Horsepower is a unit of measurement of power, or the rate at which work is done. There are many different types of horsepower. Two common definitions being used today are the mechanical horsepower, about 745.7 watts, the metric horsepower, 735.5 watts. The term was adopted in the late 18th century by Scottish engineer James Watt to compare the output of steam engines with the power of draft horses, it was expanded to include the output power of other types of piston engines, as well as turbines, electric motors and other machinery. The definition of the unit varied among geographical regions. Most countries now use the SI unit watt for measurement of power. With the implementation of the EU Directive 80/181/EEC on January 1, 2010, the use of horsepower in the EU is permitted only as a supplementary unit; the development of the steam engine provided a reason to compare the output of horses with that of the engines that could replace them. In 1702, Thomas Savery wrote in The Miner's Friend: So that an engine which will raise as much water as two horses, working together at one time in such a work, can do, for which there must be kept ten or twelve horses for doing the same.
I say, such an engine may be made large enough to do the work required in employing eight, fifteen, or twenty horses to be maintained and kept for doing such a work… The idea was used by James Watt to help market his improved steam engine. He had agreed to take royalties of one third of the savings in coal from the older Newcomen steam engines; this royalty scheme did not work with customers who did not have existing steam engines but used horses instead. Watt determined; the wheel was 12 feet in radius. Watt judged. So: P = W t = F d t = 180 l b f × 2.4 × 2 π × 12 f t 1 m i n = 32, 572 f t ⋅ l b f m i n. Watt defined and calculated the horsepower as 32,572 ft⋅lbf/min, rounded to an 33,000 ft⋅lbf/min. Watt determined that a pony could lift an average 220 lbf 100 ft per minute over a four-hour working shift. Watt judged a horse was 50% more powerful than a pony and thus arrived at the 33,000 ft⋅lbf/min figure. Engineering in History recounts that John Smeaton estimated that a horse could produce 22,916 foot-pounds per minute.
John Desaguliers had suggested 44,000 foot-pounds per minute and Tredgold 27,500 foot-pounds per minute. "Watt found by experiment in 1782 that a'brewery horse' could produce 32,400 foot-pounds per minute." James Watt and Matthew Boulton standardized that figure at 33,000 foot-pounds per minute the next year. A common legend states that the unit was created when one of Watt's first customers, a brewer demanded an engine that would match a horse, chose the strongest horse he had and driving it to the limit. Watt, while aware of the trick, accepted the challenge and built a machine, even stronger than the figure achieved by the brewer, it was the output of that machine which became the horsepower. In 1993, R. D. Stevenson and R. J. Wassersug published correspondence in Nature summarizing measurements and calculations of peak and sustained work rates of a horse. Citing measurements made at the 1926 Iowa State Fair, they reported that the peak power over a few seconds has been measured to be as high as 14.9 hp and observed that for sustained activity, a work rate of about 1 hp per horse is consistent with agricultural advice from both the 19th and 20th centuries and consistent with a work rate of about 4 times the basal rate expended by other vertebrates for sustained activity.
When considering human-powered equipment, a healthy human can produce about 1.2 hp and sustain about 0.1 hp indefinitely. The Jamaican sprinter Usain Bolt produced a maximum of 3.5 hp 0.89 seconds into his 9.58 second 100-metre dash world record in 2009. When torque T is in pound-foot units, rotational speed is in rpm and power is required in horsepower: P / hp = T / × N / rpm 5252 The constant 5252 is the rounded value of /; when torque T is in inch pounds: P
Banner Lane was the site of a wartime shadow factory in Coventry, England run by Standard Motor Company and dedicated to making Bristol Hercules aero engines. The war-surplus plant was taken over by Standard in 1946 to make Ferguson tractors and it was made Standard's registered office. After the 1959 sale of Standard's part ownership of the tractor partnership to Massey Ferguson it became Massey Ferguson's base for tractor-building operations until production ceased in 2002 and the site was redeveloped for housing. In May 1939 the Air Ministry sought a facility to manufacture Bristol Hercules aero engines and construction of a plant commenced that year on an 80-acre green-field site just outside Coventry. With over 1 million square feet of floor space, the Banner Lane site was one of the largest shadow factories erected at Government expense, costing £1.7 million to build and set up for production. The new plant luckily missed the summer and autumn 1940 bombing raids of the Coventry Blitz and was functioning before the end of that year.
