In recent years, many researchers have paid more attention to the substantiation and determination of the range of optimal (rational) parameters, ensuring a reduction in energy, labor and time, and the effect of mechanical treatment on the soil structure. The article presents the rationale and determination of the design parameters of the rotary subsoil loosener of the combined plough for flat ploughing. Rotational working element is made in the form of a screw cone mounted on a bearing, with the possibility of frictional rotational movement around its own axis from the reaction of the soil, and which is a multiple-thread screw. Oscillatory-rotational movement, which occurs in the process of introducing the ripper-subsoiler into the soil, is due to the uneven resistance of the soil. An analytical study was conducted from the point of view of the impact of soil-cultivating workers on the soil, depending on their design parameters. Analytical dependences of the subsoil loosener were obtained, which allowed substantiating the choice of its design parameters, in particular, the central angle β at the top of the cone, the width of the grip, the distance L between the plough bottoms and the resistant subsoil loosener, and the length of the soil splitting. Central angle at the cone apex β depends on the depth at which loosening occurs, the extension length of the cone apex from the tine and the rear cutting angle of the subsoil loosener.Minimal acceptable distance from the subsoil loosener's tine to the combined tillage machine's bottom depends on the depth of loosening, rear cutting angle, cone apex angle β and the physical-mechanical properties of the soil. These dependences determine the possibility of a stable rotational workflow, which is reduced to a constructive implementation after the calculation of its basic parameters. The obtained analytical dependences and some prerequisites can be used both in the study and in the design of such rotary working bodies.

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One of the necessary conditions for the creation of effective working bodies that ensure high quality tillage with the lowest possible energy intensity of the process is the search for the optimal geometric and kinematic parameters of the working body of the tillage implement. This problem is successfully solved for working bodies making a simple flat movement. At the same time, a significant proportion of the working bodies of agricultural machines have relatively complex working bodies, which, along with the portable rectilinear movement, rotate around its axis. So, many rotary working bodies rotate around disjoint axes and move progressively in a direction that does not coincide and does not intersect with the instantaneous axis of rotation. One of the promising designs of the working bodies for deep loosening of the soil is a rotary working body conical shape. In the article, the equations of motion of an arbitrary point of the working surface of a subsoiler of a conical shape are obtained. The subsoiler is a screw cone mounted on a bearing, with the possibility of frictional rotational movement. The main research results are obtained on the basis of theoretical study using methods of mechanics, analytical geometry and laws of agricultural mechanics. The rational parameters of the angle at the apex of the cone ψ and the rear cutting angle ε are revealed. Using the obtained equations, it is possible to determine the speed of action on the soil, as well as the acceleration of various points of the working surface of the cone-shaped rotary working bodies, which can be further used to analyze the process of interaction of the tool with the soil and justify its structural and technological parameters.

Establishing optimal technological and design parameters of tillage tools is essential for ensuring tillage quality and lowest possible energy consumption by the tillage process. For simple plane soil looseners, used on the majority of tillage machines, this task is successfully achieved. In the meanwhile, significant proportion of tillage machines has relatively complex tools, which combine translational motion of the tool with rotation around its axis. This article studies the process of soil interaction with a screw conical subsoiler mounted on bearings. The subsoiler can freely rotate around its axis. The surface of the subsoiler is described by the screw surface equation bounded by a circular cone. External action on the subsoiler body is a resultant of normal and tangential forces applied to screw surface and friction force in the bearings. Theoretical dependencies have been obtained which determine the resultant force of soil on the screw surface of the subsoiler. This force is composed of the sliding friction force and the force appearing due to frontal soil flow after destruction of soil structural cohesion. The article also gives results of numerical calculations. The obtained dependencies allow studying the influence of technological and design parameters of the screw tool on the tillage process and substantiate parameters’ optimal values.