Covering 3000 km between Darwin and Adelaide
The challenge is simple. Cross the Australian desert as fast as you can without one drop of fuel. Fourteen selected engineering students of Groep T Engineering School in Leuven, Belgium, took up the challenge to hunt for a medal in the World Solar Challenge, the world championship for solar-driven vehicles.
From their predecessor team they inherited a solid, proven vehicle design along with ample know‑how and experience. In partnership with high-tech companies such as Nikon Metrology, these youngsters succeeded in developing the second generation of the solar race car, named Umicar Infinity.
“The focus of our engineering teams in creating the Umicar Infinity was somewhat different than what is usual in regular automotive vehicle development programs,” stated Koen Van Beneden, Head of Solar Team Marketing.
“To get the most out of limited solar cell power, our race car was engineered specifically for low weight, little aerodynamic
resistance and high energy efficiency of vehicle driveline mechanisms. The Umicar Infinity is a one-seater that only weighs 175 kg, and features dynamic wind resistance that is roughly six times better than premium serial-production sports cars. With just the electrical power of a vacuum cleaner available, the Umicar Infinity is capable of reaching speeds higher than 140 km/h!”
Pertinent need for metrology-level alignment
To create the race car’s rigid, light-weight space frame, engineers used extruded aluminum tubes that were welded together. To compensate for slight frame deformation due to the welding heat, engineers relied on technology from Nikon Metrology. After welding, the positions of key locations on the frame were measured using the hand-held SpaceProbe of the Nikon Metrology K-610 Optical CMM system.
This optical metrology solution operates using a fixed carbon-fiber structure that houses three linear CCD cameras. Through triangulation, the system is able to accurately track the positions of infrared LEDs integrated into the SpaceProbe that is held onto the frame point being measured. Based on the acquired frame coordinates, the team was able to verify specific shape characteristics of the frame. Engineers additionally measured datum points to define
reference planes to be used for alignment purposes later on in the subsystem assembly process.
According to Pieter Vangeel, Team Manager of Solar Team, alignment was critical, in particular when connecting the completed frame to the suspension subsystems. “The suspension units play an essential role in aligning the three wheels with respect to the body of the race car. The powered rear wheel has a swing-arm suspension unit, while a double-wishbone suspension unit keeps the front wheels in position. Special attention went to the locations on the frame where suspension parts need to be fitted, because they require perfect orientation to one another. Therefore, we relied on the Nikon Metrology K-610 system to accurately identify the positions of all suspension attachment points on the frame structure. With this information in hand, we were able to weld all connections between the space frame and the suspension units with high positioning precision.”
Further pushing race car’s operation efficiency limits
The next highly sensitive alignment job was the positioning of the aerodynamic body shell around the rest of the vehicle. Pieter Vangeel noted that the Nikon Metrology equipment, once again, proved very useful in adding metrology accuracy to the attachment procedure of major vehicle subassemblies. “Precise measurements and finishing are an absolute must in order to ensure that the wheels
are in their optimum position and orientation. Even the slightest wheel misalignment causes excess tire wear and mechanical friction. This means that we would potentially lose valuable time with additional tire exchange stops, each requiring about ten minutes standstill time. And additional mechanical friction would decrease the dynamic performance of the Umicar Infinity, reducing vehicle speed through lower operation efficiency.”
“Nikon Metrology truly helped Solar Team to develop a better race car,” Pieter Vangeel stated when asked about the role of Nikon Metrology in this ambitious Umicar Infinity project. “Metrology-level assistance in assembling main vehicle subsystems was essential in obtaining higher precision and better vehicle dynamics. We took the mechanical accessory gauge, which was used in Nikon Metrology alignment test campaigns, with us to Australia to perform wheel alignment tests in between racing days. The gauge allowed us to re-establish the original alignment, compensating for any wheel misalignments that resulted from mechanical and tire wear. Although measurements only take minutes, the impact of precision alignment has a significant impact on the competitive edge of our race car. We are convinced that this will propel the Umicar Infinity to success in the Solar Challenge world championship race.”