HP = (Torque X RPM)/ 5250
where does this 5250 come from?
Thanks,
matt

 

1 HP is the amount of work one horse can do (duh): a gentleman named Watt measured it and discovered that one horse can lift 33,000 pounds one foot in one minute. think about that for a minute: 33,000 lbs, one foot, one minute; or, if you'd rather, 33,000 ft-lbs /per min.

Sounds rather familiar, no? ft-lbs, minutes... you're right. But, to get from linear feet to rotational torque, you use the factor of 2 pi, since a one foot diameter thing rotates 2 pi feet per revolution at the circumference. So, one horsepower = one ft-lb of torque x one revolution /2 pi. So, HP = (torque) x (RPM) x (33,000 / 2 pi) . 33,000 divided by 2 pi = 5252.11.

Make sense?

Incidentally, horsepower is not directly measurable, because it doesn't really exist. Torque does exist, and can be measured. Torque is the actual twisting force applied to something, acting over a distance; that is the textbook definition of "work" in the rotational mode. Horsepower (or any kind of power for that matter) is the time rate of doing work, and can only be measured by measuring the amount of work done and the time it was done in.