NUT-T Coin Trap

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About: Just an ordinary person who loves #thinking and #tinkering

Once I searched coin trap puzzle on the net and this card-size puzzle showed up.

It is called The Centrale. Beautifully made yet simple, but I just can't find the inside of this puzzle. Some believe that the inside has the same mechanism like 4 Steps Visible Lock using steel balls inside.

Well, then I have my own vision using materials around me. Scrap wood, bolts and nuts. That's why I called it NUT-T Coin Trap (read : nutty) which represent T-shape bolts and nuts as the locking mechanism inside the puzzle.

Step 1: Materials

  1. Scrap wood
  2. Bolts and Nuts (2 pairs)
  3. Little piece of bamboo chopstick.

Tools I used :

  • Pencil
  • Ruler
  • Saw
  • Files
  • Pen knife
  • Wood glue
  • Power drill + 5 mm drill bit.
  • Varnish (optional)

Get your Bolts cut to 8 mm total length from the top (the head + four threads). In the making process, I adjusted everything to fit in, so the measurement doesn't have to be exact anyway.

Step 2: Cut Your Pieces

Firstly, print out the design at original size. That design was drawn with vector app according to the real size so that the bolts and nuts will fit in. Cut out all the holes so that we can use the papers to transfer the design to wood. We cut the paper at original size. When we transfer to wood -- draw the holes based on the paper -- the size will be smaller because we are drawing at the inside of the holes. That is okay. No worry. We will then enlarge them to fit the materials in (bolts, nuts, coin).

How I cut the small holes? Pen knife. Use any tools you have or you love. Enjoy your cutting time. Do it slowly. Plywood is soft and easily cut or sliced.

Details about the cutting are described below :

The bold text and bold underlined text will be used as glossaries on next steps.

Bottom Board

  • Cut the nut track half way down (about 2 mm of depth).
  • Cut the chopstick track half way down (about 2 mm of depth).
  • Cut out the finger curve.

Middle Boardsare broken down into three parts :

  1. Top Piece : Cut out the top bolt container space.
  2. Center Piece :
    • Cut the top nut container about 4 mm of depth (fit the whole nut in) from the other side (facing the bottom piece).
    • Cut off/half way the coin holder. If you choose to cut off, it can hold thicker stuff like a wedding ring (and this is what I wanted).
    • Cut off bottom dummy nut container. I called it dummy because this has nothing to do with locking mechanism. It simply hold a nut that will "clink-clank" when we shake, pretending to be a locking part.
    • Drill a 5 mm hole at the chopstick holder. This chopstick simply prevent the center piece being pulled entirely out of the system.
    • Plug in the bamboo chopstick, around 2 mm pass the bottom surface and 2 mm over the top surface.
  3. Bottom Piece : Cut out the bottom bolt container space.

Top Board

  • Cut down the chopstick track half way down (about 2 mm of depth).
  • Cut out the finger curve.
  • Cut out the peep hole (small circle).
  • Cut out the coin hole (large circle).

The Bolts

  • Previously we have cut the bolts at 8 mm total length from top (approximately the head plus four threads). If you haven't cut it yet, now it is the time.
  • File two opposite corners of the bolt to fit in the thickness of middle board. It will then have the shape of Thor's hammer :)

Step 3: The Nuts

  • Place the bottom board with finger curve on the left and nut track facing up.
  • Put one nut in top nut container on center piece.
  • Place the center piece on top of bottom board with the nut on the nut track and chopstick on chopstick track.
  • Put the other nut in bottom dummy nut container.

Step 4: Top and Bottom Pieces of Middle Board

    • Put the top piece and bottom piece of middle board in place.
    • Put a coin inside the coin holder.
    • Test moving the center piece, make sure nothing block its movement along the nut track and the chopstick track.
    • Glue the top piece and bottom piece on the bottom board.

    Step 5: Finishing

    • Smoothing the center piece with 200 grit sandpaper and then 400 grit to get a smooth movement.
    • Put back the nuts and center piece in place and put the Thor's hammers in top and bottom bolt containers.
    • Glue the top piece and bottom piece and put the top board onto them. Make sure your glue doesn't melt into the bolt containers or touch the center piece.
    • Wait to dry completely and smooth all the edges with a file.

    Step 6: Ready, Click, Ouch!

    • A label will add psychological lock because people will stick with that orientation for most of the time, therefore keep them away from solving the puzzle.
    • Put a coin in the coin holder. Ready?
    • Slide the center piece bar inside (to the left). Click.
    • Ouch! It will be auto-lock.

    If you take a look back at the design, you will know how to unlock it in few steps. This kind of puzzle is pocket-friendly and set great challenges. When they shake it, they will predict what are inside the box and the dummy nut plays its role.

    I am going to put a ring inside and hand it over to my Brother to solve it on his wedding day, December One :) Optionally you can apply varnish to get a glossy look.

    Need a solution to this puzzle? Well, I will post it in comment section only if you ask for it ;)

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    27 Discussions

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    Mastering Me

    3 days ago

    Hey I recognize that coin! Seribu! You’re not from Indonesia are you? If you are, salam dari amerika! Great instructable by the way.

