The Story Behind: The Aluminium Car Frame

Car frame design slowly embraces a lighter alternative

The Aluminium Car Frame The rise of the automobile can be linked directly to a single raw material - steel. While the very first automobiles were modelled on horse carriages and made of wood, it was the wide availability of steel at the beginning of the 20th century that paved the way for mass-produced, affordable automobiles.

Even today, steel remains the material of choice for constructing the weight-bearing frames of motor vehicles. Although lighter and therefore more fuel-efficient alternatives exist, the car industry at large has been holding on to steel, mostly because of the high cost of production processes and raw mate-rials for the lighter alternatives.

It was not until 1994 that the first-ever mass-produced car frame system made entirely of aluminium hit the market. The car was the A8 by Audi, which had patented the technology a year before. Since then, other manufacturers have followed suit, but it was a steep climb from the days of wooden cars to a mass-produced alternative to steel as the main material for car frames.

Engine-powered carriages

When Gottlieb Daimler and Karl Benz experimented with their first automobiles in 1886, all their focus was on developing the combustion engines that powered the vehicles. The construction of the frame and chassis was left to engineers who specialized in the design and manufacture of horse carriages. After all, the functional requirements were the same whether the vehicle was powered by horse or engine, namely providing a safe and sturdy shell for passengers during transit.

Even the terminology for the different elements of the automotive body, such as "phaeton," "tonneau," "landaulet" and "wagonette," stems from the construction of horse coaches. So was the design: The first car test-driven by Benz around the streets of Mannheim in June 1886 ran on three wheels. Only in 1891 did the pioneer add an extra wheel, inspired by the success of Peugeot, Panhard and Levassor with their prototypes in France.

Due to the limited power of early combustion engines, wood proved the perfect frame material in terms of torsion and stiffness. The fact that all carriages had to be hand-crafted and assembled for each new car was not a problem at the time, as only the very rich could afford an automobile in the first place, keeping market demand low.

Steeling the show

At the dawn of the 20th century, wood was on its way out as the preferred manufacturing material. The introduction of steel sheets for outer panel design, together with the new drop-hammering manufactur-ing process, were the shape of things to come. While the inner, weight-bearing frames were still made of wood - sometimes reinforced with steel in "armoured wood" frames - the design options and mass production capabilities offered by steel had engineers exploring the possibility of manufacturing the automobile's frame of the same material.

This was made possible by the crucial meeting of two pioneers, namely steel manufacturer Arthur O. Smith from Milwaukee and automobile visionary Henry Ford. While Smith's company had created the world's first press-steel automobile frame in 1900 and had begun delivering it to Cadillac in 1903, it was Ford who was to take the entire automotive industry to the next level with his assembly line.

In 1906, Ford ordered 10,000 steel automobile frames from Smith and when he unveiled the legen-dary Ford Model T two years later, he made history as the man "who put America on wheels." Steel frames and an innovator had provided the world with the first mass-produced, affordable automobile. Within four years, Smith had become North America's largest frame manufacturer. By 1914, all-steel cars, such as the Dodge Brothers' vehicle that sold thousands of units, had become the norm.

Costly experiments

While steel remained the frame material of choice for the workingman's car, racing car engineers in their quest for a lighter and faster vehicle were scoping out alternatives early on. European car build-ers including Ferrari, Bugatti and Aston began using aluminium in the 1920s and 1930s on limited production runs. Innovation came to a standstill during World War II, however, when car-manufacturing plants were converted to support the war effort.

In the aftermath of the war, steel became a scarce commodity, especially in Europe, and car manufac-turers began to introduce lighter alternatives such as aluminium alloys and composite materials into car design. However, this was only in the body panelling, transmission and other components; in the frame, steel remained the only option.

Aluminium makes a stand

Two major obstacles stood in the way of aluminium becoming established as frame material. First, the cost of aluminium by weight is five times that of steel. Second, to reach the necessary stability and torsion stiffness, aluminium frames need special construction and assembly methods - also at a higher cost for manufacturers. Therefore the mass-production of an aluminium-frame car not only re-quires heavy investments in research and development, but also in new production facilities.

When Audi introduced its aluminium space-frame design at an industry convention in 1993, it was carried onstage by four tradeshow hostesses to demonstrate its lightness. At the same time, the Ger-man car manufacturer had also stepped up its ability to make the switch from steel to aluminium by creating the Audi Aluminium Competence Centre and manufacturing site.

Compared to steel, the technology affords better fuel efficiency, better handling and increased crash safety. Over the years, other automotive companies have followed suit by offering aluminium-framed cars, including Ferrari, Plymouth, Rolls Royce and Honda.

The technology currently remains limited to medium- to large-sized vehicles at a higher price point and has yet to find its way into budget automobiles. However, experts believe that increased production capabilities and lower costs of raw materials - together with more rigid legislation regarding fuel ec-onomy and recycling targets - might soon make aluminium the primary material in auto frame and body design.

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