Engineering Expert Witness Blog

      Could it be that after cave men invented the wheel they moved on to invent another circular object, the gear?   Gear assemblies are found in a wide variety of applications, from tiny ones used inside wrist watches to massive ones found in aircraft carriers.

      No one knows for certain when gear technology was first employed, but we do know that gear driven machinery has been around since before the Industrial Revolution.   As far back as the Renaissance we’ve documented their use within flour milling equipment and the first primitive clocks.   Going even further back in time, Roman engineers are known to have developed a primitive gear driven odometer.   It was attached to horse drawn cart wheels and the number of revolutions performed allowed the distance traveled to be calculated.

      In fact gears have been used far longer than scientists originally thought.    In October of the year 1900 sponge divers stumbled upon an ancient Roman shipwreck at the bottom of the Aegean Sea near the Greek island of Antikythera.   Inside this wreck they found mineral encrusted fragments of an artifact composed of a bronze alloy.   This amazing discovery appeared to be a remarkably modern looking gear assembly which would come to be known as the Antikythera Mechanism.

The Antikythera Mechanism

      Analysis of the Mechanism conducted over the last 100 years has revealed it to be a highly complex device.   Still visible engraved inscriptions disclose it to be of Greek origin, dating back to about 100 BC.   As such it’s the oldest known complex gear driven mechanism in the world.   Prior to its discovery it was thought that mechanisms of its kind were not made until 1400 AD.   As to the purpose it served, that remains a subject of controversy, since many of its parts are missing.

X-Ray View of the Antikythera Mechanism

      The X-ray image reveals some of the Mechanism’s hidden complexity.   Based on detailed examination of these images coupled with engineering analysis, it’s theorized by scientists that the mechanism may have been configured as illustrated below.

Possible Configuration of the Antikythera Mechanism

      Since there’s no evidence that ancient Greeks possessed motors, such as those used in modern clocks, some scientists believe that the gears in the Mechanism were set into motion by simply turning a hand crank.   Others believe that the arrangement and size of the gears indicate that the Mechanism’s movement is analogous to planetary motion within our solar system.   They theorize further that it may have been used to calculate the positions of the Sun, Moon, and other celestial bodies.

      Next time we’ll fast forward to present day to familiarize ourselves with the basic terminology of gears and then later see how they’re used in modern devices.

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