Torsion Engines is a technology in Age of Empires II HD: The African Kingdoms that is unique to the Ethiopians and can be researched at the Castle once the Imperial Age is reached. Once researched, it increases the blast radius of most Siege Workshop units by 0.45 tiles. It does not affect Siege Towers or Battering Rams, but it does affect Capped Rams and Siege Rams, granting them +0.5 blast radius instead of 0.45 (see Gallery for comparison). It also grants +0.3 (up to 0.4 tiles) projectile width (radius) for the Scorpion line.
Torsion Engines is a very helpful upgrade that benefits almost all siege machines the player can build. The Mangonel line arguably gains the most out of Torsion Engines due to the expanded blast radius remedying the unit's inherent lack of precision and making missed shots slightly more forgiving. Attack ground commands become more effective as more enemy units can be caught in the blasts, allowing tactical players to wipe out large contingents of cavalry, archers, scattered infantry, or even multiple siege machines with a single shot. Bombard Cannons also appreciate Torsion Engines and make an excellent siege and archer counter once it is researched. Scorpions are now capable of hitting multiple lines of most units if they are stacked closely to the target in the lateral dimension, as collision size of the units is smaller than the projectile width of upgraded scorpion bolt.
- With update 36906, Scorpion projectile collision size was increased from 0.3 to 0.5 tiles. With update 42848, it was decreased to 0.4 tiles.
A Torsion Siege Engine is a type of artillery that utilizes torsion to launch projectiles. They were initially developed by the ancient Greeks, specifically Philip II of Macedon and Alexander the Great, and used through the Middle Ages until the development of gunpowder artillery in the 14th century proved them obsolete, essentially all non-battering ram/siege tower siege units utilize torsion. It should also be noted that increasing the blast range is inaccurate, as torsions allowed their users to fire and reload faster.