Optimization of the tractive performance of four-wheel-drive tractors: Theoretical analysis and experimental substantiation

Abstract

The results of a theoretical analysis reveal that, for a four-wheel-drive tractor to achieve the optimum tractive performance under a given operating condition, the thrust (or driving torque) distribution between the front and rear axles should be such that the slips of the front and rear tyres are equal. For four-wheel-drive tractors with rigidly coupled front and rear drive axles, this can be achieved if the theoretical speed (the product of the angular speed and the free-rolling radius of the tyre) of the front and that of the rear wheels are equal or the theoretical speed ratio is equal to 1.

Field test data confirm the theoretical findings that, when the theoretical speed ratio is equal to 1, the efficiency of slip and tractive efficiency reach their respective peaks, the fuel consumption per unit drawbar power reaches a minimum, and the overall tractive performance is at an optimum.