Making a Mystery Box

So how do you make a mystery box?

Materials you will need:

3x3x3 box (Uline.com sells them in bulk)

1/4” x 3” dowel axle

wooden spool (if you are making a lot try eBay)

2 - pieces 2 7/8” x 2 7/8”  corrugated cardboard

2 pieces Nylon string

    1 - 12”

    1 - 18”

2 washers

tape (I prefer electrical tape)

glue (I prefer the thick crafters glue)

Inside the finished box

Back to Mystery Box Home

Step 2 - Make the axle

Make a Mystery Box - click on any image for larger picture

Step 1 - Axle Holder

Step 3 - Add string

Materials

Making the Box

Step 1 - Axle Holder

The first step is to create a holder for the axle on the inside of the box. To do this you will need to find the center of your cardboard pieces and poke a hole through the two pieces at the same time (so they will line up in the box better). Stretch the hole size by pushing a #2 pencil through the hole to enlarge it so the axle will turn freely.

After you have the holes in the cardboard pieces, add glue to one side of each piece and place them in the box across from each other.

Step 2 - Making the axle

The axle is the secret of the mystery box. The idea is to create two different size axles so the string will wind up at different rates. If you are making a number of boxes, use a variety of different size spools so none of them will work the same and you will have deniability about how any one box works on the inside.

To make the axle take a piece of electrical tape and wrap it around the dowel about three times. This will give the dowel sufficient diameter to hold the wooden spool in place (the hole on the spool is usually larger than the dowel and too loose). Push the spool on to the dowel so it is about 3/8” from the end (see picture). This will give you sufficient length for the cardboard axle holder. Now add a little bit of glue around where the spool and dowel meet on the longer end of the dowel. This will hold the spool and dowel together without both moving.

Step 3 - Adding the string

The string is the last stage before you put it all together. The longer piece of string (18”) will go on the spool and the shorter piece (12”) on the bare dowel axle.

To add the string, put a drop of glue on the spool. Lay the string through the drop of glue so that it is laying perpendicular to the way thread would be wound and the long end of the string is going toward the short piece of dowel sticking out of the spool (see picture). Take a piece of electrical tape and place it across the string (going the direction of winding thread). This will hold the string in place securely. Do the same to the string for the bare dowel axle, but with the string going away from the spool.

By placing the string this way you will avoid it coming off of its respective axle and “breaking” the box.

Step 4 - Finishing the Mystery Box

If you can, let the glue dry on everything before you do the final assembly.

To complete the box, put a small hole on each side of the box directly across from the center of each axle (about 1 1/2” from the bottom and 3/4” from the side). Roll the string on to the spool so it comes off of the bottom. Leave about 4” of string off of the spool to put through the hole. You should not wrap any string around the bare dowel axle.

Carefully place the axle assembly into the box at an angle and push the strings through the holes. Now put the axle ends into the cardboard holders.

Tie a washer on to the end of the spool string and cut and burn the ends so it will not pull apart. Now pull the completed spool thread to wind the bare dowel axle thread on to the axle. When the spool thread is fully extended tie the washer on to the other string so that the washer has just enough string to hang to the tabletop. Tie it off and cut of the excess string. Burn the knot so it will not pull through.

Try out your box, pulling the strings back and forth a number of times. After you are sure that it is working fine close and glue the top of the box. Now when your students ask you to open it you can’t (though they will not realize the bottom can still be opened to fix problems later).

Try a bunch of boxes out on your students using the activity.