Comfort efficiency of the front axle suspension in off-road operations of a medium-powered agricultural tractor

The whole-body vibration transmitted through the seat of a 4WD modern tractor of 81 kW max power, equipped with seat, cab and front axle suspension systems were measured and analysed according to the official relevant Standards. The test conditions involved the travelling speed (from 1.11 to 4.44 m s-1), the surface feature (field and rough track), the type of task (tractor alone and coupled with a towed slurry tank) and the front axle suspension condition (working or locked). After their statistical validation, the results highlight a good efficiency of the front axle suspension in reducing the vibration levels of the tractor alone, while when coupled with the slurry tank the benefit is less evident, especially in the back-front direction. The lower limit provided by the 2002/44 EC Directive (“action value”, 0.5 m s-2) is generally exceeded in all the three axes, apart when travelling at the lowest speed. Vice versa, the vibration levels exceed the higher limit (“limit value”, 1.0 m s-2) only if the overall RMS values are considered, in the field at 2.22 m s-1 and on the rough track at 4.44 m s-1.