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  • Mechanical linkage project ideas

    Discussion in 'The main mechanical design forum' started by johnsy123, Mar 31, 2014.

    1. johnsy123

      johnsy123 New Member

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      I have to design a mechanical linkage system that traces over a semi circle object. I have an idea of a design but i am not sure if it will work. Can i get some feedback?

      Rough drawing attached.

      [​IMG][/URL][/IMG]
       
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    3. bdeuell

      bdeuell Member

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      I'm not sure what you are trying to achieve. You say trace which to me implies you want the surface to drive the movement but then you have motors driving both the joints in your design. What is the objective here?
       
    4. johnsy123

      johnsy123 New Member

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      So where should i put my motors if i was to use this mechanical set up? Would there be only one on the remaining joint? So no motor on the ground...
       
    5. johnsy123

      johnsy123 New Member

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      Well i want the links to transmit a movement to the tracer that allows it to trace over a semi circle object back and forth.
      Where would i have to put motors on this linkage setup to achieve this?
       
    6. bdeuell

      bdeuell Member

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      Here is a vary mathematical approach to the problem. You need two degrees of freedom in your mechanism to allow the tracer to follow the surface that varies in two dimensions. If you want to force the tracer along this surface you would then drive one of the degrees of freedom with a motor. The second degree of freedom will be a function of the two inputs, the motor and the surface. You can think of the surface as a mathematical function where the motor position is the independent variable and the tracer is the dependent variable. I use the term degrees of freedom because it could be a sliding or rotary joint.

      Now as far as the design of the mechanism goes you have not provided much information about what function tracing the surface is intended to serve but i can provide a few tips. First off for the kinematics to function well you will want the motion path driven by the motor to be as parallel to the surface as possible this will drive the tracer along the surface most efficiently. You will want the free motion path of the tracer to be as perpendicular to the surface as possible and it may be desirable to drive the motor in one direction to prevent jamming of the mechanism...depending on design. The reason for selecting the motion paths in these general orientations is to maximize the ability for the mechanism to transmit the torque/forces to the intended motion efficiently minimizing loads within the structure and the required forces to make the mechanism function..

      I might suggest placing a motor as close to the center point of your semicircular surface. from there an arm would extend out a little past the radius of your surface and a second link would freely pivot on that point. The end of the second link would be the tracer (a roller might be desired to minimize friction). If a spring is required to keep the tracer against the surface I would place it between the first link (the arm) and the second link.

      These are just some rough ideas, I do not have a full understanding of your objective so my suggestions may or may not apply.
       

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