Any car owner would probably know how many “horses” there are in his car. After all, this simple parameter allows comparison with other models. Gone are the days when movement was carried out with the help of graceful animals. Powerful devices generate much more power today. But why is horsepower used as the benchmark?
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The term was coined by Scottish engineer and inventor James Watt around 1789. The creator of steam engines wanted to convince the whole world of their effectiveness. To do this, Watt had to show that his device can replace several horses at once. It remained only to somehow measure the work that the animal is able to do in a unit of time.
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What is horsepower and how much horsepower is in one horse?
According to legend, one of Watt’s first machines was purchased by a brewer. He chose the strongest horse and made it work for exhaustion. So the cunning brewer tried to belittle the capabilities of the machine in comparison. The inventor took the data obtained and made it the standard. But in reality, an ordinary horse actually develops power one and a half times less for a long time.
Another story looks much more true. Watt personally conducted observations in coal mines. At that time, it was the horses who were engaged in raising barrels with people, water and coal from there. Watt calculated that an ordinary animal can lift a 75 kilogram load at a speed of 1 meter per second (75 kgf · m / s) for a long time at a standard acceleration of gravity (9.80665 m / s²).
Thus, horsepower corresponds to 736.56 watts.
But these calculations referred to the power averaged over a long time. For a short time, a horse is capable of developing a power of up to 9.8 kW, which is 13 times more than its usual calculated unit of force, but with normal rhythmic work, it just turns out about one hp.
Such measurements can give rise to different results, which will differ even from their location in relation to geographical latitude. So there were many variations of horsepower: metric, water, electric, boiler, British and tax … Finally, the confusion was ended in 1960 with the adoption of the International System of Units. Power is now finally expressed in watts and horsepower is 735.5 watts. Interestingly, in America and England, horsepower is about 1.3% higher than our metric standard.
Russian designation for horsepower: l. from.; English: hp; German: PS; French: CV.