Its curious similarity to other shadow factories was because the buildings were designed by the Government's own architects. The business was run, for a £40,000 per annum management fee, by Standard Motor Company enabling products and plant to benefit from Standard's expertise in making similar, if much less complex, products. With some of the parts being produced at Rover's shadow factory at Acocks Green, the Hercules engines were complex machines of 38.7 litres capacity having 14 cylinders in two radial rows using sleeve valves rather than poppet valves, with an output of 1,290–1,735 horsepower depending on application. When production ended in 1945 more than 20,000 Hercules engines had been built. Other wartime products managed by Standard but made at Canley, the location of a further shadow factory nearby, included the Bristol Beaufighter and De Havilland Mosquito twin-engined fighter bombers together with a variety of other matériel. After the war the shadow factory was no longer required by Bristol.
However, discussions between Standard and Harry Ferguson in 1945 to build Ferguson tractors in the UK resulted in Standard signing a 10-year lease for the Banner Lane plant costing £36,000 per annum. The intention was to build up to 500 tractors per day for which Standard would receive a fee for each one produced, from mid-1946 until the end of 1947 over 20,800 new tractors had been built. At the height of production over 6,000 people were employed, in 10 years more than 500,000 Ferguson TE tractors had been produced at Banner Lane. Disagreements between Standard and Ferguson culminated in Standard breaking all connections with both Ferguson and tractor production in the summer of 1959. By this time Harry Ferguson Ltd had formed a merger with Massey Harris to become Massey-Harris-Ferguson shortened to Massey Ferguson. All Standard's tractor assets were sold to Massey Ferguson as of 31 August 1959 and Banner Lane entered the sole ownership of Massey Ferguson. By 2000 the plant covered 1.8 million ft2 and tractor output was in excess of 70,000 per annum, the majority for export.
In order to rationalise production it was decided that either Beauvais or Banner Lane would be shut down, but pressure from the French Government and workers made Beauvais the more difficult of the two to close, sealing Banner Lane's fate. Production came to an end on Christmas Eve 2002 when the last tractor, number 3,307,996 was completed; the enormous task of decommissioning, demolition of the plant and site clearance ended with the demolition of the 16-storey tower block on 8 July 2012 using high-explosive charges. And a housing development called Bannerbrook Park now occupies the site on which it has been planned to build in the region of 1,000 new homes, together with an entire infrastructure including shops and a school. A Massey Ferguson memorial to the tractor production facility has been erected on the site. Video made at the time of the demolition of the tower block Aerial photograph of the original factory site illustrating wartime camouflage, taken April 1946
Massey Ferguson Limited is a manufacturer of agricultural equipment, formed by the 1953 merger of farm machinery manufacturers Massey Harris of Canada and the Ferguson Company in Britain. It was based in Brantford, until 1988; the company transferred its headquarters to Buffalo, New York, in 1997, before it was acquired by AGCO, the new owner of its former competitor Allis-Chalmers. Massey Ferguson is one of several brands produced by AGCO and remains a major seller around the world; the company was founded in 1847 in Newcastle, Ontario, by Massey, as the Newcastle Foundry and Machine Manufactory. To begin with it made some of the world's first mechanical threshers, at first by assembling parts from the United States, but designing and building its own equipment. Eldest son, ye Massey, renamed the enterprise the Massey Manufacturing Co. and in 1879 moved it to Toronto, where it soon became one of the city's leading employers. The massive collection of factories, consisting of a 4.4 hectares site with plant and head office at 915 King Street West, became one of the best known features of the city.
