Ismail al-Jazari

A camshaft, a shaft to which cams are attached, was introduced in 1206 by al-Jazari, who employed them in his automata,[13] water clocks (such as the candle clock)[14] and water-raising machines.[13] The cam and camshaft also appeared in European mechanisms from the 14th century.[15]

The eccentrically mounted handle of the rotary quern-stone in fifth century BCE Spain that spread across the Roman Empire constitutes a crank.[16] The earliest evidence of a crank and connecting rod mechanism dates to the 3rd century AD Hierapolis sawmill in the Roman Empire.[16] The crank also appears in the mid-9th century in several of the hydraulic devices described by the Banū Mūsā brothers in their Book of Ingenious Devices.[17]

In 1206, al-Jazari invented an early crankshaft,[18][19] which he incorporated with a crank-connecting rod mechanism in his twin-cylinder pump.[20] Like the modern crankshaft, al-Jazari's mechanism consisted of a wheel setting several crankpins into motion, with the wheel's motion being circular and the pins moving back-and-forth in a straight line.[18] The crankshaft described by al-Jazari[18][19] transforms continuous rotary motion into a linear reciprocating motion,[20] and is central to modern machinery such as the steam engine, internal combustion engine and automatic controls.[19][21]

He used the crankshaft with a connecting rod in two of his water-raising machines: the crank-driven saqiya chain pump and the double-action reciprocating piston suction pump.[20][22] His water pump also employed the first known crank-slider mechanism.[23]

English technology historian Donald 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.[7]

Al-Jazari invented a method for controlling the speed of rotation of a wheel using an escapement mechanism.[24]

According to Donald Hill, al-Jazari described several early mechanical controls, including "a large metal door, a combination lock and a lock with four bolts".[7]

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."[25] 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.[26]

The first known use of a crankshaft in a chain pump was in one of al-Jazari's saqiya machines. 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. 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,[28] and were in everyday use throughout the medieval Islamic world.[29]

Citing the Byzantine siphon used for discharging Greek fire as an inspiration,[30] al-Jazari went on to describe the first suction pipes, suction pump, double-action pump, and made early uses of valves and a crankshaft-connecting rod mechanism, when he invented a twin-cylinder reciprocating piston suction 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 water-raising machine had a direct significance for the development of modern engineering. This pump is remarkable for three reasons:[7][31][32][33]

• The first known use of a true suction pipe (which sucks fluids into a partial vacuum) in a pump.
• The first application of the double-acting principle.
• The conversion of rotary to reciprocating motion via the crank-connecting rod mechanism.

Al-Jazari's suction piston pump could lift 13.6 metres of water, with the help of delivery pipes. This was more advanced than the suction pumps that appeared in 15th-century Europe, which lacked delivery pipes. It was not, however, any more efficient than the noria commonly used by the Muslim world at the time.[34]

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.[35]

One of al-Jazari's humanoid automata was a waitress that could serve water, tea or drinks. The drink was stored in a tank with a reservoir from where the drink drips into a bucket and, after seven minutes, into a cup, after which the waitress appears out of an automatic door serving the drink.[40]

Al-Jazari invented a hand washing automaton incorporating a flush mechanism now used in modern flush toilets. It features a female humanoid automaton standing by a basin filled with water. When the user pulls the lever, the water drains and the female automaton refills the basin.[41]

Al-Jazari's "peacock fountain" was a more sophisticated hand washing device featuring humanoid automata as servants which offer soap and towels. Mark E. Rosheim describes it as follows:[38]

Pulling a plug on the peacock's tail releases water out of the beak; as the dirty water from the basin fills the hollow base a float rises and actuates a linkage which makes a servant figure appear from behind a door under the peacock and offer soap. When more water is used, a second float at a higher level trips and causes the appearance of a second servant figure – with a towel!

Al-Jazari's musical robot band.

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.[7]

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.[42]

One of al-Jazari's candle clocks.

According to Donald Hill, al-Jazari described the most sophisticated candle clocks known to date. Hill described one of al-Jazari's candle clocks as follows:[7]

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. No other candle clocks of this sophistication are known.

Al-Jazari's candle clock also included a dial to display the time and, for the first time, employed a bayonet fitting, a fastening mechanism still used in modern times.[44]

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.[45]

Automatic castle clock of al-Jazari, 14th century copy.

Al-Jazari's largest astronomical clock was the "castle clock", which was a complex device that was about 11 feet (3.4 m) high, and had multiple functions besides timekeeping. It included a display of the zodiac and the solar and lunar orbits, and an innovative feature of the device was a pointer in the shape of the crescent moon which travelled across the top of a gateway, moved by a hidden cart, and caused automatic doors to open, each revealing a mannequin, every hour.[7][46] Another innovative feature was the ability to reprogram the length of day and night in order to account for their changes throughout the year.

Another feature of the device was five automata musicians who automatically play music when moved by levers operated by a hidden camshaft attached to a water wheel.[14] Other components of the castle clock included a main reservoir with a float, a float chamber and flow regulator, plate and valve trough, two pulleys, crescent disc displaying the zodiac, and two falcon automata dropping balls into vases.[47] Al-Jazari's castle clock is considered to be the earliest programmable analog computer.[14]

Al-Jazari invented water clocks that 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.[27][43] Al-Jazari's famous water-powered scribe clock was reconstructed successfully at the Science Museum, London in 1976.