Mechanical behavior of the imperial carroballista Francesco Penta, Cesare Rossi, Sergio Savino Department of Industrial Engineering, University of Naples —“Federico II”, Via Claudio 21, 80125 Naples, Italy article info abstract Article history: Received 15 February 2014 Received in revised form 30 May 2014 Accepted 31 May 2014 Available online xxxx A reconstruction of an artillery piece of the Roman Imperial Army and a mechanical study of the device is presented. The reconstruction is based on some bas reliefs on the Trajan Column and the Aurelian Column and on the investigations of some authors. By means of a mathematical model of the machine, the mechanical behavior of the machine itself and hence the range figures of possible projectiles are computed. The study shows that such a lightweight and cart mounted war machine represented a powerful and effective close support artillery piece for the Roman Imperial Legions. By means of a finite element code the torsion springs constituting the elastic motors of the machine were also analyzed. © 2014 Elsevier Ltd. All rights reserved. Keywords: Mechanics of ancient machines History of Mechanism and Machine Science 1. Introduction Throwing machines are among the most studied devices by those who investigate on ancient technology (see e.g. [1–25]). An in- teresting example of throwing machine is represented by the carroballista. The working principle and the mechanical design of this machine are still somehow mysterious and just in the last few years, investigations on this possible mechanical design were carried out [20–25]. From a historical point of view, the Roman imperial carroballista was developed in the I century A.D. and represents the first example of mobile artillery. It was very similar to the cheiroballistra or manuballista [Iriarte, Russo] but was mounted on a chart in order to provide a quick deployment of artillery piece to obtain a close support to the infantrymen. In this sense it represents the first example of infantry support gun (or battalion gun) that was then developed in modern (18th–20th century) warfare. In the paper some hypotheses are done on the design of that machine, based on ancient bas-relief (Trajan and Marcus Aurelius columns, Fig. 1) and on the studies of several authors, in order to evaluate the mechanical behavior and the performances of the machine itself. 2. Design of the carroballista 2.1. General considerations Based on some authors' previous studies [2–4] and on several investigations by other authors, the authors supposed that this ballista (see Fig. 2) was based on a palintonon design, as already suggested in [20–26]. As it was shown in a previous authors' study [4], in fact, this design, having the arms inside the machine main frame, is more efficient because the arms' rotation angle is wider than that one of an eutitonon. So it is reasonable to suppose such a design for a machine that should develop enough power in small dimensions. Mechanism and Machine Theory 80 (2014) 142–150 E-mail address: cesare.rossi@unina.it (C. Rossi). http://dx.doi.org/10.1016/j.mechmachtheory.2014.05.006 0094-114X/© 2014 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Mechanism and Machine Theory journal homepage: www.elsevier.com/locate/mechmt