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Flat rubber belts and pulleys

Discussion in 'Electronic Repair' started by N Cook, Mar 5, 2007.

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  1. N Cook

    N Cook Guest

    Can someone explain to me how bulbous/baluster pulleys centralise a belt.
    And why the belt does not slip off parallel sided , ie non bulbous flywheels
    with usually no flange on one side. The chances of grime or shine on one
    side or the other of belt or pulley should easily lead to a belt comming off
    such flywheels , shouldn't it ?
     
  2. Tim

    Tim Guest

    It's the crown that is on the pulley. The belt will always climb to the
    highest point and stay there. It's the same concept that kept those big
    flapping belts on old equipment like you see on the Walton's saw mill.

    - Tim -
     
  3. davidlaska

    davidlaska Guest

    When Mercedez change to a new body style in 1981, we were in a 380sel
    and popped off a couple v belts on a dirt road.
     
  4. Guest

    The centre fattest part of the bulbousness travels faster, because its
    wider, thus pulls the belt more than at the ouer edges of the drive
    wheel. Hence the belt is pulled towards the fatter wider centre.

    As for whats-it-called wheels, the slave ones, the belt position on
    them depends on the driving wheel, which feeds the relatively slack
    belt to the secondary wheel.

    grime is distributed fairly evenly in practice. But there is normally
    no slippage occurring between belt and drivewheel, so friction level
    has no effect. You'd need a very dirty and very slack belt for this to
    occur.


    NT
     
  5. N Cook

    N Cook Guest

    I'm surprised they only seem to fall off if the belt is perished or someone
    meddling inside the mechanism or as a result of some fault or jam.
     
  6. I worked on old belt driven VTR's. The speed of the
    heads was controlled by a magnetic brake. As the brake
    acted, the belt would creep off center of the pulleys
    to maintain the correct size ratio for the new speed.
     
  7. Sofie

    Sofie Guest

    The belt will go to the highest point is where the most tension is.... and
    the most grip.... the belt will not go where there is no tension or little
    grip.
     
  8. Why then not simply have two flat pulleys
    the correct distance apart for optimum tension.
    Edges would prevent the belt from slipping off.
    I've seen this in some audio tape decks that are
    fixed speed.
     
  9. Edges would cause wear.
     
  10. Guest

    Lionel:
    If they were truely FLAT pullys with EDGES, the belt would bump the
    edges and immediately climb off the pully.
    If you look closely at the FLAT pully with EDGES on your audio tape
    deck that you mentioned, the motor pully surface that the belt rides
    on is CONVEX so the belt stays "high" centered and does not bump the
    edges.....
    I hope that this clarifies things for you.

    - - - - - - -
     
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