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.

How trebuchet work

A trebuchet works by using the mechanical advantage principle of leverage to propel a stone or other projectile much farther and more accurately than acatapult, which swings off the ground. The sling and the arm swing up to the vertical position, where, mostly assisted by a hook, one end of the sling releases, propelling the projectile towards the target with great force. Much improvement has been made upon the trebuchet. Scientists are still in argument over whether the ancients used wheels to absorb some of the excess kinetic energy and put it back into the projectile. It is known that troughs, frequently rotated in either direction for aiming, were used for the projectile to slide along, thus increasing accuracy.

The mangonel had poorer precision than a trebuchet.The mangonel threw projectiles on a lower trajectory and at a higher velocity than the trebuchet with the aim of destroying walls, rather than hurling projectiles over them.

Recently, it has undergone something of a revival of interest
among historians, hobbyists, and assorted show-offs. While many have been successfully built with a rather wide variety of designs, most work on their design has been highly empirical--little work on the mathematical analysis on their operation and design has appeared. The object of this work is to obtain a fairly complete analysis of the device, so that the ingenuity of the medieval engineers can be more fully appreciated, and modern dabblers in the art can produce more reliable and powerful designs.

How To Build A Trebuchet

By Tyler Geonetta

Okay, so you want build your first trebuchet. This site will have tips and tricks of the trade. Okay, lets get to business.

The first question you will need to ask yourself is whether you want to build a "historically accurate" traction trebuchet, or it's simpler and easier to design and build cousin, the counterweight trebuchet.

If your building a trebuchet for the sole purpose of your highschool physics teacher's amusement, then you should probably consider one of the counterweight variety. If, on the other hand, you are building a trebuchet for fun or self education, the traction trebuchet may be something to seriously consider. (Keep in mind that at least three-fourths of the "free" plans on the web are of the counterweight flavor.)

Once you have determined your design plan, you probably want to decide on a suitable size. If your looking to launch bowling balls the length of a football field, you will want a much larger trebuchet than if your intending to launch eggs at incoming traffic. Which, of course, is a BAD thing to do. (Based on personal experience most drivers won't enjoy chipping dried egg off their windshield.) Another point of interest is whether or not to buy premade trebuchet kits or design plans for your trebuchet. If you are just a beginner, kits are excellent to use. Plans also will help you out immensely if you are just a beginner.

Now, the next step is construction of your trebuchet. For most people, I would suggest using 1"x2" pine for all of the pieces. But, if your going to be building a 10ft tall trebuchet, stretch for the 2x4's. Once you have completed your trebuchet structure-wise, you will need to construct a sling and if used, a suitable counterweight. I prefer cutting up any kind of old cloth and attaching both ends to lengths of string.

Suitable counterweights can be anything from a box/bottle full of lead shot, to a sock full of rocks, or a dumbbell weight. After you have all of that stuff sorted out, you should attach the trigger mechanism and release pin. There are plans and pictures of these on most sites, but the only advice I can give you is that the release pin is the trickiest part of constructing a trebuchet. It should be angled so that the sling releases the projectile at an angle of somewhere around 45 degrees.

Final word: Building a trebuchet can be lots of fun and be a great learning experience. (Or sometimes an unbelievable chore for those unlucky physics students such as myself). Construct your trebuchet with quality and take care to add support where needed and it will last you a long time.

Oh yes, and Links:

General Design:
http://www.tasigh.org/ingenium/medium.html

Good Pictures:
http://www3.telus.net/public/royway/

Whether your building a trebuchet for your a physics project, or for the fun of it, your sure to find something here.

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