Horsepower is an off-system unit of power that has officially been taken out of use in Russia, but still finds use, for example, in the automotive industry.
Perhaps many of us, representing horsepower, use something like the following analogy: if a car with a capacity of 100 hp. tie a rope, at the other end of which there will be a herd of 100 horses, then starting to move in opposite directions, they will not be able to budge. And this is not entirely true. In practice, the horses will most likely win and simply disable the car's transmission at the start. The fact is that engine power in horsepower is a nominal value. To convert the potential energy of the engine into kinetic energy, it is necessary to develop a certain frequency of rotation of the crankshaft and transfer the required torque to the wheels. In addition, horsepower is a relatively strictly established value, and the capabilities of horses can vary greatly and differ from this parameter.
Horsepower unit of power and ratio with Watts
The first to use the term "horsepower" was the famous English (Scottish) mechanic-inventor James Watt. This thought occurred to him while he was watching the work in the coal mines, where horses were used to lift rock to the surface of the earth. Looking at the process from the point of view of physics, the scientist determined that the horse has some power, which can be calculated by the ratio of work performed to time. The mass of coal lifted from a depth of 30 meters in one minute was taken as the basis. It turned out 150 kg / 1 m - he determined this value to be 1 hp (HP - horse power) Later, in 1882, The British organization of engineers introduced the watt, a unit of measure equal to 0.736 hp.
By the way, the subsequent recalculation of the indicators calculated by Watt showed that in reality no horse is able to develop sufficient power to vertically lift 150 kg of load at a speed of 1 m / s. Moreover, in the mines where Watt carried out his calculations, ponies were used for work. It is believed that he calculated the performance of one horse per minute in foot-pound ratio and increased this figure by 50%. According to one version, the inventor deliberately equalized the power of his engine with the power of a horse in order to demonstrate the greater productivity of the unit in order to sell it.
How to convert watts to horsepower
In 1784, James Watt introduced the first steam engine to the public. To measure the power of the unit he invented and designed, Watt introduced the term "horsepower", which he had previously developed.
The further development of mechanics gave rise to the emergence of a number of similar "horsepower", denoting different sizes. The presence of several units of the same name leads to the need to transfer power between different measuring systems. In 1960, the watt was established in the international SI system as the official unit for measuring power. Despite this, horsepower is still used in some areas of activity, in particular in the automotive industry.
To carry out the transfer of 1 hp. in watts, you need to multiply the power indicator by 736: 1 hp. \u003d 736 W. Accordingly, the reverse translation is made by dividing the value by the same number. Examples:
- 5 hp = 3.68 kW;
- 10 kW = 13.57 hp
But not everything is so simple! Therefore, we read the text below under the video, which can also be useful for understanding the basic physical quantities of an electrician.
Such different standards
After Watt's definition of a new unit of measurement, his "horsepower" appeared not only in different measurement systems, but also in individual countries. Today, this unit is not officially recognized, but is used in 4 different versions:
- Metric horsepower (used in Russia). Equal to the power required to lift a 75 kg load at a speed of 1 m/s. To convert to watts, multiply by 735.5. Example: 2 HP = 1471 W.
- Electric horsepower. Used in electromechanics and electrics. To convert watts to this unit, you need to divide them by 746. For example, 4000 W (4 kilowatts) \u003d 5.362 el. hp
- Mechanical HP Corresponds to the values of the English system of measures. One fur. l. With. equals 745.7 watts (1.014 metric hp).
- Boiler horsepower. It is applied in industrial and power branch. To convert to kilowatts, the following ratio is used: 1 k. hp. = 9.809 kW.
The tradition of using horsepower in the automotive industry is associated with convenience - this value is characteristic and always understandable even to those who are far from the intricacies of auto mechanics. Much more people will be able to navigate what a car with a declared power of 150 hp is capable of, but 110.33 kilowatts will mislead the majority. Although in fact it is one and the same.
For a short time, a horse can develop a power of 10 - 13 horsepower, but with normal rhythmic work, just about one. Why was "horsepower" used as a unit of power? And how much is one horsepower?
The inventor of the steam engine, the Englishman James Watt (1736–1819), is “blamed” for this. He needed to clearly demonstrate to the public that his car could replace many horses, and for this it was necessary to somehow measure the work that the horse itself could produce in a unit of time.
