Mechanism of "Man-nen dokei", a Historic Perpetual Chronometer (1st Report, Celestial Globe and Japanese Traditional Clock)

Abstract

The “Man-nen dokei”, that literally means a clock that works for ten thousand years, is a historic perpetual chronometer that was built in 1851 by Hisashige Tanaka, who founded the predecessor of Toshiba Corporation. It has six multifunctional clock faces and is crowned with a celestial globe that shows the positions of the sun and the moon. It is said that “Man-nen dokei” is one of the best works in Japanese traditional clock. Recently, it has been disassembled and restored in a national project as a one of the most original symbols of Japanese manufacture, so we investigated the mechanism of the “Man-nen dokei” in cooperation with the project. This paper shows the mechanism of the celestial globe and the Japanese traditional clock which is the main part of the six clock faces. Especially, we focus on (1) the mechanism for simulating the motion of the sun and the moon throughout the year in the celestial globe and (2) the mechanism for the movement of the “warigoma”, the ten square pieces, which show the time in the old Japanese temporal hour system.