Abstract

BAJA SAE is an engineering competition that tasks team with designing single-seat all-terrain vehicles that partake in a variety of events, predominantly on soft soils. Events range from (off-road) land maneuverability, hill climb, tractor pull, and timed acceleration. Tire-terrain interaction strongly influences the performance of off-road vehicles. Tire terrain traction is limited by the mechanical properties for soft soils; therefore, understanding tire-terrain traction forces is important for assessing vehicle performance. Using the stress integration method (SIM) initiated by Bekker and developed by Wong, this paper analyzes the performance of BAJA SAE tires using Bekker’s defined terrain measurements for soft soils. The relative rigidity of the tire versus the soil, in terms of pressure, was compared for operating conditions and used to determine the tire state (rigid wheel or pneumatic tire). Tire state determines shape of the tire-terrain interface, and integration limits. Based on the operating conditions, the tire sinkage into the soil was calculated and used to determine compaction resistance, tire hysteresis, and normal pressures along the tire-terrain interface. Using the SIM, the longitudinal and lateral tractive forces vs the slip ratio and slip angle, respectively, were calculated for a range of operation conditions. The tire-terrain traction forces were evaluated for different tire diameters and tire pressure for a range of soil types. The described process can be used to predict performance for BAJA SAE teams participating in specific events and the results can be used as a basis for selecting tires and tire pressure for dynamic events.

This content is only available via PDF.
You do not currently have access to this content.