Trebuchet Project

This project is currently being used for a middle school intro to engineering program. This project is pretty simple to build and just about any home improvement store will have the supplies.

The kids are given the materials and the trebuchet drawing (see link in description). It takes the average group (2 to 5 kids) about 10 minutes to assembly the trebuchet. There are two variables in the setup. The first is the launching arm - three choices are available: short, medium and long. The other variable is the height of the weight. This is controlled by the distance on the ruler attached on the board at the base of the trebuchet. Data is collected for the three arm lengths across the weight height range (see link to spreadsheet). After the data is collected, a competition is held to hit a target (bucket, 20 feet away).

See video for actual build.

Step 1: Materials, Tools and Notes

Trebuchet Project

Materials:

  • PVC Pipe, 1/2" diameter x 30" Long (x2)
  • PVC Pipe, 1/2" diameter x 17" Long (x4)
  • PVC Pipe, 1/2" diameter x 4" Long (x3)
  • PVC Pipe, 1/2" diameter x 3" Long (x4)
  • PVC Pipe, 1/2" diameter x 1.5" Long (x12)
  • PVC Pipe, 3/4" diameter x 17" Long
  • PVC Pipe, 3/4" diameter x 8" Long
  • PVC Pipe, 3/4" diameter x 6" Long
  • PVC Pipe, 3/4" diameter x 4.5" Long
  • PVC Pipe, 3/4" diameter x 1.5" Long
  • PVC Elbow, 1/2", 45 degree, Female Unthreaded Socket Ends (x8)
  • PVC Tee, 1/2", Female Unthreaded Socket Ends (x10)
  • PVC Tee, 3/4", Female Unthreaded Socket Ends
  • PVC Cross, 3/4", Female Unthreaded Socket Ends
  • PVC Adapter, 3/4", Unthreaded & Female thread
  • PVC Adapter, 3/4", Unthreaded & Male thread (x3)
  • PVC Cap, 1/2", Female Unthreaded Socket End (x4)
  • PVC Cap, 3/4", Female Unthreaded Socket End (x3)
  • PVC Glue/Cement
  • Pin or nail - 1/8" diameter x 3/4" long
  • Epoxy
  • Wood - 30" x 4.75" x 5/8"
  • Paper Ruler - 30" long
  • Clear Packing Tape
  • 5lb weight
  • Rope (30")
  • Rubber squishy ball
  • Fishing line - 26" long

    Tools:

  • Saw
  • Drill
  • Ruler

    Notes:

    Refer to the drawing for build instructions (last step). Note that Upper and Lower frame joints (items 1 and 2) are shown as assemblies on the drawing. This is an optional step which was done to speed up the build process for classes that had limited time. Both of these assemblies were glued together. The launching arm assembly must be glued together to support the weight and swinging motion.

    Step 2:

    Trebuchet Project

    Cut PVC pipe to the lengths shown in materials list

    Step 3:

    Trebuchet Project

    Assembly the lower frames assemblies

    Step 4:

    Trebuchet Project

    Connect assemblies together with 30" pipe

    Step 5:

    Trebuchet Project

    Add the 17" pipes off the 45 degree fittings

    Step 6:

    Trebuchet Project

    Attach the upper frame assemblies to the upper sides of the pipe

    Step 7:

    Trebuchet Project

    Feed the 4" pipe through the launching arm between the two upper frame assemblies

    Step 8:

    Trebuchet Project

    Tie the 5lb weight to the launcher arm

    Step 9:

    Trebuchet Project

    Cut a piece of wood 30" x 4.75". Thickness doesn't matter (.25" to .75" will work). Find or print out a ruler and attach it to the wood. This version was printed and covered with clear packing tape.

    Step 10:

    Trebuchet Project
    Trebuchet Project

    Drill a hole in the 3/4" end caps. Pre-bend a pin (nail) to a 60 degree angle. Place pin in the hole and use epoxy to secure the pin to the cap.

    Step 11:

    Trebuchet Project

    As mentioned above, the arm length can be adjusted by swapping out the launcher end caps (short, medium and long). Make sure pin is facing forward.

    Step 12:

    Trebuchet Project
    Trebuchet Project

    Cut a piece of fishing line to 26" long. Tie knots on one side of the line. Drill or poke a small hole through the diameter of the squishy ball (slightly bigger than the fishing line). Feed the straight end of the fishing line through the ball. Tie a 1" diameter loop on the other end of the line.

    Step 13:

    Trebuchet Project

    Cock trebuchet by pulling the ball back along the board. Record the cocking distance on the data sheet. The ball should fly up to 50 feet.

    Step 14: Drawing and Data Sheet

    Drawing:

    https://googledrive.com/host/0B21TbB8gGNQbLXMydVlY...

    Data Sheet

    https://drive.google.com/file/d/0B21TbB8gGNQbaWVCc...

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