Eccentric Cam

Cams with complex profiles can be complicated to manufacture, particularly with the type of equipment available in the school workshop. However, if all that is required is to produce a single up and down motion for every revolution on the cam, a circular cam rotating about a point offset from its centre (i.e. eccentric), will often suffice.

An Eccentric Cam would normally provide the follower with Simple Harmonic Motion - (this can be defined as the projection of a point on the diameter of a circle as it precesses around it with constant angular velocity).

Note that the cam follower need not just move up and down in a reciprocating motion, but it can be a lever as shown, which will produce oscillating motion.