Dynamic driving pleasure on three wheels
- Cornering dynamics of a motorcycle, safety of a passenger car
- Body and front wheels tilt when negotiating bends
Three wheels, two seats and a jet-design body – these are the visual characteristics of a research vehicle with which DaimlerChrysler surprised the public at the Frankfurt Motor Show in autumn 1997. The F 300 Life-Jet is aimed at a market segment which does not even exist yet, namely the niche between passenger cars and motorcycles. A new species of vehicle could establish itself here which combines everything the modern motorist requires for the perfect driving experience: the fresh-air fun of a convertible, the individuality of a roadster, the performance of a sports car, the comfort of a compact car and – not least – the safety of a Mercedes-Benz.
The F 300 Life-Jet offers all these attributes, and combines them with a further special feature which car drivers have previously lacked: the driving experience and cornering dynamics of a motorcycle. Accordingly this research vehicle reconciles seemingly contradictory characteristics: it is as safe and comfortable as a four-wheeled vehicle but as dynamic as a two-wheeler.
Active Tilt Control (ATC) lies at the heart of the F 300 technology. This system is based on the lightning-fast interaction between electronics, hydraulics and mechanics: sensors register the current driving situation and continuously feed the onboard computer with data indicating the yawing and linear speed of the vehicle, the acceleration, the current steering angle and the position of the hydraulic cylinder which steers the front axle. On the basis of this information the computer calculates the necessary angle of body tilt and sends the relevant control signals to the hydraulic system. As a result, the F 300 Life-Jet adopts a precisely calculated angle of tilt when negotiating bends, which reflects the current driving situation and therefore offers the best possible resistance to overturning. At maximum speed, for example, the ATC computer allows only a very small amount of body roll and provides additional stability, but quickly allows the active control system to select a maximum angle of tilt of 30 degrees at non-motorway road speeds.
Cornering speed of a motorcycle
By means of this active tilt on bends, the F 300 developers are able to compensate a large proportion of the lateral forces which act on the vehicle and affect its resistance to overturning. The centre of gravity is shifted to the inside of the bend, substantially compensating the tendency to overturn and making high cornering speeds possible. The maximum lateral acceleration of the F 300 Life-Jet is 0.9 g – a level normally only reached by experienced motorcyclists. The loads acting on the occupants remain low, however. Owing to the tilting effect on bends, they only need to resist the centrifugal forces to a very small extent – an advantage that decisively improves ride comfort.
The engine and transmission of the three-wheeled study are in a space-saving position between the interior and the rear wheel. The 1.6-litre power unit adopted from the A-Class has an output of 75 kW/102 hp and accelerates the F 300 Life-Jet from standstill to 100 km/h (62 mph) in just 7.7 seconds. The maximum speed is 211 km/h (131 mph). This innovative three-wheeler therefore achieves the performance levels of much more powerful sports cars and roadsters.
Aluminium chassis with removable roof sections
The chassis of the two-seater is made from aluminium and weighs only 89 kilograms. Special features of the body include an upward pivoting door on the driver’s side, a rearward pivoting door on the passenger side and a fixed roof of aluminium and transparent plastic which makes the F 300 Life-Jet a genuine all-season vehicle. The two roof sections can be easily removed and stowed in a compartment above the rear wheel, converting the three-wheeled study into an open-top roadster.
An innovative headlamp with three reflector areas and two bulbs provides maximum road illumination when negotiating bends. The headlamp electronics are linked to the ATC computer, pivoting the headlamp according to the body tilt and switching on a special cornering light when required. This increases the area illuminated by the dipped headlamp beam by more than 80 percent.
New, space-saving neon lighting technology is used for the indicators, brake lights and side lights of the research vehicle. The driving lights are switched on automatically by a sensor when darkness falls or the vehicle enters a tunnel. Mercedes passenger cars have been equipped with this system since 1998.
Bright, welcoming, jet-style interior
Inside, the F 300 lives up to its name Life-Jet, with a cockpit which might almost have come straight out of an aircraft. The jet-style steering wheel, instruments, shift lever and seats create an impression of sitting in an aircraft cockpit. The large windows, sharply rearward sloping A-pillars and transparent roof reinforce this impression, while the attractive colour scheme ensures a bright and welcoming ambiance.
But that’s where the resemblance ends. The front wheels are prominent in the driver’s field of vision, and ground contact is ensured at all times even if the steering wheel does look rather like a joystick. Far from allowing the driver to ‘take off’, this ingenious ‘segmented’ steering wheel, in conjunction with the active tilt control, ensures the driver stays firmly on the road, even when cornering at high speed. The rack-and-pinion steering is geared so that only 2.3 turns of the wheel are required to turn the front wheels from lock to lock, making for easier parking and manoeuvring.
Controls in the segmented steering wheel
The segmented steering wheel is also a control centre. Tucked into the sides of its padded boss are the radio and telephone buttons – the driver can select a station or control the volume without taking his hand off the wheel. The radio and cassette player are concealed under a flap in the nearside side trim and the phone is mounted on a bracket on the instrument panel. On two displays underneath the windscreen the driver can see what station has been tuned in or what telephone number has been dialled. Time and temperature readings are also displayed.
Forming the centrepiece of the F 300 cockpit are three easily readable circular instruments showing engine speed, road speed, coolant temperature, fuel level and engaged gear. A thin layer of electroluminescent foil on the back of the instruments gives an agreeable and even illumination of the instruments. On the left hand side of the cockpit is the new light sensor which automatically switches on the dipped beam at nightfall or when entering a tunnel. Close to this is the conventional manual light switch.
Underneath the instrument cluster are the usual cockpit lights for oil level, voltage, hand brake and high beam. To the right is a useful detail inspired by motorcycle design – a starter switch. After the ignition has been switched on, this switch can be pressed to start the engine without turning the ignition key.
Hydraulic transmission functions
Speed and convenience are keynotes of the manual transmission too. The five gears are selected, after depressing the clutch, by moving the shiftlever, situated on the right-hand side of the cockpit, slightly forwards or backwards. Conventional shift linkage has been dispensed with in favour of electronics. The slight pressure on the lever is translated by the electronic transmission control system into electric signals, activates a hydraulic system and automatically engages the gears. At the same time the display in the instrument cluster changes, informing the driver that the command has been carried out.
This “sequential gear selection” system results in fast, efficient gear-changing – which is exactly the right note for a dynamic vehicle like the F 300 Life-Jet.