combined free speed of 3 motors

[Ether]

Originally Posted by James Kuszmaul

However, using all that single motor math will cause you to result in suboptimal results (if you attempt to optimize in any way, beyond just modelling the system).

I'm having trouble extracting an interpretation of the above. Could you explain what you mean? Perhaps give an example?

Also, has anyone gone through the proof that you can validly treat the two motors as one, given that you input the same voltage?

I thought that's what I did in the attachment to the original post. At what point in the derivation do you disagree?

To be clear, the derivation assumes the motors will be used to drive a load (like a drivetrain or heavy arm for example) with a reflected inertia much larger than the rotor inertia, so the dynamic contribution of the rotor inertia can be ignored.