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Clay Modelling

Clay modelling is one of the oldest and most traditional methods used in car design. Studios are divided in their preferences relating to CAD or clay but many believe that it remains one of the best ways to visualise developing designs in three-dimensions.

GM modellers use renderings, sketches and tape drawings as reference to create a 1/4 scale half model. Using a mirror in this way enables modellers to produce results more quickly. With full proportioned models, substantial time is spent balancing one side with the other.In this view it is possible to see the rig beneath the clay. In the rear wheel arch the base can be seen along with the core of light blue modelling foam.


Clay has been used since the earliest stages of car design and emphasises the strong links between three-dimensional automotive styling and sculpture. Working on the form of a vehicle in clay is a very tight form of sculpture, reliant upon a expert eye and an advanced perception of form and proportion.
Clay modellers work on the Holden FJ many decades ago. This practice is still common today. The modellers shown here are using, amongst other things, gauges to measure height and depth (to balance both sides) and profile guides to ensure the model corresponds to the design.


The Principles

There are several stages to producing a clay model.

First, the scale of the model is determined. Using a package drawing or profile sketch, the vehicles dimensions are worked out and the scaled dimensions calculated.

Using the core dimensions, a rig is built. A rig is designed to be a solid working base for the model as it is built and developed. In the case of small scale models – such as 1/4 scale – the rig will be designed to be mounted on a bench where modellers can stand to work on the model. It is often preferable to position a model to create the most lifelike perspective. In addition to providing a base for the model, the rig is also a means of reducing the amount of clay used on a model. Rather than using expensive and heavy styling clay all the way through, an inner core of foam is often used on which the clay is applied.

Manual Method

With the rig configured, clay is applied. Using a system of ’10-lines’, reference points are transferred from the drawings to the model. Clay is built up to match the profile from the drawings and is then added to fill out all the proportions.

From here, designers can either rigidly follow their drawings, creating guides and templates to help develop the model from the package drawing, or they can begin to experiment and develop the form freely. The beauty of automotive styling clay is its ability to be reworked and continually adjusted. This freedom of form development is rarely matched by computer.
Chevrolet designers work on a full scale Corvette model. Dynoc has been applied to give the impression of real glass and upper body paintwork. Real wheels add to the effect whilst designers make final adjustments to the surfaces.


Automated Method

Instead of designers and modellers labouring over a clay for weeks, many car firms are now in the habit of sending a CAD model directly to a specialist milling machine. The machine can precisely mill out the form and proportions of the 3D computer design in a relatively short period of time, although humans may still be called in to finish the surfaces or make slight adjustments.Although most aspects of a design can be resolved on computer, especially with the aid of virtual reality evaluation, almost all companies will still produce a full size clay towards the end of the process. The cold light of day can produce suprises that manufacturers want to be aware of before a vehicle enters tooling and production phases.

Once a vehicle is completed, one of several next steps may be taken. If the vehicle is to be shown as a concept, it might be painted and detailed but will more likely become the template for ‘hard modellers’ to use to create a production look-a-like with individual panels, real glass and details as well as an interior.

If the vehicle is ready for production, it will usually be scanned using 3D digital equipment which will in turn create a new CAD wireframe model. This will be tweaked by CAD specialists to remove imperfections before being passed on to engineers who will begin the arduous process of creating panels, componentry, drivetrain and propulsion based on the design.

Of course, if a vehicle was simply an in-house research project, as many are, it may never be seen by the public; in fact the clay may be reused in later projects.

These Holden models give an idea of the processes involved and their purpose. Both vehicles are full-size clays that give an accurate representation of the proposed vehicles. Applying a neutral coloured paint and sitting the model outside in a typical working environment is about the most accurate way to assess a concept’s visual impact without actually building it.The vehicle in the upper image appears to be in the later stages of development. Details such as light graphics, shut lines and Dynoc to imitate glass allow designers to quickly and effectively evaluate the model.

CAD Rendering: Virtual Photography with ART VPS

At the sharp end of automotive design, manufacturers are constantly seeking ways to improve the virtual visualisation of their products. CAD rendering allows designers to evaluate their work and assists in the decision-making processes of new vehicle development. In addition to the purely in-house benefits, virtual visualisation can be used to place a design in front of potential customers before production engineering and tooling take place.

Despite the benefits of the system, CAD rendering has often been unable to convey the reality of a design convincingly. ART VPS, based in Cambridge in the UK, have devised a highly successful solution with their ‘Virtual Photography’ process.

The beauty of the ART system is the way it becomes possible to not only convincingly render the CAD form but then to build it comprehensively into an extremely realistic scene.

