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Skeleton-like automotive manufacturing innovations, part 1: The Maserati Birdcage

By Rain Noe - September 14, 2010

in Object Culture

In the late 1950s, Maserati designer/engineer Giulio Alfieri came up with an innovative way to build a racecar: Instead of going with the "steel tub" construction of the time, he devised a crazy-looking trellis of interconnected tubes shaped into a frame.

Alfieri's car was called the Tipo 60 (later Tipo 61), and as explained by Supercars.net,

Opting out of using a tub chassis made from sheet steel or aluminum, Alfieri's birdcage instead used small segmented [steel] tubes [with diameters ranging from 10 to 15mm]. Over 200 individual pieces were used in the design. The resulting chassis looked like a complex network, almost always described as a Birdcage.

Two challenges arose from the Birdcage frame. These included maintaining a high level of welding throughout the design which had hundreds of connection points and calculating the required elasticity as not to break the welds during stress. Remarkably, the chassis only weighed 80 lbs (36 kgs).

Calculating the stress points in a pre-CAD error must have been part guesswork and part nightmare, but somehow Alfieri got it together. The resultant super-light car was like nothing else on the track and proved to be blazingly fast; unfortunately it was plagued by mechanical problems unrelated to the body, and the innovative structure was overshadowed by a reputation for engine failure.

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Spiv

14 years ago

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I'm not sure who came up with it first, but my lotus seven is built much the same way (Chapman's origional design was in 1956, but there are many precursor cars in the lotus racing lineup). Finite element analysis is an old art, but new tools make for great yields. For example the original frame is about 100-140lbs ("production" model, no two are really alike) and 1200lbs/degree of flex. With modern engineering tools (ANSYS) we were able to modify the design to 1900lbs/degree and 70lbs, including an independent rear suspension. The main runners are 1" 16 gauge box steel, most everything else is smaller.

Chapman got around welding issues by having the entire frame brazed, which is does less thermal stress to the metal. I cheated and used gussets, but I had weight to spare.
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Fred Schechter

14 years ago

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In 1995 MIT students raced a solar car with a bird cage chassis inside a carbon shell.
Kicked everyone's butt from the start of the race in Indianapolis,, to Golden Colorado.
The thing was awesome, and ridiculously robust.
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