Abstract
The aim of these experiments was to investigate the characteristics of a 495/70 R24 XM47 radial tyre and a suspension coil spring and damper as used on high mobility agricultural tractors. Data were collected using a single wheel tester operating on two surfaces. A steel plate bumpy track laid on a flat tarmac surface provided a square wave input to the wheel and a compacted sandy loam soil in a ground level soil tank had a sine wave cut into the surface. The main test wheel variables changed were the tyre input frequency, the tyre pressure and the vertical tyre load. Vibration transmissiblity and decaying free vibration were used to determine dynamic tyre stiffness and damping. Decaying free vibration of a rolling tyre was found more applicable at tyre pressures higher than 2 bar. Tyre stiffness increased with increasing tyre pressure and increased from 328 kN/m at 1 bar to 645 kN/m at 3 bar for a tyre load of 1600 kg. Measured damping values are given. Vibration transmissiblity was used as an indication of linear or non-linear characteristics. Compared to the steel bumpy track, the hard soil surface appeared to give very little change in tyre stiffness but a large increase in tyre damping. For the limited results presented, the software simulation of the suspension accounted for most of the vibration transmissibility change.