Alfa Romeo recently unveiled the technical contents and manufacturing secrets of the new 'compact supercar' which embodies the sportiness intrinsic to the 'Alfa Romeo DNA': a combination of performance and engineering excellence with breathtaking style. This car is obviously the already mythical 4C. Reason enough to spend a special three part report on this issue on our web site. Aficionado of (Italian) thoroughbred automobiles, enjoy it!
Hans Knol ten Bensel
Checking the front alignment of the superlight 4C supercar...
The Alfa Romeo 4C developers have combined the best technical and manufacturing competencies of two brands: Alfa Romeo and Maserati. Thanks to the internal synergies of the Fiat - Chrysler Group, the two carmakers were able to collaborate. They could integrate Alfa Romeo's design roles and Maserati's manufacturing functions.
Of course, other Italian world-wide leaders in the component industry for high-performance sportscars contributed also with their engineering and technological skills and competences.
In particular, the Maserati plant brings in topmost quality and meticulously studied details reminiscent of hand-crafted work.
As the birthplace of the world's most famous sports- and racing cars, Modena and its surroundings are definitely the place that offers everything a manufacturer needs: tradition, technology and know-how. Of course, most of all, there is the same passion driving the team who conceived, designed and built the Alfa Romeo 4C.
Hi-tech materials for a weight/power ratio worthy of a true supercar…
The Alfa Romeo 4C was born from a clean slate, a prerequisite for conceiving, developing and producing a new concept in the domain of sportscars, the "affordable supercar."
The 4C was designed not only to be an exclusive car both for contents and performance, but also to become an achievable dream for Alfa Romeo fans all over the world.
As a consequence, it was necessary to think of limited production volumes, but still in the order of some thousands vehicles per year and, therefore, decidedly higher than those of the practically handcrafted production typical for this class.
The outer wing being removed here, made of SMC (Sheet Moulding Compound).
The clean slate, was soon assigned new parameters and presented with new challenges. the first parameter was a fundamental reference data point: the weight/power ratio must be less than 4 kg/HP.
To achieve this “supercar” ratio, Alfa Romeo designers could have focused on horsepower, but this would have impacted the purchase and maintenance costs, thus making the car significantly less affordable.
They decided to go a different way; they reduced the car weight by using materials where lightness is combined with efficiency and by perfecting, sometimes even creating, manufacturing processes where high technology is joined to craftsmanship.
Here one sees the Alfa Romeo C4 on a lift for further assembly and measurements
In this way they were able to obtain a total dry weight of just 895 kg, a true record that makes the 4C one of the lightest cars in the world. The 4C is lighter than a city car and its weight/power ratio is indeed less than 4 kg/HP.
So a lot of attention was focused on the materials, each of which was chosen on the basis of its specific weight as well as on the chemical-physical, mechanical and technological properties.
The 895 kg 4C mainly consists of aluminium, steel, lightened SMC and carbon fibre.
Carbon fibre for the monocoque…
The secret of the 4C Alfa Romeo lightness and dynamic behaviour lays in the use of 10% carbon fibre, which represents 25% of the 4C overall volume.
At present, carbon fibre is the material offering the best weight/stiffness efficiency. This is the reason why it was chosen for the monocoque that makes up the central, load-bearing cell of the chassis. The monocoque weighs just 65 kg.
Checking rear alignment of the 4C...
The monocoque was entirely designed by the specialised team of Alfa Romeo and manufactured by Adler Plastic by means of an innovative manufacturing process capable of joining state-of-the-art manufacturing technology and the manual craftsmanship typical of the Italian artisans.
Thanks to this approach, the 'pre-preg' technology inspired by the Formula 1 was also transferred to standard manufacturing, so much so that Alfa Romeo is the only brand capable to assure a production of over 1,000 pieces per year.
'Pre-preg' carbon fibre processed in an autoclave with vacuum bag has marked the transgression from piece design to material design.
The monocoque has reached stress and dynamic behaviour response levels that would be unthinkable with different technologies and materials.
