[apalrd]

The JVN excel calculator does not deal with this situation well.

The JVNcalc determines the 'supermotor' specs by:
-For speed, you input the design speed. There is no calculation of this.
-For torque, you input the gear ratios for each motor, and it adds the adjusted torques.
-For current, it adds them up.

This works fine if the adjusted free speed of all of the motors is close to the design speed, but if you deviate from this, then the free speed number is wrong, so you would incorrectly get more torque than you should.

Looking at the second link in my last post, moving from the yellow line to the red line will cause an increase in stall torque (which the simulator uses as the torque number) but a decrease in free speed - Since these torques are the sum of a CIM and adjusted RS-550, the CIM will overrun the RS-550 before 4500rpm, and at 4500rpm the negative torque produced by the RS550 and positive torque produced by the CIM total zero and you have your new free speed of the combined assembly (~4500 for that example). So while you would gain stall torque, you would lose free speed and when you adjusted your gearing appropriately, the result would be roughly the same. The JVN calc does not calculate free speed, so it does not show this. If you open the circuit on the motor that is being overrun at the point at which it starts being overrun (so instead of acting as a generator it does nothing), you end up with a piecewise torque curve with a higher free speed, but the accel simulator on the next two pages of the spreadsheet won't simulate the piecewise torque curve correctly either.

Increasing motor load also increases electrical load. There's a point at which adding more motors hurts more than it helps, I believe 6 motors is right around that point (so adding more than 6 is bad, adding 6 is good), but the benefits taper off after 4 (the improvement from 2 to 4 motors is huge, the improvement from 4 to 6 is not nearly as big).