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Thread: Torque

  1. #1
    Associate Engineer
    Join Date
    Aug 2013
    Location
    North Carolina
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    3

    Torque

    I am trying to calculate the torque required to rotate a mass around a shaft. See attached.

    20140519094434670.pdf

    m = 315 lbs.
    w = 10"
    h = 16"
    d = 9"
    r = .75"

    T = Iar (a is angular accel.) (r is

    I = I1+md2
    I = 1/12 mw2+ 1/3 mh2 + md2
    I = 2625 + 26880 + 25515 = 55020 lb-in2

    Mass rotates 90 deg in 3 sec.
    average speed = pi/2 * 1/3 = pi/6
    pi/6 = at
    a = pi/18 rad/s2

    T = 55020 * pi/18*.75

    T = 7202 in-lbs

    My biggest problem is calculating the angular acceleration (a). I know i did not do it correctly. THe mass rotates from rest (0 degrees) to 90 degrees in 3 seconds.

  2. #2
    Associate Engineer
    Join Date
    Aug 2013
    Location
    North Carolina
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    3
    PS.. I am trying to size a quarter turn actuator which is why i need the torque. I am trying determine if i can drive 3 of these sections off of (1) actuator.

    The mass is a load on a platform and the shaft will be rotating to dump the platform. I have multiple platforms in series. Therefore, my max torque will be the initial torque, since once it starts rotating the mass will continually drop. Once i have passed 45 deg gravity should assist.

  3. #3
    Administrator Kelly Bramble's Avatar
    Join Date
    Feb 2011
    Location
    Bold Springs, GA
    Posts
    1,955
    Check the following webpage and Calculator -->

    Mass Moment of Inertia Equations


    Mass Moment of Inertia Rectangular Block

  4. #4
    Senior Engineer
    Join Date
    Sep 2014
    Posts
    35
    The above ideas are very clear and fine regarding the torque. Thios is also beneficial in case off engeneering purposes.

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