Mercedes-Benz SL-Roadster

Innovation, emotion, dynamism and technical perfection

Exterior design
Bertrandt Sindelfingen (now known as Bertrandt Technology Centre) worked out the prototype surface data based on DaimlerChrysler’s scanning. This was followed by the preparation of all the exterior production data in June 1997. The basic surfaces were developed to PTS status, first on Syrko and later on Catia. Joints and flanges at doors, headlamps, bumpers, tail lights, tailgate, roof and other parts were added and inserted.

After various principle sections had been considered in consultation with the specialist departments at the end of 1996, the bodyshell team began work in 1997 on the basis of the top-quality exterior body-shape data. The project called for data generation for the side panel, the rear end and the rear lid throughout the whole development period from PT through PTS to volume production, the front end in the PT and PTS phases and the main and rear floor pans in the PTS phase.

During the three-year design period, resident engineers were assigned to work the customer’s premises. In close cooperation with DaimlerChrysler the process chain was secured, interfaces reduced, communication channels optimised and synergy effects put to efficient use.


The ‘Vario’ roof is one of the technical highlights of the SL. During the innovative retraction process the slightly curved rear window is rotated around its horizontal axis and folded into the boot parallel to the curved roof segment. This solution, which was highly innovative at the time, occupies little space and thus permits a significantly larger luggage compartment volume. We were commissioned by the roof supplier to design the body-in-white roof, the two C-pillars, the rear window and the seals, and so were closely integrated in the project from preliminary development through to volume production.

Based on the body-in-white data, joints and partitions were defined on the basis of the specified roof kinematics. A feasibility study was carried out using empirical values and this formed the basis of the commissioned work. .

The combined efforts of DaimlerChrysler, the supplier and Bertrandt enabled a seamless connection between roof frame, the roof folding process, the functioning of the rear lid and the precision sealing of the various components.

We were also involved in the design of almost all the seals for the SL and the A-pillar trim. Many years of experience and expert knowledge are required to develop a perfect water management system which, in a premium product like the SL, is absolutely indispensable. The fact that the rear window is turned around its Y axis when the roof is retracted posed a particular challenge for the design of the rear window and sealing at the pivot point.
Design of the rear lid
We were also commissioned to design the rear lid, the licence-plate recess for European and US model variants and all the relevant seals. This posed a few problems, too: how to accommodate the latch system, the handle flap, the hinges for both opening directions and the drive motor for the side flaps, which fold in during the roof retraction process and thus make room for the C-pillars. The complex design of the rear lid and its packaging required several optimisation loops, which were agreed with the customer. We were closely integrated into the project from the PT phase to volume production.
Interior trim
Based on the first principle sections, the A-pillar trim, the front roof frame panelling, wiring ducts and attachments and the sun visor with pivots were designed by us.