Prof. Lynn White Jr. writes: “Segmental gears first clearly appear in A1-Jazari, in the West they emerge in Giovanni de Dondi‘s astronomical clock finished in 1364, and only with the great Sienese engineer Francesco di Giorgio (1501) did they enter the general vocabulary of European machine design“.

(From Wikipedia, the free encyclopedia)

Abū al-’Iz Ibn Ismā’īl ibn al-Razāz al-Jazarī (1136-1206) (Arabic: أَبُو اَلْعِزِ بْنُ إسْماعِيلِ بْنُ الرِّزاز الجزري) was an important Arabic Muslim scholar, artist, astronomer, craftsman, inventor and mechanical engineer from al-Jazira, Mesopotamia who flourished during the Islamic Golden Age (Middle Ages). He is best known for writing the Book of Knowledge of Ingenious Mechanical Devices in 1206, where he described fifty mechanical devices.

Biography

Little is known about Al-Jazari, and most of that comes from the introduction to his Book of Knowledge of Ingenious Mechanical Devices. He was named after the area in which he was born, al-Jazira - the traditional Arabic name for what was northern Mesopotamia and what is now northern Iraq and northeastern Syria, between the Tigris and the Euphrates. Like his father before him, he served as chief engineer at the Artuklu Palace, the residence of the Diyarbakır branch of the Turkish Artuqid dynasty which ruled across eastern Anatolia as vassals of the Zangid rulers of Mosul and later Fatimid general Saladin.[1]

Al-Jazari was part of a tradition of craftsmen and was thus more of a practical engineer than an inventor [2] who appears to have been “more interested in the craftsmanship necessary to construct the devices than in the technology which lay behind them” and his machines were usually “assembled by trial and error rather than by theoretical calculation.”[3] Some of his devices were also inspired by earlier devices, such as one of his monumental water clocks being based on that of a Pseudo-Archimedes.[4]

Mechanisms and methods

While many of al-Jazari’s inventions may now appear to be trivial, the most significant aspect of al-Jazari’s machines are the mechanisms, components, ideas, methods and design features which they employ.[1]

Crankshaft and connecting rod mechanism

Al-Jazari invented the crankshaft, though not the hand-operated crank (which appeared in Han China) but he was the first to incorporate it in a machine. It transforms continuous rotary motion into a linear reciprocating motion,[5] and is central to modern machinery such as the steam engine, internal combustion engine (where it converts in the other direction) and automatic controls.[6][7]

The connecting rod was also invented by al-Jazari, and was used in a crank and connecting rod system in a rotating machine he developed in 1206, in two of his water-raising machines: the crank-driven saqiya chain pump and the double-action reciprocating piston suction pump.[5]

Design and construction methods

Donald Routledge Hill writes:

“We see for the first time in al-Jazari’s work several concepts important for both design and construction: the lamination of timber to minimize warping, the static balancing of wheels, the use of wooden templates (a kind of pattern), the use of paper models to establish designs, the calibration of orifices, the grinding of the seats and plugs of valves together with emery powder to obtain a watertight fit, and the casting of metals in closed mold boxes with sand.”[1]

[edit] Escapement mechanism in a rotating wheel

Al-Jazari invented a method for controlling the speed of rotation of a wheel using an escapement mechanism.[8]

Mechanical controls

According to Donald Routledge Hill, al-Jazari described several early mechanical controls, including “a large metal door, a combination lock and a lock with four bolts.”[1]

Segmental gear

A segmental gear is “a piece for receiving or communicating reciprocating motion from or to a cogwheel, consisting of a sector of a circular gear, or ring, having cogs on the periphery, or face.”[9] Professor Lynn Townsend White, Jr. wrote:

“Segmental gears first clearly appear in Al-Jazari, in the West they emerge in Giovanni de Dondi‘s astronomical clock finished in 1364, and only with the great Sienese engineer Francesco di Giorgio (1501) did they enter the general vocabulary of European machine design.”[10]

Water-raising machines

Al-Jazari invented five machines for raising water,[11] as well as watermills and water wheels with cams on their axle used to operate automata,[12] in the 12th and 13th centuries, and described them in 1206. It was in these water-raising machines that he introduced his most important ideas and components.

