Lecture 17: Lifting Water with Human Power
Understanding Greek and Roman Technology: From the Catapult to the Pantheon
Dr Stephen Ressler (2013)
The Screw Pump
Ancient Greeks and Romans needed to pump water for fire fighting, irrigation, removing bilge water from ships and removing water from mines. The first pump they used was based on the sixth simple machine described by Archimedes (the screw).
The Archimedes screw pump was also called the cochleus because it resembled the spiral sea shell of a sea animal known as the cochleus. The Roman engineer Vetruvius gives detailed instructions in De Architektura for creating a pump screw.
Starting with a wooden dowel, you draw lines dividing it into eight equal pie shapes. After dividing its surface into equal squares, you wrap a narrow strip of wood around the dowel at a 45 degree angle to the squares. The process is repeated seven times, adding additional veins for each of the points on the grid, until the helix is half the diameter of the dowel. Then you encase the entire structure with wooden slats held together with iron bands (like a barrel).
Ressler shows us a screw pump he built himself following these instructions, substituting plastic case for the wooden one.* It was typically used to remove water from ancient mines.
During the third century AD, the Romans designed a wheel and axle irrigation pump called the tympanum. Consisting of a hollow wooden cylinder, the tympanum was divided into eight wedge shaped compartments on its horizontal axis. After being scooped up by the compartments, the water exited through an outlet adjacent to the axle.
It was powered by a slave treading the outer surface of the wheel. A 10 foot diameter wheel could produce 5,000 gallons of continuous flow water in an hour.
The bucket wheel pump was an improvement on the typanum, in that water only entered small compartments near the rim. A 12 foot bucket wheel could lift 1200 gallons per hour 12 feet.
Eventually the Romans combined multiple bucket wheels in tandem. An ancient Roman contraption made up of eight pairs of bucket wheels was discovered in an old Rio Tinto mine in Spain. When operated by 16 men, it would have lifted 2400 gallons per hour a total of 100 feet.
The Bucket Chain PumpVetruvius also describes a bucket chain pump in De Architechtura. This consists of a series of brown buckets on two chain loops driven by a tread wheel.
The SakiaThe Sakia is a Helenistic era invention still in use today. With the Sakia, an animal turns a capstan and the horizontal movement is transformed into rotary motion through a right angle gearing system.
The Force Pump
The final pump Vetruvius describes is the force pump (invented in the first century AD). It was used to spray cold water on heated mine walls to make them fracture. Initially made of steel, it was re-engineered in wood (which was much cheaper).In a force pump a piston valve moves up and down in each of two cylinders. When one piston lets water in, the other forces it up and sprays it out of a spout at the top.
*Although Ressler uses a crank, it wasn’t invented until much later. In Rome a full-sized screw pump was eight foot long and powered by a man walking on the outer casing. Powered by one man it produced 2,000 gallons per hour.
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