An overconstrained 5-bar with a plane of quasi-symmetry

Abstract By means of algebraic screw system theory, Waldron was able to demonstrate full-cycle mobility for classes of line-symmetric and plane-symmetric linkages. They included some classical loops as special cases. In this paper it is shown that one of Waldron's classes, the general plane-symmetric 5-bar is itself a special case of another 5-bar group, possessing a plane of quasi-symmetry, but basically defined by having two pairs of adjacent screw axes parallel.