Testing the tractor in agricultural soil is one way of getting information, particularly with regard to the development of traction. The yield at the drawbar is often used to compare or evaluate tractors. However, drawbar performance is affected by the conditions of the displacement surface, the gear ratio and the ratio between the weight and power of the tractor. The objective of this study was to evaluate the yield at the drawbar of a tractor at different weight to power ratios, with different loads on the drawbar. The test was conducted at the Lageado Experimental Farm ,belonging to UNESP, on Botucatu Campus in SãoPaulo, by evaluating the following weight to power ratios: 50, 55 and 60 N kW-1, where for each of these ratios, three intervals of force on the drawbar were used, as follows: 15 to 20, 25 to 30 and 35 to 40 kN. It was concluded that the weight to power ratios and the loads studied showed little variability. The weight to power ratios of 50 and 55 N kW-1, for loads on the drawbar of 25 to 30 and 35 to 40 kN, showed differences between their averages, with the highest yield at the drawbar being obtained for a load of 25 to 30 kN, where the average was 50.9 and 54.1% respectively. As for the weight to power ratio of 60-N kW-1, there was no difference in the averages for loads of 25 to 30 and 35 to 40 kN.
Tractive efficiency; Dynamometer car; Tractor testing
