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Writer's pictureSílvio Pereira

Su Sung's Clock: A Marvel of Medieval Chinese Mechanical Engineering

By: Silvio Pereira

 
 

Introduction


Su Sung

The Su Sung Clock (also known as the Su Song Clock) is one of the most remarkable achievements of ancient Chinese engineering. Built in the early 11th century, this device was much more than just a clock; it was a complex astronomical tower that combined timekeeping with observation of the heavens. This technical feat is attributed to the scholar and engineer Su Sung (1020–1101), a Chinese polymath who was an astronomer, pharmacologist, and diplomat. His most famous work, the water clock, was notable for its innovative use of gears and automation, marking a high point in the history of pre-industrial mechanical engineering.





Song Dynasty, the dynasty of knowledge

The Historical and Cultural Context


China during the Song dynasty (960–1279) was a center of great innovation and technological development. At that time, astronomy was closely linked to government and science. Emperors relied on astronomers to establish calendars and predict important astronomical events, which in many cultures was considered essential to maintaining cosmic and political order.


Su Sung was tasked with designing a device that could not only accurately measure time, but also monitor and record the movements of celestial bodies. Construction of the clock began around 1088 and was completed in 1092 in the city of Kaifeng, the capital of the Song Empire. This construction was not only a demonstration of China’s technological supremacy, but also a valuable tool for imperial administration. Su Sung’s clock was an imposing structure that used the power of water to drive a series of intricate mechanisms. The centerpiece was a huge wheel with 36 compartments, which rotated slowly, driven by the constant flow of water. As each compartment filled, it triggered a series of movements that updated the clock’s various displays.

Schematic of Su Sung's water clock

Structure and Function of Su Sung's Clock


Su Sung's clock was an impressive tower about 12 meters high, equipped with several features:


1. Water clock (clepsydra): The heart of the mechanism was a sophisticated water clock system. This method of measuring time was already used in China, but Su Sung innovated by combining the hydraulic system with complex gears that allowed for continuous and automatic movement. The water, stored in a reservoir, flowed in a controlled manner, creating pressure that moved the gears and, in turn, the rest of the mechanism.


2. Water escapement : One of the great innovations of Su Sung's watch was the use of an escapement mechanism . Although rudimentary escapements were already known in older water clock systems, Su Sung developed a more advanced escapement that regulated the flow of water evenly, ensuring much more accurate timekeeping.


3. Automation and movement of the celestial spheres: The clock also contained an armillary sphere , a mechanical model that represented the movement of celestial bodies. This sphere rotated automatically, allowing regular and time-aligned astronomical observations. With this device, Su Sung was able to accurately map the heavens and establish detailed calendars.


4. Dials and automatons: The tower included multiple floors of dials that indicated the time and the movements of the celestial bodies. It also had automatons —mechanical figures that emerged at set times to ring bells, drums, and gongs, announcing the time and other significant events. These automatons were controlled by a complex system of gears and were considered one of the greatest mechanical marvels of the time.


The main functions of the watch included:


  • Indication of the time: Through mechanical figures that moved on spheres, the clock presented the time clearly and precisely.

  • Display of the days of the month: A mechanical calendar indicated the date, taking into account the different lengths of the lunar and solar months.

  • Representation of the phases of the Moon: A miniature model of the Moon showed the different phases, from the new moon to the full moon.

  • Demonstration of celestial movements: The clock had a celestial globe that moved in sync with the real movements of the stars, allowing astronomers to study celestial patterns.


Technological Innovations


©egiosfera
©egiosfera

Su Sung's watch is recognized for several technological innovations, which influenced the development of automatic watches and movements both in China and eventually in other parts of the world. Some of these innovations include:


1. Chain- fuse escapement : Although the use of this type of mechanism was more associated with later Western watches, the concept of a regulated system of energy release (in this case, water) was already essential in Su Sung's watch. This concept would later be a cornerstone in the development of mechanical watches in Europe.


2. Complex gears: The use of gears to transmit continuous motion was already known, but the precision and sophistication of Su Sung's system was remarkable for its time. Each gear and cog was designed to maximize the efficiency of the hydraulic system and maintain accuracy over time.


3. Early automation: The use of mechanical figures that acted automatically was a particularly advanced feature. This idea of automation not only provided an aesthetic and functional value (such as telling the time), but also reflected the mechanical ingenuity of this period.


The Legacy and the Destruction


Unfortunately, Su Sung's clock did not survive the passage of time intact. In 1126, during the Jurchen invasion of Kaifeng, the tower and clock were dismantled and taken as spoils of war to Manchuria. Although attempts were made to rebuild it, the original device was lost.


However, the impact of this clock on the history of technology was immense. Su Sung's design was recorded in his treatise "Xin Yi Xiang Fa Yao" (新儀象法要), which described the design and operation of the clock. This information preserved knowledge about the device and helped influence the development of other mechanical technologies, both in China and abroad.


Influence on Global Watch Development



Although China maintained a strong tradition of mechanical clockmaking until the mid-imperial period, the impact of Su Sung's engineering may have indirectly contributed to the development of clockwork mechanisms in Europe centuries later. The concept of a regulated mechanism, such as Su Sung's escapement system, is a precursor to the mechanical clock escapement that emerged in Europe during the Renaissance.


Conclusion


Su Sung’s clock represents a milestone in the history of watchmaking and mechanical engineering. Although its construction took place almost a thousand years ago, the technological innovations incorporated into its design continue to be recognized as remarkable advances for their time. The fusion of scientific precision with advanced mechanics makes this clock one of the technological marvels of ancient China and a testament to human ingenuity.


Full size replica

Today, Su Sung is remembered as one of the great pioneers of mechanical engineering, and his legacy endures as a symbol of the technological greatness of Chinese civilization.

Replica models of Su Sung's clock can be found in museums around the world, allowing the public to admire the complexity and beauty of this masterpiece of Chinese engineering.


Some final considerations


· Buddhist influence on the clock's construction: Buddhist philosophy, with its search for order and harmony, may have influenced the clock's design and construction.


· The relationship between Su Song's clock and Chinese astrology: Astrology was a very important science in ancient China, and Su Song's clock certainly embodied many of the astrological concepts of the time.


· The difficulties faced by Su Song in building the clock: Building such a complex clock must have been a huge challenge. Su Sung and his team had to overcome many major obstacles of various kinds to build this clock.



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