Ensuring that the soft top is wind and waterproof is a complex undertaking, and AMG and Mercedes-Benz have used the enormous experience gained during 125 years of innovation. There have always been open-top vehicles in the history of Mercedes-Benz – and unlike in the case of many competitors, in an uninterrupted sequence. Every soft top is different, however, and even objectives already defined become more ambitious over time. The five challenges to which the AMG developers of the SLS AMG Roadster gave great attention and commitment were water, sand, dust, heat and cold. One special feature of the compact soft top is the continuous water pocket: this is attached below the soft top to catch rainwater and direct it down to the underbody via two apertures on each side.
All the development aspects of a vehicle which involve flexible deformation are always very complex. Simulations can sometimes lead to false conclusions, and do not always provide the most cost-effective solution. Classic test procedures often help to achieve rapid results. Development project manager Holger Strahl (34): "In this field it is not possible to simulate everything with CAD, and it becomes a matter of trying out, driving, testing and improving. The solution finally approved must also be suitable for series production, of course. Our specialist departments and the overall development team work together very closely in their common search for the perfect solution." He also adds: "There is no such thing as the second-best alternative for AMG."
Endurance test with 16 criteria: the "Sindelfingen rain test"
The rain test at the Mercedes Technology Center (MTC) in Sindelfingen is particularly demanding, and every new vehicle bearing the Mercedes star is required to pass it - whether it has a fixed roof, a soft top or a vario-roof. Extreme quantities of water are used to ensure that the result of the development work is watertight – which is a particular challenge in the case of roadsters or cabriolets. 16 tests must be successfully absolved before approval is granted. Whether during the hose test, when all soft top, door and flap seals are sprayed with a water-hose, the continuous, overnight rain test, the fording test, the icing, swirl and high-pressure tests, or the final session in an automatic car wash – the rain test simulates every conceivable situation that can occur on any continent.