Driving to Win
Since 1990, the student-directed University of Minnesota Solar Vehicle Project’s mission is to teach its members about engineering and project management while creating solar-powered cars that continuously improve upon previous designs. The team is the first American team to compete in the Cruiser Class at the World Solar Challenge. In addition to speed, this class places emphasis on practicality.
The standard for analyzing the University of Minnesota solar vehicle’s suspension has remained the same throughout the team’s history. Little testing has been conducted to actually validate this standard. The team decided that strain measurements should be taken on the a-arms of the solar vehicle’s suspension to determine if parts are over- or under- engineered. This will ensure the team is designing with realistic loading conditions and making the car as efficient as possible.
The tee rosette strain gages provided by Micro-Measurements were bonded to 7075 aluminum and 4130 steel suspension links using the installation kit provided. To compensate for temperature while measuring axial loads, the team wanted to use a half Wheatstone bridge configuration. The tee rosettes minimized the number of gages needed for this setup, which reduced installation time and potential errors.
The team used a tensile test machine to generate a calibration curve for each link with known loads. The components were then reinstalled for testing in a nearby parking lot. In each trial, the driver maneuvered over a piece of wood to simulate a bump and then ended with either a hard brake or turn.
The results implied that the theoretical loading conditions used are realistic and should continue to be utilized for design. In addition, weight can now be reduced from components with confidence to allow for a more efficient design for future cars.