Theoretical study of the conditions of the maximum allowable slipping of wheel tractors
¹National University of Life and Environmental Sciences of Ukraine, 15 Heroyiv Oborony Str., UA 03041 Kyiv, Ukraine
²Institute of Mechanics and Automatics of Agroindustrial Production of the National Academy of Agrarian Sciences of Ukraine, 11 Vokzalna Str., Glevakha stl, Vasylkivsky Dist., UA 08631 Kyiv Region, Ukraine
³Dmytro Motornyi Tavria State Agrotechnological University, 18B Khmelnytsky Ave., UA 72310 Melitopol, Zaporozhye Region, Ukraine
⁴Estonian University of Life Sciences, Institute of Forestry and Engineering, 56 Kreutzwaldi Str., EE51006, Tartu, Estonia
*Correspondence: jyri.olt@emu.ee
Abstract:
The process of tractor wheels slipping is accompanied by two forms of ground deformation: displacement and shearing. From the point of view of preserving the structure of the soil environment, wheel slip should be limited to displacement only. The limit of soil strength at this deformation can be a standardizing parameter. In this article an analytical dependence is developed, which allows using the parameter to establish the maximum permissible level of slipping of wheeled tractors. Of the soil parameters, the specified dependence includes the coefficient of sliding friction between the particles of soil medium and the coefficient of wheel rolling resistance on a particular agrotechnical background. Theoretical studies have established that the greater the value of this coefficient, the smaller should be the maximum permissible value of tractor slipping with a more economical effect on the soil environment. Compared to a tractor with a nominal drawbar pull of 14 kN, the use of a heavier tractor with a drawbar pull of 30 kN is possible with higher values of maximum permissible towing. This result is due to the magnitude of the vertical load on the wheel of the heavier tractor, which gives it a greater friction force between the tire wheel and the ground and allows the same contacting traction force to be realized at a lower level of slipping. The results of mathematical modeling using the developed analytical relationships indicate that with increasing the value of the angle of placement (slope) of the tractor wheel to the longitudinal axis of symmetry, the maximum permissible level of its slipping should be less. This will help to reduce the value of deformation (longitudinal shift) of the soil by the tractor during its working movement. When using the ground shear strength limit у as a limiting parameter for increasing the pitch and height of the tractor tire, as well as the width of the tractor wheel tyre, the maximum permissible level of its towing is more than 15%, which is an undesirable fact.
Key words:
rolling resistance coefficient, soil conditioner attachment, soil shear strength, tangential driving force, tractor attachment