In the article theoretical preconditions of a description of dynamics of manoeuvrability of machine-tractor, aggregates with a wheeled-tracked mover are considered. For a machine-tractor aggregate with half-tracked progress theoretical formulas of determination of an actual turning radius, the moment of resistance of turn and torque for rotation are obtained. The theoretical preconditions are confirmed by experimental research of the manoeuvrability of the machine-tractor aggregate with the tractor on a halftracked progress, made as the experimental sample. The dependences of the turn coefficient and the resistance coefficient of the turn are obtained, and the correlation coefficients and their significance have confirmed the existence of a stable connection between the changing parameter and the response function. Proceeding from theoretical and experimental research, it is possible to draw a conclusion that the manoeuvrability of the tractor with a wheeled-crawler mover does not concede to the tractor in the basic execution.

Development of agriculture in conditions of market relations is accompanied by aggravation of the problem of efficiency of use of technics. In this connection, the task of scientists is to increase the actual volume of work performed by tractor units, reducing the cost per unit of production. The high cost of tractors, the lack of personnel, the reduction of technical equipment of farms and the increase in the volume of products produced in the agro-industrial complex, natural and climatic conditions impose special requirements on technical service to maintain tractors in working conditions. The working state of tractors is the state at which values of parameters, which characterize ability to execute the given functions, correspond to normative-reference and design documents. During the operation of tractors in agriculture under the influence of various factors, wear of their parts and knots. The indicator determining the value of wear is the residual resource of aggregates and knots of technics. In the article the questions of influence of residual resources of basic aggregates and systems of tractor on frequency of failures of various groups of complexity are considered. Experimental research on determination of dependencies of residual resources of tractor units and frequency of failures of different groups of complexity, on the basis of which the rules of replacement of the unit whose resource are exhausted, is carried out, i.e. is replaced with a full of the resource (new) or on the aggregate after overhaul.

3. Novikov Vladimir, Candidate of technical sciences, professor of the department of Agricultural machines and mechanization of livestock breeding, Samara State Agrocultural Academy, 446442, Samara region, Ust'-Kinelsky settlement, Uchebnaya st.

The process of operation of tractors is inextricably linked with conditions that affect their performance. These conditions include operational, organizational and climatic conditions on the one hand and technical operation on the other, i.e. the technique is influenced by operating conditions. A comprehensive, dimensionless indicator of the operating conditions of tractors in agricultural production is the level of their operation. The level of operation of the tractor, this is the state of their operation on the farm, which is determined by the degree of implementation of measures for the technical operation of equipment and the percentage of tractors involved in labor-intensive processes when used for their intended purpose. The theoretical level of operation of the tractor can vary from 0 to 1. At the same time, 1-corresponds to the state of operation of the tractor, in which the resource consumption is minimal, i.e. the degree of implementation of the generalized factors of technical operation meets the requirements of State standard and the tractor performs work with the lowest resistivity; 0 -theoretical, corresponds to the state of operation of the tractor, in which the resource consumption is maximum, i.e. technical operation of the tractor is not performed and the tractor performs work with maximum resistivity. The article discusses the optimization of the level of operation of tractors, presents a methodology for optimizing this indicator and provides a calculation using the example of farms in the Republic of Tatarstan. Regularities of changes in unit costs for eliminating failures and downtime depending on the level of operation of tractors are obtained. Calculations are given to justify the optimal values of operating hours before repair, between repairs and operating hours before decommissioning, depending on various values of the level of operation of tractors.

The relevance of this study is subject to the fact that the intricate design of the valve assembly's control system shows the insufficiently highperformance characteristics of the pump-injector units. The purpose of the study is to develop a modernization model for a pump-injector unit to increase its functional performance and develop its control valve. The principal method to be used to investigate the problem is to assess the influence of the design parameters of the control valve on the quality of the operation of the pump-injector unit. The authors developed a method to upgrade a diesel pump-injector unit using a ring control valve, as well as a mathematical model for the operation of the ring control valve of the pump-injector unit, which allows for the establishment of parameters affecting the quality of its operation. Studies have shown the effectiveness of the control ring valve on the pump-injector unit. The ring valve performs the function of both the force and locking elements. The absence in it of a particular power element (spring) can significantly reduce the volume of the intra-valve cavity. The ring functions as a freeedge mechanical multiplier built into it with a multiplication factor π. There is no spring, discharge volume decreases, and the pump-injector unit speed increases.