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I am not an mechanical engineer and I have a question about this laboratory rocker (https://www.thingiverse.com/thing:2948680/files). As I wish to reduce the height of the Model_Base.stl by half, by how much should I short the Linkage.stl model height. I wish to learn more about this design and therefore where can I find more information/reading material about this type of mechanical movement.

Thanks a lot.

PS What is the proper mechanical term for the mechanism?

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This is a classic crank rocker linkage design problem. Any kinematics textbook covers this topic. Design of Machinery - Robert Norton, Theory of Machines and Mechanisms - Uicker and Pennock, Mechanism Design - Erdman and Sandor. My favorite is Kinematics and linkage design - Allen Hall pages 33-35 covers this exact problem.
A new CAD based method is recently published called pole and rotation angle constraints. See the book Planar Linkage Synthesis - Ron Zimmerman. www.prclinks.com

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If you reduce the height of the base by half, there is a specific value involved. I have not downloaded nor measured this model, but for argument's sake, I'll assign 120 mm for the existing height. Half of that is 60 mm, the length to be removed from the reciprocating linkage.

It is necessary to be concerned about interference between the rotating portion and the rocking panel. One must also expect that the electronics contained within will be moved outside, a somewhat trivial issue.

Calculations specific to this form of motion are based on the radius of the rotating portion, measured from the center of the linkage to the center of rotation. This is because at top dead center, the linkage has moved upwards as far as possible. At bottom dead center, it is in the lowest position.

This is a generality due to the motion of the platform, as it is an arc, but the difference in this case is going to be insignificant unless very precise measurements are required.

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  • $\begingroup$ Thanks for the comments. I do not care about the electronics at the moment but more on the mechanical parts calculation. Is there an equation set for this mechanism? $\endgroup$
    – alirazi
    Oct 6, 2023 at 10:01

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