Aus:
Tony Hadland, Hans-Erhard Lessing. Bicycle design: an illustrated history. Cambridge (Mass.): MIT Press; 2014.
In the earliest days of the pneumatic-tired safety bicycle, aluminum was tried as a frame material. “Many attempts have been made to employ it in cycle construction,” Archibald Sharp wrote (1896, 287), but “no alloy containing a large percentage of aluminium, and therefore very light, has been found to combine the strength and ductility necessary for it to compare favorably with steel.”
The St. Louis Refrigerator and Wooden Gutter Company showed aluminum bicycles in New York in 1895 and claimed to have made racing versions weighing about 16 pounds. Three years later, the British firm Humber introduced a 22-pound diamond-frame bike built of aluminum tubes mechanically clamped together with steel lugs. This necessitated inserting steel liners in the ends of the frame tubes. The Humber machines weren’t durable and were soon discontinued.
Aluminum only has about one-third the stiffness (modulus of elasticity) of steel. To achieve stiffness and maintain low weight, the diameter of the tubing has to be increased. But for many decades the few bicycle makers who built aluminum frames typically used tubing similar in diameter to that in steel frames. Another drawback of aluminum is that, unlike steel, it has no fixed fatigue limit and can fail under fairly low stress with enough repetitions. Owing to aluminum’s deficiencies in stiffness and resistance to fatigue, frames made of it were inferior to steel frames, even if they were somewhat lighter.
A few French makers produced beautiful aluminum frames, such as Caminade’s Caminargents of the late 1930s. In 1948, the British firms Holdsworth and Hobbs both exhibited all-welded aluminum-alloy frames, but they don’t seem to have manufactured them in large quantities. In 1949, Raleigh exhibited a 16-pound bicycle of similar construction. It got a lot of publicity, but wasn’t series produced.
In 1967, the British Aluminium Company (BACo) undertook research for its sister company Raleigh. (At the time, both were owned by Tube Investments.) BACo made a study of past aluminum racing bicycle frames and found that all had been based on the conventional triangulated tubular steel design. It concluded that the few commercially successful machines had had mechanical joints with tapers and/or clamps, and that, used in this way, aluminum didn’t offer advantages over steel as a frame material. BACo and Raleigh later built an experimental aluminum monocoque prototype; series production did not follow. An alternative approach to monocoque aluminum construction was demonstrated in 1986 by the Italian designers Fabrizio Carola and Carla Matessi. Their Aluetta commuter bicycle (Italian patent 19,748A of 1986) had a frame made up of two half-shells of honeycomb-core aluminum. In the late 1980s, Raleigh America made lightweight frames of aluminum but stayed with the lugged diamond frame design and used the Technium system of adhesive bonding.
In the early 1990s, TIG-welded aluminum frames with large-diameter tubes, mostly made in the Far East, became widely available and fashionable, having been pioneered in the United States by Cannondale and Klein a decade earlier. TIG welding was found to work well if a much larger fillet was used at the joint than would be used with steel. Most TIG-welded aluminum joints looked a little crude, but, as with steel, improving the appearance was a manual job that cost time and money.
Few cycle makers in the West were able to manufacture aluminum frames as cheaply as their competitors in the Far East, and this hastened the demise of frame making in North America and Europe. The Heinz Kettler company in Germany, however, has produced TIG-welded aluminum city and trekking bicycles since 1977.
Because aluminum has much poorer fatigue performance than steel, the cheaper aluminum frames were overbuilt to avoid warranty and liability problems. Such frames were often therefore no lighter than steel ones.
