著者

佐々木 勝浩

出版者

国立科学博物館

雑誌

Bulletin of the National Science Museum. Series E, Physical sciences & engineering (ISSN:03878511)

巻号頁・発行日

vol.4, pp.31-40, 1981

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The Foucault's Pendulum in the National Science Museum was replaced by a new improved model in January-April 1981. Before that, some theoretical investigation and experiments, such as measurements of the damping rate and elliptical motion were carried out. We have compared two kinds of suspension. One is the "bolt type" in which the upper end of the wire is simply fixed by a bolt. Another is the "knife edge type" in which the wire is suspended by a ring equipped with double knife edges. The measurements of both the damping rate and the elliptical motion of the pendulum showed that the knife edge type is slightly better. In consideration of the result of the experiments, the bob and the wire changed in size and material, and the suspension ring was improved. The length of the new pendulum is 1950 cm, about 50 cm than before, and the new bob was made of stainless steel instead of lead. Stainless steel is less dense than lead but it is more suitable for the precise shaping and fine finish. The new bob is 23 cm in diameter, 3 cm longer than the old one. The writer designed a new suspension ring to increase the rigidity as shown in Figure 4. The formance of new pendulum is almost satisfactory but no remarkable decrease of damping rate and elliptical motion were observed.

著者

佐々木 勝浩

出版者

国立科学博物館

雑誌

Bulletin of the National Science Museum. Series E, Physical sciences & engineering (ISSN:03878511)

巻号頁・発行日

vol.26, pp.21-31, 2003-12

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Rokoku is the water clock used in ancient China, and the origin goes back to thousands years ago. The multistage type Rokoku which has several vessels as the typical form can be mentioned, and the first vessels is for water supply, the middle vessels are for control of flow rate of water, and the last vessel is for time measurement. The last vessel has a float with the time scale which we can read and know time. Although researches of J. Needham or D. Price were known, the sufficient interpretation about the accuracy and the usage of Rokoku as a clock was not carried out. In this research, first the physical character of a single vessel was observed, subsequently the change of the water level of each vessel was calculated numerically, and then the static and dynamic characteristics of Rokoku were examined. Consequently, in multistage type Rokoku it was able to confirm that the vessels play an important role in controle of a water flow, a fixed quantity of water is supplied periodically when actual using, for example 2 times everyday (in the morning and in the evening), and in the case of that sufficient accuracy is secured, etc.

著者

佐々木 勝浩 渡辺 誠

出版者

国立科学博物館

雑誌

Bulletin of the National Science Museum. Series E, Physical sciences & engineering (ISSN:03878511)

巻号頁・発行日

vol.19, pp.17-42, 1996

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The large Pillar clock with detailed hour scale 'SEIMITSU-SHAKUDOKEI' has been exhibited at the National Science Museum on loan from Mr. Shingo Takabayashi, on the scale of which has quite rare hour system, 13 deviding hour system, including special hour 'YO-JI', chinese character 'YO(餘)' of which means the remainder. In the historical investigations about astronmy in Ishikawa and Toyama prefecture, Watanabe, one of the authors, found the fact that the 13 deviding hour system was used in the old fief of Kage in Edo period. Also Watanabe and others found the astronomical clock 'SUIYOU-KYUGI' at the 'KOJU-BUNKO' library in Sinminato City. In examining the relation between the 'SEIMITSU-SHAKUDOKEI' and the 'SUIYOU-KYUGI', the evolution of hour system including rare hour 'YO-JI' in the old fief of Kaga was known in details. We report about this special hour system and discuss about the meaning of special hour 'YO-JI'.