How Do Archimedes Screws Work?

The Archimedes screw is a simple machine (a type of pump) that has been used since ancient times. Its application ranges from lifting water from a lower to higher level, such as rivers or lakes, to irrigate agricultural fields to moving granular material along a more level surface. Its name is from the person who wrote about it, Archimedes (287-212 BC). Archimedes was a mathematician from Syracuse, Sicily, who studied in Alexandria, Egypt.

Physical Features

There are various basic versions of the Archimedes screw. One type is a corkscrew shaped tube. Another is one that has a hollow cylinder, and inside is a screw shaped (spiral shaped) component. The interior part is sized to be nearly the same dimension (inside diameter) as the interior of the cylinder it is placed in, but allowing for it to turn.

As with ordinary screws, the screw portion of an Archimedes screw can vary in length, height, number of blades on the screw and acuteness of the blade's angle. The surface can be smooth or coarse.

Application

When using an Archimedes screw, one end is placed in the material to be moved, such as water that is at a lower level than where it is needed. Since this is a movement of water from a lower to a higher point, the whole device is at an angle. The internal component, the screw, is rotated to ladle up the water that enters the device and is held within it between the blade and the interior diameter.

The operator turns the screw more, lifting up more water with it to be held within the cylinder and moved up as the screw is turned. This ongoing turning, lifting of water, filling up the interior of the Archimedes screw continues until the water spills out the top at the intended destination. The operator continues to turn the screw until the amount of water needed is obtained.

Construction Principles

How efficient an Archimedes screw works is determined by its structure: the diameter (inside and out), the angle it’s placed at and how long it is, the angle of the blades, the number of blades and the rate at which the internal component is turned.

When water moves down a pipe, the rate of flow is faster in the central part of the pipe than toward the outer diameter. This rate of flow is a consideration when designing an Archimedes screw for use with an application. If the use of the screw is to force material from one source to another, then the distance between the interior diameter of the cylinder and the screw blades needs to be very small. If there is not the need for high pressure, then there can be a more open area between the blades and the interior wall of the cylinder.

Operation Principles

The speed at which the screw is turned has to allow for a smooth movement of the material being moved. If too fast, the water doesn’t have time to fill the open areas within the cylinder before the screw turns, reducing the efficiency of the device.

Also, just as it is more of a challenge to carry a full bucket of water than an empty one, the Archimedes screw becomes more difficult to turn when there is more water in it; the pressure needed to turn it increases.

Benefits

Even though the Archimedes screw was invented in ancient times, it has been adapted throughout time. Due to the simplicity of how it works, the Archimedes screw can be environmentally friendly by being powered by a windmill. Motors can be added for industrial applications. And even though it is most well known for lifting, when viewed from another perspective, it is also used for pushing material forward.

References

• All About Pumps/Russell D. Hoffman: Archimedes Screw Pump
• Global Oneness Commitment: Pump Types
• Global Oneness Commitment: Archimedes Screw – A Wisdom Archive
• School for Champions/Ron Kurtus: Archimedes – Early Years and Mathematics
• Drexel University Department of Computer Science: Archimedes Screw Illustrations

Resources

• Drexel University Department of Computer Science: Archimedes Screw – Optimal Design