Why Not Torque Instead of HP

[WKPoor]

Been wondering about something for quite awhile and thought I would pester this crowd with my question of the week.

Why is torque not mentioned when describing a tractor engine power when most tractors produce up to 6 times more torque than HP? Auto engines on the other hand have typ. less torque than HP. To me the torque is the missing piece to the puzzle of why these old machines can do so much work on so little HP. Everyone constantly talks about how much HP but never bother to mention torque. These engines would never be big on HP with so little RPM but torque they got especially for there size. My H has almost as much torque as a chevy 350 with a fraction the HP and a third less RPM. So again, why is torque seeminly always left out of the equation?

[Lurker Carl]

Way back when engines were newfangled contraptions, horsepower was something everyone could understand. Torque didn't mean anything to the common man. The advertising folks knew how to sell engines for replacing horses. This engine has the power of 3 horses! Wowee! No one could fathom what 80 pound feet of torque could do.

Torque is a direct measurement, horsepower is a calculation. It's easier to fudge a calculation to make it seem more than it is.

[George Willer]

Torque is a fairly good comparison to help determine the maximum pull an engine can produce compared to another, but horsepower better reflects how much work it can accomplish in a given amount of time. Which kind of measurement is best is dependent on which is more important to you. In most cases horsepower tells a better story.

[Carm]

Isn't torque for the low end work and horespower for the high end work. Or something like Torque gets you there but horsepower keeps you there?

[Jack fowler]

Lurker Carl said

Way back when engines were newfangled contraptions, horsepower was something everyone could understand.

To my understanding this is why Horsepower was the term that was used for the Farmer because; he could only relate to Horses for the power of the machine that was going to replace the horses.

Personally I like the term "torque at low RPM’s", because that means Engine efficiency, which means low fuel cost, but you get from point A to B slower. (Remember the John Deere two cylinder tractors when worked hard). You couldn’t stall it and it burned one gallon of fuel an hour doing a lot of work. The Farmall Cub is another good example for its size.

A Diesel engine is designed for high torque at low RPM’s. In Europe the automotive industry is primarily Diesel engines for transportation. I personally drove a European version Ford Taurus with a six speed manual transmission with a four cylinder Diesel turbocharged engine. I didn’t inquire about the torque and horsepower of the engine but the car ran very well on the highway at 60 to 70 MPH. It also was getting 56 MPG. My dad drives an American version Ford Taurus with a six cylinder engine with an automatic transmission. The best fuel mileage he gets is 27 MPG on the highway. The American version Taurus will get to 100 MPH in a matter of seconds, the European version in matter of minutes.

WKPoor said

My H has almost as much torque as a chevy 350 with a fraction the HP and a third less RPM.

If you could, put that stock Chevy engine in the “H” tractor and make it work at the same RPM’s as the “H” engine would work at. I bet you the Chevy engine wouldn’t pull half the weight the “H” engine could. What engine has more power now? But “turn” that Chevy engine up a few RPM’s and see what happens. What engine has more power now? What engine would burn more fuel doing the same work?

In aviation (turboprop engine’s) is measured by engine output in torque -- what's being delivered to the propeller.

Torque is a turning or twisting force. The engine, crankshaft rotates with a torque transmitted through the drivtrain to turn the drive wheels.

Horsepower is the rate at which torque is produced. Engines produce power by turning a crankshaft in a circular motion. To convert terms of force applied in a straight line to a force applied in a circular motion, the formula is: torque= force x radius.

If the torque output of an engine at a given speed (rpm) is known, horsepower can be calculated by the following formula. HP= (torque x rpm) ÷ 5,252.


Jack Fowler

[George Willer]

It's not productive to try to use the two terms interchangeably... they are telling very different things. Torque by itself means almost nothing useful. When it comes to torque, the steam engines win by a large margin. As a matter of fact, many, if not most develop their maximum torque when they aren't turning at all! Horsepower is a measure of torque modified by how quickly the machine can produce it. The faster an engine can produce a given torque, the higher the horsepower. This is indirectly why we need transmissions.