Massey began to sell its products internationally. Through extensive advertising campaigns it became one of the most well known brands in Canada. A labour shortage throughout the country helped to make the firm's mechanized equipment attractive. In 1891, Massey Manufacturing merged with A. Son & Co.. Ltd to become Massey-Harris Limited and became the largest agricultural equipment maker in the British Empire. Massey-Harris made threshing machines and reapers as well as safety bicycles, introducing a shaft-driven model in 1898. In 1910 it acquired the Johnston Harvester Company in Batavia, New York, making it one of Canada's first multinational firms. Massey-Harris's early tractor models included the 20 horsepower Massey-Harris GP 15/22, 25 horsepower'Massey-Harris Pacemaker, 35 horsepower Model 101, Massey-Harris Pony, Model 20, Model 81, Model 744. Grain harvesting was revolutionized by Massey engineer Tom Carroll in 1938 with the world's first self-propelled combine – the No. 20. It was too heavy and expensive for extensive mass production, but served as a guide for the design of the lighter and less costly No.
21, tested in 1940 and put on sale in 1941. The Massey-Harris No. 21 Combine was commemorated with a Canada Post stamp on June 8, 1996. E. P. Taylor, one of C. D. Howe's dollar-a-year men, joined the board of directors in 1942, Eric Phillips joined management in 1946; the final generation of Massey-Harris tractors, introduced after World War II, included the 25 horsepower M-H 22 series, the 35 horsepower M-H 33 series, the 45 horsepower M-H 44 series and the 55 horsepower M-H 55 series. In 1952 the M-H 22 was replaced by the M-H 23 Mustang. In 1955 the 30 horsepower Massey-Harris 50 was introduced after the merger that created Massey-Harris-Ferguson, it was based on the Ferguson TO-35 and was produced as the F-40 for Ferguson dealers. The MH-50 was available in several configurations: utility, high-crop utility, or row-crop with a choice of single, tricycle, or wide adjustable front ends. In 1956 the M-H 33 was replaced by the MH 333, the M-H 44 was replaced by the M-H 444 and the M-H 55 was replaced by the M-H 555.
These tractors known as the "triple series", were mechanically similar to their predecessors but featured new styling which included a different hood design, chrome trim on the grill and hood, a different color scheme. They were available with power steering, live PTO and hydraulics; the Massey Harris triple series tractors remained in production until 1958. In a complex turn of events, the Massey family turned to steam engine builder L. D. Sawyer & Company of Hamilton and started a line of steam tractors; these engines were built in a number of sizes. The 25 horsepower was popular, the expanding Prairie provinces clamoured for big breaking engines. Massey experimented with tandem compound engines. Sawyer Massey lasted only until 1910 when the firm was wound down, Massey went into oil engines. Sawyer-Massey and Massey-Harris were two separate companies, both managed by the Massey family. Massey began experimenting with oil engines with engines such as the Bulldog. However, success came only in the 1920s with the Wallis line of tractors, purchased by the firm.
In the 1930s, it introduced the first self-propelled combine harvester. Massey Harris produced one of the world's first four-wheel drive tractors. Hart Massey's sons Charles, Walter and Fred became involved in the business and took over its operations, they were, the last generation of Masseys to run Massey-Harris. Other members of the family went on to other accomplishments: Vincent Massey became Governor General of Canada and Raymond Massey became a noted actor in American films; the Massey family used its fortune to improve the city of Toronto and many institutions, such as the University of Guelph, University of Toronto, Upper Canada College, Crescent School, Appleby College, Massey Hall and Metropolitan United Church, were financed by the Masseys. During and after World War II, Massey Harris undertook a number of contracts to produce tractors and self-propelled artillery vehicles for the U. S. Military. Vehicles produced by Massey Harris include the following: M5 Stuart light tank M24 Chaffee light tank M41 Howitzer Motor Carriage self-propelled artillery M44 Self Propelled Howitzer M36 Jackson tank destroyer M19 Gun Motor Carriage Self-propelled Anti-Aircraft Artillery vehicle (300 buil
The Diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel, injected into the combustion chamber, is caused by the elevated temperature of the air in the cylinder due to the mechanical compression. Diesel engines work by compressing only the air; this increases the air temperature inside the cylinder to such a high degree that atomised Diesel fuel injected into the combustion chamber ignites spontaneously. With the fuel being injected into the air just before combustion, the dispersion of the fuel is uneven; the process of mixing air and fuel happens entirely during combustion, the oxygen diffuses into the flame, which means that the Diesel engine operates with a diffusion flame. The torque a Diesel engine produces is controlled by manipulating the air ratio; the Diesel engine has the highest thermal efficiency of any practical internal or external combustion engine due to its high expansion ratio and inherent lean burn which enables heat dissipation by the excess air.
