2892465 - Introduction - BODYSHELL PANELS - REPLACING AND REPAIRING

GLOSSARY

Space frame

The Space Frame consists of a structure made from high resistance steel producing a vehicle frame to which the bodywork panels are welded.

Magnesium

A metal which is exceptionally light, in relation to its volume, and has excellent strength properties.It is used in mechanical constructions in the form of alloys of various types and is cast or forged.

Submarining

This is the phenomenon which occurs in the case of a frontal impact where the occupants of the front seats, even with their seat belts worn correctly, tend to slide under the actual belt.

Single-galvanized panels

Panels on which the zinc galvanizing process has been carried out where the panel comes into contact with a solution of zinc salts which deposits a layer of pure zinc about 8 micron thick with a high degree of surface finish through the electrolytic effect

Twin-galvanized panels

Panels on which the zinc treatment has been carried out on both sides: a galvanizing process, similar to that carried out for zinc panels, or through fire deposition, where the molten zinc is deposited on the panel through the heat effectThis process, which is used mainly for structural elements of the bodyshell, can produce zinc thicknesses of up to 20 micron to be used for the parts most exposed to corrosion, compared with the 8 micron normally used for the rest of the galvanized panels.

DESCRIPTION

Introduction

Fiat Auto has produced this collection of technical information to describe the features of the Multipla.The subjects have been developed with special attention paid to the description and teaching aspects, limited to providing minimal ideas, rules and precautions.For information on repair techniques and vehicle technical data, refer to the descriptions in the specific sections in the Repair Manual.

Aerodynamics

The style of the new vehicle, featuring an extremely personalized and original design, has concentrated on developing the high levels of versatility, comfort, functionality and strength already achieved with previous models.

The front section, the side panels with glazed areas, the joined surfaces, the rear section and the underbody have all been designed with special attention paid to the aerodynamic profile and have made it possible to achieve the following results:

  • drag coefficient (CX = 0.31);
  • area drag coefficient (CX x S = 0.866).
These figures are the results of road tests and measurements carried out in the Fiat wind tunnel.These are excellent figures which, in addition to giving fuel savings, contribute to the quietness of the vehicle with significant reductions in aerodynamic noise.

Versatility

One of the features of the Multipla is its high degree of versatility, in effect the vehicle has been designed to accomodate six persons and their luggage.

This objective has been achieved by creating a completely new chassis which allows:

  • an optimum ratio between the internal volume and the surface area occupied on the ground with a ratio of 41% between the habitable area and the occupied area;
  • considerably wider than traditional vehicles;
  • ample space for occupants legs, in particular rear passengers;
  • more headroom for passengers thanks to the vertical configuration of the side panels;
  • a very large luggage compartment capacity thanks to the flat configuration of the load carrying compartment allowing easy loading;
  • a completely flat floor panel to allow the widest possible use of the interior space;
  • a vehicle which is easy to get in and out of, for rear passengers as well, achieved by moving the side pillars as far forward as possible and designing the doors so that they take up a limited amount of space (but with high safety levels), concentrating on the areas which do not hinder movements, all of the armrest area and the door opening handles and the lowering windows;
  • a seat layout, which is the same in shape and size, with two rows of three seats side by side. The rear seats also have two possible attachments, spaced ten centimetres apart, to improve the comfort of the passengers or the capacity of the load carrying compartment.
These features, together with the possibility of adjusting each seat, gives an extremely large number of combinations for the vehicle interior.Possible arrangement of the passenger compartment with all the seats on board
Possible arrangement of the passenger compartment with / without the rear seats

SAFETY

Introduction

The Multipla has been designed, chosing from innovative technology, adopting a so-called Space Frame and adapting the vehicle to meet both European and worldwide market regulations which are very exacting.

Structure of the bodyshell

The Space Frame is the result of radically innovative technology which has many advantages compared with the traditional method of constructing a bodyshell from pressed steel. It consists of a structure made from high-resistance steel forming a frame to which the bodywork panels are welded.
SPACE FRAME STRUCTUREThe choice of using a Space Frame for mass production has led to innovative design solutions never used previously.

Special attention has been paid to the design and the production of the structure, especially as far as the following are concerned:

  • the structural intersections of the bodysheel, to increase resistance to stress and fatigue;
  • the production processes to ensure resistance and the seal of the weld areas in time;

The Space Frame structure has many advantages compared with the traditional pressed bodyshell solution; advantages which can be summed up in:

  • lighter vehicle for the same resistance properties;
  • lower industrialization costs;
  • possibility of producing complex, open or closed shapes, constructing "beams" for the special structural requirements of the parts in question.
A further positive aspect is that there are no special repair problems because no different materials other than steel are used.The adoption of a bodyshell with this type of frame satisifes all technical variables in terms of new industrialization solutions and allows for a large number of variatns (for example, Pick Up, 4x4, etc.) with the layout of the mechanical components remaining unaltered. All of this takes market requirements into account, both in terms of quality and price.

