How do I Build a Trebuchet?

Rachel Burkot
Rachel Burkot
A hammer is one tool needed to build a trebuchet.
A hammer is one tool needed to build a trebuchet.

A trebuchet is a launching device that was used in the Middle Ages to fire projectiles over walls. Today, physics classes often require students to build a trebuchet. There are two types of trebuchets: a traction trebuchet, which is the historical type used in medieval times, and a counterweight trebuchet, which is a more modern type built by physics students. Building a trebuchet takes about two hours.

To build a trebuchet, certain tools and miscellaneous items are required. These include: a hammer, saw, screwdriver, wood glue, scissors, file, drill and bits, sandpaper, metal cutters, pliers, small screws, small nails, two eyehooks, wire or bread ties, electrical tape, three feet (0.9 meters) of string, six inches (15.2 cm) of cloth, a sheet of cardstock and paints. Any type of pliers will work, but needlenose are preferable because they are easier to use with small objects. The heavy object should be equivalent to the weight of at least 147 pennies. The cardstock or cardboard can be something like a cereal box.

Different sizes of wood are also required to build a trebuchet: one 16-inch (40.6 cm) piece (the swing arm), two 12-inch (30.5 cm) pieces (the long bases), two 10-inch (25.4 cm) pieces (the uprights), three five-inch (12.7 cm) pieces (the cross pieces), and one six-inch (15.2 cm) square piece (the flat wood). Draw a line from one corner to the other on the piece of flat wood and cut, forming identical triangles. Lay out one 12-inch (30.5 cm) piece and one 10-inch (25.4 cm) piece perpendicular to one another. Using nails or screws, place one of the triangular pieces at the intersection of the two longer pieces. Repeat this step on the other side of the trebuchet.

For the next step of building a trebuchet, add the cross pieces to the sides using glue. Drill holes in the top of the uprights and insert metal pieces through the holes, such as a sturdy coat hanger or a screwdriver blade. Using the 16-inch (40.6 cm) piece of wood, drill three holes three, four and five inches (7.6, 10.2 and 12.7 cm) from the end. On the other end, insert a loop and nail at an angle, then file down the head.

To build a trebuchet, now run the metal bar through one upright, a swing arm, and into the other end. Tape up the counterweight using twist ties or wire and loop it through the swing arm. Cut two pieces of 18-inch (45.7 cm) string. Fold the cloth in half and tie each one with a piece of string. Attach a loop to one of the ends of string, then attach the cloth and string 12 inches (30.5 cm) from the arm of the trebuchet.

Use the cardstock to make a runway by folding each end up about one inch (2.5 cm), and glue the runway into the trebuchet. To build a trebuchet, that is the final step. Now test it by putting the projectile into the pouch. The strings and pouch should be placed along the bottom of the runway, and the arm should now swing around, throwing the projectile forward. A trebuchet will last a long time if the proper steps are followed and the proper materials used.

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Discussion Comments


If you are interested in building a full-sized trebuchet, the first thing you must do is ask yourself a question. "Why?" Trebuchets are a lot of fun, but were medieval machines used for bombarding a castle. Nowadays, castles are normally accessible to the general public, rendering trebuchets unnecessary. If you want to enter a castle, simply walk up to the door and knock. It's as easy as that!

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    • A hammer is one tool needed to build a trebuchet.
      A hammer is one tool needed to build a trebuchet.