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Truck and Tractor pulling, also known as power pulling, is a motorsport competition, popular in the United States, Canada, Europe (especially in the Netherlands, Belgium, 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 farthest.
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 farther 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.
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 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 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 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 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 two-wheel drive (2WD) division was introduced in 1983.
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.)
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 575 in3 and two valves per cylinder. They permit tubular steel frames. The maximum tire size for the 2WD class is 18.4 x 16.1, with a maximum circumference of 143 inches when mounted on an 18-inch-wide rim and inflated to 28 psi. The ground patch is not to exceed 19 inches on original tread.
Super Stock Open class uses primarily methanol fuel (some are diesel versions). The Super Stock Open machines can generate over 6,000 horsepower an 4000 ftlbs of tourqe,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 Diesels super stock tractors generate close to 5000hp an 6000ftlbs of tourqe 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 6200 lbs and the Heavy Super Stock Classes that are 8000 - 8250 lbs
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 680 cubic inches. These engines can achieve 3700 or more horsepower and 5500 ftlbs of tourqe 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 640 Cubic inch engine and 4.1" turbocharger. This class typically pulls at 9300 - 9500lbs and is slightly restricted, as opposed to the Pro Stock class, which can run up to 680 cubic inch engine and an unrestricted size turbocharger, along with intercoolers.
The latest addition to Pro Stocks is the Light Pro Stock Class that typically pulls 8300 -8600 lbs depending on location. These tractors are limited to 540 Cubic Inch engines but can run any size turbo. They are not allowed to run intercoolers, however these tractors are making an average of 2500 -2800 horsepower. 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 575 cubic inches (always an aftermarket V-8 engine block) and uses up to a 14-71 hi helix supercharger. With the driver, they weigh only 2050 pounds. Today's engine is capable of a minimum of 2500 horsepower 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 6000, 7500 and 8000 pounds, 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 8000 pound weight limit. Nitromethane and oxidizers were outlawed in 1976.
The first Australian Tractor Pull was held at the Elmore Field Days (Victoria) in 1976. The following year saw Tractor Pulling begin in the Victorian rural town of Quambatook. It has developed over the years into a highly competitive and technical sport, where the difference between first and last place may be as small as one or two metres. Often the top tractors are separated by mere centimetres.
The Australian Tractor Pullers Association (ATPA) is a non-profit organisation that governs Tractor Pulling in Australia. Our events (Tractor Pulls) are held in conjunction with a promoter. This is often a local school, sporting, service or community club (for example; Apex, Rotary, Lions, Netball, Cricket, Football) who use the event as a fundraiser. Tractor Pulls are held in locations throughout Australia, predominantly in Victoria, South Australia and New South Wales. In the west the Western Australian Tractor Pullers Association (WATPA) runs events and is affiliated with the ATPA.
The ATPA is focused on actively promoting this spectacular sport and working with communities to not only establish a unique annual event, but more importantly to assist communities financially through the influx of spectators, sponsors and promotion.
The tractors are divided into classes and comply with either "Limited" or "Open" rules. The classes are Open Modified, Super Modified, Limited Modified, Open Mini Modified, Mini Modified, Pro Stock (diesel) and Two Wheel Drive Trucks. The distinction between classes is determined by the overall maximum weight, engine modifications, fuels and physical size.
Competition is open to both women and men, the only restriction being that competitors must at least hold a current Learner Driver's Permit. It sometimes comes down to members of the same family competing for the trophies.
The Junior Modified Pulling Association conducts an "introductory" class for 8- to 16-year-olds to develop driving, mechanical and competitive skills. The Modified Mowers pull their own smaller version of the big sled.
In the early days two main techniques were used. Either a dead weight of fixed mass was dragged, or the step-on method was used, where people stood at fixed positions and stepped aboard as the sled passed. 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 125 mph/200 km/h.
Today's sleds use a complex system of gears to move weights up to 65,000 pounds/29,000 kilograms. Upon starting, all the weights are over the sled's rear axles, to give an effective weight of the sled plus zero. As the tractor travels the course, the weights are pushed forward of the sled's axles, pushing the front of the sled into the ground, synthetically creating a gain in weight until the tractor is no longer able to overcome the force of friction. Most sleds have grouser bars that act like teeth and dig into the soil to stop the sled.
Radio control truck and tractor pulling has been around since the late 1980s. It was started by a group of people interested in R/C pulling, near Pittsburgh, Pennsylvania, US. The main R/C pulling group is the NR/CTPA. NR/CTPA also has many, smaller, affiliated clubs, such as County Line R/C Puller's Club, club number one in the NR/CTPA.
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.
There are many different organizations with different rules in tractor pulling. Some include:
Possible sources of verification.