EXPERIMENTAL ASSESSMENT OF THE RIDE COMFORT OF FARM TRACTORS

The paper is focused on the assessment of the ride comfort of farm tractors. The problem of assessing the ride comfort is crucial due to the fact that operators spend part of their own lives on board of such machines, exposed to whole body vibrations potentially harmful for their health. The paper deals with the experimental measurement of the relevant vibration occurring at the tractor body, at the cabin and at the seat. The focus is on which accelerations are actually relevant and have to be taken into account. A number of farm tractors have been instrumented and run under monitored conditions. The test track was equipped with a number of cleats able to force at resonance the cabin and the seat. The six motions of the tractor body and the six motions of the cabin were measured. The motion of the seat was measured. The signals have been processed in the time domain. Some interesting occurrence have been highlighted referring to the amplification that a badly regulated seat can provide under certain circumstances. The comfort index was computed according with ISO 2631 and other standards. The acceleration of the seated subject was described at different positions on the body. It turned out that the acceleration of the head was particularly relevant for establishing a comparison among different tractors. Synthetic indices have been derived from the measured data able to correlate the subjective drivers' feeling with the measured level of vibration. The conclusion is that for a proper comparison of the ride performance of different farm tractors a huge number of measurements are needed. There is no possibility to record only the vertical accelerations to assess the ride co mfort of farm tractors.