Quote:
Originally Posted by 1683cadder
How do you do that?
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The speed/current/power vs. torque curves are shaped similarly for DC permanent magnet brush motors (i.e. all current FRC motors). Motors differ in the magnitudes of these quantities. You plot those curves (either experimentally or theoretically), and then decide what ranges you'd like your mechanism to operate in. Then you scale the curves using gear ratios (to multiply the torque by some factor). Look at the JVN DesignCalc spreadsheet (
here,
here and
here) and Andrew Kesic's motor curve spreadsheet (
here and
here) for examples.
1
If you want the motors to share the load proportionally to their maximum output power, then you want to gear them so that the speed vs. torque curves of all motors are superimposed (or that at least they're as close as possible within the relevant range). If you want motors to share unequally at different loads,
2 then you can orient those motor curves arbitrarily.
1 I have some incremental updates to these I've been meaning to complete and post. (Mostly updated motor lists for 2012, and minor formatting/functionality improvements.) One of these days....
2 That's a pretty rare requirement. Maybe one motor is a can motor with a fan that has a minimum effective speed, and you are willing to load it more at high speed, in order reduce its load when high torque is demanded (at low speed when cooling is ineffective).