JUSTIFICATION OF THE RATIONAL GEOMETRY OF THE STEERING TRAPEZOID OF A VEHICLE WITH A VARIABLE TRACK

A steering trapezoid with a four-link articulated-lever mechanism is used in the control system of most modern wheeled vehicles, including tractors, to perform wheel rotation. It is noted that its use is not always effective due to non-observance of the required correspondence between the rotation angles of the inner αВ and outer αН of the steered wheels, required by the condition of implementing their pure, without slipping, rolling and correct rotation. It is established that when the track of a wheeled vehicle changes, the kinematic discrepancy between the correct and actual rotation increases. The objective of this work was to improve the design of the steering trapezoid of a wheeled vehicle to maintain the conditions of pure rolling when the track width changes. Recommendations on finding the intersection point of the continuation lines of the working lengths of the lateral pivot levers of the trapezoid at a distance of d = 0.75L from the axis of the front axle of the vehicle are taken as the main criterion. The calculated kinematic scheme has been developed. Analytical expressions establishing the relationship between the geometric parameters of the elements of the articulated-lever mechanism of the steering trapezoid: the length of the lateral pivot levers m, the angle of their inclination to the longitudinal axis of the machine φ, the wheelbase L and the length of the transverse rod n, are derived on this basis. Rational values of m and φ for different tracks are determined for the Belarus-80.1 tractor. The need to improve the design of the steering trapezoid of the Belarus-80.1 tractor with a variable track was confirmed by an analytical study of the kinematics of the experimental version of the steering trapezoid, which makes it possible to obtain rational relationships between the turning angles of the steered wheels. For example, when changing the turning angle of the inner steered wheel from 20 ° to 40 °, a decrease in the minimum turning radius of 3.375 m was obtained when using a modernized trapezoid compared to a serial one. Experimental samples of side levers of the steering trapezoid were manufactured for three track width options of the Belarus-80.1 tractor.