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The 14th IFToMM World Congress, Taipei, Taiwan, October 25-30, 2015 DOI Number: 10.6567/IFToMM.14TH.WC.OS6.007 An Introduction to the Gravity-driven Clocks in the Forbidden City Y.-H. Chen 1 National Cheng Kung University Tainan, Taiwan K.-H. Hsiao 2 National S&T Museum Kaohsiung, Taiwan T.-Y. Lin3 Southern Taiwan University of S&T Tainan, Taiwan H.-S. Yan4 National Cheng Kung University Tainan, Taiwan Abstract— Ancient timepieces are combinative products of science and technology, and they were communicated to China through importation during the 17 to 19 centuries. Clocks collected by Chinese emperors are elegant works and show the highest manufacture level. Regarding the gravity-driven clocks, the methods to apply gravity as a power source are ingenious. The development of power sources in timepieces and the communication of technology from Europe to China are introduced briefly. Four typical gravitydriven clocks are presented and divided into two types, driven by an outer force and by its own weight. Furthermore, structural analyses regarding the mechanisms of typical gravity-driven clocks are provided. Keywords: Clocks and watches, Forbidden City, Structural analysis, History of machinery I. Introduction The Forbidden City in Beijing took a part of imperial palace from the Ming Dynasty (1368-1644) to the end of Qing Dynasty (1644-1911). It was the residence for emperors, and the political center of ancient Chinese government. In 1925, the role of Forbidden City was changed from palace to museum. Emperors’ collections became exhibitions, including jewels, calligraphies, paintings, and timepieces. These clocks and watches reflect the development of timepieces and the highest manufacture levels of the period from the 17 to 19 centuries. Some timepieces came from countries in Europe, and others were made in China. The former ones were contributed by Jesuit missionaries, purchased by the government, or ordered by the emperors; and the latter ones were manufactured by the clock workshop in the palace, with over one hundred artisans under guidance of missionaries worked in. Timekeepers collected by emperors were made of expensive material, resplendent adornment, and exquisite mechanical structure. Not only the ancient Europe artistic style is shown, but also Chinese cultural elements are combined, Fig. 1 [1]. Hundreds years passing, people are still amazed by these ingenious antique timepieces. These clocks and watches are evidence to provide communication between China and Western countries in that period [1, 2]. Fig. 1. A Chinese style clock [1] These gravity-driven clocks were made in the palace and France. This paper focuses on the historical and mechanical studies of the gravity-driven clocks in the Forbidden City. In what follows, the development of power source applied to timepieces is briefly introduced. Then, the communication of the technology and science in ancient China during the Qing Dynasty is expressed. Finally, the classification and the structural analysis of typical gravity-driven clocks are presented. II. Power Sources in Mechanical Clocks People have got sense of “time” since thousands years ago. Many kinds of timekeepers such as gnomons, sundials, clepsydras, sandglass, and mechanical timepieces were invented. Mechanical clock is one of the most important inventions that greatly affect the development of science and technology in the history of mechanical inventions. Figure 2 shows the evolution of power source in mechanical clocks, including water, gravity, and coiled spring. Thousands of mechanical timepieces were collected in the Forbidden City. Coiled spring is the main power source of these timepieces, but a small number of clocks are driven by gravity of weight [3]. 1 [email protected] 2 [email protected] 3 [email protected] 4 [email protected] Fig. 2. Power sources in ancient timepieces In the 11th century, a water-driven astronomical tower clock was built in ancient China. Two spherical instruments in the upper floors show celestial phenomena, and the devices at the base floor are power and time-telling systems, Fig. 3 [4]. Water trickles out of the tank and constantly flows into a bucket attached to the water wheel. To make the wheel revolute in a uniform speed, a set of steelyardclepsydra device was applied. Unfortunately, the exquisite work was destroyed in the end of the 12th century, and the achievement was not inherited and developed. Although coiled spring had been applied to drive machines since the 14th century, it was hard to power timepiece because of its various force. The tighter