Motions of unequal force from off-centre driving wheels
Three linkages compared: eccentric centres make force or movement unequal; the last is praised.
Three crank-and-rod mechanisms are compared for how evenly they deliver power and movement. In the first, the motion is of unequal force because the centre of the driving wheel is not at its middle, so its driving circle is not equally distant from the centre of the principal wheel. A third device is equal in force yet unequal in movement. The last mechanism Leonardo judges quite praiseworthy, both for the ease of its motion and for the compactness of the work.
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Unequal force from an off-centre wheel
The motion is of unequal force because the centre of the driving wheel is not at its middle. Its power stays unequal only because the driving circle is not kept equally distant from the centre of the principal wheel.
Equal in force but not in movement
The motion drawn below, although equal in force, will not be equal in movement.
A praiseworthy, compact motion
The lowest mechanism, a toothed wheel with a connecting rod driving a rack, is judged quite praiseworthy, both for the ease of its motion and for the brevity and compactness of the work.