Simulated performance of a tractor equipped with two types of tyre under two levels of soil moisture

Due to the importance of grain production, and the need to work the soil under limited moisture, the aim of this study was to develop computer software to predict the tractive capacity of wheeled tractors for two types of tyre, the effect of different inflation pressures and levels of soil moisture. A mathematical model was developed to predict the tractive capacity of a 4 x 2 AFT tractor. Software was developed and tested by comparing the computational data with those from tests of a working tractor in the field. The parameters under evaluation were drawbar force and front and rear drive wheel slip. At both moisture levels, the bias tyres had the lowest front to rear slip ratio at the lower pressure; the ratios were similar when equipped with radial tyres. The bias tyres show maximum force at a slip ratio of 1.09 at the higher pressure and 1.03 at the lower, while for the radial tyres the ratio was 1.05 at the higher pressure and 1.07 at the lower. Software was developed to process data from the model, with the results used for estimating the tractive force of the tractor. The tractive force was overestimated by the model, which needs further adjustment for direct application in the field.