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Starting Out: Car Design Glossary - Part 1
by David Browne, Director Automotive Design, Coventry University   
Chrome swage lines on Harley Earl's 1951 Le Sabre concept

Swage Line

Swaging is a technique in which cold metal is formed over a grooved tool or swage. In the early automotive context, the edge of one panel was swaged so that it could overlap its neighbor to create the impression of a continuous surface - usually running along the beltline or waistline. By the time production techniques made one-piece doors possible, the swage line had become a popular, elegant device (and a useful division in two-color paint schemes) often concealed by coachlined or chromed 'waist moldings' effectively becoming, in the process, a feature line.

Today, the term is often used generically - particularly by those with an engineering background - for any raised, continuous, pressed bodyside crease or feature lines.

A car with more tumblehome suggests a faster, sportier car. The Lamborghini Countach had the most severe tumblehome of any production car.


Tumblehome is nautical terminology. It was introduced to automotive design with the advent of curved side glass and the need to describe the convex inward curvature of the side of a car above the belt line or waistline.

Unlike screen angles, the degree or amount of tumblehome is not measured. Oddly, while more recent cars tend to have a lot of tumblehome, this may now be reducing again in order to accommodate cant rail-mounted curtain airbags without further intrusion to lateral headswing.

The amount of tumblehome needs to be carefully balanced by the designer as part of the overall car package. Cars such as the Fiat Multipla or Honda Crossroad (illus. bottom right) are examples of cars with very liitle tumblehome, due to their emphasis on practicality and spaciousness.




See Beltline
BMW's new Mini (above); Lamborghini Countach (below left); Mercedes-Benz 300SL (below right)
Wheel Arch

These are essentially circular apertures in the body sides which admit the road wheels, and importantly, frame them.  At their simplest - and often most satisfying - wheel arches appear to have been surgically cut out of the body sides. 

The relationship of wheel to wheel arch is critical, and designers attempt to make the former fill the latter as fully as possible. 

Wheelarches - and the wheels - may be emphasized by pulling out the body sides locally or by the addition of wheel arch extensions or 'eyebrows'.  Usually textured matt-black plastic, these offer the added bonus of reducing the depth of painted sheet metal between the wheel arch and the top of the wing (illus. new Mini). Clever detailing on the sheet metal may be used to achieve the same result. Larger diameter wheels are an important visual ingredient of a car's exterior, but there is a price to pay: inner wheel arch intrusion will be greater and, in the worst cases, may force offset pedals or the complete driving position.

Although wheelarches tend to conform to either of a few types, there have been some 'trademark' excursions: the aerodynamic 'blisters' on the 1954 Mercedes 300SL; Gandini's distinctive rear arches on the original Lamborghini Countach and the slashed affairs on the Chris Bangle's 1993 Coupe Fiat. 

Extremes of wheelbase proportions: Mitsubishi i (above), Bentley and Audi Quattro Sport (below right)

This is the distance between the front and rear wheel centers, and a critical dimension in the quest for internal space efficiency and optimized accommodation.

Successive models in all manufacturers' ranges tend to be incrementally bigger than their predecessors, but the biggest dimensional gain is invariably to the wheelbase. Overhangs consequently have been quietly shrinking.

The wheelbase is also a critical dimension visually, contributing greatly to the balance and proportion of a car. There are plenty of examples of cars whose appearance has been compromised by inheriting cost-saving hand-me-down platforms from unsuitable relations.

There have traditionally been long wheelbase (LWB) versions of prestigious sedans, the extra length all going into the rear compartment - space, after all, being a luxury. Conversely, lighter and nimbler short wheelbase (SWB) versions of some cars have been specially prepared and homologated for rally use, most famously perhaps, the all-conquering Audi 'Quattro Sport' which took over from the regular Quattro in the mid 80s.


See Fender

Related Article:
Car Design Glossary - Part 2