Wood used in conjunction with fabric has been referred to already and was the construction of the bodywork of many cars in the 1920s before its replacement by steel. For outer panels this was of fairly thick gauge between 0.9 and 1.00 mm and
much of it destined for the UK Midlands car plants was produced in the South Wales steelworks in ingot cast rimming or stabilized grades (Chapter 3). The rimming steels could be supplied in the ‘annealed last’ condition for deeper drawn internal parts but
for surface critical panels a final skin pass was essential to optimize the paint finish.
For complex and deeper drawn shapes the more expensive stabilized or aluminium killed material was used which conferred enhanced formability. Gradually a change took place – due to weight and cost reduction studies the average thickness of external panels reducing progressively to 0.8 mm in the 1950s/1960s and to the current level of 0.7 mm in use today for the production of the body of unitary construction shown in Fig. 2.1. Internal parts for structural members range from 0.7 to 2.0 mm, the scope for downgauging over the years being limited by stiffness constraints. Therefore although the thickness of strength related parts such as
longitudinal members can be reduced by utilizing high strength grades on the basis of added impact resistance, as rigidity is a major design criterion, and the elastic modulus of steels is constant throughout the strength range, opportunities for substituting lighter gauges are limited. This situation can, however, be improved by use of adhesives or peripheral laser welded joints and examples of the use of these techniques are
given later in this chapter and in Chapters 4 and 6. Although not introduced until 1948 the Land Rover provides a good example of a modern vehicle with a chassis of two standard lengths serving a myriad of agricultural and military purposes. Although answering the rugged off-road requirements of the 4 × 4 vehicle virtually any type of body shape could be tailormade and constructed without the need for a dedicated higher volume facility. When steel was difficult to obtain in sheet or coil form in 1948 the underbody frames were produced by welding together strips of steel cast off remnants and aluminium was used for many body
panels.
Materials for Automobile Bodies
Geoff Davies F.I.M., M.Sc. (Oxon)
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