The dynamics and limits on the scaling of a flexible kinetic sculpture

Abstract

Highly flexible structures may be scaled up by different criteria that lead to different degrees of structural integrity as the scale increases. This paper first explores the effects of different scaling rules, focusing in particular on a double-size version of the Len Lye kinetic sculpture Blade, whose aesthetic performance characteristics must be preserved as the size is increased. Stresses in the sculpture increase, reaching first an economic limit beyond which frequent fatigue failure makes the sculpture too costly to operate. As the scale further increases, a size is reached where the sculpture will collapse. A dimensional parameter for comparing the values of the life to failure for different construction materials is also developed. The second part of the paper summarizes the results of different analytical approaches to the dynamics of Blade, both with and without the inclusion of an axial acceleration load due to gravity. The results of analyses are found to be in good agreement with experimental data. The paper closes by discussing some of the design implications of implementing the drive system for a double-size version of Blade that has been built and is now on public display.