A variant double-spherical linkage and its reciprocal screw

Five- and six-bar linkages are formidable subjects for mobility analysis. Apart from those loops that arise through inspiration or hybridisation, success in isolating a new solution is generally only possible now under imposed and significantly simplifying geometrical constraints. Presented here is a modest example of such an approach, suggested by linkages already discovered. The establishment of mobility criteria is assisted by an examination of the single screw reciprocal to the screw system defined by the loop's articulations. Although the resulting kinematic chain is a minor extension of a known six-bar, knowledge of its existence is a worthwhile achievement, along with the elimination of ineligible sets of constraints.