I just came across the lovely and unreal set of gear
constructions – that seem to work when you watch the videos. At
first I thought this was a one-off project by a student but
there seems to be more science behind the geometries of these
paradoxical gear sets. From Jacques Maurel’s explanation on his
website: “…This gear pair has been invented by Mr. Mercier of
Renault automobile company, and has been patented in 1988 – it
was to be used in a special differential providing “torque
transfer” This model below shows 2 pulleys with a crossed belt –
a knot giving a point on the belt. With a felt pen, it is
possible to point out the trajectory of this point on a disc
locked by a pin to the left pulley (red spots) and afterward, on
a disc locked to the right pulley (green spots). These spotted
lines are the involute curves, which will give the profile of
the teeth. The pulleys are turning in opposite directions. But
look at photo 4, showing a straight (non-crossed) pulleys and
belt mechanism, the 2 same involute cu