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Old 10-08-2009, 07:15 AM
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Another feature that helps the 12C to handle at a new level is a development of an electronic system used by McLaren’s 1997 MP4/12 Formula 1 car, – Brake Steer. In essence, it is a system that brakes the inside rear wheel when the car is entering a corner too quickly to make the desired radius. Under normal circumstances the front would wash away wide of the apex the driver wants to touch: in other words, the car is in a state of understeer.

Brake Steer manages the tendency of a car to wash out and brings its nose back on line. It assesses the steering angle to determine the driver’s intended course and applies the inside rear brake to increase yaw rate and resume the desired course.

The system also works on acceleration out of a corner when the inside rear has a tendency to spin, allowing the driver to put power down more quickly. It controls what a limited slip differential would do and obviates the need for such a complex and heavy unit, thus saving more valuable kilos.

The standard brakes for the 12C reduce overall vehicle and unsprung mass. McLaren has developed a composite braking system that uses a forged aluminium bell that attaches to the cast iron disc. This solution maintained the excellent brake feel of a cast iron disc while saving 8 kg. Carbon ceramic brakes will be available as an option, offering fade-free braking performance during high performance driving, but the standard composite brake system is actually lighter than the larger carbon ceramic units.

The design of the standard cast alloy wheels (19” front, 20” rear) was driven by McLaren’s light weight objectives: the light weight styling was agreed in concept, then the wheel was tuned using Finite Element Analysis to take a further 4 kg out of the wheels. Bespoke Pirelli tyres have been developed in conjunction with McLaren specifically for the 12C.

An array of electronic aids is fitted to the 12C that will assist and protect the less-experienced driver, or when conditions challenge even the best. These include ABS, ESP, ASR traction control, Electronic Brake Distribution, Hill Hold and Brake Steer. The level of intervention varies according to the handling mode selected.


Design: everything for a reason

The McLaren MP4-12C has been designed around a demanding mechanical package that puts emphasis on aerodynamics, compact dimensions, performance and efficiency, practicality and comfort. Although the design of the 12C was driven by aerodynamics, it aims to remain contemporary and elegant throughout its lifetime as well as distinctive among its peers.

Frank Stephenson, McLaren Automotive Design Director, helped finalise the design: “Like most designers it’s a boyhood dream to work with high performance sports cars. They are the purest expression of speed and purpose and, with increased consumer demand in this market and environmental aims to the fore, offer designers the ultimate challenge.

The 12C design was therefore led by aerodynamics. At McLaren we have been able to use the Formula 1 techniques and the huge expertise that the company has amassed at the pinnacle of the sport,” explained Stephenson.

“All the fins, vents and the flat underbody are there for a reason. No styling addenda have been incorporated for appeal or style alone. This aerodynamic purity explains why this car can hit top speed with great stability without resorting to tea tray wings or deep front air dams. I really feel that the styling communicates the 12C’s engineering integrity and technical benefits and it is this purity that makes the design timeless.”

The overall design theme supports engineering aerodynamic ambitions. Purity of lines then give the car its character. Successful car design is based on proportions and McLaren’s styling team, whilst driven by the demands of the purest airflow, honed a mix of concave and convex surfaces that present balanced proportions and a feeling of lightness. Nothing is out of place on the car and surfaces interact smoothly and with purpose; surfaces that are integrated into the whole of the car along two continuous lines that flow round the body.

The front is very low since it does not have to house large engine cooling radiators, two of which are mounted longitudinally at the sides. This offers the added benefit of segment-leading space for storage under the bonnet.

The 12C’s face is dominated by large and distinctive air intakes and bi-xenon headlights with LED running lights inspired by the form of the McLaren logo. The McLaren logo itself also graces the bonnet of a car for the first time.

Illumination from the running lights bleeds into three distinctive gills just above the headlamps. The windscreen is deep and low for superb forward visibility and redolent of the McLaren F1: in wet weather it is swept by a single weight-saving pantograph wiper blade, as was the F1.

Stephenson again: “The 12C does not reproduce the F1 design but it unashamedly builds on its functionally-driven engineering and design highlights such as the large, deep windscreen and the low cowl to give the driver good visibility for accurate placement on the road. Any similarities are there for a reason.”

From the side, the 12C cannot be mistaken for another sports car. The dominant side air inlets act as turning vanes and help direct cooling air over the side radiators. This shape was designed and optimised using McLaren’s extensive computational fluid dynamics capability. Likewise, the scalloped shoulders drive airflow to the airbrake, thereby enhancing its effectiveness in the aerodynamic package.

The other prevailing design characteristics are the dihedral doors (a hereditary gene from the McLaren F1), which has a clear purpose, like every other element of McLaren’s design ethos.

The concept of dihedral doors is simply to allow the driver and passenger to get into and out of the car as easily as possible as well as allowing a smaller door opening than would otherwise be necessary.

The simple act of moving the door forward and upwards invites the driver to step across the sill and sit in the car more easily. In tighter parking situations, dihedral doors allow ingress and egress in a situation where another car has parked too closely. In traditional door systems a huge parking space is necessary to permit the doors to open wide enough.

With its single hinge, the dihedral doors offer weight-saving features and are unique to the McLaren brand. As is the unique handle-free door entry system.

The 12C’s rear is unique. It has an aggressive, business-like appearance with its downforce-optimised rear diffuser. The exhaust pipes exit high and in the centre of the car and the rear end is open to ensure efficient evacuation of hot air from the engine bay. The engine itself is visible through the top deck. The LED tail light clusters do not dominate the rear and are hidden behind horizontal black bars. They are only visible when illuminated: the two upper bars light up as LED brake lights and turn indicators.

Aerodynamic efficiency drove the 12C’s design. High downforce helps maintain traction, cornering ability and stability while low drag aids top speed and acceleration. It has a completely flat underbody and smooth upper body surfaces to yield a highly effective drag coefficient and generate very high levels of balanced downforce at high speed.

A nose splitter gives more downforce at the front while guide vanes near the front and rear wheels help to increase downforce with minimal drag penalty and direct air towards the all-important diffuser at the rear.

The active Airbrake is another innovation that made its debut on the F1 supercar and was also incorporated into the SLR. It deploys hydraulically under braking, or when the driver wants to trim the car for increased downforce by using a switch on the Active Dynamics Panel.

Under braking, a piston operated by transmission hydraulics raises the Airbrake to a certain angle. Once a small amount of wing angle is pushed into the airflow, the centre of aerodynamic pressure forces the bottom of the ‘wing’ back. In this way, it raises the airbrake to maximum angle using the ‘free’ airflow rather than relying on another mechanical device.

The Airbrake moves the centre of pressure of the 12C rearwards, whereas it would normally move forward under braking. It improves yaw stability under braking and allows the brakes to work more effectively due to increased downforce. It is also a weight-saving solution that took almost 50 per cent of weight out of the mechanism.

Overall, the 12C is lower, shorter and narrower than key competitors, but has much shorter front and rear overhangs due to its longer wheelbase – a layout that promotes stability and assists handling response.
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