## Understanding Power and Torque

Difficulty
Easy
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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 lb-ft or oz-in (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 lbs-ft 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 lbs-ft.) 150 lbs-ft 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 ft-lbs, how much power is it producing?

HP = (RPM * TORQUE (in ft-lbs) )/5252

RPM = 2000 rpm

TORQUE = 160 ft-lbs

HP = 2000 rpm * 160 ft-lbs/ 5252

So this is the basic for understanding and using torque and horsepower.

Sam