What Is Tractor Pulling

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What Is Tractor Pulling

Tractor pulling is commonly referred to as “The World’s Heaviest Motorsport,” and for good reason. With the heaviest tractor class weighing in at 20,000 pounds, nothing else in motorsports comes close. And while most other motorsports focus on speed, tractor pulling is all about distance. 

If you’re ready for a crash-course in this unique sport, we tasked our resident racing fanatic at Printed Kicks to deliver the details. Be sure to buckle up; it’s going to be a bumpy ride.

Environment

Basketball has a court, wrestling and boxing have a ring, and tractor pulling has a pulling track. With a setup not unlike other motorsports, fans gather in a packed arena to watch their favorite tractors compete on a prescribed course.

The goal is for each competitor to successfully drag a metal sled as far as their tractor will allow. This metal sled isn’t your average sled, however. On it is a box that contains weight, which is mechanically winched to pull forward as the sled proceeds through the course.

As such, the weight becomes heavier and heavier, eventually proving to be too much for the tractor attempting to pull it. In some rare cases, there have been tractors capable of pulling the metal sled through the course’s entire length. 

To do this is called a “full pull,” and although uncommon, it can be done. In the event that there are two full-pull winners in a single competition, a “pull-off” takes to determine the one true champion. 

Because the difference between winning and losing can come down to a fraction of an inch, that’s exactly how tractor pulling measures its competitions. Measured in thousandths of an inch from start to finish, this can result in some truly close calls.

Equipment

At first glance, you’d be forgiven for thinking competition tractors are simply standard-issue farm equipment. However, closer inspection will reveal that any similarities start and stop with the tractors’ tires and body. 

The sport of tractor pulling is all about the horsepower and torque that’s “under the hood.” As such, competition tractors need to have a modified engine that’s capable of generating as much power as possible. 

Because there are so many different tractors and modification options, various classes have been formed. These classes serve to rank tractors based on limitations in the rules. For example, modified tractor limits are largely based on weight, while engines can include jet turbines, drag racing automotive type, and aircraft and industrial engines in a variety of configurations. 

Trucks range between two- and four-wheel drive and semis. Moreover, four-wheel-drive trucks are either naturally aspirated, blown, or diesel.

Class

Let’s now move on to the many different classes that make up tractor pulling. As you can probably imagine, there are a seemingly endless array of configurations due to so many vehicle types and possible modifications.

Modified Tractor

What initially started as common farm tractors with non-tractor engines eventually exploded into fully customized machinery, some with multiple engines and power plants. Every division in the Modified class uses a maximum of 30.5 x 32 tires and a 20-inch drawbar.

The drawbar is what the metal sled attaches, so there are limitations on what kind can be used depending on the class.

Modified (RN)

Specifications:

  • A combination of NTPA-recognized turbine engines (cannot exceed 5,050 total horsepower)
  • Either one or two Allison aircraft engines (based on blower type)
  • One marine or industrial engine with a 12-cylinder limit
  • Three blown automotive engines with 8-71 blowers
  • Two blown automotive engines with 14-71 blowers
  • 7,500 pounds

Light Unlimited (GN)

Specifications:

  • 6,000 pounds
  • No turbines

Modified (GN)

Specifications:

  • A combination of NTPA-recognized turbine engines (cannot exceed 5,800 total horsepower)
  • Two marine or industrial engine with a 12-cylinder limit
  • Three blown automotive engines with 14-71 blowers
  • Four blown automotive engines with 8-71 blowers
  • Two Allison aircraft engines
  • 7,500 pounds

Unlimited (GN)

Specifications:

  • 8,000 pounds (can use any power plant that makes weight)

Super Stock Tractors

Specifications:

  • Diesel- or alcohol-powered
  • Multiple turbochargers

Heavy Super Stock tractors that are performing at the Regional level run a 20-inch drawbar. Alcohol-powered tractors can weigh in at 8,000 pounds, while diesel-powered is 8,300 pounds. 

Light Super Stock Tractors performing at the RN level only run component tractors at 6,200 pounds, while agricultural rear-end tractors are at 6,500 pounds. 

Diesel fuel only and Grand National Open (Alcohol) tractors use a 20-inch drawbar and weigh 8,000 pounds, while the Grand National Light Super Stock class uses a mixture of fuels and runs at 6,200 pounds.

Pro Stock Tractors

Specifications:

  • Single turbocharger (diesel only) tractor class
  • Intercoolers/Water injection allowed
  • 680 cubic-inch displacement limit
  • One turbocharger
  • 20-inch drawbar
  • 10,000 pounds
  • 24.5 x 32 tires

Light Pro Stock Tractors

Specifications:

  • OEM agricultural-type engine heads (no billet)
  • “P” pump (only 3000 or 7100 series)
  • Includes rules from Pro Stock class
  • Component chassis prohibited
  • Inner/aftercoolers prohibited
  • Overhead cams prohibited
  • Only one plunger/cylinder
  • 8,500 pounds
  • 540 cid limit

Limited Pro Stock Tractors

Specifications:

