DETERMINING TRACTOR PERFORMANCE USING TRACTOR MOBILITY NUMBER AND ENGINE POWER

            Drawbar power used to describe the power requirement of an implement being towed or pushed. It is extremely useful in matching the rated horsepower of the tractor with the size of existing or purchased implements. In this paper, the tractors are classified according to their mobility number into three groups. The first group (I) has a range of mobility number of (4-5) at light soil and (17-23) at heavy soil. While the second (II) and the third (III) groups have ranges of (2-3) and (1-2) at light soil and (10-14) and (7-8) at heavy soil. Two methods are represented in this paper to describe drawbar power as a function of a tractor engine power. The first one predicts the drawbar power as a ratio of engine power at different soil types (clay soil, sandy clay loam and concrete road). The average drawbar ratios were 0.61, 0.55 and 0.75 for clay, sandy clay loam soils and concrete road for group I, 0.63, 0.52 and 0.78 for group II and 0.67, 0.55 and 0.84 for group III.  The second method is a model that predicts the drawbar pull using a mobility number and engine power for the clay and sandy clay loam soil. The model doesn't include predicting drawbar power at concrete because it is impossible to measure soil penetration resistance at concrete road. The PTO power ratio is calculated as a ratio of engine power. It is found to be as an average of 0.90 for all tractors type. The axle power ratios are 0.87, 0.83 and 0.83 for tractors of group I, group II and group III respectively. The average tractive efficiency on clay and sandy clay loam soil are: 0.66 and 0.62 for tractors of group I, 0.78 and 0.67 for tractors of group II and 0.81 and 0.66 for tractors of group III.