[Carm]

So I guess my non technical assessment is a bit off. Horsepower helps torque get you there more quickly. So in the turboprop, the engines are rated by shaft horsepower or equivalent shaft horsepower but their output is measured in torque at a given RPM. So engine mass along with the horsepower creates torque. or engine mass at a given RPM will give you torque.

[WKPoor]

What I'm basically trying to point out is that the HP numbers are small on these tractors but they are still able to do great amounts of work. When someone says my garden tractor has more horsepower than your big ole H they don't have the whole story.

Then there is the other topic of how HP #'s are taken which can lead to preformance confusion of similar products.

[Lurker Carl]

Is that garden tractor remotely capable of doing what the H can?

Horsepower ratings on 'garden' tractors and lawnmowers are grossly inaccurate. Most are rated at the maximum horsepower the engine can ideally produce, not at the actual speed and conditions at which the engine will operate for the consumer. The 20 hp garden tractor might only make 15 hp at the flywheel as set up by the manufacturer, the belt drive system and hydrostatic tranny gobbles up another 8 hp, another 1-2 hp are used for recharging the battery and cooling the engine. Actual drawbar horsepower is far below the horsepower number stamped on the engine shroud.

[Paul B]

This is just my opinion, but you normally see the horsepower rating of a tractor used as a measure of what the tractor can be used for, such as, a 10 hp tractor will pull X number of plows, a 20 hp will pull maybe twice as many , 30 hp maybe three time as many, etc. Any time you see anything stated about the size/use of antique tractors or tractors of the Cub era, it is usually stated that it is a XXX plow tractor. I believe most of the tractor brands of this era, of a given horse power, had engines of similar size, displacement wise, and most had a similar torque output, and ran at similar RPM's. But the horse power rating of the tractor is what was used to basically determine what a tractor of that size could do. The size and number of plows a tractor of a given hp could pull, may have been a carryover from horse farming days based on how many horses it took for a given job, I don't know, but as someone else said, basically torque is what get's you moving, horse power is what keeps you moving. Because of the gearing and the gear reduction of a tractor, the torque to get that plow moving wasn't as important to the farmer as was the horsepower to keep it moving. Just my opinion, and I may not be right, ..... but it makes sense to me, that's my story, and I'm sticking to it

[George Willer]

There are a number of ways to say the same or similar things, but torque is merely a way to express a force. That force must be multiplied by a distance to become a statement of power. The force (torque) by itself tells nothing about power.

One horsepower is equal to a force (torque) of 33,000 lbs. acting over a distance of 1 foot in one minute, or a force of 1 lb. acting over a distance of 33,000 feet in one minute or anything in between. Torsional force (torque) is really a force acting at a given radius, and says very little by itself about power.

Sears horsepower is measured under very different rules. They just make them up.

[Lurker Carl]

Sears horsepower is measured under very different rules. They just make them up.

Well said!

[Jack fowler]

I’m getting confused here and I know I’m arguing with the wrong person, this is my thinking;

Engines don’t make horsepower;they convert fuel into torque. Torque is the twisting force imparted to the crank flange and then transmitted to the transmission and the rest of the drivetrain. To some degree torque is the grunt that gets things moving, and horsepower is the force that keeps things moving. An engine is most efficient at its torque peak, wherever that happens to occur. This is generally beneficial in that it lets engines produce most of the desirable grunt work (torque) at lower engine speeds, which means reduced wear-and-tear and better fuel economy. Horsepower is torque multiplied by engine speed to produce a measurement of the engine's ability to do work over a given period of time.

This is an article that maybe an interest:

http://vettenet.org/torquehp.html


Jack Fowler

[Carm]

Thats a pretty good article. Thanks!

[400lbsonacubseatspring]

When it comes to torque, the steam engines win by a large margin. As a matter of fact, many, if not most develop their maximum torque when they aren't turning at all!

This is why steam powered cars always won the uphill races. Also, Steam locomotives had no reduced gear train, they were direct piston-to-wheel engines. They could start under incredible loads from a stop

Horsepower is a measure of torque modified by how quickly the machine can produce it. The faster an engine can produce a given torque, the higher the horsepower. This is indirectly why we need transmissions.

and why steam engine vehicles did not....