Single axle tractor

The single-axle tractor is a compact module consisting of an engine, transmission, one fixed-rotary drive axle, a frame, a cab and auxiliary equipment. The uniaxial tractor has a rotary support device to which the drawbar of the aggregated machine is attached. The rotation of the unit is carried out due to the rotation of the tractor relative to the machine ^[1] .

This design creates several advantages:

• Compared with the machine-tractor unit, where the entire weight of the trailed machine creates only harmful resistance and is not transferred to the tractor chassis, the part of the weight of the aggregated machine is transferred to the tractor’s driving wheels, which improves the traction properties of the wheels and increases the traction forces with a lower mass of the unit.
• Compared to a car, a uniaxial tractor does not need steered wheels, therefore, the radius and width of the wheels can be very large with a small width of the machine. This improves the permeability of the unit.
• The single-axle tractor has the ability to force rotation relative to the semitrailer by 90 degrees. This ensures the rotation of the unit in its dimensions and greatly simplifies maneuvering in reverse.
• The unit with a single-axle tractor has front-wheel drive, which also improves cross-country ability and maneuverability.
• A unit with a uniaxial tractor is more compact than a similar machine and tractor unit.
• The unit with a uniaxial tractor has significantly higher speeds (up to 50 km / h) compared to machine-tractor units.
• The driven wheels of the unit with a uniaxial tractor can be of very small diameter without sacrificing cross-country ability. This allows you to place on such chassis large-sized machines and modules (cranes, launchers or missile launchers).
• A single-axle tractor is a unified traction unit for completely different machines. This significantly reduces the range of spare parts and simplifies the training of drivers.

Disadvantages of a single-axle tractor:

• The uniaxial tractor is functional only in conjunction with an aggregated machine. Without an aggregated machine, it is unstable and cannot turn.
• The unit with a uniaxial tractor has low cornering stability.
• Compared to automobiles, single-axle tractors are slow-moving and have a higher specific fuel consumption.
• The rotation scheme of a single-axle tractor makes it difficult to move along public roads, since the overall width of the car in turn increases.
• It is more difficult to aggregate a machine with a single-axle tractor than with a tractor.

Monoaxial tractors are usually built using units (engines, transmissions) of trucks, less often tractors. Hydraulic systems, steering and chassis are usually original.

Initially, single-axle tractors were designed to work as part of self-propelled scrapers . However, their advantages turned out to be very relevant for road construction and military equipment and the production of single-axle tractors and machines aggregated with them was expanded. In the territory of the former USSR with uniaxial tractors, the following road construction vehicles were aggregated:

• high-speed scrapers;
• semitrailer graders (in comparison with motor graders they have better passability and traction);
• road rollers;
• self-propelled cranes, for example MKT-40;
• heavy trawls;
• mobile concrete and mortar units;
• mixers for transporting concrete;
• construction and underground heavy dump trucks;
• Using a special bridge, an attachment based on uniaxial tractors created ballast biaxial tractors.

In the USSR, uniaxial tractors were widely used in military affairs ^[2] . Based on them, engineering machines and machines for missile forces were created. Attempts were made to use uniaxial tractors in agriculture.

The first uniaxial tractor in the USSR was the MAZ-529 . In the CIS, the main producer of single-axle tractors is the Mogilev Automobile Plant ( Belarus ), which for many years has been the world leader in the number of cars produced. They are also produced at BelAZ . In the USA, single-axle tractors and machines based on them are manufactured by Caterpillar , in Europe - by Liebherr and Volvo , in Japan - by Komatsu and several other companies. It is interesting that in a separate type of equipment, a single-axle tractor was isolated only in the USSR, since it was widely used as part of a wide variety of equipment. In the USA, Germany and Japan - is not considered an independent unit.