  • OEM agricultural-type engine heads (no billet)
  • Turbo limit: smooth-bore 4.1 inlet housing
  • “P” pump (only 3000 or 7100 series)
  • Includes rules from Pro Stock class
  • Component chassis prohibited
  • Maximum two valves/cylinder
  • Inner/aftercoolers prohibited
  • Overhead cams prohibited
  • 9,500 pounds
  • 640 cid limit

Super Farm Tractors

Specifications:

  • Tractor class limited to single turbocharger diesel only 
  • One turbocharger 3x3 (sealed after inspection)
  • Water-injection “P” pump allowed
  • 640 cubic-inch displacement limit
  • Inner/aftercoolers prohibited
  • Overhead cams prohibited
  • 20-inch drawbar
  • 24.5 x 32 tires
  • 9,300 pounds

Modified Mini Tractors

Specifications:

  • 650 cid or 575 cid blown (naturally aspirated limits)
  • Turbines limit: NTPA 1,800 horsepower
  • Turbine or automotive-style engines
  • 18-inch drawbar
  • 18.4 x 16.1 tires
  • 2,050 pounds

Four Wheel Drive Trucks

Specifications:

  • 20-inch-wide rim and 112-inch circumference tire limit
  • 650 cid (naturally aspirated engine)
  • Stock-appearing 4x4 truck
  • 26-inch drawbar
  • 6,200 pounds

Super Modified Four Wheel Drive Trucks

Specifications:

  • 20-inch-wide rim and 112-inch circumference tire limit
  • 500 cid (turbocharged or supercharged engine)
  • Stock-appearing 4x4 truck
  • 26-inch drawbar
  • 6,200 pounds

Diesel Pro-Stock Four Wheel Drive Trucks

Specifications:

  • Stock-appearing 4x4 truck (includes most street class)
  • 460 cid limit (max 3-inch turbocharger)
  • DOT tires (maximum 35-inch)
  • 26-inch drawbar
  • Diesel fuel only
  • 8,000 pounds
  •  “P” pump

Super Stock Diesel Four Wheel Drive Trucks

Specifications:

  • Tires: Max 35 inches tall (tread cannot exceed 18 inches)
  • Two-stage turbocharger configuration limit 
  • Stock-appearing 4x4 truck
  • Water-injection allowed
  • 26-inch drawbar
  • Diesel fuel only
  • 7,500 pounds
  • 460 cid limit
  •  “P” pump

Two-Wheel Drive Trucks

Specifications:

  • Supercharged or turbocharged engines
  • 30-inch drawbar
  • 18.4 x 16.1 tire
  • 6,200 pounds 
  • 575 cid limit
  • Alcohol fuel
  • Truck body

Super Semi

Specifications:

  • Production-available commercial truck engine only (minimum 500 units produced)
  • Stock-appearing semi (single or multiple turbochargers) 
  • Maximum turbocharger system: two stages of pressure
  • DOT-approved tires
  • 16-inch drawbar
  • Diesel fuel only
  • 20,000 pounds

Pro Stock Semi

Specifications:

  • Production-available commercial truck engine only (minimum 500 units produced)
  • Stock-appearing semi (single turbocharger)
  • One turbocharger (any size)
  • DOT-approved tires
  • 16-inch drawbar
  • Diesel fuel only
  • 20,000 pounds

The Sled

Now that you know what kind of tractors you’ll see at a tractor pull, it’s time to take a closer look at the metal sled they’ll be pulling. 

In the infancy of tractor pulling, they didn’t have the sophisticated weight system used today. Instead, various fixed weights were used to test a tractor’s mettle. In some instances, people would actually stand on the sled to provide more weight.

Modern sleds are capable of moving up to 65,000 pounds of weights. At the start of a competition, the weights start just over the sled’s axles. But as the tractor pulls, the weights transition ahead of the axles. This is done in order to cause the sled to dip, thus dragging the front into the ground.

This serves to create more resistance, thereby providing synthetic weight. This continues until the tractor can no longer pull the sled.

Let’s look at the various components that make up the metal sled.

Sled Operator

Maintains control and safety of the sled at all times. If the operator believes there to be a problem, they can pull the kill switch.

Kill Switch and Hook

Emergency shut-off that instantly kills the sled. 

Box

Houses the weight used to stop the tractor.

Weight Block

Most sleds have a full block (2,000 pounds) and a half block (1,000 pounds).

Pan

Creates friction by applying force to the weight. This friction increases as the tractor advances through the course.

Trip

Responsible for starting the push-down system that slows the tractor.

Push-Down System

Comprised of hydraulic cylinders that lift the back half of the sled.

Summary

Tractor pulling has technically been around for over 100 years. However, it didn’t become a popular sport until the 1950s. Although technology has progressed exponentially since its inception, the premise has remained the same.

With the advent of more powerful tractors, the excitement of competition is at an all-time high. Tractor pulling can be seen all across the United States, with fans scattered everywhere. As machinery continues to advance and innovate, tractor pulling is sure to follow suit.

 

Sources

What is Tractor Pulling? - Pulling 101 | NTPA Pull

NTPA Pull | NTPA Hall of Fame Inductees

Tractor Pulling during the 1950s and 60s | Living History Farm


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