
04132009 03:52 PM
Understanding Power and Torque
 Difficulty
 Easy
 Estimated Time
 N/A
 Skills Required
 None
 Parts Required
 None
 Tools Required
 None
Hello.
This is a brief tutorial about torque, horspower. I will put up some exemples to clarifie things. Most people know what these terms are and what they meen. If you don't, it's pretty important.
Torque :
Torque is calculated in lbft or ozin (not lb/ft or oz/in!). A simple example of applied torque is on a bicycle. When you push on the pedal, you exert a load (mass) on the pedal. Let's say you are pushing 15 pounds. If the pedal is a foot away from the center of rotation (where the gears meet the shaft of the pedals), you would be producing 15 lbsft of torque.
If, by some weird event, the shaft linking your pedal to the center of rotation (the gears) is 10 feet long, you would be producing (10 feet * 15 pounds = 150 lbsft.) 150 lbsft of torque. This is the basic comcept.
So, the formula is :
T = torque
F = Force
D = Distance.
T = F * D
Example :
So let's say you would want to know how much weight a servo rated at 200 oz.in. could lift if it were 12.5 inches away from the center of rotation.
T = 200 oz.in.
F= ?
D = 12.5 inches.
T/D = F
F = 200 oz.in./12.5inches = 16 oz.
So the servo could theoretically pull 16 oz of weight.
HORSEPOWER :
Horsepower is calculated using the following formula :
HP = (RPM * TORQUE)/5252
The constant 5252 may seem like it comes from nowhere, but it doesn't! It's just a bunch of numbers simplified into one. But you don't really need to know where it comes from for now.
Example :
If you know your engine is turning at 2000 RPM (Revolutions Per Minute) and that the torque it's producing is 160 ftlbs, how much power is it producing?
HP = (RPM * TORQUE (in ftlbs) )/5252
RPM = 2000 rpm
TORQUE = 160 ftlbs
HP = 2000 rpm * 160 ftlbs/ 5252
So this is the basic for understanding and using torque and horsepower.
Sam