|Audi e-bike Wörthersee. Click to enlarge.|
One of the highlights on the Audi stand at the 2012 Wörthersee Tour in Austria (an annual gathering of Audi VW, Seat and Skoda enthusiasts) is an electric bicycle technology concept: the Audi e-bike Wörthersee.
The prototype cycle—described by Audi as a high-end pedelec made for sport, fun and tricks—combines an electric drive and muscle power. The permanent magnet synchronous electric motor is located at the lowest point on the frame and drives the bottom bracket shaft directly; the rear wheel is driven by a chain. Maximum torque delivered to the rear wheel is 250 N·m (184 lb-ft). The electric motor generates a maximum output of 2.3 kW, a new world best for e-bikes.
The lithium-ion battery is housed in the frame; it weighs about 5 kg (11.02 lb) and operates at a voltage of 48 V. Its capacity is 530 Wh and it can be fully recharged from a 230 V supply in two and a half hours. As an alternative it can be easily detached from the bike and replaced by a recharged battery.
The nine-speed hydraulically actuated gear shift has a very rapid sequential action, similar to the R tronic transmission in an Audi R8, Audi notes. The two disk brakes are also applied hydraulically. Seat height can be continuously adjusted at a handlebar control, even while the bike is being ridden. The front fork uses the more complex ‘upside-down’ principle; it is air-sprung, with 130 mm (5.12 in) of travel. LEDs are used for powerful lighting: the front light is integrated into the handlebar, the rear light into the seat.
The frame features a low center of gravity and a compact overall volume. The frame and the swinging arm that holds the back wheel are made of carbon fiber-reinforced polymer (CFRP). The same material is used for the 26” wheels, which feature an innovative “Audi ultra blade” design with broad flat spokes for an optimized transmission of pedal power. The wheels weigh only 600 grams (1.32 lb) each. The entire CRFP frame weighs only 1,600 grams (3.53 lb). Material reinforcements are used only at the points where loads actually occur.
The complete bike, excluding electrical components weighs, in at 11 kg (24.25 lb), equivalent to a power-to-weight ratio of 9 kg (20 lb) per kilowatt, or 7 kg (15 lb) per horsepower.
The on-board computer is located in the frame top tube and operated using a touchscreen. Among the functions it provides are riding mode selection, recording trick sequences and adjustment of various e-bike functions such as electric pedaling assistance and lighting. The display shows road speed, distance covered, state of battery charge, energy consumption and slope angle at any given moment.
Cycling modes and other functions can be set using the touchscreen on-bike computer:
In the “Pure” mode, the drive power is purely the product of the cyclist’s legs.
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 delivers a range of 50-70 kilometers (31-44 miles).
Under “eGrip”, 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. “Power Wheelie” mode offers an adjustable wheelie angle for less skilled bikers; “Balanced Wheelie” mode is set 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.
This means the rider can influence the bike’s speed by shifting weight: lean forwards accelerates the bike, lean backwards slows it. “Training” mode keeps performance constant for training purposes.
The rider’s smartphone communicates by WLAN with the bike’s computer. The antenna is integrated into the front brake line. To ride the bike, the immobilizer is deactivated at the smartphone; the bike is then ready for use. In addition, by way of the interface between the bike’s computer and the smartphone, video images recorded while riding or even complete trick sequences can be transmitted to the Internet or the trainer. Every trick performed successfully qualifies for success points. As the number of points increases, the rider is rewarded and at the same time the challenge level rises. The total Internet ranking can be compared with friends or other riders. The rider can locate them by way of Facebook entries that can be shown on the Audi e-bike Wörthersee’s display.