A tripled pawl tooth and its spring on a retaining wheel
Guarding against a broken detent when great weights are held by a ratchet wheel
Leonardo discusses the pawl (servidore) of a retaining wheel, noting that some makers triple its engaging tooth because a single tooth, running with or across the wood grain, could snap under excessive weight, especially on a small-circuit wheel; he approves of this safeguard for moving great loads (text 1). He adds that a perpendicular pawl needs a spring behind it to keep it pressed onto the wheel's teeth, lest it fall back and let the wheel run backward with fury, causing a conflagration among the machine's toothed wheels or a great crash. The drawing shows a saw-toothed ratchet wheel with a hanging weight and a spring-loaded detent.
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Tripling the pawl tooth of a retaining wheel
Because a single detent tooth, lying along or across the grain of the wood, has sometimes broken under excessive weight (worst on a small wheel), some makers let the servidore engage three teeth at once. Leonardo does not reject this reasoning, since in moving great weights one should make oneself as secure as possible.
A spring keeps the perpendicular pawl seated
Setting the servidore on a perpendicular line requires a spring behind it, so it stays pressed and pushed onto the wheel's teeth. Otherwise the pawl might fall backward and the wheel run back with fury, kindling a fire through the machine's many toothed wheels, or making a very great crash.