Dynamics

21 03 2011

Tires: A race car must generate large forces in order to achieve the desired lateral and longitudinal accelerations. This is a result of Newton’s Second Law of Motion. All such forces are generated by friction between the tires and the road surface. Maximizing this friction, or grip, between the tires and the road improves the cornering, acceleration, and braking performance of a vehicle. Extensive analysis has been done to evaluate several tire options for the Ravens Racing cars and to determine how to set them up so that they are operating at the peak of their capabilities. This analysis involves determining the best rubber compound, tread width, inflation pressure, and wheel alignment for maximizing the performance of the vehicle. For the 2011 Formula Hybrid competition, 20.5×7.0-13 Hoosier bias ply road racing slicks have been selected. These tires employ an extremely soft rubber compound to provide grip levels far beyond those of consumer street tires.

Shocks, Springs, and Anti-roll Bars: Similar to previous years, the RR11 car’s suspension will feature an independent, double, unequal length control arm setup that utilizes a system of pushrods and bellcranks to transfer the wheel loads to the horizontally mounted springs and dampers. Front and rear anti-roll bars will also be implemented on the car in the form of a t-bar to reduce body roll and aid in cornering. This year’s design will feature a spring and bellcrank combination that will allow the car achieve a slightly lower ride rate while the t-bars will be sized to deliver a stiffer roll rate than used in the past. Manufacturing of the suspension components has already begun. The springs and dampers have been received and the bellcranks are built and ready to be installed on the car. Manufacturing of the t-bars is expected to be completed shortly.

Figure 1: Suspension components including damper, coil spring, and bellcranks

Kinematics: A Short-Long Arm (SLA) suspension system has been carried over from previous years since the SLA design is generally considered to be the most flexible to tune. Motion of RR11 Suspension system is simulated using suspension simulation software such as OptimumK. Static wheel alignment settings for optimum performance and stability have been determined from the results of simulation and load transfer calculations.

Compliance: Carleton University Formula Hybrid has added the study of compliance to its race team this year to better understand load-induced deformation in our race car designs. As the design evolves each year, Raven’s Racing pushes performance limits higher with each step. In order to achieve the highest level of competitiveness, the dynamic behavior of the car must be understood in great depth. Compliance is the study of how the vehicle is deforming under racing loads. With this knowledge, designs can be fine tuned, and modified to perform above the competition. Progress has been made in the design and operation of a static test apparatus used to simulate dynamic loads on the car. It enables our team to study and analyze compliance effects. Initial testing has been carried out on RR10 to determine the compliance camber, and body roll hysteresis as a function of lateral loads. The testing was successful in gathering data that can be used for design and tuning modifications.

Figure 2: Compliance test setup using tension cable and load cell

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