Trebuchets and their modern use

A highly detailed model of the Stirling Warwolf medieval trebuchet, like the one King Edward made in 1304 which leveled a section of a castle wall. (Photo: Ron L. Toms, http://www.trebuchet.com)

The Middle Ages, spanning roughly from the 5th to the 15th centuries, are a romantic age, spurring forth tales of knights in shining armor fighting over castles protected by high stone walls and drawbridges over perilous moats. But while one might think all vestiges of medieval times were left in the past, there is one holdover that only seems to be increasing in popularity: the siege engine known as the trebuchet. While medieval times are not known for their technological advances, this clever piece of machinery has had lasting implications.

The ancient precursor of the trebuchet was the stave sling, also known as staff sling, which was a simple sling on the end of a staff for hurling rocks. The catapult, also known as a traction trebuchet, was a much larger version of the stave sling, generally with a group of men used to pull down on ropes that would then propel the object of choice, usually large rocks, at castle or city walls.

The counterweight trebuchet was a double-armed machine that improved on its predecessor. Instead of a group of men pulling down to launch the payload, the machine used gravity and a large counterweight to launch an object. The placing of wheels allowed the machine to move forward and backward with the motion of the arm and swinging action of the counterweight.

The first recorded use of a trebuchet is in Europe in the 12th century. It was the machine of choice for the siege of castles, and far eclipsed the range of the simple catapult. The catapult used potential energy stored in twisted rope to hurl objects. While catapults could be reloaded more quickly, their range was less and their payload lighter.

Trebuchets were very heavy and often built on-site, and were not designed to be mobile, but to lay siege to a castle or city and destroy its protective walls. The counterweight greatly extended the range of the trebuchet so that it could remain far enough from its target to be out of reach of serious harm, but still close enough to unleash its deadly terror.

Trebuchets were known to hurl stones weighing 200 pounds up to 300 yards. King Edward I built the largest known trebuchet, called Warwolf, to assault Stirling Castle in Scotland after a long siege in 1304. When the inhabitants saw what was being built, they tried to surrender based on the sight of it alone. King Edward refused to accept their surrender, however, until after he had a chance to use the machine, which leveled a large section of the castle wall.

Trebuchets are an example of a first class lever, which places the fulcrum in the middle with input on one side and output on the other, like a seesaw. Examples of modern day first class levers include crowbars, pliers and scissors (both double levers), bottle openers, bicycle hand brakes, and hand trucks.

Today trebuchets are used as teaching tools in high schools and colleges to learn about load, force, fulcrums, velocity, gravity, and parabolic arcs. They are also used as recruiting tools to lure students into engineering programs. Designing a trebuchet is an assessment of mechanical design and engineering skills. Testing a trebuchet is not only a learning tool, it is also fun.

While in medieval times trebuchets were used to hurl stones, manure, and even the bodies of enemies, today they are used to hurl pumpkins, cabbages, and the occasional piano or car (like in this video of the annual Punkin Chunkin). Whether used as a teaching tool or just for fun, trebuchets have proven to be a timeless engineering marvel.