Lotus Elise Service Notes page 22

Lotus Service Notes Section TDL
AF.1 - GENERAL DESCRIPTION
The chassis frame of the Lotus type M111 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 fasteners. 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 crossmember bolting to the rear of the
engine bay to provide rear suspension mountings and rear body support, and a tubular steel roll over bar bolted
to the top of the chassis structure for additional occupant protection. The cabin rear bulkhead, body sills (inc.
'A' and 'B' posts), front energy absorbing crash structure and scuttle/windscreen mounting frame, are all con-
structed from glass fibre composite and are bonded to the chassis structure using an elastomeric adhesive.
The front and rear body sections are each single piece composite mouldings, fixed to the chassis structure with
threaded fasteners.
Two main chassis siderail extrusions, 210mm deep and 100mm wide, run along each side of the passen-
ger compartment between the front and rear suspension mountings, splaying outwards towards the rear until
the fuel tank crossmember behind the passenger cell. At this point, the siderails curve inwards around each
side of the engine bay to provide platforms for the engine mountings. The passenger cell is further stiffened by
sill extrusions secured beneath the siderails, with the flat floor panel reinforced with ribbed transverse channel
sections running across the inside of the tub, which also provide seat mountings. At the rear of the passenger
cell, an open bottomed crossmember uses a detachable, swaged, closing panel to house the steel fuel tank,
with a further extruded crossmember joining the bottom of the siderails at the rear of the fuel tank bay, and
providing pick up points for the front pivots of the rear lower wishbones. Note that the fuel tank bay closing panel
contributes to the structural integrity of the chassis, such that the vehicle should not be operated without the panel
fitted.
The rear ends of the siderails are joined behind the engine bay with a galvanised sheet steel fabricated
subframe which provides mountings for the rear suspension pivots, engine rear stabiliser and exhaust muffler.
Onto each top side of the subframe is bonded and rivetted a box section extrunded alloy longeron, which extends
rearwards to provide rear body support. Enhanced stiffness of the chassis rear section and additional occupant
protection is provided by a tubular steel roll over bar which bolts to the top of the siderails alongside the fuel tank
bay, with bracing struts running from each top corner of the bar to the rear ends of the siderails.
At the front of the passenger compartment, four transverse extrusion beams are used to provide mount-
ings 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. A extruded floor section is used to reinforce this area, with the space
between the front ends of the siderails housing the heater unit and battery. An extruded scuttle beam links the
tops of the siderails, mounts the steering column, and is reinforced by a panel joining this beam with the
steering rack crossmember, the panel also serving to mount the pedal box. Each end of the scuttle beam
carries a vertical extrusion to mount 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 jig built
unit to which no structural repairs are approved. Superficial, cosmetic, or non-structural localised damage may
be 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 geometry 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 and roll over bar together with jig bonded composite rear bulkhead,
body sills, windscreen frame and crash structure, and the radiator feed and return pipes, heater pipes, battery
cable and clutch pipe which are all routed within the sill panels.
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