17/01/2006
NEWS STORY
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Although the most important change to the regulations for the 2006 season concerns the engines - down from ten cylinders to eight and 3-litre displacement to 2.4 litres - there are also far-reaching consequences for the chassis construction. The V8 power units are shorter, use less petrol and require a smaller radiator surface, which has a significant effect on the car's design.
The minimum chassis dimensions stipulated by the FIA ensure that the cars' overall dimensions will remain almost unchanged. "The more compact engine gives the designers more freedom in the design of the overall car", explains Willy Rampf, Technical Director at the BMW Sauber F1 Team. The reduced tank capacity of the BMW Sauber F1.06 influenced both the design of the monocoque and the position of the engine. Added to which, the shorter engine allowed the engineers to extend the length of the 7-speed transmission's titanium casing. This, in turn, encouraged the construction of a particularly svelte rear end.
Although knowledge gained from the development of the Sauber C24 has not surprisingly found its way into the new car, the BMW Sauber F1.06 is every inch a new design. The engineers focused in particular on aerodynamics, widening their objectives beyond just optimum downforce to enhancing efficiency as well. The construction, arrangement and design of all the car's sub-assemblies and components were based around these criteria.
The front section of the new car has been given some striking new features. The chassis has been lowered considerably at the front, with the effect that the lower wishbones are no longer attached below the monocoque but to the side of the chassis. The nose of the car has also been lowered further to the ground, with its underside curving upwards slightly. Naturally, the front wing has been modified in line with the other changes through a host of optimisation measures. All of these measures help to optimise the air flow around the aerodynamically critical underbody.
The reduced cooling requirement of the V8 engine allows not only the use of more compact radiators, but also smaller apertures in the sidepods. This also benefits the car's aerodynamics. The same applies to the rollover bar with integral air intake, which has been reduced in size due to the engine's lower air throughput. Plus, complex finite-element calculations made it possible to significantly reduce the weight of the rollover bar, while at the same time meeting the stringent safety stipulations.
The shorter engine has allowed the rear end of the BMW Sauber F1.06 to become even leaner and more harmonious, ensuring optimum air flow over the rear wing. The exhaust tailpipes have been moved further back from their location on the C24. The engineers used computational fluid dynamics (CFD) to position them in such a way that the hot exhaust gases are channelled around structural components such as the rear suspension and rear wing in the most efficient way possible.
The development of the rear wing will be a significantly higher priority during the coming season. "Last year we started most races with maximum downforce", explains Rampf. "The high output of the 3-litre engines meant that drag did not play a dominant role at many circuits." That has now changed fundamentally. The 20-percent reduction in engine displacement means the team will be looking at making compromises at many more circuits when it comes to downforce and drag. Whereas in 2005 the team used three basic rear wings for high, medium and low downforce, this year there will be a greater number of variants.
"If we're also looking to achieve the top speed which we've calculated as a target, there will only be a few tracks where we can still run with maximum downforce", says Rampf. And that means aerodynamic development work will focus far more closely than in the past on the development of finely graded rear wing variants.
A totally new feature of the BMW Sauber F1.06 is the design of the front and rear suspension. On the front axle, the layout is influenced significantly by the higher attachment points of the lower wishbones, which reflect the focus on aerodynamics. The rear axle is also a new construction. Here, modified kinematics aimed at responding better to the Michelin tyres were at the centre of the engineers' considerations. As Rampf confirms, "The new rear suspension geometry will allow us to exploit the potential of the Michelin tyres much more effectively."
Lowering the front section also allows the assembly position of the pedals and inboard front-axle components to drop by a similar degree, as well as ensuring a lower position for the driver's legs. All these factors help to bring down the car's centre of gravity.
"Our declared aim in the medium term is to close the gap on the leading teams. The BMW Sauber F1.06 represents our first step in that direction", says Rampf of the team's objectives.
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