catapult v. ballista v. onager v. mangonel v. trebuchet
Sunday, December 6, 2009 Catapult is a general term describing any non-handheld mechanical siege engine for hurling projectiles, such as rocks, burning objects, or even the carcasses of animals or people. There are several basic designs for catapults, including ballistae, onagers, mangonels, and trebuchets.
A ballista is essentially a giant, two-armed crossbow. Torsion derived from two thick skeins of twisted cords is used to propel bolts or stones.
The onager (so named because of its kick) or mangonel is the machine most frequently identified as a catapult today. A beam is mounted to a frame and one end is run through a skein of rope. A payload is placed in a bucket or sling at the other end of the beam. When the beam is rotated in the frame, the rope applies torsion, and when released, the beam rotates until it hits a stop, at which point the projectile is fired. Mangonels throw projectiles on a low trajectory at a high velocity with limited accuracy. Consequently, they’re best-suited for attacking large, stationary targets like walls.
Unlike the aforementioned devices, a trebuchet is based on leverage instead of torsion. A heavy counterweight is placed at one end of a pivoting arm, close to the fulcrum, and a payload is placed in a sling at the far end. When the counterweight is dropped, the arm rotates quickly, and the payload is released. Trebuchets can be used for hurling missiles over walls.