The design question I keep coming back to is “How do I create a reliable interlocking system for blocks?” My criteria for a robust and useful system are:
- The interlocking system should allow interconnections in three dimensions.
- The pieces should snap/interlock together reasonably well/easily.
- The pieces should stay assembled reasonably well.
- The pieces should snap apart reasonably well/easily.
- The pieces should not require additional tools to be assembled and disassembled.
[...] While lego nubs are circular, the parts they fit into touch the circular nubs tangentially. For instance a nub fitting into a corner piece would be held in place by two straight sides and held against a circular tube. The picture to the right shows the underside and nubby bits for several lego (lego compatible?) pieces. This system probably works because of the exacting tolerances of real lego parts. I’m guessing they tested the nub heights and contact points to find an optimal mix of most of the same criteria I have for an interconnecting building block system. [...]