Introduction: Treasure Chest Puzzle

About: I love science, electronics, programming, and making. Visit my website ^ for more info.

PLEASE NOTE: I never found the time to finish this Instructable, or the project. I probably shouldn't have published it in the first place. Now that it's here, I'm going to leave it, but please know that it's more of an idea than an actual working product. Anyway, feel free to take my files and adjust them until they work properly, if you want to!

A few weeks ago, I found a cool 3d-printed puzzle on Thingiverse called The Impossible Puzzle (links are below) which was a plastic cross with a ring, and the goal was to remove the ring from the cross. This could be done by spinning the cross, which "unlocked" the cross and allowed you to take it apart so you could easily get the ring off. In my opinion, it was one of the coolest things I had printed so far with my 3d printer (which I recently got), and I became very interested in 3d-printed puzzles. Soon after that, I saw a video on YouTube about the Lotus Puzzle, which I thought was really cool, so I decided that it would be fun to design my own "sequential discovery" puzzle using some of the same concepts. This puzzle is the result. It is also the hardest thing I've ever modeled in Fusion 360 (which I recently learned) so I learned a lot while designing this.

The Treasure Chest Puzzle is really 6 puzzles in one, and you must solve them all to find the "treasure". This puzzle is very, very difficult to solve the first time, but after you solve it once, it's easy to solve it again. The Treasure Chest Puzzle is really 6 puzzles in one, and you must solve them all to find the "treasure".

Unfortunately, I didn't have time before the deadline for the Puzzle Challenge to take pictures of the full assembly and working puzzle, but hopefully you like the idea and hopefully all my files (which are completed) are helpful for you in case you want to build this puzzle. Hopefully I'll have time soon to add a video of the completed puzzle!

Step 1: The Design

First of all, I'd like to mention few designs that gave me inspiration for this puzzle. Specifically, Thingiverse user David Mussaffi's Impossible Puzzle design, cnorth's Dove Tail Puzzle Box design, and the Lotus Puzzle (specifically this video).

I started out by designing this puzzle on paper, and then I built a model of the design in Fusion 360.

The Treasure Chest is a "sequential discovery" puzzle, in which you have to solve multiple puzzles in one, and as soon as you solve one part of the puzzle, it reveals the next part of the puzzle. I have organised the inside of my puzzle into three "layers", which are flat plastic pieces which contain the mechanisms for that part of the puzzle:

  • L1 - this layer sits at the top inside my chest and holds the lid down, using two rods which latch onto a latch extending down from the lid. You must spin the chest to unlock the lid. Centrifugal force causes two rods inside L1, which are holding the lid down, to fly away from each other, releasing the latch for the lid. Simply tilting the chest will not work, because as the first rod slides away from the latch, the second one will fly into the first one's place, keeping the chest lid locked.
  • L1B - this consists of three plastic pieces which can be moved by switches on the front of the chest. Each piece has a slot in it, and when they are all lined up, layer L1 can be removed from the inside of the chest to reveal the next part of the puzzle.
  • L2 - this is simply a tray that holds a "key", which is really just a M3 screw. This layer is held down by layer L2B.
  • L2B - this layer holds down layer L2 by holding onto a bar attached to it. Two springs hold the latch in place, but if the screw from the previous layer is inserted into the side of the chest and screwed into place, pulling outwards on the screw "key" will release layer L2, revealing several holes in the top of L2B.
  • L3 - L3 is the drawer at the bottom of the chest, which holds the "treasure". A latch with a spring on the side of the chest holds the drawer in place, but inserting the screw "key" from the previous step into the right hole in L2B (see above) releases the latch, allowing the drawer to be removed.
  • L3B - when you open the trick "dovetail" (it's more like a T than a dovetail) box (L3B) attached to the bottom of the lid of the chest, you will find a little "hook" that can be used to remove the drawer from the side of the chest.

At the bottom of this step is an assembled model of the whole chest (it's not printable), in case you want to examine the chest in 3D.

To solve the puzzle, you must complete six tasks (spoiler alert):

  1. Spin the chest to unlock the lid.
  2. Find the correct combination for the switches on the front of the chest to release L1.
  3. Insert the "key" into the side of the chest, screw it in, and pull outwards; to release L2.
  4. Insert the "key" into the correct hole in the top of L2B (inside the chest) and push it in to release the drawer.
  5. Slide the lid of the fake "dovetail" box attached to the lid of the chest sideways diagonally, and remove the hook from within.
  6. Insert the hook into the front of the drawer at the side of the chest, and pull the drawer out.

Step 2: Materials and Tools Needed

All you really need to build this puzzle is a 3d printer (I used an Anet A8) with filament (I used PLA). You also need one or two small springs, which you can easily remove from a retractable ballpoint pen. Just unscrew a retractable pen (you'll need the kind that you can take apart) and remove the spring from inside. Finally, you will need one M3 nut and one M3 screw (at least 28mm long), and a glue gun or other similar glue.

