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Truck and Tractor pulling, also known as ''power pulling'', is a motorsport competition, popular in United States, Europe (especially in the Netherlands, Denmark and Germany), Australia and Brazil, and New Zealand which requires modified tractors to pull a heavy sled along a 35 foot wide, 330 foot long track, with the winner being the tractor that pulls the sled the farthest. The sport is known as the world's most powerful motorsport, due to the multi-engined modified tractor pullers. All tractors in their respective classes pull a set weight in the sled. When a tractor gets to the end of the 100 metre track, this is known as a "full pull". When more than one tractor completes the course, more weight is added to the sled, and those competitors that moved past 300 feet will compete in a pull-off; the winner is the one who can pull the sled the furthest. The sled is known as a ''weight transfer sled''. This means that as it is pulled down the track, the weight is transferred (linked with gears to the sled’s wheels) from over the rear axles and towards the front of the sled. In front of the rear wheels, there is a "pan". This is essentially a metal plate and as the weight moves over this the resistance builds. The further the tractor pulls the sled, the more difficult it gets. The most powerful tractors, such as those in the 4.5 modified class in Europe, can produce over 10,000 horsepower. ==History in the US== Prior to the invention of the tractor, when farm implements were pulled by horses, farmers would boast about the strength of their teams and seek to compare and contest against one another to see who had the most powerful animals. In some cases they compared horse teams pulling large loads over distance, such as a fully loaded hay cart or wagon. In other situations, a flat board or skid would have a horse or team of horses then hitched to it; weight would be added, usually in the form of rocks, and the driver would ask the horses to pull the load, with more weight added and competitors were eliminated; the animals pulling the most weight or for the greatest distance were judged the strongest. These events became the formalized sport of horse pulling, which is still carried out today with specially bred draft horses bred to have high strength for pulling heavy loads. Today, fixed weights on sleds are dragged for a set distance and additional weight is added in successive rounds. While it is said that the term horsepower is derived from this event, the concept was developed earlier, in experiments and measurements performed by James Watt. It wasn't until 1929 that motorized vehicles were put to use in the first events at Vaughansville, Missouri, and Bowling Green, Ohio, the latter being where the current national championships are held. Although the sport was recognized then, it did not really become popular until the '50s and '60s. It was also realized, at that time, there were no uniform set of rules. The rules varied from state to state, county to county, and competitors never knew what standards to follow. This made the sport difficult for new entrants. In 1969, representatives from eight states congregated to create a uniform book of rules to give the sport the much needed structure, and created the National Tractor Pullers Association (NTPA). The NTPA's early years were events that used standard farm vehicles, with the motto "Pull on Sunday, plow on Monday". Pulling remained basically the same through the '70s, with only stock and modified tractors. Stock tractors were commercially available tractors produced by manufacturers, and modified tractors were the basic tractor chassis with another non-tractor engine mounted on it. Tractors remained single engine until two Ohio brothers, Carl and Paul Bosse, introduced the crossbox which could allow multiple engines to be attached to a single driveshaft. Other innovators during this period included Bruce Hutcherson, with his triple Rodeck engine powered "Makin Bacon Special", Dave and Ralph Banter and their Chevrolet powered tractors, and the "Mission Impossible" tractors of Tim Engler, which at one point had up to seven blown alcohol engines on board. Subsequently, modified tractors with four engines were common, while stock tractors tried to catch up by adding multiple large turbochargers, along with intercoolers, but both retained the appearance of a tractor. Soon tractors became single-use machines that were not used on the farm, making the "Pull on Sunday, plow on Monday" motto obsolete. Throughout the '70s and '80s the modified division continued to thrill crowds by adding more engines, and soon the tractors lost their tractor appearance and turned into high 'spec' dragsters. The limit was reached in 1988 when a tractor with seven engines was built. As well as piston engines, jet engines appeared in 1974, with Gardner Stone's "General" Tractor a four-jet-engined unit hitting the hook in 1989. The growing popularity of the sport caused the creation of a new four-wheel drive division in 1976, which captured a large fan base. The engine sizes in these vehicles continued to increase, from 450 cubic inches/7.3 liters up to 700/11.5 and probably would have continued, but the NTPA limited it to 650/10.6 naturally aspirated and no blown engine in 1989. Today the 4-wheel drive division is one of the most popular with the success of trucks like the Holman Brothers "4-Play" Chevy and Bob Boden's "Studley Studebaker". 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Tractor pulling」の詳細全文を読む スポンサード リンク
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