Torsional and bending strength

The high torsion and bending strength of the Multipla bodyshell, in addition to endowing the vehicle with excellent passive resistance properties, also translates into manyfold advantages:

  • less noise thanks to fewer vibrations;
  • no creaking from the trims;
  • improved driveability, keeping the suspension angles correct, therefore precise driving giving a sensation of a firm, comfortable ride;
  • increased resistance to breaking caused by the use of the vehicle over particularly uneven roads;
  • the sensation of a compact car;
  • improved maintenance in time of the overall qualities of the vehicle.
Torsional strengthTorsion deformation diagram
Torsional strength values

Bodyshell with bonded windscreen and third window

  • kgm/rad = 84200
  • kgm/degres = 1470

Bodyshell with bonded windscreen and third window complete with moving parts:

  • kgm/rad = 103700
  • kgm/degree = 1810
Bending strengthBending deformation diagram
Bending strength values

Bodyshell with bonded windscreen and third window:

  • kg/mm = 590

Bodyshell with bonded windscreen and third window complete with moving parts:

  • kg/mm = 630

Preventative safety

This involves all those factors which contribute to driving comfort and allow situations which could distract the attention the driver to be prevented. and can be summarized as follows:

  • extremely rigid bodyshell for greater driving safety;
  • optimum engine mountings to keep transmission of vibrations and noise to a minimum;
  • climate control system, fitted with a pollen filter, with balanced distribution throughout the passenger compartment which, thanks to the arrangement of the vents, allows an excellent exchange of air and comfort;
  • excellent visibility ensured by the extensive glazed area and the external mirrors giving a broad range (the right mirror makes it possible to see the pavement for parking manoeuvres in reverse gear);
  • reverse gear sensor, available on request, which facilitates parking manoeuvres, signalling the distance from obstacles;
  • lights arranged on three levels to give the most effective lighting with:
  • main beam headlamps at the top to limit pitching and broaden the light beam;
  • dipped headlamps in the middle position;
  • fog lights as low as possible;
  • special shaped rear light clusters which give optimum light and signalling functions;
  • height adjustable steering wheel, layout of pedals and driver's seat height adjustable allowing the ideal driving position to be found;
  • excellent layout of main controls, located ergonomically, instruments and warning lights facing the driver with very large characters which are easy to read. All of this has been carefully designed to give a good balance between the driving position and accessibility allowing optimum comfort which guarantees the best control of the vehicle;
  • generous dimensions of the interior spaces and wraparound seats (electrically adjustable for the driver's seat, on request) which allow the necessary comfort for the occupants of the vehicle;
  • extensive use of sound insulation materials both on the floor panel and on the bulkhead between the engine compartment and the passenger compartment (covered on both the outside and the inside of the passenger compartment) and the adoption of special fixing solutions for the components to keep down noise and ensure a pleasant, quiet environment;
  • interior fittings which respond to the most stringent regulations governing flammability.
The Multipla also offers the driver the optimum conditions for safe driving thanks to its special configuration which gives a high driving position with excellent visibility.Sound insulationIn order to meet CEE regulations the design of the Multipla has produced exterior noise levels below 74 decibels.The noise level inside the passenger compartment is shown in the diagram below, according to the engine type:

The improvement of the comfort whilst driving, in terms of quietness and the quality of life inside the passenger compartment, has been achieved by:

  • optimizing the bodyshell with the careful design of all components subject to noise, where the rigidity has been increased and the fixings have been reinforced;
  • selecting the contact materials with great care;
  • working on the insulation of noise transmitted from the road surface, the mechanics, the suspension;
  • taking care of the assembly of the parts, the aerodynamics and all those components which, with their inevitable profiles, often adversely affect acoustic comfort, such as the door handles, external rear view mirrors, bumpers, various profiles
  • adopting new generation engine types with technological contents also designed to improve acoustic/vibrational aspects with optimum flexible mountings on all versions

A further area of intervention has been the insulation of the passenger compartment involving:

  • highly efficient sound absorbing materials which are excellent both in terms of thickness and their layout on the vehicle;
  • the elimination of acoustic holes, i.e. areas where noise passes between the engine compartment and the passenger compartment which has been achieved by using double seals and thicker rubber plugs, combining the various sound insulation elements with stricter tolerances to avoid uncovered sections;
  • the extensive use of sound absorbing material seals;
  • sound insulation linings for the panels with thermo-bonding materials applied before painting;
  • linings for the partition and the front running boards to eliminate the sensation of the engine;
  • the application, before painting, of thermo-expandable materials inside the box sections to reduce the transmission of noise;
  • appropriately lining the luggage compartment to reduce rolling noise;
  • carefully studying the couplings and the dimensions of the parts subject to creaking, for example the dashboard, heater and seats where the mountings and couplings have been reinforced;
  • special plugs made from thermo-expandable material have been inserted in the box sections which, during the bodyshell cataphoresis, increase in volume by around ten times thereby completely filling the box section;
These prerogatives of quietness allow the driver and passengers to travel in a relaxed manner without the stress caused by noise, being able to talk without raising their voices or listen to the radio undisturbed.
To maintain the high level of acoustic comfort reached, in the case of repairs the solutions adopted during the construction must be exactly renewed.
Diagram showing the application of thermo-bonded materials on the vehicle
Diagram showing application of thermo-bonded materials on the underbody
Diagram showing the application of sound insulation and sound absorption material on the vehicle
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