Describe such a story. James Watt suggested using steam instead of horses in breweries. Watching horses, Watt noticed that a horse could drag a load weighing 14.774 kg over a distance of 0.3 m in 1 minute. Rounding 14.774 kg to 15 kg, he introduced the unit of power "horsepower". Comparing the performance of a horse and a steam engine using this unit, Watt convinced brewers to replace horses with steam, and as a result, the efficiency of the brewing process increased significantly.
This “herd” was finished in 1960 - the XI General Conference on Weights and Measures adopted the unified International System of Units SI (SI). In it, power is expressed in watts in honor of the same James Watt.
However, even now there is the concept of horsepower. At one time, Watt, observing the traditional source of energy - a horse, came to the conclusion that a barrel weighing 180 kg can be pulled out of the mine by two horses at a speed of 2 miles / h (3.6 km / h). In this case, the horsepower in English measures takes the form of 1 liter. With. = 1/2 barrel · 2 mph = 1 barrel · mile / hour (here the barrel is taken as a unit of force, not mass). The same in smaller units is 380 lbs at 88 ft/min. Rounding off the calculations in foot-pounds per minute, he decided that the horsepower would be 33,000 foot-pounds per minute. Watt's calculations referred to horse power averaged over a long time. For a short time, a horse can develop a power of about 1000 kgf m / s, which corresponds to 9.8 kW or 33,475 BTU / h (boiler horsepower)
Units of measure vary from country to country, and horsepower in Sweden is not exactly the same as in America, for example. In Europe, one horsepower refers to the power required to lift 75 kilograms one meter per second, or 75 kilogram-force meters per second (kgcm/s). At the same time, in the US, one horsepower means the power required to lift 550 pounds one foot per second, which corresponds to 33,000 pound-force feet per minute. In Russia, as a rule, horsepower means the so-called "metric horsepower", equal to exactly 735.49875 watts.
By the way, the photo at the beginning of the post is from the Library of Congress, taken around the 1890s at a logging site in Michigan.
In this way, timber was usually transported in spring and winter along a frozen path to the nearest railway or river. To make the movement of the sled with the load smoother, the road was watered, and the horses, as a rule, were put on special studded equipment on their hooves for better grip on the ice.
1 kW is equal to 1.3596 hp. when calculating engine power.1 HP is equal to 0.7355 kW when calculating the engine power.
Story
Horsepower (hp) is a non-systemic unit of power that appeared around 1789 with the advent of steam engines. Inventor James Watt coined the term "horsepower" to show how economically advantageous his machines were to draw power. Watt concluded that, on average, one horse lifts a load of 180 pounds 181 feet per minute. Rounding off the calculations in pound-feet per minute, he decided that the horsepower would be equal to 33,000 of these same pound-feet per minute. Of course, the calculations were taken for a long period of time, because for a short time a horse can "develop" a power of about 1000 kgf m / s, which is approximately equal to 13 horsepower. This power is called boiler horsepower.In the world there are several units of measurement called "horsepower". In European countries, Russia and the CIS, as a rule, horsepower means the so-called "metric horsepower", equal to approximately 735 watts (75 kgf m / s).
In the automotive industry in the UK and the US, the most common hp. equate to 746 watts, which is equal to 1.014 metric horsepower. Also used in US industry and power is electric horsepower (746 W) and boiler horsepower (9809.5 W).
Horsepower
Horsepower(hp) - off-system unit power.
In the world there are several units of measurement called "horsepower". In Russia, as a rule, horsepower means the so-called " metric horsepower”, equal to approximately 735 watts.
Currently, in Russia, formally, horsepower has been taken out of use, but is still used to calculate the transport tax. In Russia and in many other countries, it is still very widespread in the environment where internal combustion engines are used (cars, motorcycles, tractor equipment, lawn mowers, trimmers).
In the International System of Units ( SI) the officially established unit of power measurement is watt.
In the English ("Imperial") system of measures, the pound-feet per second is considered the unit of power, but in reality it is no longer used in England, and in the USA it is used extremely rarely.
Horsepower Options
In most European countries, including Russia, horsepower is defined as 75 kgf/ , that is, as the power expended to lift a load of 75 kg to a height of 1 meter in 1 second with standard acceleration of gravity (9.80665 m / s²) . In this case, 1 l. With. is exactly 735.49875 Tue, which is sometimes called metric horsepower (notation German PS, fr. ch, netherl. pk ), although it is not included in the metric system of units.
