Analytical justification of the parameters of the internal structure of tires of a propulsion unit for mobile power vehicles of traction class 1,4

Any wheeled mobile power vehicle for agricultural purposes takes into account the required traction performance, its smoothness, the level of soil compaction and the characteristics of the trajectory, which depend on the properties of the shell of the pneumatic tires of the propulsion units. The justification of the internal parameters of a pneumatic propulsion unit is obviously impossible without a set of theoretical and experimental studies based on mathematical modeling of the processes in the propulsion unit and subsequent fullscale tests. Accordingly, the purpose of the research is to substantiate the parameters of the internal structure of tires of propulsion units for mobile power vehicles of Traction Class 1,4 using the method of physical similarity. When substantiating the parameters of the internal structure of tires for mobile power vehicles of Traction Class 1,4, there has been applied a theoretical and experimental method in the study. It was determined that tires of size 18,4R-38 require the number of breaker and carcass layers should be four and three, respectively, the angles of inclination of the cord threads in the breaker and carcass should be 700 and 50, respectively. It has been proved that in order to achieve the maximum performance of a machine-tractor unit based on a mobile power vehicle of Traction Class 1,4, one should provide tires of a propulsion unit with a normal stiffness of 278 kN/m, a tangential stiffness of 323 kN∙m/rad. The experimental tire of Model VL-32 has such elastic properties. The tires of Model VL-32 that are installed on the driving axles of a mobile power vehicle of Traction Class 1,4 revealed the maximum values of the spectral densities of the torque on the driving axle of the propulsion unit, crankshaft rotational speed of the engine, and the vertical accelerations of the rear axle are lower, respectively, by 26,9%, 28,0% and 23,8% compared to tire of the serial model 206B. With an increase in the stiffness of the studied tires of size 18,4R-38, the maximum values of the spectral densities of the same parameters occur at a higher frequency, which prevents the occurrence of resonant frequencies of the studied parameters during the trajectory of the machine-tractor unit.