A Mathematical Analysis of Off-Road Vehicle to Avoid “Hang Up” and “Nose In” Failures

The goal of this study was to determine the design constraints for the Georgia Southern SAE BAJA vehicle to operate in a rough terrain without unwanted direct body impact. The BAJA vehicle may encounter two distinct kinds of failure while climbing or descending terrain obstacles: Hang up failure, and Nose in failure. Hang up failure occurs when the bottom of the chassis of the vehicle makes contact with the obstacle. This occurs after the front tires have cleared the obstacle but before the rear tires have. This mitigates the pace of the vehicle but does not structurally threaten it. Nose in failure is when the protruding front bumper or “nose” of the vehicle makes contact with either the ground or the obstacle before or after encountering the obstacle. The possible ramifications of this event are much more disastrous than the Hang up failure. Nose in failure can send the vehicle into an end over end flip, or cause significant structural damage to the frame. Through a geometric analysis of the two situations, the critical values of parameters such as wheel diameter and nose length were determined and used as the boundary for the “safe zone” beyond which no failure can occur for a given obstacle geometry. It was found that for Hang Up Failure, higher values for angles β and β1 resulted in a greater traversable hill height, h. For Nose In Failure, lower values of angles β1 and α resulted in a greater allowable nose length, a.