Ride vibration of agricultural tractors: Transfer functions between the ground and the tractor body

Abstract

Two experiments are described in which measurements were made of the transfer function between the ground profile and the motion of an unsprung agricultural tractor. The results of these experiments indicate that significant differences exist between the characteristics of rolling and non-rolling tyres. The stiffness of tyres was found to decrease at the onset of rolling and thereafter remain relatively constant for further increases in rolling speed. The damping characteristic of the tyres was found according to circumstances to increase or decrease substantially with changing rolling speed. The dynamic characteristics of rolling tyres were found to be relatively unaffected by changes in vibration amplitude. The motion of the tractor was found to be coherent with the profile of the ground only at frequencies lower than half the passing frequency of the tyre lugs.