TRUCK

also called lorry any motor vehicle designed to carry freight or goods or to perform special services such as fire fighting. The truck was derived from horse-driven wagon technology, and some of the pioneer manufacturers came from the wagon business. Because of their speed and flexibility, trucks have come to carry a quarter of the intercity freight in the United States, and they enjoy an almost total monopoly in intracity freight delivery. In 1896 Gottlieb Daimler of Germany built the first motor truck. It was equipped with a four-horsepower engine and a belt drive with two speeds forward and one in reverse. In 1898 the Winton Company of the United States produced a gasoline-powered delivery wagon with a single-cylinder six-horsepower engine. In World War I motor trucks were widely used, and in World War II they largely replaced horse-drawn equipment. A notable vehicle was the four-wheel-drive, quarter-ton-capacity, short-wheelbase jeep, capable of performing a variety of military tasks. also called Lorry, any of a class of motor vehicles designed to carry freight or heavy articles or to perform special services such as transporting the sick or fire fighting. The first motor truck, built in 1896 by the German automotive pioneer Gottlieb Daimler, had a four-horsepower engine and a belt drive with two forward speeds and one reverse. In 1898 the Winton Company became the first American firm to produce a trucka delivery wagon with a single-cylinder, six-horsepower engine. Trucks came into widespread use in both Europe and the United States during World War I, and by the 1920s they were firmly established as a major means of freight conveyance. Because trucks must transport heavy loads, frequently over long distances, they require powerful engines. The engine of a large truck may have more than 400 horsepower. Until the 1930s gasoline engines were widely used, especially in the United States, but since World War II most large trucks have been equipped with diesel engines. Although diesels can develop more power, they generally operate within a relatively narrow speed range and require transmissions with a greater number of forward speeds. Modern long-distance load haulers may have as many as 16 forward speeds operating in dual-range transmissions. This capability gives the truck both maximum power for climbing hills and maximum speed for freeway driving. There are two basic types of trucks, the straight truck (in which all axles are attached to the frame) and the articulated truck (in which two or more frames are connected by suitable couplings). A common articulated truck consists of a towing truck, or tractor, and a semitrailer equipped with one or more rear axles and constructed so that its front end rests directly on the tractor. The tractor thus carries part of the weight of the semitrailer and its load, while the rear axles of the semitrailer carry the balance of the load. The semitrailer is connected to its tractor by what is called a fifth wheel, which consists of an articulated trunnion (pivot assembly) plate and a latching mechanism mounted on the tractor, into which a kingpin mounted on the semitrailer fits and latches firmly. Truck and tractor frames are usually separate from the body and cab and are built of channel sections of alloy steel. Semitrailers are built with a wide variety of bodies on similar frames, although the integral construction methodin which body structural members are designed to bear the loadis becoming more common. Since 1960 many truck and tractor frames have been built with individual front suspension and with rear suspensions varying according to need. A truck or tractor may have a single or a double powered rear axle, which is attached to the frame by leaf springs. The weight is carried by the axle housings, so that the driving axle bears no load. Until the advent of power steering in the early 1950s, steering a truck required great strength because of the weight of the load and the width of the tires. The Ackermann system, which provides a kingpin for each front wheel and power assist, has greatly relieved this problem. Power steering has also made possible the construction of larger trucks having two steering axles. Four-wheel brakes were introduced in trucks in 1925, seven years after the introduction of air brakes. Most trucks and truck-tractors now have air brakes on all the wheels. The DD3 actuator, an emergency-brake system, applies the brakes after being actuated, and a mechanical lock holds them on even if air pressure is lost. Additional reading G.N. Georgano (ed.), The Complete Encyclopedia of Commercial Vehicles (1979); James William Fitch, Modern Truck Engineering Handbook, 3rd ed., rev. and enlarged (1984); The Truck & Bus Manufacturing Industry: Building the Tools That Move America, 2nd ed. (1983), a brief survey by the U.S. Motor Vehicle Manufacturers Association; John B. Montville, Mack, 2nd ed. (1981), describing a single truck manufacturer; Tom Brownell and Don Bunn, The Heavyweight Book of American Light Trucks, 19391966 (1988); and Andrew Norman and Robert Scharff, Heavy Duty Truck Systems: Electrical, Powertrain, Steering, Suspension, Brake, and Accessory Systems (1991). Terminology is explained in the Society of Automotive Engineers' Truck & Bus Industry Glossary (1988). George C. Cromer