Analog Computing Component - Integrator (Five-Inch Disc)

Instruments for finding the area bounded by curved lines (integrators) date from the nineteenth century. This twentieth century example is based on a mechanism invented by British engineer James Thomson and used by his brother William (later Lord Kelvin) in constructing the first harmonic analyzer in 1876. The object shows modifications and refinements made by the American inventor Hannibal Ford to assure high accuracy and durability. It has two stacked balls, held by stiff springs, between a disk and cylinder, each made of hard steel. The balls are held in place by pairs of small rollers in a carriage. This design permitted the carriage to move even when the disk was not moving, a feature that is necessary when integrating with respect to a variable other than time. From about 1915 into the 1940s, Ford's integrators were used by the U. S. Navy in devices for aiming guns on ships.

For further background and references, see 1982.0751.07.

References:

A. Ben Clymer, "The Mechanical Analog Computers of Hannibal Ford and William Newell," Annals of the History of Computing, 15, #2, 1993, 19-34.

K.C. Epstein, Analog Superpowers: How Twentieth Century Technology Theft Built the National Security State, Chicago and London: University of Chicago Press, 2024.

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