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The horsepower (hp) is the name of several non-metric units of power. In scientific discourse the horsepower is rarely used due to the various definitions and the existence of an SI unit for power, the watt (W). However, the idea of horsepower persists as a legacy term in many languages, particularly in the automotive industry for listing the maximum power of internal-combustion engines.The various types of horsepower are:
1 hp
According to the most common definition of horsepower, one horsepower is defined as exactly:
- 1 hp = 745.69987158227022 W
The horsepower was first used by James Watt during a business venture where his steam engines substituted horses. It was defined that a horse can lift 33,000 pounds with a speed of 1 foot per minute: 33,000 ft· lbf· min-1. This is roughly equivalent to lifting 147,000 Newtons (the weight of a 15,000 kg mass) at a speed of 0.005 metre per second.
2 RAC horsepower
This measure was instituted by the Royal Automobile ClubThe Royal Automobile Club is a private Gentlemen's Club and is not to be confused with the RAC plc. It has two clubhouses; one in Pall Mall, London and another in the countryside at Epsom. It was founded on 8 August 1897 as the Automobile Club of Great Br in BritainThe United Kingdom of Great Britain and Northern Ireland is a state in Western Europe, usually known simply as the United Kingdom the UK Britain or less accurately as Great Britain . The UK was formed by a series of Acts of Union which united the formerly and used to denote the power of early 20th century19th century 20th century 21st century more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901- 2000 in the sense of the Gre British cars. Many cars hence had names such as "40/50hp", which indicated the RAC figure followed by the true measured power.
RAC horsepower cannot be given as a proportion to metric power. Instead, it is derived from dimensions of the engine and certain assumptions about engine efficiency. When invented, it gave a rough guide to its true power rating; as new engines were designed with ever-increasing efficiency, it was no longer a useful measure, but was kept in use by UK regulations which used the rating for tax purposesThe tax horsepower was an early system by which taxation rates for automobiles were reckoned in some European countries, like Britain and France. The tax horsepower rating was based on a pure mathematical formula based on cylinder dimensions. The British.
-
- where
- D is the diameter (or bore) of the cylinder in inches
- n is the number of cylinders
3 PS
This unit (German: Pferdestärke = horse strength) is still commonly used in Germany and central Europe, although not a lawful unit any more. It was adopted throughout continental Europe with designations equivalent to the English "horse power", but mathematically different from the British unit. It is defined by the Physikalisch-Technische Bundesanstalt (PTB) in BraunschweigBraunschweig may also refer to the administrative region of Germany. See Braunschweig (region). Brunswick may refer to several geographic locations, companies and products. See Brunswick (disambiguation). Braunschweig [ˈbraunʃvaik] (English: as exactly:
- 1 PS = 75 kp·m/s = 735.49875 W
