Lightweight Electric/Hybrid Vehicle Design

Introduction xv
offsets the very high calorific value packed by a litre of petrol. An electric car has potential for
very low cost per mile operation based on electrical recharge costs for the energy-storage batteries,
and EVs are quite competitive even when the cost of battery replacement is included after the
duration of charge/recharge cycles has been reached. It needs to be made apparent to the public
that a change in batteries is akin to changing the cartridge in a photocopier–essentially the motiveforce
package is renewed while the remainder of the car platform (machine) has the much longer
life associated with electric-driven than does the petrol-driven vehicle. In this sense batteries are
amortizable capital items, to be related with the much longer replacement period for the vehicle
platform which could well carry different style bodies during its overall lifetime.
The oversizing of petrol engines in conventional cars, referred to above, arises from several
factors. Typical car masses, relative to the masses of the drivers they carry, mean that less than 2%
of fuel energy is used in hauling the driver. Added to the specifying of engines that allow cars to
travel at very large margins above the maximum speed limit is of course the conventional
construction techniques and materials which make cars comparatively heavy. The weight itself
grossly affects accelerative performance and gradient ability. Also some estimates consider six
units of fuel are needed to deliver one unit of energy to the wheels: one-third wheel power being
lost in acceleration (and heat in consequent braking), one-third in heating disturbed air as the
vehicle pushes through the atmosphere and one-third in heating the tyre and road at the traction,
braking and steering contact patch. This puts priorities on design for electric vehicles to cut tare
weight, reduce aerodynamic drag and reduce tyre rolling resistance.
0.2.3 QUESTIONING THE INDUSTRY-STANDARD APPROACH
The design process in the main-line automotive industry is driven by the edicts of the car-makers’
styling departments who ultimately draw their inspiration from the advertising gurus of Madison
Avenue, whose influence has, of course, spread worldwide. The global motor industry has been
predominately US dominated since Henry Ford’s pioneering of systematic volume production
and General Motors’ remarkable ability to appeal to widely different market sectors with quite
modestly varied versions of a standard basic vehicle. Thus far the electric, or hybrid drive, vehicle
had to conform to historically developed design norms with the cautious conservatism of marketing
management defining the basic scantlings. Conventional automotive design must conform to the
requirements of Mr and Mrs Average, analysed by countless focus groups, while meeting the
necessities of mass-production equipment developed during the first century of the motor vehicle.
When bold attempts have been made to achieve substantial reductions in weight below that of
the standard industry product, the limitations of these major constraints have usually moderated
the design objectives, Fig. 0.1. The overruling necessity to ‘move metal’ at the scale of ten million
vehicles per year from each of the world’s three main areas of motor manufacture makes radical
design initiatives a scary business for ‘corporate bosses’. Advertising professionals, with their
colleagues in public relations, have skilfully built up customer expectations for the conventional
automobile, from which it is difficult for the designer to digress in the interests of structural
efficiency and light weight. Expectations are all about spacious interiors with deep soft seats and
wide easy-access door openings; exterior shape is about pleasing fantasies of aggressiveness,
speed and ‘luxury’ appearance. Performance expectations relate to accelerative ability rather than
fuel economy, as Mr Average Company Representative strains to be ‘first off the grid’.
Ecologists who seek the palliative effects of electric propulsion will need to face up to educating
a market that will appreciate the technology as well as convincing motor industry management of
the need for radical designs which will enable the best performance to be obtained from this
propulsion technology. The massive sensitivity of the general public to unconventional vehicle