a. Description

4V - Parallel
Sheet Metal


The Artifacts of R. Buckminster Fuller:
A Comprehensive Collection of his
Designs and Drawings,
James Ward, Ed.,
Garland, New York,

The lower half of this sheet-metal dome is of parallel “Truncatable” sections, although the upper half conforms to a “Triacon” grid. The “Triacon” grid was developed by Duncan Stuart during the early fifties, and structures based on this grid are theoretically more stable, as the constituent panels conform to the thirty -one great circles. With the use of this grid, one has the smallest discrepancy in the sizes of individual panels. By contrast, the “Truncatable” grid is necessary to ensure that a dome touches the ground on the points of evenly spaced triangular sections of equal size. Although this sheet-metal structure provides a clear illustration of the “Triacon-Truncatable” combination, the most famous example of this structure is the United States pavilion for expo ‘67, the lower third of which is composed of Truncatable sections. 

Fuller, R. Buckminster, The artifacts of R. Buckminster Fuller: a comprehensive collection of his designs and drawings, 
James Ward, ed., Garland, New York, 1984

This dome produces an oriented interior space. its envelope is composed
of surfaces whose scale and degree of discontinuity is regular.

The degree of repetition in the relationship between the part to its
whole is also regular.