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Motorsport competition form

the human equivalent

Truck and tractor pulling, also known as power pulling, is a form of a motorsport competition in which antique or modified tractors pull a heavy drag or sled along an 35 feet (11 m), 330 feet (101 m) track, with the winner being the tractor that pulls the drag the farthest. Tractor pulling is popular in certain areas of the United States, Mexico, Canada, Europe (especially in the United Kingdom, Greece, Switzerland, Sweden, Netherlands, Belgium, Italy, Denmark and Germany), Australia, Brazil, South Africa, Vietnam, India and New Zealand. 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 drag. When a tractor gets to the end of the 100 meter track, this is known as a "full pull". When more than one tractor completes the course, more weight is added to the drag, and those competitors that moved past 300 feet (91 m) will compete in a pull off; the winner is the one who can pull the drag the farthest. The drag is known as a weight transfer drag. This means that, as it is pulled down the track, the weight is transferred (linked with gears to the drag’s wheels) from over the rear axles and towards the front of the drag. In front of the rear wheels, instead of front wheels, there is a "pan". This is essentially a metal plate, and as the weight moves toward it, the resistance between the pan and the ground builds. The farther the tractor pulls the drag, the more difficult it gets. Tractor pulling originated from pre Industrial Era horse pulling competitions in which farmers would compete with one another to see whose teams of draft horses could pull a heavy load over the longest distance. The first known competitions using motorized tractors were held in 1929 in Missouri and Kentucky. Tractor pulling became popular in rural areas across the Midwestern and Southern United States in the 1950s and 1960s. From there it gradually spread to Canada, Europe, and Australia and New Zealand.

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 in teams with 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 urge his horses to pull the load, with more weight added as 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 draft horses, specially bred to have high strength for pulling heavy loads. Today, fixed weights on drags 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 and Mason Worrell. It wasn't until 1929 that motorized vehicles were put to use in the first events at Bowling Green, Missouri, and Vaughansville, Ohio. 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, turbine engines (frequently mistakenly called "jet engines") appeared in 1974, with Gardner Stone's "General" Tractor a four turboshaft 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 up to and probably would have continued, but the NTPA limited it to 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".

The two wheel drive (2WD) division was introduced in 1983. The division imposes a weight limit of on each competing truck, a maximum width of 8 feet (2 m), and a maximum distance of 15 feet (5 m) from the centerline of the rear axle to the front of the vehicle (including weight racks and tow hook). (The length restriction allows for up to of cosmetic fiberglass, however.) Alcohol methane engines with up to eight cylinders are permitted, but diesel engines are not. Any wheelbase is permitted. The National Tractor Pullers Association restricts engines to and two valves per cylinder. They permit tubular steel frames. The maximum tire size for the 2WD class is , with a maximum circumference of when mounted on an rim and inflated to The ground patch is not to exceed on original tread.

Super Stock tractor Open class uses primarily methanol fuel (some are diesel versions). The Super Stock Open machines can generate over an of torque, with billet or re cast engine blocks. Super Stock Open and Super Stock Diesel tractors may use up to four turbochargers in three stages. The Diesel super stock tractors generate close to and of torque and are allowed to compete in the Open class, which very rarely occurs anymore. However, a true Open (methanol fuel) tractor is not allowed to compete in the Diesel class. There is light Super Stock class which is and the Heavy Super Stock Classes that are
Diesel Pro Stock Tractors are limited to one turbocharger and diesel fuel is the only allowable source for power, in keeping with the 'spirit' of the original tractors. The maximum engine displacement is These engines can achieve around and of torque In recent years, new classes have been created to appeal to different groups of pullers. There is now a class called Limited Pro Stock that is limited to engine and turbocharger. This class typically pulls at and is slightly restricted, as opposed to the Pro Stock class, which can run up to engine and an unrestricted size turbocharger, along with intercoolers. The latest addition to Pro Stocks is the Light Pro Stock Class that typically pulls depending on location. These tractors are limited to engines but can run any size turbo. They are not allowed to run intercoolers, however these tractors are making an average of The light overall weight makes this a driver's class as significant skill is required to keep the tractor on the track. The mini modified class is a highly specialized and custom built tractor to be fitted with a naturally aspirated engine, at minimum. NTPA Minis are limited to (always an aftermarket V 8 engine block) and uses up to a 14 71 hi helix supercharger. With the driver, they weigh only Today's engine is capable of a minimum of on methanol or ethanol. Their reputation is known as the wildest ride in pulling, as naturally it is a very high horsepower to weight ratio. Whereas, their larger counterparts, the Modifieds, will weigh , utilizing the same engine that a Mini has, but, with multiple powerplants per custom built tractor chassis. Usually, a maximum of five engines is all that will make the weight limit. Nitromethane and oxidizers were outlawed in 1976.

Antique tractor pulling is how tractor pulling first got started (although the tractors were just modern tractors at that time). As early as 1929, farmers began attaching their tractors to drags, and dragging it down a field to see who could pull it the furthest. The hitching device can be no more than round stock ( square), or less than round stock ( square), the hole has to be diameter. Another rule which has now been dropped was that a speed limit should be observed because of injuries resulting from the increased speed at which they boarded. Today's tractors can achieve theoretical speeds over
Today's drags use a complex system of gears to move weights up to Upon starting, all the weights are over the drag's rear axles, to give an effective weight of the drag plus zero. As the tractor travels the course, the weights are pushed forward off the drag's axles, pushing the front of the drag into the ground, synthetically creating a gain in weight until the tractor is no longer able to overcome the force of friction.

Apart from modified standard diesel tractors, a variety of high power engines are used in tractor pulling, which started in the late 1970s. In the early years, mainly single, double or multiple US made big block dragster engines were used, but nowadays, a lot of parts from discarded military machinery are in use, like Klimov TV3 117 (Isotov) turboshafts from Russian helicopters, Soviet Zvezda M503 torpedo boat engines, Continental AV1790 tank engines, or World War 2 era aircraft piston engines in V12 shape (e. g. Rolls Royce Griffon) or as radial engines (e. g. Curtiss Wright R 3350). Due to the limited number of vintage warbird engines remaining, some organisations that own them, such as the Fantasy of Flight museum in Florida, refuse to sell engines from their collection to customers that wish to use them for tractor pulling. In recent years a number of agricultural engines have been converted to run on methanol with multi stage turbocharging.