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In order to better understand the complexities of modern tractor rollover, this paper investigates the energy absorbed by a Roll-Over Protective Structure (ROPS) cab during controlled lateral rollover testing carried out on a modern narrow-track tractor with a silent-block suspended ROPS cab. To investigate how different tractor set-ups may influence ROPS and energy partitioning, tests were conducted with two different wheel configurations, wide (equivalent to normal 'open field' operation) and narrow (equivalent to 'orchard/vineyard' operation), and refer to both the width of the tires and the corresponding track. Dynamic load cells and displacement transducers located at the ROPS-ground impact points provided a direct measurement of the energy absorbed by the ROPS cab frame. A trilateration method was developed and mounted onboard to measure load cell trajectory with respect to the cab floor in real-time. The associated video record of each rollover event provided further information and opportunity to explain the acquired data. The narrow tire configuration consistently subjected the ROPS cab frame to more energy than the wide tire arrangement. To better evaluate the influence of the ROPS cab silent-blocks in lateral rollover, static and dynamic tests were performed. The results confirm that tires influence the energy partition significantly and that further understanding of silent-blocks' dynamic performance is warranted.

Tractor rollover is one of the most hazardous events for the driver. The rollover protective structure (ROPS) was introduced to passively protect the driver. In the specific case of two-post protective structures fitted in front of the driver on narrow-track wheeled agricultural tractors, the ROPS has to avoid non-continuous rolling in the event of a lateral rollover. In order to check non-continuous rolling behavior in narrow-track wheeled agricultural tractors, a mathematical model is included in the preliminary ROPS tests of the standardized testing procedures issued by the Organization for Economic Co-operation and Development (OECD). A recent approach in the design of narrow-track tractors is the fitting of rubber tracks. A safety issue consequent to this new arrangement is that the standardized calculation does not cover narrow rubber-tracked tractors because it was originally developed assuming only the behavior of the tire in a lateral rollover. The aim of this study was to extend the field of application of the standardized calculation for non-continuous rolling behavior, allowing rubber-tracked tractors to be fitted with a front ROPS suitable for operation in narrow orchards and vineyards. The effect of track-ground interaction compared to tire-ground interaction was evaluated. The track shape and non-deformed behavior of the rubber track at a state of unstable equilibrium under full load caused the tractor to rotate around the outer edge of the track; therefore, the tipping axes and wheel characteristics in the original mathematical model were revised. The tracked tractor checked with the revised model required a higher ROPS with respect to the equivalent wheeled tractor to obtain non-rolling behavior. The ROPS needed to be increased by 0.28 m to meet the safety requirement., (Copyright© by the American Society of Agricultural Engineers.)