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In the course of its history, BMW has
repeatedly provided impulses for the further development of personal
mobility through innovative vehicle and drive concepts. Last year's
special exhibition ‘Concept Vehicles' at the BMW Museum presented a
selection of these unusual concepts. Now two more vehicles from the
recent past are about to be added to the exhibition. Known as SIMPLE and
CLEVER, this brace of concepts goes on show at the Museum on 9th
October, bearing eloquent witness to BMW's innovative strength.
SIMPLE - light in weight, low
on energy
Simple combines features and advantages
from both automobiles and motorcycles. The concept owes its passenger
cell to the car, providing protection from wind and weather as well as
shielding the driver from exterior noise and offering occupants a high
degree of safety in the event of an accident. The motorcycle inspired
the slim design of the Simple (at just 110 centimetres wide) and its
configuration for two people sitting one behind the other. Plus it
boasts the dynamic driving style typical of a two-wheeler, allowing you
to lean right into corners as desired. The designation "simple" is an
acronym of the project name "A sustainable and innovative mobility
product for low energy consumption".
The BMW designers initially planned a
small vehicle with low weight and minimal aerodynamic drag properties.
Following a concept phase of several months, the pooled requirements and
ideas gave rise in 2005 to a vehicle based on tilting technology. In
contrast to other vehicle concepts in which only the passenger cell
tilts during cornering, here all the driver has to do is determine a
change in direction for the appropriate tilt to follow automatically.
The stand-out feature of the Simple concept is that it activates the
hydraulics only in exceptional situations, for example if the vehicle
threatens to become unstable during extremely slow driving, when
righting the vehicle during standstill or in extreme situations such as
drifting. Otherwise, Simple rides like a motorcycle and, beyond natural
gravity and gyroscopic forces, requires no energy whatsoever to lean
into a corner. The passenger also benefits from this tilting technology
as he feels no transverse forces and, particularly during rapid changes
of direction, need not compensate for any lateral movements.
All that is needed to power this
lightweight vehicle with a kerb weight of approx. 450 kg is a 36 kW
combustion engine. Acceleration from 0 to 100 km/h is estimated at under
ten seconds and the vehicle has an excellent drag coefficient of 0.18.
Using the electric motor and the combustion engine, the Simple would
need just 6 kWh (equivalent to 0.7 litres of petrol) or two litres over
100 km.
CLEVER - cooperative driving
pleasure
CLEVER is the acronym for "Compact Low
Emission Vehicle for Urban Transport" and refers to a research project
aimed at producing a low-emission, practical city vehicle. The CLEVER
project was launched in 2002 as an initiative of Berlin's Technical
University, sponsored by the 5th Framework Programme of the EU
Commission. Further research partners were the University of Bath,
England, the Institut Français du Pétrole and the University of Natural
Resources and Applied Life Sciences, Vienna. Involvement on the industry
side came from Cooper-Avon Tyres Ltd., the ARC Light Metal Competence
Centre Ranshofen GmbH, TAKATA-PETRI AG and WEH GmbH. The BMW Group took
over the technological management and the construction of the chassis,
interior and exterior. The design and the prototypes likewise came under
the aegis of the BMW Group.
Being CLEVER means sitting one behind
the other in a three-wheeled vehicle driven by a low-emission natural
gas engine. And that adds up to low aerodynamic drag, minimal weight and
a small road footprint: the research vehicle is around 3 metres long, 1
metre wide and 1.4 metres tall, weighs in at under 400 kilograms and
offers no more than a square metre of frontal area to the airstream. But
being CLEVER also means enjoying the riding fun of a motorcycle coupled
with the safety of a passenger car. To this end, the driver and
passenger sit in a crash-optimised aluminium space frame with
computer-controlled tilting during cornering, offering occupants a
typical two-wheeler ride experience.
Focusing on the essentials of motorised
travel in city traffic thus paved the way for new technologies and
innovative solutions. The tilting technology, in particular, was then a
novelty in this form: the single-cylinder engine along with the seamless
CVT transmission are mounted in a subframe to which both rear wheels -
controlled by swing arms - are attached. The connection to the front
main frame is by a central pin with two hydraulic actuators. Depending
on the driving situation, these ensure that the driver and passenger
lean into corners by up to 45 degrees. It makes for driving that is free
of transverse forces and, for the first time, is entirely
computer-controlled.
The research engineers came up with a
similarly unusual solution for the front steering, which is controlled
by an H-shaped swing arm. To save space and weight on the one hand,
while on the other creating a secure connection to absorb energy in a
frontal collision, they developed a new kind of wheel hub steering. The
pivot pin around which the wheel turns during steering is located inside
the wheel hub, allowing the front axle to be attached to the swing arm
flanges on both sides. When the driver turns the steering wheel - which,
incidentally, comes from the BMW Z4 - a steering transmission with lever
arm control transmits the steering commands. This not only prompts the
wheel to turn but, depending on speed, also tilts the entire passenger
cell into the corner.
A paramount aim of the CLEVER was to
use a drive system with minimal emissions. The stipulation of low CO2
emissions in the region of 60 grams per 100 kilometres was thus part of
the brief from the start. The researchers opted for a fully developed
single-cylinder engine with 230 cc displacement and output of 12.5 kW,
powered by natural gas from two compressed-gas cylinders. The research
vehicle accelerates from standstill to 60 km/h in around 7 seconds,
going on to a top speed of approx. 100 km/h. The two gas cylinders each
contain 1.7 kilograms of CNG (Compressed Natural Gas) to provide a range
of about 200 kilometres. That means it costs two people 1 euro to travel
around 100 kilometres. The cylinders are also designed to be easily
refilled at gas filling stations as well as at home.
On a par with eco-friendliness and
energy efficiency, a high level of passive safety was among the
principal requirements in the brief. As in a Formula One racing car, the
main frame - weighing just over 60 kg - constitutes the survival cell,
while the front wheel and steering ensure a deformation path of some 35
centimetres to absorb sufficient energy in an impact. Thanks to special
seat belts and a specially developed driver airbag, the research vehicle
complied with the Euro NCAP crash test requirements for small cars at
the time: even in a frontal collision at 56 km/h, the three-wheeled
prototype offered a secure survival cell.
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