With ART VPS’s hardware, it is possible to take a computer model and make it indistinguishable from a photograph. Changing the subject’s location or visual properties to create another ‘photograph’ can be done in about 20 minutes, far faster than traditional software solutions. Features such as real-world lighting, physically based materials, and unique camera effects make it possible to create powerful images. The high level of realism allows designers to make decisions on specifics of the aesthetic, more accurately than with previous rendering techniques.

Virtual Photography images are produced through ART VPS’s plug-in interface to major modelling and animation programmes such as Discreet’s 3ds max, Alias’s Maya, Autodesk’s VIZ and Dassault Systemes’s CATIA Photo Studio 2. The interface, called RenderPipe, provides access to ART VPS’s dedicated hardware rendering devices, which enable much higher rendering quality and speed than can be achieved with built-in software renderers.

The Virtual Photography Process, Step by Step

Step One – Data Import

First, the model is imported into or created in 3ds max, Maya, VIZ or CATIA. Often, the CAD model will already exist in a company’s design or styling departments.The image shows the mesh data in 3ds max with a standard blue material applied to it.Click on the images to enlarge.

Step Two – Apply Materials

The RenderPipe interface supports native 3ds max, Maya, VIZ and CATIA materials. ART VPS also provides a library of specially designed RenderPipe (RP) materials or shaders. There is also a specifically developed range of ‘RP-Automotive’ shaders specifically for use in the auto industry for unique functionality and photorealistic material behaviour. The materials are based on the RenderMan scripting language, which makes it possible to tailor them to individuals’ requirements.This image shows the RenderPipe material types in 3ds max’s material browser. These can then be loaded into the material editor. This allows users to create their own materials by simply changing the various settings and colour values. RP materials can also be mixed with standard 3ds max, Maya or VIZ materials, creating many possible variants.

The car uses both standard library materials and RP-Automotive materials such as RP Smoked Plastic and RP Matt Aluminium. The RP Metallic shader is an example of a custom shader, which accurately reproduces special aspects of car paint, including surface perturbation, coloured paint layer, and lacquer or coating layer.


Step Three – Apply Lighting

There are two approaches to lighting: standard and high-dynamic-range imaging (HDRI). Standard lighting techniques use computer graphics lights to replicate real-life light sources. RenderPipe complements the full range of light types found in most 3D packages.ART VPS also provides the option of adding an HDRI image to be used for lighting, reflections, shading and other effects. HDRI has revolutionized the external lighting process. In conjunction with ART VPS rendering hardware, it has made Virtual Photography a reality.

HDRI images contain high resolution contrast data, recorded photographically on location, which is used by ART VPS’s ray-tracing renderer to light the scene. The image also appears as the background environment. This means you are able to drop a computer model into a scene and it will be fully integrated into an apparent real-world environment.

Step Four – Apply Cameras and Render

RP cameras work just like the standard 3ds max, Maya, VIZ or CATIA cameras. In 3ds max, Maya and VIZ they have additional controls for motion blur, depth of field, and lens effects.The ART VPS RenderPipe renderer is integrated with the application. A user selects RenderPipe as the active renderer giving access to a selection of RenderPipe options, including chalk preview, image quality, ray depth, and a preview that shows the entire rendering in progress, rather than just the partial fill shown by many software renderers.

Step Five – The End Results

This scene was rendered in 12 minutes and 34 seconds at a resolution of 1828×1332 pixels.
Because of the way the system works, should it be necessary to make changes to the rendering, it only takes about 15 minutes to modify and re-render the image to incorporate, for example, silver paint work and chrome alloys.


This image illustrates the potential of the Virtual Photography system, allowing the CAD derived object to take on the light, shade and reflection properties of its surroundings.For more information about ART VPS, visit their

Images courtesy & © ART VPS

Lexus model by M Pavos.

Fuel Cells

Fuel cells are largely envisaged as the most likely successor to the internal combusion engine (ICE) and are at advanced stages of development for use in motor vehicles. Fuel cells are not restricted solely to transport and can be used for power generation in a range of contexts. It is however, transport that is believed to hold some of the greatest possibilities for the technology.

Mercedes-Benz A-Class NeCAR Fuel Cell Vehicle


Background and History

The fuel cell was invented by Welshman Sir William Grove in 1839. It was his ‘gas voltaic battery’ that laid out the principles for modern fuel cells. Grove new that passing a current through water caused the separation of water into hydrogen and oxygen and hypothesised that the reaction could be reversed – thus creating an electric current. From his experiments, he created the first fuel cell. The term ‘fuel cell’ only came later in 1889 with Charles Langer and Ludwig Mond’s attempts to produce a working device.