a spring is wound, the larger force is released. To the 15th century, a regulated device, fusee, was invented. It makes output torque of the coiled spring uniformly. Clocks driven by coiled spring and adjusted by fusee were created, Fig. 5. Obviously, the size and weight of spring-driven clock is smaller than the former types, so portable timepieces were developed since the 16th century [6]. Fig. 5. A spring-driven clock [8] III. Communication of Technology and Science through Timepieces in Qing Dynasty Fig. 3. Su-Song’s water-driven clock in ancient China [4] During the period of 13 to 14 centuries, with the invention of escapement device, the mechanical clocks driven by weight were presented in Europe. It is said that the first gravity-driven mechanical clock was built at a cathedral in British [5]. Figure 4 shows a similar movement of clock tower. The power source coming from a device consisting of a heavy weight tied to a rope activates gears through a ropewrapping pulley. The earliest gravity-driven clock tells time by striking since there is neither dial nor hands in the clock. Many years later, hour hand and minimum hand were attached step by step. Weight is a good power source for clock because the heft of each weight is fixed and a stable force is applied to the movement. Nevertheless, gravitydriven clocks were not only heavy but huge, and were usually set at churches, towers, or city halls in that period. Until the 15th century, the dimension of gravity-driven clocks was reduced for domestic use and people continued to make timepiece portable [5, 6]. Fig. 4. A gravity-driven clock [7] Jesuit missionaries went to China from Europe after the Age of Discovery. They not only disseminated the religion, but also brought Western science and technology. Since the Italian missionary Matteo Ricci ( 利 瑪 竇 , 1552-1610) introduced mechanical chime clocks to China in 1601, a large numbers of timepieces were sent to the Forbidden City as gifts, tribute, or purchases. Chinese Emperors were interested in Western clocks, watched, mechanical toys, and instruments. In order to maintain, manufacture, and refit timepieces, Kangxi Emperor (康熙, 1662-1722) of Qing Dynasty set a clock workshop in the palace in 1677. Foreigner missionaries, technical personnel, and local artisans were hired. According to the archives of imperial workshop, emperors gave detailed instructions on form and manufacturing process, including how to disassemble, combine, and refit. Also, when craftsmen finished the madeto-order clock, emperors checked their work and provided comments for modifying. Chinese style such as architecture, decoration, symbol of myths, and folk ritual is shown in these timepieces. Except for the workshop in the palace, timepiece industry was developed in coastal cities such as Guangzhou (廣州) and Suzhou (蘇州). Most importation from Europe was through the trading ports in these areas. The timepiece industry in China started in the 17th century, reached its height during the period of Qianlong Emperor (乾隆, 1711-1799), and decayed in the 19th century because of the decline of the Qing Dynasty [1, 2, 9-15]. The clock brought by Matteo Ricci was driven by weight and regulated by foliot and verge escapement, Fig. 6. It did not work accurately that the error was more than one quarter per day. In 1658, most imported clocks were with pendulum and cycloidal cheeks, and the error is less than 1 minute per day, Fig. 7. Clepsydra, the most important device for keeping time in ancient China before the 17th century, was also erred in 20 seconds to 1 minute a day. Until 1681, the timepieces with coiled spring and balance wheel were imported from the West, and the error was just a few seconds per week. That is to say, the clepsydra was replaced progressively when the accuracy of mechanical timepieces improved. Clocks were regarded as elegant art work, rather than instrument, by Chinese emperors in the early 17th century [16, 17]. 滴水, 水乃漸減, 遂以為輪之運轉, 是水由重而漸減為 輕也; 自鳴鐘以鐵為捲, 置銅鼓之中, 捩之使屈其力, 力由屈求伸, 亦由重而減為輕也。…綜其理, 皆由重以 減輕, 故曰重學也。