The Traction Trebuchet Spotters Page

What was a Traction Trebuchet?

Let's start simply...
Most people describe trebuchets of any kind as giant see-saws where pulling one side down causes the other side to go up - and throw what ever is on that side.
To nail things down a little more exactly, we'll try to make our definition a bit more concise:

A trebuchet is a missile-throwing machine where a long pivotted beam, much longer on one side, has the short side pulled down causing the long side to rise quickly. A sling attached to the end of the long side of the beam whips over, releases itself and hurls the projectile it held.

On a "Counter-weight" Trebuchet the power used to pull the short end of the beam down is gravity - because the trebuchet builders hang an enormous weight (such as a large box full of stones and earth) on it

With a Traction Trebuchet the power is human muscle. A team of people haul down on ropes hanging from the short end of the beam. This bundle of ropes is what poetically-inclined Eastern writers have compared to a witch's hair.
A handy feature of a traction trebuchet is that, while a counter-weight machine has to have its weighted beam slowly winched back into the start position, the pulling crew of the people-power machine can just pull on their ropes again and make the beam fall back into place.

Let's have a look at the parts of a traction trebuchet...

The Anatomy of a Traction Trebuchet

The Beam-end & Ropes This is how the crew (seen below) get to haul down on the beam. The short end of the beam usually has a kind of rake-like spreader to which the hauling ropes are attached. The extra width of this "hay-rake" gives the crew a bit more room to work. Even so, on a large crew a few elbows and ears must accidentally meet...		The Axle and Support For the crew to be able to make the beam swing around above their heads, the axle has to be supported high above the ground even on a small machine. In this case the wooden axle is held by a square frame that is mounted on the top of a single pole. In other machines two large posts - one each side and rising all the way from the ground - hold up the axle and beam		The Sling Release A trebuchet is not just a lop-sided seesaw - the sling adds a huge amount of extra whip to the shot and can double the range obtained. The way the sling works is simplicity itself - the pouch holds the stone projectile as long as both cords are connected to the beam end... and one of the sling cords is designed to fall off during launch. (see the loop and hook?)
The Hauling Crew These soldiers are the power of the machine. They must all haul down on those ropes above their heads at the same moment, causing their end of the beam to suddenly drop and the much longer other end of the beam to rise and whip over.		Protection The trebuchet and its crew are close to the enemy - perhaps only 100-200 metres away ... and that's within bow-range. If they are lucky they might have wooden or hide-covered defenses to protect them. If not, they'll just have to hope that "covering fire" from their own archers will put the defenders off their aim.		The Sling Handler This crewman has to re-hook and load the sling pouch after each shot. Assisting him will be another crew bringing up new stones to feed the trebuchet. Another part of his job is to hold onto the sling during launch. This helps make the crew's efforts more synchronised and, by changing the angle he holds the sling, he can aim the shot a little.

Traction Trebuchet Spotting: Different Shapes and Kinds

The "Tower" type This shape, which looks a little like a modern oil-drilling rig or windmill stand, was probably the first to be used in Europe. My sketch is based upon a drawing done sometime in the 7th or 8th Centuries in the region around modern Turkey. The defensive wall on the front (covered with a fire-proof layer of freshly removed animal hides) is based on Archbishop John's description of the siege of Thessaloniki in 597 - although here I have only drawn the wall on one side. In John's account three sides were covered, with only the back being open. You can see the original here This design allows the crew (who stand inside the structure) to approach the target closely with considerable protection. If the besieged townspeople had their own artillery, a fire bomb thrown from their trebuchet could destroy a plain wooden machine. If this was likely to happen a fireproof coating of the sort illustrated would have to be made.

The Single Pole type An elegant-looking design, this one is light, portable and lacking in any in-built protection. The principle of this machine (based on the St Petrus de Eboli one shown in the "Anatomy" section and described more fully here) was that the team whipped the short end down by pulling their ropes (tied to the triangular wooden "spreader"). The beam rotated until it struck the frame of the trebuchet. If the beam was light, the pole and frame flexible and (perhaps) some sort of padding was provided, then the repeated impacts would not destroy the machine. These machines turn up in drawings of around the late 12th Century in Europe (although they appear in Chinese illustrations much earlier).

