Galvanized body shell clad

Entirely with composite skin

Panels

Renault have designed a high-rise car which has

a skeletal steel body shell (Figure 1.38, clad

entirely with composite panels. After assembly

the complete body shell is immersed in a bath of

(a)

Figure 1.34(a) VW Golf Estate body assembly

36Repair of Vehicle Bodies

(b)

Figure 1.34(b) Land Rover Discovery body assembly

The history, development and construction of the car body 37

molten zinc, which applies an all-over 6.5 micron

(millionth of a metre) coating. The process gives

anti-rust protection, while the chemical reaction

causes a molecular change in the steel which

strengthens it. Lighter-guage steel can therefore

be used without sacrificing strength, resulting in

a substantial weight saving even with the zinc

added.

Skin panels are formed in reinforced polyester

sheet, made of equal parts of resin, fibreglass and

mineral filler. The panels are joined to the galvanized

frame and doors by rivets or bonding as

appropriate. The one-piece high-rise tailgate is

fabricated entirely from polyester with internal

steel reinforcements (Figure 1.39). Damage to panels

through impact shocks is contained locally

and absorbed through destruction of the material,

unlike the steel sheet which transmits deformation.

Accident damage and consequent repair costs are

thus reduced.

Variations in body shape

Among the motor car manufacturers there are

variations in constructional methods which result

in different body types and styles. Figure 1.40

illustrates four types of body shell – a saloon with a

boot, a hatchback, an estate car and a light van.

Figure 1.41 shows a coach-built limousine of

extremely high quality, built on a Rolls-Royce Silver

Spirit chassis by the coach-builders Hooper & Co.

This vehicle has been designed for the use of heads

of state and world-ranking VIPs.

1.4 Basic body construction

A typical four-door saloon body can be likened to

a hollow tube with holes cut in the sides. The

bulkhead towards the front and rear completes the

box-like form and assists in providing torsional

stability. The roof, even if it has to accommodate a

sunshine roof, is usually a quite straightforward

and stable structure; the curved shape of the roof

panel prevents lozenging (going out of alignment

in a diamond shape). The floor is a complete panel

from front to rear when assembled, and is usually

fitted with integral straightening ribs to prevent

lozenging. With its bottom sides or sill panels,

wheel arches, cross members and heelboard, it is

the strongest part of the whole body. The rear

bulkhead, mainly in the form of a rear squab

panel, is again a very stable structure. However,

the scuttle or forward bulkhead is a complex structure

in a private motor car. Owing to the awkward

shape of the scuttle and the accommodation

required for much of the vehicle’s equipment, it

requires careful designing to obtain sufficient

strength. Body sides with thin pillars, large windows

and door openings are inherently weak,

requiring reinforcing with radiusing corners to the

apertures to give them sufficient constructional

strength.

(c)

Figure 1.34(c) Rover 800 load levelling body parts

38Repair of Vehicle Bodies

A designer in a small coach building firm will

consider methods necessary to build the body

complete with trim and other finishing processes.

The same job in a mass production factory may

be done by a team of designers and engineers

all expert in their own particular branch of the

project. The small manufacturer produces bodies

with skilled labour and a minimum number of

jigs, while the mass producer uses many jigs and

automatic processes to achieve the necessary output.

However, the problems are basically the

same: to maintain strength and stability, a good

standard of finish and ease of production.

Figure 1.42 shows the build-up details of a fourdoor

saloon, from the main floor assembly to the

complete shell assembly. In the figure the main floor

Figure 1.35Front end construction (a) integral or mono (b) composite and (c) front sub-frame, this is bolted

separately to body assembly

The history, development and construction of the car body 39

unit (1), commencing at the front, comprises a toeboard

or pedal panel, although in some cases this

may become a part of the scuttle or bulkhead. Apart

from providing a rest for the front passengers’ feet,

it seals off the engine and gearbox from the body

and connects the scuttle to the main floor. The main

centre floor panel (2) should be sufficiently reinforced

to carry the weight of the front seats and

passengers. It may be necessary to have a tunnel

running the length of the floor in the centre to clear

Figure 1.36Motor body panel assembly using GRP: Lotus Elan (Lotus Engineering)

Figure 1.37Complete Lotus Elan SE body shell

(Lotus Engineering)

Figure 1.38Espace high-rise car with galvanized

skeletal steel body shell (Renault UK Ltd )

40Repair of Vehicle Bodies

the transmission system from the engine to the rear

axle, and holes may have to be cut into the floor to

allow access to the gearbox, oil filler, and dipstick,

in which case removable panels or large grommets

would be fitted in these access holes (3).

The front end of the main floor is fixed to the toeboard

panel and the sides of the main centre floor

are strengthened by the bottom sills (4) and/or some

form of side members which provide the necessary

longitudinal strength. The transverse strength is provided

by the cross members. The floor panel itself

prevents lozenging, and the joints between side

members and cross members are designed to resist

torsional stresses.

The rear end of the floor is stiffened transversely

by the rear seat heelboard (5). This heelboard also

stiffens the front edges of the rear seat panel. In

addition it often provides the retaining lip for the

rear seat cushion, which is usually made detachable

Figure 1.39Espace high-rise car showing

composite panel cladding (Renault UK Ltd ). Plastic

parts are made from a composite material based on

polyester resin: pre-impregnated type (SMC) for parts

1, 4, 5, 6, 7, 8, 9, 10; injected resin type for parts 2, 3.