In the 1960s, NASA used fuel cell technology to create electricity for spacecraft. Further development took place in the ’70s but it wasn’t until the 1980s that testing began in the automotive industry. In the mid ’90s, automotive prototypes were finally coming closer to practical use but the size of componentry was still a serious problem. Now, the size of fuel cell components has become manageable and testing is in advance stages.

Ballard Fuel Cell Timeline

The Principles of Fuel Cells

In the most basic sense, a fuel cell works in a similar way to a battery, changing chemicals from one form to another, generating an electric current as a by-product. The key difference is that whilst batteries hold energy to be released, fuel cells can generate energy only whilst they are supplied with fuel and air. The fuel used is typically hydrogen but can take other forms.

Unlike the combustion engine, a fuel cell has no moving parts making it far more efficient. Power is output as electric current which is passed to electric motors which in turn drive the vehicle. A combustion engine can actually only ever transfer a fraction of its input energy into motion; with substantial losses due to converting heat into mechanical energy. Toyota have stated that their conventional petrol engine offers a ‘tank-to-wheel’ ratio of 16% compared to their fuel cell vehicle which offers 48%.

In terms of vehicle design, fuel cells can now be packaged within relatively standard proportions.

The following components must be incorporated:

  • Fuel cell stack
  • Battery
  • Electric motor(s) – depending upon your choice of drive configuration
  • Hydrogen tank
  • Electronic contol unit.

The Main Types of Fuel Cell

Proton Exchange Membrane (PEM)
PEM fuel cells are relatively small with a good power generation ratio for their size. These systems use a solid polymer membrane as the electrolyte and operate at low temperatures. The solid electrolyte means simpler production and longer life whilst low operating temperatures allow faster start-up and power increase responses.

Proton exchange membrane fuel cells are the choice for automotive applications due to the favourable performance they offer in a small package. All current automotive fuel cells use the PEM system.

More details on the PEM Fuel Cell

Alkaline systems need pure oxygen and hydrogen to work which makes them less versatile than other types of fuel cell.

Phosphoric Acid
Common for use in industrial power generation, they are typically used in static applications. With their high operating temperature, corrosive electrolyte and complex system, they are not appropriate for automotive roles.

Molten Carbonate
These systems are highly complex and use a molten electrolyte. This means the system operates at very high temperatures; this allows the process to take place without a fuel processor but it is only used in wholesale energy production applications.

Solid Oxide
These systems run at extremely high temperatures and can operate with far less pure fuels than other systems; their overall operation is relatively simple. Planned use as very large static power stations.


This section looks at the principles and design concerns associated with the most common form of automotive propulsion – the internal combustion engine as well as some of the less well know variants and alternatives.

The Internal Combustion Engine


The Wankel / Rotary Engine

The rotary engine was conceived by Felix Wankel in Germany in 1926 with the first functional prototype not actually running until 1957 – this was largely due to the Second World War and the fragmented post-war Germany.

Electric Motors

Electric motors were one of the earliest means of propelling autocars.


Recycling vehicles and their components is a serious concern to manufacturers. (More information on the European End-of-Life Vehicle Directive.) The core materials used in most vehicles today are quite straight-forward to recycle. This page takes a look at recycling considerations within the automotive industry.


Steel is the most common material in vehicle production. It is relatively easy to reclaim and recycle. Two-thirds of steel used in US car manufacturing is recycled (source: Steel Recycling Institute); the remainder is new. Aside from environmental considerations, it is economically preferable to recycle due the large costs in obtaining steel from ore. New steel is generally used when recycled supply cannot meet demand.


Aluminium is still a small material by volume in car production. Obtaining Aluminium from Bauxite (ore) is an expensive process that requires considerable electric current; it is for this reason that Aluminium was once a semi-precious metal and has only (relatively) recently entered mainstream use. Recycling is quite straightforward with aluminium and, like steel, is economically preferable.


Plastics come in two types – Thermosets and Thermoplastics.

Thermosets are made up of strong bonds that are created with heat and subsequently do not melt with heat. This means that they cannot be reused and are either scrapped when finished with or ground down to make a filler material for something else. Thermosets are being phased out from car production as and when possible.

Thermoplastics, on the other hand, become fluid (plastic) with heat. This means they can be melted down and remoulded or added to new material. This characteristic makes them ideal for recycling on cars; it is necessary however, to match the properties of Thermoplastics carefully to their role on a vehicle; polypropylene and nylon are often used for the demanding conditions of the engine bay.

