Issue 50

A. Kakaliagos et alii, Frattura ed Integrità Strutturale, 50 (2019) 481-496; DOI: 10.3221/IGF-ESIS.50.40 482 their deployment. Female gun names were typical such, as “ Dulle Griete ”, the Angry Margherit, from the City of Ghent in today Belgium, casted in 1452, “ Mons Meg ” from Edinburgh Castle in Scotland casted in 1449, “ Griete ” from the Duchy of Burgundy casted in 1431 and “ Signora Amedea ”, bombard deployed by the Duke of Savoy in 1426. Occasionally, some bombards carried bizarre names such as “ Il Deluvio ”, the downpour, or “ Non piu parole ”, hence, no more talks. The fall of Constantinople can be considered as a bench mark in City Siege warfare in the European theater of operations. Passing the mid of the 15 th Century, stone throwing bombards were deployed more often in several city sieges in Europe. Typical example of late medieval siege in Italy, is the assault on the fortified position of Rocca di Castelletto. Herein, on May 28, 1464, Francesco Sforza deployed massively bombard artillery against this position. The bombards “ Corona ”, the Crown and “ Liona ”, the Lioness, both from Pavia, “ La Bissona ”, the Bison, of Milan, together with “ San Giorgina ” and “ Golia ”, the Goliath, both from Genova, were deployed. The bombards devastated the heavy wall fortification after only 4 hours of bom- bardment and opened a wide gap in the fortified wall of 3.6 m thickness (12 piedi Romani , an Italian foot equals to 0.30 m). The deployment of bombards against Roman type fortifications, which typically projected heavy stone walls perpendicular to the enemy attacking effort and line of advance, had catastrophic results on the City defenses, as Roman City Walls could no more block and repel an attacker. The use of bombards posed a type of asymmetrical threat to fortified positions equipped with Roman Type fortifications. This threat was to be mastered years later by Sébastien Marquis de Vauban (1633-1707), whose innovative fortification system counterbalanced the strength of the Siege Artillery. During the Siege of Constantinople in 1453, a Bombard with huge dimensions was deployed. The Gun was ordered by Sultan Mehmet II and manufactured by Orban, a skilled master craftsman from Hungary. Bombards often tended to explode inflicting severe casualties to friend and foe. The dangerous situation develops during the ignition of the gunpowder placed inside the gunpowder chamber. According to historical reports, Orban’s gun had the same fate, killing both Orban and the gun crew. The present paper deals with the investigation of the causes who potentially may have led to a fatal failure of Orban’s Gun. In order to focus on the structural response of the gun powder chamber, as this part of the gun was suspect for potential gun failure, it was necessary to numerically reconstruct the weapon and evaluate gun ballistics and effect on target. The results were compared to contemporary to the siege, Byzantine and Italian historical reports, thus identifying gun dimensions, gunpowder charge and force capacity of the exploding gunpowder inside the gun chamber. With those factors confirmed, powder chamber structural response was analyzed considering the combined action of blast pressure inside the powder chamber together with associated temperature effects produced by powder ignition. O RBAN ’ S GUN RECONSTRUCTION verall gun dimensions were assessed on the basis of historical reports and were compared to the existing Darda- nelles Gun at Fort Nelson Museum, U.K (Voice of the Guns Gallery, Object Number: XIX.164), an Ottoman bombard casted in 1464. Additionally, Orban gun dimensions were cross checked using the contemporary to the Siege gun classification system proposed by Francesco Giorgio Martini [7]. It was considered that Orban’s gun consisted of two parts, casted separately, with the cannon powder chamber shorter than the barrel. The split cannon was assembled in- situ after transportation as reported by Critovoulos [3]. The gunpowder charge p was estimated at 177 kg, adequate to fire a granite cannonball with a diameter at 752 mm and a corresponding projectile weight B of 600 kg (Table 1) - see Barbaro [1], Chalkokondyles [2], Critovoulos [3]. Information given by the Venetian physician N. Barbaro [1] (Venice, 1420-1494) dealing with size of the cannonball and cannon overall dimensions when compared to numerical results of present paper lead to the conclusion that Barbaro had actually measured the size and weight of the cannonballs. Based on the geometrical data for Orban’s bombard as presented in Table 1, it was verified that the ratio of powder chamber thickness t 1 =648mm to barrel thickness t=200 mm was at a ratio of 3.24, thus, corresponding on the average to 2φ, where φ equals 1.618, the golden ratio. Correspondingly, the ratio of total gun length at 9200 mm to barrel length at 5800 mm is close to φ (Table 1). L G (mm) L (mm) c (mm) B (kg) p (kg) d (mm) D (mm) D 1 (mm) D 2 (mm) t (mm) t 1 (mm) k (mm) 9200 8552 2752 600 117 752 248 1152 1544 200 648 648 Table 1 : Schematic representation of Orban’s Bombard and geometrical parameters. O