Analysis of tire/gripper slip forces during the handling of large off-the-road tires

Abstract

Handling large off-the-road tires poses significant safety risks in surface mines, often leading to fatal accidents. This study aims to scientifically address the industry-wide knowledge gap regarding the impacts of various operational and tire parameters on tire handler gripper and tire traction performance. The specific research objectives include (i) quantifying the maximum lift force under various pad-to-tire contact conditions, (ii) identifying critical parameters influencing the point of first slip, and (iii) offering suggestions for improving tire handling operations. To achieve these goals, a portable tire handling test rig weighing 7 t was designed, constructed, and commissioned. Subsequently, in July 2021, functional performance and initial tire slip tests were conducted at the service center of Bridgestone Mining Solutions Australia in Oxley, Brisbane. Overall, 44 lifting tests were conducted on new, semi-worn, and worn Bridgestone 42/90R57 tires using a Cascade 10 t H-Series tire handler. Further, a design of an experiment matrix was formulated to test the influence of various parameters on the slip force, which is defined as the point of the first slip. The investigated parameters included tire orientation (vertical or horizontal), tread surface (dry or wet), tire wear (new, semi-worn, or fully worn), and tire handling pressure (unpressurized standalone and 0, 5, 10, 15, 20, and 30 psi for the tire and wheel set). The results revealed that to mitigate the hazard of sudden pressurized air release, tires must be preferably lifted at the lowest pressure adequate for ensuring handling performance, preventing bead-seat displacement during lifting. Furthermore, the risk of bead-seat displacement was found to be higher when lifting tires from an initial horizontal position owing to the action of shear forces on the bead seat. Considering these factors, an optimal pressure of 10 psi was recommended for lifting semi-worn 42/90R57 tires vertically under both wet and dry conditions, contingent upon the use of a concave gripper design typical of the Cascade H-Series tire handlers.