A small efficiency loss is avoided compared with two-stroke non-direct-injection gasoline engines since unburned fuel is not present at valve overlap and therefore no fuel goes directly from the intake/injection to the exhaust. Low-speed Diesel engines can reach effective efficiencies of up to 55%. Diesel engines may be designed as either four-stroke cycles, they were used as a more efficient replacement for stationary steam engines. Since the 1910s they have been used in ships. Use in locomotives, heavy equipment and electricity generation plants followed later. In the 1930s, they began to be used in a few automobiles. Since the 1970s, the use of Diesel engines in larger on-road and off-road vehicles in the US has increased. According to Konrad Reif, the EU average for Diesel cars accounts for 50% of the total newly registered; the world's largest Diesel engines put in service are 14-cylinder, two-stroke watercraft Diesel engines. In 1878, Rudolf Diesel, a student at the "Polytechnikum" in Munich, attended the lectures of Carl von Linde.
Linde explained that steam engines are capable of converting just 6-10 % of the heat energy into work, but that the Carnot cycle allows conversion of all the heat energy into work by means of isothermal change in condition. According to Diesel, this ignited the idea of creating a machine that could work on the Carnot cycle. After several years of working on his ideas, Diesel published them in 1893 in the essay Theory and Construction of a Rational Heat Motor. Diesel was criticised for his essay, but only few found the mistake that he made. Diesel's idea was to compress the air so that the temperature of the air would exceed that of combustion. However, such an engine could never perform any usable work. In his 1892 US patent #542846 Diesel describes the compression required for his cycle: "pure atmospheric air is compressed, according to curve 1 2, to such a degree that, before ignition or combustion takes place, the highest pressure of the diagram and the highest temperature are obtained-that is to say, the temperature at which the subsequent combustion has to take place, not the burning or igniting point.
To make this more clear, let it be assumed that the subsequent combustion shall take place at a temperature of 700°. In that case the initial pressure must be sixty-four atmospheres, or for 800° centigrade the pressure must be ninety atmospheres, so on. Into the air thus compressed is gradually introduced from the exterior finely divided fuel, which ignites on introduction, since the air is at a temperature far above the igniting-point of the fuel; the characteristic features of the cycle according to my present invention are therefore, increase of pressure and temperature up to the maximum, not by combustion, but prior to combustion by mechanical compression of air, there upon the subsequent performance of work without increase of pressure and temperature by gradual combustion during a prescribed part of the stroke determined by the cut-oil". By June 1893, Diesel had realised his original cycle would not work and he adopted the constant pressure cycle. Diesel describes the cycle in his 1895 patent application.
Notice that there is no longer a mention of compression temperatures exceeding the temperature of combustion. Now it is stated that the compression must be sufficient to trigger ignition. "1. In an internal-combustion engine, the combination of a cylinder and piston constructed and arranged to compress air to a degree producing a temperature above the igniting-point of the fuel, a supply for compressed air or gas. See US patent # 608845 filed 1895 / granted 1898In 1892, Diesel received patents in Germany, the United Kingdom and the United States for "Method of and Apparatus for Converting Heat into Work". In 1894 and 1895, he filed patents and addenda in various
The Ferguson TE20 is an agricultural tractor designed by Harry Ferguson. By far his most successful design, it was manufactured from 1946 until 1956, was known as the Little Grey Fergie, it marked a major advance in tractor design, distinguished by light weight, small size and versatility. The TE20 popularised Harry Ferguson's invention of the hydraulic three-point hitch system around the world, the system became an international standard for tractors of all makes and sizes that has remained to this day; the tractor played a large part in introducing widespread mechanised agriculture. In many parts of the world the TE20 was the first tractor to be affordable to the average farmer and was small and light enough to replace the draft horse and manual labour. Many TE20s remain in regular use in farming and other work and the model is a popular collector's item for enthusiasts today; the model name came from England 20 horsepower. The TE range of Ferguson tractors was introduced in England in 1946, following 30 years of continuous development of'The Ferguson System' from 1916.