[19] ) Even though we did not read the definite physical principle in the article, it shows that contemporary Chinese got a little sense of potential energy from the power source of timekeeper [14, 15]. Some series and journals about science knowledge were published in China during 19 century. Chinese scholars and foreign missionaries not only translated European literature, but also selected to compile series, including the book “Shi Wu Tong Kao” (時務通考, Collected Edition of Western Science Continued) and the text of “Zhong Xue Qian Shuo” (重學淺說, Popular Treatise on Mechanics). Subjects such as machinery, force, gravity, and kinematics were introduced. However, the communication of mechanics knowledge in Qing Dynasty is just on conceptual level, and the relation between theory and its application is not reflected [20]. IV. Classification of Gravity-driven Clocks Fig. 6. Gravity-driven clock with the verge escapement [17] Within the collections of the Forbidden City, the number of gravity-driven clocks is much less than that of springdriven. Nevertheless, the way that a coiled spring drives the clock is the same, but the methods to apply gravity as a power source are various [3]. Gravity-driven clocks in the Forbidden City can be classified into two types, powered by outer forces and by their own weights, and this classification is depended on whether there is a relative motion between the movement and the weight, Fig. 8. The adding weights are attached to the movements of the gravity-driven clocks. If the movement is fixed but the weight is falling, there is a relative motion between the two parts, and it is driven by an outer force, Fig. 9(a). If the movement and the weight are fixed together, there is no relative motion between the two parts, so it is driven by its own weight, as shown in Fig. 9(b). Each type of gravity-driven clocks is described in the following sections, along with four gravity-driven clocks collected in the Forbidden City as examples. Fig. 7. Huygens clock with a pendulum and cycloidal cheeks [18] Although Chinese could imitate the Western timepieces in the Qing Dynasty, most of contemporary people did not learn relevant science knowledge. Nevertheless, some people got sense about the physical principle through observing how clocks work and each component inside. For example, an article written by Juan Yuan (阮元, 1764-1849) told about mechanics as following: The water clock in ancient time works on the following principle: First, people fill water into a leaking tank. As the water leaks, the quantity of the water in the tank decreases and becomes the motive power of the clock. As for the chime clock in recent days, there is a coiled spring in its bronze barrel. When one turns the coiled spring, it bends, gradually stretches, and therefore generates motive power. Both methods display an application of energy consumption, which falls in the field of mechanics. (古漏壺盛水, 因漏 Fig. 8. Classification of gravity-driven clocks in the Forbidden City (a) (b) Fig. 9. Relative motion between the movement and the adding weight A. Clocks driven by an outer force As shown in Fig. 8, an outer force driven clock is divided into two types, hanging weight and rolling balls. The detail of each type is as follows: A.1 Clocks with a hanging weight The size of a clock with a hanging weight is usually bigger than others [5]. Figure 10(a) shows the chime clock on a sandalwood tower with carved floral patterns. As the largest timepiece collected in the Forbidden City, it is 585 cm tall and 262 cm in width and thickness, made in the clock workshop of the Forbidden City during Qianlong period (乾隆, 1736-1795) in the Qing Dynasty [1]. Figure 10(b) shows how the adding weight is attached to the movement. The power source is the gravity of a weight hanging by a rope or chain, and the other end of the rope/chain wraps a pulley. With the weight falling down, the pulley turns and transmits force through gear trains to the movement. The power-system is a mechanism with four members and four joints, including the frame (member 1, KF), a pulley with a pinion (member 2, KGU), a rope/chain (member 3, KR), and a gear attached to the movement (member 4, KG2). Since there is no relative motion between the pulley and the pinion, they are considered as the same member. The pulley with a pinion is connected to the frame, the gear, and the rope/chain with a revolute joint (JR), a gear joint (JG), and a wrapping joint (JW), respectively. The gear is connected to the frame with a revolute joint (JR). Figure 10(c) shows the structural sketch. A.2 Clocks with rolling balls A clock driven by steel balls is shown in Fig. 11(a). It is 53 cm tall, imported from France during the 19th century. A large wheel with 12 sections is behind the movement. A box contains 18 balls is on the clock, and a drawer is at the bottom for receiving the fallen balls. When 4 balls enter the divided parts on the wheel and make torque to the shaft, the clock starts working. With the wheel turning, a ball finishes half-circle turning and falls into the drawer at the bottom every 16 hours. At the same time, another rolling down ball enters the wheel from the box at the top story. The wheel driven by balls