Parts bonded to chassis: Detachable parts:

1 Body top 3 Tailgate lining

2 Roof 4 Tailgate outer panel

5 Rear wing 6 Rear door panel

9 Front wing 8 Front door panel

7 Sill 10 Bonnet

Figure 1.40Body shell variations: (a) saloon

with boot (b) hatchback (c) estate car (d) light van

(Rover Group Ltd )

The history, development and construction of the car body 41

from the body. The heelboard, together with the

rear panel and rear squab panel, forms the platform

for the rear seat.

The rear seat panel (6) is reinforced or swaged if

necessary to gain enough strength to support the

rear passengers. Usually the rear seat panel has to

be raised to provide sufficient clearance for the

deflection of the rear axle differential housing. The

front edge of the rear seat panel is stiffened by

the rear seat heelboard, and the rear edge of the seat

panel is stiffened by the rear squab panel. The rear

squab panel completes this unit and provides the

rear bulkhead across the car. It seals off the boot

or luggage compartment from the main body or

passenger compartment.

The boot floor (7), which extends from the back

of the rear squab panel to the extreme back of the

body, completes the floor unit. In addition to the

luggage, the spare wheel has to be accommodated

here. The front edge of the boot floor is reinforced

by the rear squab panel and the rear end by a cross

member of some form (8). The sides of the floor

are stiffened by vertical boot side panels at the

rear, while the wheel arch panels complete the

floor structure by joining the rear end of the main

floor and its side members. The wheel arch panels

(9) themselves seal the rear road wheels from the

body.

In general the floor unit is made up from a

series of panels with suitable cross members or

reinforcements. The edges of the panels are stiffened

either by flanging reinforcing members, or

by joining to the adjacent panels. The boot framing

is joined at the back to the rear end of the

boot floor, at the sides to the boot side panels and

at the top to the shelf panel behind the rear squab

(10). It has to be sufficiently strong at the point

where the boot lid hinges are fitted to carry the

weight of the boot lid when this is opened.

Surrounding the boot lid opening there is a gutter

to carry away rain and water to prevent it entering

the boot; opposite the hinges, provision is made

for the boot lid lock striking plate (11) to be

fixed. From the forward edge of the boot, the next

unit is the back light and roof structure (12), and

this extends to the top of the windscreen or

canopy rail (13). The roof is usually connected to

the body side frames, which comprise longitudinal

rails or stringers and a pair of cantrails which

form the door openings (14). Provision in the roof

should be made for the interior lights and wiring

and also the fixing of the interior trimming. The

scuttle and windscreen unit, including the front

standing pillar or A-post (15), provides the front

bulkhead and seals the engine from the passenger

compartment.

Accommodation has to be made for the instrumentation

of the car, the wiring, radio, windscreen

wipers and driving cable, demisters and ducting,

steering column support, handbrake support and

pedals. The scuttle (16) is a complicated structure

which needs to be very strong. When the front door

is hinged at the forward edge, provision has to be

made in the front pillar for the door hinges, door

check and courtesy light switches.

The centre standing pillar or BC-post (17) is

fixed to the side members of the main floor unit

and supports the cantrails of the roof unit. It provides

a shut face for the front door, a position for

the door lock striking plate and buffers or dovetail,

and also a hinge face for the rear door; as with the

front standing pillar, provision is made for the door

hinges and door check. The rear standing pillar or

D-post (18) provides the shut face for the rear end

of the floor side members at the bottom, whilst the

top is fixed to the roof cantrails and forms the front

of the quarters.

The quarters (19) are the areas of the body sides

between the rear standing pillars and the back light

and boot. If the body is a six-light saloon there

will be a quarter window here with its necessary

surrounding framing, but in the case of a four-light

saloon this portion will be more simply constructed.

Apart from the doors, bonnet, boot lid and

Figure 1.41Coach-built limousine: Emperor State

Landaulette (Hooper & Co (Coach-builders) Ltd )

42Repair of Vehicle Bodies

Figure 1.42Body constructional details of Austin Rover Maestro (Austin Rover)

1 Main floor unit

2 Main centre floor panel

3 Access holes

4 Bottom sills

5 Rear seat heelboard

6 Rear seat panel

7 Boot floor

8 Cross member

13 Windscreen or canopy rail

14 Cantrails

15 Front standing pillar (A-post)

16 Scuttle

17 Centre standing pillar (BC-post)

18 Rear standing pillar (D-post)

19 Quarter panels

9 Wheel arch panel

10 Rear squabs

11 Boot lid lock striking plate

12 Roof structure

The history, development and construction of the car body 43

front wings this completes the structure of the

average body shell.

1.5 Identification of major body

pressings

The passenger-carrying compartment of a car is

called the body, and to it is attached all the doors,

wings and such parts required to form a complete

body shell assembly (Figure 1.43).

Outer construction

This can be likened to the skin of the body, and

is usually considered as that portion of a panel

or panels which is visible from the outside of

the car.

Inner construction

This is considered as all the brackets, braces

and panel assemblies that are used to give the

car strength (Figure 1.44). In some cases the

entire panels are inner construction on one make

of car and a combination of inner and outer on

another.