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truck,automotive vehicle designed primarily for the transportation of goods. A truck is constructed on the general lines of the automobile but uses larger and heavier parts. It may be powered by a gasoline internal-combustion engine or a diesel engine. In some trucks propulsion is supplied through a single front or rear axle, in others through two rear axles, and in still others through both front and rear axles. Many trucks have automatic or semiautomatic transmissions. Smaller trucks are built as a single unit, but larger trucks are frequently combinations of a truck tractor, which contains an engine, transmission, and cab, and a semitrailer, which is a trailer that the tractor hauls. The semitrailer has no forward axle, so that its front end must be supported by a swivel mount, known as the fifth wheel, which is found on the rear of the truck tractor. A full trailer, which can be attached to the rear of a semitrailer, has a front axle and one or two rear axles. In other countries, such as Australia, as many as three trailers may be attached to a single tractor. In the United States most states place restrictions on the length of trucks, on the maximum weight that may be carried on a single axle, and on the addition of trailers, though some states still allow up to three trailers. Despite these restrictions, truck traffic accounts for ever-larger percentages of accidents and road damage. As common carriers, motor trucks have made serious inroads on the earnings of the railroads as they carry freight over increasingly long distances. In Asia and Africa, they have replaced the camel caravan and human carriers.
any of several types of motor vehicle, differing in load-carrying capacity, body type, wheel arrangement, and arrangement of the principal components, particularly of the cab in relation to the front axle. The maximum allowed weight of a trailer is indicated in the load-carrying capacity of the truck. For towing, the truck is outfitted with towing equipment (fifth wheel) and convenient connections to the trailer’s turn-signal and braking systems.
Trucks are classified according to load-carrying capacity into very small, to 1 ton; small, I to 2 tons; medium, 2 to 5 tons; large, over 5 tons; and very large, which includes off-road trucks with load capacities exceeding limits set by the road clearances and road weight limits for trucks. For traffic safety on the roads and in the cities the length of a two-axle truck may not exceed 11 m. Trucks with more than two axles are limited to 12 m. and trucks with one or more full trailers are limited to a maximum of 22 m. None may exceed 2.5 m in width and 3.8 m in height. Higher load-carrying capacity may be achieved by increasing the number of axles (to three and four axles) or by using trailers or semitrailers. In the USSR the following load-carrying capacities are recommended for trucks and trailers: 0.5. I. 1.5, 3. 5. 8, 10, 12, 14, 16, 25. 40. 60. and 100 tons.
There are general-purpose and specialized trucks. The general-purpose trucks have a loading platform with a tail gate and removable side walls. The specialized trucks (including dump, van, and refrigerator trucks) have bodies designed for special purposes. Trucks and trailers with specialized bodies are usually adapted to carry one cargo or several similar cargos: these trucks include moving vans, gasoline tankers, cement-mixer trucks, timber carriers, cement carriers, and container carriers. To reduce loading and unloading effort some trucks are equipped with various power systems for lifting and lowering cargo, moving the body or back gate and sides, rearranging and moving the cargo within the body of the carrier, or performing other operations. Trucks are constructed with emphasis on the concept of component systems, including such components as engines, transmissions, running gear, and steering. The most common truck systems have the cab behind the engine or the cab over the engine. The latter is popular especially among the trucks of larger load capacity, because of its more correct weight distribution in relation to its axles both in the loaded and empty condition. It also provides the longest load-carrying platform for total truck length. For the more complete matching of the truck to a load, a model is usually issued in several wheel-base lengths. The chassis with the shortest wheelbase is used for dump trucks, which move loose, large-volume loads, and for tractor-trailer power units. Chassis with long wheelbases are used for large truck bodies, which provide good load-carrying properties even with light but bulky loads.
Trucks with a particularly small load capacity (vans and pickups) are usually built on a passenger car chassis or on their partial assemblies. Trucks of small to medium load capacity usually use carbureted gasoline engines, transmissions with single or dual-range final drives, hydraulic or hy-dropneumatic brakes, leaf spring suspensions both front and back, and no power steering. Trucks of large and extra large load capacity are usually equipped with diesel engines, mechanical, hydromechanical or electromechanical transmissions, pneumatic or pneumohydraulic brakes with braking-rate retarders, and hydraulically assisted steering.
The principal characteristics of several Soviet trucks are shown in Table 1.
In the USSR trucks are made in several motor-vehicle plants, including the Ul’ianov (UAZ), Gorky (GAZ), Moscow (ZIL), Urals (Ural), Minsk (MAZ), Kutaisi (KAZ), Kremenchug (KrAZ), and Byelorussia (BelAS) plants.
The basic models built by these plants include the UAZ-451 DM (load-carrying capacity of 1 ton), GAZ-53A (4 tons), ZIL-130 (5 tons), Ural-377 (7.5 tons), MAZ-500 (8 tons), KAZ-608 (tractor trailer power unit), and KrAZ-257 (12 tons). These form the basis for many modified types, including dump trucks, cross-country trucks, and tractor-trailers. The Byelorussia motor-vehicle factory builds quarry dump trucks of particularly large capacity, including the BelAZ-540 (27 tons), BelAZ-548 (40 tons), and BelAZ-549 (65 tons).
The trend of truck development is toward further adaptability to the special needs of operating conditions. For trucks of small and medium load capacity attention is particularly directed toward greater maneuverability and acceleration and reduced height in relation to load. For the trucks of large load capacity the trend is toward maximizing the load-carrying capacity within the existing weight limitations. Effort is also directed toward ensuring docking maneuverability of systems in which the trailer is as big as the truck itself. In power units, more powerful and economical engines of lighter weight are being developed. High speed diesel engines are enjoying increasing popularity. Trucks of large capacity are being considered for gas turbine application. The use of atom power (atomvehicle) is difficult because of need for complicated physiological shielding.
Automatic transmissions and diesel-electric transmission with electric motor drives on each wheel (motor-wheel) are beginning to be used somewhat more widely. Their use reduces the pollution of city air with toxic substances of combustion products. Much attention is given to the reduction of steering effort (power steering), traffic safety (improved brakes, visibility, and signaling), reduction of labor-intensive work in maintenance and repair, and the improvement of the reliability of the truck structure.
REFERENCESAfanas’ev, L. L. Avtomohil’nye perevozki. Moscow, 1965.
Avtomobilestroenie SSSR. Moscow, 1967.
Anokhin. V. I. Otechestvennve avtomobili, 3rd ed. Moscow. 1968.
|Table 1. Truck characteristics|
|Load capacity of truck|
|up to 1.0||1.5||3||5||8||12|
|Minimum width of truck deck (mm).............||–||1,900||2,200||2,200||2,200||2,200|
|Minimum length of truck deck (mm)............||–||3,000||3,800||4,500||5,200||7,000|
|Maximum loading height (mm)..................||900||1,150||1,200||1,200||1,400||1,400|
|Minimum clearance (mm).......................||175||200||240||260||270||270|
|Acceleration to 50 km/hr (sec)...............||15||15||15||25||25||35|
|Maximum speed (km/hr)........................||110||100||90||90||85||75|
|Size of tires (inches).......................||600–13||8.40–15||7.00–18||7.50–20||8.25–20||11.00–20|
Milushkin, A. A. Tekhniko-ekspluatatsionnye trebovaniia k perspek-tivnomu gruzovomu podvizhnomu sostavu avtomobil’nogo transporta. Moscow, 1968.
Velikanov, D. P. Effektivnost’ avtomobilia. Moscow, 1969.
Chagette, J. Technique automobile, 3rd ed. Paris, 1953.
L. L. AFANAS’EV