rotates clockwise and transmits torque to the movement through gears, Fig. 11(b). The users have to move balls from the bottom drawer to the top box when no ball left. It is the only one clock with rolling ball mechanism in the Forbidden City [2, 3]. The power-system is a mechanism with three members and three joints, including the frame (member 1, KF), a pinion with a wheel (member 2, KG1), and a gear attached to the movement (member 3, KG2). The pinion is connected to the frame and the gear with a revolute joint (JR) and a gear joint (JG), respectively. The gear is connected to the frame with a revolute joint (JR). Figure 11(c) shows the structural sketch. (a) External [1] (a) External [1] (b) Diagram of power-system (c) Structural sketch of power-system Fig. 11. Gilded copper clock with a rolling ball mechanism B. Clocks driven by its own weight There are two types of clocks that are driven by its own weight in the Forbidden City, Fig. 8. The detail of each type is as follows: B.1 Clocks with falling movement (b) Diagram of power-system (c) Structural sketch of power-system Fig. 10. Chime clock on tower with carved floral patterns The clock with falling movement was made in France in the 19th century. It is 53 cm tall, 30 cm wide and 20 cm thick, Fig. 12(a). The clock consists of four pillars with slots standing on the base, and pins on the casing of movement are in the slots. It makes the movement be slid up and down along pillars. A rack is fixed between pillars on the right side, and engaged with a gear connected to the movement, Fig. 12(b). The weight and the movement are fixed together. The clock is “winded” through raising the movement to the top of pillars every six days. When it falls down by gravity, the gear turns, transmits power to the movement and makes the clock work. The power-system is a mechanism with three members and three joints, including the frame (member 1, KF), a pinion with outer sleeve (member 2, KG1), and a gear (member 3, KG2). The movement remains plumb, so it is considered as the frame. The pinion is connected to the frame and the gear with a revolute joint (JR) and a gear joint (JG), respectively. The gear is connected to the frame with a revolute joint (JR). Figure 13(d) shows the structural sketch. The power-system is a mechanism with three members and three joints, including the frame with a rack (member 1, KF), a gear (member 2, KG), and a slider (member 3, KP). Since there is no relative motion between the rack and the frame, they are considered as the same member. The slider is connected to the frame and the gear with a sliding joint (JP) and a revolute joint (JR). The gear is connected to the frame with a gear joint (JG). Figure 12(c) shows the structural sketch. (a) External [1] (b) Inner [21] (a) External [1] (c) Diagram of power-system (d) Structural sketch of power-system Fig. 13. Gilled copper clock with a rolling sleeve (b) Diagram of power-system (c) Structural sketch of power-system Fig. 12. Cooper clock with a falling movement B.2 Clocks with rolling sleeve Figure 13(a) and (b) show a clock with rolling sleeve, with 13 cm in diameter and 9.5 cm in thickness. It was also imported from France in the 19th century. The clock is driven by its own weight through rolling down a 55 cm long and 10° sloping board. It is the combination of an outer sleeve and a movement fixed with weight. When the clock rolls down the board, a line from 6 to 12 o’clock on the dial attached to the movement remains plumb because of the weight. It takes 24 hours for the clock to roll down the board [21]. A gear attached to the outer sleeve and engages with another gear that is fixed with the movement. It transforms gravity potential energy of weight into power for driving the clock, Fig.13(c). V. Conclusions It is necessary to keep a stable and sustaining power source in timepieces. In the process of searching, many kinds of power sources were applied to drive timepieces, including water, gravity, and coiled spring. Timepieces become smaller and smaller with evolution of power sources, and the portable timekeepers, watches, were also invented. Mechanical timepieces not only changed people’s life, but influenced the development of science and technology. Importation is a way to communicate. When Jesuit missionaries brought science instruments and introduced Western technology in the 17th century, Chinese started timepiece industry at imitating and improved their products progressively. With Chinese emperors’ enthusiasms for Western timepieces, the most exclusive products were sent to the Forbidden City, and outstanding artisans were gathered in the imperial