By W. T. S. Tarver
Technology and Culture, Vol. 36, No. 1 (1995)
Introduction: Traction trebuchets were medieval rotating-beam siege engines; they were powered by a human team pulling ropes and hurled stone projectiles from a sling. Traction trebuchets were entirely unlike ancient Greek and Roman torsion engines which used springs made of skeins of twisted sinew or hair, and they were quite unlike the later medieval trebuchets whose rotating beams were turned by large counterweights. Counterweight trebuchets were the dominant medieval siege artillery, but the survival of useful Roman-style torsion artillery into the Middle Ages is a myth with Renaissance origins. This myth, as well as confusion with counterweight machines, has hampered our understanding of traction trebuchets so much that some have even questioned their existence. I have reconstructed and tested a full-sized traction trebuchet in order to find out exactly how they worked and how they differed from other kinds of mechanical siege artillery.
The historiography of the traction trebuchet is inextricably linked to the contributions of centuries of antiquarians and scholars who have wrestled with difficult sources and baffling terminology. The Renaissance, enchanted with the recovery of ancient texts and knowledge fostered the lingering notion that all things Roman were perfect. The Romans had siege engines; therefore the Romans had the best siege engines imaginable. The flourishing Renaissance mechanical tradition produced “theatres of machines” and similar works by authors such as Konrad Kyeser, Mariano Taccola, and Agostino Ramelli, including the celebrated sketches of Leonardo da Vinci. These works first circulated in manuscript form and later achieved wide distribution through printing. They typically included drawings of fictitious machines which were later confused with real ones, greatly compounding the usual problems of distinguishing image from reality. Drawings of “ancient” siege engines, based on fragments of ancient descriptions fleshed out with artful ingenuity, usually conveyed mechanical cleverness and originality, rather than the details of any sort of living tradition.