Economy and Function
Never before has the car of the future come in for closer examination within the auto industry, in government circles, by the fuel and energy producers, by the financial world, and at the consumer level. The shape of the future cars will depend on fuel prices and availability, the cost of raw materials and labor, road and traffic conditions, and regulations concerning auto safety, the effects of automobile use on the environment, technological advances, and competition for the markets.
Design is dictated by function. If that rule is not observed, gross inefficiencies will result. The function of a car as a transport medium depends, above all, on the intended payload. That includes the number of passengers, the amount of luggage/cargo (in terms of weight, size, and shape), and other items forming part of the payload
A second part of the car’s function is the speed with which it is intended to carry its payload. Speed costs money. Inevitably, a fast car costs more than a slow one.
Speed is inseparable from acceleration. It’s not just the cruising speed that matters, but also the time it takes to reach the intended travel speed from standstill or to resume normal speed after driving at reduced speed.
Higher performance demands more power. This means a more expensive engine-bigger or more highly stressed. In either case it will cost more. It will also consume more energy in operation. If it’s bigger, it will be heavier and demand more installation space. These are serious considerations. Design must be very practical for the operators needs as well.
The body must have convenient openings for passengers to get in and out and for loading and loading luggage. Step height must not too high and door sills must be sufficiently wide. Doors must be positioned so that they correspond to where the seats are, and nothing must obstruct the doorsill area. Doors must be wide enough and high enough and swing far enough.
Trunks should be shaped to resemble a cube or two cubes joined (as closely as possible) so as to accept the bulkiest pieces of luggage. The liftover height should be low, and the lid must correspond in size to the trunk capacity so that any object that will fit in the trunk can actually be put there.
Examples abound-modern and not so modern-of cars failing to meet one or more of these basic requirements. The designer’s difficulties do not end with the practical needs of driver, passengers, and cargo. Body design must also allow for logical and space-efficient accommodation of all the mechanical elements needed to make the car go (such as engine and transmission, suspension systems, steering and brakes).
Due attention must be paid to the dynamic safety of the car, unladen or with maximum payload. Just as cars start and stop, they also change direction of travel. In every turn, the car and its payload are subject to centrifugal force.
Consequently, the center of gravity should be as close to the ground as permitted by the design concept. Not just the heavy components, such as the engine and the transmission must be considered, but also the payload. Equal or nearly equal front/rear weight distribution is also regarded as a desirable feature.
Making the car economical is extremely important. The auto industry has undertaken successive phases of a general down-sizing weight-shedding and streamlining process that will enable the companies to produce cars giving higher fuel mileage. The energy picture will force the industry towards further improvement, while also refining its products to give better satisfaction in other respects. During the rush to downsize, conventional considerations such as comfort and practicality were given secondary importance. And some cars suffer for embodying less intelligent solution than others.
The fuel economy of a passenger car with a given powerplant and performance is determined significantly by the vehicle’s tractive resistance which essentially is composed of inertial resistance, aerodynamic drag, and rolling resistance. While rolling resistance problems can be handled best by the tire industry, the car designer can take appropriate measures that affect the other two resistances. Inertia resistance largely is a function of vehicle weight, while aerodynamic drag can be affected by the configuration and ducting of the air-flow. Further vehicle weight reduction using the standard materials by design modifications is limited. Therefore, alternative materials would have to be used, which, in all probability, would entail higher cost. The aerodynamic drag may be reduced substantially by proper styling, which might give the vehicle a somewhat new appearance but is not likely to result in significant additional cost.
Other factors than fuel must also be taken into account at the design stage. Oil consumption and tire wear are also part of the total consumption picture. Lubricating oil is more expensive than gasoline or diesel fuel, and it is important to make the most use of it (which means smaller oil pans and larger oil-change intervals).
Tyre life is another important part of the overall running costs. Car tyres are made mainly from synthetic rubber (based on petrochemicals). Longer tyre life helps conserve oil resources in addition to easing the cost per mile to the owner.
It has been observed that improvements in air quality do follow the industry’s drive to improve fuel economy because emissions are by-products of a fuel-burning process. Burning less fuel will produce lower levels of pollutants. As long as the energy crunch is with us, there will be a strong pressure for improvement on all fronts.
Energy consumption means more than just fuel consumption. It starts at the manufacturing stage. How much energy is spent in building the car? Energy is consumed in making the steel, aluminum and other materials used. And it takes energy to run the assembly line. You can add up all the energy inputs for the total car and draw certain conclusions. A change of materials for one or more applications might be indicated or there might be a need for a different method for assembling the car.
The use of lightweight materials to reduce car weight is to some extent counteracted by the greater energy input needed to produce workable auto parts from such materials.
Weight-saving can make a big contribution to improving a cars fuel economy. First there is the primary saving gained by substituting a part of lightweight material for one of the heavier construction. For every such part there is a secondary saving in the form of lighter structural loads, which is known as a ‘knock-on’ or ‘ripple’ effect. For instance a lighter engine opens the way for also lightening the drive train, suspension system, frame and/or body shell and so on.
"Product planning" does not mean the planning of a specific new car. Product planning stops before the new car project is defined in terms of type, size, layout, componentry, and price. The task of what is called product planning comprises information-gathering and data analysis with a view to predicting market trends and opportunities. The product planner, therefore, as a specialist in identification of trends and interpretation of marketing data, with the aim of providing an economic map of long range developments affecting the automobile. This is then used to draw certain conclusions about the new product and it’s long-range objectives.
Once the project has been fully defined and scheduled for production, a cost target has to be worked out. That means co-ordination with production specialists at an early stage. Decisions must be made quickly as to the extent to which existing components can be used.
Whenever new mechanical components are needed, the decision must be made whether to manufacture them in-house or buy them from outside or associated suppliers. If a new engine is needed, that is a matter of such great scope that it goes beyond the individual car project. An engine needs along time for testing and development, and a long lead time for tooling after the design has been frozen. The investment in a new engine is so heavy that car companies try to use them for twenty years or more.
The car type, approximate size, and certain other specifications are contained in the concept of the program. The engineers start by packaging. That means accommodating the desired number of passengers and the mechanical components into an envelope that corresponds to the size, weight, and performance targets.
This envelope is the basis of the car designers’ work. The designer is responsible for the artistic development of the final product. Of course the designer must co-ordinate their work structures specialists, body engineers, and manufacturing engineers who can rule on the feasibility of innovations proposed by the designers.
The car designer is by definition a creative person working on concepts five to ten years old. His productivity is continually placed under the constraints of cost, feasibility and regulations. Designers who create the shape, colour and texture of these objects (cars) are involved in an art form of a very high order, and they combine this art with the practical considerations of function, manufacturing feasibility, consumer acceptance, and cost.
In 1979, GM engineer Richard E. Fancy said "Market trends, investment limits, manufacturing capabilities, future regulation, and other forces all serve to focus the designer towards reality, yet the designer continually challenges both planners and engineers to see the limitations in a new light and push back the limits of reality"