Why Not Torque Instead of HP

[Ritter107]

I was always told Horsespower is how quick the work gets done, Torque is what it takes to kill it.

[Patbretagne]

Not knowing much about either torquepower or horses, I am indebted to this string to bring me up to strength on these matters,
Steam as I think George said has a guaranteed torque even when the engine is at rest because the power is there in the boiler "Latent" that is it is waiting to deliver. With a steam engine it doesn't need to be turning to start the process working, an internal combustion engine needs to turn to suck in the air/fuel mixture so it can go bang and continue turning. The steam engine produces it's power through expansion. Steam at 0 lbs sq in as what comes out of a kettle only has velocity and will turn a windmill just like wind. Steam at 150 lb sq in not only has pressure but also expansion, the higher the pressure the greater the expansion and the more economic the whole shebang.
The internal Combustion also uses expansion but not latent expansion, wonderful stuff steam, a steam engine always has a good smell about it, takes me back to the days when I had a 10 ton Wallis and Steevens Road Roller of 1903, rebuilt it boiler riveting, engine mechanics etc, used it on the road for fun for a number of years then sold it to buy a better house.
Steam on the road is a young man's game, but a good game at that!
Pat the rambler
PS Compressed air does not work the same as steam because it is not expansive, it just has pressure, the moment it is released it is gone, steam continues to expand once it has left a nozzle.

[Jack fowler]

I see what everyone is trying to tell me now. I guess (maybe) you can relate it to an electric motor which has no internal parts like a combustion engine. The energy (torque) volts is something like steam which is the push. The flow (power) amps is the flow of steam when released to the engine.

I’m I correct by saying this?

[George Willer]

Jack,

I would compare power to WATTS (amps x volts), but the volts/torque analogy is probably right. Torque is a FORCE (without actually moving something, it isn't doing anything), and power is a force times distance over time.

[400lbsonacubseatspring]

Here is a good, concise link to an explanation of James Watt's original Torque and HP calculations, based upon the power of a real horse.

http://www.offroaders.com/info/tech-corner/reading/horsepower-torque.htm

For the most part, Torque (in ft lbs) is interchangeable with the basic unit of work (in ft lbs). While they are not the same, they are measured in the same units, and work the same in calculations. One could say that torque is "latent" work, or work that would have occured if there was not a resistive force.

A real life calculation of this is expressed as an amount of work done in a certain amount of time. The formula for this is:

HP = Force (in lbs) X Distance (in Feet) / ( 33,000 ft lbs/min) [a constant] X Time (in minutes)

Let's go back to my earlier theoretical experiment of Ralph and I running up a flight of stairs.

Ralph weighs 100 lbs (That's our force) the height of the stairs is an arbitrary 10 ft (that's our distance) It takes him 1.0 minutes (that's our time.)

We can now calculate how much hp ralph generated.

100 lbs X 10 ft = 1000 ft lbs
33,000 ft lbs/min X 1.0 minutes = 33,000 ft lbs (the minutes cancel out)

1000 ft lbs / 33,000 ft lbs = .03 HP

Now, for my part of the experiment...

I weigh 400 lbs, and it takes me 2.5 minutes to climb the stairs.

400lbs X 10 ft = 4000 ft lbs
33,000 ft lbs/min X 2.5 minutes = 82500 ft lbs

4000 ft lbs / 82,500 ft lbs = .048 HP

And while these are arbitrary numbers (in reality, Ralph is probably faster than that, and I am probably slower) You can see how speed, torque, and power actually are quite different. the two of us generate nearly the same horsepower. Although I have hauled 4 times the weight up those stairs, requiring me to put a lot more "torque" (actuall force) on my legs to do so. I have generated 4 times the torque, in reality...4000 ft lbs, compared to his 1000 ft lbs, and yet, I have not even generated twice his horsepower. Simple reason being that he is much faster than I am.

When you shift gears into a lower gear, you are increasing torque at the expense of speed, and hence, horsepower remains (theoretically) constant. When you shift to a higher gear, you are increasing speed at the expense of torque. Again, horsepower remains constant.

If you "gear down" any mechanical arrangement, you increase its torque at the cost of speed. If there is no minimum speed requirement, you can perform huge amounts of work with the very smallest motors. If speed is required, you can do limited amounts of work very quickly.

It would be possible to power any machine with the cub's PTO, if speed were not a requirement. You merely would have to reduce the gearing, by either gears, sprockets, or pulleys, in order to do so.

This is the reason that Rick's backhoe works on his cub. He has reduced the gearing, and the hydraulic system of the hoe provides some mechanical advantage. The hoe was rated for tractors having 30hp, but it works just fine on the cub, albeit likely not as fast as it would on larger tractors.

I hope this was more helpful than confusing.

If not, perhaps I at least have given you a new appreciation of the amount of work fat people do when they climb stairs......

Tom

[400lbsonacubseatspring]

Jack,

I would compare power to WATTS (amps x volts), but the volts/torque analogy is probably right. Torque is a FORCE (without actually moving something, it isn't doing anything), and power is a force times distance over time.

HP and watts are both accepted terms for power, in fact, they are interchangeable. 746 watts = 1 HP We don't do it here, but in many asian countries, small engine horsepower is expressed in KW, rather than HP....

Amps is a term best compared to "flow" or in our discussion here, distance, but only in analogy.

Volts is a term best compared to "pressure" or in our discussion here, force, but again, only in analogy.

The reason we don't need to be concerned with the "time" factor in electrics is that electrons flow at a speed which is more or less constant (depending on the material, in the age of semi-conductors, I guess). That being the speed of light.