02 Design theory and practice

For the automotive engineer with background experience of IC-engine prime-moving power sources, the electrical aspects associated with engine ignition, starting and powering auxiliary lighting and occupant comfort/convenience devices have often been the province of resident electrical engineering specialists within the automotive design office. With the electric vehicle (EV), usually associated with an energy source that is portable and electrochemical in nature, and tractive effort only supplied by prime-moving electric motor, the historic distinctions between mechanical and electrical engineering become blurred. One day the division of engineering into professional institutions and academic faculties defined by these distinctions will no doubt also be questioned. Older generation auto-engineers have much to gain from an understanding of electrotechnology and a revision of conventional attitudes towards automotive systems such as transmission, braking and steering which are moving towards electromagnetic power and electronic control, like the prime-moving power unit.

In terms of reducing vehicle weight, to gain greatest benefit in terms of range from electromotive power, there also needs to be some rethinking of traditional approaches. The conventional design approach of automotive engineers seems to involve an instinctive prioritizing of minimizing production costs, which will have been instilled into them over generations of Fordist mass-production. There is something in this 'value-engineering' approach which might sacrifice light weight in the interests of simplicity of assembly, or the paring down of piece price to the barest minimum. Aerospace designers perhaps have a different instinctive approach and think of lightweight and performance-efficiency first. Both automotive and aerospace design engineers now have the benefit of sophisticated finite-element structural analysis packages to help them trade off performance efficiency with minimum weight. In earlier times the automotive engineer probably relied on substantial 'factors of safety' in structural calculations, if indeed they were performed at all on body structures, which were invariably supported by stout chassis frames. This is not to mention the long development periods of track and road proving before vehicles reached the customer, which may have led engineers to be less conscious of the weight/performance trade-off in detail design. Individual parts could well be specified on the basis of subjective judgement, without the sobering discipline of the above trade-off analysis.

Not so, of course, for the early aeronautical design engineers whose prototypes either 'flew or fell out of the sky'. Aircraft structural designers effectively pioneered techniques of thin-walled structural analysis to try to predict as far as possible the structural performance of parts 'before they left the drawing board', and in so doing usually economized on any surplus mass. These structural analysis techniques gave early warning of buckling collapse and provided a means of idealization that allowed load paths to be traced. In the dramatic weight reduction programmes called for by the 'supercar' design requirements, to be discussed in Chapters 4 and 6, these attitudes to design could again have great value.

Design calculations, using techniques for tracing loads and determining deflections and stresses in structures, many of which derive from pioneering aeronautical structural techniques, are also recommended for giving design engineers a 'feel' for the structures at the concept stage. The design engineer can thus make crucial styling and packaging decisions without the risk of weakening the structure or causing undue weight gain. While familiar to civil and aeronautical engineering graduates these 'theory of structures' techniques are usually absent from courses in mechanical and electrical engineering, which may be confined to the 'mechanics of solids' in their structures teaching. For students undertaking design courses, or projects, within their engineering degree studies, these days the norm rather than the exception, the timing of the book's publication is within the useful period of intense decision making throughout the EV industry. It is thus valuable in focusing on the very broad range of other factors-economic, ergonomic, aesthetic and even political-which have to be examined alongside the engineering science ones, during the conceptual period of engineering design.


Since the electric vehicle has thus far, in marketing terms, been 'driven' by the state rather than the motoring public it behoves the stylist and product planner to shift the emphasis towards the consumer and show the potential owner the appeal of the vehicle. Some vehicle owners are also environmentalists, not because the two go together, but because car ownership is so wide that the non-driving 'idealist' is a rarity. The vast majority of people voting for local and national governments to enact antipollution regulation are vehicle owners and those who suffer urban traffic jams, either as pedestrians or motorists, and are swinging towards increased pollution control. The only publicized group who are against pollution control seem to be those industrialists who have tried to thwart the enactment of antipollution codes agreed at the international 1992 Earth Summit, fearful of their manufacturing costs rising and loss of international competitiveness. Several governments at the Summit agreed to hold 1990 levels of CO2 emissions by the year 2000 and so might still have to reduce emission of that gas by 35% to stabilize output if car numbers and traffic density increase as predicted.

