Archimedes' screw
It was so-named after the Greek mathematician Archimedes who first described it around 234 BC, although the device had been developed in Egypt earlier in the century.
In the modern world, Archimedes screw pumps are widely used in wastewater treatment plants and for dewatering low-lying regions.
Run in reverse, Archimedes screw turbines act as a new form of small hydroelectric powerplant that can be applied even in low head sites.
[1] Some researchers have proposed this device was used to irrigate the Hanging Gardens of Babylon, one of the Seven Wonders of the Ancient World.
A cuneiform inscription of Assyrian King Sennacherib (704–681 BC) has been interpreted by Stephanie Dalley[4] to describe casting water screws in bronze some 350 years earlier.
This is consistent with Greek historian Strabo, who describes the Hanging Gardens as irrigated by screws.
[6] Athenaeus of Naucratis quotes a certain Moschion in a description on how Hiero II of Syracuse commissioned the design of the Syracusia, a luxury ship which would be a display of naval power.
[8] It is said to have been the largest ship built in classical antiquity and was launched by Archimedes who designed device with a revolving screw-shaped blade inside a cylinder to remove any potential water leaking through the hull.
German engineer Konrad Kyeser equipped the Archimedes screw with a crank mechanism in his Bellifortis (1405).
[13] Developments in maritime transport occurred over the next 180 years from the Fawcett, Preston and Company double blade design and patents by Sharrow Marine to address rotary propulsion and flow control on boating vessels through loop propellers.
[14][15] Archimedes screws are used in sewage treatment plants because they cope well with varying rates of flow and with suspended solids.
[16] Screw turbines (ASTs) are a new form of generator for small hydroelectric powerplants that could be applied even in low-head sites.
The low rotation speed of ASTs reduces negative impacts on aquatic life and fish.
Other inventions using Archimedes screws include the auger conveyor in a snow blower, grain elevator, concrete mixer and chocolate fountain.
The screw is usually turned by windmill, manual labor, cattle, or by modern means, such as a motor.
The contact surface between the screw and the pipe does not need to be perfectly watertight, as long as the amount of water being scooped with each turn is large compared to the amount of water leaking out of each section of the screw per turn.
The design of the everyday Greek and Roman water screw, in contrast to the heavy bronze device of Sennacherib, with its problematic drive chains, has a powerful simplicity.
A double or triple helix was built of wood strips (or occasionally bronze sheeting) around a heavy wooden pole.
A cylinder was built around the helices using long, narrow boards fastened to their periphery and waterproofed with pitch.
Based on the common standards that the Archimedes screw designers use this analytical equation could be simplified as:[17]
A screw conveyor is a similar device which transports bulk materials such as powders and cereal grains.
On a much larger scale, Archimedes's screws of decreasing pitch are used for the compaction of waste material.
Such an installation has the same benefits as using the screw for pumping: the ability to handle very dirty water and widely varying rates of flow at high efficiency.
The screw works well as a generator at low heads, commonly found in English rivers, including the Thames, powering Windsor Castle.
