和時計における自動割駒式文字盤機構とその幾何学的誤差
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概要
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In July 2006, one of the authors, Okada, got an octagonal type Japanese table clock signed Masatoshi Miyake which has automatical wari-koma dial adopted to Japanese temporal hour through a year. We have already reported this Japanese clock in the previous report. However, we could not judge whether its number of annual gear teeth is 72 or 73 only from photograghs of the clock. At this time, we disassembled and investigated the another same type Japanese table clock and confirmed that the number of annual gear teeth is 73. Therefore, it was understood that the mechanism of this automatical wari-koma dial of the clock had been calculated and designed as 365 days a year. In addition, we tried to interpret the basic principle of the automatical wari-koma dial mechanism, which has an elliptic plate with radical slits and spoke shaped arms for driving wari-komas, and calculated the geometrical error margin which is included in the mechanism. From the culculation for the octagonal type Japanese table clock, it has been understood that the mechanical error at the mut-tsu of Japanese hour reaches 1.137 degrees at the maximum but that at the others of Japaese hours are very small. As a result, we were able to conclude that among the Japanese clocks with the automatc wari-koma dial investigated in the previous report, the bracket clock made by Shokichi Miyake was the oldest, the octagonal type table clock with no signature, the octagonal type table clock made by Masatoshi Miyake and the bracket clock introduced by M. E. James in Journal Suisse d'Horlogerie were newer, and the hanging clock made by Tadayuki Iwano was newest.
- 国立科学博物館の論文
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