Bao Sihe's Hypothesis
According to Liu Xianzhou, in 1948 Bao Sihe wrote an article, "The Study
of the South-Pointing Chariot", in which he inferred that Yen
Su's south-pointing chariot has a transmission system like that shown
below.
The function is described as follows:
...the central distance of installation between gears 5, 6 and 7 should
be greater than the theoretical central distance. When the chariot moves
forward, gears 5 and 6 do not mesh with gear 7. When the chariot turns,
the shaft tilts and the central distance of one side gear is reduced, the
chain of gears operates, and gear 7 and the celestial figure turn together...
Source: Jingyan, Lu: Studies of the South-Pointing
Chariot: Survey of the Past 80 Years, 1996