Non-continuous rolling in modern narrow-track tractors

Tractor rollover is one of the most hazardous event for the operator. Roll-Over Protective Structure (ROPS) was introduced to protect operator passively. In the specific case of protective structures in front of the drivers and fitted on wheeled narrow-track agricultural tractors, ROPS has to avoid the non–continuous rolling in the event of lateral rollover. Mathematical Model is included in the preliminary tests of the standardised testing procedures issued by the Organisation for Economic Co-operation and Development in order to check non-continuous rolling behaviour in narrow-track wheeled agricultural tractors. Modern narrow-track tractors fitted with rubber-tracks are currently designed but the standardised calculation does not cover the rubber-track tractors. The aim of the evaluation was to analyse the lateral tractor rollover behaviour as affected by the replacement of the tyres with the rubber-tracks. In the tested tractor the fitment of rubber-tracks replacing the rear wheels showed to increase the tractor mass and to affect the position of Centre of Gravity causing a downward and rearward shift with respect to the equivalent wheeled tractor. The track-ground interaction was different compared to the tyre-ground one. Mainly, the behaviour of the rubber-track with respect to the tyre at the state of unstable equilibrium under full load caused the rotation of the tractor around the outer edge of the track.