Two Hundred Years of Analyzing Roberval's Balance

Abstract

Roberval’s balance, a type of weighing scale, was proposed by Giles Roberval in 1669, and it was soon regarded as a paradox because it appeared to violate the laws of statics.  Beginning in 1695 and over a nearly 200-year period, many analysts attempted to explain the paradox using a variety of methods, many of them succeeding.  Of these, a forgotten paper by Antoine Parent in 1713 is the most significant in that it employed what was later to be known as the free-body method, the foundation of modern structural analysis.  Around the late 1800’s, the focus shifted to making the necessary assessments so that the Roberval balance could become a practical device.  These analyses were also conducted using the free-body method.   Documenting the history of Roberval’s balance is like exploring the early development of the field of structural analysis.  It also demonstrates how structural analysis can be used not only to gain basic understanding of a novel machine design but to provide a path to commercial application.

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