Matching the Traction Qualities of Agricultural Mobile Power Vehicles with the Permissible Maximum Pressure on the Soil

. Modern highly mechanized agricultural production is characterized by the incompatibility of simultaneous matching of the maximum pressure of agricultural mobile equipment movers on the soil and the possibility of increasing the tractors energy saturation when equipping them with existing wheel engines. ( Research purpose ) To coordinate the maximum pressure on the soil with the permissible norms, weight utilization factors and the level of tractors energy saturation. ( Materials and methods ) The authors used a calculated method for determining the maximum pressure on the soil using a universal tire characteristic. ( Results and discussion ) The authors found that when performing spring works on closing moisture and sowing row crops at a maximum pressure of 80 kilopascals, corresponding to all types of soil, the most mass universal row tractor Belarus 1020 had a maximum pressure of 150 kilopascals, which was 70 kilopascals higher than the permissible one for the corresponding crop shortage. They found that replacing ordinary tires with agrophilic tires could increase the area of the contact spot by 16 percent, while reducing the coe ﬃ cient of unevenness and increasing the coe ﬃ cient of use of the adhesion weight. The main condition for replacing ordinary tires with agrophilic tires was to keep the traction force unchanged. ( Conclusions ) Summarizing the results of the research as agrophilic direction, ensuring the compliance impacts on soil and positively solving the problems of saturation, it is possible to recommend the development of navigation systems in achieving utilization hitch weight equal to 0.5 (low tire pressure), equal to 0.6 (rubber joint with torsion bar suspension) and 0.7 (rubber track). It was found that the conducted research, taking into account the available data on traction tests of the T-250 tractor, would allow to include an agrophilic concept with a hypothetical dependence of the adhesion weight use factor on the longitudinal unevenness coe ﬃ cient in the revised State Standard 27021-86 “Agricultural and forestry Tractors. Traction classes”.


Согласование тягово-сцепных качеств движителей сельскохозяйственных мобильных энергетических средств с допустимым максимальным давлением на почву
THE RESEARCH PURPOSE is to coordinate the maximum pressure q max on the soil with permissible norms, coefficients of adhesion weight φ c using and the level of tractors energy saturation.

MATERIALS AND METHODS.
To solve this problem, it is necessary to conduct in-depth experimental studies of the longitudinal non-uniformity coefficient influence the pressure distribution over the tire K 2 contact area on the adhesion weight φ с use coefficient for given slipping δ max and maximum contact pressure qmax.
To coordinate the maximum pressure q max on the soil with the permissible norms, the adhesion weight φ c use coefficients and the energy saturation level, the authors used the calculation method for determining the maximum pressure on the soil using the universal characteristics of the tire, given in State Standard R 58656-2019 in combination with the results of actual traction tests of progressive wheel and tracked movers [5][6][7].

RESULTS AND DISCUSSION.
As a result of the research, it was found that when performing spring work on closing moisture and sowing row crops at an admissible maximum pressure of 80 kPa, corresponding to all types of soils, the most massive universal row-crop tractor Belarus 1020 had a maximum pressure of 150 kPa, which was 70 kPa higher than permissible with a corresponding shortage of harvest ( Fig. 1).
Based on the previous results, the authors considered the possibility of reducing the maximum pressure of the tractor, based on Fig. 2 and formula (1), obtained taking into account that K; where K 2 = 1.5 was the coefficient of longitudinal non-uniformity of pressure distribution over the support area of the tire-soil contact [6,[8][9][10][11][12][13][14].
For new highly elastic tires K 2 could be specified when determined according to a method agreed with consumer, customer and tire developer representatives (State Standard R 58656-2019, replacing State Standard 26953-86. Agricultural mobile equipment. Methods for determining the impact of propellers on the soil).
where G к -mass that created a static load on the soil by a single wheel propeller; F кп -wheel contact area with soil, m 2 .

ЭКОЛОГИЯ ECOLOGY
Then: At the same time, the adhesion weight use factor based on table 1 (tests of tires of LIM company), take φ с А = 0.5 , where φ с А -adhesion weight use factor of agrophilic tires, instead of φ с о = 0.39 where φ с о -adhesion weight use factor of ordinary tires corresponding to the old State Standard 27021-86.
At the same time, the authors assumed that K 2 А = 1.2, where K 2 А was the coefficient of agrophilic tires irregularity, instead of K 2 о = 1.5 where K 2 о -adhesion weight use factor of ordinary tires. The fundamental condition for replacing ordinary tires at φ с о = 0.39 with agrophilic ones at φ с А = 0.5 was to maintain a constant traction force created by the tractor: in accordance with the definition of adhesion weight use factor, was determined by the formula:

TRACTION INDICATORS OF THE T-150K TRACTOR WITH VARIOUS TIRES
Based on formula (1), the authors defined: Where, taking into account the requirements for reducing the maximum pressure on the soil (Fig. 1) they got: q max о /q max A = 150 kPa / 80 kPa = 1.88.
The scale of the increase in F к А in comparison with F к o was schematically shown in (Fig. 3), and the sequence of actions to reduce the maximum pressure on the soil was shown on the nomogram (Fig. 4).
The nomogram graphically shows a decrease in the maximum pressure q on the soil from 150 kPa to 80 kPa (ΔΣ) with an increase in the adhesion weight use factor φ с from 0.39 to 0.50 due to a decrease in the adhesion weight from 36 kN to 28 kN, a decrease in the coefficient of longitudinal irregularity of K 2 from 1.5 to 1.2 -ΔК, an increase in the tire contact area by 16% -ΔF with a constant traction force P cr = 14 kN and an increase in the energy saturation of E tr from 2,0 kW/kN to 2,6 kW/kN, corre-sponding to Professor G.M. Kutkov qualifications for third-generation tractors.
Summarizing the results of the research presented in tables 2, 3, as well as in figure 5, it was necessary to include in the revised State Standard 27021-86 "Agricultural and forestry tractors. Traction classes ", the following recommendations.
The nominal tractor tractive force in kilonewtons was determined by the formula P cr.nom = A⸳m e , where А -coefficient set depending on the tractor type; m e -operating weight of the tractor, kg.
Coefficient А take equal: 3.24⸳10 -3 -for agricultural tractors: 3.73⸳10 -3 -for tractors with an operating weight of up to 2600 kg; for four-and three-wheeled tractors with two driving wheels (4K2 and 3K2) with an operating weight of over 2600 kg; for four-wheel tractors with four driving wheels (4K4) and an operating weight of over 2600 kg: 3.92⸳10 -3 -with tires of the ordinary concept; 5.00⸳10 -3 -with ultra-low pressure tires; for tracked tractors:

Soil background Winter wheat stubble
Operational weight, kg 13200

CONCLUSIONS.
Taking into account the research data as an agrophilic direction, ensuring compliance with the norms of impact on the soil, and positively solving the problems of energy saturation, it was possible to recommend the development of running systems to ensure the achievement of the adhesion weight use factor φ с = 0.5 (ultra-low pressure tire), φ с = 0.6 (rubber-metal hinge with torsion bar suspension) and φ с = 0.7 (rubber-reinforced track).
The conducted research, taking into account the available data on traction tests of the T-250 tracked tractor, would make it possible to include the agrophilic concept with a hypothetical (assumed) dependence of the adhesion weight use factor φ с on the longitudinal unevenness coefficient K 2 in the form of recommendations in the revised State Standard 27021-86 "Agricultural and forestry tractors. Traction classes " [15][16][17][18][19][20].