Exploding Desktop Toys

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About: In 2016 I uploaded my first video to YouTube. It was a simple project, and my only goal was to teach myself filming and video editing skills. For the last 11 years I have worked full-time as a photographer a...

Delight children or torment coworkers with these lighthearted desktop pranks. This is an easy project that takes minimal tools and the end result always makes a lasting impression. Make sure you watch the accompanying YouTube video to see just how much my own children enjoyed these things.
You will note in that video that I use a CNC machine to cut out the parts, but don't worry, it is very easy to cut them out the old fashioned way as well.

Supplies:

Step 1: Materials, Tools and Asset Links

Here is all of the stuff that you need to get the job done, and a few extra things that might make the job easier. Look it over, check out the links, and decided what's best for you.

I have an even more detailed set of plans available on my website. It includes step-by-step instructions with photos, color-coded diagrams, measurements, a cut list, and other considerations that you might want to take into account when building these for yourself. After you've finished looking over this project here, if you still want more information you should definitely go check out the plans on my website - available here.

This project uses mostly 1/4-inch material. I used thin pieces of walnut that used to be ceiling fan blades from an old project I did a few years ago. You don't have to use hardwood though, plywood would work fine. In fact, plywood MIGHT make your life a little easier because it always tends to be just a little thinner than the claimed dimension. You want a little slop in the fitment of these pieces to make construction, and deconstruction a little easier.

Materials:

  • 1/4 inch lumber/plywood
  • 1/2 inch lumber/plywood
  • Mouse Traps
  • Thick CA Glue (hot glue works too)
  • Accelerator (if using CA glue)
  • Short Screws (just a few)
  • Heavy Gauge Wire (just a couple of inches)
  • String or Twine (just a couple of inches)
  • Wood Finish or paint (whatever you like best)
  • Leather (or something similar for hinges)
  • Short bit of string

Tools:

Step 2: Cutting Out the Pieces.

I used an X-Carve to cut out the pieces. Since I was using recycled fan blades, it was a little tricky getting everything lined up, but it made for the perfect material to get all the parts I needed. If you happen to have a CNC too, here are links to the files in Easel so you can cut them out just as easily:

Bank

Outhouse

If you don't have a CNC machine at your house, don't worry! It's really easy to cut everything out using more traditional tools. Just use your preferred cutting tools to make these shapes.

Most of the parts use 1/4 inch material - the bases need a little more mass to them, so they use 1/2 inch.

Bank -

  • Sides - (2) 4-1/2 x 5-1/8
  • Front/Back - (2) 4-1/2 x 2-3/4
  • Top - (1) 3-1/4 x 6-1/8 - cut a coin slot roughly 1.5 inches from one end big enough for a quarter.
  • Base - (1) 3-1/4 x 6-1/8 USE 1/2-INCH MATERIAL

OUTHOUSE -

  • Sides - (2) 6 x 3-3/4 - These will need a diagonal cut in them for the sloped roofline.
  • Front - (1) 6 x 2-3/4
  • Back - (1) 4-1/2 x 2-3/4
  • Door - (1) 4 x 2
  • Top - (1) 3-1/4 x 5-7/8
  • Base - (1) 3-1/4 x 4-3/4 USE 1/2-INCH MATERIAL

To cut the dados in the tops and bases, use whatever you have access to, but I would suggest a table saw or router table. Just set your fence 1/4-inch away from a 1/4 inch bit or blade, then run all four sides of both bases, and the bank’s top through.

*The top of the outhouse is slightly different. The long sides also need that 1/4-inch spacing, but the front and back are spaced out slightly different to create a little extra overhang in the front. I'd suggest putting the parts together and get your own measurements for that bit.*

Step 3: Mounting the Traps

To find the placement for the mousetrap on the bank base, hold the lid on its side then move the trap so the catch is right in line with the coin slot. Then drill a pilot hole and run in a screw to secure it to the base.

When mounting the trap in the outhouse base there won't be much wiggle room. You might have to trim the trap slightly to make it fit because not all traps are the same size. Make sure that the hammer won’t slam into the bottom of the door frame when the trap is sprung. There is such little material there that the trap could break that piece.

Step 4: Launch Pins

In order for the trap to launch the walls of the toys, we need something for the hammer to catch on when it swings by.

Set the mousetrap, then put the pieces in place one at a time and mark the locations for the pins.

Make some small blocks of wood and use CA glue (or wood glue if you aren’t in a hurry) to attach them in the locations you marked out. Their purpose is to add a little extra meat to the sides so you can put in some small screws.

Drill pilot holes in the blocks being careful not to drill all the way through, then twist in screws by hand. Put each piece into the base make sure everything lines up.

You only need launching pins in the sides and back pieces, the fronts just sort of bounce out on their own.

Step 5: The Trigger

At this point the bank is about done. To test it, set the trap, assemble the bank, and leave the front off. Try dropping a quarter through the coin slot and watch to make sure it hits the catch. If the trap goes off, you’re good to go.

The trigger for the outhouse needs a bit more work. Remove the original catch from the trap and throw it away. Use CA glue (or wood glue if you aren’t in a hurry) to attach a small block of wood with a hole through it in it’s place.

Bend a short piece of heavy gauge wire into the funny shape you see here, then slide the ends into the holes and pinch it together.

Use CA glue and accelerator to stick a small handle to the front of the door (a little dowel works well). Once it’s attached, flip the door over and drill through into the back of the handle. Turn in a short screw just enough to help hold the handle more securely, but leave it sticking out the back just a little bit.

Use something to space out the door inside the frame, then put CA glue on some small squares of thin leather and press them in place to act as door hinges.

Put the door in the base and bend another piece of wire into a tiny figure eight. Use a piece of string to connect the figure eight hanging from the door, to the catch on the mousetrap.

Step 6: Test It on Friends and Family (and Enemies)

That’s it. Why are you still reading this? Slap on your favorite finish, put these babies together and go find some unsuspecting soul to test it on.

I might suggest taking them to work and just leaving them on your desk. Sooner or later some nosy coworker will open the door, or drop in a penny and then they will curse you forever!

Thanks for checking out my project! Once again, if you feel like you need more information make sure you check out my website and get yourself an even more comprehensive set of plans that is available as a 10-page downloadable pdf. https://www.gunflintdesigns.com/product-page/exploding-desk-toy-woodworking-plans-1

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    8 Discussions

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    sixsmith

    7 weeks ago

    To quote Roy Underhill "The mousetrap can hurt unwary fingers, so you may wish to add a safety chain to stop it in the vertical position" from The Woodwright's Eclectic Workshop page 170 The Exploding Bank
    I mention it because that book is where I first learned about the exploding bank many years ago, I was a teenager but had a number of little nieces and nephews whos fingers I was concerned about so I added a bit of wire to my bank to keep the trap from fully closing :D

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    Arbormakes

    2 months ago

    This is amazing.
    I have never seen a better prank on instructables!

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    binaryben

    2 months ago

    Took me a second to remember that the wood was from old fan blades (the trash). The story being the real treasure was easy to see though, and it's adorable! I really enjoyed watching you get to pass on something that your dad shared with you in your own creative way. Thanks for this. I hope your kids treasure theirs for as long as you have your own.

    1 reply
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    Steinzel

    2 months ago

    This is great! Cool that you got your kids involved!

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    David R

    Question 2 months ago

    Do you have the plan for the escaping mongoose?

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    chefspenser

    2 months ago

    Excellent - very well done! Lionel explocing box car of my youth.