The dependence of the functional parameters of a tractor of traction class 1,4 as part of a cultivator unit on the type of tire model of size 18,4r-38 on propellers

. The aim of the work: to establish the functional indicators of a cultivator unit based on a wheeled mobile power vehicle of traction class 1.4 when its driving wheels are equipped with tires of size 18.4R-38 of various models (206B, TM300S, VL-32). The increase in the performance indicators of the functioning of any machine-tractor unit depends largely on its working speed and the width of the grip, which implies the use of mobile energy means with high traction and energy indicators at the lowest level of dynamic processes in the links of the machine-tractor unit. For wheeled mobile power equipment, the achievement of high traction and energy indicators is determined by the properties of the tires of the driving wheels. Analysis of traction test data showed that the MTZ-80 tractor with VL-32 tires mounted on the propellers had the best traction performance compared to other tested models.


Introduction
The analysis of the technical equipment of the agro-industrial complex shows that mobile energy means (MEM) have been used, and will be used in the near foreseeable future, in the cultivation of crop production [1]. At the moment, when cultivating agricultural crops, about 85% of all MEM use energy facilities with wheeled running systems.
One of the main ways to increase the performance indicators of any tire-tractor unit (TTU) is its operation at high speeds and the use of agricultural machines with a large gripping width, which implies the use of mobile energy means with high traction characteristics when aggregating [2]. But at the same time, normal and tangential stresses in the contact imprint of the MEM propellers with a supporting base are constantly increasing, which leads to an increased negative impact on the soil, up to its destruction [3,4]. Hence the emerging scientific interest in the problem of increasing the traction properties of pneumatic movers MEM while simultaneously fulfilling the permissible standards of their impact on the soil.
Other disadvantages of the MEM wheel mover include the significant dynamic loading of all TTU links under conditions of variable loads that arise when performing practically any agricultural technological operation, which leads to additional energy costs developed by the MEM power plant [5][6][7][8][9][10].
For any wheeled MEM, the achievement of high traction performance, smooth running, the level of compacting effect on the support base, as well as the characteristics of movement along a given trajectory will be determined by the elastic properties of the driving wheel tires [2,11].
Therefore, the purpose of these studies is to establish the functional parameters of a cultivator unit based on a wheeled mobile power vehicle of traction class 1.4 when its driving wheels are equipped with tires of size 18.4R-38 of various models (206B, TM300S, VL-32).

Materials and Methods
An experimental method was used to establish the influence of various models of driving wheel tires on the traction and energy indicators of the tractor as part of the MTA. The test conditions corresponded to GOST 7057-2001 and GOST 24055-2016. Traction and energy indicators of the MTZ-80+CSR-4 cultivator unit were determined in accordance with the requirements of RD 10.2.2 "Methods of energy assessment of agricultural machinery".
The MTZ-80 tractor was chosen as the object of the study, which alternately has tires of the serial model 206B, the model VL-32 and the imported model TM300S, as part of the cultivator MTA.
Traction tests were carried out on two main agricultural fields: the stubble of ear crops and the field intended for sowing (Table 1). Continuous cultivation on the prepared area of the field was carried out to a depth of 8... 10 cm. The control of the cultivation depth during the experimental work showed that it did not exceed the limits of agricultural requirements.
When conducting comparative tests, a measuring complex was used, which included devices for determining the engine crankshaft speed, transmission drive shaft, tractor propellers and driven wheels; torques supplied to the axes of the propellers; traction, fuel consumption, as well as vertical and horizontal accelerations of the tractor frame.
The speed sensors were various tachogenerators.
To measure the values of the torques supplied to the axes of the tractor propellers, foil strain gauges were used, which were glued to the half-axes and connected according to the bridge scheme.
To fix the values of the traction force, a dynamometer developed by VISH was used, located between the tractor and the traction laboratory or cultivator.
To measure the vertical and horizontal accelerations of the tractor frame, MP-95 sensors with measurement limits of ±3g were installed on the lower part of its rear axle.
To estimate the magnitude of the traction efficiency in the calculations, the maximum power of the tractor power plant was taken as its average value, determined during bench tests before and after the experiments.
For a legitimate assessment of comparative tests, experiments were conducted within one day on the same field. At the same time, with all variants of the tractor's configuration with tires, it was controlled by an irremovable tractor driver.
During field tests, atmospheric pressure and air temperature were measured with a barometer and a mercury thermometer. The temperature of the fuel, oil in the pan of the power plant and the coolant was recorded by remote thermometers.
The distance traveled by the tractor, the duration of the tests and the parameters under study were determined using an automatic data accumulation and processing system developed at the Donskoy ANC Federal State Budgetary Research University (a division of the SCNIIMESH).
When processing these experiments, a personal computer with a package of special programs was used.
The measurement of the functional parameters of the cultivator MTA was carried out by a direct method, therefore, the accuracy of the experimental results was determined by the magnitude of the errors of the instruments in the measuring system (Table 2). The minimum repetition of the experiments was threefold. The test results obtained after each series were decrypted, and if questionable data were detected, the experiments were repeated after additional verification of the readings of all sensors of the measured parameters.

