The Atlantic Codex

Top left block

This is the method for ensuring that a
movement, through its interrupted motion Leonardo refers to the rhythmic engagement of gear teeth,
is very strong by means of a toothed wheel which is
moved by a perpetual screw perpetual screw: a worm gear, where a threaded shaft turns a wheel by means of a "fish" original: "pesce"; likely a technical term for a specific gear tooth shape or a pawl
or rather a wheel made of many teeth situated perpendicularly
to its circumference; this wheel,
through its revolutions, maintains the motion
in the manner seen here below by means of
two wheels and one perpetual screw, because the one
always gives motion to the other, and thus it is preserved
continually in its motion.

Middle right block

So, let us suppose that the perpetual screw
has to move many great weights
and performs great labor, through which
it is seen that the teeth that are in the
wheels would come to wear out quickly;
but by this method, it is seen that one
wheel has no more labor than the other,
and the forces are shared equally; for
these reasons, it is maintained for a long
time without any wear original: "consumo"; refers to the mechanical erosion of parts through friction.

Bottom right block near sketches

This is used? ...
screw? ...
This is the way that ...
This maintenance ensures that for a long time
its motion is maintained with less effort
and much more force, and thus the
toothed wheel and perpetual screw are preserved.