Which motor is better?

[Joe Johnson]

Originally Posted by Biff

Just a side note, The torque at stall on the mini bike motor is almost twice that of the small cim. If you want to keep it simple and not shift you might consider that. And if you want it all Check out the Andy mark conversion kit to run one small cim and the large cim out of the kit transmissions.

Yes it is true that the FP CIM has 66% more stall torque than the smaller CIM, but the Smaller CIM has 97% more free speed.

Stall torque and free speed are accidents of birth. You can always trade more of one for less of the other (by gear ratios).

The Peak Power (=Tstall*Wfree/4) is your immutible figure of merit for a motor size.

For example, I can put an extra 1.66:1 gear ratio on the smaller CIM and get 1.66X the stall torque which will match the FP CIM's stall torque. BUT, this reduced smaller CIM will be running 25% faster than the FP CIM loaded to the same torque.

I like the FP CIMs, they are nice motors that will probably run nice and cool even when abused (as they surely will be), but they have 25% less power than the smaller CIMs.

Joe J.