ARCHIMEDES' SCREW
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Archimedes' screw solved one of the greatest practical problems of antiquity, which was finding an easy way to lift liquids. Archimede created a machine that allowed this operation to be carried out with relative simplicity: the Archimedean screw. The machine is made up of a large screw and placed inside a tube, not necessarily welded watertight. The lower part of the tube is immersed in a liquid and, by rotating the screw, each step collects a certain quantity of substance which is raised along the spiral until it exits from the upper part, to be discharged into a storage basin.
The energy for rotation can be provided by a handle, by animals, by windmill propellers or by agricultural tractors. The Archimedean screw is attributed to Archimedes on the basis of the testimonies of Diodorus Siculus and Athenaeus. Recent studies, however, indicate that it may have already been invented before Archimedes, as it is thought to have been used to irrigate the hanging gardens of Babylon. Archimedes may have studied the screw during his stay in Alexandria in Egypt and may have imported an instrument into Italy that was therefore already known in the Middle Eastern country. Archimedes' studies have a notable influence on the history of science both in antiquity, when the rigor of his demonstrations is taken as a model, and in the Renaissance when his works, published in versions or in the original text, are the subject of great interest for those who founded modern experimental science. Galileo Galilei takes up Archimedes' screw in his work Le Meccaniche: in the passage "On Archimedes' screw for removing water", he demonstrates how it works. “It does not seem to me that in this place Archimedes' invention of raising water with the screw should be passed over in silence: which is not only marvelous, but miraculous; for we will find that the water ascends in the vine, continually descending.”
Even today, Archimedes' screw is used in various contexts to lift substances in the solid, liquid and gaseous states. Furthermore, the hydraulic auger can be applied to uneven water levels, as it exploits the potential energy in a stationary position. At the highest point, the potential energy of the water is maximum and as a result of the consequent fall towards the lowest point, it is conveyed into a rotor connected to a generator which transforms the kinetic energy given by the movement of the screw into electrical energy . The fluid enters the cochlea, namely its three or four compartments, at the highest point, while a motor, started by an electrical impulse, sets it in motion. The different compartments form individual chambers in which the incoming water pushes, thanks to the earth's gravitational force, creating a rotation principle. The energy produced by the rotation of the auger shaft is transmitted, through a belt multiplier, to a generator; the rotation speed is minimal, in fact what wins in this technology is not the speed, but the thrust force.
Source: Archimede's Blog
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