Electric vehicles have appeal in urban situations where governments are prepared to help cover the cost premium over conventional vehicles. EVs have an appeal in traffic jams, even, as their motors need not run while the vehicles are stationary, the occupant enjoying less noise pollution, as well as the freedom from choking on exhaust fumes. There is lower noise too during vehicle cruising and acceleration, which is becoming increasingly desired by motorists, as confirmed by the considerable sums of money being invested by makers of conventional vehicles to raise 'refinement' levels. In the 1960s, despite the public appeals made by Ralph Nader and his supporters, car safety would not sell. As traffic densities and potential maximum speed levels have increased over the years, safety protection has come home to people in a way which the appalling accident statistics did not, and safety devices are now a key part of media advertising for cars. Traffic densities are also now high enough to make the problems of pollution strike home.

The price premium necessary for electric-drive vehicles is not an intrinsic one, merely the price one has to pay for goods of relatively low volume manufacture. However, the torque characteristics of electric motors potentially allow for less complex vehicles to be built, probably without change-speed gearboxes and possibly even without differential gearing, drive-shafting, clutch and finaldrive gears, pending the availability of cheaper materials with the appropriate electromagnetic properties. Complex ignition and fuel-injection systems disappear with the conventional IC engine, together with the balancing problems of converting reciprocating motion to rotary motion within the piston engine. The exhaust system, with its complex pollution controllers, also disappears along with the difficult mounting problems of a fire-hazardous petrol tank.

As well as offering potential low cost, as volumes build up, these absences also offer great aesthetic design freedom to stylists. Obviating the need for firewall bulkheads, and thick acoustic insulation, should also allow greater scope in the occupant space. The stylist thus has greater possibility to make interiors particularly attractive to potential buyers. The public has demonstrated its wish for wider choice of bodywork and the lightweight 'punt' type structure suggested in the final chapter gives the stylist almost as much freedom as had the traditional body-builders who constructed custom designs on the vehicle manufacturers' running chassis. The ability of the 'punt' structure, to hang its doors from the A- and C-posts without a centre pillar, provides considerable freedom of side access, and the ability to use seat rotation and possibly sliding to ease access promises a good sales point for a multi-stop urban vehicle. The resulting platform can also support a variety of body types, including open sports and sports utility, as no roof members need be involved in the overall structural integrity. Most important, though, is the freedom to mount almost any configuration of'non-structural' plastic bodywork for maximum stylistic effect. Almost the only constraint on aesthetic design is the need for a floor level flush with the tops of the side sills and removable panels for battery access.


Some industry economists have argued that local body-builders might reappear in the market, even for 'conventional' cars as OEMs increasingly become platform system builders supplied by systems houses making power-unit and running-gear assemblies. Where monocoque structures are involved it has even been suggested that the systems houses could supply direct to the local body-builder who would become the specialist vehicle builder for his local market. The final chapter suggests the use of an alternative tubular monocoque for the sector of the market increasingly attracted by 'wagon' bodies on MPVs and minibuses. Here the stylist can use colour and texture variety to break up the plane surfaces of the tube and emphasize the integral structural glass. Although the suggested tubular shell would have a regular cross-section along the length of the passenger compartment, the stylist could do much to offer interior layout alternatives, along with a host of options for the passenger occupants, and for the driver too if'hands-off' vehicle electronic guidance becomes the norm for certain stretches of motorway.

Somehow, too, the stylist and his marketing colleagues have to see that there is a realization among the public that only when a petrol engine runs at wide open-throttle at about 75% of its maximum rotational speed is it achieving its potential 25% efficiency, and this is of course only for relatively short durations in urban, or high density traffic, areas. It is suggested that a large engined car will average less that 3% efficiency over its life while a small engined car might reach 8%, one of the prices paid for using the IC engine as a variable speed and power source. This 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.


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

Fig. 0.1 Alcan's use of 5754 aluminium alloy substituted for steel in the Ford Taurus/Sable saved an impressive 318 kg. The client's constraint of minimal changes to the passenger compartment and use of existing production equipment must have constrained the possibilities for further weight reduction, however.