Please keep in mind that while assembling the parts of this puzzle, you may need to sand, cut, clip, or add glue/tape to parts of the puzzle to make the pieces fit together properly.

Step 3: Printing and Assembly: the Chest + L2B Latch + Drawer

Because you need to access the inside of the chest to attach the springs, and possibly adjust stuff, I cut one side of the chest off in the model. Fortunately, this also makes it easier to print. I recommend printing the chest on one side, with tree supports. (If you are using cura, tree supports are in the "experimental" section in the print settings.)

Also, for all prints for this chest, if you are using cura, I recommend setting "slicing tolerance," in the experimental part of the settings, to "inclusive." This will ensure that parts of the chest with any diagonal surfaces fit together properly.

Print the L2B latch like in the picture, with supports (it doesn't matter which kind).

Once done, slide the L2B latch into the side of the chest, with the tabs on the side of the latch sliding into the slots in the middle of the chest. Make sure that the side of the latch with the hexagon is at the open side of the chest, facing down (in the pictures I made a mistake - the hexagon part should be below the rest of the L2B latch). Then, take an M3 nut and place it into the hexagon. Glue it in place.

Print the drawer with the flat side on bottom. You might need to do some sanding to get it to fit in the bottom of the chest.

For some reason, the drawer doesn't render properly when you click "view in 3d" below. It will look like the drawer after you download it, though.

Step 4: Printing and Assembly: L1B + L1B Switches + L1

Print the L1B layers (you need 3, so L1B.stl contains 3). If you own a very small printer, I included a single L1B layer, which you can print 3 of. Then print the L1B switches and L1.

Take a look at the pictures (renderings) above to get an idea of how the parts fit together.

Basically, the three L1B layers should sit inside at the top of the chest, on top of the rails on either side of the inside of the chest, and the switches should be glued onto them (one switch onto each L1B layer) so that the switches come out the holes in the front of the chest. Glue them so that when the switches on the front are in a certain position, the notches in the L1B layers line up. Then place the L1 piece on top of the L1B layers so that the hooks on the bottom slide through the notches. The switches on front should now act like a combination lock - when the right combination is set, L1 can be removed.

Step 5: Printing and Assembly: Trick "dovetail" Box + L2 + Drawer "hook"

Print the two pieces of the trick "dovetail" (as I said earlier, the box uses "T"s, not dovetails) with one of the sides at the bottom. In cura, make sure you have "slicing tolerance" set to "inclusive." Slide the two pieces of the box together.

Print layer L2 and place it inside the chest, on top of L2B. Pull the L2B latch all the way to the side that the M3 nut is on first. Once L2 is in place, push the latch back so that it latches onto the hook in the bottom of L2 and holds L2 in place.

For some reason, the drawer "hook" - used to pull the drawer out of the chest - didn't turn out as expected for me, but it mostly works anyways.

Step 6: Printing and Assembly: the Side of the Chest + the Lid + the L1 Poles + L3 Latch

Unfortunately, I don't have pictures or detailed instructions for assembling the rest of the chest. I'll include the rest of the files here, along with a brief description of how to assemble them. Ask me in the comments if you have any questions or want any of the Fusion 360 files to edit. The assembled chest (treasure_chest FULL.stl) is attached for reference (it's not printable).

  • Chest_side - glue this onto the empty side of the chest.
  • L3_Latch - slide this onto the longest pole on the side of chest_side. glue the end cap (the little round piece) onto the end of the pole. Attach a short piece of spring between the underside of the left side of the latch, (when viewed while attached to the chest_side), and the platform directly below it.
  • L1_poles - you only need to of the poles - slide them into the hole in the side of L1 then plug the hole shut with a little glue.
  • Lid - glue the side of the lid onto the rest of the lid. Insert the joint on one side of the lid into its opposite part on the chest, then insert the other joint (the really small part) into the other respective opposite part on the chest and glue it onto the other side of the lid (that was a confusing sentence - see the full design for reference)

Step 7: Conclusion

I hope you liked this design/idea!

Like I said earlier, hopefully I'll be able to add a video/more pictures sometime in a few days/weeks, so you can see how the completed chest works - but anyways, I hope this design inspires you to create some cool puzzle; or if you do try making this, I wish you luck and please leave a comment if you have any questions!

Fusion 360 files for the puzzle may be available on request, in case you want to modify my chest - just leave a comment explaining why you need them.

Also, feel free to check out my website. It sometimes has other little tutorials/ideas/stuff that I don't have on Instructables.

Thank you!

Puzzle Challenge

Participated in the
Puzzle Challenge