Clock spring, ratchet teeth, and self-releasing weight hooks
Mechanisms to lower a load that frees itself the instant it touches the ground
The sheet studies clock and hoisting mechanisms: a coiled clock spring, a toothed wheel driving a hammer, and two hooked devices for lowering a suspended weight. Leonardo explains that the gear tooth a must gain a little impetus before it meets the hammer lever, and that the teeth should be spaced about a finger apart. Two schemes let a lowered load release itself on touching the ground, the second preferred because its hook m sits in a case clear of the tied bundle; a further note adds that the mover's grip should be at the middle of the weight.
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Clock spring
A coiled spring labelled 'clock spring' is drawn among the mechanisms. It supplies the driving force for the clockwork studied across these folios.
Spacing gear teeth so the hammer gains impetus
The tooth a must first pick up a little impetus before it meets the hammer lever, or the hammer's motion tires its mover. So the companion teeth of a-n should be kept sparse: a wheel one-eighth of a diameter should carry twelve, leaving about a finger's space between each pair.
Weight that releases itself on touching the ground
A hook lets a lowered weight untie itself the moment it reaches the ground. This version is judged better than the first because its hook m does not touch the tied bundle and has a case that gives it free release when needed.
Placing the mover's grip at the middle of the weight
This device (labelled n, p) is the same as the one below it, but it shows that the mover's grip should be taken at the middle of the weight. The note refines where the lifting force should be applied.