Types of Catapults

Catapults were large devices for hurling stones or other objects. Hurling seems to be the proper term most people use when referring to catapults. An object that is hurled is not launched by any chemical means, like gunpowder or greek fire. With this definition, many devices fall into the catapult category, but there are three main categories that usually come up when talking about siege engines.

Siege Engines

A siege engine is a device that is designed to break or get around castle walls or other fortifications. Basically, big machines used to break through a castle wall. Catapults as siege engines fell into three styles: Onager, Ballista and Trebuchet. But these three styles break down into more sub-types.


Catapult - Onager

The Onager is what we usually think of when we hear the term catapult. The onager:

  • is a torsion catapult, so uses twisted cords to power the projectile
  • has a single arm
  • has no wheels
  • has a sling at the end of the arm (not a bucket)
  • has a variation called a mangonel which is a tension catapult

Learn more about the Onager.


The Ballista resembled a giant crossbow and could hurl stones or giant arrows. The ballista:

  • is a torsion catapult, so uses twisted cords to power the projectile
  • has two arms
  • has no wheels
  • is also called a scorpion
  • has a variation called a springald which has inward swinging arms

Learn more about the Ballista.


Catapult - Trebuchet

The trebuchet was a very tall catapult that used a heavy counterweight to hurl stones. The trebuchet:

  • is a gravity catapult, so uses a heavy counterweight to power the projectile
  • has one arm with a fulcrum
  • has wheels
  • has a variation called a traction trebuchet which does not use a counterweight

Learn more about the Trebuchet.


Catapult Energy Storage Types


The balista and the catapult derived their projectile force from the recoil of tightly twisted cordage, while the trebuchet owed its power to the utilisation of the force of gravity of a heavy weight.

Sir Ralph Payne-Gallwey, The Crossbow

With ancient catapults, there were four main energy storage types:

  • tension – usually bending wooden arms and letting them spring back
  • torsion – using twisted ropes to spring the arm forward
  • gravity – uses a falling counterweight to propel the arm forward
  • traction – powered by people pulling on ropes attached to the arm

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