Abstract. Ideally, the theoretical drawbar performance characteristics should be identical to the one experimentally obtained. In reality, there are some differences between the two characteristics. One difference lies in that the actual speed of the tractor, which is analytically obtained, is not equal to the actual speed of the tractor that is experimentally obtained. We assume that the actual speed that is obtained on a theoretical basis depends on engine speed, transmission ratio and tractor slip. In reality this speed also depends on the variable value of the tractor wheel radius: for instance, it depends on the tractor variation of weight distribution on the two axles during operation. The paper presents a mathematical model that determines the theoretical drawbar performance characteristics of the wheel tractor taking into account the modification of the wheel radius during operation. The paper also presents applications of the mathematical model developed on tractor MAT 81, constructed in Craiova, Romania. We further examine the calculus systematic errors that may occur when we assume the tractor wheel radius is constant. Introduction. Defining the drawbar performanceThe drawbar performance along with the economic qualities of the tractor for nominal operating conditions and also for all the other conditions are determined with the drawbar performance characteristics. The drawbar performance characteristics is analytically or graphically-analytically built, considering the drawbar pull F t parallel to the ground surface, when the tractor is operated on horizontal ground, under stable operating conditions (V = constant).

Abstract:The paper elaborates a mathematical model in order to conduct a study into the dynamics of tractor-trailer systems during braking. The braking dynamics is analyzed by considering two versions for the braking system: 1) braking applied on the rear axle and 2) braking applied on all four wheels. In both versions the trailer is braked on all wheels. The mathematical model enables us to determine and graphically illustrate the evolution of the following parameters: braking deceleration, braking speed and the distance traveled by the tractor during braking. The mathematical model elaborated is applied on a tractor-trailer system completing transportation works.

The paper elaborates a mathematical model in order to study the dynamics of tractor-trailer systems during braking. The braking dynamics is analyzed by considering two versions for the tractor’s braking system: 1) braking applied on the rear wheels and 2) braking applied on all four wheels. In both versions the trailer is braked on all wheels. This model enables us to determine the evolution of the following parameters: braking deceleration, braking forces, and force at the tractor-trailer hitch point. The authors present applications of the mathematical model elaborated on a tractor-trailer system used for transportation works.

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