The first work was to design a plough and linkage to integrate the tractor with its work in a manner, an engineering whole. The automatic control system is now employed by all tractor manufacturers worldwide. A British patent was granted the following year. By the early 1930s the linkage design was finalised and is now adopted as international standard category I. Just one prototype Ferguson System tractor, known as the Ferguson Black, was built to further technical development and for demonstrating to potential manufacturers. During 1936 the first production Ferguson tractors were built in Huddersfield, Yorkshire, by the David Brown Company; this tractor, the Ferguson Model'A', incorporated Harry Ferguson's'suction side' hydraulic control system, the key to solving sensitive automatic control of three point mounted implements and patented on 5 February 1936. The combination of Ferguson's converging three point hitch, patented on 3 July 1928 with his'suction side control' valve is the key to the success of all subsequent Ferguson and Massey Ferguson'Ferguson System' tractors, the most important of which are the TE and TO 20 models..
In order to get volume production with lower costs, following a demonstration of his tractor before Henry Ford Senior in October 1938, Ferguson made a gentlemen's agreement or referred to as the handshake agreement with Ford to produce the Ferguson tractor in Detroit starting in mid-1939. About 300,000 of these tractors, known as'Ford Fergusons', were produced up to 30 June 1947. During the war years the Ferguson design team developed many improvements to both tractor and implements and started to make arrangements to manufacture in the United Kingdom; the agreement with Ford in 1938 was to include production at the Ford plant at Dagenham, but the UK Ford company would not do it. By 1945 Ferguson had made a manufacturing agreement with the Standard Motor Company of Coventry to produce a Ferguson tractor incorporating all their latest improvements and to be known as the TE20; as well as allowing Ferguson to get his tractor into full production, the deal was of great benefit to Standard as the tractor would be built in its huge'shadow factory', an aero engine plant during World War II but was now standing empty.
Standard developed a new wet-liner engine for the tractor, which would in turn be used in Standard's road cars, such as the Vanguard. Production started in the late summer of 1946, nearly a year before the last Ford Ferguson came off the line in Detroit in June 1947; the break with Ford left his US company with implements to sell but no tractors. To make up the gap until the new Ferguson factory in Detroit started in October 1948, more than 25,000 Coventry-built TE20s were shipped to the USA and Canada; the TO 20 was the same as the TE20 with a Continental engine Z-126 fitted instead of the standard engine. At the time of its introduction the Ferguson three-point linkage was unique to the TE20, to gain the full utility of the tractor the farmer had to purchase specially-designed implements to work with the tractor. Ferguson designed and manufactured a range of implements for the TE20 in-house, but as the tractor's popularity spread other manufacturers began designing their own machinery for the TE20 in agricultural, industrial and horticultural applications.
The idea that the three-point linkage made the tractor and its implement into a single mechanised unit was marketed as'The Ferguson System', presenting a wholly new and mechanised form of agriculture. By 1950 there were over 60 official Ferguson implements for the TE20, many of which had not been seen in mechanised tractor-mounted form before; as well as basic implements such as ploughs and cultivators the range included a number of trailers and loaders, seed drills, a side-mounted baler, a rare'wraparound' combine harvester, a muck spreader, a sickle mower and a powered auger. With its Power take-off the tractor could drive stand-alone equipment by belt or driveshaft, such as pumps, milking machinery or circular saws. Ferguson became well-known for its effective and distinctive advertising, intended to demonstrate the abilities of the TE-20 tractor to farmers who had used only draft horses and had little experience with mechanised equipment. Public demonstrations of Ferguson tractors and implements were held throughout rural Britain towards the end of the h
Agriculture is the science and art of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to live in cities; the history of agriculture began thousands of years ago. After gathering wild grains beginning at least 105,000 years ago, nascent farmers began to plant them around 11,500 years ago. Pigs and cattle were domesticated over 10,000 years ago. Plants were independently cultivated in at least 11 regions of the world. Industrial agriculture based on large-scale monoculture in the twentieth century came to dominate agricultural output, though about 2 billion people still depended on subsistence agriculture into the twenty-first. Modern agronomy, plant breeding, agrochemicals such as pesticides and fertilizers, technological developments have increased yields, while causing widespread ecological and environmental damage. Selective breeding and modern practices in animal husbandry have increased the output of meat, but have raised concerns about animal welfare and environmental damage.
