In an interlocking puzzle, is the fine balance between two or more pieces that must connect to hold the complete puzzle together; the pieces are mutually self-sustaining – like a house of cards.
The aim of Interlocking Puzzles is to completely disassemble and then/or reassemble the puzzle. Both assembly and dis-assembly can be difficult – contrary to purely assembly puzzles, these puzzles usually do not just fall apart easily - often they have a "key piece" which needs to be removed. Generally, the level of difficulty is assessed in terms of the number of moves required to remove the first piece from the initial puzzle. Although his is not the only barometer as discussed by Jack Krinjen in a previous article.
We touched a little bit on interlocking puzzles in our previous blog post on assembly puzzles. Interlocking puzzles represent the most popular and comprehensive branch of mechanical puzzles – and they have their own varieties and genres and themes also. Going by Jerry Slocum’s puzzle classification, Interlocking Puzzles are a completely different classification from assembly and put-together puzzles.
With developments in technology, it has become popular, with computer powered assistance, to analyze puzzles more comprehensively. There are now a ton of tools that help you break puzzles down; this is useful to assist you in the solving and the design of puzzles.
This process was begun by Bill Cutler with his analysis of all variants of Chinese wood knots - a 6 piece bur puzzle: From October 1987 to August 1990 he analysed all 35 657 131 235 different variations and solutions. The calculations were done by several computers in parallel and would have taken a total of 62.5 years on a single computer. Burr puzzle complexity and difficulty has grown exponentially, the level of difficulty having reached levels of up to 100 moves for the first piece to be removed, this is a scale humans would struggle to grasp. You can read more about Bill's experiment on Rob's Puzzle Page.
In Jerry Slocum’s view, interlocking puzzles can be broken down into a few categories; figural (like Kumiki Puzzles), geometric (Cube and Sphere Puzzles), 3-Dimensional Jigsaws, Burr (Links, Supernova), Keychain (essentially miniatures) and Miscellaneous which categorize other varieties of interlocking puzzles that don't have a general theme. We're hoping to address some of these in this article.
For starters, you can’t really write about interlocking puzzles without starting with the classic 6-piece burr puzzle. This is the 'archetypal' puzzle and is ferociously popular across the world. It is known by a variety of names: “Puzzle Knot”, “Devils Knot”, “Chinese Cross”, “Lock of Luban” or the “Lock of Kongming.”
The term “burr puzzle” dates back to the early 20th century when it was coined by Edwin Wyatt in his book Puzzles in Wood – supposedly as the puzzle resembled the clinging burrs of plants. The traditional 6 piece burr does feature in Hoffman’s book of puzzles – termed as The Nut and this date backs to the 1890's.
The burr puzzle forms the base for many of our 3D brain teasers, the diagonal star puzzle – or as we call it “The Shooting Star”, this is one of our most popular puzzles and Pulsar, also has a burr puzzle at its heart. So flexible is the burr puzzle method that they can act as boxes – like secret box, or magic drawers.
Kumiki translates from Japanese as “to join wood together” and in Japan this is a traditional art form. Kumiki puzzles come from humble roots in Japanese minimalism. In Japanese antiquity Kumiki was taught by master craftsmen to their apprentices as a technique for building without metal parts and fasteners.
Traditional Japanese craftsmen did not use nails in building construction. The style of woodworking was made to protect the structure of a house during earthquakes and other severe weather conditions, as bolted wood fared badly when bolted.
Kumiki styles are made from interlocking pieces that were not rigid, allowing for more stable structures during earthquakes and tremors. Tsunetaro Yamanaka, was the first craftsman to apply this philosophy to the design of puzzles – they became famed for their clever, fun interpretations of real-life objects.
There are four variations of Kumiki puzzle, defined by how you solve them: Oshi (push), the puzzle has a central key piece that needs to be pushed out; Mawashi – this means there is a piece that needs to be twisted in order to complete; Kendon – requires moving a piece up to down or left to right and Sayubiki – this means that a piece needs to be twisted in order to solve it.
This Kumiki puzzle art form although not used in house construction is continued in the Yamanaka family. Japanese Pagoda and Burrs are an exceptionally ornate puzzles that can have up to 129 pieces depending on size. In general, the nth degree pagoda requires 2n2+1 pieces.
3D Jigsaw puzzles also represent a style of interlocking puzzles, these are usually termed simply as 3D puzzles as they rely on forming a completely 3-dimensional object. These can come in form of virtually anything from famous landmarks to sporting objects like footballs. They also fall into the category of Spanish sculptor Miguel Berrocal – who has produced a stunning array of art works that included puzzle sculptures – coveted by collectors the world over.
Berrocal was in bon in Malaga, the south of Spain, in 1933 and died in 2006. Berrocal has made a career out of crafting huge sculptures – however there has been a limited edition mini series that included: Mini-David, Mini-Maria, Mini-Cariatide, Portrait de Michele, Mini-Zoraida and Mini Cristina. You can read more about Berrocal here.
To complete the set on interlocking puzzles, we need to explain some of the miscellaneous groupings. There are different puzzle groups that are not particularly popular that don’t fall into the basic framework including: ‘coordination motion assemblies’, which are usually complicated puzzles where all the pieces need to be moved in a coordinated fashion to achieve assembly or dis-assembly or Cube-and-Plank: a variety of cubes that are joined to straight planks, the blanks for the spine of the puzzle that usually turns into a cube upon completion – flash cube for example is a Cube-and-Plank puzzle.