Finally together with the knowledge and expertise provided by Apollo, a new internal structure was realised as well as a specially designed tread compound for the tyres on the 2014 car. The final outcome was a slick tyre which was extremely quick, but prone to excessive tyre wear. Also, they had a rain tyre which outclassed the competition by some margin.
The chassis for its 2015 racer is a single-piece CFRP monocoque with honeycomb core. This achieved the team’s lightness and strength goals. The whole car without its driver only weights 160 kg. When looking at the bulkhead of the 2015 car, it reveals the exposed honeycomb core, while a look at the front suspension shows the wishbone layout and outboard Ohlin’s dampers as well as the aluminium bracket for the brake reservoir.
For its propulsion, the cars use four AMK DT5-14 electric motors, which have been cleverly designed to sit inside the wheel hub. The maximum power output is four times 32.5kW at 11000rpm / (4 x 28Nm at 0rpm). The power is put through a student developed, four one-stage planetary gearboxes which are put onto the road by a self-developed slip ratio and yaw-rate controller differential. The front and rear suspension sees double anti-parallel unequal length CFRP A-arms. The layout consists of front pull rod, rear push rod, actuated vertically oriented springs and dampers.
One design concept which has carried over from the 2014 car, is its unique wheel layout with external brake discs. On the 2015 car, the concept integrates part of the brake calliper with the upright, reducing weight even further. On the inner face of all four wheels sit the hub motors for geometry and balance gain.
This year, a new design of accumulator provides the energy to all four electric motors, which can store 7.2 kWh of electrical energy. This is an increase of 12% over the car they ran last year.
The simulation showed that the increase of energy capacity is more favourable, although the weight increases substantially. The result is that the car can have a higher average velocity during the endurance. Though during the endurance at Silverstone, the Delft drivers had to drive at a reduced speed in order to last the distance, something the team’s main rivals ETH Zurich failed to master.