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This is the Cast O'Gear invented by Oskar van Deventer, who has contributed with many other designs to the Cast Series, and it was released by Hanayama in October 2002. It was first introduced in 2001 at the 21st IPP Design Competition, at the time simply called, Sunflower. It can be categorized as a Sequential or Route-Finding puzzle.
It is one of the largest puzzles in the Cast collection, measuring around 9cm in height and also, one of the most interesting designs. Other large puzzles available include the Cast L'œuf and the Cast Duet, which curiously were also invented by Oskar himself.
You're presented with a gear containing five teeth, locked in a cube with six holes. Your goal is to find the correct hole path to remove the gear. Now, sequential puzzles can be considered boring, for taking too much time or because you can often find yourself in the same place you started. However, the design of the Cast O'Gear is cleverly done to intrigue you and encourages you to keep going.
Tips for the solution:
When you're trying to solve it, take a bit of time to carefully inspect it and pay special attention to the slight details and differences in the puzzle. Note that each tooth at the right and left of the main one (the tooth with the hole) has a difference in thickness. Now, take a look at the cube face that's opposite of where you started (the one with two extra holes at the edges), and you'll see that it's different from the ones at the four sides of the cube, which by the way, are all identical. That's the face you need to focus and the gear teeth that have the difference in thickness, as one of them is going to allow you to remove the gear. All that you need now, is find a way to pass the right tooth in the bottom cube's face. If you're still struggling after this, take a look at the solution here.
The Cast O'Gear is not that difficult, if you don't think about the boring part of finding the right sequence of movements... The goal is intuitive and you know what you're supposed to do, you just need time to get there eventually. Hanayama rates the puzzle at 3 out of 6 and PuzzleMaster 7 out of 10, so it's just around the middle of the scale. Returning the gear to its original position is way easier than removing it, contrary to most other Cast puzzles, mainly because you're more familiar with the puzzle's features and particularities.
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Hanayama's Factory Visit (Many thanks to Roxanne Wong for sharing these pictures)