Light and aerodynamic bodywork

Tuesday, October 28, 2014

Tags :  corners

As with every component on a modern Formula One car, the bodywork fulfils a number of different tasks. The most obvious is covering the internals of the car, but its primary role is to increase aerodynamic efficiency, so how do engineers design it to be aerodynamically efficient and as light as possible, while also staying within the regulations?

The vast majority of body panels on a Formula One car are made from different types of carbon composite materials. Optimising these materials to provide the best compromise between weight and stiffness (or, if some degree of aero elasticity is desired, a lack of stiffness) is an integral part of the Formula One design process. In some areas, for example the bodywork that forms the engine cover, advances in composite materials such as the adoption of spread tow fabrics has allowed fewer material plies to be used and thus weight reduced. However, finding savings in other areas, such as the front and rear crash structures, is more complicated.

Front and rear crash structures at the of the car must fulfil a number of tasks, specifically taking the most aerodynamically efficient form possible, while also meeting the stringent crash test requirements laid down by the FIA. In the past, the most common method for creating these structures was to use an aluminium honeycomb structure, housed in a composite shell. Here, the aluminium would provide the bulk of the structure needed to absorb the energy of an impact.

In recent years though, advances in composite simulation technology and lay-up methods has allowed structures to be created that do away with the aluminium honeycomb, relying solely on the composite for energy absorption. Honda for example, while it was still involved in Formula One, was able to make a 15% weight saving by replacing its aluminium-based nose cone with a solely composite item. The nose cone used four composite ‘pillars’ inside the nose, which provided energy absorbance as well as good structural stiffness.  

Engineers face similar challenges when constructing the monocoque. On the one hand, weight needs to be kept to a minimum, but this cannot be at the expense of chassis performance. Again, information released by Honda sheds an interesting light on this balancing act. The team found that local stiffness around the suspension mounting points had a far greater bearing on chassis performance than overall chassis stiffness. With this in mind, reinforcing plies in areas of the chassis that did not carry suspension mounts were removed, with a consequent 20% reduction in overall torsional stiffness. Meanwhile, the areas around the front suspension mounts and the engine-to-chassis interface were reinforced. Track testing showed that this had no adverse impact on vehicle performance, and netted a very useful 6.5% reduction in weight and a lowering of the centre of gravity by 2 mm.

No doubt the current teams use many other ingenious methods to find similar weight savings and performance gains, but this example shows clearly why it is sometimes necessary to reassess theories about chassis construction that are seemingly set in stone, in order to find that elusive extra performance.

Written by Lawrence Butcher

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