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Starting Out: Car Design Glossary - Part 1
by David Browne, Director Automotive Design, Coventry University   
This Lexus has a joint line in the trunklid. Other makers, such as BMW or Audi) try to minimize this intrusion.
 

Joint Lines

The trunk lids of some cars simply cannot be pressed in one piece because of the inherent right-angled nature of the panel, coupled with the preferred sharp undercuts associated with the design of some license plate recesses. 

The impression of a single panel is achieved by butting and laser welding a separate lower licenceplate-bearing panel to the main boot pressing, but this does leave a (barely visible) joint line. 

The 'intrusion' can be minimised by concealing it with a bright capping, simply 'overwhelming' it with rear-end sculpture and jewelry, or by losing it in a simple undercut 'joggle'.

 

 

Lightlines

Lightlines are effectively 'paths' of reflected light which 'run' along a surface and make it possible to understand its sculptural form without reference to its outline shape (though, of course, the additional information provided by outlines helps build the complete picture).

A highlight is a visible concentration of light which 'flares' off a lightline at a point which is dependent on the position of, and will move with, the viewer.

A car is not, of course, a purely static object, and as it (or the observer) moves, lightlines and highlights will travel along and around its surfaces. Organizing this flow around a complex 3-D form so that it works from any and all angles and views is hugely challenging, and requires great sculptural feel and experience.

BMW 3 Series showing very short front overhang with long rear overhang. A Porsche Boxster has equal overhangs while a McClaren F1 represents a typical supercar with sharply cut-off tail.
 

Overhang

Those parts of a car which project forward of the front wheels and extend rearwards of the rear wheels and which incorporate the crumple zones.

The relationship between overhang and wheelbase is critical in achieving an overall visual balance: too much overhang is a killer. Fortunately, the visual perception of excessive overhang can be reduced by the judicious use of plan shape.

Front overhangs are making a comeback to conform to new European pedestrian impact legislation. One example of this is the Peugeot 407. But the illusion, at least, of a wheel at each corner still lures the stylists.  Fortunately, the visual perception of excessive overhang can be reduced by the judicious use of plan shape.

Designers will say that unequal overhangs add a certain visual 'dynamic' (illus: BMW 3 Series), whereas a car with equal overhangs will tend to look inherently static (illus: Porsche Boxster).

The untypical balance of the generic mid-engined sports car is exactly the opposite - long front overhang and cut-off tail which adds to their distinctive look (illus: McClaren F1).

Design Review: Mitsubishi i
Package

The basic layout of the car, in terms of passengers, engine postion, drivetrain and trunk. It may be defined by a drawing or series of specifications, or more commonly today, by a 3-D CAD model.

The package is usually determined by engineering, and the designers need to ensure the styling design conforms to the set package, although they can negotiate changes to set 'hard points' on a  case-by-case basis.

This Citroen has glass wrappped over the pillars to cover the C- and D-pillars at the rear but the B-pillar is exposed. It is unusual in that it has 2 sets of A-pillars: the main ones in body color, the secondary ones forming the joint with the front door window. From inside, pillars are usually thicker and bulkier than they appear from outside: they need to provide safety and strength for occupants.
Pillars

Pillars fulfill a number of primary functions: they are important structural members, doors are hinged off and/or close on to them, they support the roof, 'cage' and protect the occupants, and visually frame the windows.

Pillars may be 'removed' graphically by being matt blacked out, or by being 'wrapped' by the side or rear glass (illus: Citroen Picasso) and by internal masking to achieve the required DLO graphic.

A-Pillar (or A-Post)

The upright structural supports either side of the windshield which is usually bonded to them. A-pillars invariably flow visually seamlessly into the cantrail. Roll-over requirements are so tough these days that many A-pillars have become worryingly thick, and can obscure other road users. One-box designs, which thrust the A-pillars forward into the driver's field of vision, can further accentuate this.

The base of the A-pillar, where a number of planes conspire to meet, remains the most challenging area to resolve satisfactorily for designers.

B-Pillar

Strictly speaking, the B-pillars of most four and five-door (and some two and three-door) cars are not visible until their door or doors are opened.  What we refer to as B-pillars are actually the adjacent uprights of the front and rear side window frames which sit over, and hide, the actual B-pillar.

The real B-pillar is invariably a hefty, vertical, structural member that front doors latch on to and off which the rear doors are hinged.  It will also accommodate the upper front seat belt mountings.

C-Pillar, D-Pillar (rearmost pillars)

While an A-pillar might have elegance, and a B-pillar is largely plain, functional but anonymous, a C-pillar can have style.  Some, like BMW's 'Hoffmeister kink' have become important marque signifiers.  Strictly speaking, for a car with 3 windows along the side (such as an estate car, SUV or MPV) the C-pillar is the third pillar - that is the rear door pillar. The rearmost pillar is therefore the D-pillar.

Plan Shape

Plan view is simply the elevational view of a car as seen from directly above.

Plan shape, refers to the amount of curvature in body sides, and particularly front and rear ends, as seen from above (i.e. in plan view).

Cars have predominantly constant curvature in plan, but these days this curvature will accelerate or speed up noticeably towards the front and rear ends (where it is referred to as 'tuck in') leading into much more generously radiused corners - or in some cases, effectively, no corners at all.

Clever use of plan shape - visually pulling the corners back - provides the best opportunity to disguise the greater overhangs required by ever-tougher impact testing.