Another 4th year Question

here is another 4th year question that you might all be interested in getting the answer to:
In the torque equation T=HP÷rpm×5252 . Where does the 5252 come from in the equation?
Well.....
since there are 550ft-lb per second per horsepower, and 60 seconds in a minute going from HP and RPM to foot pounds will involve using the 550 and 60, multiply that out and you get 33000.  Since we are talking angular motion (RPM) and not linear motion there is a conversion going on.  Remember that circumference = pi*D?  and since D=2r we can throw 2pi in to convert our angular speed to a linear speed at a given radius (in this case 1 foot). Put 33000 in your calculator and divide by 2pi (6.28 approximately) and see what you get.

for more info see http://en.wikipedia.org/wiki/Torque down near the bottom of the page.

Greg McMurphy
Instructor
LU112-NECA Electrical Training Center
Kennewick, WA 99336