Planetary motors

Discussion in 'General Electronics Chat' started by Dritech, Mar 28, 2013.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    5
    Hi all,
    Do planetary geared motors rotate both directions? because I am seeing drawings indication an arrow to one side.
    Also, do Planetary motors lock like worm motors? Lets say for instance the motor will be used to rotate a pulley which will be used to lift a load using a rope. Will the load go down when the supply is turned off, or will the planetary gears prevent this (lock) ?

    Thanks in advance.
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,022
    3,236
    If the motor can rotate in both directions then so can the planetary output. Planetary gears rotate equally well in either direction.

    No, planetary gears don't lock like worm gears.
     
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  3. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Thanks for the reply crutschow .

    So basically I have to do some kind of braking system to hold the load right?
     
  4. crutschow

    Expert

    Mar 14, 2008
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    3,236
    That is correct if the load generates enough torque to back turn the motor through the gears.
     
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  5. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
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    Depending upon the planetary ratio, it may not take much of a brake on the motor end. Remember, the torque is multiplied (motor to output) by the gear set when the motor is driving and divided (output to motor) when the load becomes the drive.
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
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    That's true, but a "rope on a pulley" can have significant leverage and is one of the worst cases for backdriving. Likewise if it does start to move it will accelerate badly, anothe r worst case laod for backdriving. Even a worm drive can have issues with that type of load.
     
  7. Metalmann

    Active Member

    Dec 8, 2012
    700
    223


    Planetaries go/run in both directions, unless impeded by a stop mechanism.

    You can also use a one-way bearing, to hold position.
     
  8. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,015
    1,531
    Automatic transmissions in cars are a good example of this. Sprag clutches and one way rollers plus planetary gears.
     
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