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Beam bending problem

  1. Nov 26, 2009 #1
    1. The problem statement, all variables and given/known data

    Hi there all,

    I am designing a pedal box for a vehicle, and its adjustment is does by removing some pit-pins and sliding the pedal box along a rail and reinserting the pins. I need to calculate the stresses in the pin given a 600N total load applied by the feet of the driver. The pin is of radius 3.5mm, and has a Youngs Modulus of 193GPa.


    That diagram basically shows what is happening after i have simplified the problem. The beam is not supported at the ends. The black part is the pin, or beam, and where the loads and reactions are are where the pin is in contact with the chassis/pedal box.

    2. Relevant equations

    I am trying to work through this website:


    but can not get any decent answers. I am not too sure what dimensions u, x and c are to be honest.

    I make the Moment of Inertia to be 1.18 x 10^-10 .
    3. The attempt at a solution

    Working through a mechanics book i get the ractant forces to be 300N, and a shear force diagram that goes 300N-0N--300N along the length of the beam, which i cant help but think is wrong. I was expecting a more complex outcome to be honest.

    Any help wold be much appreciated as this is making me feel very stupid!
  2. jcsd
  3. Nov 27, 2009 #2


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    Science Advisor
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    Gold Member

    TowlieUK, welcome to PF!
    c is the overhang distance 0.001 m; u is the distance between the support and the point of interest where you wish to calculate the stress, measured from the support toward the near free end.
    you were expecting too much, your shear force diagram is correct. What is the maximum bending stress in the pin?
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