Runnning Motors at WOT on the bench

[lohring]

If your motor is close to its max rpm when loaded then it will be over that when unloaded, that's when rotors laminations can come unglued and start to fall apart, especially cheaper made motors. I've had this happen with cheap motors and had it happen with a high end German motor, one blip to wot and "bang". Run it in the water where it's supposed to be run.

The unloaded rpm is the maximum the motor can run. It's Kv times the voltage. Loading the motor always lowers the rpm. I've seen motors seize when they threw a magnet even when under load in the water. The load varies tremendously on a running boat as the prop raises and lowers. Motors that you value probably shouldn't be run unloaded. However, they often can be without a problem. Under load they heat up and weaken the adhesive and wraps holding everything together. I think high rpm under load or high rpm on a motor that has been run hot is more likely to cause a problem.

Lohring Miller

[NativePaul]

It's Kv times the voltage. Loading the motor always lowers the rpm.

Unless your motor's KV is quoted loaded as some of the best motors are, in which case, unloading the motor raises the RPM.

[T.S.Davis]

I used to twist up to WOT on the bench because I liked the sound and I'm a child. Did that until I had a wire drive give out at the strut. Apparently the prop wasn't as balanced as I thought. It threw the prop and it hit me right in the throat. Could have killed me.

WOT on the bench is pointless.

[lohring]

Hi Lohring,

Is the a series of disc used as a brake?

Mike

Yes. The disks are braked by the eddy currents the magnets create. Heating is probably the main limit to power absorption, thus the number of disks. It's designed to absorb a lot more power than the P spec motor shown.

Lohring Miller

[Heaving Earth]

Try telling my wife this! We have a 4runner with over 250K and it's never had anything major done to it. She didn't let it warm up any before driving.

what are you trying to jinx yourself?