Gear Trains, a Bombard Hoist, and Time Reckonings
Wheels and pinions with lettered parts, a pulley note, and figures for days, months and hours
Ink sketches across this sheet lay out gear trains — wheels a, b, c and the great wheel m with its pinion — analyzing which way each turns and how their teeth come into and out of contact as they revolve. A marginal note beside a crane labels a 'wheel for going to the mountain,' a hoist for hauling a bombard uphill, and another explains that the small wheel will not turn without its cord nor the large one without its pitch. Scattered figures reckon time and distance: a thousand miles at fifty a day, twelve hundred months to a hundred years, and 365 multiplied by 24 to give 8760 hours. Numerous mechanical sketches on the sheet go beyond the transcribed captions.
On this page
A gear train of lettered wheels and pinion
The wheel a turns to the right and b to the left, c likewise to the right, while the great wheel m turns contrary to a because the square pole comes round in a circle. The pinion b has no pole of its own; the wheel m carries them poled upon one of its arms and drives them around, so that b and c revolve about a, which turns contrary to b.
Meshing and separating of the wheels as they turn
As c gives its turn and is carried to a, a goes to b and n passes under b, so that m must touch f — f coming to meet m and m to meet f, until they remain just touching. Then little by little they return to their first distance, separate, and come together again according to the turning of the wheels.
A hoisting wheel for hauling a bombard up a mountain
Beside a crane figure that lifts a bombard, a caption names a 'wheel for going to the mountain' — a hoist for raising heavy artillery over rising ground. The device is drawn at the sheet's left, one of several lifting and hauling mechanisms studied here.
Note on a pulley: cord and pitch
A margin note beside a pulley drawing observes that the small wheel does not turn unless a cord is given to it, and the large one does not turn without the pitch. It records the practical conditions under which each element of the tackle will run.
Reckonings of days, months and years
Scattered figures work out time and distance: forty days for a thousand miles at fifty per day, then 'say a month,' and twelve hundred months making a hundred years. A companion calculation multiplies 365 by 24 to reach 8760, the hours of a year.