Lotus Eleven/Elise/Exige. Instruction

Page 2

Lotus Service Notes

Section AH

ELISE CHASSIS UNIT

Seat belt mount

ing

frame steel roof hoop

Composite

Scuttle

Seat mounting

crash structure

beam

extrusion

Seat belt mounting

frame backstay

Door hinge

mounting

Sill extrustion

Main siderail

Fuel tank bay

Steel rear subframe

Page 3

Lotus Service Notes

Section AH

AH.1 - GENERAL DESCRIPTION

The chassis frame of the Lotus Elise is constructed primarily from aluminium alloy extrusions and formed

alloy sheet, with the various sections bonded together using an epoxy adhesive with secondary drive-in fasten-

ers. The basic chassis unit includes the passenger cell, front suspension mountings, fuel tank housing, and mid

mounted engine bay, with a fabricated sheet steel rear subframe bolting to the rear of the engine bay to provide

rear suspension mountings and rear body support. A tubular steel seat belt mounting frame is bolted to the top of

the chassis structure and incorporates a roof hoop for additional occupant protection. The cabin rear bulkhead,

body sills (inc. 'B' posts), front energy absorbing crash structure and scuttle/windscreen mounting frame, are all

constructed from glass fibre composite and are bonded to the chassis structure using an elastomeric adhesive.

The front and rear outer body clamshells are each constructed from glass fibre composite mouldings, fixed to

the body and chassis structure with threaded fasteners to facilitate service access and economic repair.

Two main chassis siderail extrusions, 210mm deep and 100mm wide, run along each side of the passenger

compartment between the front and rear suspension mountings, splaying outwards towards the rear before

curving inwards around the fuel tank bay and terminating at each side of the engine bay in a vertical section to

provide engine mounting platforms and a flange to which the rear subframe is attached. To enhance cockpit

access, the height of the siderails is reduced in the door area, and internal reinforcement added in order to

maintain beam strength and torsional rigidity.

Running along the underside of the siderails from the front suspension crossmember to the fuel tank bay

are sill extrusions which carry the cockpit floor panel. The single skin floor panel is swaged for stiffness, and

is reinforced by a ribbed transverse extrusion running across the inside of the tub, which also provides for the

seat mountings. Behind the passenger cell, the siderails are linked by a pair of transverse crossmembers

which are used in conjunction with a folded sheet upper panel to form an open bottomed fuel tank cell with a

detachable, screw fixed, closing panel with swaged lightening holes. Note that this lower panel contributes to

the structural integrity of the chassis, such that the vehicle should not be operated without it fitted.

The rear ends of the siderails are joined behind the engine bay by a galvanised sheet steel fabricated

subframe which provides mountings for the rear suspension pivots nad damper abutment, engine rear stabiliser

and exhaust muffler.

At the front of the passenger compartment, four transverse extrusion beams are used to provide mountings

for the front suspension pivots, and house the steering rack, with an upright section used each side to anchor

the top of the spring/damper unit. Five interlinked extruded floor sections together with additional extrusions,

connect the transverse beams to form an open topped space to house the heater/a.c. unit. An extruded scut-

tle beam links the tops of the siderails at the front of the cockpit, and is reinforced by a panel extending to the

steering rack crossmember. These elements are used to mount the steering column and pedal box, with a

vertical extrusion fixed to each end of the scuttle beam to carry the door hinge pillar.

To the front end of the chassis is bonded a glass fibre composite 'crash structure' which incorporates

tubular sections designed to dissipate collision energy and control the rate of deceleration sustained by the

occupants. Ducting and mountings for the horizontally positioned engine cooling radiator are also incorporated

in this structure.

The bonded and rivetted alloy chassis structure described above is considered a non-serviceable single

unit, jig built to fine tolerances, to which no structural repairs are approved. Superficial, cosmetic, or non-structural

localised damage may be cosmetically repaired as necessary, but in the case of accident damage resulting in

significant bending, tearing or distortion of the aluminium chassis, such that the specified suspension geom-

etry cannot be achieved by the standard range of suspension adjustment provided, the recommended repair

is to renew the partial body assembly, which comprises the chassis, rear subframe and the seat belt mounting

frame together with jig bonded composite rear bulkhead, body sills, windscreen frame and crash structure.

Also included are the radiator feed and return pipes in the chassis siderails, and those pipes and cables routed

through the sills, including the heater and a.c. pipes, battery cable, clutch and brake pipes, and brake servo

and oil cooler hoses.

Page 4

Lotus Service Notes

Section AH

AH.2 - CHASSIS STRAIGHTNESS CHECK

In the absence of visual damage, the chassis may be checked for twist or distortion by utilising the tooling

holes in the underside of the main side rails. If computer processed laser measuring equipment is not avail-

able, instruction checks can be made with reference to an accurately level ground plane, e.g. an accurately set

and maintained suspension geometry ramp/lift. Position the car on the lift, and proceed as follows:

1. Identify the tooling holes in the lower surface of each chassis main side rail. At the front end, between the

suspension wishbone pivots, and at the extreme rear end of each rail.

2. Measure the height of each tooling hole above the reference plane and use jacks to adjust the height of

the chassis in order to equalise any three of these dimensions.

3. Measure the deviation of the fourth dimension from the other three.

Maximum service deviation = ± 2.0 mm.

4. Repeat operations (2) and (3) for each combination of corners to result in four values for the 'fourth' dimen-

sion deviation. If any one of these exceeds the service specification, the chassis should be considered

damaged and replaced by a partial body assembly.

FRONT

REAR

Tooling hole

Tooling

hole

Front wishbone

Rear wishbone

a27/27a

Lotus Eleven/Elise/Exige. Instruction - part 9