Belt-Driven Machine with an Output Calculation and Glue Recipe
Dated 2 January 1496: a reminder to make the strap, a leather paste, and daily-to-yearly earnings.
Dated 2 January 1496, this leaf pairs a working reminder with a mechanical study and a profit calculation. A rotating belt runs between two pulleys above a large machine shown in cross-section, its shaft ending in winding drums, and Leonardo gives a recipe of fish glue dissolved in strong vinegar for cementing the leather strap. A long reckoning converts the machine's hourly output into daily, monthly and yearly earnings, ending at 60,000 ducats a year. Further faint notes appear elsewhere on the sheet.
On this page
Rotating belt and horizontal machine
At the top a continuous belt runs around two end pulleys, and below it a large machine is shown in cross-section with a horizontal shaft carrying a winding drum at each end, set on hatched masonry supports. The figure is captioned as a rotating belt and a machine. The number 22 and the figure 100 are written on it.
Fish-glue paste for the leather strap
To make the paste, Leonardo dissolves fish glue in strong vinegar and works it into a paste with which the leather is stuck, judging that it will hold well. The recipe serves the leather belt (soatta) that drives the machine.
Reckoning of the machine's earnings
One hundred cycles an hour at 400 per cycle gives 40,000 an hour, and in twelve hours a day some four hundred eighty thousand. Reckoned at 5 soldi the thousand, this comes to a thousand lire a day, twenty thousand lire a month over twenty working days, and two hundred forty thousand lire a year, which Leonardo equates to 60,000 ducats.
Reminder to have the strap made
A dated memorandum for the morning of 2 January 1496 instructs that the strap (soatta) be made and tested. It reads as a note to self scheduling the next day's work on the machine.