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Laying Out Cams with String

T

HE EASIEST WAY TOdraw a cam is to use the unwinding string
principle—tie a string around a cylinder of suitable size to create
the desired cam shape. Aluminum food cans are often about the right
size. First, tie a length of string around the can, and tie a loop in the
end of the string. Then wind the string fully around the cylinder, and
place a pencil in the loop with the point where the cam is to begin.
Unwind the string by moving the pencil away from the cylinder. The
point of the pencil will scribe a cam that expands in proportion to the
diameter of the cylinder. Because the distance from the center of the
cam increases at a constant rate, the resulting cam will have a smooth
and controlled action.
—E. W. CARSON,Blacksburg,Va.

CHAPTER SIX

As string unwinds

from can, the pencil

will draw a smooth

cam shape.