Weights on Cords over Pulleys and the Intercentric Line
Why equal-obliquity cords share a load equally; no mover can exceed its own power
Leonardo continues his study of gravita, analysing a weight held by two cords running over pulleys and arguing that the load stays equal because it never leaves the vertical line f c during its motion. He states that cords bent at equal angles carry the weight equally at their ends, and that the centre of gravity of a suspended beam always lies on its 'intercentric' line. A closing note on gravity asserts that no mover can, in equal time and motion, generate a power greater than itself. The pen diagram at upper right shows two pulley wheels with a weight hung between them.
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A weight held equal on two cords over pulleys
A heavy body suspended from two cords stays equal in weight because it never departs from the line f c in any part of its motion. The more oblique the cords become, the more difficult the arrangement is. Labels: a, f, b, c.
Equal obliquity loads cords equally; the intercentric line
Cords bent at equal angles about a ring carry the weight equally at their ends. For a beam held by converging or diverging cords set at any obliquity, its centre of gravity always lies on the intercentric line that passes through the beam.
Twin pulley wheels carrying a suspended weight
The drawing pairs two pulley wheels over which the cords run to a central hanging weight, illustrating how the load is routed and balanced. It is a device sketch supporting the statics argument.