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Mechanical System for Lifting and Lowering Weight

  1. Dec 16, 2011 #1
    Hi, I am looking for a 115 VAC motor (able to be plugged into an ordinary power outlet) that is capable of raising and lowering a load of up to 150 lbs. (attached to a cable and a pulley) at the speed of 6 inches per second. I want the speed to remain constant even if the load changes. How can I turn this into motor specifications? Also, given the low speed, will I need to use a gearbox with this motor and if so what could I use? Also anyone who could help me out in selecting/recommending parts for this system I would be eternally grateful. Thanks for any help.
     
  2. jcsd
  3. Dec 16, 2011 #2
    OK, here are a few starters:

    Compute the motor shaft power:

    Power = weight * g * vel

    weight = 150 lb
    g = acceleration due to gravity 9.81 m//s^2
    vel = velocity = 6 inch / sec

    watch your units.

    Now if you put a pulley of radius rp on the shaft, the angular speed is:

    angular speed pulley = vel / rp.

    If the motor nominal speed is: rpm_motor, the gear reduction is:

    gear reduction = rpm_motor / angular speed pulley.

    I would also recommend a small, low end VFD so you can tune the speed.
     
  4. Dec 18, 2011 #3

    Danger

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    Gold Member

    Good answer, Edge.
    Just to simplify things, though... any normal 115VAC motor that I've seen runs at 1750rpm. That should eliminate one variable.
     
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