Search

A tractor losing lateral stability starts to rollover. It is a matter of fact that tractor lateral rollover accidents are one of the most frequent causes of death and injuries for farmers. Consequently, tractors are fitted with a specific protective structure to minimize the consequences for the driver during the rollover (ROPS). The narrow-track tractor, designed to operate in vineyards and orchards, is a tractor category with a very narrow track width and the risk of rollover is higher. The aim of the study was to evaluate the compact narrow-track tractor types commercially available, designed to mount a cantilever engine in the forward position with effects on the Center of Gravity (CoG) because more than 50% of the tractor weight is loaded on the front axle, and, specifically, the articulated narrow-track tractors where the stability is affected by the pivot point connecting the two tractor bodies. As a consequence of the typical tractor design of articulated tractors, during the steering action the line passing through the front and rear tire contact points on the ground changes, influencing the tractor’s stability. The approach of the research was based on reproducing the lateral stability tractor condition by developing a kinematic model, with the goal to virtually simulate the tractor behavior and to calculate the lateral stability angle for articulated tractors. The innovative contribution of this paper was the tractor articulation joint modeling, assuming a virtual pivot point to reproduce two relatives’ rotations between the front and rear bodies of the tractor: vertical (yaw angle) and longitudinal (roll angle) rotations. The lowest value of the stability angle was 39.3°, measured at −35° yaw angle. The model at the tractor design stage will allow adjusting of the tractor parameters to improve the lateral stability performance.

Vehicle rollover is a common event in agriculture due to the variability of the pedological and orographical condition of the soil and/or to human incorrect practices. Tractors since 1930 have been considered at risk of rollover and they were fitted with roll-over protective structures (ROPS) which had to provide a survival volume for the operator. The Directive 2006/42/EC currently foresees the same approach for the agricultural machines when a risk of rollover is recognised. The main purpose of the work was to identify a suitable survival volume for small multi-tasks agricultural vehicles. The study carried out evidenced that the design and operational characteristics of these small vehicles require an ad hoc survival volume. Indeed the official volumes already consolidated for tractors and other machines, even if in all cases consider the dimension of a seated male operator, had to be adapted in respect to the space actually provided by the features and operational characteristics of the small sized vehicles in order to preserve their functionality in the normal operation.