Frontispiece: Joseph F. O'Callaghan
Illustrations 1–11 can be found between pages 200 and 201 in the essay “The Hybrid Trebuchet: The Halfway Step to the Counterweight Trebuchet” by Paul E. Chevedden.
1. The city of Naples, defended by Richard, count of Acerra, is besieged by King Henry VI of Germany in 1191. Henry's army bombards the city with stone-shot launched from a pole-framed traction trebuchet. The machine is operated by a pulling-crew of eight knights and a “shooter” holding the sling. The defenders prepare to launch stone-shot from a similar machine mounted on a tower. Peter of Eboli, Liber ad honorem Augusti. Bern, Burgerbibliothek, MS 120, fol. 109r.
2. A hinged counterweight trebuchet from Bellifortis, a treatise by Conrad Kyeser of Eichstät, which was left incomplete at his death in 1405. The main beam, counterweight box, sling, projectile, windlass and framework are all clearly visible. The machine has some of its dimensions numbered; the long arm of the beam is forty-six feet, and the short arm eight. The prong at the end of the long arm, which is essential for the release of the sling, is not depicted. Instead, both cords of the sling are incorrectly shown as attached to a ring at the extremity of the long arm. This massive machine used a simple peg-and-hole catch-and-trigger device to retain and release the beam. A hole is drilled in the base of one of the machine's triangular trestles, shown in the foreground, for the insertion of the peg. A restraining rope, attached to the base of the other triangular trestle, is drawn over the long arm of the beam at a point just above the windlass and is looped over the bottom end of the peg. When the peg is lifted out of its socket, the looped end is released, and the beam flies free. Trebuchet beams were often banded circumferentially with iron (as shown in the illustration), or lashed with rope, to help withstand splitting. This type of machine was identified in Arabic historical