Formation the driving force of wheeled and caterpillar machine-tractor units

On the basis of existing dependencies describing the traction-coupling properties of wheeled and caterpillar machine-tractor units, theoretical and experimental investigations, a model of the formation of the driving traction force of units depending on the weight of the tractor, coupling properties of the propulsion unit, load distribution and propulsion slipping is obtained. The analysis of calculated coefficients shows a considerable variation of values, which causes difficulties in using in the calculations. Therefore it’s necessary to know their values at each interaction of the tractor propulsion unit with the soil. The same values of slipping can be obtained with different values of the coefficients. The task is simplified if data of this dependence have the same coefficient. During field investigations an active experiment was developed i.e. the levels of factors variation changed purposefully depending on the conditions of conducting each experiment. Composite B-plans (Box-design) of the second order were realized. The following parameters were chosen as the variable factors: the coefficient of the using coupling weight, the coefficient of traction and the weight of the tractor. The works were conducted according to the plan of the three-factor experiment matrix. As the agricultural field were a freshly plowed field, a stubble field and a wet meadow, with the coefficients of traction of 0,50, 0,65 and 0,80 respectively. The value of resistance to movement was fixed by a dynamometer during towing tractors MTZ-82, MTZ-2022 and MTZ-3022 DC.1 in neutral on the various agricultural fields. Efforts on the hook were changed by shifting gears in the gearbox of a towed tractor whose engine operated in the compressor mode. The coefficient of traction was determined with completely braked wheels of the tractor and towing it with a towing vehicle during simultaneously measuring the force on the coupling with the help of a dynamometer. The obtained model of driving force formation for wheeled and tracked machine-tractor units takes into account the weight of the tractor, coupling properties of propulsion units, load distribution, slipping and has a minimum number of experimental coefficients, which makes it more accessible and easily used for engineering calculations.