McLaren’s new Sequential Shift Gearbox (SSG) for the MP4-12C sets a new standard

Article by Christian A., on May 11, 2011

Introducing the lightest and most compact Dual Clutch Transmission (DCT) – the new Sequential Shift Gearbox (SSG) is found in the new McLaren MP4-12C. Sourced from Oerlikon Graziano, the Sequential Shift Gearbox for McLaren should also serve as a new benchmark in terms of durability and refinement of a DCT. Paolo Mantelli, head of automotive transmissions Oerlikon Graziano, remarked that as a carmaker and a brand, it understands very well the type of cars it is should make, as reflected by technologies and innovations found in its powertrains.

Graziano quipped that McLaren is building cars that are not only fast and dynamic, but are also comfortable, efficient and a pleasurable to drive. He noted that Oerlikon Graziano is closely cooperating with McLaren’s engineers to develop a new gearbox that would help achieve those targets. It was eventually decided that a DCT-type transmission should be adapted since it offers both smoothness and refinement. Likewise, a DCT-type transmission may allow for instant gear change sans any torque interruption, which means no drop in acceleration.

Moreover, this type of transmission allowed a highly sophisticated DCT control system that was developed in cooperation with Vocis, a subsidiary of Oerlikon Graziano. It was decided that a compact DCT-type transmission would be created as McLaren aims to maximize passenger space without any compromise in dynamics.

In the process, Oerlikon Graziano opted for three-shaft architecture since the parallel secondary shafts could minimize gearbox length, which means that the engine could be mounted further back. The resulting Sequential Shift Gearbox features eight ratios, all of which employ Oerlikon Graziano's high-performance synchronizers. These synchronizers further optimized to allow quicker gear changes without any compromise in durability. Vocis managing director Mike Everitt said that his team aimed for quick and smooth shifting sans any tricks that could make a DCT feel fast. Everitt quipped that they made sure that there is a highly optimized interaction between the software and the hardware, which leads to quick, accurate as well as consistent and progressive responses. Thus, Vocis paid thorough attention to the fluid dynamics as well as to the design and calibration of the control algorithms constructed using the company’s proprietary architecture.

The new Sequential Shift Gearbox for McLaren features a 'pre-cog' facility that allows for an almost instantaneous gear change feel. When the gear up/down paddle is pulled to the first detent position, the facility directs the gearbox to engage the next gear while preparing the oncoming clutch. Once the paddle is pulled to the second detent, the gear shift is completed in a nick of the time compared to a typical DCT.

This 'pre-cog' facility makes the shift more engaging than a conventional DCT with single-pull paddle shifts. Since McLaren is known for its passion for weight reduction, it is only logical that transmission hardware should be a light as possible without having to sacrifice strength or stiffness. Oerlikon Graziano’s Mantelli remarked that McLaren has very high standards for durability as the SSG was tested in a virtual environment and on purpose-designed laboratory rigs.

Whole-vehicle testing was also conducted. Oerlikon Graziano tested the SSG on rigs to validate the designs for the dynamic loads that the McLaren MP4-12C could deliver. Alberto Noto, Oerlikon Graziano's DCT program manager, disclosed that the oil will be at 45 degrees to the horizontal at 1g. He noted that the McLaren MP4-12C could exceed 1g in both cornering and accelerating as well as under braking.

With this dynamic and phenomenal performance, oil flow management is a critically important matter. Noto disclosed that Oerlikon Graziano has developed specialist test techniques that do not only provide valuable observations about the challenges but also allow an advanced level of design refinement -- helping the company improve the transmission’s performance and durability while making it lighter.

Both the lightweight nature and efficiency of the SSG play an important role in reducing the vehicle’s carbon dioxide emissions. Oerlikon Graziano also employed low friction bearings and optimized fluid thermal management to further reduce the vehicle's emissions. Oerlikon Graziano is producing in low volumes the SGG at its Luserna facility in Italy, employing precision automation and traditional craftsmanship to ensure high quality of the end-product.

