If L + S < P + Q, four Grashof mechanisms exist: crank-rocker, double-crank,
rocker-crank, double-rocker
• If L + S = P + Q, the same four mechanisms exist, but, change-point condition occurs
where the centerlines of all links become collinear and the mechanism can toggle
• If L + S > P + Q, non-Grashof triple-rocker mechanisms exist, depending on which is
the ground link, but continuous rotation is not possible
• Geometric inversions occur when different pivots are made the ground pivots (this is
simply an application of reciprocity)