Saqiya chain pumps

The first known use of a crankshaft in a chain pump was in one of al-Jazari’s saqiya machines.[13] The concept of minimizing intermittent working is also first implied in one of al-Jazari’s saqiya chain pumps, which was for the purpose of maximising the efficiency of the saqiya chain pump [13] Al-Jazari also constructed a water-raising saqiya chain pump which was run by hydropower rather than manual labour, though the Chinese were also using hydropower for chain pumps prior to him. Saqiya machines like the ones he described have been supplying water in Damascus since the 13th century up until modern times,[14] and were in everyday use throughout the medieval Islamic world.[13]

Double-action suction pump with valves and reciprocating piston motion

In 1206, Al-Jazari described the first suction pipes, suction pump, double-action pump, valve, and crankshaft-connecting rod mechanism, when he invented a twin-cylinder reciprocating piston pump. This pump is driven by a water wheel, which drives, through a system of gears, an oscillating slot-rod to which the rods of two pistons are attached. The pistons work in horizontally opposed cylinders, each provided with valve-operated suction and delivery pipes. The delivery pipes are joined above the centre of the machine to form a single outlet into the irrigation system. This may be the only one of al-Jazari’s inventions which had a direct significance for the development of modern engineering. This pump is remarkable for three reasons:[1]

* The first known use of a true suction pipe in a pump.
* The application of the double-acting principle.
* The conversion of rotary to reciprocating motion, via the crankshaft-connecting rod mechanism.

Water supply system

Al-Jazari developed the earliest water supply system to be driven by gears and hydropower, which was built in 13th century Damascus to supply water to its mosques and Bimaristan hospitals. The system had water from a lake turn a scoop-wheel and a system of gears which transported jars of water up to a water channel that led to mosques and hospitals in the city.[15]

Automata

Al-Jazari invented automated moving peacocks driven by hydropower.[16] He also invented the earliest known automatic gates, which were driven by hydropower.[15] He also created automatic doors as part of one of his elaborate water clocks.[1]

Al-Jazari also designed and constructed a number of other automata, including automatic machines, home appliances, and musical automata powered by water.[17] Al-Jazari also invented water wheels with cams on their axle used to operate automata.[12]

Musical automata

Al-Jazari’s musical automata.

Al-Jazari’s work described fountains and musical automata, in which the flow of water alternated from one large tank to another at hourly or half-hourly intervals. This operation was achieved through his innovative use of hydraulic switching.[1]

Al-Jazari created a musical automaton, which was a boat with four automatic musicians that floated on a lake to entertain guests at royal drinking parties. Professor Noel Sharkey has argued that it is quite likely that it was an early programmable automata and has produced a possible reconstruction of the mechanism; it has a programmable drum machine with pegs (cams) that bump into little levers that operated the percussion. The drummer could be made to play different rhythms and different drum patterns if the pegs were moved around.[18] According to Charles B. Fowler, the automata were a “robot band” which performed “more than fifty facial and body actions during each musical selection.”[19]

Clocks

Al-Jazari constructed a variety of water clocks and candle clocks. These included a portable water-powered scribe clock, which was a meter high and half a meter wide, reconstructed successfully at the Science Museum (London) in 1976 [12][20]

Astronomical clocks

Al-Jazari invented monumental water-powered astronomical clocks which displayed moving models of the Sun, Moon, and stars. His largest astronomical clock, which was about 11 feet high, displayed the zodiac and the solar and lunar orbits. Another innovative feature of the clock was a pointer which travelled across the top of a gateway and caused automatic doors to open every hour.[21][1]

Candle clocks

According to Donald Routledge Hill, al-Jazari described the most sophisticated candle clocks known to date. Hill described one of al-Jazari’s candle clocks as follows:[1]

“The candle, whose rate of burning was known, bore against the underside of the cap, and its wick passed through the hole. Wax collected in the indentation and could be removed periodically so that it did not interfere with steady burning. The bottom of the candle rested in a shallow dish that had a ring on its side connected through pulleys to a counterweight. As the candle burned away, the weight pushed it upward at a constant speed. The automata were operated from the dish at the bottom of the candle.”

Elephant clock with automaton

The elephant clock described by al-Jazari in 1206 is notable for several innovations. It was the first clock in which an automaton reacted after certain intervals of time (in this case, a humanoid robot striking the cymbal and a mechanical robotic bird chirping) and the first water clock to accurately record the passage of the temporal hours to match the uneven length of days throughout the year.[22]

Weight-driven water clocks

Al-Jazari invented clocks which were driven by both water and weights. These included geared clocks and a portable water-powered scribe clock, which was a meter high and half a meter wide. The scribe with his pen was synonymous to the hour hand of a modern clock.[12][23] Al-Jazari’s famous water-powered scribe clock was reconstructed successfully at the Science Museum (London) in 1976.

Miniature paintings

Alongside his accomplishments as an inventor and engineer, al-Jazari was also an accomplished artist. In The Book of Knowledge of Ingenious Mechanical Devices, he gave instructions for of his inventions and illustrated them using miniature paintings, a medieval style of Islamic art.