Allan Bromley (historian) - Antikythera Mechanism

Antikythera Mechanism

Bromley, together with Sydney clockmaker Frank Percival, built a partial reconstruction of the Antikythera mechanism, one of the oldest (surviving) geared mechanisms known.

Professor Bromley took up the mystery of the computer where Price left off. He tested Price's theory of how the device worked by building a model of the main gear train with Meccano parts. He found that the mechanism was unworkable.
Professor Bromley says that he had an advantage that Professor Price did not have - he worked on the research in very close association with Mr Percival, a retired engineer and expert clock-maker in his spare time. Professor Price did not work closely with a mechanical-minded person.
The Bromley-Percival solution was to improve the mechanics of the device by altering the function of the handle which turned the gears so that one complete turn could represent one day, the most obvious of all astronomical phenomena.
Professor Bromley used the same arrangement of parts as Professor Price but had to conjecture that there were other gears and, as if it were meant to be, there was a gap in the mechanism in just the place where he wanted to put them
Another major discovery by professor Bromley concerned one whole train of gearing which had puzzled professor Price who could find no purpose for it. Professor Price guessed that it might have operated a four-year cycle on the device. Price had an assistant count the number of teeth on this gear train and was told it had 15 and 63 respectively. His response, possibly with modern gearing too much in mind, was to say that these numbers were too difficult to work with and must have actually been 16 and 64.
Professor Bromley decided he would see what happen if he worked with the original estimate of 15 and 63 gear teeth. If those were correct figures, he realised, the cycle of this gear train would have been 4 1/2 years. Four time 4 1/2 years is 18 and this happens to be the cycle of eclipses - which repeat every 18 years.
With this gearing the model worked. As the handle is turned, the pointer moves into a new square for each new moon - that is, one square shown on one of the dials of the device represents one month. In 223 months, or 18 years, one can see the complete cycle. —The University of Sydney News, 29 March 1988, p.39