Reciprocating motion from a one-way handle (7th species)
Pinions and a segment-wheel that make a wheel swing to and fro though the crank turns one way.
Folio 17r studies two mechanisms that turn continuous rotation into reciprocating motion. The upper device pairs a pinned lantern-pinion with a segment-toothed wheel so that, turning the handle a always one way, the principal wheel swings now one way, now the other (texts 1-3); Leonardo names this the 'seventh species of composite motions', a continuous circular motion that generates motion which continually goes and returns. The lower disc-and-crank device (handle n, wheel m) does the same, the wheel turning now this way, now that (texts 4-5).
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Circular motion generating back-and-forth motion (7th species)
A continuous circular motion generates a continuously discontinuous motion, one that continually goes and returns, as the pinion here makes its wheel do. Leonardo classes this as the seventh species of composite motions.
Handle a swings the principal wheel both ways
Turning the handle a always in one same direction makes the principal wheel turn now one way and now the other, as the teeth of the pinion show.
Handle n reverses wheel m
This lower instrument is so made that turning the handle n in a single direction makes the wheel m turn now this way, now that.