Screw jacks and geometric sketches
Screws driven by a crank, by a man's weight, and by a wheel and windlass
The sheet studies lifting screws driven three ways: a screw jack turned by a crank at upper right, a screw pressed down by a man's weight on its long lever arms at lower right, and a screw worked by a wheel and windlass at left. Small geometric doodles - squares, a triangle set in a square, and a bisected circle - fill the upper-left corner. The captions give proportions for the threads, the windlass and the wheel.
On this page
Screw jack turned by a crank
A framed vertical screw is worked by a crank or handle at the top. Leonardo specifies its thread as '6 double [turns]' and its shaft as one-sixth thick.
Screw driven down by a man's weight on its levers
At lower right a screw is lowered by the weight of a man bearing on the top of the screw's long levers, worked by hand. The long lever arms multiply the force a single man can apply to the thread.
Screw driven by a wheel and windlass
At the left a screw is turned through a wheel and a windlass (burbera). Leonardo notes the windlass should be one-third thick and the diameter of the wheel above 2 braccia.
Geometric doodles
The upper-left corner carries small geometric figures: divided squares, a triangle inscribed in a square, and a circle split by a diameter. No caption accompanies them.