87 Figure 120: Solar shuffler wiring Photo Credit – Richie Hongladaromp .... 104 Figure 145: ATN Solar Car Team & Shane Jacobson at Parliament house Photo Credit – Richie Hongladaromp ..
Solar Car Design & Aesthetics
Figure 40: Bird of prey concept sketch
This chapter outlines the project's design brief and its evolution over two and a half years of iterative design and validation It highlights the collaborative methods employed by the team to achieve the car's performance and desirability criteria, encompassing concept development, analysis, aerodynamic simulations, and ergonomic validation of the interior through physical construction and interaction with a seating buck.
In 2017, I completed my Bachelor of Industrial Design (Honours) with a project focused on a solar sports ute designed for the 2019 WSC Event, aiming to transform the iconic Aussie ute into a zero-emissions vehicle Attending the WSC event in Adelaide deepened my understanding of the competition's context and requirements My solar ute concept won the ATN solar car design competition; however, it was later determined that the ute's design would struggle aerodynamically due to its bluff surfaces, which create turbulence and increase drag Ultimately, a teardrop-shaped "coupe" design is more suitable for minimizing these aerodynamic challenges.
In February 2018, I initiated the development of new design ideas focused on low wind resistance, leading to the creation of the "Bird of Prey" concept to address ute concerns After a month of aesthetic refinement, the design prioritized aerodynamics to enhance air efficiency This innovative concept was unveiled at the Melbourne Formula 1 Grand Prix.
Figure 42: Solar sports Ute (2017 Honours project)
Prix, as the directional design of the ATN Solar car team The detailed development of this design took place through the inclusion of iterative simulations of aerodynamic Computational Fluid
The car's design leverages Computational Fluid Dynamics (CFD) to achieve a low drag coefficient (Cd) while minimizing frontal area While aerodynamic principles shape the vehicle's form, it also adheres to essential automotive design elements The aggressive styling features an angular front with sharp headlights and a prominent air passage that channels airflow beneath the car Rounded front wheelhouses seamlessly integrate into broad shoulders, creating a low, wide stance reminiscent of race cars, complemented by a sleek rear end resembling a flying buttress The glasshouse showcases a streamlined silhouette with a tumblehome inspired by supercar aesthetics To enhance the exterior, racing stripes adorn the bonnet, emphasizing performance and adding vibrancy to the character line-free surface.
Figure 432: Concept 3 “Bird of Prey”
Collaboration with Engineers to meet performance criteria
Designing vehicles for optimal aerodynamics presents challenges due to the impact on body form and aesthetics These vehicles must feature streamlined shapes that maintain balance from all angles to achieve efficiency Even small details, such as car size, ventilation openings, or minor creases, can significantly influence computational fluid dynamics (CFD) results Consequently, elements like mirrors, spoilers, and panel lines must be meticulously evaluated before integration into the design Thus, creating a solar car involves finding the 'Goldilocks zone'—making precise adjustments to ensure smooth airflow over the body with minimal disruption.
In July 2018, our team engaged in an intensive design blitz to develop a solution that could meet the challenging CdA target, as the initial "Bird of Prey" concept only achieved a CdA of 0.229 During this period, we proposed five new concepts, including two designed by myself: Concept 4, which took a futuristic approach, and Concept 5, a stylistic remodel of the Bird of Prey Ultimately, after conducting CFD analysis, Concept 5 was selected for its aesthetic appeal and potential to meet strict aerodynamic targets, achieving a CdA of 0.207, while Concept 4 had a CdA of 0.285 By October 2018, Concept 5 had undergone over twenty-five iterations, coming within 7% of the target CdA of 0.16.
