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.