# Christmas Present Puzzle



## Inferno (Apr 23, 2020)

I have about 8 months to get this done. If I really decided to do it all at once, I could do it in a day. But this will be fun to add and modify as I go. 

My son likes mechanical puzzles. Most of the lower level ones he's seen or done. If he gets stuck he will cheat and look it up online. 

What better present for him than a new, unique, puzzle? Inside will be a prize, similar to the one he put inside a puzzle he made for me. $100 bill. 

My plan is to get an aluminum rod. I think I have some 2.5" stuff laying around. That will be good enough to start with. 

I'll cut two identical halves. Inside one half will be a small pocket for the prize. 

The puzzle will be a simple "screw it apart" puzzle. I'm thinking I could do a left hand thread to throw him off. 
There will be a center stud to hold it together. 

So, the two halves will just unscrew to open it. 

EXCEPT

After I add the center stud, I will drill a small handful of holes around the center stud. All the holes will line up to the other half so when its screwed together you'd see straight through. 
Some will be threaded, some will be straight out plugs. 
Each plug will have a small hole in it. Maybe 1/16" or smaller. 
Each threaded hole will have set screws, also with a hole drilled through it. 
Every hole will either be plugged, or set screwed. Some will have the set screw put in BEFORE the two halves are put together. They won't be able to be unscrewed at all unless the two halves are separated. 
I'll mix brass, stainless and "other" materials for the plugs/set screws. 

So, the whole idea is to lead him to believe that if he removes the plugs then he can simply access the prize. The trick will be that, under the plugs and set screws will be a spring, and a pin. When the two halves are put together, the pins will fall into the opposing hole and lock the two halves so they can't turn. And all the plugs and most of the set screws will be permanently in place. There, simply, won't be a way to remove them. 

The small hole in the plugs will be so he can access the pins to push them out of the holes and turn the two halves apart, theoretically, since it will be left handed threads. If he were to know the threads are left-handed, and pushed in all the right pins with a small handful of pin tools, it will come apart. 

To add a little variety, some of the pins will be so when he pushes against them, they will engage instead of disengaging. 

Some holes will have blind plugs that serve no purpose other than to make him think they serve a purpose. 

I have 8 months. 

Stay tuned. 

P.S. I fully expect him to resort to a sledge hammer.


----------



## tjb (Apr 23, 2020)

That sounds interesting.  I'm having trouble visualizing the puzzle on a first read.  I'll need to read it much more slowly in subsequent passes.

I have a grandson that would really get off on this kind of thing.  Awards just came out for the school year, and he won three first place math awards (11th grade).  He's likely going to be a prospect for an engineering major in college.  He's very good with these kinds of puzzles: along with a few of his friends, he designs cryptographs that are amazingly complicated.  In his spare time, he does competition Rubik's cubes - his record is about 17 seconds/normal, and he's down to (what he considers an abysmal) three-and-a-half minutes/BLINDFOLDED.  I can't do it in half a day with eyes wide open and with him coaching.

Please keep posting on your progress.  Time permitting, I may try to copy it (if you don't mind).

Regards


----------



## Inferno (Apr 23, 2020)

I'm probably going to have to do a quick Solidworks sketch to keep it going in the same direction until it's done. 

Once the basic sketch is done, I'll post it here. 
I don't mind if it's copied. 

One of my employees said he wanted to see it when it's done which made me realize that I could add a "key" so I can solve it in seconds. Without the key it could take a while. 
This adds a layer of complexity in that my son will insist it can't be solved but I could take it into another room, solve it, and then put it back together. 

It would drive him nuts.


----------



## vocatexas (Apr 23, 2020)

I'm sure you're familiar with Joe Pieczynski. He hold a world's record for a mechanical puzzle. You might like this video:


----------

