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Here are some notes on adjusting your trebuchet or catapult to help maximize the distance it will launch an object. Happy flingin'!

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Catapults and trebuchets originated more than 2000 years ago, and over time became highly sophisticated machines that represented the pinnacle of medieval engineering. The largest machines were capable of consistently launching half-ton boulders hundreds of feet, knocking down thickly fortified stone castle walls - no small feat!

The general working property of a trebuchet isn't too complex - it's a large lever that works by multiplying the speed on a short arm by the ratio of its length compared to the long (throwing) arm. Gravity is used to provide the energy for this, in the form of a counterweight, and a sling is attached to the end of the throwing arm to further multiply the speed of the projectile. But within those few components, you have a multitude of variables, all which interact to affect the distance a machine can hit.

Here are some good tips for tuning your trebuchet for maximum effect:
Physical Dimensions:
One of the first pieces to consider is the ratio of the short arm to the throwing arm. General wisdom has a 5:1 ratio being the norm for a standard trebuchet, although 4:1 is sometimes used. The longer the ratio, the greater the speed that tip of the throwing arm will reach - but also increasing the force required to move it quickly.

A second component is the height that the axle will be placed above the platform of the trebuchet. Larger distances allow the throwing arm to be placed higher up, which increases the distance that it will travel when released. The further it travels, the more it will accelerate, which again increases tip speed on the throwing arm.
Weight:
Obviously, there's a connection between the counterweight and the throwing arm/projectile. General advice is that the optimal ratio is 133:1. A golf ball projectile (1.62 oz) should fire best with 13.46 lbs of counterweight - and a 14 lb bowling ball should have 1862 lbs pulling on the other side of the arm to reach maximum distance. Of course, this is all dependent on other variables and may differ for you, but is a good starting point for your machine.

The weight of the throwing arm should also be kept as low as possible, but not without damaging the integrity of it. A lightweight but strong material is advised for best results - for smaller machines ash can used, but on larger trebuchets, the strength of oak, aluminum, or even carbon fiber becomes necessary.

It is advisable to taper the throwing arm to keep it light at the tip. Meanwhile, the short arm should be stout and strong, as it has a lot of mass to support. Don't be afraid to break it while testing - it's good to know the limits and get as close to them as possible.
Sling:
Sling length and pin angle work together to affect the angle of release. Longer length slings have a lower angle of release, good for line drives (if you need a direct hit against the castle gate, for instance). Shorter lengths will result in a higher angle of release, best for lobbing projectiles over tall objects. The general ratio to start at is a sling length (arm connection to tip of pouch) 80% the length of the throwing arm.

Modifying the release pin angle will also affect the trajectory of the launch. Forward facing by 30º is the norm - but the length of the sling and the angle of the pin interact greatly, so make sure to change both while testing to exploring the full potential.
Wheels:
Trebuchets large and small tend to have wheels, which initially appear to be for transport. And while this would be true for minor adjustments, the largest trebuchets were so massive and heavy that they would have to be assembled on location. The real purpose of the wheels is to allow the entire mechanism to move back and forth as the counterweight is released, keeping the weight's movement as vertically linear as possible. A weight that rotates downwards loses some of the power of gravity as the force on it has to be transferred into a forward and then backward motion. But if the counterweight drops directly downwards, it can maximize the effect of gravity.
Wind Resistance:
Not a major factor until very large builds are happening, do to the squaring effect of resistance due to wind. But for those who are working with large machines, making the moving parts (throwing arm, sling, pouch) as invisible as possible to the wind will help increase the distances.

Also, film and review your throws. A lot can be seen by checking the frames of your launches to determine what is happening, and where.

Many of these notes were taken from The Hurl, a great community of trebuchet and catapult enthusiasts. This thread on their forum details the tuning of a smaller trebuchet that was able to go from 30′ to 115′ throws with a variety of modifications. Quite an increase.

Ripcord's trebuchet website has a tremendous amount of information on building and improving your catapult through better sling design and more. A must read.

