Machine for cropping woollen cloth with paired beams
A cloth-shearing frame: cloth wound between beams m and n while automatic shears crop the nap
The large central drawing shows a cabinet-like cloth-cropping machine in which woollen cloth is stretched and wound between a lower beam m and an upper beam n by means of a central spool r. Along the top Leonardo details the automatic shears whose cut is regulated by wires, a lever a-n, a levelling wedge m and a return spring. He adds working notes to build a model, to keep a small measuring rod at hand, and to conceal the driving mechanism of the shears.
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Winding the cloth between beams m and n
The cloth is fastened to beam m along a row of little loops, like an embroiderer's frame, then held taut and wide at a-b. It is wound almost entirely onto beam m while the far head stays at a-b, after which a cord draws it to the loops fixed on the upper beam n, and the cropped cloth is gathered onto n by the middle spool r.
Self-regulating shears with wedge and spring
Along the top margin Leonardo works out the shear action r a o - f t - c h - m - n. Wire a-r, acting through lever a-n, first pulls the levelling wedge m out of the shear's stirrup; two further wires then close the blades. A nail at f and a bendable lever f-a keep the cut o-t from biting into the nap, and on opening a spring pushes back under the wedge to level the shears again.
Notes on the model and its concealed drive
Beside the central figure Leonardo marks the correct arrangement (A is good, not A; d c b a; a b c d be the model) and reminds himself to make a small measuring arm for gauging every detail. A separate container of screws and cylinders is labelled a-b as the way to hide the secret of the first motion, since a-b covers the part that drives the shear heads.