Friday, November 4, 2011

Torque and Horsepower

What is torque?  Torque is a radial force that causes an object to rotate.  Torque is measured by multiplying Force and Radius.  Basically, if you connect a one foot long arm to a pivot point (shaft) and hang a ten (10) pound weight on it, you get 10 foot pounds of torque expressed on the pivot point or shaft.  Make sense?

Take the example above and say you want to express 30 ft. lbs. of torque on the shaft.  You can do this by one of three methods:

-         place 30 lbs of weight on the 1 foot long lever
-         leave the 10 lbs. of weight on but increase the length of the lever to 3 feet
-         any combination where the weight and the lever equal 30 pounds

Remember, Force x Radius = Torque

So what is Horsepower?  Horsepower can be defined in foot-pounds per second.  It is a power measurement of an amount of energy that can be expressed in many ways, but the primary way is in Watts.  One horsepower is 746.  Here is a simple formula that can be used to calculate horsepower when the torque requirement and the speed is known:

                               HP =    Torque x RPM                                   

A simple method of calculating the Torque of a specific motor when you know the horsepower and the speed is by doing the following:

                                  Torque =  Horsepower x 5250

Just a few simple formula’s that were taught to me many years ago and I never forgot them.  Believe it or not, once you know how to do this, you really do use it when working around equipment in our field.