Fig. 0.1 Alcan's use of 5754 aluminium alloy substituted for steel in the Ford Taurus/Sable saved an impressive 318 kg. The client's constraint of minimal changes to the passenger compartment and use of existing production equipment must have constrained the possibilities for further weight reduction, however.

configurations was made abundantly clear from the reaction to the otherwise ingenious and low cost Sinclair C5 electric vehicle. While clearly launched as a motorized tricycle, with a price appropriate to that vehicle category, the C5 was nearly always referred to by its media critics as an 'electric car' when operationally it was more appropriate for use on reserved cycleways of which, of course, there are hardly enough in existence to create a market. While the Sunracer Challenge in Australia has shown the remarkable possibilities even for solar-batteried electric vehicles, it is doubtful whether the wider public appreciate the radical design of structure and running gear that make transcontinental journeys under solar power a reality, albeit an extremely expensive one for a single seater. Electric cars are perceived as 'coming to their own' in urban environments where high traffic densities reduce average speeds and short-distance average journeys are the norm. There is also long-term potential for battery-powered vehicles to derive additional 'long-distance' energy from the underground inductive power lines which might be built into the inside lanes of future motorways. It is not hard to envisage that telematics technology for vehicle guidance could be enhanced by such systems and make possible electronically spaced 'trains' of road vehicles operating over stretches of motorway between the major urban and/or rural recreational centres.


At the time of writing some customer-appealing production hybrid and electric drive vehicles have already come onto the market. The Toyota Prius hybrid-drive car, described in Chapter 6, is already proving to be well received in the Japanese market where imaginative government operational incentives are in place. A variety of conversions have been made to series production compact cars which allow short-range urban operation where adequate battery recharging infrastructure is available. However, GM surprised the world with the technically advanced prototype Impact medium-range electric car, but the market has reportedly not responded well to its production successor and generally speaking there is not yet an unreservedly positive response.

Like the existing market for passenger cars, that for electric-drive cars will also be segmented, in time, with niches for sedan, convertible, dual-purpose, sports, utility, limousine and 'specialist' vehicles. The early decades of development, at least, may also be noted for the participation of both high and low volume builders. The low volume specialist is usually the builder prepared to investigate radical solutions and in the, thus far, 'difficult' market for electric cars it would seem a likely sector for those EVs which are more than drive-system conversions of existing vehicles.

With the high volume builders, already under pressure from overcapacity, their main attention is likely to be focused on retaining markets for current design vehicles, without the 'distraction' of radical redesigns. The ambitious, imaginative and high technology specialist has thus much to gain from an informed innovative approach and could benefit from a reported longer-term trend when drive systems will be manufactured by huge global producers and vehicle manufacturing will tend towards a regional basis of skilled body shops catering for local markets.


The 'physical' design package for an electric vehicle will result from a much larger 'design package of affecting factors' which encompasses vehicle operational category, manufacturing systems/ techniques, marketing and distribution. Packages for industrial trucks and specialist delivery vehicles are already established but those for passenger-car variants much less so. It has been suggested that the first substantial sales of electric cars might well be to electricity generating companies in the public utilities sector, who would rent them to railway operators for end-use by rail travellers. Such people would purchase their hire with return travel tickets to destination stations at which EVs would be parked in forecourts for the use of travellers. Other potential customers might be city-centre car hire fleets, taxicab operators in fossil-fuel exhaust-free zones or local authorities setting up city-centre car pools.

One of the most imaginative EV applications is the lightweight mini-tram, Fig. 0.2, as exhibited at the Birmingham ElectriCity event in 1993. This is a vehicle that runs on low cost tracks which can be laid on an ordinary road surface without further foundation. The vehicle can travel up to 50 km/h and is a flywheel-assist hybrid machine having its batteries recharged via low voltage conductor rails positioned at intervals around the track. Each car weighs just over 3 tonnes unladen and can carry 14 seated and 11 standing passengers. A 5 km route, including rails, can be constructed, to include five trams, ten stops and four charge points, at a cost ofjust £1 million. It seems an ideal solution to the problem of congested cities that have roadways that date back to pre-automobile days, with the mini-trams able to transport both passengers and goods in potential 'pedestrian precincts' that would be spoilt by the operation of conventional omnibuses and tramcars. The proposal serves well to illustrate the opportunities for electric vehicles, given some imaginative lateral thinking.

