Mannen-Dokei

NOTE:  The description of the Mannen Dokei in this web strand has intentionally been kept brief as numerous other dedicated books and web strands, including those of the Toshiba International Federation, are able to give far better justice to this outstanding clock.

The Mannen-Dokei (literally Ten-Thousand Year Self-ringing Bell), was a Wadokei designed and built by the Japanese inventor Hisashige Tanaka in 1851. It was designated as an Important Cultural Property by the Japanese government.

The clock is driven by springs and once it is fully wound, it was reputed to run for one year without another winding. It can show the time in 7 ways – Mean Time, Temporal Time, Day of the Week and Month, Moon phase, amongst other indications. It also has a planetarium on top showing the transition of the Sun and Moon with the seasons. It consists of more than 1,000 parts to realize these complex functions, and it is said that Tanaka made all the parts by himself with simple tools such as files and saws. It took more than three years for him to finish the assembly.

In 2004 the Japanese government funded a project aimed at making a copy of this clock. More than 100 engineers joined the project and it took more than six months with the latest industrial technologies. However, even then it was not possible to make exact copies of some parts, such as the brass metal plate used as its spring.

The ‘mannen jimei-sho’ remained the property of the Tanaka family, and it can be said that it eventually settled at the place most closely associated with it. The Wadokei is now located in the National Museum of Nature and Science in Tokyo.  A replica can also be seen in the Toshiba Museum, Kawasawa.