Expandable Flat Ring

Scissors joints are arranged side by side to form a flat ring. The members of the scissors are angled at the hinge to ensure that each joint can move in radially as the ring expands and retracts. At least four scissors are needed for an expandable ring, whose geometry is essentially the same as that of the rings used in Hoberman spheres. There the rings are arranged along the great circles of a sphere according to various polyhedral symmetries.