In the US and UK, the automotive industry still equates horsepower to 745.69987158227022 watts (notation English hp), which is equal to 1.013869665424 metric horsepower.
The US also uses electric horsepower and boiler horsepower (used in industry and energy).
Ratios
To calculate the engine power in kilowatts, use the ratio 1 kW = 1.3596 hp. (1 HP = 0.73549875 kW)
Story
Around 1789, a Scottish engineer and inventor James Watt coined the term "horsepower" to describe how many horses could replace it steam engines. In particular, it is claimed that one of Watt's first machines was bought by a brewer to replace the horse that powered the water pump.
At this time in England, barrels (BARREL) with a volume of 140.9 to 190.9 liters were used to lift coal, water and people from mines. a typical barrel with a load weighed 400 pounds (1 pound - 0.4095 kg), i.e. 1 barrel = 163.8 kg. Naturally, only two horses could pull out such a barrel by a rope thrown over a block. The effort of an average working horse for 8 hours of work is 15% of its weight, or 75 kg with a horse weighing 500 kg. In 8 hours, a horse with such an effort can travel 28.8 km at a speed of 3.6 km / h (1 m / s). Observing the traditional source of energy - the horse, Watt came to the conclusion that only two horses could pull a 160 kg barrel from the mine at a speed of 2 miles / hour (3.6 km / h). In this case, horsepower in English measures becomes 1 hp = 1/2 barrel * 2 mill/h = 1 barrel*mill/h. The same in smaller units is 180 pounds on 181 foot. Rounding off the calculations in foot-pounds per minute, he decided that the horsepower would be 33,000 foot-pounds per minute.
Watt's calculations referred to horse power averaged over a long time. For a short time, a horse can develop a power of about 1000 kgf m / s, which corresponds to 9.8 kW or 33,475 BTU / h (boiler horsepower). According to other sources - up to 15 hp. at the peak.
At the Second Congress of the British Scientific Association in 1882, a new unit of power was adopted - Watt (symbol: W, W), named after James Watt (Watt), the creator of the universal steam engine. Prior to this, most calculations used the horsepower introduced by James Watt.
Engine power
For the power of automobile engines, there are not only different units of measurement, but also different ways of measuring, giving different results. The standard way to measure power in Europe uses kilowatts. If the power is given in horsepower, then the methods of measurement in different countries may differ (even if the same horsepower is used).
The USA and Japan use their own standards for determining engine horsepower, but they have long been almost completely unified with others. In both America and Japan, there are two types of indicators:
Net measurement
Net engine power measurement ( English netto, net) provides for a bench test of an engine equipped with all the auxiliary units necessary for the operation of the vehicle: a generator, a silencer, a fan, etc.
Gross measurement
If the power is less than 100 hp. s., then, for example, in the Moscow region 7 rubles / l are paid. With. per year, and if a little more - already 29 rubles / l. With. in year. Moreover, from 101 hp. up to 150 hp the tax rate is the same. Thus, due to different power values, the price changes from less than 700 to several thousand rubles a year. This fact leads to annoying curiosities. So, the power of a South Korean car Hyundai Accent equal to strictly 75 kW, that is, 102 liters. With. For an American car owner, 100.7 hp would be an even more offensive figure, but in the US, the tax does not depend on horsepower. In the US, some taxes (road, environmental) are included in the price of gasoline, in addition, you have to pay personal property tax every year, which is directly proportional to the price of the car.
In the past, in some countries (eg UK, Germany, Belgium, France, Spain) the vehicle tax was based on horsepower. In some countries, the use of power in taxation was abandoned (for example, in the UK in the forties, car dimensions were used instead of power), in others (for example, in France), kilowatts were used instead of horsepower. From those times, the expressions "Caballo fiscal" and "Cheval fiscal" remained.
In Russia, many car owners, mainly truckers, in their data sheets they underestimated the real power of the motor in order to reduce tax costs. However, at present, tax authorities usually take information about power not from technical passports, but from general databases (which, however, do not contain data on many relatively exotic car models or equipment, which is what their owners use).
see also
Notes
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