Expanding Surface Structure
The expanding modular structure shown consists of squares connected by rods. In the structure's closed state the squares cover the plane without gaps or overlaps. Cogs on the undersides of the squares ensure that all parts of the structure expand simultaneously.
The rods pivot about their end points. The pivots are connected to cogs on the other side of the squares. The relative positioning and the rotation of the cogs is identical for all squares. Hence fixing the cog position for one square fixes the cog positions for all squares.