cim motor power question

[Kit Gerhart]

Originally Posted by Jeffrafa

Based on the motor spreadsheet the CIM's have a peak output power of 343 watts each - this means 3 of them theoretically will give you roughly 1.38 HP as your peak. This multiplied through your gear ratio will put you at about 4.14 HP - leaving you with a decent advantage over the " 1 HP (3 peak)" go kart motors you are vs.
Jeff

The CIM motors have a peak power of 337 watts which is available at roughly half the no-load rpm, 2655 according to the spec sheet. That would be roughly 1.37 hp for three of them. Gearing does not create horsepower. It only trades force for speed and vice versa. The specified peak power of 337w/motor is, in fact, the actual peak power if the supply voltage is the specified 12 volts. Loaded to peak power rpm, each motor pulls 68 amps.

To maximize top speed of your vehicle, you need to have gearing that places top speed at the peak power rpm of the motor(s). This can be determined with lots of fancy calculations involving air drag, power loss in gears and bearings, etc. For your purposes, assuming you have a battery that can provide 68x3 or 204 amps for a while (and a way to control it--are you going to use Victors?) you can just gear for 18mph at 2655 rpm and see if you go at least 18mph. You won't want to "full throttle" the motors from a standing start because you would be pulling LOTS OF CURRENT for an extended period of time which the motors and speed controls won't like, and which the battery probably can't provide anyway. My gut feeling is that, with reasonably efficient gearing and proper electrical control of the motors, you should be able to go 18mph with your three CIM's as long as climbing hills isn't involved. Unless you can get that speed with "lower" gearing that allows you to run the motors faster than the peak power rpm, you won't be able to do it for a long time, because the motors will get hot and the battery will die quickly.

If you are using chains as part of your power train and you can easily adjust gearing with a single sprocket change, I'd start out with gearing that would provide 18mph at the "normal load" rpm of 4320. At that rpm, the motor draws 27 amps and can, presumably, be run continuously.

Good luck, and let us know how this project goes.