The Two-Post type This sort of machine - apparently tougher and cruder - appears in Western Europe and looks to be the sort shown on the Carcassonne cathedral and may be the type shown in the mid-13th Century Maciejowski Bible. In this design the beam can pass between the uprights of the frame and, rather than an impact, it is the crew's ropes that stop the beam after the rock is thrown. I have left the base largely undrawn in this sketch, as the base is not shown well on the originals. Grey Co experiments have found that sideways bracing timbers, in addition to the backward facing ones shown, make the machine much less "wobbly" and more consistent in its aim.

The Heavy type This is just a heavier (and probably larger) version of the two-pole machine, its support posts being replaced by a sturdy tower. In this it is almost a return to the old tower style - although much more heavily constructed. Here also the beam can pass between the legs of the support and stopping the beam is up to the crew and their ropes. Note the size of the end timber on the triangular "spreader". Not only would this be immensely strong, but its weight would help balance the weight of the heavier beam used. This sketch is based on the machine shown here.

Spreader Orientation: "Rake" or "Axe"

Although I have chosen to show only horizontally arranged rope attachment triangles on the drawings in this page (what I have called the "rake" arrangement), a traction trebuchet can work with the triangle turned to a vertical arrangement. Here we look at the two orientations and recognise that some medieval drawings can suggest one or the other way - or leave the viewer mystified as to how it was supposed to go.
"Rake" - Horizontal Arrangement	"Axe" - Vertical Arrangement
Advantages: All the pullers' ropes are joined to the beam at the same height, so they all reach their maximum leverage and pull at the same moment of the launch - giving a potential for a more "explosive" effort. The triangle also supports the axle, making it easier to build the axle/ahaft assembly rigid. Movement here can have a large effect on the side-to-side accuracy of the machine.	Advantages: Because the wooden triangle or spreader goes between the uprights sideways, a shorter axle can be used. The pullers each reach their maximum and minimum efforts at slightly different times thus giving a more even and longer application of power. This may have been an advantage in machines throwing heavier projectiles.
Disadvantages: The pullers all reach the point where their efforts have no effect (when their ropes are in line with the beam) at the same time, after which the beam is "coasting".	Disadvantages: The pullers' maximum efforts and leverage cannot occur at the same time, losing the "explosive" team burst of power.

Crew Protection

It's interesting that the earliest machines seem to have built-in protection for their crews, while the later ones do not. Is this a true picture? Assuming for the moment that it is, here are a few thoughts on the matter:

The crew don't matter...

A good Hollywood view of Medieval armies, but not one consistent with cases where soldiers would be paid bonuses for dangerous acts (such as carrying stones or bundles of sticks to a moat to fill it).
A limited exception to this might be the Mongols, who were reputed to use prisoners to crew their siege engines.

The crew is in armour...

This is certainly the case with the Petrus de Eboli drawing, where the crew are obviously soldiers and are wearing helmets and mail. Unfortunately, mail is not particularly good at stopping arrows - especially if the range is short and the arrows needle-pointed... although mail over padding will offer considerably better protection.
The rather odd and probably unreliable drawing being used in this page's title shows the crew holding or wearing large shields. As long as it didn't get in the way of the rope hauling or the other crewmembers, I expect that this could help.

The crew are out of range...

Certainly an increase in range of the traction trebuchets might see the crew out of the range of the hand-thrown missiles that tormented their ancestors, but traction trebuchet range was always likely to have been comparable to bow range.

The crew are protected by screens...

Large wooden hoardings and tall woven baskets filled with soil (basically Medieval sandbags) were used in a variety of roles to protect vulnerable attackers. Whether these were used with traction trebuchets isn't shown.

The crew have "active protection"...

If the attacking traction trebuchets and archers could effectively keep the defenders' heads down then the chances of one of them getting off a good aimed shot would be greatly diminished. Having a body of archers nearby would also provide protection should the defenders "sally forth" and attack the attackers.

Russell Miners
This page was last edited Jan 2000