Torque Torque is a force that rotates or turns things You by monkey6


Torque Torque is a force that rotates or turns things You

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									Torque: Torque is a force that rotates or turns things. You generate a torque every time you apply a force using a wrench. Tightening the wheel nuts on your car is a good example. When you use a wrench, you apply a force to the handle. This force creates a torque on the wheel nut, which turns the nut. English units of torque are Foot-Pounds; the SI unit is the Newton-meter. Notice that the torque units contain a distance and a force. To calculate the torque, you multiply the force by the distance from the centre. In the case of the wheel nuts, if the wrench is a foot long, and you put 200 pounds of force on it, you are generating 200 Foot-Pounds of torque. If you use a 2-foot wrench, you only need to put 100 pounds of force on it to generate the same amount of torque. A car engine creates torque and uses it to spin the crankshaft. This torque is created exactly the same way: A force is applied at a distance. The combustion of gas in the cylinder creates pressure against the piston. That pressure creates a force on the piston, which pushes it down. The force is transmitted from the piston to the connecting rod, and from the connecting rod into the crankshaft. The horizontal distance changes as the crankshaft spins, so the torque also changes, since torque equals force multiplied by distance. You might be wondering why only the horizontal distance is important in determining the torque in an engine? When the piston is at the top of its stroke, the connecting rod points straight down at the centre of the crankshaft. No torque is generated in this position, because only the force that acts on the lever in a direction perpendicular to the lever generates a torque. If you have ever tried to loosen really tight wheel nuts on your car, you know a good way to make a lot of torque is to position the wrench so that it is horizontal, and then stand on the end of the wrench -- this way you are applying all your weight at a distance equal to the length of the wrench. If you were to position the wrench with the handle pointing straight up, and then stand on the top of the handle (assuming you could keep your balance), you would have no chance of loosening the nut. You might as well stand directly on the wheel nut itself. BHP – Horsepower: This term was coined by James Watt, who invented a new type of steam engine in the eighteenth century. Watt found that the horse could do a certain amount of work per second; when he sold his steam engines, this measurement allowed him to estimate the power of an engine in terms of the number of horses it would replace. Therefore, a sixhorsepower engine was capable of replacing six horses. The power of an engine can be measured or estimated at several points in the transmission of the power from its generation to its application. A number of names are used for the power developed at various stages in this process:

Indicated Horsepower (IHP) Indicated horsepower is the theoretical power of a reciprocating engine assuming that it is completely efficient in converting the energy contained in the expanding gases in the cylinders. It is calculated from the pressures developed in the cylinders, measured by a device called an engine indicator - hence indicated horsepower. It was the figure normally used for steam engines in the 19th century but is misleading because the mechanical efficiency of an engine means that the actual power output may be only 70% to 90% of the indicated horsepower. Brake Horse Power (BHP) Brake horsepower was a term commonly used before the 1970s in the United States, and is still common in the United Kingdom. It refers to the brake dynamometer, the device for measuring the true power of the engine. Stating power in 'bhp' gives some indication that this is a true reading, rather than a calculated or predicted one. However, it does not tell where the power reading was taken at the flywheel, transmission or drive wheels. We, at CHIPTUNING SA find the average car loses between 15 -20% of its power from the flywheel to the road wheel. Hp (SAE) In the United States the term "bhp" fell into disuse after the American Society of Automotive Engineers (SAE) recommended manufacturers use "hp (SAE)" to indicate the power of the engine, given that particular car's complete engine installation. It measures engine power at the flywheel, not counting drive train losses. Prior to 1972 most American carmakers rated their engines in terms of SAE gross horsepower (defined under SAE standards J245 and J1995). Gross hp was measured using a blueprint test engine running on a bench without accessories, exhausts, or emissions control devices. It therefore reflected a maximum, theoretical value, not the power of an installed engine in a street car. Gross horsepower figures were also subject to considerable adjustment by carmakers: the power ratings of mass-market engines were often exaggerated, while those for the high-performance muscle car engines were frequently underrated. In 1971 automakers began to quote power in terms of SAE net horsepower (as defined by standard J1349). This reflected the rated power of the engine in as-installed trim, with all accessories and standard intake and exhaust systems. By 1972 U.S. carmakers quoted power exclusively in SAE net hp. The change was meant to 'deflate' power ratings to appease the auto insurance industry and environmental and safety lobbies, as well as to obfuscate the power losses caused by emissions-control equipment. SAE net ratings, while more accurate than gross ratings, still represent the engine's power at the flywheel. Contrary to some reports, it does not measure power at the drive wheels. Because SAE gross ratings were applied liberally, at best, there is no precise conversion from gross to net. Comparison of gross and net ratings for unchanged engines show a variance of anywhere from 40 to 150 horsepower. Hp (DIN) This is the power measured according to the German standard DIN 70020. It is measured at the flywheel, and is in practical terms equivalent to the SAE net figure. However, be aware that DIN "horsepower" may in fact be expressed in PS (Pferdestärke) - see "Metric horsepower" below.

SAE-certified Horsepower In 2005, the Society of Automotive Engineers introduced a new test procedure (J2723) for engine horsepower and torque. The procedure eliminates some of the areas of flexibility in power measurement, and requires an independent observer present when engines are measured. The test is voluntary, but engines completing it can be advertised as "SAE-certified". Metric Horsepower PS This unit (German: Pferdestärke = horse strength) is no longer a lawful unit, but is still commonly used in Europe, South America and Japan, especially by the automotive and motorcycle industry. 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 Physikalische -Technische Bundesanstalt (PTB) [2] in Braunschweig as exactly: 1 PS = 75 kp·m/s = 735.49875 W = 0.9863201652997627 hp (SAE) The PS was adopted by the Deutsches Institut für Normung (DIN), and subsequently, by the automotive industry throughout most of Europe. (In the nineteenth century, however, the French did not use this German unit, but had one of their own, the Poncelet.) In 1992, the PS was rendered obsolete by EEC directives, where it was replaced by the kilowatt as the official power measuring unit, but in situations where horsepower was used for commercial and advertising purposes, it continued to be used, as customers are not familiar with the usage of kilowatts for combustion engines. The European and Japanese automotive industries may use "horsepower" or "hp" (rather than "PS" or "CV", etc.) when referring to metric horsepower in their press-releases or in the media. Summery: Torque (moment of force) Nm (Newton meter) 1 kpm (kilopondmeter) = 9.80665 Nm (Newtonmeter) ~ 10 Nm 1 lbf (pound-force) = 4.44822 Nm 1 pdf (poundal) = 0.138255 Nm = force which accelerates a mass of 1 lb by 1 ft/s². 1 Nm = 0.101972 kp ~ 0.1 kp 1 Nm = 0.224809 lbf 1 Nm = 7.233011 pdl 1 kW = 1.3410 hp or metric 1.3596 PS 1 PS = 0.7355 kW or 0.98632 hp 1 hp = 1.0139 PS or 0.7457 kW The


August 2006

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