Based on pictures of existing designs, I started with some sketch drawings to see if it was feasible. I might have a go at drawing up a CAD version, as I'd like to try cutting one out with CNC or even a laser cutter in the future. It would be really interesting to try it with acrylic.
This is my fist Instructable, so constructive criticism and comments are gratefully received. I'd be really interested to see if anyone else has a go at building one.
Step 1: Cut Out Parts
I used entirely materials I had lying around: some 5mm ply, some 8mm ply and some thin rope; thick shoelaces would probably suffice. As a protoype ply was fine, but I think it would look nicer in plain wood. Wood glue holds it all together, though its annoying to wait for it to set. You'll need minimal tools. I used a jigsaw to cut the wood, but a scroll saw would be better. A drill and bit of similar size to your rope is also necessary.
After a little research online, I started with some scrawly paper sketches to see if the concept would work and work out some sensible dimensions. With a puzzle of this type, accurate dimensions are quite critical. I did make one mistake, but I was able to recover it.
Skip these if you don't follow, it should all become clear in the next couple of steps.
Step 2: Cover
This step describes the cover. It consists of two boxes, one around the lid and one around the bottom of the bottle. These are held together by a loop of rope from the top cover through the bottom cover and back to be secured tightly via a hasp and staple arrangement. The rope length can be adjusted by moving the knot inside the top cover.
I should have taken a photo of the parts, but I forgot. For a wine bottle sized version, you need to cut the following wood:
1x 5mm ply 90x90mm (base)
2x 5mm ply 40x90mm (long side)
2x 5mm ply 40x80mm (short side)
1x 5mm ply 45x45mm (top)
1x 5mm ply 45x55mm ('long' side)
2x 5mm ply 35x55mm (short sides)
1x 5mm 90x55mm (long side with 'staple') *
* I made the staple a little too short and had to elongate the hole for the puzzle to work. Next time I'd make it 100mm long, and move the 22mm hole 10cm further out. This allows enough room for both hasps to sit on the staple and still get the small ball though - crucial to the puzzle!
The hasp needed to be a bit thicker, so I made this from 8mm ply.
Step 3: Locking Mechanism
Sizes are on my paper plan in step 1, but the key points are that the square must be too big for the circular hole on the top cover, but small and thin enough to fit through the hasp slot. The small ball must be too big for the hasp slot, but small enough to fit through the top cover circular hole (~15mm diameter sphere, or 11mm diameter cube if you don't round it off). The large ball doesn't need to fit through anything, it needn't be humungous, but make it large enough not to fit through the circular hole in the top cover.
I didn't have any suitable wooden balls and imagined it would be hard to get hold of the correct dimensions. So with some glue, lots of a patience and a Dremel I approximated some spheres from some made-up cubes. They're a bit knobbly, but I think it adds to the plywood 'effect'.
Step 4: Finished
I'll leave it as a small challenge for the builder (it's easier to lock than unlock), but you want it to look as illustrated when you've finished.
Having completed the project, I'm now a bit loathe to give it away. I might have to give it with the proviso that I can have the puzzle back once they've opened and drunk the wine.