Eccentric

Chambers's Encyclopaedia, Volume 4: Dionysius to Friction, p. 179
A technical diagram of an eccentric mechanism. It shows a horizontal shaft with a central circular disc. A rod is attached to the disc at a point that is not at its center, creating an eccentric motion. The rod is connected to a lever arm on the left, which is shown in a slightly angled position, indicating its movement as the disc rotates.
A technical diagram of an eccentric mechanism. It shows a horizontal shaft with a central circular disc. A rod is attached to the disc at a point that is not at its center, creating an eccentric motion. The rod is connected to a lever arm on the left, which is shown in a slightly angled position, indicating its movement as the disc rotates.

Eccentric, in Machinery, is a contrivance for taking an alternating rectilinear motion from a revolving shaft. It consists of a disc or circular frame, fixed on a revolving shaft or axis which does not pass through the centre of the disc. The disc is surrounded by a hoop of metal, and to this hoop a rod is attached. When, therefore, the shaft revolves, carrying the eccentric with it, the rod attached to the encircling hoop receives a reciprocating motion, just as it would do if attached to a crank in the shaft (see CRANK).

Source scan(s): p. 0188