# Torque ,RPM, AMP Draw & Car Speed



## DavidDymaxion (Dec 1, 2008)

It can be a complicated thing. You are right, in general the bigger a motor the more efficient it is... but it is also heavier and more expensive. Usually 1 larger motor is more efficient than 2 smaller ones. However, electric motors are pretty efficient, so you aren't paying much penalty by going to 2 motors.

There is also a fundamental physics thing going on. Electric motors work by changing flux, so that pushes the design in the faster spinning direction. You'll notice many electric motors are geared, instead of using a larger, slower turning motor without gears. An example is car starters. My old direct drive car starter was about as big as a 2 liter bottle. My racing starter is geared, and the electric motor part is only about 1/2 the length and 1/2 the diameter of the old motor! Even so, it turns the motor over significantly faster.


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## Efiero (Feb 7, 2009)

yes the gearing in the mini starter brings the drive rpm down but it multiplys the torque so you are geting more torque per amp drawn large motor also have an earler rpm limit due to weight centrfugal force smaller lighter will rev quicker and higher. Correct me if i am wrong but i thought that if you run 2 motors in series that the torque doubles but rpm is cut in half so you have to double the voltage to get the rpm back up and as you add motors in series the torque go's up due to adding them together but you must add the voltage due to it gets devided betwen the motors. one last ? is ther a rpm limiter for motors so if you just wanted to run it a a constant 5000 rpm it would do it even with like 300 volts hooked up


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