After assembly, the produced SSG will undergo inclusive end-of-line functional testing using custom-built automated systems, making sure that every product meets their requirements as delivered to McLaren. Oerlikon Graziano recently commenced production of gearboxes for the new Lamborghini Aventador and for the new Aston Martin Vantage S, using different technology matching the character and technical requirements of these vehicles.

Press Release

New double-clutch transmission for McLaren is the lightest and most compact in its class

The McLaren MP4-12C's new Sequential Shift Gearbox (SSG) is not only the lightest and most compact in its class; supplier Oerlikon Graziano says it also sets new standards for the refinement and durability of a Dual Clutch Transmission (DCT).

"McLaren has a very clear understanding of its brand and of the type of cars that it should make. This is reflected in the technologies and innovations that are chosen for their powertrains," explains Oerlikon Graziano head of automotive transmissions Paolo Mantelli. "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."

A DCT-type transmission was the natural choice as it combines smoothness and refinement with the possibility to change gear quickly with no torque interruption and therefore no reduction in acceleration. It also allowed a highly sophisticated control system, developed in conjunction with world-leading DCT controls specialist Vocis (a subsidiary of Oerlikon Graziano), whose UK-based team has managed some of the world's most challenging and prestigious DCT programmes.

The compact dimensions were driven by McLaren's desire to maximise passenger space without compromising dynamics. A three shaft architecture was chosen because the parallel secondary shafts help to minimise gearbox length, allowing the engine to be mounted further back. All eight ratios use Oerlikon Graziano's high-performance synchronisers, further optimised to allow substantially faster changes without compromising durability.

"We wanted to achieve genuinely fast, smooth shifting without any of the 'tricks' that can be employed to make a DCT feel fast," says Vocis managing director Mike Everitt, who's team also calibrated the transmission.

"The secret is to get the very best out of the whole control system with a highly-optimised interaction between the software and the hardware. This ensures that the responses are not just quick and accurate but are also consistent and progressive. That means rigorous attention to the fluid dynamics and to the design and calibration of the control algorithms, which are constructed using our proprietary architecture."

An unusual feature of the McLaren transmission is a 'pre-cog' facility that can make the already class-leading change time feel almost instantaneous. The driver can pull the gear up/down paddle to the first detent position, commanding the transmission to engage the next gear and preparing the oncoming clutch. When the paddle is pulled to the second detent, the gear shift is completed in a fraction of the time required by a conventional DCT. The system also makes the shift more engaging than typical DCTs with single-pull paddle shifts.

McLaren's passion for weight reduction led to extremely sophisticated analysis of the transmission hardware with numerous iterations so that the maximum amount of material could be removed without compromising strength or stiffness. "McLaren set very high standards for durability too, so everything was tested in a virtual environment, then on purpose-designed rigs at our laboratories before whole-vehicle testing," says Mantelli.

Rig testing was also used to validate the designs for the very high dynamic loads that 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," explains Oerlikon Graziano's DCT programme manager Alberto Noto. "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."

The very low weight is also important in reducing vehicle CO2 emissions, which were further cut by meticulous attention to the efficiency of the overall SSG system. Low friction bearings were specified and fluid thermal management was optimised. The result is a significant contribution to the vehicle's ground-breaking CO2 performance.

The new transmission is manufactured at Oerlikon Graziano's plant in Luserna, Italy, using a combination of precision automation and traditional craft skills to allow consistently high-quality manufacture in low volumes. Comprehensive end-of-line functional testing, using custom-built automated systems, ensures that every transmission delivered to McLaren meets their demanding requirements for Britain's newest supercar.

Oerlikon Graziano has also recently started production of transmissions for the new Lamborghini Aventador and for the new Aston Martin Vantage S, each one using a different technology carefully matched to the character and technical requirements of the vehicles.

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