Globe gear box

[Joe Johnson]

Originally Posted by T134guy

...I have matched the rpm of the 2 to within 3%(about 186rpm) ... ...-Pat

Matching RPM this close is of almost no benefit.

Know that matching RPM for all load conditions is impossible unless you have motors that are the exact same power.

For all other motor combinations, you will match the motors at exactly ONE speed/load point.

You have choosen to match the free speeds (free speed is the zero load torque point). You may have just as well chosen to match the speeds at some other point (for example at the 1/2 stall torque point -- a.k.a. the peak power condition -- or at the peak efficiency point or even at 75.432% of stall point).

Which point you chose matters, but not as much as many folks seem to think. Also, don't forget that you have some freedom to modify behaviours of your motors by giving them different PWM values -- in this way you CAN have matching RPM over a wide range of load torques. But, even this has some limitations (software cannot make motors have more power than they have).

There are some good whitepapers on this topic.

Joe J.

P.S. I have concerns about the idea of adding a 50 Watt Globe motor to an almost 400 Watt Bosch drill motor. It just seems like a lot of bother for not very much benefit... ...but that is just me perhaps... ...Of late, I have given up building my own custom gearboxes, swerve drive, shift on the fly, and any number of other complexities...

...perhaps I should start a 12 step program for multi-motor, shift on the fly, steerable drivetrain addicts:
Step 1 We admitted we were powerless over fancy FIRST drivetrains - that our FIRST designs have become unmanageable
Step 2...