Push-and-pull wheel motion and a weighted water tube
A wheel-driven rod that pushes and pulls, and a tube whose water keeps its height at any tilt
The large central mechanism is a 'motion that pushes and pulls': as the axle h f n carries the angle d to the rim of the wheel at h, the little rod m d is thrust outward, and as d reaches the wheel's center at f it is pulled back, the fixed poles S and o governing the throw. Leonardo insists the axle h f n must sit half on each side of the wheel to run well. Above, a tube-and-weight device shows water held at a fixed height by a descending lead: because the lead loses weight in oblique descent just as the water is raised by the same obliquity, tilting the instrument to any line leaves the water at the same level.
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A motion that pushes and pulls (axle h f n, rod m d)
It pushes when the axle h f n sends the angle d to the rim of the wheel at h, thrusting the little rod m d outward, and pulls when d reaches the center of the wheel at f. The poles S and o being fixed, if b goes forward with f then d goes back, and the axle must sit half on each side of the wheel.
Water in a tube held at height by a descending weight
Water standing at a height in its tube is pressed by a weight; if both weight and water move by perpendicular lines, then twisting the instrument to any line keeps the water at the same height. This follows because the lead losing weight in oblique descent is matched by the water rising by a like obliquity.
The upper wheel's axle set half on each side
The axle h f n of the wheel above must stand in this form, coming to be one half on this side of the wheel and one half on the other, if it is to work well.