Variant worm-and-fork gear, with cast-iron screw and gear ratios
A worm-screw, half toothed-wheel and forks, a trapezoidal screw, and reduction ratios
The sheet reworks the geared mechanism of the previous folios as a variant driven by a worm-screw acting on a half toothed-wheel and forks. Alongside it is a trapezoidal-threaded screw that, the note says, must be made of cast iron, together with a detail of the central hub passing through a two-part socket. A closing note gives the reduction ratios (12 to one and 32 to one) with the diameters and shaft lengths in braccia, while an interlace knot occupies the upper-left corner.
On this page
Variant of the worm-and-fork mechanism
The principal drawing restates the device of the preceding folios as a variant: a worm-screw meshing with a half toothed-wheel that works a pair of forks. It is the largest and most finished assembly on the sheet.
Trapezoidal screw to be cast in iron
A screw with a trapezoidal (buttress) thread is drawn beside the mechanism, and the note specifies that this instrument must be made of cast iron. It is placed between the gear and an ornamental motif.
Central hub through a two-part socket
A detail of the hub between the two forks explains that the central member passes through the female socket of a single piece, while the female itself is made in two pieces. The note distinguishes the moving spindle from its split bearing.
Reduction ratios and dimensions
The closing note sets out the drive ratios: the first is 12 to one, with a diameter of one and a half braccia; the second is 32 to one, on a shaft two braccia long. It reasons that these ratios equal 6/10 because the screw is 1/8 thick and half of that 1/8 is 1/16.
Interlace knot
A looped interlace knot is drawn in the upper-left corner, of the decorative kind Leonardo repeatedly explored. It sits apart from the mechanical studies filling the rest of the sheet.