The catapult is a military weapon capable of launching large arrows or javelines or spherical stones at great distances (around 200 m). The strong chord of a powerful bow set horizontally was pulled back mechanically (with a system of levers and cranks). Bending and axial energy was thus accummulated, and when set free it launched the projectile. This technical invention took place at the time of the Tyrrant of Syracuse, Dionysios the Elder (399 B.C.).
Later, probably by Philippe II (~343 B.C.) two torsion springs (made of twisted ropes) were added which were twisted by the very bending of the arms of the bow. In the next phase the springs released their energy increasing the range of the weapon.
The model shown in this exhibition is a later version (Hellenistic) of catapult in which the energy is accummulated only be means of two torsion springs.