Jin H Kim wrote:
I believe that the eastsheen 4x4x4 mechanism uses a 3x3x3 style mechanism inside. The four inner cubes of the 4x4x4 overlap the center square portion of the 3x3x3.
The Eastsheen 4x4x4 is just like their 5x5x5 internally, but with some pieces reduced to the barest minimum (which makes assembly quite fiddly). The face centres of the 4x4x4 are extensions to the pieces diagonally adjacent to the 5x5x5 face centres, which they overlap.
It is an interesting way to do the 4x4x4, but there are a lot of hidden moving parts, so it wouldn't get my vote for elegance.