Semitrailer

Semi -trailer ,  trailer-dissolution  ( dissolution ) — a vehicle not equipped with an engine and intended for movement in combination with a mechanical vehicle, a non-self-propelled device, like a trailer, which is designed and manufactured for its towing by a vehicle; a kind of trailer, which, with its front part, rests on a tractor.

Semi —  trailer, dissolution trailer  is a vehicle and is designed to transport a variety of goods or equipment on roads of all categories and off-road (separate).

Story

During the development of mankind, the development and improvement of the products used by them took place. So, with the invention of drags, sledges, and later wheels, the means of transporting people and goods were also improved. Hand sledges and a cart that were moved by a man gradually transformed into a wagon, which is already being moved by various animals tamed by man. The carrying capacity of wagons grows in proportion to their size and the number of animals in one team. It is the wagon that the animal pulls that is the prototype of the modern trailer hitch, and later the  semi -trailer  and  dissolution trailer. Later, with the advent of the steam engine and the intensive development of all kinds of machines and mechanisms, steam locomotives and railway trains with various wagons, tractors and cars appeared. During the period of industrial development of mankind, the need for equipment capable of transporting a large amount of goods over long distances on the roads increased, and various  semi -trailers  and  dissolution trailers of  various types and types appeared.

Varieties

Purpose and design

Depending on the nature of operation and body structure,  semi-trailers  are divided into:

• onboard (colloquially, the so-called scow)
• awning
• curtain
• curtain side
• all-metal vans
• isothermal
• refrigerators
• container ships
• dump trucks
• heavy trucks (trawls)
• cisterns
• timber trucks
• semi-trailers for launchers
• tractor semi-trailers
• trailers-dissolutions for the transportation of long material and products (forests, pipes, etc.), connected to the front end with the help of the load itself, consisting of a frame fastened by means of suspension to the axle of the wheels, and a bunk (support beam with folding racks holding the load)
• and so on.

On a semi-trailer towed by a tractor, many specialized installations can also be mounted — for example, a concrete mixer truck, an aerial platform, a garbage truck. But such solutions are much less common than installations on self-propelled chassis.

By region

Currently, semi-trailers can be divided into two large groups: European type and American. Main differences:

• Semi-trailers of the European type, as a rule, have three axles with single tires and disc (for countries with good road surface and relatively warm winters) or drum (in Scandinavia — despite good road infrastructure, due to the abundance of snow in winter, slush during the day and frost at night; in a number of CIS countries — for the same reason and in view of the poor condition of the road network outside of large settlements, a large number of roads without asphalt on the periphery) with brakes. Sometimes one or two bridges can be raised from the ground automatically when driving without a load.
• American semi-trailers have, as a rule, two (rarely three) axles with dual tires and drum (in view of efficiency) brakes; all bridges are involved in the movement and are not lifting.
• European-type semi-trailers, including Russian ones, sometimes have a “pallet box” — a metal box attached to the semi-trailer frame instead of side bumpers, designed to transport pallets. In view of the specifics of cargo transportation in Russia, it is usually used by truck drivers to store spare wheels and other equipment not directly related to cargo transportation.
• American semi-trailers, due to the lack of relevant standards, are often not equipped with side bumpers at all, which creates the danger of a car running under the wheels of a “truck”
• Some refrigerated and isothermal semi-trailers of the American type are made low-bed to increase the volume. This is extremely rare in Europe.
• Also, tent semi-trailers of the American and European type differ in the way and arrangement of the tent.

Hitch mechanism

King pin on a  semi-trailer .

For hitching a semi-trailer with a tractor, there is a support platform with a pivot in the front part of the semi-trailer. The tractor, in turn, has a saddle, which includes a kingpin and on which lies the semi-trailer support platform. In this way, the semi-trailer transfers part of its weight to the tractor. Today, as a rule, backlash-free saddles are used, which exclude knocks and bumps when the road train travels over bumps.