    3 replies
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    chienlineMastering Me

    Reply 3 days ago

    Good eyes. Yes, I am ^^
    Salam dari Tebing Tinggi, Sumatra Utara.
    Thank you. You write great ibles too :)

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    Mastering Mechienline

    Reply 2 days ago

    Bahasa Inggris anda bagus banget. Saya belum pernah ke Sumatra Utara. Saya pernah tinggal di Manado, Jakarta, Solo dan Magelang. Kapan-kapan saya main ke sana wkwk. Terima kasih lagi utk instructablenya. :D

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    chienlineMastering Me

    Reply 1 day ago

    Thank you. Now everyone of us has all kinds of dictionary in our pockets, don't we? Saya belajar Bahasa Inggris namun saya tidak jadi sekolah di luar negri (karena situasi pada saat itu tidak memungkinkan). Maka menulis di Instructables.com menjadi salah satu media bagi saya untuk terus belajar grammar dan juga belajar bersama-sama dengan anak saya :D
    I read that Manado has many great places to visit too. Bunaken is spectacular. I hope I can visit there one day :)

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    thehoss

    15 days ago

    Ok, I've never heard of the coin trap puzzle. You have made a very good ible and I see a wonderful piece of work but, What does it do? Is there a video showing what it's supposed to do? If a video is here I can't find it, (which would not be unusual for me lol). Every time I ask a question the answer is usually right in the ible. But I can't find a video of what it does. Great ible though.

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    christine828thehoss

    Reply 14 days ago

    Google : The Centrale coin puzzle. It's the same puzzle Cheinline references in his Instructable. A guy on the website shows how to work the device. Before I watched this video, I couldn't make any sense of it.

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    thehosschristine828

    Reply 13 days ago

    Thanks Christine828. Now I know how it works maybe I'll try to make one. I don't know what kind or size the wood is for this project, yet.

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    christine828thehoss

    Reply 13 days ago

    Cheinline posted some dimensions. 5 mm for top and bottom boards, 8 mm for middle boards, 10 mm nut/bolt.

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    chienlinethehoss

    Reply 13 days ago

    Thank you @christine828 for pointing it out to @thehoss. Mine has the size of 10 cm x 8 cm, it is a little bit larger than credit card size.
    I am trying to make one smaller than credit card, but of course I have to recalculate the nuts and bolts positions, or maybe I'll switch them with pieces of wood to make it smaller ^_^

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    Thecowboywaynethehoss

    Reply 15 days ago

    I had a similar puzzle as a kid. My granny put a dollar coin in it and gave it to me.
    It's more fun than just giving the coin, you have to solve the puzzle to get the money.

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    chienlinethehoss

    Reply 14 days ago

    Unfortunately I had given it to my Brother on Dec 1, er, Dec 2 actually (that was plan B), so no video I can provide until I make another one :D

    I try to answer your question:
    * Coin Trap Puzzle means you put a coin in a container (not only a wooden box like mine but it can also a metal box, a cube shape, wood pieces with metal bars, any kind of container that can hold a coin and there is/are certain way(s) to get the coin out of the container.
    * NUT-T Coin Trap has two pairs of bolt-nut in it which are placed carefully to lock the inner piece of wooden container. The GOAL is getting the coin out from the coin hole (the large hole). How can you keep the top bolt up and the bottom bolt down to get the coin out. Remember there is also a nut blocking at the backside :)

    I will post a solving steps if requested :D
    Note :
    For those who own 3D printers, this design can be printed too. Change the bolts and nuts with plastics and make it smaller in size :)

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    thehosschienline

    Reply 14 days ago

    Ok I’ll have to wait for the movie bc I have to see what’s going on. I don’t understand but now I’m excited for the movie. Let me know when it’s posted. I searched utube and got nothing

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    christine828

    14 days ago

    Hi Cheinline - This may seem like a dumb question - - Can you tell me what depth wood you're using? It looked like thin luan plywood. But the carving depths (2mm & 5 mm) you list wouldn't work. I cut out 1/4" pieces of scrap wood, but that won't give me enough depth either. Any advice you could give will be appreciated.

    3 replies
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    chienlinechristine828

    Reply 13 days ago

    Ups! I didn't mention the thickness yes. My bad. I use 5 mm for bottom and top, and 8 mm for middle
    A 10 mm nut has 4 mm thickness, so pick any plywood that can hide it in. I am thinking of 4 layers of 4-5 mm plywood will do. You can use 2 layers for middle boards.

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    christine828chienline

    Reply 13 days ago

    Thanks so much! This info will help a lot. I'll post a photo is I'm successful!

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    chienlinechristine828

    Reply 13 days ago

    As I said, my measurement changes in the making process, but the mechanism stays as is. Nut track on bottom board is cut half way down the bottom board. The nut container on middle board should fit the nut completely that means at least 4-5 mm, so that it can escape the nut track.

    Chopstick track is also cut half way down for both bottom board and top board. The chopstick length itself can be adjusted to fit in its track.

    Feel free to ask anything you want to know and I will assist at my best. Since this project is fresh in my head and fun ^_^

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    Thecowboywayne

    15 days ago

    Great instructable! I'm going to make one.