Tractor Pulling

NTPA

Tractor pulling, also known as ‘power pulling,’ is a motorsport popular in the United States, Canada, Europe, Australia, and Brazil in which modified tractors compete to see which can pull a heavy sled the farthest along a 35 foot wide, 330 foot long track.

The sport is known as the world’s most powerful motorsport, due to the multi-engine, modified tractor pullers, such as those in the 4.5 modified class in Europe that can produce over 10,000 horsepower.

All tractors in their respective classes pull a set weight in the sled. Getting to the end of the track is known as a ‘full pull.’ 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, instead of front wheels, there is a ‘pan,’ which is essentially a metal plate, and as the weight moves toward it the resistance between the pan and the ground builds. Hence, the farther the tractor pulls the sled, the more difficult it gets.

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 with others. 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 hitched to it; weight would be added, usually in the form of rocks, and the driver would ask the horses to pull the load. 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. 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 Vaughansville, Missouri, and Bowling Green, Ohio. Although the sport was recognized then, it did not become widely popular until the ’50s and ’60s. At that time, rules varied from state to state, county to county. In 1969, representatives from eight states congregated to create a uniform book of rules and create the National Tractor Pullers Association (NTPA). In the early years of the NTPA, standard farm vehicles were used and the organization’s motto was: ‘Pull on Sunday, plow on Monday.’

Tractors remained single engine until two Ohio brothers, Carl and Paul Bosse, introduced the crossbox which permitted 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.

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 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.’ The division imposes a weight-limit of 6,200 pounds on each competing truck, a maximum width of eight feet, and a maximum distance of 15 feet 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 ten inches of cosmetic fiberglass, however.)

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