More or less amps?

[coolhandcountry]

Tahnks brian. I wanted to know if a motor like the xl1200 and xl12 turn both spin about 1200 kv give or take 51. :D One motor is rated at 55 amp the other at 26. I was wonder if they would produce the same amount of torque on the same amount of amps or would the xl12turn produce motor for it has more rotor area. If that is the case I should possible get more run time out the xl12turn than xl1200.
By looking at what you explained. If i go up on voltage the watts will go up and the torque as well. So If I pack a 8s lipo on instead of 6s with a lower kv( higher resistance) I can get the sam torque with the same rpm with lower amp draw. Am I on the right track?

[BrianG]

CHC, I'm not really sure about the motors themselves, but don't forget that the watts (or HP) you get is a function of torque and motor speed. You could probably plot a horsepower and torque curve vs motor speed for each motor based on the formulas I supplied. It won't be "exact" because of some losses, but it should give you a rough idea.

You'll need a voltmeter and a high current (~100A) meter, or I suppose you could use a watt meter. If a watt meter is unavailable to you, measure the battery voltage and current draw for different battery voltages. From that, calculate wattage. You know a motor has a kv rating, so you can calculate motor rpm based on the voltage you are using. Once you know the power and rpm, you can calculate torque using the second formula from my previous post. You can do this for different cells counts from 6v up to whatever you want to get a plot. Do this for both motors.

Note: Since you are measuring input power, there will be some inaccuracy because of controller inefficiency, but as long as you use the same controller for each motor, the inaccuracy will at least be consistent. Also, you'll have to provide a consistent load for each motor.

Oh, and don't forget that torque is ft-lbs. You can convert that to oz-in if you want.

Once you get the plots done, it should be intersting to see if the sweet spot is truly around 35k-40k rpm.