REMAKING HISTORY
By William Gurstelle, Workshop Warrior
Archimedes and the Water Screw
Re-create the invention that quenched the
Egyptian desert.
WHILE STUDYING AT THE LIBRARY OF
Alexandria, Archimedes, the great mathematician of Syracuse, invented the worm screw,
a simple but effective device that provided
Egypt with a better way to grow crops. By dipping one end of the machine into a river or
stream and rotating its auger-like conveyor,
Nile Delta farmers could irrigate large tracts of
otherwise arid farmland.
The Archimedean screw was a technological breakthrough in the third century B.C.
Historical records show the device was soon
adapted throughout the ancient world and put
to use removing water from the bilges of ships
and pumping water and sand out of mines.
The ancient open-pit mines along the Rio
Tinto in southwestern Spain were perhaps the
largest of the classical world. Roman historian
and naturalist Pliny the Elder wrote that near
these silver and lead mines, “The mountain
has been excavated for a distance of 1,500
paces, and along this distance there are water-carriers standing by torchlight night and day
steadily bailing the water (thus) making quite
a river.”
The miners of the Rio Tinto made intense
use of Archimedes’ screws. The Greek historian Diodorus Siculus reported that, “By
these, with constant pumping by turns, they
throw up the water to the mouth of the pit and
thus drain the mine; for this engine is so ingeniously contrived that a vast quantity of water
is strangely and with little labor cast out.”
Today Archimedes’ screws are everywhere.
They transport liquids in sewage treatment
plants, fish hatcheries, and farmlands; they
move solids in coal mines, grain elevators,
HEAVY LIF TING
; Archimedes of Syracuse
(ca. 287 B.C. – ca. 212 B.C.),
Greek mathematician and
engineer, not only discovered
the principle of buoyancy,
the law of the lever, and the
formula for the volume of
a sphere, he also battled
Roman ships with solar
death rays and invented the
water screw that irrigates
farmlands to this day.
snow blowers, and a host of other devices.
At first glance, the manner in which the
Archimedean screw works is something of a
mystery. Why does turning the crank cause
water to rise? The best way to understand it
is to imagine placing a small ball in the screw-auger mouth at the bottom of the device. The
ball rests in the depression defined by the
curve of the screw. As the crank is turned,
the instantaneous location of the ball-holding
depression moves up the centerline of the
screw, and likewise, up moves the ball.
Calculating the volume of water moved by
a turn of the screw requires the manipulation
of many different parameters, including the
radius and angle of the screw, the ratio of the
screw’s outer and inner cylinders, and the
pitch of the blades. Further, constructing the
screw in the manner of the ancients is quite
difficult, requiring a great number of exacting
operations.
Luckily for us, we 21st-century types can
re-create Archimedes’ invention using inexpensive plastic tubing. Building a model screw
pump this way is quick and simple and has
the advantage of being easy to reconfigure, so
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