Lateral stability performance of narrow-track tractors

A tractor losing lateral stability starts to rollover. It is a matter of fact that tractor lateral rollover accident is one of the most frequent causes of death and injuries for the farmers. Consequently tractor is fitted with a specific protective structure to minimise 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 narrow-track tractor types commercially available, including, the compact narrow-track tractors, 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 during the steering action the line passing through the front and rear wheel-ground contact points changes influencing the tractor rotation. Moreover the cab ROPS fitted on the articulated narrow-track tractor with its additional devices (air-conditioning system, filters, heating system etc..) influences the tractor CoG position and finally the tractor stability. The approach of the research was based on reproducing the lateral stability tractor condition by developing a kinematic model, with the goal to virtual simulate the tractor behaviour, calculating the limit angle of inclination for each tractor type. The kinematic model calculates the lateral stability limit angle for articulated and non-articulated tractors and if used during the tractor design phase allows adjusting the tractor parameters improving the lateral stability performance.