The Rolling Ball Web
An Online Compendium of
Rolling Ball Sculptures, Clocks, Etc.
By David M. MacMillan et. al.
W. Daniel Hillis has designed an improved "Congreve-style" rolling ball clock which employs cycloidal tracks. Hillis is a computer pioneer whose work has included the Connection Machine massivly parallel processing computer. At the age of 12, he constructed a computer out of plywood and scrap which could play tic-tac-toe; in college, he built another tic-tac-toe computer out of Tinkertoy® components. His work and interests are by no means limited to computer technology, however. More recently, he has created a foundation, The Long Now Foundation, for the purpose of building a monumental clock designed to run for 10,000 years. Hillis is a Vice President at Walt Disney Imagineering, and a Disney Fellow.
Several papers by Hillis are available from
The Long Now Foundation, at:
http://www.longnow.org/download.html
An extensive article on Hillis appeared in Wired 6.05 (May 1998): 116-123, 167-168, 170, 172, 174. His rolling ball clock is mentioned on page 122 of this article. The illustration accompanying it is, however, of a conventional Congreve clock.
The advantage of cycloidal tracks in a rolling ball clock of any type is that the cycloid is an isochronous curve. A ball rolling down a cycloidal track will always take the same time to reach the bottom, regardless of its starting position.
I believe that this was first demonstrated by Huygens in his work on the ideal, cycloidal, path for a pendulum. Cycloidal tracks were common in 18th century scientific demonstration apparatus.
The photos below illustrate three prototype tracks created for Hillis' clock. The Wired article indicates that some or all of the tracks for Hillis' clock were fabricated by the shops of Walt Disney Imagineering. The tracks are machined out of solid aluminum, and at least one of them is approximately 1' x 2'. The ball is tungsten.
These photos are reproduced through the courtesy of W. Daniel Hillis and The Long Now Foundation, http://www.longnow.org/
Designed by W. Daniel Hillis of The Long Now Foundation.
Photographs copyright © 1998 by W. Daniel Hillis and The Long Now Foundation. The text and encoding of this document are copyright © 1998 by David M. MacMillan.
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