Resumen de Rolling Radii of a Pneumatic Tyre on Deformable Soil
Several rolling characteristics can be examined simultaneously by means of a suitable model representing the interaction of a pneumatic tyre rolling on deformable soil. The rolling radii can be distinguished, namely: the radius which develops due to wheelslip; the radius defined by the kinetics of the interaction; and the distance between the centre of the wheel and the bottom of the tyre. These three separate radii vary in time while rolling takes place. Owing to the varying nature of these values, they can only be obtained using dynamic measurements. This paper describes how these radii vary during rolling and discusses their interdependence. Tractor drawbar pull tests were conducted using 0·01 s data sampling intervals. The kinetic rolling resistance was defined by the peripheral force generated at the tyre-soil interface and the distance between the centre of the wheel and the bottom of the tyre, which is influenced by the wheel-load. The kinematic rolling radius was determined by measuring slip; and the kinetic rolling radius was established by analysing pull-test performance data, that is, the tractive force and the driving wheel-torque. The acceleration of the centre of the wheel was integrated twice with respect to time to obtain the path of the centre of the wheel as a function of time. The terrain profile, recorded after the tyre passed over it, and the path of the centre of the wheel were then plotted in the same coordinate system, making it possible to determine the distance to the bottom of the tyre.
