Lightweight garage #7 aluminum chassis @ Audi A8 D2 (4D)

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Lightweight garage, News

The vehicle

This time, the legendary successor to the Audi V8, the first Audi A8, is behind our garage door. With an unladen weight of 1.46 to 1.75 t and an engine output of up to 309 kW and 550 Nm for the W12 engine, the Audi A8 was the flagship of the product portfolio at the time.

©AUDI AG, CC BY-NC-ND 2.0, Audi A8 D2

In addition to the all-wheel drive, the aluminum body was a unique feature of the chassis at the time and paved the way for multi-material lightweight construction and the design of complex aluminum structures.

The technology

This truss structure made of aluminum - also known as the Audi Space Frame - offers advantages from a lightweight construction point of view. The basic idea behind it is a clear functional separation of the individual components. The frame is provided by the economically producible extruded aluminum profiles, which are connected via cast aluminum nodes. These are clad with aluminum sheets, although presumably due to the crash requirements for the entire chassis, these only make a small contribution to the overall rigidity.

In addition to the redesign of the vehicle architecture, the production side was also redesigned over 12 years. The specially developed alloys and production and joining techniques not only met the mechanical requirements, such as ductile cast nodes using vacuum casting, but also offered resistance to contact corrosion between plastics and aluminum. Components were glued, welded or riveted.

The lightweight aspect

With this design, the aluminum properties can be exploited and individual components can be designed to withstand loads. One example is the inherent rigidity of the aluminum profiles with several chambers. Other components, such as panels and doors, are attached to this aluminum skeleton. Even in current vehicles, this results in weight savings of up to 40 % compared to a steel version. In addition to aluminum, other materials are now also being used.

©Jens from AudiStory, Audi A8 D2

At 1,750 kg, the 1994 Audi A8 weighed less than the Mercedes W140 S420 at 1,900 kg and the BMW E38 740i at 1,755 kg, despite its all-wheel drive. The cast nodes also certainly sharpened the ideas for subsequent carbon applications in automobiles.

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