A glass-vessel spinning engine and the wear of its pivot
Rotating shaft with a needle-spindle in glass, propositions on pivot wear, and columns of arithmetic
The verso of the same blue sheet continues the workshop machinery: a central engine whose rotating shaft ends in a needle-spindle and turns inside a vessel of glass or crystal, its parts sized in ounces. Down the left side Leonardo sets out propositions on the wear of a pivot ('pole'), which has two contrary motions about its centre — one that consumes both the pivot and its support, and one that consumes neither. Columns of multiplication and division fill the lower part, one block written with the sheet turned onto its side. Many further faint mechanical sketches cover the leaf.
On this page
Rotating shaft with a needle-spindle in a glass vessel
A central machine turns a vertical shaft whose lower end carries a needle (spindle); the shaft rotates inside a vessel of glass. The scale is fixed by the note that a b measures one braccio.
Two contrary motions and the wear of a pivot
Leonardo argues that a pivot ('pole') has two motions about its centre, each opposed to the other. One motion wears away both the pivot and its support — the part that follows behind the mover — while the other, which flees from the mover, wears away neither itself nor its support.
Machine dimensions in ounces
A machine in the lower-right corner is annotated with the sizes of its pieces: a crystal element two-thirds wide, and parts of one-and-a-half and two ounces.
Worked multiplication and division
Columns of figures carry out calculations such as 22 multiplied by 6 giving 132, and 132 divided by 7 giving 18 and 6/7. A further group of figures is written with the sheet turned on its side.