Operation of tractors in high-mountain conditions is very different from their use in flat terrain. When braking on a steep long slope with large number of turns with minimal radius, the intensive heating of braking mechanisms is occurred, which not only reduces the efficiency of braking system, but also often leads to a complete failure. The aim of the study is to improve the operational efficiency of disk braking mechanism of a tractor produced by Minsk tractor works when braking during direct motion by means of increasing the impact of pressure disk on brake disk by the use of tractive effort torques that arise between them. The general characteristics of tractor braking mechanisms, as well as the characteristics of a proposed improved braking mechanism are given. The improved braking mechanism allows to rotate simultaneously the pressure disks in the direction of rotation of brake disks during tractor forward motion. At that, the tractive effort torques generated in the process of interaction of surfaces of pressure and friction disks match with the torques applied to the pressure disks from the side of brake gears. As a result, the total axial forces affecting from the side of pressure disks on brake disks are increased, which leads to the efficiency improvement of tractor braking. The patent no. 2435997 for the invention of disk braking mechanism has been received based on this study. The proposed design significantly improves the braking capabilities of a tractor. It can be used in the braking systems of tractors, vehicles and motorcycles.

Studies are carried out with the purpose of increase of soil cultivation quality through the improvement of technological process and design of a soil spiker with variable wedge angle of needles. When rotary needle working organs influence the soil, the following processes take place: the partial soil casting back and aside, soil layer hoeing, clods crumbling, plant remains burial and their extraction from soil, weed destruction and leveling of microrelief roughness. Quality indicators of performance of soil cultivation process by means of experimental section of soil spiker are determined. Investigations of soil cultivation process by means of experimental and serial sections of soil spiker are carried out on an experimental unit. Experimental section contains a disk with needles having the wedge angle of 9 and 5 degrees. The section of universal multifunction 5.4 beet hoe is used as a serial one. The soil samples are obtained in soil layers at a depth of 0-5; 5-10 and 10-20 cm. Soil quality indicators are determined according to state standards of the Ukraine 11465-2001 «The quality of the soil. Determination of dry matter and mass humidity» and 11272-2001 «The quality of the soil. Determination of density of structure on dry weight». The experiments are conducted in three replications. Following quality indicators of soil loosening by means of soil spiker are established as results of the studies: the cutting (destruction) of weeds in treatment area is 98.5%; the content of fractions of size up to 25 mm for needles with wedge angle of 5 degrees is 88.2%, for needles with wedge angle of 7 degrees - 90.5%, for needles with wedge angle of 9 degrees - 93.5%.

It is shown that the basis of robotic technologies in plant cultivation is an unmanned mobile power unit for agricultural purposes on wheeled or tracked platform with hybrid power plant, motion control and machine vision equipment. Description of software algorithm and schematic circuit diagram of motion control are given. It is noted that machine vision is an integral part of working organs, because much of the information about the state of plants (growth rate, maturity degree, disease) is received through visual contact, as well as through systems of motion control and precise positioning. This information allows the robotic working organs to find the technological solutions and implement the required operations, and the unmanned mobile power unit to move on process route. Another fundamental function of unmanned mobile power unit is positioning and motion control on required trajectory. A brief analysis of implementation of this function by means of satellite navigation or ground facilities of positioning including machine vision and target indication is given. Satellite navigation systems provide positioning and identification on large areas, but do not work indoors. Network wireless system of local positioning allows to control the location and motion of objects and reliably identify them both outside and inside the premises. Combined application of such systems allows to extend the motion control of vehicles and agricultural machines to areas not directly visible for satellites: covered yards, buildings. That creates additional opportunities for control of local movements of products and personnel in industrial and non-industrial premises of closed and open type.

The United Nations Organization has called for the need to increase world food production by 70% to 2050. Russia has 9% of world agricultural land and 2% of population of the world, and could not only provide itself with the quality production, but supply the world market. However, today the state support of our agriculture and enterprises producing agricultural machinery is insufficient. One of the most important conditions of agricultural development is a large-scale revival of domestic agricultural engineering, one of the oldest industries of the country. The article presents extracts from the history of this industry, gives an overview of main features and development trends of domestic and foreign agricultural engineering. It is noted that in recent years production and development of domestic agricultural machinery has been reduced significantly. Being its key customer and consumer, the Ministry of Agriculture of the Russian Federation stopped formerly active and useful participation in the development of technical means. Import of foreign machinery increased. But the imported machines do not always sufficiently conform to our conditions. The development of domestic production of agricultural machinery and its use are to be granted the status of top-priority task of the state. A set of measures is proposed for the implementation of this task. These measures will provide the necessary level of food security of the country, the welfare of population, the growth of food exports and raising Russia’s international standing.

In order to develop the methods for assessment of durability of pistons of tractor diesel engines, it is necessary to conduct the research of causes of failures in their operation, in particular crack formation on the edge of combustion chamber. Tractor engines operate in transient regimes due to periodic changes of control organ position and resisting moment when tractor performs agricultural, logging and other works. In transient regimes, the stress-strain state of piston varies in time, which leads to the formation of fatigue cracks on the edge of combustion chamber. The paper reviews the studies on regularities of change in the rate of propagation of fatigue cracks on the edge of combustion chamber of tractor diesel engine. The peak values of heat flows passing through the heat-absorbing surface of piston head in transient regimes exceed by 2.5 times the same values in steady-state regimes. According to the researches, for the 4ChN 11/12.5 tractor diesel engine stress intensity on the edge of combustion chamber caused by temperature gradients equals to 92-98 MPa, and exceeds more than by 2 times the stresses caused by gas pressure forces in cylinder (38-42 MPa). With the increase of engine forcing, the edge of combustion chamber becomes a local concentrator of thermal stresses, that leads to elastic-plastic deformations of cyclical pattern and microdefects. Stresses appearing on the edge of combustion chamber under rapid change of loading modes typically exceed the values of yield stress of piston material. This leads to the appearance of plastic deformations on the edge of combustion chamber. The analysis of causes of crack formation on the edge of combustion chamber of piston of a tractor diesel engine shows that when assessing the durability of piston, the whole range of indicators and parameters of the engine should be taken into account.