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.