Advanced Automotive Technology: Visions of a Super-Efficient Family Car

on material substitution--the use of aluminum, magnesium, plastics, and possibly composites in
place of steel--and on optimization of vehicle structures using more efficient designs.

Although there is widespread agreement that improved designs will play a significant role in
weight reduction, there are several views about the role of new materials. On the one hand, a
recent Delphi study based on interviews with auto manufacturers and their suppliers projects that
the vehicle of 2010 will be composed of materials remarkably similar to today’s vehicles.^2 At the
other extreme, some advocates claim that the use of strong, lightweight polymer composites such
as those currently used in fighter aircraft, sporting goods, and race cars, coupled with other
reductions in tractive loads and downsized powertrains, will soon allow total weight reductions of
65 percent to 75 percent.^3 The factors that influence the choices of vehicle materials and design
are discussed below.

Vehicle Design Constraints

The most important element in engineering design of a vehicle is past experience. Vehicle
designs almost always start with a consideration of past designs that have similar requirements.
Designers rarely start from “blank paper,” because it is inefficient for several reasons:

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Time pressure. Automakers have found that, as with so many other industries, time to market is central

to market competitiveness. While tooling acquisition and facilities planning are major obstacles to

shortening the development cycle, they tend to be outside the direct control of the automaker. Design

time, however, is directly under the control of the automaker, and reduction of design time has, therefore,

been a major goal of vehicle development.

Cost pressures. The reuse of past designs also saves money. In addition to the obvious time savings

above, the use of a proven design means that the automaker has already developed the necessary

manufacturing capability (either in-house or through purchasing channels). Furthermore, because the

established component has a known performance history, the product liability risk and the warranty

service risk is also much reduced.

Knowledge limitations. Automakers use a various analytical methods (e.g., finite element codes) to

calculate the stresses in a structure under specified loading. They have only a rough idea, however, of

what the loads are that the structure will experience in service. Thus, they cannot use their analytical

tools to design the structure to handle a calculated limiting load. Given this limitation, it is far more

efficient to start with a past design that has proven to be successful, and to modify it to meet the

geometric limitations of the new vehicle. The modified design can then be supported with prototyping

and road testing.

2 University of Michigan Transportation Research Institute, Office for the Study of Automotive Transportation, “Delphi VII Forecast and Analysis
of the North American Automotive Industry,” February 1994.
3 Arnory B. Lovins and L. Hunter Lovins, "Reinventing the Wheels," The Atlantic Monthly, January 1995, p. 76.