Precious Metals

Electronic components and circuitry are often made up of thousands of complex elements which are almost impossible to seprate and recycle. Within this componentry there is a variety of toxic metals such as lead and cadmium in circuit boards, mercury in switches and flat screens and brominated flame retardants on printed circuit boards, cables and plastic casing.
When dumped, these metals contribute to a range of types of pollution with serious consequences to human health and the environment. As increasing amounts of electronics feature in cars, this will become of greater concern.

End of Life Vehicles & Recycling

On September 18th 2000, the European Parliament and the Council of the European Union produced a directive relating to End-of-Life Vehicles (ELVs). This will form the basis of future legislation for, and implementation of, greater recyclability of motor vehicles. Much of the directive relates to the legislation needed to ensure the aims are met but some significant points are raised which refer to the ways in which design and manufacture will need to be changed.

Currently, the proportions of material in a car are approximately as follows:

Ferrous metals 70%
Plastics 10%
Rubber/Elastomers 7%
Light Alloys 5%
Glass 4%
Miscellaneous 4%

Use of plastics has increased in recent years as manufacturers attempt to remove weight from vehicles. Plastics have often been used where their use represents improvements in structural ability, durability and appearance. For example, rubber coated metal bumpers have long since been replaced by more aesthetically pleasing and impact absorbing moulded ABS. Roof rails, windscreen wiper mount areas, inner wheel arches and engine components are typical of the parts of a vehicle that have changed in material.

Where cars may have had a double skin inner wheel-arch some years ago, a plastic skin may now be used which is more resistant to corrosion, offers greater sound damping qualities and reduces weight. Under the bonnet, some metal ducting, manifolds and mounts can be replaced with durable, heat-resistant plastics, again saving on weight. As Siemens puts it: “lightweight, recyclable plastics reduce costs, simplify vehicle assembly and improve under-bonnet packaging”. Such changes typically mean less ferrous metals are being used in vehicles than a decade or so previously. The replacement of these metals with lighter plastics represent significant weight savings.

In the US and Europe, more than 94 % of End-of Life Vehicles are processed. Of these processed vehicles, 75 % of the vehicle by weight is recycled or recovered. Generally speaking it is composite components that prove most difficult to recycle. They are made up from combinations of materials that have to be separated before they can be successfully recycled. The complexity of some of these items, and in the case of batteries, the toxicity of the materials used tend to mean they are land-filled instead of reused or recycled.

The End-of Life Vehicles Directive lays down some very stringent guidelines regarding recycling over the next few years and for the foreseeable future. By January 1st 2006, all ELVs must be at least 85% reused and recovered and at least 80% recycled. By 2015, reuse and recovery must increase to at least 95% whilst recycling must be at least 85%.

Material that isn’t recycled is known as ASR (automotive shredder residue). Despite recycling a greater proportion of the end product than most other industries, the auto industry still landfills millions of tonnes of waste a year in Europe alone. The problem with recycling is cost; the cost to dismantle; the cost to the process; and the ability to find uses for recovered material. In the European ELV Directive, it specifically refers to an overall coherence in approach to the issue, “particularly with a view to the design of vehicles for recycling and recovery”. It states that “it is important that preventative measures be applied from the conception phase of the vehicle onwards”. This will obviously have a bearing on the early design and development stages of a vehicle.

Measures such as the prohibition of Lead, Mercury, Cadmium and hexavalent chromium and the increasing percentages of reuse and recyclability will force car and component manufacturers to develop products that can be more easily dismantled and broken down. Processes will be sought to deal with composite components as well as alternatives if they prove more practical or where a material is banned from use. The greatest demands will fall upon the manufacturers to create networks of dismantlers and recyclers and on component suppliers to ensure their products can be easily recycled. It appears that because figures for reuse and recovery are high, anything that cannot be recycled will mean additional cost to the manufacturer.

Designers will need to look always towards the newest materials and processes. It will be necessary to design and engineer vehicles to be more easily dismantled and avoid creating complex mixtures of materials. Parts of a car will need to be “labelled or made identifiable” to aid the recovery process. Ford began issuing its designers with “design-for-recycling” guidelines in 1991. The Focus, for example, is designed to have 50% of its components dismantled in thirty minutes.

The increasing demands for recyclability and environmental accountability may mean designers are forced to look at more intelligent solutions – making use of new materials and technologies rather than using existing inefficient and wasteful devices and components. Despite the ever increasing demands on electrical power within the car, it may be necessary to look towards more efficient energy use rather than simply increase battery capacity which will cause significant problems with recycling and recovery. In essence, designers must apply a greater degree of intelligence to design. Careful selection of materials and components will be key to making a vehicle design a viable proposition. Having designed a range of durable thermoplastics capable of withstanding the conditions of the engine bay, Siemens now use fully recyclable thermoplastics in all new designs; illustrating how a change of approach needn’t affect the overall result. Designers should also push to bring new technologies to the fore earlier to ensure vehicles meet the increasingly stringent requirements of legislation.

