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Originally Posted by Jim McDougall
Further encouraged by Philip's insight, I found what I could online and recalled some time ago, another huge cannon, Mons Meg in Edinburgh, which is apparently a 'bombard'.
Mons Meg, which is 15ft. long and a 20" barrel, firing a 369 Lb. ball.
Jaivana is 20.2" long and an 11" barrel firing a 11 pound ball.
It is said that the firing of Jaivana cannon took 220 lbs of powder , which had the handling soldiers taking refuge in water barrels to prevent burns from the intense heat generated. While Mons Meg had huge caliber, the Jaivana had range of up to 22 miles if I have read correctly.
The Mons Meg cannon apparently burst in 1680, rendering it effectively inert and I wonder if that was from the manner of construction which consisted of iron staves rather than solid cast iron.
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You're most welcome, Jim. Thank you for taking an interest, I know that this subject is outside your bailiwick. It's great that you presented a comparison piece, Mons Meg, with essential technical info. Here are some comments on the interesting points you raise.
1. First, a question for you. Do you have R D Smith / R R Brown,
Bombards: Mons Meg and Her Sisters (Royal Armouries Monographs series, 1989)? It quite clearly lays out the elements which define a bombard, a type of mega-artillery which originated in the final decades of the Middle Ages. We can see from this that they can be distinguished, by their design and construction, from large cannon of later eras. The most obvious difference, and which affected ballistics and field performance, was the fact that bombards were constructed of
forged wrought iron, consisting of longitudinal staves forming a tube stabilized by an outer shell of forge-welded hoops and reinforcing mouldings. (hence, in English the word for the tubular portion of a gun is "barrel"). The inherent limitations of this method led to its abandonment by the turn of the 16th cent. in favor of
cast pieces in bronze or iron.
2. The bursting of Mons Meg in 1680 makes a modern reader wonder who might have thought that it was still safe to shoot over 230 years after its manufacture, and apparently being exposed to the elements for much of that time. Here is an object built up of numerous iron pieces welded together with heat and hammer (a remarkable feat in and of itself) -- all those mating surfaces, interstices which are subject to slag inclusions, incomplete welds, etc., coupled with the corrosive effects of atmospheric moisture for many years...
Not to mention that between the mid-1400s and 1680, gunpowder manufacture had improved markedly. Early powder was ground to the consistency of flour or "meal" -- it tended to settle into its constituent ingredients during transport, and its consistency impeded efficient combustion because insufficient oxygen got into the mixture. During the 15th cent, it was found that powder of "corned" or granular consistency made for faster and more consistent rate of ignition: therefore more POWER. However this increased the internal pressure in the barrel, making the bombard construction woefully inadequate.
3. Re projectile size and weight. Because of the different ballistic profiles of bombards and later cannon, comparing bore diameter and weight of shot between the types is not all that meaningful. The reason that most large cannon made during the 16th cent. and later have smaller bores on average* than earlier bombards is that gunners realized, with the improved ammunition at their disposal (corned powder and precisely cast iron balls), that a shot traveling at greater speed packed more
projectile energy and therefore more destructive force, not to mention being capable of greater range and accuracy (the latter due to a more consistent burning rate of granular powder).
* leaving mortars out of the discussion for now, since these specialized guns have a totally different role and function than the types of artillery we are considering here.
4. Performance of Jaivana: 22 miles is an impossibly long range. I recall from reading the text in Fernando's post that estimates vary considerably, but 3 miles is a more realistic figure. A lot of this depends on the quality of the powder used, and the elevation to which the tube could be raised. It is an axiom in ballistics that the maximum range that can be achieved by a gun,
ceteris paribus, is at an elevation of 45 degrees, this principle proved by the Italian mathematician Tartaglia in the 15th cent. (he is said to have invented the gunner's quadrant which became essential in gunnery practice for the next 400 years). Do we have any idea of how the one test shot with Jaivana was conducted?
5. Fuel economy: 220 lb of powder to power an 11-in. diameter cannonball sounds like an awful lot. Would be interesting to compare this with the powder charges of the largest fortress guns of the 18th cent.; British and French gunnery manuals of the era would have this info. I'm wondering if for this firing, the earlier type of fine-consistency powder was used. For instance, bombards required a prodigious amount of gunpowder in order to function (the powder chambers of these cannons is a separate part of the bore so it's easy to estimate the volume of powder required) simply because the relative weakness of the explosive required it.
Now, for the gunners having to dunk themselves to avoid being toasted by the blast. I wonder where they were standing when Jaivana was touched off. I can imagine a frightful muzzle blast but who would stand near the front end of something like this? For a barrel that's 20 feet long, one would think that somewhere to the side and rear should be sufficient, and that ear protection would nonetheless be the order of the day.