RC-Monster Forums - View Single Post

BrianG · 09:52 PM

Torque is force. Horsepower is the rate of torque ("time" is a factor here).

Horsepower can also be expressed in watts. Voltage generates an amount of current flow across a given resistance. The product of voltage and current generates a certain wattage. So, for a given voltage and resistance, the current will be X. If you double the voltage on the same resistance, you double the current, which quadruples the wattage. So, if you have a motor that pulls 30A on 14.4v, you know it will pull more current with higher voltage, and less current at lower voltage. We are assuming that resistance is constant here, but BL motors essentially run on PWM AC so you have to take inductive reactance into account, but to make things simpler (if a little inaccurate) we don't usually worry about it.

To find HP, you can use the following equation:

HP=( engine_speed * engine_torque) / 5252

Engine speed is in rpm.
Engine torque is in foot-pounds.

Since you know the HP rating of a motor (watts) depending on how many cells you use, you can figure out torque by messing with the equation to get:

engine_torque = ( HP * 5252 ) / engine_speed

That's how I see it anyway...

	(#2)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	06.23.2006, 09:48 PM Torque is force. Horsepower is the rate of torque ("time" is a factor here). Horsepower can also be expressed in watts. Voltage generates an amount of current flow across a given resistance. The product of voltage and current generates a certain wattage. So, for a given voltage and resistance, the current will be X. If you double the voltage on the same resistance, you double the current, which quadruples the wattage. So, if you have a motor that pulls 30A on 14.4v, you know it will pull more current with higher voltage, and less current at lower voltage. We are assuming that resistance is constant here, but BL motors essentially run on PWM AC so you have to take inductive reactance into account, but to make things simpler (if a little inaccurate) we don't usually worry about it. To find HP, you can use the following equation: HP=( engine_speed * engine_torque) / 5252 Engine speed is in rpm. Engine torque is in foot-pounds. Since you know the HP rating of a motor (watts) depending on how many cells you use, you can figure out torque by messing with the equation to get: engine_torque = ( HP * 5252 ) / engine_speed That's how I see it anyway... Last edited by BrianG; 06.23.2006 at 09:52 PM.