'Pre-preg' carbon fibres may be arranged in an optimum structural direction in relation to the forces, thus producing a result that metal would only yield if layers were overlaid, shims differentiated, and reinforcements added.
In addition, the autoclave polymerisation makes it possible to manufacture box-section structures in one phase, whereas normally the production and assembly of various components often made of different materials is required.
One example would be the door post. In its standard steel version, the door pillar is comprised of approximately 6 pieces assembled to one another and to the car body at different stages of the manufacturing process.
A future delight for Alfa enthusiasts: the dashboard of the C4.
If autoclave polymerisation is used, the door post is a one-piece component included in the load-bearing structure.
The monocoque is a carbon fibre one-piece structure and, as such, it resists external stress with a clear advantage in terms of dynamic behaviour.
Aluminium for the roof reinforcement cage and the front and rear frameworks
Indeed, aluminium is used for the roof reinforcement cage and the front and rear frameworks.
In particular, the designers replaced the traditional rectangular strut section with a newly designed section.
In this way, they obtained lighter and, at the same time, safer frameworks. Frameworks are manufactured using the innovative 'Cobapress' process.
Maserati technicians checking the specifications of the C4 Alfa Romeo...
Cobapress joins the advantages of fusion and the benefits of forging under pressure by compressing the aluminium alloy even further, thus removing any residual porosity. All this determines the component lightening to the advantage of its mechanical properties.
In addition, thanks to the use of seam welding processes, the welding is very precise, the components are not deformed and the filling of the gaps is excellent.
Aluminium also plays the main role in the hybrid-type front brake discs with aluminium bell and cast iron ring gear.
This patented technology developed by SHW guarantees up to 2 kg of weight reduction per disc in addition to better braking. Furthermore, the sophisticated surface finishing technology by brushing increases grip and pedal feeling whereas the innovative release system between disc and bell guarantees a more comfortable and safer braking.
The difference in the thermal expansion coefficients of cast iron and aluminium is compensated by specific steel radial pins that accurately transmit the braking action.
SMC (Sheet Moulding Compound)
Using SMC (Sheet Moulding Compound), a low-density and high resistance composite material, for the body has allowed a 20% weight reduction in comparison with the traditional sheet steel.
The Alfa Romeo 4C is the first standard production car to achieve such a high percentage of low-density SMC: with a weight of 1.5 g/cm³ this material is decidedly lighter than steel (~7.8 g/cm³) and aluminium (~2.7 g/cm³), besides being more malleable.
The 4C breathes the styling DNA of Alfa Romeo...
This feature has allowed a styling and design freedom necessary to create a true, instantly recognisable Alfa Romeo.
Moreover SMC is a stable material which, unlike aluminium, does not strain in the event of minor impacts, has high resistance to chemicals and atmospheric agents, and also disperses noise very well to the advantage of acoustic comfort.
Finally, low-density SMC guarantees a good functional integration of the parts; this in turn entails a reduction in the number of components and operations, and requires shorter assembly times, thus lowering production costs.
PUR-RIM (injected polyurethane)
The PUR-RIM (injected polyurethane) was chosen for bumpers and wings for the same reasons described above. See also the photo below...
It is a lightweight material (it weighs 20% less than steel) suitable for creating very complex design elements, such as the 4C wing, and for keeping an ideal cost/production volume ratio.
Windows with thinner glass…
In the search for the lowest possible weight, no material was ignored, not even glass.
In the case of glass, the lightening was obtained by adopting a real silhouette-thinning approach: all the window glasses are on average around 10% thinner than those normally fitted on cars; this allows for an average weight reduction of 15%.
The windscreen in particular is only 4 mm thick. This is an extraordinary result especially in consideration of the fact that this particularly aerodynamic shape is difficult to obtain on such thin glass.
In next report, we will tell you more about the production of the 4C, and, amongst others, the Maserati factory facilities…
Hans Knol ten Bensel