Vol 84, No 2 (2017)

In 1972 G.G. Kolobov and A.P. Parfenov published the monograph «Traction characteristics of tractors». The monograph generalized numerous results of field tests of domestic wheeled and caterpillar tractors of that time, conducted by machine testing stations in various soil and climatic zones of the USSR. This had an impact on formulation and study of the issue of determining of tractors slippage, and in general, the study of their traction characteristics. Averaging of the experimental data was carried out according to the formulas and coefficients developed by the authors of the monograph. The obtained dependencies, hereinafter referred to as traction characteristics of tractors, establish the dependence of the coefficient of usable traction (specific traction force on the hook) on the slipping of tractors of various types on different soils. By now, the concept of the role of the studies in research of the interaction of a wheel and track with the surface has changed. The standards have been introduced to limit slipping of agricultural tractors, considering the negative impact of their propulsors on the soil. There is a need to clarify the terminology used earlier in order to unify the same meaning terms used in different, but related technical disciplines. Objectives of work are: rethinking of previous research results and assessing their relevance; distinction between the physical meaning and concepts of the traction coefficient and the coefficient of usable traction (specific traction force on the hook); determination of traction capabilities of wheeled and caterpillar tractors on natural agrotechnical and asphalt-concrete surfaces, considering current slippage limitations. It was proposed for the purposes of engineering calculations in assessing traction performance of tractors to use as a traction coefficient of various propulsors its value corresponding to the maximum slipping on the appropriate agro-technical background or dry concrete. It is also found that the limitations on slipping of tractors on metal caterpillars are overstated on all soil backgrounds, since they rather characterize the «stop» mode of the tractor, than the beginning of the unstable operation of the engine. The parameters of traction characteristics of 4x4 wheeled tractors require correction based on statistical replenishment with the initial data on traction tests of such tractors having a layout that considers the increased role of the front drive axle in creating the tractor pulling power. For 4x2 tractors traction characteristics are at the same time characteristics of traction performance of individual driving wheels (tires). Therefore, having such data on all available driving tires of different dimensions, it is possible, at the development stage, to determine traction properties of newly created different variants of machines, including all-wheel drive.

In Uzbekistan, over 800 thousand hectares of irrigated area are used to grow winter wheat in row-spacing of growing cotton. They are mainly sown by spreading, then seeded with cotton cultivators. Disadvantages of the spreading method are high seed rates by 30...40 % and excessive energy costs due to multiple (3...4 times) passes of the unit. However, the issues related to the establishment of the dependence of the quality of cereal crops in cotton row-spacing on the main parameters of the colter and the row profiles in Uzbekistan have not been adequately studied. In this regard, the materials of a theoretical study on the justification of technological and constructive parameters of the colter for sowing winter wheat seeds in the row-spacing of cotton are presented. As a result of the carried out research, it has been established that for the quality sowing and shaping of the seed beds the colter must be submerged in the soil to a depth of 2.0...4.0 cm. In order to form a slightly compacted furrow shape, the colter must be pressed to row-spacing surface. To ensure the non-heap of soil piles through the wings of the colter, their height should be 14...18 cm. In this case, the angle of installation of the wings in the continuous direction of colter movement should be equal to a = 47°, and the angle of the colter wing spread у = 69°. The given constructive parameters of the colter are optimal for sowing winter wheat seeds in the cotton row-spacing. The proposed new technology and colter design implements multi-row seeding from 5 (for 60 cm spacing to 9 rows (for rows between rows 90 cm). Due to formation of a new loose shape of the row spacing, the useful seed sowing area is increased by 9...22 % compared to the spreading method and conditions are provided for uniform seeding and obtain good and even sprouts.

It is scientifically proven that the main factors affecting the productive potential of the animals, are the structure of fodder farms, the quality of feed and methods of feeding. It is known that concentrated fodder are an important component in the diet of animals and contribute to a stronger manifestation of their productive potential. For grinding grain into livestock is usually used crusher with different working bodies. The most widely is spread hammer mill grain crusher. This happens due to the simplicity of their construction and relatively high resource of working bodies. Currently, for farmers are of great interest the small-sized feed factories and units, which include crusher grain with a fan. However, along with the obvious advantages of hammer crusher, like with forced feeding of material and with pneumatic, have a number of disadvantages, one of which is the increased wear of their working bodies: hammers, screens, fan blades. The greatest interest from the point of reducing wear represent fan blades, as changing their shape, it is possible to reduce or increase the intensity of wear. In addition, they are more prone to wear, since all of the crushed material passes through them with great speed, while in the grinding chamber, the amount of grain distributed over a larger number of hammers, and the relative velocity of grains in it decreases. The analysis showed that the intensity of wear of working surfaces of the blades of the fan depends on the coefficient of friction of grains on the blade, the angle of the blade to the radius of the rotor disc, and the greatest influence on friction force has a peripheral speed of the blades. To increase the service life of the blades and reduce the intensity of wear and tear it should be choosen the correct form of the smallest possible radius of curvature. The method is proposed on the basis of which it is possible to calculate the amount of wear of fan blades, taking into account its aerodynamic characteristics.

The article presents the results of an experimental study of a tractor diesel engine 4CHN15/20,5, equipped with various pre-start preparations tools, starting characteristics in a climate chamber at low ambient temperatures. The purpose of the study is the determination of different methods of tractors diesel engine pre-start preparation at its starting characteristics. Engine was sequentially equipped with electric starter system, together with the liquid starting preheater, and starter engine, which exhaust gases were used for oil heating in the crankcase of a diesel engine. On the engine was installed hydrotransformer that allowed to reproduce the actual conditions of engine operation more accurately. The study found out that engine with liquid starting preheater always starts at ambient temperature not lower than minus 30 ° C, but the pre-start preparation time is longer than one hour. Long warm-up time leads to discharge of even fully charged and warm batteries, which limits the start of diesel engine at lower temperatures. The use of a heater only for heating the coolant with heated oil in the diesel fuel tray with the exhaust gases of the heater slightly increases the rate of heating of the oil, compared with the use of water-oil heat exchangers, and has practically no effect on the speed of heating the coolant. Using the starter engine with forced coolant circulation and exhaust gases outlet for heating the crankcase and oil pump, allows to start diesel with cold batteries at minus 40 ° C during 30 minutes, that corresponds to the requirements of existing regulations. Results of the study were used for the modernization of production and development of new "Uraltrac" tractor diesel engines models and can be recommended for implementation in diesel engine companies.