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Want to find out the mass movement capability of my motor

  1. Feb 1, 2012 #1

    SOA

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    am not sure if i am asking it right, it appears to be very easy, but am un able to solve it...
    any help is highly appreciated..:)

    Ques: ihave a motor wuth these specs

    torque = 5 Nm
    no of revolution = 90 rpm
    radius of wheel mounted on motor shaft = 0.05 m

    i need to calculate the mass which this motor can drive????
     
  2. jcsd
  3. Feb 1, 2012 #2

    Simon Bridge

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    A constant torque of 5N turns the wheel at a constant 90rpm means there is friction in the system balancing it out. No net torque.
    But if you put a Newtonmeter on the rim and figure the force to stop it, then you also have the maximum weight it can hold.
     
  4. Feb 1, 2012 #3

    sophiecentaur

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    Does this motor have a gear box in it? 90rpm seems very slow for an off-load speed. What sort of motor is it?
     
  5. Feb 2, 2012 #4

    SOA

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    yea i will mount it on some wheel definitely but before that i want to get the idea of its capability...
     
  6. Feb 2, 2012 #5

    SOA

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    yea it is worm geared motor... mostly used in car windows.
     
  7. Feb 2, 2012 #6

    Simon Bridge

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    iirc there are important real-life restrictions - don't rl electric motors draw more current under load or something? I remember something about motors burning out.

    But doing stuff with motors is usually more about power than work.
    So you need to settle on something for a benchmark.

    Manufacturer usually has a clue or three too.

    A naive calculation would suggest to expect it to hold 10kg against gravity with the specs shown. I wouldn't bet on it though. The RPM given, if stamped on the motor, may be that under normal load (eg - lifting a window). Have you run it without yet?
     
  8. Feb 2, 2012 #7

    sophiecentaur

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    From the data, it looks as though the motor will produce a force of 100N at the periphery of the 0.05m wheel. That suggests it should lift 10kg if you use it as a winch, for instance.

    Torque = Force times radius
    so Force = Torque/ radius

    There is another important parameter and that is the useful Power output.
    The power out will be Torque times angular speed (in radians)
    That's 5 * 90*2π/60 = 47W
    If the motor is 50% efficient, that means a current draw of about 8A, when running on full spec load. Doesn't sound too far wrong for a chunky bit of car electrics.

    The motor should lift this 10kg at about 0.5m/s.

    Someone else might like to check these shirt cuff sums.

    [edit - well, at least Simon agrees with my 10kg figure. Ain't sums wonderful?

    and the bit about being careful not to overload is relevant too.]
     
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