Historical Science & Technology, Technology

Archimedes’ Screw: Hey, This is A Family Site!

Archimedes’ screw is a hand-operated machine used by the Ancient Greeks (and other cultures since their time) to raise water from low-lying bodies to higher elevations, usually for the purposes of irrigation. Also known as a screw pump, Archimedes’ screw is a simple yet effective device, modern variations of which can still be found in use today.

Invented By, Or Merely Credited To?

The invention of the screw pump is commonly attributed to Archimedes of Syracuse, a Greek polymath who lived in the 3rd Century BCE. However, historical records describe similar devices being used by the Assyrians over 350 years prior to Archimedes’ birth. It is possible that the device was simply unknown to the Greeks prior to that time, and that Archimedes merely mimicked the design of water pumps he saw in use during a visit to Egypt.

Either way, he must’ve done something right, because the device is still called the Archimedes’ screw 2,000-plus years later.

Simple, Yet Effective

A typical Archimedes’ screw is comprised of a flat, helical surface winding around a cylindrical center shaft (like a spiral staircase anchored to a center pole) enclosed in a hollow pipe. As the shaft turns, the bottom end of the screw surface scoops up water and slides it up the pipe until it reaches the top, where it pours out.

A modern Archimedes' screw, with open-top casing.

A modern Archimedes’ screw, with open-top casing.

Originally, screw pumps were operated by hand, but windmill- or water-powered designs soon followed. Some designs had the screw attached to the inside of the tube itself, with the whole device rotating as one, rather than the screw turning independently of the stationary tube. It is believed that this variation allowed the apparatus to be powered by human treading (i.e. people walking in place on top of the casing as it rotated).

Common Applications & Legacy

In addition to feeding irrigation systems, Archimedes’ screw was also used to drain water out of mines and other low lying areas. In the Netherlands, it was used to drain land that was underwater to create agricultural polders.

The auger device at the front of a snow blower is essentially an Archimedes’ screw turned on its side. Modern Archimedes’ screws are used in sewage treatment facilities. In 2001, a screw pump was used by British engineer John Burland to stabilize the Leaning Tower of Pisa. Perhaps most importantly of all, Archimedes’ screws are used in chocolate fountains.

Photo credit: ARG_Flickr / Foter / Creative Commons Attribution 2.0 Generic (CC BY 2.0)

Historical Science & Technology

Aeolipile: The World’s First Steam Powered Engine

The aeolipile, known more fantastically as the “Hero engine,” is a steam powered, rocket style jet engine, invented by Hero of Alexandria in the 1st century CE. The word “aeolipile” derives from Greek and Latin origins, and translates to “the ball of Aeolus,” referencing the Greek god of air and wind.

What is An Aeolipile?

The aeolipile is a reaction steam turbine, the first of its kind in history. It consists of a spherical or cylindrical vessel (references to both have been found, and recreations have been equally successful using either shape) arranged to rotate on its axis. The vessel has oppositely bent or curved nozzles projecting from either side.

Water is heated in a boiler, which, in most aeolipiles, forms part of the rotating chamber’s base. The boiler is connected to the vessel via a pair of pipes that feed into it, one on each side; these pipes are also the pivot point for the vessel. A simplified version of the aeolipile uses the rotating chamber itself as the boiler, simplifying the construction of the bearings and pivot point.

When the vessel is pressurized with steam, the steam is expelled through the nozzles. As they are pointing in opposite directions, this produces force perpendicularly to the axis of the vessel’s bearing. The opposite thrusts combine to produce rotational movement (torque), spinning the vessel on its axis.

This is the first recorded use of the rocket principle as it relates to Newton’s 2nd and 3rd laws of motion.

Steady state speed is achieved relatively quickly, as aerodynamic drag and frictional forces in the bearings rapidly build up with increasing RPMs and cancel out the accelerating torque.

Origins

Prior to Hero of Alexandria’s lifetime, the Roman author Vitruvius (c. 80 BCE – c. 15 BCE) also described the aeolipile in his writings, though it is unclear whether or not it is truly the same device that is being referenced. As Hero (c. 10 – 70 CE) provides a more practical description of the aeolipile, including instructions for how to build one, he is generally credited as the device’s inventor.

Practical or Demonstrative Use?

There is no record of ancient aeolipiles being used for practical purposes. Indeed, the device’s design calls into question whether any practical use could be found for it. The aeolipile is most often depicted as a standalone device, and, like many other devices described in Hero’s Pneumatica, was likely intended as a “temple wonder”—that is, a device intended to perform only as demonstration. However, the aeolipile did pave the way for the many useful steam-powered devices that would follow.

See Also

For more info, and to view photos of a replica aeolipile in action, visit ModelEngines.info/aeolipile.