The Effect of Friction on Actuation Torques of Foldable Rollover Protective Structures

Abstract

Abstract. The number of fatal tractor rollover accidents with an inoperative foldable rollover protective structure (FROPS) has increased sharply in recent years. Operators frequently leave the FROPS in the folded-down position after lowering the FROPS to pass a low overhead obstacle. One possible explanation for leaving the FROPS in the folded position is that raising and lowering the FROPS is a time-consuming and strenuous process. The actuation torques required to raise and lower a FROPS are not well known and may be influenced by friction. The actuation torques of ten FROPS from four different models were measured. One model FROPS was tested on seven different vehicles, and three models were tested separately. The dynamic and static (initiation and holding) actuation torques were measured to evaluate the effect of static and kinetic friction on actuation torque. The dynamic actuation torques were measured before and after greasing the FROPS. The proposed instruction to measure the actuation torque based on OECD Code 7 was evaluated. Results showed that friction has a significant effect on the measured actuation torque and can increase the actuation torque by up to 212%. The friction varies between FROPS of the same model, which is due to variations in the manufacturing, maintenance, and age of the FROPS. The friction force could be decreased by greasing the FROPS, and decreasing the friction increased the lowering resisting torques and decreased raising torques of FROPS. The measured actuation torque based on OECD Code 7 instruction (static holding) is not a constant value. The dynamic method is recommended for measuring FROPS actuation torques. Keywords: Actuating torque, Foldable rollover protective structure, FROPS, Safety, Standards, Tractor.

Safety Vision of Agricultural Tractors: An Engineering Perspective Based on Recent Studies (2009–2019)

“…Other studies dealt with the analysis of the actuation forces needed to operate foldable rollover protective structures (FROPSs) [97,98], whereas Pessina et al [99] compared the handling load of different narrow-track tractors' FROPSs with the related grasping area. Furthermore, two studies describing field tests aimed at setting a warning device based on the operative conditions of the tractor [100,101] were included in this research stream.…”

“…The latter issue was stressed by different studies, shedding light on the necessity of updating technical standards such as the OECD Codes, taking into account the features of modern tractors (e.g., the tractor ballast [120]) and how they are used in practice [65,118]. Similarly, the lack of a clear reference for dynamic tests of ROPS was outlined [117,126], while the inadequacy of the standards related to FROPSs testing (e.g., concerning the grasping area [99] and the actuation torque [97]) needs to be further investigated.…”

Tractor Rollover Protection: Is the Incorrect Use of Foldable Rollover Protective Structures Due to Human or to Technical Issues?

“…Regarding the reasons to leave the FROPS in the folded-down position, Khorsandi, Ayers, Jackson, and Wilkerson (2016) argued that the process of raising the FROPS is time-consuming and strenuous for the operators, also because of the actuation torques required to raise and lower the foldable frame (Khorsandi & Ayers, 2018). A multidimensional study conducted in a group of Italian agricultural operators (Caffaro et al, 2019) showed that handling the FROPS was not associated with a high perceived effort but it was considered by farmers time-consuming and uncomfortable.…”