Hydraulic Mechanical Water Clock

The Chinese Hydraulic Water clock, created by Su Song in 1088 C.E. is a very important artifact. Although it is no longer in it's original state, this astounding clock is studied today all over the world.

How it Works
A simple hydraulic system
A simple hydraulic system

The ancient Chinese mechanical water clock worked in the same ways brakes on cars work today, using hydraulics. Hydraulics involves the science of applying force at one point, with the force then transferred to a second point using an incompressible liquid. For example, a simple hydraulic system consists of two pistons and a pipe connecting them. The basic operating principle of a hydraulic system is the definite volume and indefinite shape of the liquid. A hydraulic system was used to control the rate at which the water inside the clock flowed. If hydraulics were not used to control the flow of water, other miscellaneous tools could be used. These tools required a high level of maintenance and typically had to be adjusted or repaired daily.

Although many different types of water clocks have been developed, mechanical water clocks are classified as either inflow or outflow clocks. An outflow clock keeps time by allowing the water to drain out at a fixed rate. One example of an outflow mechanical water clock is a bowl with a small hole at the bottom and graduated lines marked on it. The bowl is then filled and as the water trickles out, the lines are used to keep track of the time elapsing. In contrast, an inflow clock keeps time by allowing water to flow into a container such as a cylinder.


Su Song water clock
Su Song water clock

The original Chinese mechanical water clock was built in 1088 C.E. The clock was over 30 feet high. Even though it was not perfectly accurate, it still gave people the general time of day. On the hour, wooden manikins came out of the bottom level, banging gongs and ringing bells to make sure that the people knew a new hour had begun. The manikins would also carry a stone tablet listing the time of day. In total, there were 117 of these manikins inside the clock. The clock contained an eleven foot water wheel with 36 buckets that filled with water to move the water throughout the tower. The water wheel turned about a hundred times a day. The clock consisted of 3 different levels. The top level had a bronze power-driven armillary sphere which represented the great circles of heaven. The middle level contained a celestial globe which rotated on its own to display the movement of celestial bodies. Finally, the bottom level was where the manikins were located. Though very complex to use, the water clock was the most helpful way to tell time for much of Asia and was the inspiration for modern day clocks.

"Life" of the Clock

One of Su Song's original building plans
One of Su Song's original building plans
Su Song, a Chinese expert in the calculation of calendars, otherwise known as an astronomer, built the first Chinese water clock. Su Song was not only an astronomer, but also a cartographer, zoologist, pharmacologist, mineralogist, and an engineer. He lived from 1020-1101, and died at the age of 81. At one point during his long life he was appointed the Ambassador of the Song dynasty. His most famous achievement occurred when he led a team of skilled mathematicians and artisans in building the large water clock tower. It took them about 12 years to build because it was such an immense project for the time. The final product was finished in 1088 C.E. Although the length of time cannot be confirmed, historians believe that the clock stood at the capital between 39-79 years before being disassembled by the Jin army. The army brought the clock back the city, now known as Beijing, hoping to put it back together and keep it as their own. The army was faced with a challenge when they discovered they did not bring the plans with them. They were unsuccessful in rebuilding the clock because it was so intricate and difficult to understand. When a new emperor gained control of China, he commanded Su Song's son, Su Xie, to rebuild the clock. After several years and numerous attempts to rebuild the clock, he failed. He realized that even with the plans, rebuilding the clock was nearly impossible because his father had left key parts of the clock out of his building plans. It is believed that he did this intentionally so that no one could ever have a clock like his. Even to this day, no one has been able to successfully replicate Su's clock the way it was originally.

Mimi- Period B
Anna- Period G
Amelia- Period F


  1. http://www.uh.edu/engines/epi1580.htm
  2. http://www.thenagain.info/webchron/Technology/SongClock.html
  3. http://www.wisegeek.com/what-is-a-water-clock.htm
  4. http://science.howstuffworks.com/hydraulic1.htm (picture one)
  5. http://www.nationmaster.com/encyclopedia/water-clock
  6. http://www.experiencefestival.com/a/water_clock/id/2012045
  7. http://fourriverscharter.org/projects/Inventions/pages/china_waterclock.htm (picture two)
  8. http://www.legends.mapsofworld.com/ancient/su-song.html#
  9. http://inventors.about.com/library/weekly/aa071401a.htm
  10. http://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Clock_Tower_from_Su_Song%27s_Book.JPG/180px-Clock_Tower_from_Su_Song%27s_Book.JPG (picture three)