Analysis of Approximate Four-Bar Straight-Line Mechanisms

Abstract

Four-bar linkages possess many unique advantages as straight-line mechanisms. Formulations involving linkage geometry and curvature theory are developed to yield the lengths of the approximate straight line for specified accuracies. Design data such as link dimensions, transmission angles, and crank rotation angles are also obtained. Classical mechanisms including the Watt, Evans, Chebychev, and Roberts types are analyzed and compared. More detailed data, including a design data chart, are presented for linkages based on a Ball-double Burmester point.