In his 1989 book Penrose Tiles to Trapdoor Ciphers, and most of the key puzzle authors mention the puzzle. de Boer, and work by Tom O'Beirne and Arthur Cross, There have been sporadic fits of research into the six-piece burr, including an extensive analysis by hand by the Dutch William (Bill) Cutler has performed (starting in 1975)Īnd the statistics cited below are based on his analysis. Overall set of possible such pieces (of a given length), and interlocked in a characteristic 2x2x2 Often but not always distinct, selected from the The burrs in this section are composed of six such pieces, One can visualize an individual burr piece as being composed of unit cubes arranged in a 2 x 2 x 2 n prism where n is greater than or equal to (and usually) 3.Ī solid piece will contain 24 unit cubes, and other piece types will have some of the cubes removed, resulting in notches. In the burr shape there are 32 internal cube positions where the pieces would overlap, The burr shape is tricky to envision without an example in front of one, but it gets easier with practice. See above layer-by-layer diagram of an assembled burr - the internal cubies have dotted borders.
