What you’ll need

  • A cardboard box (the size of a shoe box)
  • 50 cm of sturdy wire (approx. 2 mm thick)
  • 1 wooden skewer (approx. 20 to 25 cm)
  • 1 cork stopper
  • Colored paper, colored pens and other decorations
  • A ruler
  • Scissors
  • An awl
  • Quick-drying glue
  • A sharp knife
  • A cutting board
  • End-cutting pliers and flat-nose pliers for cutting and bending the wire
  • Topsy figure: download here (PDF, 2 MB) to print and cut out

Note: Let an adult help you with all the steps that require a sharp or pointed tool!

How to do it

1. Place the cardboard box edgewise in front of you so that the base is facing you. The narrow side at the top will be the platform for your crank-operated theater.

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2. Decorate the box any way you like.

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3. Using the ruler, mark a point exactly in the center of the platform on the top, narrow side.

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4. Place the wooden skewer lengthways on the wide side of the cardboard box so that it extends 4 to 5 cm over the edge. You now have the right height for marking the next point.

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5. Place the ruler at the end of the wooden skewer and mark two points on the sides of the box. These should be exactly opposite each other.

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6. Ask an adult to help you make holes through the marked points using an awl. The holes must be large enough for the wire and skewer to move about easily in them.

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7. Using the knife, cut off a piece of cork about 1 cm thick and use the awl to pierce a hole through the middle of it. This should also be large enough for the wire to move easily within it.

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8. Now measure off about 50 cm of wire and thread the piece of cork onto it. Make sure that around one-third of the wire sticks out on the left, and around two-thirds on the right.

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9. Use the flat-nose pliers to twist the wire on both sides of the piece of cork, as shown in the photo.

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10. Punch a hole into the side of the piece of cork and glue the wooden skewer into it.

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11. Now you can install your cork-wire drive in the box. Insert the skewer through the hole on the upper, narrow side of the box and thread the wire ends through the side walls.

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12. Bend the crank on the right as shown in the picture. Bend both ends of the wire into eyelets, so that you can’t hurt yourself and to stop the wire from slipping out of the box.

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13. Now glue your Topsy cutout onto the top end of the wooden skewer. Next, rotate the handle and watch what happens to Topsy!

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Well spotted!

Via the wire the rotation of the crank makes the wooden skewer go up and down.

What's the secret?

A crank drive is not just a bit of fun. Before the invention of motors, water wheels were used to drive machines, for example. Of course the mechanisms they needed were more complicated than this one, but they used the same principle of rotation. You can imagine how the rotation of a water wheel would have been able to move a saw up and down, for example.

In the case of an internal combustion engine, it is the other way around – the recurring small “explosions” during fuel combustion cause a piston to move up and down. This movement is transformed via a crank drive into a rotation that drives the wheels.