Subteam Updates Before Unveiling
Preparing the car for the May 2 unveiling took lots of long hours. Here, Graduate Advisor Scott Grabow solders solar cells to the array. On this page, learn more about the team's preparation for the unveiling.
The Aurora-II's iridescent blue solar array looks great and appears seamless, but it represents months of painstaking work.
During the month of April, the solar cells went through their final cuts, preparing them for soldering. The soldering process took many hours. We first had to join the flat ribbon wire to each cell, and then to connect one soldered cell to the next to create a string of soldered cells. The solar array consists of about 130 of these strings of soldered cells.
Three strings were grouped together and mounted to a thin Tedlar(R) film, making a larger module. This module construction strengthened the cell groups and made them easier to transport from the assembly lab to the Aurora-II shop. This construction also isolated the cells from the vehicle's shell, protecting the very fragile cells from vibrations and elements.
The 47 modules were placed one-by-one on the shell. Holes were drilled into the shell at the end of each string within the module to facilitate interconnections between the strings. After the holes were drilled, the module was fastened to the shell with 3M's Very High Bond joining tape. The team worked roughly 80 hours within one week to attach the 47 modules and ensure the electrical connections were functioning properly.
After the 47 modules were joined to the shell, the entire array was encapsulated. This was necessary to further strengthen the fragile solar cells and protect them from dirt and moisture. We used an optical film along with an adhesive mixture (a silicone-based, two-part adhesive with the consistency of Karo syrup) which was poured on the array and spread evenly with a squeegee. When the adhesive and film were spread evenly, the entire shell including the solar array was vacuum-bagged to keep pressure on the film and adhesive until it cured.
The solar array had is first taste of sunlight during the unveiling. Since then, we have been testing the array both exclusively and with the other components of the vehicle.
Aero Team Enhances Aerodynamics, Safety of Aurora-II
The Aero Team worked diligently to prepare the shell in it's final racing configuration for the unveiling.
Our final tasks were manufacturing wheel fairings and attaching the shell to the chassis. With the wheel fairings, our main concern was aerodynamics; with the shell is was safety.
To meet the Sunrayce regulation of a seven-second exit capability, we designed a quick release system for the shell. One side is hinged, similar to a clam, to allow driver access. The shell tips up via a gas charged shock, allowing the driver to exit quickly.
Electrical Team Meets Challenges, Get Aurora-II Running
The Electrical Team moved at the speed of light to install the electrical system so that we could test and safely run the car for the May 2 unveiling. Since spring break, we had two major projects: building a battery charger compatible with our system and developing a testing scheme for the motor.
It was difficult to find a battery charger capable of charging seven batteries with a constant voltage and current profile, so the Electrical Team decided to build our own charger using two ferro-resonant transformers and materials from the Electrical Engineering department.
Our second major project was developing and implementing a
testing scheme for solar car motors. The magnitude of this project was significantly greater than we had expected. During spring break we hoped to gather data on the motor's performance. However, this took three times longer than we had hoped and planned. We used a dynamometer from the Mechanical Engineering department to calibrate all the components and receive accurate measurements.
The great time investment was well worth it, because we now have accurate performance information for our motor as well as a motor testing scheme for future projects.