What is the formula for Horsepower?

Gene 007
WarWagon

 

PLAN/33000

which after some meddling gives you

(Tq(ft-lbs) x Rpm) / 5250

I hope that was the question..

 

Work = Force x Distance. If you push a 100 pound box 1 foot, you have 100 pound-feet of work.

Power = Work/Time. If it took you one minute to push that 100 pound box one foot then the power you expended was 100 pound feet per minute. If it took you two minutes then you did 50 pound-feet per minute of work. Get it?


From James Watt in the late 1800's - the number he came up with for one HORSEPOWER is 33000 pound-feet per minute or 550 pound-feet per second. So what James Watt figured was that a typical horse could pull or lift 550 pounds one foot in one second.

 

Technologist = formula's
Engineer = Theory

 

The 5252 comes from David's 33000 ft-lb/min divided by 2*Pi radians per revolutuon. Pi = 3.1415, so 2*Pi = 6.283. 33000/6.283 = 5252

 

"Work = Force x Distance. If you push a 100 pound box 1 foot, you have 100 pound-feet of work."

I think the 100 pound box is LIFTED, not PUSHED. Pushing is too vague since friction would have to be defined.

Steve

 

I had an error in my calc. 5252.. Thanks Banshee

 

In "theory" it is either pushed or lifted as the term is distance. But I see your point.

 

yep-- Hp= (tq*rpm)/5252

This lets us see how you can "make" hp just by revving the engine higher. This makes sense because the engine is moving more air and burngin more fuel at higher rpm, so it SHOULD make more HP.

It also explains why we can multiply torque but not power. Since power is the product of force AND time, we can trade one to get the other with gears. IOW, we can get more force by trading in some time and vice versa with gears. however, the overall product of POWER will remain constant.

That's why it IS hp that rules, not TQ. People mistakenly think that "tq moves the load, hp keeps it moving". Not true. You can't feel a difference between torque and hp. When someone says an engine has "good low end torque", then actually mean that it has good low end HP (which IS tq).

Tq *is*hp, in a sense. Hp is the RATE that torque is applied.

Clear as mud?

Justin

 

Actually, if it is pushed, the work done would be F x D, but F would be equal to M x Cf (coefficient of friction) between the 100 lb box and the surface on which it is placed. If you push a 100 lb box 1 foot on a surface with a coefficient of friction of 0.3, you have done 30 ft-lb of work.

The original W = F x D assumes that the load is lifted - that is, (to oversimplify) F = M. If you lift a 100 lb box 1 foot, you have done 100 ft-lb of work.

Rusty