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Truck Tractor

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Transportation Equipment
2002 Kenworth W900 T/A Truck Tractor
A truck tractor, also known as a semi-trailer truck, tractor-trailer or articulated lorry, is designed for transporting goods or freight in the transportation industry. Typically these trucks are classified as heavy-duty trucks, meaning they surpass the gross vehicle weight of 33,000 pounds (15,000 kg).[1] When pulling a trailer, they surpass 80,000 pounds (36,360 kg).[2]

The truck has two basic designs: setback cab and cab-over-engine. Setback cab trucks have a sloped nose that extends up towards the cab, which sits above and behind the engine and front axle. Cab-over-engine (COE) trucks have a vertical front face, which typically provides excellent visibility and shorter overall cab length. However, they are generally much noisier and provide a rougher ride than setback cabs because they sit on top of the engine and front axle. Both types are available as sleepers.

Trailers exist in a wide of variety of different types for different purposes. They are equipped with different numbers of axles and wheels depending on the size and style of the trailer. Still, all these trailers are without a front axle. Instead they have an attached kingpin, which allows them to connect to the truck. The truck’s connecting anchor is called a “fifth wheel coupling.”

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[edit] History

Commercial development of truck tractors began in the 1910s. A truck designer named Charles Martin constructed a gasoline-powered truck-tractor to pull a modified horse-drawn wagon. He also invented a connecting mechanism called a “fifth wheel coupling,” which allowed the trailer to attach to the truck with its kingpin. This was essential for the success of modern truck tractors. The coupler consisted of a round plate with a central hole, which was attached to the rear of the truck tractor frame.

Martin then introduced his Rocking Fifth Wheel coupling, which was able to handle rougher terrain and could articulate at turns. Soon, nearly every truck manufacturer was purchasing Martin’s device and attaching them to their machines.

Sternberg Co., which was based in Wisconsin, began manufacturing cab-over-engine (COE) trucks as early as 1907. However, the first modern COE is attributed to an industrial designer named Viktor Schreckengost. He and fellow engineer Ray Spiller designed the truck for White Motor Co. in 1932. This was an important invention because there were laws restricting the length of vehicles. So, a shorter cab meant more room for a longer trailer, and thus more cargo.

[edit] Features/How it Works

The truck tractor connects to the trailer through a pivot point mounted on the truck, known as the fifth wheel coupling. Both the truck and trailer travel on wheels and axles; however, the number of wheels and axles can vary from model to model.

Most truck tractors are built to order, meaning they are completely customized. However, there are trends that exist in the trucking industry.

2004 Kenworth K104 Aerodyne 6x4 COE Truck Tractor
Typically, North American truck-tractors have three axles with 10 wheels total, two on the front axle and eight on the back two axles. These rear two axles are each equipped with double wheels on each side, but can be replaced by larger single wheels called “super singles.” These single wheels allow for more cargo because they are lighter. They also cover less of the brake unit, which allows the unit to cool quicker. However, if one of them deflates or is defective, the truck is unable to drive to a repair shop.

North American trailers generally have two tandem axles at the rear, each equipped with dual wheels. Most of these trailers have moveable tandems that can be adjusted to balance the weight.

European truck tractors are typically cab-over-engine models. COEs were popular in North America in the 1970s, and they are popular now in European trucking markets because of strict cab measurement laws. European laws require the measurement to begin at the front of the cab, whereas North American laws ignore the cab. These trucks generally have two axles with a total of six wheels—two on the front axle and four on the rear axle.

European trailers usually have three axles with six wheels total—two on each axle.

Truck tractors of all types are typically constructed from steel, aluminum, stainless steel, fiberglass, and molded plastics.

[edit] Common Manufacturers

[edit] References

  1. Heavy Duty Truck. Madehow.com. 2008-09-24.
  2. Heavy Duty Truck. Madehow.com. 2008-09-24.