A semi-trailer truck is the combination of a tractor unit and one or more semi-trailers to carry freight. A semi-trailer attaches to the tractor with a fifth-wheel coupling (hitch), with much of its weight borne by the tractor. The result is that both the tractor and semi-trailer will have a design distinctly different from that of a rigid truck and trailer.
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration; smaller varieties may be mechanically similar to some automobiles. Commercial trucks can be very large and powerful and may be configured to be mounted with specialized equipment, such as in the case of refuse trucks, fire trucks, concrete mixers, and suction excavators. In American English, a commercial vehicle without a trailer or other articulation is formally a "straight truck" while one designed specifically to pull a trailer is not a truck but a "tractor".
A road train or land train is a trucking vehicle of a type used in rural and remote areas of Australia, the United States and in Europe to move freight efficiently. It consists of two or more trailers or semi-trailers hauled by a prime mover.
The kingpin, also king-pin and king pin, is the main pivot in the steering mechanism of a car or other vehicle.
A trailer is an unpowered vehicle towed by a powered vehicle. It is commonly used for the transport of goods and materials.
Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion when a body rolls on a surface. It is mainly caused by non-elastic effects; that is, not all the energy needed for deformation of the wheel, roadbed, etc. is recovered when the pressure is removed. Two forms of this are hysteresis losses, and permanent (plastic) deformation of the object or the surface. Another cause of rolling resistance lies in the slippage between the wheel and the surface, which dissipates energy. Note that only the last of these effects involves friction, therefore the name "rolling friction" is to an extent a misnomer.
A tow hitch is a device attached to the chassis of a vehicle for towing, or a towbar to an aircraft nose gear. It can take the form of a tow ball to allow swiveling and articulation of a trailer, or a tow pin, or a tow hook with a trailer loop, often used for large or agricultural vehicles where slack in the pivot pin allows similar movements. Another category is the towing pintle used on military vehicles worldwide.
A dolly is an unpowered vehicle designed for connection to a tractor unit, truck or prime mover vehicle with strong traction power.
An articulated vehicle is a vehicle which has a permanent or semi-permanent pivot joint in its construction, allowing the vehicle to turn more sharply. There are many kinds of articulated vehicles, from heavy equipment to buses, trams and trains. Steam locomotives were sometimes articulated in that the driving wheels could pivot around.
A tractor unit is a characteristically heavy-duty towing engine that provides motive power for hauling a towed or trailered load. These fall into two categories: heavy and medium duty military and commercial rear-wheel drive "semi tractors" used for hauling semi-trailers, and very heavy-duty typically off-road-capable, often 6×6, military and commercial tractor units, including ballast tractors.
A semi-trailer is a trailer without a front axle. In the United States, the term is also used to refer to the combination of a truck and a semi-trailer, a tractor-trailer.
The fifth-wheel coupling provides the link between a semi-trailer and the towing truck, tractor unit, leading trailer or dolly. The coupling consists of a kingpin, a 2-or-3 1⁄2-inch-diameter vertical steel pin protruding from the bottom of the front of the semi-trailer, and a horseshoe-shaped coupling device called a fifth wheel on the rear of the towing vehicle. As the connected truck turns, the downward-facing surface of the semi-trailer rotates against the upward-facing surface of the fixed fifth wheel, which does not rotate. To reduce friction, grease is applied to the surface of the fifth wheel. The configuration is sometimes called a turn-table in Australia and New Zealand, especially if it is a rotating ball-race-bearing type. The advantage of this type of coupling is towing stability.
A motorcycle trailer is either a trailer used to carry motorcycles or one to be pulled by a motorcycle in order to carry additional gear.
Truck classifications are typically based upon the maximum loaded weight of the truck, typically using the gross vehicle weight rating (GVWR) and sometimes also the gross trailer weight rating (GTWR), and can vary among jurisdictions.
A drawbar is a solid coupling between a hauling vehicle and its hauled load. Drawbars are in common use with rail transport, road trailers, both large and small, industrial and recreational, and with agricultural equipment.
The M54 5-ton 6×6 truck (G744) was the basic cargo model of the M39 Series truck. It was designed to transport a 10,000 lb (4,500 kg), 14-foot-long (4.3 m) cargo load off-road in all weather. In on-road service the load weight was doubled.
A car carrier trailer, known variously as a car-carrying trailer, car hauler, auto transport trailer, etc., is a type of trailer or semi-trailer designed to efficiently transport passenger vehicles via truck.
The Mack M123 (G792) was a 10-ton 6x6 semi-tractor introduced in 1955; the Mack M125 was a heavy cargo truck version of the M123. The M123 was used to tow tank transporter trailers while the M125 towed field artillery pieces.
The Autocar Model U8144T, officially "5- to 6-Ton, 4 x 4, Ponton Tractor Truck", was the largest, and most heavy-duty, of a family of heavy four wheel drive trucks developed for, and deployed primarily with, the United States Army in World War II. They were of a "cab over engine" design, and produced by the Autocar Company from 1941 to 1945 with 2,711 being built.
The M809 Series 5-ton 6x6 truck (G908) was a family of heavy tactical trucks built for the United States Armed Forces. The basic cargo version was designed to transport a 5-ton (4,500 kg), 14 ft (4.3 m) long load over all terrain in all weather. In on-road service the load weight was doubled. Built by AM General, they evolved into the M939 Series.
