Design and development of a tire changing mechanism for heavy vehicles

Abstract

At present, nearly 500,000 lorries, trucks and buses are registered in Sri Lanka. Trucks are widely used for transportation of goods around Sri Lanka. The tires in these vehicles must be removed during a service, repair or for a tire replacement. High loads and awkward postures from manually lifting, lowering, and handling of tires in many instances are linked to Musculoskeletal Disorders in humans. This research project aims at developing a suitable mechanism to minimize the human effort and to overcome the awkward postures and time consumed when changing truck tires. A survey conducted showed that, 86% had difficulties in mounting the tire onto the wheel studs and 76% had difficulties in loosening lug nuts. Also, 60% experienced lower back pain due to the tire changing process. Levering, lug wrenches, impact guns and torque multipliers are the current methods used, to change truck tires. It was found that, 60% of the employees faced problems when using the current methods to change tires in heavy vehicles. The required torque for loosening and tightening of lug nuts was estimated at 600Nm to 800Nm respectively. The worm gearbox strength calculations of the proposed design were carried using a torque of 1000Nm. Total weight of a semi-truck tire was taken as 600N and the tire lifting equipment calculations were performed to withstand a load of 1000N using a factor of safety of three. Finally, the design was simulated and validated through ANSYS modeling software using properties of mild steel as for the strength calculations.