Design of Borealis III
Borealis III was the University of Minnesota's 7th generation solar vehicle. The design of Borealis III began in the fall of 2003. Work on Borealis III will be completed in September 2006.
The Borealis III aerodynamics team combined over ten years of UMNSVP design experience to come up with a new hybrid shape that continues to improve on aerodynamic performance. Utilization of CFX and Pro-E allowed the team to quickly analyze and compare three different distinct body shapes: the classic flat body and bubble canopy, the classic manta, and the new hybrid. This software was used to modify these models to produce the final product that has been made into a female molds which were used to produce the actual vehicle body through a Kevlar and nomex core lay-up process. Kevlar was chosen this year to be used on the top half of the car due to its lack of conductivity and its light weight. The result has been a very significant reduction in weight. The bottom shell was constructed using carbon fiber to increase the rigidity of the body.
One of the parts that the Minnesota team takes great pride in is the car’s solar array. The UMNSVP is one of the few collegiate teams that research, test, string, encapsulate, and assemble their entire solar array in-house. The array team worked with other design teams within the project to produce a solar cell laminator and a solar cell power curve tracer machine. Both machines have produced positive results in test pieces which have been constructed from older low efficiency cells that are similar in size and shape to the cells that are planned on being used in the new array. The array team also worked very hard to integrate the solar panel module layout with the car body. The end result was an increase in the total number of solar cells fit to the car compared to Borealis II, thus increasing overall power performance.
After a producing a simplified and reliable electrical system for Borealis II, the electrical team shot for loftier goals for Borealis III. This group designed new circuits that will be running on C-code instead of assembly programming language. Improvements to the power trackers and communications systems were integrated with a new custom in-wheel motor (which was used on the summer trial run of NASC), motor controller, driver and diagnostic display, and a new battery pack. More so than in past years, the electrical team integrated designs with the mechanical team to strategically place primary components and cabling. The purpose of this was to properly set the center of mass of the car to give maximum stability and to produce a cleaner finished car while increasing electrical system efficiency and functionality. The team is extremely proud of the culmination of over 5 years of research, field testing, and refinement of the power trackers and motor, both of which were originally designed by UMNSVP members who have since gone on to pursue other endeavors in their academic and professional careers.
The mechanical engineering team produces one of the most reliable and cleanly designed cars in collegiate solar racing. After the excellent survivability and reliability of the Borealis II, the group continued to optimize previous designs. Since every member took on a new system this year, every member learned something new. Breakthroughs for the new car included increased utilization of composites and lightweight metal alloys in suspension systems, optimized suspension geometry for "no-scrub" movement, improved weight savings in the vehicle’s structure, and increased cross-functional integration among the four engineering teams. The mechanical design team also made a CNC machined front suspension upright that weighs less than 1.2 pounds, a small improvement over Borealis II’s upright, which weighed 1.27 pounds!