McLaren Reveals Transmission Secrets
Following the much-hyped commercial launch in May of McLaren’s affordable supercar, the MP4-12C, the company and its transmission supplier, Oerlikon Graziano, have issued further technical details of the two-seater’s seven-speed dual clutch transmission. So exacting were McLaren’s requirements for every aspect of the new vehicle that, for the transmission, only an all-new design would suffice.
“McLaren has a very clear understanding of its brand and of the type of cars that it should make,” said Oerlikon Graziano head of automotive transmissions, Paolo Mantelli. “This is reflected in the technologies and innovations that are chosen for their powertrains. As well as being immensely fast and dynamically capable, the cars must be comfortable, refined, efficient and a pleasure to drive every day. We worked closely with McLaren Automotive’s engineers to develop a new transmission that would help them meet these targets.”
Because of the vital importance of optimum weight distribution to the handling of the MP4-12C (a car which invites comparison with class-leading elite models, such as the Ferrari 458 Italia and Lamborghini Gallardo), McLaren set especially demanding targets for the axial length of the transmission. A short transmission would allow the engine to sit further back within the wheelbase, reasoned McLaren, to the benefit of mass centralization and the car’s polar inertia, critical to handling agility and steering response. To achieve this, a three-shaft architecture was adopted, along with individual clutches alongside one another rather than nested concentrically.
The result, says Oerlikon Graziano, is a transmission that is the most compact in its class and, thanks to rigorous testing in both virtual and real environments, also the lightest and the most durable. McLaren and Graziano brought a Formula One-style zeal to the challenge of minimizing the weight of the transmission. The complete hardware was subject to extremely sophisticated analysis and went through numerous iterations, so that the maximum amount of weight could be taken out of the components without any compromise to the unit’s stiffness or strength. Weight is just as crucial for efficiency as for peak performance. The low mass of the transmission system is one of the many key factors helping the MP4-12C to a class-leading CO2 emissions figure of 279 g/km. Important, too, are low-friction bearings and optimized internal fluid management.
Oerlikon Graziano also reports a comprehensive set of rig tests to validate the designs to what DCT program manager Alberto Noto describes as the “very high dynamic loads” the car can deliver.
“At 1g, the oil will be at 45 degrees to the horizontal. The McLaren can significantly exceed 1g both cornering and accelerating, and substantially exceed it under braking. Its dynamic performance is phenomenal, which makes managing oil flows critically important,” he says. “As the world’s leading supplier of transmissions for high-performance vehicles, Oerlikon Graziano has developed specialist test techniques that provide insights into these challenges and allow a high level of design refinement, helping us to improve performance and durability while also reducing weight.”
We have already reported on the innovative “pre-cog” function that allows the driver to pre-select the next gear by pulling the shift paddle to its first detent position, much like pre-focusing a camera in advance of taking the actual shot. When the gearchange is actually required, it is even more immediate, something which McLaren claims makes the shift even more engaging than typical DCTs with single-pull paddle shifts. This typifies the thorough approach and McLaren’s desire to optimize the interaction between the gearbox software and hardware, while Oerlikon Graziano says its high-performing synchronizers, fitted to all eight ratios, have been further optimized to allow “substantially faster changes” without compromising durability.
In terms of manufacturing – at Graziano’s plant in Luserna, Italy – the MP4-12C transmission shows some parallels with the system produced by Ricardo for the Bugatti Veyron. Precision automation in the machining of individual components combines with the traditional craft skills involved in hand assembly processes to allow high quality, low volume manufacture in low volumes.
Story Filed: 7/25/2011
By Tony Lewin, managing editor DCTfacts.com