A lot of people seem to be confused about Torque and Horsepower. Maybe this article will help.
We will use the above dyno of a 50cc moped as one example. Just kidding it's a twin turbo mercedes V-8.
....this article needs to be finished......for now they are different units! One measuring turning force, the other at what rpm that torque can be apllied.
Anyway, let's start with the definition.
For science & engineer types the definition is built in to the units ! it's so simple and beautiful ! really it is...........
Torque is a way to quantify the strength of a twisting (rotational) force.
Torque is expressed in units of Force x Distance. It is shown as ft lbs which really means ft x lbs (feet multiplied by pounds)
Or lbs x feet because in mathematics ther order does not matter when multiplying.
example: 500 ft lbs of Torque, means whatever lbs you have multiplied by whatever distance you have =the Torque amount
Imagine you have a bolt sticking out of a building and a wrench on that bolt. If you wanted to apply 500 ft lbs of TQ (twisting) to the bolt you could apply 500 lbs at the
end of a 1 foot wrench (1 x 500=500), or 50 lbs at the end of a 10 foot wrench (50 x 10 = 500).
Very Important Note: There is no unit of time included in the units of Torque, so the rate that you can turn that bolt is not acoounted for .
There are two ways to look at this:
1) maybe 500 ft lbs is not enough to turn the bolt so the bolt is not turning yet 500 ft lbs is still the Torque, it is a static situation,nothing moves (a clue).
2) 500 ft lbs and the screw is turning, how fast? It doesn't matter Tq has no units of time. In the case the 500 ft lbs of TQ can be thought of as instantaneaous
application of Torque repeatedly applied. Never the less, if one knows the "feet " and the "lbs" one knows nothing about time or speed (speed is based
on knowing time).
Science students are taught that the Concept of WORK is based on distance and force also, if one moved 50 lbs of Brick 10 feet they have done a certain amount of work. Work also does not
describe how fast the 50 pounds of brick get moved 10 feet.Because there is no unit of time involved.
The definiton: 1 Horsepower = 33,000 lb ft/minute see the numerator is lb x ft , thats the TQ we just talked about.
Let's forget about the horse , POWER =work/time= (force x distance)/time= Torque/time
So POWER (and Horsepower) does include time in it's definition. It's an expression of how much WORK or TORQUE can be applied in a certain amount of time, the RATE at wich TQ can be applied.
(the Horse part is just a reference to make the standards relative to how much work a hose can do basically www.en.wikipedia.org/wiki/Horsepower )
For example : If you can have applied 500 ft lbs of torque to a bolt and it's not turning that is still ZERO hp.
If you can apply 500 ft lbs of torque to a bolt and turn it at 2 turns per second that is twice as much Hp as 500 ft lbs turning at 1 turn per second.
The torque is the same but the power used is double because you did the same work twice as fast.
more on this later