The research objective was justification of the most effective parameters and operating modes of cultivating unit with wheel 4k4a tractor of the 5th class of draft. The research problem was the establishment of the extent of influence of variable external impacts on the parameters of traction characteristic of wheel tractor "John Deere 8310R" taking into account various values of its opera-tional weight. The research problems were solved by means of universal techniques of determination of the most rational values of traction dynamic characteristics of the tractor at casual character of external loading. The comparison of settlement data showed that power indicators of a tractor on unary or dual wheels at various values of coefficient of the variation of loading on this transfer insignificantly differ in identical size of opera-tional weight. The installation of dual wheels allows im-proving parameters of traction characteristic of a tractor. For example, traction power of a tractor increases on average by 6 %. The losses of power caused by the impact on the unit and a tractor of variable external fac-tors make 5 % at the maximum size of coefficient 1 % lower, than at a complete set 1K. Optimum load modes for various complete sets at = 0.06--0.2 are in the zone of the extent of loading of a tractor = 0.97-1.1. Traction mode = 1.0 corresponds to the maximum value of trac-tion power of the tractor. The most rational is the tractor weighing =14690 kg complete set on dual wheels (2K). It is confirmed by values of parameters of traction char-acteristic of a tractor at various values of coefficient of variation. The results of two-criterion optimization (sim-ultaneous influence of two major criteria were consid-ered: the maximum of traction power of a tractor and minimum of specific fuel consumption) showed that op-timum extent of loading of a tractor averages 0.98. Min-imum of energy consumption on operating mode and, respectively, minimum size of total operational expens-es are provided in the range of values of the load mode of the tractor = 0.85-1.07.
tractor, tillage, rational parameters, vari-able load, design methods, operating weight
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