MECHANICAL ENGINEERING

Water-raising machines

The earliest machine used by man for irrigation and water supply is the shaduf.It is illustrated as early as 2500 B.C.E in Akkadian reliefs and about 2000 B.C.E. in Egypt. It has remained in use until the present day and its application is world-wide, so that it is one of the most successful machines ever invented. Its success is probably due to its simplicity, since it can easily be constructed by the village carpenter using local materials. For fairly low lifts it delivers substantial quantities of water. It consists of a long wooden pole suspended at a fulcrum to a wooden beam supported by columns of wood, stone or brick. At the end of the short arm of the lever is a counterweight made of stone or, in alluvial areas where stone is not available, of clay. The bucket is suspended to the other end by a rope (see Figure 1). The operator lowers the bucket into the water and allows it to fill. It is then raised by the action or the counterweight and its contents are discharged into an irrigation ditch or a head tank.

The scoop drum or tympanum was probably invented in Egypt in the first half of the third century B.C.E. Two large timber discs were fixed to a wooden axle which had iron pegs protruding from its ends. The pegs were housed in iron bearings supported on two columns. The space between the discs was divided into eight segments by wooden boards. The perimeter was closed by wooden boards, there being a slot in each segment to receive the water. Circular holes were cut around the axle in one face of the drum, one hole to each segment.

The whole machine was coated with tar (see Figure 2). As the drum was rotated by a tread-wheel, the water was scooped from the source, entered the compartments when they were at the bottom of their travel and was discharged from them when they approached the top. The water ran into a channel and then into a head tank. The scoop drum is rarely mentioned by Muslim writers in connection with irrigation, and its main use seems to have been in de-watering mines. It is ideally suited for this purpose since it can be operated in a fairly restricted space. It was necessary to use a series of drums: the first raised the water into a tank on a platform, a second wheel raised it from this tank to a second tank and so on, until the water was discharged into a drain at the head of the mine.

The screw or water-snail was probably invented by Archimedes (c. 287-212 B.C.E.) when he was living in Egypt and it is therefore appropriate that the machine is often called the ‘Archimedean screw’. A wooden blade is fitted spirally to a long cylindrical wooden rotor. A wooden case is made to fit around the blade, constructed like a barrel, the planks painted with pitch and bound with iron hoops. The rotor is supplied with iron spigots which rotate in iron journals. The screw is set at an angle with one of its ends in the water and as it is rotated the water flows along the helix and discharges from the other end. The smaller the angle to the horizontal, the greater will be the rate of discharge. We do not know precisely how the machine was turned in earlier times – it may have been by a tread-wheel, the power transmitted through a pair of gears. Nowadays it is usually operated by a crank, but the crank is not known to have been in use before the sixth/twelfth century.

The screw was in common use throughout the Muslim world until quite recently, but now seems to be becoming rarer (see Figure 3).The word saqiya is used here to denote the chain-of-pots driven through a pair of gear-wheels by one or two animals harnessed to a draw-bar and walking around a circular track. This very important machine was invented in Egypt, probably about 200 B.C.E., but did not come into widespread use until the fourth or fifth century C.E., with the introduction of the pawl mechanism and earthenware pots. Although it is fairly easy to explain the operation of the machine, it should be emphasized that its construction is quite complex, consisting as it does of over 200 separate components. Only the basic constructional details will be given here. The draw-bar to which the animal is harnessed passes through a hole in an upright shaft to which the horizontal gear -wheel is fixed by spokes. The shaft rotates in a thrust bearing at ground level and another bearing above the gear -wheel located in a cross-beam which is supported on plinths. The gear-wheel is a lantern-pinion, i.e. two large wooden discs held apart by equally spaced pegs. The vertical gear- wheel carries the chain-of-pots and is often called the potgarland wheel. It is supported centrally over the well or other source of water on a wooden axle. On one side of it are the pegs that enter the spaces between the pegs of the lantern-pinion and these pegs pass through to the other side of the wheel, where they carry the chain-of-pots. 

A saqiya at Ma’arrat al-Nu’man near Aleppo, Syria

This consists of two continuous loops of rope between which the earthenware pots are attached – sometimes chains and metal containers are used (Figure 4). In order to prevent the wheel from going into reverse, the machine is provided with a pawl mechanism, which acts on the cogs of the potgarland wheel. This mechanism is essential, because the draught animal is subjected to a constant pull both when moving and when standing still. The pawl is activated in two cases – when the animal is to be unharnessed and in the event of the harness or traces breaking. Without the pawl the machine would turn backwards at great speed and, after one revolution, the drawbar would hit the animal on the head. At the same time, many of the pins of the lantern - pinion would break and the pots smash.

As the animal walks in a circular path, the lantern-pinion is turned and this rotates the potgarland wheel. The pots dip into the water in continuous succession and discharge at the top of the wheel into a channel connected to a head tank. Although the main function of the saqiya is for irrigation it can also be important for water supply when, for example, buildings are some distance above the source of water. The longer the chain-of-pots, i.e. the lift, the lower the rate of discharge will be. For domestic water supply this may not be a crucial factor, but in fact one of the problems of water-raising engineering is that of raising large quantities of water through a small lift.

The problem can be solved by using a spiral scoop-wheel (see Figure 5), which raises water to ground level with a high degree of efficiency. This machine is very popular in Egypt nowadays, and engineers at a research station near Cairo have been trying to improve the shape of the scoop in order to achieve maximum output. Although it appears very modern in design, this is not the case, since a miniature from Baghdad dated to the sixth/twelfth century shows a spiral scoop-wheel driven by two oxen. The transmission of power is the same as that employed with the standard saqiya.

The saqiya was widely used in the Muslim world from the earliest days onwards. It was introduced to the Iberian peninsula by the Muslims, where it was massively exploited. Not only was it diffused into many parts of Europe but it was also taken to the New World by Christian Spanish engineers. It has advantages over the diesel-driven pump: it can be constructed and maintained by local craftsmen and does not require the importation of fuel. The long history of the saqiya is by no means ended, and there are welcome indications that its advantages will ensure its survival for the foreseeable future.

Ulasan..

sumbangan kejuruteraan mekanikal yang utama dalam teknologi Islam ialah alat mengangkut air untuk kegunaan bagi tujuan pengairan, perumahan, industri dan lain-lain. Mesin pengangkut air yang pertama digunakan di Mesir dan Syria dan dipanggil Shaduf. Alat ini mudah dan murah dan masih digunakan hingga ke hari ini di Mesir. Sementara dua lagi jenis pengangkut air dinamakan saqiya dan nau'ra. Saqiya digerakkan oleh tenaga binatang ternakan, manakala nau'ra digerakkan oleh kuasa air.

saqiya yang menggunakan dengan kuasan pergerakkan binatang ia lebih mudah digerakkan dan kebanyakkanya diperbuat dengan menggunakan tiang dan kayu, dan kemudian akan ditolak dengan binatang bagi mengangkut air tersebut. Cara menggunakannya dengan Pengendali merendahkan baldi ke dalam air dan membolehkan ia untuk mengisi. Ia kemudian dibangkitkan oleh tindakan atau pengimbang dan kandungannya dilepaskan ke dalam parit pengairan atau tangki kepala.

dengan itu juga pelbagai cara yang digunakan untuk mengangkut air dan mudah untuk digunakan. kuasa binatang juga digunakan untuk pergerakkan terhadap saqiya dan membolehkan air naik keatas apabila telah diisi didalam baldi.penggunaan saqiya diteruskan sehinggalah muncul kemudahan pengangkut air yang lain ia juga terkenal di seluruh dunia pada zaman dahulu.