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A feature of Baja SAE, and other off-road racing series, is a dynamic traction event. Usually some sort of pull-test device is towed in this event, and design of this device has a controlling influence on the performance capability of each vehicle in the field. Pull-test devices are usually designed to be progressive so that starting is easy, but the pulled load gets higher the further the tow proceeds. Pull-test devices must also be mechanically designed to suit the efficient operation of the traction event (hitching and resetting). This paper develops the operating and design theory of a new pull-test device, the log pull.

Selection of springs and dampers is one of the most important considerations when finalizing a race car suspension design. It is also one of most complex due to the dynamic interaction of the vehicle with the ground. Current tuning methods for spring and dampers' effect on vehicle ride can be based on simplified dynamic models of the vehicle, such as the quarter-car model. While efficient computationally, the traditional quarter-car model does not account for the non-linear variation in grip seen by a fluctuating contact-patch. Both amplitude and frequency of suspension oscillation contribute to loss of tire grip. The method can be improved by incorporation of a dynamic tire model, though resulting in non-linear effects. An improved ‘rolling quarter-car’ model is created, which includes the effect of dynamic tire forces in the analysis of improved grip. Using typical Formula SAE race car, characteristics as a test case, a linearized dynamic model is made.

Even with relatively unrestrictive rules in the Formula SAE competition, established teams are fighting diminishing returns in vehicle mass and engine horsepower. The typical FSAE vehicle incorporates a six speed gearbox, yet reaches a (course-limited) top speed in competition of only about 110 kph. Selecting a final drive for this top speed would result in 5 gearshifts in less than 4 seconds. As a result, final drive ratio is very sensitive to shift delay time. Although vehicle mass, engine performance and traction still play a major role, a typical FSAE vehicle acceleration is significantly limited by the time it takes to complete a gearshift.