Analysis of Drive Axis Alternatives in the Problem of Traction When Towing in a Steep Grade

Traction alternatives viewed from the perspective of drive axis choice remain an important topic in vehicle design. Electric and hybrid vehicle design alternatives have been proposed where each axis is powered by a different engine (electric and internal combustion). This draws attention to the problem of gradeability in alternative drive axis configuration when the vehicle is towing in a steep grade, to avoid slipping. The paper demonstrates the use of analytical methods to analyze the fundamental mechanical relationships that govern the gradeability of a two axis vehicle towing a single axis trailer, considering three drive axis alternatives (Front Wheel Drive-FWD, Rear Wheel Drive-RWD and All/Four Wheel Drive-AWD/4WD). The differences between FWD and RWD are small, supporting the 4WD option as the most robust alternative, calling for 4WD selection mode in Electric Vehicles