As the chain has been rerouted for this design revision, and now goes through the cab and luggage area, that area needs to be covered.
While this could be covered with 3 interlocking panels, I don’t want to leave sharp corners in the luggage area. Instead, a single piece that uses lattice hinges to create large radius bends will curve over the chainline.
Using lattice hinges is only available to me as a result of my decision to design parts for their industrial manufacture, even if that meant made them more difficult to make by hand. This part is particularly designed for manufacture by laser cutting and the thinness of the laser’s kerf means it would be difficult to make by any other method. However, the single piece part could be replaced by a three-pieces that would be easier to make by hand, could be bent without lattice cuts or the number and size of the cuts could be changed for a wider kerf.
Two sets of cuts make the lattice hinge, one offset from the other so when they overlap, the material zig-zags to provide the living hinge mechanism. The thin, long sections of the zig-zag will twist along the axis of the bend, so the flexibility of the material allows the sheet to be curved, without breaking or permanent deforming the material.
As the bend will be supported on all sides, there’s no need to have the overlapping lattice extending the full length of the bend so, to reduce the length (and time) of the cuts, there are 5 hinge areas along each bend line.