Results and Discussion
Before conducting the experiments, an examination of the selected tires was made (Table  3). The number of layers of the cord of the frame The angle of laying the threads of the cord breaker grad 70 The angle of laying the threads of the cord of the frame grad 5 The analysis of the data of the technical expertise of tires of size 18.4R-38 showed that the tires selected for comparative tests have different external geometry and internal structure, therefore they have different elastic damping properties.
As a result of the analysis of the data of traction tests of the MES of traction class 1.4 (MTZ-80 tractor) when installing tires of the tested models on its propellers ( Figure 1, Table 4), it was found: -MTZ-80 tractor on propellers with VL-32 tires at the pressure recommended by manufacturers in them of 0.11 MPa showed the best traction indicators among the tested options; -when completing the MTZ-80 tractor propellers with TM300S tires, intermediate values of its traction indicators were obtained; -the MTZ-80 tractor, when equipped with its propellers with serial tires of the model 206B, showed the worst indicators at both agrophones; -the MTZ-80 tractor on VL-32 tires, when the pressure in them was set to 0.08 MPa, showed the highest traction indicators in the field intended for sowing.
During the tests, the MTZ-80 tractor skidding on all tire models was below the permissible value (16%).
The analysis of the obtained traction and energy indicators (Table 5) showed that MTZ-80, when equipped with its propellers with any tested tire variants, quite satisfactorily provides aggregation of the CSR-4 cultivator: the tractor slip does not exceed 16% -the normalized value of the wheel tractor slip formula 4K2.  By analyzing the data obtained experimentally, it was found that the MTZ-80+CSR-4 unit on the VL-32 model tires showed the best traction and energy indicators. When installing VL-32 tires on the tractor's driving wheels, an increase in the loading of its engine by 1.50% and 3.30% was achieved, productivity growth by 2.65% and 8.30% was obtained, while reducing fuel consumption for processing one hectare by 2.7% and 6.8% compared to the complete set of tractor propellers with TM300S and 206B tires, respectively.
The cultivator unit with propellers on the tires of the model 206B showed the worst performance out of the three options.
When the tire pressure of the VL-32 model was reduced to 0.08 MPa, which is not recommended by manufacturers for other models, the unit showed even better traction and energy performance.
The result of the statistical analysis of the data obtained (Table 6) showed that when the MTZ-80 tractor drive axles are equipped with VL-32 tires, the continuous cultivation process is carried out with the smallest range of fluctuations of the studied parameters. When establishing intra-tire pressure in VL-32 tires, there is also a decrease in dynamic loads in the MTA links, which undoubtedly affects the quality of work [2]. At the same time, reducing the acceleration of the tractor frame provides improved working conditions for operators [11].
During the operation of the unit, each parameter under study can influence the behavior of others. Therefore, to establish the level of dependence of the studied parameters on each other, the pair correlation coefficients were found (Table 7).
When analyzing the data in Table 8, it was found that the smallest values of the pair correlation coefficient are observed when the unit's propellers are equipped with VL-32 tires. It follows from this that if the operating conditions change, the cultivator unit with the VL-32 tires installed on the MTZ-80 tractor engines will operate in a more independent mode, that is, more stable. This is especially noticeable when installing an intraperitoneal pressure of 0.08 MPa. According to the value of the pair correlation coefficient, it can be concluded that the cultivator unit on the tires of the model 206B is in the most unfavorable operating conditions in comparison with other options.
In order to establish the characteristic features of a stationary random process (the process of movement of any MT), we made a correlation-spectral analysis of experimental test data of cultivator MTAs aggregated by the MTZ-80 tractor, which alternately has different tire models on the movers, according to the results of which autocorrelation functions ( Figure 2) and spectral densities ( Figure 3) were constructed parameters characterizing the process of functioning of the cultivator unit.
Based on the results of the analysis of the graphs shown in Figures 3 and 4, it is possible to draw an unambiguous conclusion that the complete set of tires of the VL-32 model of the drive wheels of the aggregating tractor will provide stable and stable, both in frequency and time, functional indicators of the cultivator unit, due to the fact that in this case it is necessary to spend less energy to overcome the oscillatory process in its links. This is especially true for the unit with propellers on the tires of the VL-32 model, in which the air pressure is set to 0.08 MPa.
The cultivator unit based on the MTZ-80 tractor, on the driving wheels of which the VL-32 tires are installed, showed, in comparison with other variants (TM300S and 206B), the values of spectral densities are lower, respectively: -accelerations of the tractor frame: vertical -7.5 and 7.8 times, longitudinal (horizontal) -6.3 and 9.0 times; -engine crankshaft speed -2.8 and 10.0 times; -of the torque on the axis of the mover by 1.3 and 1.7 times; -of the traction force by 1.6 and 2.6 times.
This suggests that the cultivator unit, aggregated by the MTZ-80 tractor on the leading tires of the VL-32 model, will move more steadily with an increase in the uniformity of the course of its working bodies, which was confirmed by the results of the work quality check ( Table 9).  For production testing of the efficiency of the MTZ-80 tractor chassis systems with various tire models, we selected the MTZ-80+CSR-4 cultivator unit as the most used in agricultural production ( Table 10). As a result of the production inspection, it was found that the MTZ-80+ CSR-4 unit, when installed on the VL-32 tire propellers, had higher basic performance indicators than when the tractor was equipped with TM300S and 206B tires, especially at an intra-tire pressure of 0.08 MPa.
It should be noted that the cultivator unit on the tires of the TM300S model showed better performance than on the serial tires of the 206B model.

Conclusion
It is recommended to install tires of size 18.4R-38 of model VL-32 on the propellers of wheeled mobile power vehicles of traction class 1.4 to obtain maximum efficiency during their operation.