Trebuchets and Seige Weapons

The trebuchet is basically a lever device that can be built with basic materials, many of which can be found in the home. The trebuchet requires no batteries, no fossil based fuel, wind or water to operate and building a trebuchet is fun for all ages. It uses a controlled weight and the force of gravity upon the weight, and when triggered, a lever arm transfers natural energy to generate amazing throwing power. Essentially, when a controlled weight is released at a specific height it displaces static energy to form kinetic energy. When this energy is redirected to a "sling", it will ultimately launch varying objects hundreds of feet or yards.

Centrifugal force also plays an important role in the performance of a trebuchet. Imagine throwing a baseball or football. The trebuchet sling operates in a similar motion. You start the throw with the ball in your hand and then extend it backward behind your head and shoulders, gradually returning the ball with hand and arms forward and to release. Although not identical, a similar motion occurs with the trebuchet. The throwing object starts in one position and when activated, the projectile will slide along a track or board surface. As the swing arm pulls the sling harness skyward, the projectile will follow the path of an arc. One end of the sling must open at the apex, releasing the projectile and allowing it to launch skyward.

Many new builders initially make the mistake of placing the release prong (headless nail) or slot at the wrong angle. Doing so may cause the trebuchet sling to release prematurely or too late, this would affect the launch distance and trajectory. Another key feature of the sling is that one end should be permitted to release (open) at just the right time. A headless nail or prong, or a angle cut at the end of a swing arm should be adjusted to ensure a proper release and preferred flight trajectory. As the sling end (projectile) approaches a vertical position, one sling end should slide off an end prong (or out of a sling arm "end slot") to complete a successful toss.

Trebuchet designs range from paperclip to piano slinging models, but perhaps one of the most popular reliable online models is available at No Cost. You can obtain access to the plans at the "How To Make A Trebuchet" website. My teenage son found it, ordered it, followed the free plans and had hours of fun building it and playing with it (so did his friends). In the end, he also wound up getting a $50 rebate from a major national company in exchange for his free trebuchet plan kit. Not bad. He might turn out to be a smart kid after all. This should suffice to explain What is a Trebuchet?

If you struggle with how to improve trebuchet performance or to get more results from anything mechanical....the Global Specs website offers mathemaical solutions. Beyond the myriad of engineering variables, formulas, equations and all other linear thinking resources, ANYONE can enjoy the TREB CHALLENGE. It's really a simple online challenge that powerfully illustrates the forces of physics on trebuchet performace, regardless of one's level of understanding. It reveals how adjusting basic design features can improve a Trebuchet machine's accuracy, distance and power.

Even if you don't build trebuchets, check it out....it's fun whether you enjoy building trebuchet models or you think you already have the best trebuchet plans.

Building a trebuchet is not near as complicated as it might first seem. Sure, there are specific formulas and software programs that can crank out optimal performance trebuchet designs. However, I know builders who can estimate dimensions, cut out and then assemble their trebuchet hurling machines quickly without the aid of high-tech software analysis. Their trebuchets also perform with amazing distance, accuracy, and consistency. In this short article we will examine key elements to build in the proper sequence and in the proper scale [or relationship] to other components of the final working machine. Don't be intimidated, building a trebuchet is really not rocket science.

For most trebuchet enthusiasts, the fun of "hurling" also includes the designing, constructing and modifying of these amazing models. So let's take a look at the key elements of building a trebuchet.

Base:
The base of a trebuchet must support the glide track, tower frame, and swing arm lever. The trebuchet base is typically attached to the glide track [board] upon which the sling harness will slide. There is no absolute formula for designing a trebuchet base. In fact, they come in a myriad of sizes, both in width and length. However, I have found that reliability and consistency is produced when the length of the base is 75-80% of the length of a swing arm (lever). Another good rule of thumb when building a trebuchet is that the width of the base should be about one-third of its' length.

The base should be designed with the tower width and counterweight size in mind, since the size of the weight or box will need to swing through without interference. If the attached weight or box is wider than the support [tower] frame it will not pass down and through as it should...unimpaired.

Glide Track [board]:
This is the surface upon which the sling harness slides after the trebuchet trigger is activated. In most cases, the glide path is about three-fourths (3/4) the length of the base. When the swing arm lever is released the attached sling is drawn along the glide path and then whipped upward in an arc path until the cradle holding a projectile opens and releases it.