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Tonight (Dec 12) I will be hosting a live discussion on the Craftsman Experience live feed with Joseph Budka, who just completed a bowling ball launching trebuchet for this show. We spent a couple days playing with the machine and will discuss the trials and tribulations of assembling one of these awesome projects (including recovering from a catastrophic malfunction). Make sure to tune into the Craftsman facebook page and click the "Experience" tab to watch. 730pm EST, 430pm PST.

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Tuning A Trebuchet For Maximum Distance - A Look at the Components and Variables - DO IT: Projects, Plans, and How-tos

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Here are some notes on adjusting your trebuchet or catapult to help maximize the distance it will launch an object. Happy flingin'! ======================== Catapults and trebuchets originated more than 2000 years ago, and over time became highly sophisticated machines that represented the pinnacle of...

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Why is it better for a bigger or smaller trebuchet?

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Why is it better for a bigger or smaller trebuchet?

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The smallest working trebuchet.

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Trebuchet Launching 7th Grade Science Project

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Traction & Counterweight Trebuchets Medieval Equipment

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A very tiny working trebuchet. There's something about building something in a small scale that could still be usable if you found tiny enough people to use it.

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This video shows a step by step process of building a trebuchet. It also explains why each part is needed

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This article has some general facts about the trebuchet

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The History of the Trebuchet
The traction trebuchet is believed to be an ancient war engine which was invented in China in 300BC. It is thought that the trebuchet may have developed from the stave sling. In the traction trebuchet a large troop of men pulled down on ropes to propel the missile.

The trebuchet reached Europe during the Medieval era in 500 AD and was used extensively by the French and the troop of men were replaced with a large fixed, or pivoting, counterbalance weight. The Trebuchet (Trebucket) was introduced in England in 1216 during the Siege of Dover - as were many other types of siege engine. Louis the Dauphin of France crossed the Channel with a large force and laid siege to Dover Castle making a violent and incessant attack on the walls. He used the trebuchet against the walls of Dover Castle. The constable of Dover castle was Hugh de Burgh - he refused to surrender.

Trebuchet

Trebuchet

Medieval Trebuchet in warfare

Description of the Trebuchet

History of the Trebuchet

Design of the Trebuchet

Missiles launched from the Trebuchet

Trebuchet maximum rate of fire

Stones

Sharp wooden poles and darts

Fire

Casks of Burning Tar

Burning Sand ( this became trapped inside armor )

Pots of Greek Fire

Dung

Dead, sometime mutilated, bodies

Disease ridden bodies

Body parts

Dead animals

Any rotting matter

Quicklime

Trebuchet

Medieval Weapons - Trebuchet

The weapons used by the Medieval Knights - Swords - Broadsword, Falchion, Bastardsword, Cutting sword and the Greatsword

The Mace, the Dagger and the Lance

The Medieval weapons used by the armed men and archers including:

The Crossbow, The Longbow, The Battle Axe

The Poleaxe and Pikes

The massive Siege Weapons

Medieval Weapons

Trebuchet - Famous - History - Facts - Information - Info - Old - Medieval - Mediaeval - Middle Ages - Medevil - Medevial - Meadieval - Trebuchet- Madieval - Meideval - Medievall - Midieval - Midevil - Mideval - Casttle - Carstle - Cassel - Cassell - Carsel - Carsell - Carsel - Carstle - Carsall - Fortress - Citadel - Court - Donjon - Fasthold - Fort - Fortress - Garrison - Keep - King - Knight - Safehold - Stronghold - Tower - Moat - Dungeon - Defence - Battle - Build - Trebuchet - Defend - England - English - Court - Life - Times - Era - Period - Trebuchet - Trebuchet - Famous - History - Facts - Information - Info - Old - Medieval - Mediaeval - Middle Ages - Medevil - Medevial - Meadieval - Trebuchet- Madieval - Meideval - Medievall - Trebuchet - Midieval - Midevil - Mideval - Casttle - Carstle - Cassel - Cassell - Carsel - Carsell - Carsel - Carstle - Carsall - Fortress - Citadel - Court - Donjon - Trebuchet - Fasthold - Fort - Fortress - Garrison - Keep - King - Knight - Safehold - Stronghold - Tower - Moat - Dungeon - Defence - Battle - Build - Defend - England - English - Court - Life - Trebuchet - Times - Era - Period - Trebuchet - Trebuchet - Famous - History - Facts - Information - Info - Old - Medieval - Mediaeval - Middle Ages - Medevil - Medevial - Meadieval - Trebuchet- Madieval - Meideval - Medievall - Midieval - Midevil - Mideval - Casttle - Trebuchet - Carstle - Cassel - Cassell - Carsel - Carsell - Carsel - Carstle - Carsall - Fortress - Citadel - Court - Donjon - Fasthold - Fort - Fortress - Garrison - Keep - King - Knight - Safehold - Stronghold - Tower - Moat - Dungeon - Defence - Battle - Build - Trebuchet - Defend - England - English - Court - Life - Times - Era - Period - Trebuchet

