Making Trebuchets

040814trebuchetTrebuchets are great engines of war that hurl huge stones to crush the enemy. The Gondorians used these devices to protect the great city of Minas Tirith from anyone trying to beiege them. This article shows how to make your own trebuchets from simple and readily available materials, such as bamboo chopsticks. Excellent economy if you want to make a large group of them.


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Making Trebuchets

Games Workshop make a very nice trebuchet model which is well worth obtaining. I have a couple, but needed to supplement these with lots more to line the walls of my Minas Tirith model.The cheap shop, bargain shop, $2 shop or whatever you like to call them are great sources of cheap materials for building models and scenery. A packet of bamboo chopsticks and a packet of bamboo skewers provided the main ingredients for a huge collection of trebuchets.

Chopsticks come with different styles. I went for the ones that were mostly square and just tapered over a short section at one end. This end was used for the main pivoting beam, with the tapered end used at the back for attaching the sling. You can just use a straight section if the chopsticks you get are not like this.

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The other end of the chopstick was already slightly rounded. This made an ideal piece for the central uprights. If your pieces are have flat ends, that is okay. You can either leave them like that or round them yourself with sandpaper or a metal file. A hole was drilled near the top of each of the two uprights and a hole drilled near the end of the main beam. A length of bamboo skewer was used to act as the shaft for the main beam to rotate on. Glue this in place with PVA glue. Before the glue dries, rotate the main beam to the angle you want. If you are making several trebuchets, then glue them at different angles. This gives a realistic appearance of the trebuchets being at different stages of the firing process.

The bamboo sections were glued together with PVA glue. I decided I wanted some of these joins to be stronger so I drilled holes and used short lengths of bamboo skewer to act as a dowel pin. This is probably not necessary, but being an engineer I like even my model constructions to be strong and able to survive the handling of many games.

Cut four pieces of bamboo chopstick with 45 degree ends. These are glued in place to act as the cross bracing to support the main uprights.


How a Trebuchet Works

The trebuchet imparts velocity to the stone through a combination of movement. The first motion occurs through the rotation of the main arm. A heavy counterweight is attached to the front end of the main arm via a pivot. A heavy stone is attached to the other end of the main arm using a sling.

To fire the trebuchet a stone is loaded into the sling (more of this below). The counterweight is then raised by the crew winding up ropes onto a drum. The drum is locked into place. When the trebuchet is ready to be fired, a lever is used to allow the rope to disconnect or sometimes just allow the drum to unwind rapidly. The counterweight drops and accelerates under gravity. The main arm rotates to provide the base velocity to the stone.

To this is added the action of the sling. The sling will often be leather or thick hide which is wrapped around the stone. One end is fixed to the rear end of the trebuchet main arm. The other end of the sling is brought around the stone and a ring is slipped over a hook. As the main arm on the trebuchet reaches its highest point, the counterweight reaches its lowest point. The sling continues to rotate with the stone in it. The hook and ring is designed so that the ring now slips off the hook. The sling opens and the rock is hurled towards the target.

The slinging action adds extra energy to the stone. It is this combination of rotating arm and slinging action which makes it a trebuchet rather than a catapult. The trebuchet is more dangerous and can hurlstones farther than if it just had a fixed arm.


Making Sling,Stone and Counterweight

Below left can be seen the stone and sling. This was made from polymer clay (such as Fimo or Sculpey) which is often sold in art and craft shops. Even some of the bigger newsagents stock it. This is moulded like plasticine and then baked in the oven on low temperature for around 10 to 20 minutes (depending on the brand). "Green stuff" could also be used. Although "green stuff"is a little more expensive, it avoids the risk ofburns from a hot oven.

Two pieces were made for each trebuchet. One is just rolled into the shape of a stone. Do not make it too round, otherwise it looks more like a bowling ball than a rock. Alternatively you can make it up into the shape of some smashed masonry or dressed stonework from Minas Tirith, as was seen in the film "Return of the King". The other piece is just a rectangular strip which represents the leather sling.

Take a short piece of thick multi-strand cotton or very thin cord. This represents the rope. You could also use wire. The latter might be preferable as I sometimes find that the cotton twists and does not hold the sling straight. If you find this to be a problem, a way to fix it is to use some slightly watered down PVA glue on the cotton. Prop the sling in the correct orientation whilst the glue dries. You will then have the sling stay in the correct orientation.

Lay the string and rock in the sling. Wrap the sling around. Add any texture you wish. Bake in the oven (if polymer clay) or allow to harden (if "green stuff"). Glue it to the back (tapered) end of the main arm.

The second photo above shows the counterweights being made. This was made using a strip of 5mm foamboard. The foamboard was cut into three lengths; one long and two short. The three were glued together with a little PVA.

Matchsticks were then used around the outside to represent the timber casing. When dry, hollow out some of the foam from the upper piece of foamboard. This is to allow the paper sides of the foamboard to overlap aroundthe sides of the end of the main pivot arm.Curve the ends slightly with scissors. Glue the counterweight assemblyin place near the end of the main pivot arm. Make sure that the counterweightis hanging straight down otherwise it will look unnatural.

When the glue is thoroughly dry, stain or paint the trebuchet.

After making the first one to get the hang of it, you can easily make lots of them by setting up a bit of a production line, as seen in the photos.