Transmissibility of agricultural tractor seats

Other than the technological development of the tractor components, in the last decennia the interest for the driver comfort increased. Noise and vibration control priority increased too. Especially for the vibration, driver's seat plays a great role. Modern tractors are often equipped without any type of suspension and the task of the tires is to reduce vibration caused by the uneven ground where these machines travel. When the tractor moves, it is solicited by a vibrational excitation that, through the vehicle, reaches the driver causing to him a stressing and tiring situation. Tractor drivers' seats must reduce the solicitations levels transmitted to the driver. For this reason, the European Directive 78/764 requires the validation of the seats. The validation must be done in a laboratory: the Directive requires only tests concerning the damping capacity along the vertical direction, whereas nothing is required for the other two directions, longitudinal and transversal. To verify the vibrational comfort values given by seat with pneumatic suspension, tests have been carried out using a 93 kW tractor. The tests have been executed with tractor speed of 13 km/h running on different surfaces: an artificial test track (ISO 5008), an asphalt road, an unmetalled farm road, a grass field and an harrowed clay field. The acceleration values have always been revealed over the seat and over the cabin platform. During tests, along X and Y axes, the seat transmissibility were always greater of one.