clock workshop during the Qing Dynasty. As the result, timepieces collected in the palace show the highest level of manufacturing during 17 to 19 centuries, and they cover all kinds of mechanical devices. Even though the number of gravity-driven clocks is much less than that of spring-driven in the Forbidden City, the ways to apply gravity are diversified. Hanging weight is a typical case to drive clock by gravity, therefore this type of clocks are familiar. Nevertheless, clocks with rolling balls, falling movement, and rolling sleeve are rare. They were imported from France during the 19 century, with artful designs and unique shapes. Nowadays, these clocks are not only elegant work of technology, but reflect the development of timepieces and the highest manufacture levels in that period. Acknowledgement The authors are grateful to the Ministry of Science and Technology (Taipei, Taiwan) under Grant MOST 103-2221E-006 -040 - for the financial support of this work. References [1] The Palace Museum (2008) Timepieces in the Collection of the Palace Museum: Classics of the Forbidden City (in Chinese), the Forbidden City publishing house, Beijing. 故宮博物院編,《故宮鐘錶》,紫禁城出版社,北京,2008 年。 [2] Guan XL (2007) Timepiece (in Chinese), the Forbidden City publishing house, Beijing. 關雪玲,《你應該知道的 200 件鐘錶》,紫禁城出版社,北 京,2007 年。 [3] Lu YZ, Ma YL (1991) The clocks without coiled spring (in Chinese), Forbidden City, No. 1, pp. 40. 陸燕貞、馬玉良,”不裝發條的鐘”,紫禁城,第 1 期,第 40 頁,1991 年。 [4] Lin TY (2001) A Systematic Reconstruction Design of Ancient Chinese Escapement Regulators (in Chinese), Ph.D. dissertation, Department of Mechanical Engineering, National Cheng Kung University, Tainan, Taiwan. 林聰益,古中國擒縱調速器之系統化復原設計,博士論文, 國立成功大學機械工程系,台南,2001 年。 [5] Falk D (2008) In Search of Time: Journeys along a Curious Dimension, Thomas Dunne Books, New York. [6] William JHA (2002) A brief history of clocks, Science American, No. 9, pp. 76-84. [7] Iron frame tower clock, The SEIKO Museum, Tokyo, Japan, http://museum.seiko.co.jp/en/collections/collect2.html [8] Thompson D, Peckham S (2005) Clocks, British Museum Press, London, pp. 64-65. [9] Lang XH, Qin XP (2002), Clocks and Watches of the Qing Dynasty: from the Collection in the Forbidden City, Foreign Languages Press, Beijing. 朗秀華、秦曉培,《清宮鐘錶集粹─北京故宮珍藏》,外文 出版社,北京,2002 年。 [10] Wang C, Qin SM, Qi HN (2008) Exploration of imperial clock workshop in Qing Dynasty (in Chinese), Journal of National Museum of China, No.2, pp.34-45. 王津、秦世明、亓昊楠,”清代御制钟表探微”,中國國家博 物館館刊,第 2 期,第 34-45 頁,2008 年。 [11] Chen ZW (1984) Successors of mechanical clock in Europe and development of modern timepiece industry in China (in Chinese), No. 1, pp. 179-183. 陳祖維,”歐洲機械鐘的傳人和中國近代鐘錶業的發展”,中 國科技史料,第 1 期,第 179-183 頁,1984 年。 [12] Zhang BC (1995) Successor and questions related to technology of European mechanical clocks during Ming and Qing period (in Chinese), Journal of Dialectics of Nature, Vol. 17, No. 2, pp.185193. 張柏春,”明清時期歐洲機械鐘錶技術的傳人及有關問題”, 自然辯證法通訊,第 17 卷,第 2 期,第 185-193 頁,1995 年。 [13] Yun LM (2000) Timepieces made in the clock workshop of palace during Qing Dynasty (in Chinese), Liang An Guan Xi, No. 11, pp. 62. 惲麗梅,”光陰似水物依舊─清宮做鐘處與自製鐘錶”,兩岸關 係,第 11 期,第 62 頁,2000 年。 [14] Li YR (2009) Clocks and Watches in Ming-Ching period (15821911) (in Chinese), Master’s thesis, Department of History, National Chengchi University, Taipei, Taiwan, pp. 9-37. 李侑儒,明清的鐘錶(1582-1911) ,碩士論文,國立政治大學 歷史系,台北,第 9-37 頁,2009 年。 [15] Hou HC (2011) Absorption and innovation: how emperors of high Qing Dynasty shape the Western craftsmanship (in Chinese), Journal of the Historical Studies, Vol.28, No.12, pp. 111-154. 侯皓之,”吸收與創新─盛清諸帝對西洋工藝的指導與創製”, 史學彙刊,第 28 卷,第 12 期,第 111-154 頁,2011 年。 [16] Hu Y (2009) The chime clock in the Forbidden City during 1601 (in Chinese), The Tide of Science & Technology, No.6, pp. 54-56. 胡源,”1601 年紫禁城裡的自鳴鐘”,科技潮,第 6 期,第 54-56 頁,2009 年。 [17] Dai NZ (2004) Early development of modern mechanical timer in China (in Chinese), China Metrology, No.2, pp. 43-48. 戴念祖,”中國近代機械計時器的早期發展”,中國計量,第 2 期,第 43-48 頁,2004 年。 [18] Piggott RK (2009) The Royal 'HAAGSE KLOK', pp. 30, http://www.antiquehorology.org/Piggott/RH/A_Royal_Haagseklok.pdf [19] Juan Y (Qing Dynasty) (1993), Theory of the Chime Clock, Yan Jing Shi Ji (in Chinese), Chung Hwa Book Co., Vol. 3, No. 5. 阮元, 自鳴鐘說, 《揅經室集》,第 3 卷, 第 5 集, 中華書局, 1993 年。 [20] Nie FL (2013) A comparative study with a focus on Zhongxue (in Chinese), Shandong Education Press, Jinan. 聶馥玲, 晚清經典力學的傳入─以《重學》為中心的比較研究, 山東教育出版社, 濟南, 2013 年。 [21] Qin SM (2007) Main points listing of timepieces maintenance in Palace Museum (in Chinese), Forbidden City, No. 7, pp. 114. 秦世明,”故宮博物院藏鐘錶修復舉要”,紫禁城,第 7 期, 第 114 頁,2007 年。