8WD Electric limousine handles like a sportscar
By Mike Hanlon
September 14, 2004
The KAZ (Keio Advanced Zero-Emission Vehicle) is a Japanese-designed Italian-built limousine prototype with eight wheels. The KAZ is not your average limo though. The all-electric KAZ can travel at 300kph and it handles more like a sports car than a 6.7m-long whale thanks to its computer-controlled eight-wheel drive train and low centre of gravity for added stability and handling around curves.
On top of that, four-wheel steering in front is augmented by the two extreme wheels angling in the opposite direction making the KAZ more nimble around corners than one would expect for a vehicle of its size.
But are the eight wheels really necessary? Actually they give the KAZ far superior balance to regular four-wheel vehicles.
The eight wheels make pickup virtually flat as "tail squat" when accelerating from standstill, and "nose diving" when braking is eliminated. While making for smoother driving, it also reduces energy loss.
KAZ makes use of three very innovative component technologies. Firstly, rows of 3.75V Lithium-Ion batteries are the most important components in order to supply high energy and power to the eight individual motors powering the KAZ.
That is, an electric motor with a 55kW (73hp) maximum output connected directly to each wheel.
This gives KAZ a total power output of 440kW (590hp).
An Intelligent Power Module was useful to make inverters with low energy loss and of a compact size. Lastly, the motors were realised with Nd-Fe Rare Earth magnets which are highly efficient and compact, yet still able to produce high torque and high speed.
The preconception that electric cars cannot travel at high speeds over long distances has been completely smashed by this prototype.
In speed tests in Italy in 2001, KAZ achieved a speed of 311kph, the current world record for an electric car. It also has a range of 300km on one charge at a constant 60kph with a range extender in development that will give KAZ a range of 600km.
Expected to carry up to eight people from 0-400m in 14.5secs, once the KAZ gets going at top speeds, one advantage it has over its fuel driven compatriots is that it is very quiet. Peaceful engine hums, zero emissions and low vibration make for a smooth ride.
By starting the vehicle from the ground up, designers of KAZ did away with the tradional combustion motor and transmission system, and opted for a reduction gear system, mechanical brake, and wheel bearing all housed around each driving wheel.
This amazing concept decreases transmission loss between a motor and a wheel, reduces the overall weight of the vehicle and increases the available cabin space, since there are no gears and axles cluttering underneath the main part of the cabin.
All design features combined make the KAZ about 1.7 times more energy efficient than a conventional car.
Designer Hiroshi Shimuzu, a Professor of Environmental Information at Tokyo's Keio University, began developing electric vehicles in 1978. KAZ is not his first attempt, as it has evolved from six earlier projects, most notably the the remarkable Luciole EV, a tandem, two-seat electric car, first introduced at EVS 17 in Orlando, Florida in 1997.
The body design and construction of the KAZ have been handled by Italy's I.D.E.A. Institute, with participation from thirteen domestic Japanese companies.