I have worked on equipment most of my life and still don’t understand.
nearly all energy put into an ice engine that isn’t lost as heat goes to spinning a shaft. please explain to me how i can tell the difference between torque and horse power?
In: Physics
Power is made up of two things
1. how hard you turn the crank
2. how fast you turn it.
Multiply the two together and you have power.
Torque is just how hard you turn the crank.
You can push on the crank as hard as you want, but if it doesn’t turn, you’re not delivering any power.
Torque = how hard it can turn
Horsepower = how fast it can turn hard
They are closely related to each other which makes it difficult to separate them. Horsepower is torque times distance over time. Its power, which is work over time. Work is force times distance.
A slow rotation engine can be very high torque, but low horsepower because it can’t apply that torque over much distance. You can have a low torque motor that spins super fast putting out decent horsepower because it’s applying low torque over a large distance.
My understanding is torque is the pulling force and horsepower is more about maintenance.
So a truck trying to pull a trailer needs torque. That puts most of the energy starting movement for something that is heavy and not already moving. Once it starts moving, torque is “wasted”. Thinking about it this way helps you understand torque isn’t about how fast the engine spins but about how hard it will push to MAKE itself spin. Attach a heavy weight to a high torque motor and it’ll start moving easily, but slowly.
A race car trying to go very fast is using horsepower. That’s not a very strong force, it’s best used to make something that’s already moving keep moving at that speed. Horsepower is about letting the engine spin very fast, but it can’t push hard to MAKE itself spin fast. If you attach a weight to a high horsepower motor, you’ll probably have to give it a push to get it started. Then you’ll watch it slowly accelerate to a high RPM.
That’s why cars have gearboxes. The low gears are about getting the heavy car moving and pulling loads: they focus on torque. Higher gears are about maintaining speed once the car reaches it: they focus on horsepower.
Imagine that you are trying to push a pile of rocks from A to B. There are two things that will definitely affect how fast you can get that pile from point A to point B. One is how hard you can push at all. Depending on the rock, you might not even be strong enough to budge it one little bit, but somebody who is stronger might still be able to move it. Another is how fast you can move it once you get it moving. Maybe you’re not super strong, but you’re extremely fit cardiovascularly, so you can move that object faster than somebody who might be stronger but less fit. On the other hand, if you’re moving something really close to the maximum weight you can push, you might have to take breaks. Who knows?
For an engine, the maximum torque is the equivalent of the heaviest object you can push. The maximum horsepower is the equivalent of the weight of the rock you can push times how fast you can push it — as in, how fast can you move one heap of rocks equaling a particular weight from location A to B. But of course that’s limited by the weight of the rocks in the sense that if all the rocks are too heavy to push, you won’t get anywhere at all.
Once upon a time inventor James Watt was comparing newfangled steam engines to each other. There are two main ways to measure the output of a machine that applies rotational force. Torque is a measure of how much turning force it applies. A steam engine with high torque was very good for moving heavy loads from a stop. On the other hand, you could also measure how many rotations the engine produced in one minute, or RPM. Ideally you would want an engine that had both high rotational force (high torque) applied very rapidly (high RPM) but because of physics this is hard, and engines that run at high RPM tend to have lower torque.
“Shut up, nerd,” said the mine owners Watt was trying to convince to buy steam engines. “I don’t care about any of that, all I know about is horses, and I only care how long it will take one of your steam engines to do the job.” Thus, the unit of horsepower was born: about the amount of work that an average horse can do in one second. Horsepower solved the torque vs. RPM dilemma because if you’re just measuring the amount of work per second you can compare high torque / low RPM engines directly to low torque / high RPM engines. You can multiply torque and RPM together and then if you know the load you know how long it will take the engine to do the job. And presumably sell more steam engines to mine owners, as that’s the metric they’re most interested in
In simple terms.
Torque, is how much work an engine can produce.
Horsepower, is how fast it can do that work.
Torque is how strongly the engine is turning the crankshaft. Horsepower is the product (multiplication) of torque and rotational speed. You can have a high horsepower by producing lots of torque at low speed or a little torque at high speed.
In internal combustion engines, the amount of torque the engine can produce will vary with speed, and different engines have different speed/torque curves. Big diesels tend to produce lots of torque but are not able to spin very fast, while gasoline engines tend to be lower on the torque but can run at higher speeds so can generate lots of power.
Power is what matters.
Torque just explains the character of an engine. If someone says that an engine has a lot of torque, they usually mean that it has a lot of power at low rpm.
Low torque engines need high rpm to produce power, like motorcycle engines.
Power is the specification that tells you how fast a vehicle can accelerate, or how much load it can pull.
Horsepower is torque * rpm.
Through gearing you can get any torque you want from a given amount of horsepower.
Horsepower is the rate at which work can be done.
You can have torque with 0 horsepower, but you cannot have horsepower without torque.
A 20 hp engine with high torque (diesel), can perform exactly as much work as a 20 hp engine with lower torque (gas).
One reason why people will believe that a diesel is more powerful is that a diesel will lug, instead of stalling like a gas engine, it will continue to run down to a much lower rpm.
Torque is literally rotational force, if you have a 1 foot lever with a one pound weight on the end, you have 1 ft*lbs of torque. Horse power is a function of that force multiplied by the rpm of the engine. There are other factors, but this is the base of it. How much force can be harnessed in a certain amount of time gives you horsepower.
My little 2.8 diesel makes almost as much torque as a v8, but because it can only spin half as fast which is less applications of that force in a given time meaning it will have less horse power.
Same as how small tuners have very little torque, but it can turn incredibly fast, which generates a lot of applied force per unit of time.
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