Evaluation of the tire cross-section shape in relation with the traction force and traction efficiency of an agricultural tire

In this paper the traction force and traction efficiency of an agricultural type tire were evaluated, using a semi-empirical traction model of the driving wheel of a Romanian tractor; the model is based on Bekker's pressure-sinkage relationship and on the ASAE equations for traction force and traction efficiency. Tire deformation under vertical load was taken into account by the means of tire volume stiffness; three variants were considered in terms of tire cross-section: elliptical shape, spherical segment shape and toroidal shape. Experimental data, obtained when ploughing operations were performed, were used in order to validate the results predicted by the models, using goodness-of-fit analysis. It was concluded that the model based on the spherical segment shape of the tire cross section provided acceptable results for both traction force and traction efficiency in comparison with the experimental values; the other two models were more accurate in relation with the traction force, but proved to be less precise when referring to traction efficiency.