vibration issue, with no consensus reached on a single solution. Various design modifications are proposed, but the discussion remains unresolved regarding the best approach.

Contextual Notes

Participants express uncertainty about the appropriate type of rubber for the stopper, highlighting the need for a balance between stiffness and ease of movement. There are also unresolved considerations regarding the effectiveness of proposed modifications in mitigating vibration effects.

RKD89
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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
 

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