Torque transfer via bar - Mechanics

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  • Thread starter Slickepot
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Slickepot
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A friend of mine asked about this problem and I'm wondering if anyone has any advice or tips how to solve it.

1. The problem statement.
(picture attached)
Two bars L1 and L3, connected to two walls, can turn around their fixed wall positions. Torques in those points M1 and M3. The bars are connected via a bar (L2) and joints P and Q (full motion).
What is the connection between the torques around M1 and M3?

3. Attempt at a solution.
All my attempts have seemed unreasonable.
I believe M1 torque can be small to result in a big M3 torque when angle α is large.
Also believe M1 has to be huge compared to M3 when L2 is almost parallell to L3.

All ideas or suggestions how to approuch this problem is welcome. Any similar problems or links to reading material would be great.
Thanks
 
Attachments
  • Planar linkage diagram: bar L3 pivots at a fixed point on a horizontal wall at top right, bar L1 pivots at a fixed point on a vertical wall at lower right, and bar L2 joins them at joints P and Q, with torques M1 and M3 and angle α marked at Q.
    problem.jpg
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Discussion

I think you need more information on the geometry of the problem; enough information to derive the positions of all 4 joints. Assuming the force acting is gravity, you'll also need masses in there somewhere. Once you have that, diagram the forces acting, and you should be able to find the torque. I'm interested to see the solution though.
 

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