How to Make a Potato Trebuchet

The trebuchet, or counterweight catapult, was a medieval war machine that used the action of a counterweight to hurl projectiles at enemy fortifications. Medieval trebuchets could be 50-feet tall or higher, capable of launching huge boulders up to a mile. Despite the massive size of these machines, they operated on simple mechanical principles. The basic simplicity of the mechanism means that you can build a small trebuchet capable of launching a potato using simple materials.

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Paper and pencil
Wood
Saw or craft knife
Wood glue
Metal rod or pipe
Drill
Screw hooks
Screwdriver
Screws
Weights
Cord or string
Scissors
Wire
Nails or pins
Cloth or leather
Potato

Instructions

- 1
  
  Draw a plan for your trebuchet. The larger the trebuchet, the longer its range will be. A foot-high trebuchet can throw its projectile up to 10 yards.
- 2
  
  Cut the parts of your trebuchet from wood using a saw or craft knife. You will need 10 wooden sections. These are a swing arm, two long base pieces, two uprights, three cross pieces and two triangular supports. The size of these will vary depending on the scale of the trebuchet. The swing arm should be a one-third longer than the base, and the uprights should be one-sixth shorter. Thus, if your base is a foot long, the swing arm should be 16 inches and the uprights should be 10 inches. The cross pieces should be about half the length of the uprights.
- 3
  
  Attach one upright to each base piece at right angles. The upright should be about one quarter of the length of the base piece back from its forward edge. Attach these using wood glue if your model is small. For larger models, use your craft knife to cut a groove in the base piece and fit the upright into it.
- 4
  
  Attach the triangular supports, connecting the uprights and base pieces and giving them extra rigidity.
- 5
  
  Attach the three cross pieces between the two base pieces. Place one at the front end of the two base pieces, one at the rear and one between the uprights. If you wish, you can also add a single sheet of wood over the cross pieces to create a smooth surface.
- 6
  
  Choose a length of pipe or metal rod to be your axle.
- 7
  
  Drill a hole in each upright for the axle to pass through. The hole should be located near the top of the upright. Drill a corresponding hole in the swing arm, one-quarter of its length from the end. You can also drill two additional holes, one on either side of the first, which will allow you to adjust the length of the throwing arm.
- 8
  
  Push the axle through the hole in one upright, through the hole in the throwing arm and out through the hole in the opposite upright.
- 9
  
  Insert a screw hook into the end of the throwing arm closest to the axle. Cut a length of string, attach it to a counterweight such as stones, batteries or lead weights, and fit it through the hook.
- 10
  
  Push a bent nail or pin into the head end of the throwing arm. Insert another screw hook into the underside of the throwing arm near the head. These will form the attachment points for the sling.
- 11
  
  Cut a sling pouch out of cloth or leather. Make sure that this fits the potato you intend to use as a projectile. Attach string to two ends of the pouch. Tie one of these to the screw hook near the head end. Make a small loop from wire, tie it to the string on the other side of the pouch and slip the wire over the bent nail.
- 12
  
  Load the potato into the pouch, then elevate the counterweight and release it. This will swing the throwing arm, launching the projectile.