Wednesday, July 4, 2007

Geodesic domes

A geodesic dome is a fractional part of a geodesic sphere, composed of a complex network of triangles. The archetypal geodesic sphere is made up of twenty curved triangles, each corresponding to one facet of the icosahedron, a twenty-faceted solid geometrical figure. The more complex the network (that is, the smaller the triangles), the more closely the form approximates a true sphere. Using triangles of varying size, a sphere can be symmetrically divided by thirty-one great circles (the largest that can be traced on the surface of a sphere). The triangles form a self-bracing framework that develops structural strength with a minimum amount of material. Thus, the geodesic dome combines the sphere (the most efficient container of volume per unit of surface area) with the polyhedron, which has the greatest strength per unit of mass. Developed in the first half of the twentieth century, it provided a completely new way of building light, transportable structures with efficient thermal and wind-resisting properties. For example, the aluminum-and-Teflon geodesic “Pillow Dome” designed by Jay Baldwin is a permanent insulated structure that can resist 135-mph (216-kph) winds and carry tons of snow; it weighs only 0.5 pound per square foot (2.43 kilograms per square meter).

The world’s first geodesic dome was assembled on the roof of the Carl Zeiss Optical Works in Jena, Germany, in 1922. The 52-foot-diameter (16-meter) structure, designed by Zeiss’s chief designer, Dr. Walter Bauersfeld, was necessary to test what he no doubt regarded as his more important invention, the planetarium projector. He built a complex skeleton of 3,480 light iron rods, accurate in length to 0.002 inch (0.05 millimeter) to form a highly subdivided icosahedron. Twenty-five years later, the American genius Richard Buckminster Fuller (1895–1983) independently derived his geodesic dome (patented 29 June 1954) from general principles, and he is generally credited with the invention of the form.

Fuller was deeply interested in the issues of shelter and housing, and by the end of World War II he had developed industrialized prototypes of the now-famous Dymaxion Houses, which he built for the Beech Aircraft Company in Wichita, Kansas. He then moved his attention to the construction of domes, because he believed that they reflected “nature’s coordinate system” and therefore provided the optimally efficient way to enclose space. Through much of the 1940s he worked on small models of spheres or part-spheres made up of intersecting great circles, just as Bauersfeld had done. Fuller coined the name “geodesic dome” because the arcs of great circles are known as geodesics (Greek, “earth dividing”). In 1948 he seized the chance to take part in the summer school of Black Mountain College in North Carolina, taking with him the material needed to build a large-scale geodesic dome. Applying engineering strategy that he dubbed “tensegrity” (a contraction of “tensional integrity”)—Fuller loved to invent words, too—he devised a system that depended on a continuous tension element rather than “discontinuous local compression members.” He soon built a number of geodesic domes.

In 1953, Fuller built his first commercial dome, for the Ford Motor Company, and it was followed in 1954 by a 42-foot-diameter (12.8-meter) cardboard shelter in his exhibit at the Milan Triennale in Italy; it was awarded the Grand Prize. A few large-scale applications included the Union Tank Car dome (1958). In I960 Fuller proposed a 2-mile-wide (3.2-kilometer), 200-foot-high (60-meter), temperature-controlled geodesic dome to enclose part of New York’s Manhattan Island, claiming that the savings of snow-removal costs would amortize the cost within 10 years. On a more practical level, his domes covered military projects including sensitive radar installations (“radomes”), emergency shelters, and mobile housing. They were and are also used for weather stations, industrial workshops, and greenhouses. One was even proposed for a cinema, in collaboration with the architect Frank Lloyd Wright.

Fuller’s magnum opus is the former United States Pavilion at Expo 67 in Montreal, Canada, designed with Shoji Sadao. The huge, lacy dome, framed with steel pipes enclosing 1,900 molded acrylic panels, has a diameter of 250 feet (76.5 meters) and stands 200 feet (60 meters) high, “weightless against the sky.” It has been adapted by Environment Canada and the city of Montreal and is now known as the Biosphere, an environmental water-monitoring center on the St. Lawrence River.

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