Weights on Cords and a Screw for Forcing Things Apart
The perpendicular of a weight, real and potential arms, and a demolition screw
The upper diagrams continue the statics of the balance: a weight always presses beneath the perpendicular, and two cords sharing a load carry half each, the required force set by the ratio of lever to counterlever. Leonardo notes that when a lever is double its counterlever a weight of 2 is raised with an effort of 1. Right-angle and triangle constructions relate each weight to the arm that holds it. At the foot of the page a screw mechanism bearing against a framed structure is captioned as a way of unlocking and bringing about the ruin of something.
On this page
Weight acts beneath the perpendicular
Every weight weighs down beneath the perpendicular, so the load is reckoned at the point l where that vertical falls. The rule fixes where a hanging weight must be calculated on the beam.
Two cords each carry half the weight K h
The cord a c, pulling the lever c b, sustains at the counterlever b e half of the weight K h, so that at a there is 2 of force and 2 of weight. Because a weight resting on cords gives half to each, the arm of the weight equals the arm b c of the force that sustains it, and the same holds on the opposite side.
A double lever lifts weight 2 with force 1
Here n g is the cord, m g the lever to which it is joined, and m l the counterlever bearing the weight 2. Because the lever is double the counterlever, the 2 is pulled with an effort of 1, so at n there is 2 of weight and one of force, and likewise at m.
A screw for unlocking and demolition
At the foot of the page a screw set within a framed structure bears against a beam. Leonardo captions it as a way of unlocking and bringing about the ruin of some thing.