Design of the Wild Solarcat-A Solar Electric Vehicle for GM Sunrayce 1990

As participants in GM Sunrayce 1990, students in Villanova University's College of Engineering were required to design, build, and race a solar powered electric vehicle. Since the car was required to race over an 1800 mile distance, reliability was an important design issue. Other design features of equal importance were driver safety and vehicle stability. GM also imposed additional design constraints such as minimum braking distance and maximum dimensions on solar panel and vehicle size. In this paper we will describe the tradeoffs made in designing our solar electric vehicle. This will include design considerations regarding both the mechanical and electrical subsystems separately as well as overall system integration.

Our final design comprised a modified airfoil body made of a lightweight kevlar and nomex honeycomb sandwich supported on an aluminum tube space frame. The solar panel consisted of a large, flat panel integrated onto the back of the body, with additional side panels used to provide extra power during early morning and late afternoon conditions. A lightweight, brushless DC motor was used to drive a single rear wheel via interchangeable gears. This motor was capable of delivering 10 hp peak and weighed in at only 13 lbs. Silver zinc batteries were mounted on a composite tray in the center of the frame and provided power for acceleration, hill climbing, and backup power during poor insolation conditions. The wheel hubs were designed to be quick release for rapid tire changing. Low rolling resistance tires inflated to a pressure of about 90 psi were used with a composite center disk to minimize tire rolling resistance and tire aerodynamic drag. A four wheel desing was selected. The front wheels were aligned with the rear wheels to minimize drag but system, using double A-arms was chosen for all four wheels. In this lessons learned from designing and building the vehicle will be presented.