September 29, 2009
The first A8 shows its Space Frame, 1993-2003; photo by Jil McIntosh. Click image to enlarge
Manufacturer’s web site
By Jil McIntosh
Audi’s Aluminum and Lightweight Design Center
Neckarsulm, Germany – When it comes to automobiles, weight is the enemy. It affects acceleration, handling and fuel economy, but as buyers demand more safety and convenience features and cars get bigger, vehicle weight has been creeping up.
Audi isn’t the only automaker tackling the problem, but it’s a leader in the technology, which it showcased to a group of international journalists at its Aluminum and Lightweight Design Center, and its A8/R8 assembly facility in Germany. The company’s lightweight aluminum Audi Space Frame (ASF) has been an essential tool in its vehicle construction for 15 years, and last year alone, it applied for 38 lightweight patent designs. Some of its design work is purely experimental, and some is too expensive to be used on anything in the near future, but much is being continually incorporated into new designs. From the A2 and A3 right up to the R8, the company’s cars have reached a point that would make Weight Watchers proud.
Braces make a plastic pedal as strong as a metal one; photo courtesy Audi (top); Lightweight components are crushed to test their strength; photo courtesy Audi. Click image to enlarge
Tackling the problem becomes very involved, with numerous departments coming together to approach it. Lightweight materials play a major role, and the company is constantly experimenting with components made of aluminum, new steel alloys, titanium, magnesium, carbon fibre, and fibre-reinforced plastic. But it simply isn’t enough to just make a part out of aluminum instead of steel, and leave it at that. The new materials have an effect on all aspects of building a car. They will require new methods of shaping and fastening, their costs will have to be taken into consideration, and their lighter weight will affect how the vehicle is balanced. “The designers take the overall weight into account right from the beginning, and then the compounds are examined,” said Heinz Hollerweger, Head of Development, Total Vehicle. “Volume production creates challenges, and active safety items add weight. The weight will also increase as we add electric or hybrid powertrains, because the batteries are very heavy, and the weight affects the cruising range.”
While fuel economy is generally most important to people who buy inexpensive vehicles, the reality is that the know-how needs to start with premium automakers such as Audi: its customers can afford vehicles such as the Audi A8 and R8, and the Lamborghini and Bugatti models that also use the technology at its earliest stages. Those driving A2 and A3 models benefit from materials and production techniques that trickled down from far more expensive models as economies of scale and volume assembly brought down the price, just as features such as air conditioning and power amenities were once restricted to higher-end vehicles and are now found in almost every vehicle around the globe.
The company’s primary objective is to use the best material, and to use as little of it as possible, at exactly the places where it’s needed. If any part doesn’t bear a load, it doesn’t have a place in the car. Audi went to nature to learn the trick of lightweight strength: just as bird bones and elephant skulls are hollow, with bracing inside them to provide rigidity, so are Audi’s parts. A thin-walled aluminum strut with interior bracing is far stronger than a thick-walled piece of steel – the company slams them with several tons of pressure just to be sure – yet is a fraction of the weight, while a clutch pedal made of braced plastic outperforms a similar model made of metal. By reducing a vehicle by 100 kilograms, fuel economy can be improved by 0.3 to 0.5 L/100 km, and CO2 emissions drop by 8 to 11 g/km.
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