Problem

The current chassis design (F25) suffered from integration issues with the engine and low performance metrics for torsional stiffness and mass. The proposed chassis design (F26) sought to address these issues by redesigning the engine bay and running parametrized models of the chassis with Ansys.

Integration Issues

To address the integration issues, critical bounding boxes were laid out in SolidWorks, including the driver, engine, suspension points, and the half shaft and differential. A chassis skeleton was created to interface with these critical regions, where the lines represent centerlines of tubes.

These lines were assigned tube cross sections, each with their own wall thickness and outer diameter.

The engine fit was resolved in the F26 design by expanding the rear bay through shortened control arm linkages and moving the main roll hoop towards the front of the car. This change increased clearance between the engine and the chassis, allowing for increased maneuverability during install and serviceability when assembled.

Performance Criteria

The line geometry was analyzed with FEA using 1D elements in Ansys Mechanical. Ansys Parametrization allows cross section dimensions (wall thickness and outer diameter) to be parametrized and iterated through to generate a plethora of unique chassis design. Since a majority of the chassis is regulated by the FSAE rules, only a selected portion applied the parametrization.

A representative torsion loading case was applied on the chassis to determine the corresponding torsional stiffness. Thus, each generated chassis has a particular torsional stiffness and mass based on its corresponding cross sections, permitting direct comparison against one another.

Results and Impact

Ansys produced 100s of chassis designs, plotted on the graph below. The best cross section layout would be the chassis that has the best torsional stiffness and lowest mass. The vehicle dynamics team established a torsional stiffness goal of 2700 Nm/deg, narrowing the chassis selection to the lightest alternative that meets this specification.

Below is the comparison between performance parameters of the F26 and F25 designs. The increased triangulation on F26 allowed for better torsional stiffness characteristics, while also decreasing mass by implementing lighter tube cross sections.

Ansys Parametrization for FSAE Chassis Design