Development of a Test Stand for Determining the Torsional Rigidity of a Formula SAE Space Frame

This paper outlines the development of an economical and high-accuracy test stand to determine the torsional rigidity of a Formula SAE space frame. Originating as a final project from the Engineering Experimentation course at The Cooper Union, the student-designed and manufactured torsional test-stand has become a permanent fixture in the Automotive Lab. The test stand consisted of a lever arm rigidly attached to the front axle, which constrained it from rotation about the axle, in order to apply a torque to simulate suspension loading. The rear axle was fixed in all three degrees of translational freedom and two degrees of rotational freedom. The instrumentation consisted of nine low cost laser pointers attached along the length of the frame at key locations that projected onto graph paper to magnify the small angular deflections. Using basic mechanics of materials, a model relating the angular deflection and the applied torque was used in order to determine the torsional rigidity of the frame. The results include the determination of the torsional rigidity along the frame, the calculated torsional rigidity at the point of interest (the front axle), and a comparison to a finite-element model. The torsional stiffness at the front axle was calculated experimentally to be 1187 ft-lb/degree. The FEA model predicted a torsional stiffness of 1100 ft-lb/degree, which is within 10% of the experimentally determined value. The cost of the entire experimental setup was approximately $375, making it a low-cost solution to a typically expensive experiment. This experimental rig has become a research platform in The Cooper Union’s Automotive Lab with uses in various courses and high school level STEM outreach programs. Motivation The initial motivation for this experiment came from the ME160 Engineering Experimentation course at The Cooper Union. Engineering Experimentation places emphasis on “data collection and statistical reduction, computational methods, and written and oral presentation skills” 1 . The course grading relies significantly on a student’s ability to design, manufacture, implement, and present the results of a final experiment. The experiment itself was left open ended, allowing the groups of three to four students free rein to explore systems that they were interested in. The project team included three active members of the Formula SAE team at The Cooper Union, an extracurricular team that designs and builds a Formula style racecar. Therefore, the project team decided to pursue an experiment related to the suspension performance of the Formula SAE vehicle: designing an experiment to determine the torsional rigidity of the vehicle’s space frame.