I was browsing the net before Christmas and came across an engineering puzzle, the restricted nut, reasonably impressed with that but disappointed that it was actually a cheat rather than a puzzle, I started searching for potential engineering puzzles maybe even for my dad`s Christmas present – I like to make him something if I can (he is one of the only people who appreciate time spent engineering). I came across a smart little puzzle, it was an aluminium cylinder in which you had to remove the top…obviously something was restricting it. The website I found, the bloke had just made a recent post mentioning that he had cracked the puzzle after a few weeks of trying!! I emailed him and asked if he could tell me any more about the puzzle and he replied very willing to help me out. It took a while but I eventually got the concept in my head and started to draw up plans…

I have since found the inventor of this puzzle is William Strijbos and after making contact with him and having a good conversation I decided with respect to his excellent idea that I would remove any details which give a clear clue to the puzzle solution! For further details please contact me or William Strijbos. His puzzles can be purchased here: http://www.puzzleworld.org/puzzleworld/toc.asp?t=_des/ws001.htm&m=des/ws000.htm

So … that makes this post a bit of a puzzle in itself as there are no photos or info showing how it works!!

So, without further a do, here is the Cylinder Puzzle!

PUZZLE: The aim is to remove the lid. The lid lifts about 1mm and can be pushed down but clearly a spring is lifting it back up. There is a hole in the bottom of the cylinder, about 6mm and ball bearings can be heard rattling around inside at various times! If the lid is depressed more ball bearings can be heard rolling. When the lid is not depressed most ball bearings appear to be trapped and can no longer be heard.


I did draw up CAD plans for this… but again I`ve removed them!
I`m totally new to CAD so this was my best effort! If there is anything wrong or bits are drawn incorrectly, I appologise. I really enjoyed building my parts from my own neat plans!!


So I started with this 50mm bar of ally I`d had for a while!

Started turning it down to 40mm for the cylinder base piece:

I`m still not getting on with parting, so once it was down to about 42mm I took it over to the saw and hacked a piece off:

Turned it down to size, faced it up, drilled and then started to bore out the centre:

Put it on an arbour and started to clean and polish it up:

Also drilled the little 6mm window hole at the bottom. This really has no use other than to show the ball bearings from time to time.

OK ! Forgot to take a picture of the internal groove as I was getting a bit frustrated. I had to make a new tool which took some time and then after all that never took a photo! I`ve also drilled the semi-circle at the top directly into the groove.
Idea of size:

Then suddenly thought I better think of a spring so grabbed my box of springs and found this which was a perfect 23mm diameter and fit into the bore perfectly!

Started doing the top section – drilled to support it with the centre which isn`t in for some reason in this photo:

Opened out the centre bore:

Started to cut the groove in the core of the top:

The top section, still stuck on the huge bar! So part it off? Nope, back over to my hacksaw!

Then took the top section down to size and polished it up:


All the pieces plus 2 of the 4 ball bearings. To be honest, it works of course with just one but 4 makes it more difficult. I`ve only been putting 2 in for now! It still takes me a few minutes to open it.
Top and bottom sections – spring lifts it to this height when you do get the satisfying pop when it opens!
Just a little shot showing the ball bearings in the bottom window:

And here it is, locked and loaded! It is quite a challenge getting it loaded. You just do it all in reverse of course and make sure you can`t see any bearings in the centre core, they all should be locked into the groove. The spring also serves in locking the balls up into the groove which means you actively have to be playing with the puzzle to have any chance and of course the lid must be depressed to align the grooves and allow the balls to rotate.

Finally, I`m going to give it one more polish and then take it to the engravers. I gave it my dad for Christmas and so I`ll have his initials with 2010 engraved. I`ll have one engraving on the top piece side aligned with the top groove and then one engraving on the bottom piece, 180 deg from the bottom hole. So the engravings will also have a bearing on the solution which should add a nice little addition.
Well hope you enjoyed it. It works really well and it would be nice to see a few more made!!
An update on the brass puzzle MK2 :
I purchased this huge bar of square brass in Sept 2009 from the scrap heap!

It was a 6 foot length of 38mm square bar. I chopped it into 3 x 2′ lenghts just to allow me to store it. Finally thought this project was worthy of using a slither or two so I hacked off a couple of inch from one end.

Held it in the four jaw chuck and turned it round! I was expecting some hastle here which is why I`ve never really used it. With my round profiling tool it was like cutting butter:

Then drilled it with my big 15/16″ drill:

Reground my internal grooving tool, 😀

And started the groove:

Then used my nice new birthday prezzy from my wife (notice the make!!) to hold in my mill while I cut the top circle.

So from a block of brass to a puzzle bottom cylinder!

Next onto the interesting bit, my new idea for the centre shield!

————Part 3 ———–
Bit of an update for anyone interested. My aluminium one has been returned from the engravers and looks great. I`m well chuffed with it and I just hope my Dad will be. As was always my original intention, the engraving forms part of the puzzle. Without it the puzzle is actually just luck and trial and error even if you know how it works. By putting the engravings in a relation to the hole and semi-circle slot, you can discover how to align them to open the puzzle. The engravings have to be 180deg apart to open the hole and allow the balls to escape.

I`m also really really chuffed as I`ve just finished my second MK2 modified puzzle and can confirm that it makes the puzzle near impossible without some way of understanding how it opens. Infact, it is more or less a lock!! :smart:

So the base piece was done last week and I posted pictures of that earlier. Here are the rest, showing the other couple of pieces:

So I turned down another block of brass so that it fit into the bore of the base piece :

And then started making the grooves and such like last time:

This time, when I started drilling for the bore, I drilled right through 6mm, but then decided it wasn`t wide enough and moved from the plans, changing it to 10mm through the lid:

Then I started making the “extra” shielding piece:

Bored it right up, about .5mm away from the top where it will reduce down to the lid diameter:

Drilled the escape hole and then cut the thumb notch in the top:

So before polishing BUT just incase I couldn`t get them apart again, thought I`d take a pic of all the bits:

This is how the extra thumb screw looks in the lid, the spring allows it to be depressed by about 5mm and of course turned.

And here it is:

I`m really chuffed with it, it is very hard to open as the inner shield has to be perfectly aligned to allow the balls through even if the other bits are in line! I must admit however, that I`ve made a small error and took the inner groove 1mm too high towards the top so this allows it to open about 1.5mm, which is a bit more than I`d like. I think it`ll take some 8mm bearings rather than the 7.5mm currently in it so for £2 I`ll order some and see if they fit (without any more modification) and if they do, it`ll reduce the gap a bit. Anyway, that is being critical, it works a treat and doesn`t lift too much that it spoils anything!

I hope you like this second edition, certainly a fun upgrade if you find anyone who can open the first puzzle! Just need to polish up the brass and it`ll be a winner.

Part 3

I initially posted the full write up, solution and plans on madmodder and was really impressed by the interest and response. One of the skilled blokes over there, Slowcoach, made some excellent computer images of the puzzle and has allowed me to share them here:

Another member of the madmodder site, Bill Todd, made this excellent key ring size puzzle from 316 stainless steel!