6th June 2012
This isn’t the first time we’ve written about car manufacturers trying their hand at designing a bike. Lamborghini recently revealed its partnership with BMC while Porsche showed off their carbon fiber framed bike in Shanghai and McLaren promoted its Venge model. Now it’s Audi’s turn as they reveal the Wörthersee e-bike, a carbon fiber, electric drive bicycle.
Like many high performance bikes, the Wörthersee makes use of carbon fiber throughout its structure to keep weight as low as possible but without compromising on strength. While most composite framed bikes are primarily road bikes, Audi’s entry into the market can be used for off-road riding and even performing tricks. This produces some interesting engineering challenges as the forces on the carbon fiber frame becomes more unpredictable as the rider performs wheelies or lands from jumps.
The complete bike excluding electrical components weighs in at 11 kg (24.25 lb), equivalent to a power-to-weight ratio of 9 kg (19.84 lb) per kilowatt, or 7 kg (15.43 lb) per horsepower – a record-breaking value.
“When developing the Audi e-bike Wörthersee we drew on motor racing design principles for inspiration,” explains Hendrik Schaefers, one of the designers at Concept Design Studio Munich. “The e-bike appears incredibly precise, highly emotional and strictly functional. Indeed, the design effort focused on its function as a sports machine. All design elements are thus firmly aligned to the technical features.”
The frame features a low center of gravity and a compact overall volume. The lithium-ion battery is incorporated into the frame and requires 2.5 hours to fully charge. The frame and the swinging arm that holds the back wheel are made of carbon fiber composites. The same material is used for the 26-inch wheels, which feature an “Audi ultra blade” design with broad flat spokes for an optimized transmission of pedal power.
“We were able to demonstrate with the choice of materials just how closely design goes hand in hand with expertise in ultra lightweight construction,” Hendrik Schaefers comments.
Homogeneous LED light strips round out the frame and create the immediately recognizable Audi light signature. For tricks and stunts, the seat can be lowered to run flush with the frame itself. At the press of a button, the seat then rises up and the biker can adopt a comfortable position.
Cycling modes and other functions can be set using the touchscreen on-bike computer. The cyclist’s smartphone hooks up by WLAN to the computer – when the rider starts cycling, for example, the immobilizer is deactivated. Video images of the trial drive or of a trick, as recorded via the in-helmet camera, are uploaded to the Internet in real time via smartphone. Each trick performed successfully is then awarded success points, and as the number of points awarded grows, the cyclist receives awards and the challenge level rises, too. The rankings table in the Internet means the rider can measure himself/herself against other bikers.
The cyclist can choose between a total of five cycling modes – pure muscle power, the electric motor alone, or pedaling supported by the electric motor. In the “Pure” mode, the drive power is purely the product of the cyclist’s legs, while in “Pedelec” mode the cyclist is supported by the electric motor that then makes speeds of up to 80 km/h (50 mph) possible and provides a range of 50 to 70 kilometers (31 to 44 miles).
In “eGrip” mode, the Audi e-bike Wörthersee runs solely on the electric motor and can reach a top speed of 50 km/h (31 mph). The cyclist then controls forward momentum using a gripshift and can configure the power as desired using the computer.
When performing wheelies, an electronic control system support the rider when performing tricks and back-wheel biking. Different modes can be set using a smartphone or directly on the e-bike – either “Power Wheelie” mode, with adjustable wheelie angle for less skilled bikers or “Balanced Wheelie” mode for sporting challenges. In “Balanced Wheelie” mode, the electronic control system maintains the rider’s balance, by compensating the biker’s movements forwards or backwards via the electric motor in a similar way to a Segway.
The electric motor is located at the lowest point on the frame and drives the bottom bracket shaft directly. The maximum torque delivered to the rear wheel is 250 Nm (184.39 lb-ft). The electric motor generates a maximum output of 2.3 kW, a new world best for e-bikes.
Learn more about the Audi e-bike