Tower Support Frame:
When building a trebuchet the tower frame is generally about 3/4 the length of the base. For instance, if the base measures 40 inches, a good tower frame height would be 32 inches. Again, these are approximations. The width between the tower primary support beams will depend greatly upon the type and size of weight planned for use. You will need to decide what size and the weight of an object to throw, and then select the appropriate weight(s) to use. Counterweights should be "approximately" 75-100 times the weight of the projectile.

Swing Arm Lever:
Building a trebuchet requires a primary swing board which is more commonly referred to as a "swing arm lever", but some may refer to it as the long arm lever or long arm beam. The swing arm lever works well when it is 1.4 - 1.6 times the base length. So, if the base board length is 3 feet, the swing arm lever could range from 50 inches to 58 inches. This will depend upon the builder and certain other adjustments that can be made, but I would tend to lean to the shorter side...probably choosing a 54 inch length (1.5 x).

Counterweight:
The counterweight will ultimately determine the height and/or distance that a projectile will potentially fly. As indicated above, a counterweight that is 80-100 times heavier than the projectile will generally produce optimal results. However, understand that all other features of the trebuchet can serve to enhance or diminish overall performance. For instance, if the swing arm is too short or too long the trebuchet results may be limited.

Sling [harness]:
The sling is attached to the long end of the swing arm lever. It is connected by rope, string or cable to a cradle or pouch holding the object to be "hurled". The sling harness length should be approximately 3/4 of the glide board. The sling harness should be designed to open and release the object in the cradle or pouch when it reaches the precipice of the launch path. This will depend upon whether one of the sling ropes is attached by a prong or in a slot cut at the end of the swing arm lever. Each trebuchet may have a slightly different release design.

Although not precise calculations used by all trebuchet builders, these primary features of a trebuchet will be useful for any novice trebuchet enthusiast. Understanding the basic design components should also help you enjoy building a trebuchet.

Primary Lever = Throwing arm; also called the swing arm. Has what are considered long and short ends based on the relationship to the pivot position connected to the tower frame. The long end should be 3-5 four times longer than the short end and it should be strong but light. Sufficient to hold the counterweight but yet light. Don't try to make the board longer with the intent to increase distance...that's not how it works. The key will be to enable the counterweight to swing through quickly for optimal hurling distance.

Sling = A good rule of thumb is to begin with the sling harness approximately 3/4 the length of the upper (longer) end of the beam and trial for optimal trajectory. The sling length will influence projectile trajectory, causing an object to too fly high, too forward, or even backward.

Counterweight = Weight about 80 to 100 times as much as the projectile to be hurled. It can be a fixed or a free moving weight affixed to the swing arm lever (beam).

Base = Foundation on which to construct the glide track and support frame pieces. The base should be designed and constructed to firmly hold together the structure during the "whipping" transfer of energy from the release of the beam (swing arm lever) that allows the force of gravity to draw the counterweight down. It is a sudden and powerful transfer that can sometimes be offset by adding wheels to the base. For a top Trebuchet Design

Frame = Is essentially the primary 2 side tower beams braced by supporting pieces. The height of the axle pivot point should be set so that the swing beam is positioned about 45° when cocked and secured in the firing position. The attached counterweight should clear the tower frame sides, as well as, the "glide" or sling platform base when it travels down and through.

There is an array of other terminology used trebuchet design and trebuchet building, but these are the primary features that distinguish the trebuchet from other "hurling" machines (designs). To learn how to apply these design features easily and quickly, visit How To make A trebuchet

If you don't know how to build a trebuchet and you have friends who have built one or you have seen a trebuchet in action...don't fret. You can build your own backyard model without much difficulty as long as you use reliable plans.

One of the most popular backyard trebuchet designs available today is the Treb309 model. The designer has many successful designs to his credit, but this particular model has proven to be one of his most reliable. Ample trebuchet plans can be found online but very few provide the unique "hand holding" instruction included with the Treb309 package. Treb309 comes with blueprints and step-by-step video assembly instructions so that enthusiasts from all age groups can follow the plans and be enjoying the fun relatively quickly.

You can easily learn How to Build a Trebuchet if you can follow simple directions (print and video), use a tape measure, and cut a few pieces of wood. It really is that easy with the Treb309 plans offered exclusively through the "How to make a Trebuchet". website. Depending on whether you have a preference for a physical copy or prefer immediate download, they even offer an option to acquire the plans for free. They really are ideal plans for someone just starting out and wanting to learn How to Build a Trebuchet.

If you do not like to construct things, but like to have fun, these pre-made kits may be ideal for you. They are simple but inexpensive trebuchet and catapult kits for all ages.