Catapults are war instruments that have been used for centuries; the author of the first catapult is not known with certainty, although many scholars agree that their first appearance could have occurred in China. At first, they were operated by human power, with a dozen men pulling a rope to run the mechanism. Later came the trebuchet, an invention attributed to Mardi Ibn Ali al-Tarsusi, a type of catapult that uses the potential energy of a counterweight to launch the projectile further and with more power than with the old catapults. Today, we can find several mechanisms that use the same principle as the trebuchet. In this work, the geometrical modelling, the mechanical analysis, its functioning, and the actual scale reproduction of the device are carried out.