Body: The basis for extreme off-road use

May 5, 2018
Affalterbach

Since its premiere in 1979, the G-Class has successfully relied on uncompromising functionality and outstanding off-road capabilities. Then and now, the basis for this is provided by a ladder-type frame with a mounted body. This design is considerably more robust and suitable for off‑road operations than a unibody construction. The ladder-type frame of higher-strength steel is able to resist torsional forces with greater stability. As the lowest point in the construction, it also ensures a low centre of gravity. Moreover, the robust frame protects the powertrain, fuel tank and exhaust system against ground contact, e.g. when driving over obstacles.

Working on the development of the new G-Class was extremely challenging for the team. "Further technical development of an icon such as the G-Class was both a challenge and an opportunity at the same time. Each part and every bolt came under close scrutiny," explains Dr Gunnar Güthenke, Head of the Off‑Road Product Group at Mercedes-Benz. "With the body, our main focus was on increasing the vehicle rigidity and the connections between the suspension and drivetrain with the ladder-type frame."

Using a digital prototype, the developers simulated the service life of individual components and closed systems to find out in which places it would be possible to make use of lighter raw materials. The diet worked, as the G-Class has shed around 170 kg. The recipe for success: a new mix of materials comprising strong, high-strength, ultra-high-strength steels and aluminium, as well as improved production processes at the Magna Steyr plant in Austria. The rigid bodyshell is now made of a variety of steel grades, while the wings, bonnet and doors are made of aluminium.

To be able to retain the door hinges and handles typical of the G-Class, the developers modified these to suit the new aluminium design. The A and B-pillars are made of high-strength steel in view of their load-bearing function. However, less mass in no way translates into less stability – on the contrary, it was possible to increase the torsional rigidity of the frame, bodyshell and body mounts by around 55 percent, from 6537 to 10,162 Nm/deg. Alongside improvements to the natural driving dynamics and comfort, this also results in enhanced quality in terms of noise levels, among other things, with the positive effect of significantly less noise and vibrations being noticeable in the interior when driving.

Focus on off-road performance

The roof of the G-Class is no longer spot-welded, but instead connected to the body structure by laser welding ‑ resulting in better surface quality and higher body strength. The flanged areas typical of the G-Class, e.g. between the side wall and roof, have been retained but improved for the new welding process.

Off-road capability was once again the main focus during further development of the doors. The side and rear doors have a protective foil cladding on the inside, so that no water can enter when fording watercourses. The surfaces of the frame, vehicle floor and body are specially treated to withstand even the most severe influences – whether water, snow, salt or sand.

For the first time, all the fixed windows of the G-Class are adhesive bonded to the body. This not only increases the torsional rigidity of the body, a particular advantage when driving on difficult terrain, but also makes the window frames more resistant to corrosion.

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