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Thread: Hand Ergometer

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  1. 27-06-2013 #15
    irving2008's Avatar
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    Strength calcs: Calculate for input gear as worst case (Ref: Spur Gears)

    Input torque = power/revs = 90/6 = 15Nm, add 50% for safety = 22.5Nm
    Tangential force on tooth Ft = 2 * torque/PCD = 2 * 22.5/.01875 = 2400N

    Bending stress = K * Ft/(b * m * Y)
    K=velocity factor, estimated at 1.03
    b = face width = 6mm
    m = module = 1.25
    Y = Lewis Form Factor = from tables, for 15T 20deg gear = .289 @ tip .49 @ centre of tooth, use .289

    stress = 1.03 * 2400/( 6 * 1.25 * .289) = 1140MPa = ~165kPSI

    PLA = 500kPSI so should be OK!
    Last edited by irving2008; 27-06-2013 at 12:32 PM.
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