[Nos. 17-32] Universal Joints, Out of Line Drives, Eccentrics
William M Clark
38.7cm x 38.7cm
Cast aluminum and wood (painted) on a vertical panel.
For educational use only. All rights reserved by the contributor(s) and publisher(s).
double-slider, eccentric, higher pair
An eccentric is a revolving disk having the point, on which it revolves, off the center of the disk. The eccentric is the driving force and works in an elongated yoke. This does away with the oscillating motion caused by disks which work in circular guides as in No. 23.
[Virginia Downward & William M. Clark, 1930]
[Editorís Note: This eccentric is similar to the Scotch Yoke [Model 21] except that the rectangular slider is replaced by an off-center cylinder. In Reuleaux's theory of kinematic mechanisms, the area-contact rectangular slider is called a 'lower pair' while the line contact of the cylinder against the vertical track is called a 'higher' pair. Higher pair mechanisms have fewer parts but more wear and noise. This mechanism is sometimes called a 'double-slider crank because of the sliding motion in both the vertical and horizontal directions. This model is similar to a sketch in the 1868 catalog of mechanical movements by Henry T. Brown, Figure 90. FCM]