Georgia Tech Solar Racing

Fig 1. SJ-1 Endeavour

Georgia Tech Solar Racing (GTSR) is a student-run team that designs, builds and races completely solar powered vehicles against other collegiate teams. All the design and fabrication work for the vehicles is carried out by students in Georgia Tech’s Student Competition Center. I became a member of GTSR during my freshman year, when the team was still working on finishing their first car, SJ-1 Endeavour, the team is currently completing fabrication of their second vehicle, SR-2. Over the next four years I held many engineering roles on the team - starting from just a member of the mechanical subteam, to leading a system design group, being chosen as part of two race teams, and finally leading the mechanical subteam. I also led the team’s finance and corporate relations subteam in my last semester as a part of GTSR.

Fig 2. SR2 Rendering

 

One of the first tasks I was given on the team was to analyze and redesign the wheel hubs used on the car for the new wheels and Michelin tires that had been donated to the team. Seeing the work I put into improving different parts of SJ-1, the captain asked me to lead the suspension design group for SR-2. As suspension design lead, I was responsible for ensuring the suspension, steering and brake systems of SR-2 designs met the regulations required and also integrated well with the aerobody and frame of the vehicle. The suspension design process started with determining the ride characteristics required and the options for suspension configurations available. The extreme aerodynamics required in solar car racing, create further restrictions for the suspension design. The carbon-fiber aerobody fitted around the entire vehicle creates a very tight space for the suspension to operate in. Coupled with the ground clearance required to not induce lift and minimize the aerodynamic ground effect, these constraints resulted in the selection of an unusual suspension geometry. A double-wishbone design was selected for precise control over the camber gain in cornering. However, both the control arms are located above the axis of rotation of the wheel. This suspension configuration results in large moments and reaction forces in comparison to those seen more conventional suspension configurations.

Fig 3. Front Suspension Assembly

Fig 4. Rear Suspension Assembly

Each suspension component was analyzed using FEA in Siemens NX to ensure that it could withstand the loads required by competition regulations. The American Solar Challenge dictates that all critical components be designed to withstand a minimum simultaneous 1G braking load, 1G cornering load and 2G bump load. The results of some of the simulations run can be seen below. The final suspension configuration selected incorporated a roll center of 3.9 inches, 1.13° of camber gain over the first inch of vertical travel and +3° of caster in the front to ensure that the steering autocenters.

FEA Simulation Results

Fig 5. Front Upright
Fig 6. Rear Upright
Fig 7. Front Upper Control Arm
Fig 8. Rear Lower Control Arm

In addition to designing the suspension, the suspension design group was responsible for designing the braking and steering systems of the car. In order to accomplish this a weight shift analysis was performed to determine the braking forces required. Using the turning regulations as a guideline, turning radius calculations were performed to select the gear ratios needed in the rack and pinion assembly used for steering. My tenure as Co-Mechanical Lead started around the same time as design for SR-2 was wrapping up and fabrication was about to begin. Since I was directly involved in the design of the suspension components, I took charge of the metal fabrication work required to build the car. This required me to source the right materials, and gain experience using machining equipment. For the more complex parts, I coordinated getting them machined at the Mechanical Engineering department’s machine shop.

Fig 9. SJ-1 FSGP 2015

During my last semester of undergrad, I noticed that the team was not in a strong financial position, and would be unable to continue fabrication of the car if the situation did not change. I volunteered to lead the finance and corporate relations subteam. During this semester, I managed the team’s $200,000+ budget, all purchasing requirements and also developed a comprehensive sponsorship strategy to be used by the team in the future. During this semester I was also able to secure the team over $50,000 in monetary sponsorships and another $50,000 in materials and supplies sponsorships.

While I was a member of Georgia Tech Solar Racing, the team participated in two races, but only managed to get a working car to one of them. Since then the team has competed in two more annual races. During the 2017 American Solar Challenge at Circuit of the Americas, Georgia Tech Solar Racing set a personal best record in the competition. They also won the award for most improved team since last year.