Calculating the power of a screw and lever
Pen rule for finding the screw's force from its half-diameter and the length of the lever
Continuing the study of the screw with the notebook inverted, this pen page gives the rule for the calculation. Line a o is multiplied by line o p, the product multiplied again by the number of parts of the screw's half-diameter that fall along the length of the lever, and the whole then divided. Below, a screw with its rectangular nut is drawn engaging a long horizontal, graduated lever bar lettered n at one end and m at the other.
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Screw driving a graduated lever bar
A helical screw passes through a rectangular block or nut and engages a long horizontal bar divided into equal segments and lettered n and m at its ends. It forms a screw-and-lever mechanism for raising a load.
Rule combining the screw's half-diameter and the lever
To find the effect, a o is multiplied by o p, and the result multiplied by the number of parts of the screw's half-diameter that lie along the lever's length, then divided. The half-diameter and lever length together set the mechanical advantage.