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V-Belt Drives & coefficient of friction

  1. Sep 28, 2015 #1
    1. The problem statement, all variables and given/known data

    1. A pulley 150 mm diameter is driven directly by an electric motor at 250 revs min–1. A V-belt is used to transmit power from this pulley to a second pulley 400 mm diameter against a load of 200 Nm.

    The distance between the centre of the pulleys is 600 mm, the included angle of the pulley groove = 40°, the coefficient of friction between the belt and pulley is 0.4 and the ultimate strength of the belt is 8 kN.

    What would be the effect of the following factors on the maximum power which can be transmitted (give reasons for your answer):

    (i) increasing the coefficient of friction

    (ii) increasing the included angle of the pulley groove.

    2. Relevant equations

    F1 / F2 = eµθ/ sinα

    3. The attempt at a solution

    Increasing the coefficient of friction would increase the power up to a certain point. graph 1 shows this. however i'm having some trouble explaining why this is.


    Increasing the included angle of the pulley groove will have the effect of decreasing the power. again i have a graph which shows this, but cannot really explain why.


    can anyone advise?
  2. jcsd
  3. Sep 28, 2015 #2


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    What's coeff. of friction as a function of angle?
  4. Oct 1, 2015 #3
    not really sure, would that be F1 / F2 = eµθ/ sinα

    but solved for sinα?
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