Improving the great hoist; excavation worker schemes
The Pesaro treadwheel hoist perfected, barrow-crew plans, a mill and portable sluice-gates, with sums
The verso is dominated by Leonardo's critique and redesign of a large treadwheel hoist used for excavation, together with several small plans for arranging barrow-crews and columns of arithmetic. Studying the machine seen at Pesaro, he counts the fifty 'tempi' wasted each time a box is raised and reset, faults the light boy counterweights, and claims to have brought the ancient architects' hoist 'to its ultimate perfection' with a self-returning box, while promising a still faster device. Other notes plan how forty men clear spadefuls from a ditch, and how to choke a canal and dig a harbour using water forced under portable sluice-gates.
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Faults of the Pesaro treadwheel hoist
At Pesaro four of the seven men leave the wheel to lift and reset the box, and for fifty 'tempi' the wheel does no work; a third of the wheel must be unwound to give a braccio of rope to tip the box. Over a hundred boxes that is five thousand wasted tempi. Leonardo faults the light boy counterweights (he wants no less than 200 pounds) and the fact that men walk under a third of the lever.
The self-returning box and the perfected hoist
In his design the raised box travels by itself to where it is unloaded; the man who normally pulls it back now empties it by pulling a rope that releases it, while the wheel turns, the weight rises, and the empty box drops swiftly to be swapped for a full one. 'Behold the last motion in goodness made by the ancient architects, from which I have removed every defect and reduced it to its ultimate perfection' — yet he still promises a swifter, more useful device.
Forty men clearing the ditch in tempi
With twelve barrows and twelve men with shovels, that is thirty-six, plus four in front, forty. With forty men one clears twelve spadefuls in twenty-four tempi, reckoning that in two tempi the barrow returns wholly to its place and the shovel is loaded and unloaded, so the ditch stays level. In two tempi one barrow is cleared with eighteen men, half on each side.
Digging the harbour with water and portable sluice-gates
Turning the sheet, Leonardo notes: choke the canal, then dig the harbour with the water that rushes under the portable sluice-gates. The banks are to be cut in graded steps of depth and width; an adjacent note directs the mill be used for the same lifting task.
Columns of worked calculation
Both faces carry dense columns of multiplication and addition supporting the hoist and excavation estimates — figures running into the tens of thousands (products such as 34 × 1900 and totals like 64800). These are Leonardo's working ledgers for tempi, loads and men, not abstract arithmetic.