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The screw pump is the oldest positive displacement pump. [1] The first records of a water screw, or screw pump, date back to Hellenistic Egypt before the 3rd century BC. [1] [3] The Egyptian screw, used to lift water from the Nile, was composed of tubes wound round a cylinder; as the entire unit rotates, water is lifted within the spiral tube to the higher elevation.
The Archimedes screw generator consists of a rotor in the shape of an Archimedean screw which rotates in a semicircular trough. Water flows into the screw and its weight presses down onto the blades of the turbine, which in turn forces the turbine to turn. Water flows freely off the end of the screw into the river.
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Animation showing the operation of a screw. As the screw shaft rotates, the nut moves linearly along the shaft. This is a type called a lead screw. A machine used in schools to demonstrate the action of a screw, from 1912. It consists of a threaded shaft through a threaded hole in a stationary mount.
Three principal forms exist; In its simplest form (the Archimedes' screw pump or 'water screw'), a single screw rotates in a cylindrical cavity, thereby gravitationally trapping some material on top of a section of the screw as if it was a scoop, and progressively moving the material along the screw's axle until it is discharged at the top.
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For example, a bench vise consists of a lever (the vise's handle) in series with a screw, and a simple gear train consists of a number of gears (wheels and axles) connected in series. The mechanical advantage of a compound machine is the ratio of the output force exerted by the last machine in the series divided by the input force applied to ...
The steeper the incline, the greater the risk of the user slipping from the top of the screw. No doubt the reverse water wheel was easier to use with a horizontal treading surface. On the other hand, the screw could be operated by a crank handle fitted to the central axle , but would be more tiring since the weight of the operator does not bear ...