Percussion of falling hammers and the gain of the screw
Falling hammers on lead, oblique versus straight blows, and the mechanical gain of a many-turn screw
Folio 188v opens with a group headed 'Moto e colpo' (Motion and blow): a 4-pound hammer dropped 3 braccia sinks a finger's depth into lead, while one of double weight from the same height sinks not twice but one and a half times as far, and the effects of a wider striking face and of a more oblique fall are posed as questions. A small right-triangle diagram accompanies the claim that the less oblique the path, the harder and swifter the blow. Further notes state that the nearer the striking part of a rod is to the hand, the weaker the blow, labelling the sketch 'mano' (hand). A closing paragraph on the screw observes that a nut of ten turns lifts the same load as a single-turn nut but bears only one pound per turn where the other bore ten.
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Doubling a hammer's weight sinks it one and a half times as deep
A 4-pound hammer falling 3 braccia buries itself a finger's depth in lead; one of equal thickness but double the weight, dropped from the same height, sinks not twice but one and a half times as far. Leonardo also asks how a wider striking face would change the depth.
The less oblique the path, the stronger the blow
Of two equal weights falling from the same place, the one whose path is less oblique strikes with greater force and greater speed. The adjoining right-triangle sketch contrasts the steep drop with the slanting one.
A blow struck near the hand is weaker
The nearer the striking part of the rod is to the hand that moves it, the less powerful the blow. The little sketch of the hand is labelled 'mano'.
Screw and nut: more turns, less load per turn
If a single-turn nut lifts ten pounds, a nut of ten turns lifts the same weight but takes only one pound per turn where the first took ten. The many-turn thread trades revolutions for effort.