Semi-Trailers — Vehicles with a Coupling Mechanism

One of the types of transport equipment involved in cargo transportation is semi-trailer. These mechanisms are designed to operate with a tractor in order to transport various goods, as well as to increase the scope of products transported within one trip.

Characteristic Features and Varieties of Semi-Trailers

A semi-trailer is a type of non-self-propelled vehicle — a trailer differing from it by presence of rear axles only, and rests on the track tractor saddle with a front platform. 

The semi-trailer is connected to the tractor by means of a fifth wheel coupling. A coupling pin (a short rod of a certain shape) located on the vehicle support platform is inserted into a special cutout of the load-bearing plate — the track tractor saddle, while fixing in it. The track tractor drives the mechanism.

All devices are conditionally divided into two groups:

1. European type. Its main features are as follows: 3 axles, disc and drum brakes, and single-slope bus arrangement. In absence of cargo, bridges can rise without participating in motion.
2. American type that is characterized by presence of two axles, drum brakes and two-slope bus arrangement.

The equipment is distinguished by the following main features:

• purpose;
• body type;
• type of cargo being transported.

According to the purpose, semi-trailers are divided into general-purpose and specialized mechanisms. The first group includes on-board equipment used for transportation of general-purpose cargo, with the exception of liquid cargo without containers.

Classification of Specialized Semi-Trailers, Advantages, Disadvantages and Criteria for Choosing the Equipment

Specialized semi-trailers are classified by body type as follows:

1. Dumping platforms designed for transportation of construction and agricultural bulk cargoes.
2. Vans, refrigerators, isothermal vehicles transporting industrial and food commodity groups.
3. Tanks used for transportation of petroleum products, gas, cement, chemical products, milk, flour, water and for other purposes.
4. Platforms, 2.5-3.4 meters wide, for heavy oversized cargo.
5. Truss platforms to transport the construction panels.

The group of special semi-trailers also includes: car carriers, grain carriers, poultry carriers, timber carriers, livestock carriers, concrete mixers and glass carriers. Devices are also classified by load capacity, overall dimensions and weight.

The main advantages of the equipment are as follows:

• maneuverability;
• high load capacity;
• uniform distribution of cargo;
• possibility to transport items with different lengths and dimensions, as well as cargoes with special storage conditions;
• breakdown of the track tractor does not require unloading the trailer, it is enough to replace the track tractor with a serviceable transport unit by disconnecting it.

The disadvantages of semi-trailers are as follows: the mandatory need for a truck tractor, and the narrow specialization of certain models.

Before buying a semi-trailer mechanism, it is necessary to decide on the purpose of using the equipment, types and dimensions of transported cargoes, know the approximate length and routes of transportation, as well as the number of planned trips.

When considering these criteria, the type of the semi-tractor and the type of semi-trailer corresponding to it shall be selected. It is also recommended to consider the carrying capacity of the mechanism, the suspension type, the turning radius, availability of additional equipment, the manufacturer and the vehicle cost.