Testing of a Suspension System Specifically Developed for an Electrically Driven race car

The Lessius Racing Team (LRT), a group of enthusiastic students from Lessius Mechelen | Campus De Nayer, is taking part in the Formula Student Competition, an educational competition requiring students to build a race car prototype as a team, and then sell it.

The mission of the Formula Student competition is to encourage young people to step into the technical business world, challenging them to design, build, finance, present, and compete as a team with a small, single-seat race car in a series of static and dynamic events. LRT is participating in the 1A class, meaning they will develop new and novel powertrain technologies that result in race cars with low carbon emissions, as defined by the Class 1A rules.

Validation of FE Models by Using Strain Gauges

The Lessius Racing Team is using strain gauges and the MGCplus data acquisition system from HBM for validating test results

A crucial part of designing an efficient race car is the suspension system. It plays a part in reducing both weight and friction, optimizing vehicle performance. To reduce not only the total weight of the race car, but also the so-called unsprung mass, as little material as possible has to be used in the construction of the suspension system. A low unsprung mass is important, to ensure fast response of the suspension system to bumps and potholes, maintaining constant contact of the tires with the racetrack, and providing maximum vehicle control.

The stiffness of the suspension is another important part, as deformation in the suspension would influence the geometry of the car setup (such as caster, camber, and toe), which would adversely affect handling and rolling friction. In addition, the suspension has to handle all the forces acting on the race car to keep it on track when turning into corners at high speed.

To ensure the maximum weight reduction does not affect the structural strength, modern finite element (FE) simulation packages have been used in the design. Only one link in the chain for developing a sturdy, but lightweight, suspension was missing: validation of the FE models to ensure the models and the design are correct.

This validation, offering certainty about the design that the team was looking for, has been achieved by applying strain gages to different suspension parts. The choice was made to perform a test with direct loading by putting weight on the vehicle while measuring the force actually acting on the full suspension with weighing plates under the wheels.

Further Tests for Increasing the Vehicle Performance

Screen of the catman software for acquiring measurement data

The measured forces acting on the wheels were used as input parameters for the FE model simulation to correlate the material deformation measured by the strain gauges with the corresponding locations in the FE model. This approach offers a well-defined test scenario that simplifies the correlation of simulated and measured data.

The next step is to instrument the race car with further data-acquisition equipment to perform measurements in real-life use cases  actually driving the vehicle on a race track. This has already been discussed, and will be an assignment for next year's racing team. For now, the static tests have proven to be a great success, and ensured structural stability of the current suspension design.

Further dynamic tests will help the team minimize the weight and increase the vehicle performance without risking component failure or vehicle misbehavior due to a lack of structural stiffness.

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