(in agriculture), combination of a tractor or engine with agricultural machines (implements) for the performance of mechanized operations and processes in agricultural production. If a machine has its own engine and transmission for driving the working parts and movement over a field it is called self-propelled. Tractor-implement units may be simple, combined, or complex. A simple unit performs a single operation, such as cultivation; a combined unit consists of separate machines and performs two successive operations, such as plowing and harrowing; and a complex unit (for example, a combine) performs two or more operations with a single machine.
According to the type of production process, a distinction is made among plowing, seeding, harvesting, transportation, and feed-preparation units. The units may be mobile, off-road, stationary-mobile (with periodic movement of the unit over the field and stationary performance of production processes, such as loading hayricks onto vehicles or distributing feeds), and stationary (where the working machine, such as a grain-cleaning unit, is set up at a particular place). According to the method of connecting the implement to the tractor, the units are subdivided into trailer, semimounted, and tractor-mounted types. Trailer units consist of a tractor and an attached implement with its own running parts or a hitch and several trailer implements. Planters and cultivators are mounted symmetrically in relation to the longitudinal axis of the tractor; plows, reapers, and mowers are mounted asymmetrically. A tractor-mounted unit consists of a tractor (self-propelled chassis), one or more implements, and a mounted or semimounted connection. The choice of a particular tractor-mounted unit depends on the working conditions. In the semimounted unit the implement is supported in the transportation and operational positions by its own guide wheels and the mounting system of the tractor.
Tractor-implement units may be of the traction, traction-drive, or driven types. In the first case the unit uses the power of the tractor engine to propel the tractor and the working machine, which performs the production process (deep plowing, cultivation, and so on). A unit consisting of a tractor and trailer (body) is called a transportation unit. In the combined traction and drive type the power of the engine is used to propel the tractor and implement and to drive its working parts. The working parts may be driven by a power takeoff shaft from the tractor engine (in the case of fiber-flax combines and silage harvesters) or the drive or support wheels (for example, planters). In driven stationary or stationary-mobile tractor-implement units, the engine’s power is transmitted to the machine by a takeoff shaft or a belt, electrical, or hydraulic drive.
A. V. ELENEV