After the gullwing version, the open-top variant is the second car to be independently developed by AMG. The Coupe and Roadster concepts were created in parallel - which brought decisive advantages during the development process. During this approx. 3-year period for the SLS AMG Roadster, the engineers devoted particular attention to the aspects of bodyshell rigidity, driving dynamics, the soft top and NVH.
Greater Stuttgart area, spring 2011: the new SLS AMG Roadsters are slightly disguised as they cover their test routes. Easily identified by those in the know, others only see these two-seaters with a fabric soft top as some prototype or other: there are no Mercedes stars or model designations to be seen, just black adhesive foil at the front, rear and along the sides. The proportions speak for themselves, however: a long bonnet, large wheels and a short rear end indicate that this is a sports car of breathtaking design.
There are still several months to go before the world premiere at the International Automobile Show in Frankfurt/Main in September 2011. Enough time to verify the maturity of the new SLS AMG Roadster. The personnel responsible at AMG have already completed most of the work involved, as the Coupe and Roadster were created in parallel. The development and testing of a new AMG high-performance car is based on the digital prototype (DPT). Extensive investigations help to achieve specific objectives. Whether these concern the bodyshell design, weight distribution, engine position, centre of gravity or axle design, or of course the handling dynamics, aerodynamics, ergonomics, crash behavior and production process - the very latest simulation programs allow the very realistic representation of a vehicle and all its characteristics. The digital prototype is therefore a complete, virtual automobile.
In the process AMG also uses the extensive know-how of colleagues at Mercedes-Benz: as in the case of the Coupe, networked development with selected Mercedes-Benz development departments at the Mercedes Technology Center (MTC) in Sindelfingen was intensified.
The latest simulation software and extensive test drives on all continents make the 420 kW (571 hp) Roadster fit for its market launch in autumn 2011. The focus of the specialists in Affalterbach was particularly on bodyshell rigidity, handling dynamics, the soft top and NVH (Noise, Vibration and Harshness).
Synthesis: rigidity, performance and a close-fitting soft top
Naturally all these development aspects are closely linked, as Tobias Moers (44), head of overall development and member of the Executive Board at Mercedes-AMG, explains: "Without bodyshell rigidity there are no handling dynamics, and neither can the close fit of the soft top be guaranteed." As the Roadster variant was already taken into consideration during the conceptual phase for the SLS AMG, the lightweight and extremely rigid aluminum spaceframe was specified at a correspondingly early stage. Owing to the omission of a fixed roof and gullwing doors, it was necessary to design the side sills more robustly. But not primarily to meet the legal requirements in the event of a crash - in principle the Roadster would also manage this with the side sills of the Coupe. Studies and test drives showed that the driving dynamics could be improved even further with this measure, therefore side sills with greater wall thicknesses and chambers were developed for the open-top SLS AMG. Tobias Moers: "The SLS AMG Roadster is a super-sportscar - just like the Coupe. It goes without saying that AMG is also determined to achieve superior driving dynamics with this open-top variant."
In order to achieve handling dynamics identical to those of the Coupe, despite the lack of a fixed roof, the Roadster has two features designed to increase the rigidity of the bodyshell: the cross-member carrying the dashboard has additional supporting struts at the windscreen frame and at the centre tunnel, and a strut mounting stay between the soft top and the fuel tank makes the rear axle even more rigid. These features prevent unwanted vibrations from the start, and make the use of additional, weight-increasing vibration dampers such as those often employed by competitors unnecessary. As another important aspect, it is only if the bodyshell has the requisite rigidity that the soft top can be safely and reliably opened and closed electro hydraulically while on the move at up to 50 km/h. The side members of the front and rear modules in both SLS AMG models are identical. The bodyshell of the Roadster tips the scales at only 243 kilograms - which is comparable to the low, 241-kilogram weight of the SLS AMG Coupe's bodyshell.