Environmental issues include contributions to global warming, depletion of aquifers, antibiotic resistance, growth hormones in industrial meat production. Genetically modified organisms are used, although some are banned in certain countries; the major agricultural products can be broadly grouped into foods, fibers and raw materials. Food classes include cereals, fruits, meat, milk and eggs. Over one-third of the world's workers are employed in agriculture, second only to the service sector, although the number of agricultural workers in developed countries has decreased over the centuries; the word agriculture is a late Middle English adaptation of Latin agricultūra, from ager, "field", which in its turn came from Greek αγρός, cultūra, "cultivation" or "growing". While agriculture refers to human activities, certain species of ant and ambrosia beetle cultivate crops. Agriculture is defined with varying scopes, in its broadest sense using natural resources to "produce commodities which maintain life, including food, forest products, horticultural crops, their related services".
Thus defined, it includes arable farming, animal husbandry and forestry, but horticulture and forestry are in practice excluded. The development of agriculture enabled the human population to grow many times larger than could be sustained by hunting and gathering. Agriculture began independently in different parts of the globe, included a diverse range of taxa, in at least 11 separate centres of origin. Wild grains were eaten from at least 105,000 years ago. From around 11,500 years ago, the eight Neolithic founder crops and einkorn wheat, hulled barley, lentils, bitter vetch, chick peas and flax were cultivated in the Levant. Rice was domesticated in China between 11,500 and 6,200 BC with the earliest known cultivation from 5,700 BC, followed by mung and azuki beans. Sheep were domesticated in Mesopotamia between 11,000 years ago. Cattle were domesticated from the wild aurochs in the areas of modern Turkey and Pakistan some 10,500 years ago. Pig production emerged in Eurasia, including Europe, East Asia and Southwest Asia, where wild boar were first domesticated about 10,500 years ago.
In the Andes of South America, the potato was domesticated between 10,000 and 7,000 years ago, along with beans, llamas and guinea pigs. Sugarcane and some root vegetables were domesticated in New Guinea around 9,000 years ago. Sorghum was domesticated in the Sahel region of Africa by 7,000 years ago. Cotton was domesticated in Peru by 5,600 years ago, was independently domesticated in Eurasia. In Mesoamerica, wild teosinte was bred into maize by 6,000 years ago. Scholars have offered multiple hypotheses to explain the historical origins of agriculture. Studies of the transition from hunter-gatherer to agricultural societies indicate an initial period of intensification and increasing sedentism. Wild stands, harvested started to be planted, came to be domesticated. In Eurasia, the Sumerians started to live in villages from about 8,000 BC, relying on the Tigris and Euphrates rivers and a canal system for irrigation. Ploughs appear in pictographs around 3,000 BC. Farmers grew wheat, vegetables such as lentils and onions, fruits including dates and figs.
Ancient Egyptian agriculture relied on its seasonal flooding. Farming started in the predynastic period at the end of the Paleolithic, after 10,000 BC. Staple food crops were grains such as wheat and barley, alongside industrial crops such as flax and papyrus. In India, wheat and jujube were domesticated by 9,000 BC, soon followed by sheep and goats. Cattle and goats were domesticated in Mehrgarh culture by 8,000–6,000 BC. Cotton was cultivated by the 5th-4th millennium BC. Archeological evidence indicates an animal-drawn plough from 2,500 BC in the Indus Valley Civilisation. In China, from the 5th century BC there was a nationwide granary system and widespread silk farming. Water-powered grain mills were in use followed by irrigation. By the late 2nd century, heavy ploughs had been developed with iron mouldboards; these spread westwards across Eurasia. Asian rice was domesticated 8,200–13,500 years ago – depending on the molecular clock estimate, used – on the Pearl River in southern China with a single genetic origin from the wild rice Oryza rufipogon
Four-wheel drive called 4×4 or 4WD, refers to a two-axled vehicle drivetrain capable of providing torque to all of its wheels simultaneously. It may be full-time or on-demand, is linked via a transfer case providing an additional output drive-shaft and, in many instances, additional gear ranges. A four-wheeled vehicle with torque supplied to both axles is described as "all-wheel drive". However, "four-wheel drive" refers to a set of specific components and functions, intended off-road application, which complies with modern use of the terminology. 4WD systems were used in many different vehicle platforms. There is no universally accepted set of terminology to describe the various architectures and functions; the terms used by various manufacturers reflect marketing rather than engineering considerations or significant technical differences between systems. SAE International's standard J1952 recommends only the term All-Wheel-Drive with additional sub classifications which cover all types of AWD/4WD/4x4 systems found on production vehicles.
