Design, Analysis and Testing of a Formula SAE Car Chassis

This paper is taken from work completed by the first author as a member of the 1999 Cornell University Formula SAE Team and discusses several of the concepts and methods of frame design, with an emphasis on their applicability to FSAE cars. The paper introduces several of the key concepts of frame design both analytical and experimental. The different loading conditions and requirements of the vehicle frame are first discussed focusing on road inputs and load paths within the structure. Next a simple spring model is developed to determine targets for frame and overall chassis stiffness. This model examines the frame and overall chassis torsional stiffness relative to the suspension spring and anti-roll bar rates. A finite element model is next developed to enable the analysis of different frame concepts. Some modeling guidelines are presented for both frames in isolation as well as the assembled vehicle including suspension. Finally, different experimental techniques are presented to determine what stiffness is actually achieved from a constructed vehicle. A comparison of frames tested in isolation versus whole vehicle testing is made, and a simple whole-car chassis torsion test method is discussed.