A jack (martinello): cogwheel driving a toothed rack
A rack-and-pinion lifting device with pawl and hooked lever, named in the note as a jack
A clearly drawn mechanism that the note names a jack (martinello): a large cogwheel meshes with a long toothed rack, engaged by a pawl or catch and a hooked lever, with fainter framework sketches above. Letters label parts of the device. The arrangement converts rotary motion of the wheel into linear travel of the rack for lifting.
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A jack (martinello): cogwheel and toothed rack
A large cogwheel meshes with a long toothed rack, engaged by a pawl or catch and a hooked lever, in a device the note names a jack (martinello). Fainter framework sketches appear above, and letters label parts of the mechanism.