Why Torsional Stiffness?
When a car accelerates through a turn, the lateral acceleration causes an increase in normal force on the outside tires and a decrease of the same amount on the inside tires. For a vehicle chassis, especially for racing, the suspension roll stiffnesses front and rear have direct impacts on handling through a corner — and for that to hold, the chassis itself needs to be torsionally stiff.
Consider a vehicle tube frame as a spring in series with the front and rear suspension springs.
Given that F = k_eq × x, a stiff chassis would produce different resultant forces compared to a softer one. For a soft chassis, the frame twists when the vehicle is cornering. That gives a difference in compression between the front and rear roll springs, making them less effective to tune. For an ideal stiff chassis the spring travel would be equal, so lateral load transfer depends on roll stiffness alone. So I aimed to test, validate, and iterate our FSAE tube frame to be stiff enough to transmit the torques.
Approach
First, I ran a number of static FEA simulations analysing the chassis with a torque load applied to the front uprights. By constraining the rear of the vehicle and allowing rotation around a fulcrum at the front, I could simulate the load paths of a cornering vehicle.
Then I managed the design and manufacturing of a test fixture to experimentally validate those simulations and bring them closer to accurate numbers.
Process
Images for the test fixture are pending due to the FSAE EV Competition in Michigan. Here are some photos from the event, and of the chassis.
The results of this test will assist chassis design in future years as I improve the simulation accuracy — especially useful as I move on to be Gaucho Racing’s Chassis Lead for ’26–’27.