In 1981, introduced carbon-fiber monocoques to Formula 1. With the F1 (1993) and the SLR (2003) road-going supercars, it also pioneered bringing carbon-fiber chassis technology to limited-production cars. So it made sense that when McLaren set out to build a production high-performance sports car in slightly higher numbers, the company continued the lightweight design concept by utilizing carbon-fiber construction. As in aerospace, racing or road cars, taking weight out of the vehicle translates to more efficiency and performance.
At the heart of the new is the carbon MonoCell. Working with Carbo Tech in Austria and Toray in Japan, McLaren is able to produce a nearly complete single-piece carbon-fiber tub for the 12C in just four hours. Previously, the F1's chassis took 3000 hours and 100 people to build. It was made from prepreg (epoxy resin already infused) carbon-fiber sheets layered and formed into shape by hand, then cured in an autoclave like a Formula 1 racing car. Even for the , it still required 400 hours to produce six carbon-fiber pieces that were then mated together to form the tub.
To bring the cost down and increase the speed of production, McLaren's MonoCell uses a new Resin Transfer Molding (RTM) process that can be more automated. Instead of using labor-intensive prepreg, sheets of dry carbon-fiber cloth are cut into shape and laid out in a 35-ton, 7-piece steel mold. After the tooling closes, resin is injected. For about two hours the entire carbon-fiber tub is subjected to 218 psi of pressure at 167 degrees Fahrenheit. And before the tub comes out of the mold, it spends another two hours curing at about 260 degrees F.
At this point, the unmachined MonoCell is already within 1 mm of design specifications. To ensure even tighter Formula 1-like tolerances of +/- 0.2 to 0.5 mm at the pickup points of the front and rear aluminum crash structures, the tub is sent to a computer-controlled milling machine for finishing touches. Because the RTM process can accommodate complex designs, a single-piece hollow tub incorporating different shapes and attachment points is possible, making the carbon-fiber chassis that much stronger as a single unit. According to McLaren, the MonoCell weighs 165 lb. It is some 25 percent lighter and stiffer than a comparable aluminum chassis.
For McLaren, the focus on reducing weight does not end at the carbon-fiber tub. The 12C comes standard with specially designed cast-iron brake rotors floating on aluminum carriers. These brakes are more than capable of handling regular on-road duties, but, more important, they are also 18 lb. lighter than conventional iron rotors. Of note, even lighter carbon-ceramic units are available as an option on the car. By having a lithium-ion battery onboard instead of the traditional lead-acid type, the new McLaren saves 22 lb. And in lieu of standard electrical wiring, a lighter wire with a hexagonal cross-section is employed, shaving another 8 lb. And for the car's Airbrake, a flap that rises to help slow the car down above 59 mph, engineers determined a smaller motor could be used for full deployment by raising the flap at a shallow angle, and then using aerodynamic forces to tilt the flap to a more severe angle, thereby maximizing braking assistance. The result is a 50-percent weight reduction in the mechanism, or 11 lb. Other weight-saving measures include having the exhaust pipes come straight out of the rear bodywork above the bumper to minimize length and weight. The same holds true for the radiators that are placed amidships and close to the engine, reducing pipework and coolant volume. Overall, the McLaren MP4-12C's dry weight tips the scale at 2945 lb.
One of the clearest indicators of McLaren's relentless pursuit of weight savings was its "weight down" competition held during the 12C's development. According to Chief Engineer Neil Patterson, teams from the McLaren automotive and racing groups competed to see who could best reduce the car's weight within reasonable financial constraints. Then the best practices were implemented in the final design. Who says racing doesn't improve the breed?
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