Linkages that Convert Lifting into Sliding Motion
Bar m n driven back and forth by g, and the varying effort to move shaft o p
The upper linkage is annotated so that when the crank g is raised, f rises and a moves toward f, driving the bar m n straight and flat toward f g; lowering g returns m n to its first position, so raising and lowering g moves the bar this way and that. The lower study asks how the effort of the mover varies as the raised bar m n turns the shaft o p crosswise. Leonardo prescribes measuring the distances from the pole d to the perpendicular c and from that pole to e, noting their difference (the excess t e), and observes that the motion at e no longer occurs between equal angles as it does at c. The sheet shows three jointed bar-and-crank mechanisms in pen.
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Raising g drives bar m n back and forth
When g is raised, f also rises and a rises and moves toward f, so that the bar m n moves toward f g straight and flat. When g is lowered, m n returns to its first position, and thus raising and lowering g moves the bar m n this way and that.
How the effort to turn shaft o p varies
When m n rises, the shaft o p moves crosswise. To find how the mover's effort varies, measure the space from the pole d to the perpendicular c and likewise from the pole to e, and note the difference in length, the excess t e. Note also that the motion at e is no longer made between equal angles as at c.