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Visit this site dedicated to providing information about the Trebuchet siege engine.Fast and accurate details about Trebuchet.Learn about the Medieval Trebuchet.

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A diagram that shows a trebuchet from medieval times

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What is the reason people used trebuchets?

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What is the reason people used trebuchets?

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The trebuchet was a weapon used during the middle ages in siege warfare. The medieval trebuchet was similar to a catapult, or stave sling, which was used for hurling heavy stones to smash castle or city walls.

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Go to this site providing information about the facts, history of the Trebuchet. Fast and accurate facts about the Trebuchet. Learn about the history of the Trebuchet.

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This article has information on the counterweight and how it works.

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Summary

*Note: For this science project you will need to develop your own experimental procedure. Use the information in the summary tab as a starting place. If you would like to discuss your ideas or need help troubleshooting, use the Ask An Expert forum. Our Experts won't do the work for you, but they will make suggestions and offer guidance if you come to them with specific questions.

If you want a Project Idea with full instructions, please pick one without an asterisk (*) at the end of the title.

Abstract

Before cannons widely replaced them, siege engines were often used by armies to throw large stones and other projectiles to break down castle walls. One of the most advanced siege engines used in the Middle Ages was the trebuchet, which used a large counterweight to store energy to launch a payload, or projectile. The horizontal distance the payload would travel is called the trebuchet's range. Figure 1, below, shows a modern reconstruction of a trebuchet.

The range of a trebuchet has always been important. In the Middle Ages, soldiers had to make sure their trebuchets had a long enough range to stay outside the range of defending archers on castle walls. While they are no longer used in warfare, today people still build trebuchets for fun and use them in contests to see who can launch things the farthest. There are many different factors that can affect the range of a trebuchet; for example, the mass of the counterweight or the length of the lever arm. While designers of the Middle Ages had to rely largely on intuition or trial and error to build their trebuchets, modern builders have many helpful tools available. In addition to building prototypes of a trebuchet, you can also use physics calculations or even a computer simulation to help you design it to have the best range.

This abbreviated engineering project idea will help you get started with three different ways to investigate what factors can increase the range of a trebuchet:

Trebuchet Physics: Use hand calculations to predict the range of a trebuchet based on its dimensions and other variables.

Computer Simulations of a Trebuchet: Use computer simulations to predict the range of a trebuchet and modify its design.

Building a Trebuchet: Build your own trebuchet and test it.

You can decide whether you want to try just one, two, or all three of these approaches. Read the relevant section(s) below for ideas on how to get started on your project.

Trebuchet Physics

If you want to do hand calculations to design a trebuchet with the best range, you will need to understand the physics involved. Figure 2, below, shows a diagram of a trebuchet with the main parts labeled. The trebuchet relies on the principle that stored potential energy of the counterweight can be converted into kinetic energy of the payload, launching it into the air.

Figure 2 raises several questions about designing a trebuchet. To throw the payload as far as possible, how long should the beam be? Where should the pivot point be on the beam? How high off the ground should the pivot be? How heavy should the counterweight and the payload be? Figure 3, below, shows a sketch that can help you start thinking about how to set up the problem, and the variables involved.

The variables in Figure 3 are as follows:

m₁ is the mass of the counterweight in kilograms (kg).

m₂ is the mass of the payload (kg).

h is the initial height of the counterweight off the ground.

L₁ is the distance between the pivot and the counterweight's attachment point in meters (m).

L₂ is the distance between the pivot and the sling's attachment point (m).

L₃ is the length of the sling (m).

