What is horsepower

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Like science, tech, and DIY projects? New Search. Find Near Me. Enter a Postal Code. We are currently experiencing technical difficulties. Please wait a few minutes and then try again. Back to Articles. How Horsepower Works In Vehicles How does this translate into the figures you see in vehicle specifications? You Might Also Enjoy. Read More. Watt lived from to and is most famous for his work on improving the performance of steam engines. We are also reminded of him every day when we talk about watt light bulbs.

The story goes that Watt was working with ponies lifting coal at a coal mine, and he wanted a way to talk about the power available from one of these animals. He found that, on average, a mine pony could do 22, foot-pounds of work in a minute. He then increased that number by 50 percent and pegged the measurement of horsepower at 33, foot-pounds of work in one minute.

It is that arbitrary unit of measure that has made its way down through the centuries and now appears on your car, your lawn mower, your chain saw and even in some cases your vacuum cleaner. What horsepower means is this: In Watt's judgement, one horse can do 33, foot-pounds of work every minute. So, imagine a horse raising coal out of a coal mine as shown above. A horse exerting 1 horsepower can raise pounds of coal feet in a minute, or 33 pounds of coal 1, feet in one minute, or 1, pounds 33 feet in one minute.

You can make up whatever combination of feet and pounds you like. As long as the product is 33, foot-pounds in one minute, you have a horsepower. You can probably also imagine that you would not want to put 1 pound of coal in the bucket and ask the horse to run 33, feet in one minute, since that translates into miles per hour and horses can't run that fast.

However, if you have read How a Block and Tackle Works , you know that with a block and tackle you can easily trade perceived weight for distance using an arrangement of pulleys. So you could create a block and tackle system that puts a comfortable amount of weight on the horse at a comfortable speed no matter how much weight is actually in the bucket. If you want to know the horsepower of an engine , you hook the engine up to a dynamometer.

A dynamometer places a load on the engine and measures the amount of power that the engine can produce against the load. Similarly, if you attach a shaft to an engine, the engine can apply torque to the shaft. A dynamometer measures this torque.

You can get an idea of how a dynamometer works in the following way: Imagine that you turn on a car engine , put it in neutral and floor it. The engine would run so fast it would explode. That's no good, so on a dynamometer you apply a load to the floored engine and measure the load the engine can handle at different engine speeds. You might hook an engine to a dynamometer, floor it and use the dynamometer to apply enough of a load to the engine to keep it at, say, 7, rpm.

You record how much load the engine can handle. Torque is responsible for how quickly your car accelerates, the more torque, the easier it is to get your wheels turning.

You may see a torque figure followed by an engine speed, for example 1,,rpm. This means peak torque delivery is around these revs, so it's better to change up a gear if the revs are too high. Electric cars differ here, though, because torque is delivered instantly - there's no need to build the revs up. The term horsepower dates back to the black and white times when a man named James Watt as in the Watt in kilowatt supposedly used horses to define how quickly he could remove materials from a mine.

Over time the term stuck, but various alternatives have cropped up such as kW and PS , as has confusion! Home cars What is horsepower?

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