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Make a jumping jack

By David, 12 May 2022 Activity

Cardboard robot toy with moving arms and legs

Pull the string and watch the robot jump

This cardboard doll loves to leap! It takes a bit of crafting, but the results will make you jump for joy.

You will need

  • Thin cardboard
  • Textas
  • Scissors
  • Hole punch. A single hole punch is easiest, but you can use a 2 hole punch too.
  • Split pins
  • String

What to do

  1. Drawing a robot body on cardboard.On a piece of thin cardboard, draw a body and head. Don’t add arms or legs.
  2. Cutting out the robot Cut out the body and head as one piece.
  3. Punch holes in the shoulders and legs of robotPunch a hole at each shoulder and one at each hip. This is where you will attach the arms and legs.
  4. Cut legs for robot.Roughly cut 2 long rectangles to make arms and 2 long rectangles to make legs. Make them about 5 centimetres longer than you’d like them on the finished doll. Remember, you can always cut them a bit shorter at the end. It’s a lot harder to make them longer!
  5. Punch holes in legs to attach split pinsPunch a hole near the end of each arm and leg, and then punch another hole about 1.5 centimetres further down each limb.
  6. Attach arms with split pinsTime to attach the first arm! Stick a split pin through the front of a shoulder hole, and then through the second hole of an arm piece. Spread the prongs of the pin and adjust so the arm swings freely.
  7. Attach arms and legs with split pinsUse the same method to attach the second arm, and each leg at the hips.
  8. Draw arm and leg details onto cardboard.Draw in the details for the arms and legs. You can now trim them down if they are too long.
  9. Tie string between each arm.Cut a piece of string and tie it between the end holes on each arm piece. You want the string just long enough to have a bit of slack to it.
  10. Tie string between legsCut another piece of string and tie it between the end holes on each leg piece. Once again, you want a bit of slack to it.
  11. Cut a longer piece of string, about twice the length of your doll’s body and head.
  12. Tie the arms and legs together.Tie the middle of the long string to the middle of the string between the doll’s legs.
  13. Tie the arms and legs together.Tie one end of the long string to the middle of the string between the doll’s arms.
  14. Test the movement of the arms and legs.You’re ready to test! Hold the doll by its head and pull down on the free end of the long string. If everything works right, the doll should raise its arms and legs. Don’t worry if it doesn’t work quite right the first time.
  15. Adjust the string lengths and tie off.If the arms raised but not the legs, try lengthening the part of the string that runs from the leg strings to the arm strings. If the legs raised but not the arms, try shortening this part of the string instead.
  16. Once you’re happy with how the toy is moving, trim off any excess string. Time to jump!

What’s happening?

This fun jumping toy is called a jumping jack. Versions of this toy have been around for hundreds or maybe even thousands of years.

It only takes a short tug to get the arms and legs moving wildly. This is down to where you put the holes in the legs and arms. Each limb acts as a lever, and the lever amplifies the movement, making a short tug into a wild flapping. The cost of this amplification is force, so the paper doll is faster but harder to move. Luckily, it’s made of light cardboard, so it still flaps with relative ease.

You can also use levers in the opposite direction, trading speed for strength. If you look at the hole punch, you’ll notice your hand moves faster than the punching part does, but the punch gains plenty of force allowing it to punch through several sheets of paper at one time.

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