L₄ is the length of the rope suspending the counterweight (this distance is zero if the counterweight is fixed directly to the lever arm) (m).

How can you use these variables to calculate the range of a trebuchet? There is more than one way to tackle the problem. Depending on your experience levels with math and physics, you can try the following approaches:

If you have knowledge of basic physics concepts like projectile motion and conservation of energy, can you predict the maximum possible range of the trebuchet, assuming all of the counterweight's initial potential energy is converted to kinetic energy of the payload? Hint: Assume the payload leaves the sling at a launch angle of 45°.

Can you derive equations that describe the position of the payload as a function of time, before and after it leaves the sling? Assume the trebuchet starts from rest with the counterweight at height h above the ground. What variables do you need to use to fully define the position of the trebuchet and the payload? Hint: They are not labeled in Figure 3. One of them is the angle of the lever arm, but do you need more than that?

In either case, can you make your analysis more realistic by accounting for things like friction and air resistance? What about moments of inertia, which are not labeled in Figure 3?

This is a complex physics problem, so there are some references in the Bibliography to help get you started. If you get stuck, you may need to consult a physics textbook, ask your physics teacher for help, or do your own internet search for "trebuchet physics." Once you have derived an equation for the range of a trebuchet based on the physical parameters above, can you come up with any design guidelines or rules of thumb for designing a trebuchet with the best possible range?

Building a Trebuchet

This is probably the most exciting part of investigating how trebuchets work: actually building one! There are many different approaches to building a trebuchet, and you can find many different guides and designs online and in books (see the Bibliography for one example). Before you start building a trebuchet, ask yourself the following questions to help you pick a design:

How much space do you have to test your trebuchet? Do you have a large outdoor area to test a big one? Do you need to build a miniature trebuchet that fits on a tabletop? Or something in between?

What is your budget, and what materials do you have access to? Do you need to use household materials like cardboard, duct tape, and string? Can you make a trip to the hardware store and build your trebuchet with wood, nuts, and bolts?

What tools and safety equipment do you have access to? Will you need help from an adult to use tools like a power drill or saw?

How much time do you have to build your trebuchet? Do you have time to do a fancy design, or do you need to build one quickly?

What should the various dimensions and parameters (lever arm length, counterweight mass, etc.) of your trebuchet be? Can you pick these parameters based on hand calculations or computer simulations (above), or based on design information you found through your own research?

Do you want any of the parameters to be adjustable; for example, a bucket that you can fill with different weights for the counterweight, or a lever arm with notches or holes so you can change the pivot location and adjust the relative lengths of each side (L₁ and L₂ in Figure 3, above)?

What factors can increase the range of a real trebuchet, based on the one you build and test? For a very impressive science project, you could also compare the range of the trebuchet you build to predictions based on hand calculations and/or computer simulations you make (above). How closely do they match? What real-world things (like air resistance, or how exactly the payload is released from the sling) were difficult to account for in your calculations or simulations?

Objective

The goal of this project is to determine how different physical parameters can affect the range of a trebuchet, using hand calculations, computer simulations, and/or physical experiments.

Bibliography

These references will be useful for learning about the physics of trebuchets. Some of these references contain advanced math, including calculus and differential equations, but you can still use them to help you get started.

If you search online, there are many different plans and designs for building a trebuchet. This book also contains some useful designs and building tips:

Autodesk Inventor software is available as a free download for students from:

Ask an Expert

Global Connections

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Science Buddies Staff. "Effect of Trebuchet Arm Length or Counterweight Mass on Projectile Distance." Science Buddies, 23 June 2020, https://www.sciencebuddies.org/science-fair-projects/project-ideas/ApMech_p013/mechanical-engineering/effect-of-trebuchet-arm-length-or-counterweight-mass-on-projectile-distance. Accessed 20 May 2024.

APA Style

Science Buddies Staff. (2020, June 23). Effect of Trebuchet Arm Length or Counterweight Mass on Projectile Distance. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/ApMech_p013/mechanical-engineering/effect-of-trebuchet-arm-length-or-counterweight-mass-on-projectile-distance

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Trebuchet engineering project: use hand calculations, simulations, or experiments to investigate what factors can increase the range of a trebuchet.