TOYS, TRICKS, & TEASERS
By Donald Simanek
The Chinese South-Pointing Chariot
Many ingenious mechanisms are devised with no “practical” purpose in mind.
They are examples of invention for the sheer fun of it. This phenomenon
occurred early in many cultures.
The classic mechanisms of the ancient Greeks
were often just toys, made to amaze and entertain.
Hero (or Heron) of Alexandria (c. A. D. 10–70) built
a coin-operated vending machine (dispensed holy
water); a clever hydraulic mechanism for mysteriously opening temple doors when a burnt offering
heated water beneath the altar; and the aeolipile,
a cute little engine that whirled around under the
force of steam, like a rotary lawn sprinkler.
But these were rather simple contrivances
compared to the legendary “south-pointing chariot”
from China. It was a two-wheeled chariot, pulled
by a horse, with a statue of a person riding on it.
The statue’s arm was extended, pointing south no
matter how the chariot moved. The chariot could
travel in curves, loops, or any convoluted path, even
backward, but the statue stubbornly continued
pointing south — but only if the ground was flat and
level and the wheels didn’t slip.
An Ancient Wonder
Though legend has this chariot invented as early
as 2,634 B.C. by the Yellow Emperor Huang-di, the
first historically confirmed version was created by
Ma Jun (c. A. D. 200–265).
Its secret was a geared mechanism inside the
enclosed body of the chariot. The differential
motion of the wheels drove the gears, which in turn
caused the statue to rotate the same angle as the
carriage turned, but in the opposite direction.
Simple to say, but not so simple to invent. In fact,
history tells us this closely guarded secret was lost
several times and reinvented, and in each case the
inventors received much acclaim.
When the chariot was shown in public ceremonies,
the mechanism was hidden in an enclosed chamber
underneath the statue. Some people supposed that
the chamber concealed a person with a magnetic
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compass, continually rotating the statue to keep it
pointing south. Some even thought a magnet could
be strong enough to turn the statue by itself.
But of what use was it? Probably only ceremonial
use, to impress, puzzle, and entertain an audience.
Some historians fell into the error of assuming it
had military uses (as the legends claimed), such
as guiding armies traveling in a desert at night, or
in smoke or fog. That’s hardly likely, as the carriage
only works well on solid and level ground (such as
a parade ground). Potholes and even small hills
compromise its accuracy quickly. Also, the wheels
must not slip or slide.
Legend even tells of a similar “south-pointing
ship,” but this goes beyond credibility, for the
mechanism requires a flat, level, and unmoving surface to work properly. If such a ship existed, it more
likely used a magnetic compass, which was known
in China during the Qin Dynasty (221–206 B.C.) and
was certainly a more practical and reliable tool for
navigation. The south-pointing chariot was not.
The chariot mechanism had 4 wooden gears,
arranged in much the same way as the differential
gear of an automobile. But it was being used backward. Additional, conventional gearing was required
to connect the differential to the wheels. The wheels
drove the gears, which in turn rotated the statue. The
Photograph courtesy of Science Museum London/SSPL