Since launch, larger vehicles have been produced and entered service. The one seen at Bristol Docks (Fig. 0.2, right) has a steel frame with GRP body panels and weighs 13 tonnes, compared with the smallest railcar which weighs 48 tonnes. There are four production variants on offer, carrying 30, 35 or 50 passengers, and a twin-car variant of the latter. Use of continuously variable transmission now ensures the flywheels run at constant speed; a third rail at stations is used for taking in electricity for 'charging up' the flywheel. A 2-minute recharge would be required for the

flywheel to propel the vehicle its maximum distance of two miles; so more frequent stops are recommended to reduce recharge time, 0.5 km being the optimum. A hybrid version with additional LPG power was due for launch in Stourbridge, UK, as a railcar in early 2001.

Some of the above projects are all based on the proposition that the more conservative motor manufacturers may not follow the lead set by Toyota and Honda in offering hybrid-electric drive cars through conventional dealer networks. In the mid 1990s the US 'big-three' auto-makers were crying that there was little sales interest from their traditional customers for electric cars, after the disappointing performance of early low volume contenders from specialist builders. The major motor corporations are considered to operate on slender profit-margins after the dealers have taken their cut, but a change to supermarket selling might weaken the imperative from high volume products which could favour specialist EVs from the OEM's SVO departments. That the corporations have also jibbed violently against California's mandate for a fixed percentage of overall sales being EVs, and wanted to respond to market-led rather than government-led forces, suggests a present resistance to EVs.

A number of industrial players outside the conventional automotive industry are drawing comparisons between the computer industry and the possible future electric vehicle industry, saying that the high-tech nature of the product, and the rapid development of the technologies associated with it, might require the collaboration of companies in a variety of technical disciplines, together with banks and global trading companies, to share the risk of EV development and capitalize on quick-to-market strategies aimed at exploiting the continually improving technology, as has already been the case in personal computers. They even suggest that the conventional auto-industry is not adapting to post-Fordist economic and social conditions and is locking itself into the increasing high investment required of construction based on steel stampings, and ever more expensive emission control systems to make the IC engine meet future targets for noxious emissions. The automotive industry reacts with the view that its huge investment in existing manufacturing techniques gives them a impregnable defence against incomers and that its customers will not want to switch propulsion systems on the cars they purchase in future.

It may be that the US domestic market is more resistant to electric vehicles than the rest of the world because the cultural tradition of wide open spaces inaccessible to public transport, and the early history of local oilfields, must die hard in the North American market where petrol prices are maintained by government at the world's lowest level, for the world's richest consumers. Freedom of the automobile must not be far behind 'gun law' in the psyche of the American people. In Europe and the Far East where city-states have had a longer history, a mature urban population has existed for many centuries and the aversion to public transport is not so strong. Local authorities have long traditions of social provision and it may well be that the electric vehicle might well find a larger market outside America as an appendage to the various publicly provided rapid transit systems including the metro and pre-metro. And, according to a CARB contributor to Scott Cronk's remarkable study of the potential EV industry1, with the control equipment in the most up-to-date power stations 'urban emissions which result from charging an electric vehicle will be 50-100 times less than the tail-pipe emissions from (even) ... ULEV' vehicles, a very different story to that put out by IC-engined auto-makers' PR departments.

It is also argued within Cronk's collection of essays that fuel savings from ultra-lightweight vehicles might predate the impact of electric vehicles, on public acceptance, particularly within European and Far-Eastern markets where petrol prices are at a premium and usually bear heavy social taxes. Fuel savings by such a course could be very substantial and the customer might, as a second stage, be more ready to take the smaller step to a zero-emissions vehicle. This is when he/ she realizes that the cost of overnight battery charge, at off-peak rates from the utilities, could prove an irresistible economic incentive. The vehicles would be produced in a lean-production culture which would also help to pare the substantial overhead costs that are passed onto the customer in traditional auto-manufacture.

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