In the design development process, achieving a CdA target of 0.16 was crucial to avoid delays in the ATN Solar Car Schedule CFD analysis and collaboration with the ATN team at RMIT led to Concept 5.6.4.2, which reached a CdA of 0.171 by raising the floor height from 230mm to 300mm This design incorporated two-seat tubs that dropped to the original height, reducing frontal area and improving drag coefficient However, further reductions in CdA required significant geometric changes, prompting a reduction in vehicle body width from 1800mm to 1700mm for Concept 5.7 Unfortunately, reverting to a smooth floor surface resulted in an increased CdA of 0.206 These iterations and changes were meticulously documented, highlighting key areas for improvement based on CFD results.
In October 2018, it was determined that the tunnels alongside the car's body needed significant softening to reduce airflow disruption Concerns also arose regarding the car's nose, front bar, and wheel spat shapes Collaborating with engineering teams from RMIT and Uni SA, the car's body was remodeled to enhance aerodynamics by flattening the side tunnels for smoother underbody transitions, rounding the front nose, and maintaining a smooth floor without seat tubs The rear wheel spats were redesigned with sharp edges to minimize drag, and a belt line was introduced for effective manufacturing in two parts The remodelling process prioritized high-resolution surface modeling, achieving A-class surfacing to ensure neat tangency and prevent imperfections that could complicate the final part's finishing.
Despite the recent changes, the CdA of concept 5.8 (Fig 46) was still lower than the previous best model at 0.175, which was disappointing Additionally, the time for further design iterations was limited as the deadlines for FEA and manufacturing approached.
As the design deadline approached, determination to achieve the established goals led to the development of Concept 5.8.2, which achieved a simulated drag coefficient of 0.104 and a frontal area of 1.54 m², resulting in a CdA of 0.16 (Fig 48).
To achieve our goal, we reverted to a previous floor geometry iteration, raising the floor and reintroducing seat tubs, which significantly reduced drag The optimal aerodynamic result, Concept 5.6.4.2, featured this floor design with a drag coefficient (Cd) of 0.103 Subsequently, our final design, known as Concept 6, underwent refinements during a team integration week with UTS and Uni SA members, hosted by RMIT in late November 2018, to expedite the integration of all vehicle components and the FEA analysis.
Figure 487: Concept 5.8 CFD (Photo Credit Steve Ilic & Marko Radmanovic)
Figure 498: Concept 5.8.2 CFD (Photo Credit Steve Ilic & Marko Radmanovic)
After assessing the CFD, a 1/5 scale model of concept 6 was 3D printed and tested in the wind tunnel at RMIT alongside Team Arrow’s 2017 car model Despite differences in simulated conditions, such as the absence of a moving ground and variations in temperature and surface finish, the comparison yielded valuable insights The wind tunnel results indicated a CdA of 0.17 for concept 6, which is comparable to Team Arrow’s car that secured 3rd place in 2017 and is set to compete again in the 2019 BWSC event This outcome is particularly promising, given that our car aims to be nearly 100kg lighter than Team Arrow's vehicle.
Figure 5051: ATN & Team Arrow Solar car ⅕ Scale Models in the wind tunnel
The body structure of a car is crucial for occupant safety, vehicle stability, and strength, necessitating careful design adjustments to accommodate structural requirements For instance, door shapes must ensure that the body remains strong enough to prevent buckling when open, as distortion can hinder proper closure Balancing structural integrity with minimal vehicle weight is essential, leading to compromises in body design, particularly in areas like the rear During the design process, aerodynamics was prioritized, resulting in multiple iterations to achieve a slim tail and a sharp shoulder radius to reduce wind turbulence and drag However, these tight radii posed challenges in the Finite Element Analysis (FEA) due to material thickness constraints, requiring several adjustments to establish an appropriate minimum radius across the body surface.
After refining the body shape, the integration process began, focusing on essential exterior details such as headlight design and positioning, tail bulkhead, tail light placement, and wheel doors Additionally, the design of the door shape, windscreen, and side windows depended on the interior validation process.
The headlight is compatible with a standard headlamp unit featuring both low and high beam functions Additionally, the design incorporates 3mm x 3mm LEDs for the parking lights and indicators.