Round shaped Rolling Over Protective Structures on modern tractors

Newly designed tractor protective structures have often a shape almost round, but the drawings in the OECD ROPS Codes refer only to cabs and frames in the shape of a rectangular box with straight edges and corners. The doubt is over where to apply loads when the ROPS is round in shape, because the test engineers have sometime to interpret the codes instead to fulfill it. The dinamic of the overturning for a round ROPS seems to be a continuous action between the first point of contact with the ground and the final point, that could not be defined as an impact stage because the ROPS does not support a dynamic impact force. Therefore a testing procedure for highly rounded protective structures is advisable for defining the points and the directions of loads application and also for verifying the need of a crushing test.