2012 Mercedes-Benz SLS AMG Roadster Undergoing Endurance Testing

The latest simulation software and extensive test drives on all continents make the 563 hp Roadster fit for its U.S. market launch in late 2011. The specialists in Affalterbach particularly focused on bodyshell rigidity, handling dynamics, the soft top and NVH – "Noise, Vibration and Harshness."

In order to achieve handling dynamics identical to the coupe – without a fixed roof - the 2012 Mercedes-Benz SLS AMG Roadster has two features designed to increase the rigidity of the body shell: the cross-member carrying the dashboard has additional supporting struts at the windshield frame and at the center tunnel, and a structure between the soft top and the tank stiffens the rear axle.

These features prevent unwanted vibrations from the start and dispose of additional weight-increasing vibration dampers often employed by competitors. Because of this rigidity, the soft top can be reliably opened and closed electrohydraulically at speeds up to while on the move at up to 31 mph.

By the way, after spending about an hour behind the wheel of the SLS AMG coupe, I can attest to the fact that it is almost impossible to drive this car at 31 mph. Owners will want to drop the top before taking off. Otherwise, who knows what damage can be done as you hit 60 mph in first gear. Will your top go fluttering behind you?

Tobias Moers, 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." Due to the lack of a fixed roof and gullwing doors, it was necessary to design the side skirts more robustly, not just for crash performance, but because test drives showed that the driving dynamics could be improved even further by strengthening this area. Moers said, "The SLS AMG Roadster is a super-sportscar – just like the coupe. AMG is determined to achieve superior driving dynamics with this convertible variant."

The three-layer fabric soft top of the SLS AMG Roadster, which is stored behind the seats in a Z-formation to save space, is also relevant to handling dynamics. This weight-optimized magnesium/steel/ aluminum construction provides a low center of gravity and is designed for speeds up to the maximum of 197 mph (electronically limited).

Engineers stressed that whether open or closed, even at top speed there must be no intrusive flapping, booming, hissing, clattering, whistling or howling. Likewise the plexi-glass windstop and the paneling in the interior, on the soft top and along the beltline must be vibration-free. These precisely defined tests were conducted on the high-speed tracks in Papenburg, Nardo (Italy) and Idiada (Spain).

The superior acoustics, which AMG engineers verified with sophisticated measuring technology, also benefit from another special feature - the seamless, bonded-in rear window made of single-layer safety glass. A special production process not only provides a smooth transition between the outer skin of the soft top and the glass but also leads to low wind noise when the roof is closed – at any speed.

AMG developers of the 2012 Mercedes-Benz SLS AMG Roadster paid great attention to water, sand, dust, heat and cold. One special feature of the compact soft top is the continuous water pocket attached below the soft top to catch rainwater and direct it down to the underbody via two openings on each side.

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 retractable hardtop. Tests include 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, and a final session in an automatic car wash. The rain test simulates every conceivable situation that can occur on any continent.

In addition to various test facilities such as the water chamber and the climate/ wind tunnel, the AMG specialists conduct test drives in all climatic regions of the world. In Laredo, Texas, for example, there is a particularly fine dust that finds its way into practically any gap, testing the absolute limits of the seals.

The compact fabric soft top, which can be conveniently opened and closed in just 11 seconds at the touch of a button at speeds up to 31 mph, must also submit to various tortures. One of these is the standardized soft top endurance test used for all new Mercedes roadsters and convertibles: 20,000 closing cycles on a stationary test rig, followed by 2,500 closing cycles while on the move (whether in extreme heat, icy cold, high humidity or dry desert winds).

The endurance testing of the 2012 Mercedes-Benz SLS AMG Roadster at a glance:

Long-term testing on a variety of different roads:

• • all the components and systems are tested together in everyday operation. Loaded up to their permitted gross vehicle weight, the test cars are put through a precisely defined test program on country roads, highways and in city traffic.

Endurance testing on unpaved surfaces:

• • in this case, the developers focus on the durability of the chassis and suspension components, the entire bodyshell and the integral subframe on which the front axle, steering and engine are mounted. The test cars are loaded up to their permitted gross vehicle weight.

"Accelerated" endurance testing:

• • testing of the entire vehicle, focusing on the powertrain, chassis and suspension. Special features of the AMG program include 6,200 miles on both the Nürburgring's North Loop and in city traffic.

Full-load endurance testing:

• • extreme acceleration and braking maneuvers with a frequent full-load operation, which place extreme demands on the cooling, fuel-delivery and braking systems.

Long-term corrosion testing:

• • corrosion testing of the entire vehicle simulates the toughest dynamic and climatic environmental influences.