A 13th Century Elephant Clock - Great Example of Control Engineering

by Meam Wye on July 10, 2009

'Elephant clock' invented by Al-Jazari in the thirteenth century consisted of many modern control engineering mechanisms such as automaton, closed-loop system and flow regulators. It was the first clock to use time-based automaton.

Abu al-'Iz Ibn Isma'il ibn al-Razaz al-Jazari (1136 – 1206) wrote an amazing book in 1206 titled 'Kitáb fí ma'rifat al-hiyal al-handasiyya' (Book of Knowledge of Ingenious Mechanical Devices). In this book he described in detail the construction of fifty mechanical devices that were classified in six categories.

Elephant clock was basically a water clock about 4 feet long and 6 feet high with clock mechanisms on an artificial elephant. It was the first water clock that accurately recorded the passage of the temporal hours by changing the rate of flow to match the uneven length of days. The clock was an example of automata as after the passage of every hour or half,the mahout hits the drum and the mechanical bird sitting on top of a dome mounted on the elephant sings.

Professor Salim Al Hassani describes the mechanism of this clock as follows:

"The submersible float or tarjahar drives the clock. Initially, the submersible float lies on the surface of the water in the tank. A calibrated orifice on its underside allows water to enter and subsequently sinks the float. Attached to the submersible float are a wire and a chain. The wire runs from the float to the ball release mechanism inside the castle and activates it when the float sinks. The chain runs from the underside of the float to a staple on the tail of the serpent. Upon activation of the return mechanics for the serpent, the chain will tilt the sunken float out of the water thus emptying it of its contents. Then the emptied float will rest on the water surface and repeat the cycle. At the top of the lock, supported by four columns, is the castle (a square brass box with a detachable dome). Inside the castle is a ball release mechanism, which when activated, releases a ball that travels down a channel leading to the beak of the falcon. The ball will travel from the beak of the falcon onto the open mouth of the serpent. The serpent is in effect a pulley which rotates on an axle that rests on bearings fixed between each pair of the columns. Upon loading with the ball, the serpent head will be lowered down to the vase. Once the ball drops away from the serpent's mouth, the return mechanism of the serpent is activated and the serpent returns to its original position. The clock will continue to work as long as there are metal balls in the magazine."

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