Hellenistic military equipment was generally characterized by an increase in size. Hellenistic-era warships grew from the trireme to include more banks of oars and larger numbers of rowers and soldiers as in the Quadrireme and Quinquereme. The Ptolemaic Tessarakonteres was the largest ship constructed in Antiquity. New siege engines were developed during this period. An unknown engineer developed the torsion-spring catapult (ca. 360) and Dionysios of Alexandria designed a repeating ballista, the Polybolos. Preserved examples of ball projectiles range from 4.4 kg to 78 kg (or over 170 lbs). Demetrius Poliorcetes was notorious for the large siege engines employed in his campaigns, especially during the 12-month siege of Rhodes when he had Epimachos of Athens build a massive 160 ton siege tower named Helepolis, filled with artillery.