# Fisher and Paykel motors top speed vs torque.

#### neorules33

Joined Apr 9, 2009
8
OK, I know the Fisher Paykel 42 pole motors are only supposed to spin 1100-1300 Rpm max due to the rotor design (its plastic).
I intend to make a solid steel back ring and bearing plate similar to an automotive brake drum only lighter using high speed bearings.

Right now the motor has 42 poles and it will have 56 Neodymium magnets.

Based on the outside diameter of approx 11 with and air gap diameter of 9.75 inches how would I calculate the max speed and max torque assuming a powerful brushless controller running at 24v, 48v, and 72v? I only mention the outside diameter as I am going to feed the values into a KE calculator later.

The values I have found online is 1295 feet or 23 gauge wire at approximately 30 ohms measured between two phases when wired in the wye configuration.

If a motor of this type has a torque of 30nm (just a number out of the air) and I stack two staters and rotors parallel would that increase my torque by a factor of 2?

I am just trying to see if the windings with a proper rotor ran up to 48 volts or even 72 volts would provide any appreciable torque and RPM.
I am replacing two 3" mag motors with neodynium magnets that is rated at 1500 oz-in (10nm?) with a unloaded RPM of 5700
assuming in parallel (geared parallel to prevent slippage of one motor) the torque would be 20nm with the same rpm?

Thanks JC

Joined Jul 18, 2013
23,933
For motors of that diameter balance is absolutely critical, especially if you are aiming at 5000rpm+.
Max.