### Author Topic: need a stepper motor  (Read 1705 times)

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#### dmehling

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• Posts: 90
##### need a stepper motor
« on: August 20, 2007, 02:40:46 PM »
I need a recommendation for a stepper motor that will be used to lift a small platform.  The platform will weigh about 15 pounds, and the stepper motor will use a threaded screw.  I have no idea how I would determine the amount of torque needed for lifting this platform.

#### jsmoker

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• Posts: 118
##### Re: need a stepper motor
« Reply #1 on: August 21, 2007, 03:11:23 PM »
Taking into account that loss of energy is NOT taken into account with this calculation (e.g. friction)

a screw is just a variation of a simple machine so the mechanical advantage (MA)= circumference of the screw over the pitch.  I don't know realistic numbers off the top of my head but say your MA is 15 so it would take 1 pound of force to lift the platform.  But obviously you're working with torque not force, but torque is just force x distance so the torque depends the diameter of nut.

Sorry, perhaps someone can give you some practical numbers from experience, but here's something to start with I guess, but really if you had a fine enough pitch (and little to no friction) you could lift the thing with the smallest of motors.