A cannon is a tubular device designed to fire a heavy projectile over a long distance. The introduction of cannons in warfare enlarged the canvass of traditional battles and played, number of times, a decisive role. India has a glorious tradition in cannon technology.
The cannons used in India were either forge welded iron cannons or cast bronze cannons. While bronze casting practice for manufacturing cannons was adopted from the Ottoman Turks, the forge welded canon technology seems to have been developed in India.
Although medieval Indian black smiths successfully used casting in the manufacture of intricate bronze objects, available evidence indicates that few practiced iron casting techniques. The black smith’s lack of interest in casting was likely due not only to the high temperatures required for casting, but also to their mastery over the forge welding technique to produce large wrought iron products. Huge and massive forge welded iron cannons found at Nurwar Mushirabad, Bishnupur, Bijapur, Gulbarga and Thanjavur exemplify the medieval Indian blacksmith’s skill in the design engineering and construction of large forge welded iron products. Western Maharashtra is littered with a number of forts each having several forge welded cannons. Janjira, an excellent marine fort of western Maharashtra, is located on an oval shaped rock near the port town of Murud, 165kms south of Mumbai. Even today around fifty-five cannons are lying in different locations of this fort. Out of these, three are forge welded iron cannons: Kalal Bangadi, Chavari and Landa Kasam which attract immediate attention of all tourists. It is certain that these three massive cannons were not cast, implying that these cannons were made of wrought iron.
There is no specific recorded history of all these cannons, however it is said that, the largest cannon – Kalal Bangadi, 5.4 m in length and 14 tons in weight, was brought by Peshwa’s Army in 1735. This cannon is a muzzle loading type where in the gun powder and the projectile object are loaded from the muzzle i.e. front end. The barrel must have been fabricated separately from the chamber. The outer appearance of the cannon indicates that individual pre-fabricated iron rings were forge welded in order to create the complete cannon structure .The rings exhibit good continuity and the skill of the medieval blacksmith must be appreciated because these rings have been so skilfully forge welded that the entire surface of the cannon appears smooth due to the excellent closure of gaps between the individual iron rings However, pitting corrosion is seen on the surface. It appears that iron rings were forge welded over a solid cylindrical shaft that made the rear portion. The rear end of the cannon is not flat but consists of successively smaller diameter rings presumably to provide impact resistance to the rear section of the cannon. Also near the trunion and front end extra rings are observed. These additional ring assemblies would have provided further strengthening to the cannon. These outer rings appear to have been forge welded over the layers of rings. The total number of rings that make up the thickness of the barrel cannot be easily distinguished by visual observations alone. It is reasonable to assume that there are layers of rings building the thickness of the barrel, based on the design of other similar cannons at Thanjavur and Bishnupur. Thus it appears that the medieval engineers were familiar with the idea of structural design for improved fracture toughness because the solid structure created with successively larger rings would have possessed a better impact resistance compared to a single solid piece of wrought iron. Although handling clamps are visible on the cannon, it is difficult to visualize how this massive cannon was transported. One of the remarkable observations concerning this cannon is that it is almost devoid of significant rusting. The surface possesses a reddish golden hue and the surface is reflective indicating the relatively thin layer present on the surface. This might be attributed to the high phosphorus present in the wrought iron used for making the cannon. It must be noted that no special maintenance procedures are currently applied to this cannon. Despite this, the cannon reveals only pitting corrosion. Under similar conditions, modern mild steel would have corroded severely in a marine environment. Thus the atmospheric corrosion resistance of the cannon is excellent and can be compared with the iron pillar at Delhi. Therefore, it can be concluded that Kalal Bangadi cannon constitutes a marvel of medieval Indian metallurgical skill.
Author and Photographs: P. P. Deshpande Source: Vol 3 Issue 2 (2010)