Thread: Which motors should we use?
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Unread 23-06-2002, 23:03
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#0047 (ChiefDelphi)
  
Join Date: May 2001
Location: Pontiac, MI
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Power is all...
Posted by Joe Johnson at 1/16/2001 9:17 PM EST


Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.


In Reply to: Which motors should we use?
Posted by CArobot on 1/16/2001 6:14 PM EST:



It is my belief that at a minumum, a drive system
should be able to break the wheels free rather than
stall the motors.

This does not pick your motor, but it does pick the
lowest gear ratio you can used with any particular
motor (which really means it determines your top speed).

I would calculate what weight you expect to be put on
your drive wheels, multiply that by .5 or so as an
estimate of the coeficient of friction and then
multiply that by the radius of the wheels. This will
give you a toque needed to break the wheels free.

Divide this torque by the stall torque for the motor
multiplied by an estimate of the efficiency of the
drive train (for example .9 per spur gear stage, .9 per
chain stage, .3 for a work drive or a jack screw, etc.)

This number is the ratio your drive train will need.

Now calculate the free speed of you wheels. Is that
fast enough? If not you need a more powerful motor.

The most powerful motors in the kit are the drills (by
far) followed by the Fisher Price motors, the Globes,
the Power Sliding Door motors, etc.

See several of the white papers on motors on this web
site for more information on motors and power calculations.

Good Luck,

Joe J.

The



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