Trebuchet Building Plans: How to Build a PVC Trebuchet

First you will need to describe the geometry of the full model, including the hinged counterweight and the sliding sling. Since the physics is rather complicated, however, the approach will be to first briefly describe several simplified versions of the machine, with each successive model more closely approximating the real device.

There are also some Limitations of the model to be consider:
First, all of the parts are assumed to be rigid and the joints rotate perfectly around points. The model is assumed to be rigidly fastened to the ground. In reality, there will be some
flexibility in all of the parts, and often, the model just sits on the ground. Second, we
assume all of the parts are without friction. The projectile during the throw experiences air resistance, and there is some unavoidable friction at axle.

Things You'll Need

• 2 1-inch PVC pipes cut 5 inches in length
• 2 1-inch PVC pipes cut 12 inches in length
• 4 1-inch PVC pipes cut 10 inches in length
• 1 1-inch PVC pipe cut 16 inches in length
• 2 1-inch PVC pipes cut 2 1/2 inches in length
• 4 1-inch PVC pipes cut 1 inch in length
• 4 1-inch PVC 45-degree connectors
• 6 1-inch PVC 3-way corner connectors
• 1 1-inch PVC 4-way "T" connector
• 1 1-inch PVC end cap
• Drill
• Sandpaper
• PVC grease
• Counterweight
• Rope
• PVC glue

Build the base for the PVC trebuchet. Make a rectangle out of the two 12-inch pipes, the two 5-inch pipes and four 3-way connectors. The empty openings on the 3-way corner connectors need to face up. Place one 1-inch pipe into each empty connector. Slide a 45-degree connector onto the end of each 1-inch pipe. The 45-degree connector needs to face
the center of the rectangle. Secure 10-inch pipes into the empty 45-degree angle connectors. Connect the two pipes on each side with a 3-way corner connector. Your piece now needs to look like two triangles standing one in front of the other. Sand one end of each 2 1/2 inch pipe 1/2 inch down the pipe. Coat the sanded edges with the PVC grease. Slide them into the open 3-way corner connectors. Slide the 4-way connector onto the end of the 16-inch pipe. Work it down to 3 inches from the end. You may have to use a rubber mallet to move the connector down the pipe. Add the counterweight onto the same end of the pipe and place the end cap over that end of the PVC pipe. The counterweight depends on the item you wish to throw. You may have to experiment with different weights before you find the best one. Drill two small holes in the pipe, each 1 inch from the end. Thread the rope through the holes and
tie the rope onto the pipe. Use the 4-way connector to place the 16-inch pipe in between the two 2 1/2 inch pipes. Apply glue to all of the connectors and pipes except for the two 2 1/2 inch pipes and connectors. The swing arm in the middle needs to move freely for the PVC trebuchet to work.