Four-by-four or 4x4 is used to refer to a class of vehicles in general. Syntactically, the first figure indicates the total number of wheels, the second indicates the number that are powered. So 4x2 means a four-wheel vehicle that transmits engine torque to only two axle-ends: the front two in front-wheel drive or the rear two in rear-wheel drive. A 6×4 vehicle has three axles, two of which provide torque to two axle ends each. If this vehicle were a truck with dual rear wheels on two rear axles, so having ten wheels, its configuration would still be formulated as 6x4. During World War II, the U. S. military would use spaces and a capital'X' – like "4 X 2" or "6 X 4". Four-wheel drive refers to vehicles with two axles providing torque to four axle ends. In the North American market the term refers to a system, optimized for off-road driving conditions; the term "4WD" is designated for vehicles equipped with a transfer case which switches between 2WD and 4WD operating modes, either manually or automatically.
All-wheel drive was synonymous with "four-wheel drive" on four-wheeled vehicles, six-wheel drive on 6×6s, so on, being used in that fashion at least as early as the 1920s. Today in North America the term is applied to both heavy vehicles as well as light passenger vehicles; when referring to heavy vehicles the term is applied to mean "permanent multiple-wheel drive" on 2×2, 4×4, 6×6 or 8×8 drive train systems that include a differential between the front and rear drive shafts. This is coupled with some sort of anti-slip technology hydraulic-based, that allows differentials to spin at different speeds but still be capable of transferring torque from a wheel with poor traction to one with better. Typical AWD systems are not intended for more extreme off-road use; when used to describe AWD systems in light passenger vehicles, it refers to a system that applies torque to all four wheels and/or is targeted at improving on-road traction and performance, rather than for off-road applications. Some all-wheel drive electric vehicles solve this challenge using one motor for each axle, thereby eliminating a mechanical differential between the front and rear axles.
An example of this is the dual motor variant of the Tesla Model S, which on a millisecond scale can control the torque distribution electronically between its two motors. Individual-wheel drive is used to describe electric vehicles with each wheel being driven by its own electric motor; this system has inherent characteristics that would be attributed to four-wheel drive systems like the distribution of the available torque to the wheels. However, because of the inherent characteristics of electric motors, torque can be negative, as seen in the Rimac Concept One and SLS AMG Electric; this can have drastic effects, as in better handling in tight corners. The term IWD can refer to a vehicle with any number of wheels. For example, the Mars rovers are 6-wheel IWD. Per the SAE International standard J1952, AWD is the preferred term for all the systems described above; the standard subdivides AWD systems into three categories. Part-Time AWD systems require driver intervention to couple and decouple the secondary axle from the driven axle and these systems do not have a center differential.
The definition notes. Full-Time AWD systems drive both rear axles at all times via a center differential; the torque split of that differential may be fixed or variable depending on the type of center differential. This system can be used on any surface at any speed; the definition does not address exclusion of a low range gear. On-Demand AWD systems drive the secondary axle via an active or passive coupling device or "by an independently powered drive system"; the standard notes that in some cases the secondary drive system may provide the primary vehicle propulsion. An example is a hybrid AWD vehicle where the primary axle is driven by an internal combustion engine and secondary axle is driven by an electric motor; when the internal combustion engine is shut off the secondary, electrically driven axle is the only driven axle. On-demand systems function with only one powered axle until torque is required by the second axle. At that point either a passive or active coupling sends torque to the secondary axle.
In addition to the above primary classifications the J1952 standard notes seconda