DNV Fuel Fighter is a student organization at NTNU, competing in "Shell Eco Marathon", a yearly international event where students compete to produce the most energy efficient car. DNV Fuel Fighter first participated in 2008, winning multiple awards over the years.
Our team consisted of nine students from Industrial Design working on the exterior and interior of the next car, along with two student from Machine Engineering, one working with CFD analysis of aerodynamics, one with FEM analysis of the carbon fiber monocoque structure.
As the team leader I have coordinated the design process within the group, and our cooperation with the rest of the organisation. I have also worked actively on the exterior, leading worksessions and keeping track of the progress.
DNV Fuel Fighter is competing in the "Urban Concept Battery Electric" class, where the car has to comply with numerous rules for dimensions, lights, etc., and the race is simulating "city driving". The main objective is energy usage, but there are multiple off-track awards as well, including Design, Communication, and a separate Autonomous competition.
INSPIRATION
Our goal was to design a car that was competitive in terms of energy usage, while taking the conceptual challenge seriously. A concept car should inspire, and explore what a car might be.
Most electric cars nowadays are based on the traditional petrol car aesthetics (a heavy engine in front, with a passenger carrege behind), with "sci-fi" detailing to signal some technological progress. The fact that most electrical cars still sport some fake "grill" is quite telling.
We wanted to use the mechanics of electric energy as the starting point for our concept, and design the exterior to signal lightness and energy efficiency. These are classic aesthetic themes, explored in many historical and contemporary concept cars, but not that apparent in the current world of electric production cars.
EARLY SKETCHES
We started sketching out ideas for how we might utilise these properties, defining the concept along the way. One early decision was to push the cockpit forward, a simple way to reduce aerodynamic drag, and an exploration of how a vehicle without a traditional engine might look.
CLAY MODELLING
After agreeing on the general concept we started experimenting with clay models, discussing our ideas and testing them in 3D. The early development culminated in a 1:10 clay model, built around a 3D printed wheelbase, roughly adjusted for the Shell rules.
The design is based around the forward leaning cockpit, and a slim casing around each of the four wheels, connected by a central plane. The lines and overall volumes are based on "tear-drop" shapes, the optimal geometry for reducing drag. The elevated plane and the soft curves around the cockpit emphasises the negative volume underneath the monocoque and the flow of air around the driver.
The combination of organic volumes and clearly defined lines suits the idea of a technically engineered vehicle flowing through the air.
With the help of 3D scanning and VR visualisation, we developed the monocoque with "T-spline"-modelling in Fusion 360. For the last 5 months we continuously developed new iterations, testing and discussing ideas underway.
While defining the monocoque, we used some quite different methods of testing and optimising the shape. For aerodynamics, we used SolidWorks to get an overview of the airflow, OpenFoam to run the precise simulations, and we built a mockup windtunnel to test our 3D printed models. For strength, we ran simulations of relevant loads on the carbon fiber structure, to make sure our design was viable, and to know where we could save weight and surface area. We also built a physical mockup of the cockpit together with the interior team, to make sure our dimensions made sense, and to find out where we might save frontal area.
During the development we had to make multiple compromises, usually involving some balance between aesthetics and performance. Important considerations has been the length of the vehicle and dimensions of the wheelbase. The many rules set by Shell have also been important. For example, we have turned the "minimum shoulder width" into a design feature, and finely tuned the overall curves to make the best out of the strange proportions.
From here, we handed the project over to the next Fuel Fighter team, which included some very skilled engineers and mechanics. Despite COVID-19, a tight schedule, and a very limited workshop, they would manage to get the car together in time for the 2022 competition. The team experimented with plant fibers for parts of the exterior, as a sustainable replacement for carbon fiber. Apart from that, the car very much sticks to the initial design.
