KV / Gearing choices

[sleebus.jones]

I've got some thoughts on this, that aren't really backed up by any sort of real-world use, but as Scotty says, "ya canna change tha laws of phyziks!"

1. Higher voltage is good. In the real world, as electric motor horsepower goes up, so does the voltage. Why? That's so the amp draw of the motor doesn't become unmanagable, which would require huge wire gauges. The higher the voltage you run, the less current you need to do the same amount of work. This means less strain on your battery and ESC system. For instance:

2S liPo driving a 1000w motor:

watts/volts = amps

1000/7.4= 135 amps

3S LiPo driving a 1000w motor:

1000/11.1 = 90 amps

The benefits there are obvious. Same amount of work being done, but with 33% less amp draw. The more amps you draw, the more you are fighting the internal resistance of the wires/battery/motor/esc and your system is running less efficiently. Let the voltage do the work, rather than the amperage.

2. Lower speed motors don't have to fight as much frictional resistance. It's not hard to see that a motor spinning at 65,000 rpm is fighting much more frictional resistance than one at 40,000 rpm. Gearing up then puts that high speed load on the driveline, rather than the motor.

3. Here's one that'll probably start everyone arguing: the torque of a brushless motor is determined by its power delivery system, not the motor itself! For instance, if you take the Fiegao line of the same size motors, all can produce the exact same torque, regardless if it's a 6XL or a 10XL. If you do see torque differences, it's because your battery system isn't up to snuff with the current demands of the motor, not because of the motor. This becomes more and more apparent the smaller number motor you pick, because the amp draw goes up as the number goes down. Yes, this goes completely contrary to brushed motor thinking, but then, these aren't brushed motors, are they? :027:

Discuss! :)

Sleebus