Mercedes-Benz E-Class Coupé and Cabriolet

Familiar Values
Many years of co-operation and mutual trust formed the basis for the Bertrandt project team’s participation in the development of a new vehicle generation: the Mercedes-Benz E-Class Coupé and the recently launched Cabriolet. From June 2004 to the end of 2009, Bertrandt teams comprising up to 15 members were involved in supporting Daimler AG in a wide range of tasks, from body-in-white as well as doors and closures development right through to technical documentation and dimensional management.

The body-in-white: extremely strong

Occupant cell and side walls
The two highlights of the Mercedes-Benz model range are characterised by a sophisticated combination of emotion and efficiency interpreted from new perspectives. Both dynamic and sporty and as a consistent further development of the saloon, the Coupé and the Cabriolet represent a new generation in the era of the upper mid-size segment.

One difference from the saloon that is immediately apparent is the lack of a B-pillar. Bertrandt was involved in developing a concept that ensures that both the Coupé and the Cabriolet have the required stiffness without the need for a continuous B-pillar.

The developers focused their interest not only on the design, however, which the Bertrandt team helped to develop through their work on the interrupted B-pillar. Particular attention was also paid to safety. The body of the two cars was optimised in a joint project involving both teams. The Coupé and Cabriolet each have four independent crumple zones that ensure that forces are distributed over a wide surface area and are transferred away from the occupant cell. As a result, the occupant cell proves to be an almost non-deformable structure both in front or rear impacts and in side impacts (or rollover events).

Passengers are protected in the intact occupant space even in the event of high impact velocities. The use of high-strength steels and sheets with a higher material thick-ness plays a key role in achieving this, as does the installation of additional loadbearing beams. Bertrandt provided support for the wide-ranging and complex body engineering measures that guarantee the torsional stiffness of the body in the two attractive Mercedes-Benz models without an upper B-pillar. The single-part side walls have individually welded inner shells which provide high strength for the roof pillars, the roof frame and the side longitudinal beams. In some cases, additional sheet steel reinforcements were added to the load-bearing components, for example on the A , B- and C-pillars. In addition, the A-pillars are fitted with high-strength steel tubes that are able to withstand even extreme loads such as those encountered in the roof-drop test. The high torsional stiffness and targeted lightweight design of the two models also form the perfect basis for outstanding driving dynamics. The high strength of the roof pillars, the roof frame and the side longitudinal beams provides optimum protection for the passengers.

Doors and closures
For the doors and closures development, fast and efficient working at the highest level was guaranteed by familiar working processes and specialised knowledge on both sides. Within the framework of the project, the Bertrandt teams supported the implementation of the door systems, which are identical for the Coupé and the Cabriolet as part of the common parts concept. Due to the differences in design of the two cars, an additional reinforcement for the side doors was developed to enable the Cabriolet to have the same high safety level as the Coupé. This made it possible to equalise the different crash load paths. A further area of the project to which Bertrandt contributed was the Active Bonnet. This innovation includes three impact sensors in the front section as well as special bonnet hinges that are pre-tensioned and arrested by powerful springs. Upon impact with a pedestrian, the sensors send information to the electronic control unit which, in turn, instantaneously activates two solenoids in the hinges. These solenoids release the arresters so that the rear section of the bonnet is pushed upwards by 50 millimetres by means of spring force. It all takes just a fraction of a second. The Active Bonnet has the effect of enlarging the deformation area in order to reduce the severity of an impact, thus helping to avoid serious head and spinal injuries. A further special feature of this Mercedes- Benz-system is its reversible release mechanism. Drivers can reset the active bonnet to its original position and reactivate the system themselves.

Dimensional management: sustainable developments
Within the framework of dimensional management, engineers from both companies developed a general procedure for tolerance simulation. There are plans to use the procedure for further projects.

Direct transfer: a special mark of confidence
The dedicated communications link that was set up during the development of the Mercedes-Benz S-Class formed the basis for archiving the project data in Smaragd, Daimler AG’s own documentation system. This direct transfer is based on the long-standing good relationship between the two companies and offers a very high level of security.

Conclusion
With their Mercedes-Benz E-Class Coupé and Cabriolet, Daimler AG has developed a vehicle generation that sets new standards in automotive engineering. Bertrandt is pleased to have been able to make a contribution towards this new success story by being involved in various projects.