Building a snake cube puzzle
So I figured this would be a good puzzle to figure out how to make. The cubes are held together by a string that is stretched through holes along the length of the "snake".
I then cut 2 cm cubes from it with my small table saw sled, using a stop attached with a clamp. I set that stop by measuring to the blade with calipers.
I started with the straight-thru pieces. These are the pieces that have cubes attached at opposite ends. I just laid my pieces on top of the puzzle I already had to figure out how many and which colour I needed, though I reversed light and dark on mine.
If you want to make your own, having an 1:1 image of an unwound cube is very useful. If you make yours with 2cm cubes, print this PDF of the image at left with "fit to page" turned off to print the image at 1:1 scale.
I clamped a piece of wood with a square notch cut near the end to the table. This helps me position each piece as I drill it.
I could just drill the holes much bigger. On the snake cube I was given, this is what they did, which is why pieces at the corners really like to slide out of alignment (image at right)
Instead of oversized holes, I decided to drill two shallow holes in the middle of the faces, then a diagonal hole to join them up. I didn't want to rely on a diagonal hole alone because it's hard to line that hole up precisely and the sharp edge of the hole might damage the string.
I did have the foresight to put a chamfer on the long edges of the sticks before I cut it into cubes so the long-grain edges were already pre-chamfered.
I wanted to put some varnish on the cubes, so I took it all apart again, and dabbed varnish on with a paper towel. I didn't want to use a brush because brushing always causes a lot of varnish to get into holes. Spraying would solve that, but I don't like to spray indoors and it's winter outside.
If I was doing it again, I'd varnish the cubes before drilling. Better yet, I'd varnish the square sticks before cutting cubes out of them so that I'd only have to varnish the end-grain faces.
So I split one of the cubes in two so I could put it on after stringing everything up.
But even with the extra cube, I had to make sure the string was in moderately tight along the whole snake. With the string going around so many corners, there's too much friction to just pull it tight from one end. So I pulled it tight a few cubes at a time, sliding the cubes to the tight part of the string, and working my way from one end to the other.
...then cut them nearly flush with the bandsaw and cut them flush with a chisel
The snake cube I was given also has plugs in the end, though you can also see the string jammed in next to the plug. So I imagine they just pulled the string tight, then jammed some glue and a plug in the ends and cut it flush.
It feels much more precise than the one I was given. But with the holes fairly small, it's much harder to twist some rotations where the corner scrapes against other parts of the cube. So if I was making it again, I think I'd make the holes a little bit larger to give it a bit more slop.
How to solve the snake cube puzzle:
I was pleased to see your post about the snake cube. Your readers may be intersted to know that the 3x3 puzzle has thousands of possible forms, based on the hamiltonian path that fills the space. The exhaustive analysis of the problem space and list of all solutions has been done at least three times that I know of, apparently the 2nd and 3rd guys didn't spend a lot of time googling before they re-solved the problem.
I have a set of the plastic Cubra puzzles described here:
Not sure if they are still sold. The green one at the link above is SUPER SUPER easy, I think because the multiple three-in-a-row sections significantly constrain the number of ways you can fold the thing up. Red is harder. I think purple is probably the hardest.
This page is a good exhaustive description of the graph theory and all the possible solutions:
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