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Fire away!

By Pat, 24 May 2013 Activity

Have you ever wondered how people used to attack castles? Follow these instructions and you can create the greatest castle crusher around – the trebuchet!

Diagram showing the the different steps of building a model catapult.

Here is a diagram to help you build a model trebuchet! The number on the diagram matches the number of the step below.

You will need

  • Thick popsticks
  • Craft glue
  • Plasticine
  • Two metal washers
  • Pencil
  • Plastic medicine cup

What to do

  1. Glue four popsticks together to form a square. Glue another six popsticks across the frame to make a base for the trebuchet.
  2. Make the base stronger by gluing another popstick along each edge.
  3. While the base is drying, make two pillars. Lay two popsticks facing each other at an angle. Connect them using a third popstick about two-thirds of the way up. Make sure the base of the pillar will fit onto the trebuchet base. Strengthen the pillar by gluing a fourth popstick opposite the third on the other side of the first two popsticks.
  4. Repeat Step 3 so that you have two pillars.
  5. Glue the pillars to the base, leaning them in towards each other. You can use plasticine to help hold them in place, as well an extra popstick on each side for support.
  6. Break a popstick in half. Lay the halves next to each other, long sides touching. Connect the halves by gluing another popstick across them to create a platform.
  7. Stick two washers on their ends to the popstick you glued in Step 6. They should be parallel so you can poke a pencil through them. Use glue and plasticine to hold them in place.
  8. Glue the platform between the pillars.
  9. Glue two popsticks end to end to make a long arm.
  10. Glue three more popsticks together to form a triangle. Glue the triangle to one end of the long arm.
  11. Glue the medicine cup to the other end of the long arm.
  12. Poke the pencil through the washers. Glue the long arm to the pencil.
  13. Allow all the pieces to dry completely.
  14. Roll a piece of plasticine into a small ball. Place it in the medicine cup.
  15. Make a big lump of plasticine. Place it on the opposite end of the long arm.
  16. Point your trebuchet away from people, pets and breakable things.
  17. Lift up the weighted end of the arm then drop it. How far can you make the ball fly?

What’s happening?

Your model trebuchet is an example of a lever. A lever is a simple machine used to make work easier. A lever consists of an effort, load and fulcrum, which are connected by a solid beam or rod. The effort applies a force to the lever, which does work on the load. The fulcrum is a pivot that allows the lever to rotate.

In this activity, the fulcrum is the pencil; the effort is the big lump of plasticine; and the load is the small ball of plasticine. When you release the effort, gravity pulls the plasticine to the ground. The plasticine exerts a downwards force on the lever, which rotates and pushes the other end up. This does work on the small ball, which causes it to fly out in the direction of rotation.

Applications

Trebuchets were used for centuries by armies laying siege to castles. Trebuchets had the advantage of being able to fling heavy objects a great distance and damage walls and fortifications. This relatively simple siege engine could inflict significant damage.

Advances to weapons technology mean trebuchets have long gone out of fashion, but levers are still very common today. Many tools, such as hammers, pliers and crowbars, are examples of levers that are used every day. Can you think of other examples of levers?

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