Taking a general view, it is unlikely that designers will need to make large changes to their practices or to make substantial concessions. However, it will be necessary for designers to be aware of the legislation that their vehicles will be required to meet and to be prepared to take different approaches to design to account for this. For example, computer design systems exist which take into account the ability of a product or vehicle to be recycled. By taking account of the structures and materials involved, the process of evaluating the impact to the environment can be automated. Designers will increasingly be required to use computer design systems which will outline these issues to them before any concrete decisions are made to manufacture the product or vehicle.

In the next five to ten years, we will see vehicles being made from increasingly reusable and safer materials. They will be easier to dismantle and will have a far smaller impact on the environment in terms of their ultimate disposal than the current materials of choice. Designers will need to be aware of the restrictions of legislation imposed upon them whilst engineers and scientists will be required to find safe, efficient alternatives to the hazardous and complex parts of a motor vehicle.

Global Car Production Figures

Listed here are the global sales figures for many well-known manufacturers. Whether a company’s information is listed here or not is a reflection of the ease of access to the necessary data, rather than any other consideration. We will endeavour to expand this section to include a greater number of companies in the future.

Figures are listed specifically for the trading name of the manufacturer without including its dependencies or subsidiaries (unless otherwise stated). See the footnotes for details of manufacturing groups and joint results.

Manufacturer 2002 2003 2004
Audi Brand Group 2 1,191,000 1,217,000
Aston Martin
BMW Cars 913,225 928,151
BMW Group 1,057,344 1,104,916
BMW Motorcycles§ 92,599 92,962
Buick 6 432,017 336,788
Cadillac 6 199,748 216,090
Chevrolet 6 2,642,786 2,655,777
Chrysler Group 4 2,820,000 2,640,000
DaimlerChrysler Group 4,300,000
Ford (Worldwide) 6,973,000 6,720,000
GM Cars (US) 2,063,875 1,960,682
GM Trucks (US) 2,790,140 2,795,721
Holden 9 178,392 175,412
Hummer 7 19,581 35,259
Jaguar (US) 61,204 54,655
Land Rover
Land Rover (US) 40,987 39,035
Lincoln 150,057
Mazda 8 936,371 1,068,400
Mercedes-Benz Group 5 1,232,300 1,216,900
Mini 144,119 176,465
Nissan 2,693,737 2,957,757
Oldsmobile 6 155,113 125,897
Pontiac 6 516,832 475,615
Renault (passenger cars) 1,902,322 1,896,128
Renault Group 1 2,404,889 2,389,022
Saab 120,831 131,706
Saab (US) 47,914
Saturn 6 280,248 271,157
Volkswagen 3 3,539,000 3,549,000
Volvo 406,112 415,046


1 – incorporates Dacia, Renault Samsung and Renault light commercial vehicles.
2 – Audi brand group incorporates Audi, Seat and Lamborghini.
3 – Volkswagen brand group incorporates VW passenger cars, Skoda, Bentley and Bugatti.
4 – Chrysler Group incorporates Chrysler, Dodge and Jeep brands.
5 – The Mercedes Car Group includes Mercedes-Benz, Maybach, smart, Mercedes-Benz AMG and Mercedes-Benz McLaren
6 – Part of GM Car (US)
7 – Part of GM Truck (US)
8 – Refers to ‘Key global Markets’ (Japan, the US, Canada, Europe, China, Australia, Thailand, New Zealand, Singapore, Taiwan, Hong Kong, Israel, Saudi Arabia, South Africa, Colombia, Chile, Venezuela and Puerto Rico)
9 – Passenger cars and light trucks

Automotive Manufacturing Processes

Modern manufacturing and assembly processes, whilst highly refined and advanced, are still based in principle on the production-line pioneered by Ford for the Model T in the early years of vehicle mass production. Contemporary systems are fast, precise and now not only actuated by robots, they are increasingly setup and configured by computer.



Body-in-White Assembly (BIW)
Following delivery of parts from the press shop the vehicle is assembled from the inside-out.
– Assembly of various modules, typically joined by cramping and spot welding.

Base coat
Top coat
Drying unit
Conveyor to assembly

Final Assembly
Trim (including interior modules)
End of line detail assembly

Testing and inspection


World Auto Steel – covering all aspects of car production with steel.