A while back, I had designed a 3D Skull using Burr Tools. I planned to use this design but there was only one (major) problem; I could only fabricate the steel pieces by laser cutting. Which meant that I could only cut on flat sheets of steel, not in 3D shapes like those done by CNC machining. Given this limitation, I had to re-design my Skull entirely.

After a week or so of designing on and off, my ninth revision resulted in my “final” design. With the help of my friend and fellow puzzler Rex Perez who created the design in DWG format, I was ready to have Skull fabricated. The plan was to use 5mm thick 304 stainless steel like the Dirty Dozen. Completed and assembled, the puzzle would measure about 55mm x 35mm x 30mm. I took the opportunity to try out two other metal cutting vendors instead of the one who did the cutting for my Dirty Dozen. Files were emailed and payments made. A week later I received 25 loose pieces from each of the vendors.

The 3-unit locking piece that goes right through and into the top of the skull

Skull with shaky bones

The first prototype from Vendor A was a dismal “failure”. The tolerance was so tight that the pieces could not fit at all. I could use a small file to sand down the pieces, but too much work. Wasted effort and money. The second Vendor B’s work is what you see here. All 25 pieces fit nicely, but with a bit too much free play between the pieces. A lot of shaking and rattling! Rex commented that the power output of the laser may have been too high. Thus “burning” away too much metal, making the notches and grooves bigger than intended. But at least when assembled, a semblance of a skull comes into play. You can recognize that the puzzle is a skull afterall. Another saving grace is that with the little 3-unit locking piece in place, none of the pieces will fall apart even when shaken hard.

As of this post, I have just finished design revision #14. A much improved design with re-shaping almost every piece. In fact its now been reduced to 24 pieces only. See the screen shot of the Burr Tools file shown here. In theory at least, the whole puzzle is better reinforced and supported and should not shake and rattle so much if the tolerances are improved. I will go for a second prototype. Have to explain to the fabricator how the pieces are supposed to work (they have no idea what the pieces are for!). Hope this one will turn out better.

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I have been very fortunate to get my hands on Shane’s Haleslock 2 and Haleslock 4 previously as well as a couple of his other non-lock wooden puzzles The Circle and Turn The Plug. All fantastic puzzles! The Haleslock 3 comes to me courtesy of Peter Hajek during the IPP37 Puzzle Exchange in Paris last year.

Shane has based his Haleslock 3 on one of these old lever padlocks. The lock comes with a key and has a shiny brassy looking front plate with a little sliding door. Externally nothing very unusual about the look and feel of the lock, so Shane must have done something to the internal mechanism to make it a puzzle lock.

simple elegant solution…but damn, i am nowhere near!

Having played with Shane’s Haleslock 2 and 4 (and a number of Popplocks), I thought I would have more experience and figure out this one pretty quickly. But apparently not. The key goes in as one would expect and even turn in both directions. At various points there is resistance when turning the key and this was all I managed to find out and the progress I made. Which was not a lot.

I tried the usual prodding of the rivets, maybe something would move (a trick I learnt from one of the Popplocks) but nothing budged. I also examined the lock a lot more closely after my “slip-up” with the Haleslock 2 but there was nothing unusual I could find.

After spending the better part of several days on and off trying this and that without any success, I threw in the towel and emailed Shane for a clue. Over the course of our email exchanges, I realised that the clues he shared with me were already some of the things that I had done, but perhaps not “far reaching enough” or the right way. Finally after some more trying, wa-lah… the shackle unlocked.

Like most puzzle locks, you cannot see the internal mechanism with the lock in the solved state. Re-locking the shackle were the steps in reverse. And I was able to do it without a cinch.  Essentially, the solution lies in just a few steps…of course easy to state now on hindsight. A rather elegant solution I might add.

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