Balls deep

Wrote this post about a month ago but then forgot about it. If you like cannons give this post a shot! But be warned you might be bombarded with puns

When walking on the ramparts of the Scottish castle of Edinburgh I came across this big lady:

and here is a much nicer photo without all the tourists:

Photo by Lee Sie CC BY-SA 2.0

She goes by the name of Mons Meg. Mons being the (now) Belgium city where she was born in June 1449 [1]. The reason to why she is called Meg is unclear. Meg might be short for the Scottish Queen, Margaret of Denmark the spouse of James III of Scotland, or maybe it just has a nice pet name for a cannon [2]. Anyway, Meg megs her sound great.

Meg's life story

The bruised and uneven barrel show that she is an old lady who has seen quite a bit of action in her prime days. When she was in working condition she could take big massive balls of approximately half a meter down her barrel; these big balls would be made of stone and weigh approximately 130-140 kg or 160-170 kg, depending on the type of stone used. To this day it ranks among the largest calibre cannons in the world, she is a high calibre lady [3].

In 1680 she had one ball too many down her barrel and one the iron rings holding the cannon together burst [4]. Reforging broken or cracked pieces of metal is extremely difficult, even for just a small sword. So the burst rendered her completely useless and she turned into a decorative piece of history. There might have been some foul play in her destruction. The Scottish annals state that to welcome an English duke an English cannoneer had loaded the charge on the day of her destruction. Since for guys the whole world is a who has the biggest game it is suspected that the English deliberately overloaded the cannon because they felt embarrassed about their tiny cannons; a blast for the English.

Meg's tale

Now Mons Meg is not in working condition so the effectiveness of Mons Meg purely relies on historical records. Sir Walter Scott claims that when it was used to besiege Threave castle the first cannon ball passed through the castle and severed the hand of a Duchess in the process [5]. Which, if true, would be an amazing achievement since Threave's castle wall is a 3m thick stone wall!

A true tale? Let's do science

When I was googling Mons Meg I found the following research article which might shed some scientific light on this tale: The ballistic performance of the bombard Mons Meg by I. Lewtas et ali [6]. In brief, this research article models how well a castle wall would hold up against a single shot of Mons Meg. The modelling consists out of three parts:

1. the internal ballistics: the muzzle velocity of the cannon ball after ignition of the gun powder,

2. the external ballistics: the trajectory of the cannon ball in flight

3. the terminal ballistics: the cannon ball's trajectory after impact on the castle wall and the structural effect on the castle wall.

For (1) and (2) lots of simplifications are made to arrive at something which can be modelled on a computer. However, these simplifications are made with the mindset to obtain the optimal conditions for when the cannon ball hits the wall, i.e. the highest possible impact velocity. To model (3) the authors consider two types of wall: a modern concrete wall and a triple layer wall consisting of only interlocking bricks. A real medieval wall is a bit in between those two types; it consists of interlocking stones and rocks with mortar in between. But modelling stones and rocks with mortar is complicated so it makes more sense to model ideal cases. Both of the idealised walls have thickness less than the wall of the tale since the thinner the wall the quicker the computer can simulate.

The result

Assuming optimal circumstances they found that the cannon ball is unable to pierce through the idealised wall. Morever, in the case of the modern concrete wall the cannon ball does not penetrate the wall deeper than the ball's radius! So not even balls deep.

This result does not really come as a surprise since the castle in question does not show any cannon damage. Full penetration was not achieved :o)

References

[1] C. Gaier. The origin of Mons Meg. J Arms Armour Soc 5(12), 425–31.
[2] J. Headley. About Cannon. Harper's New Monthly Magazine 25, 693-607
[3] https://en.wikipedia.org/wiki/List_of_the_largest_cannon_by_caliber
[4] R. Chambers. Domestic Annals of Scotland. Edinburgh : W & R Chambers. p. 330
[5] R. Smith, R. Brown. Bombards: Mons Meg and her sisters. Royal Armouries Monograph number 1. Royal Armouries.
[6] I. Lewtas, R. McAlister, A. Wallis, C. Woodley, I. Cullis. The ballistic performance of the bombard Mons Meg. Defence Technology 12, 59–68

Merchandise :D

There is a MathOwl shop which sells my artsy fartsy stuff. If you got some spare money head over there. I have really cheap stuff available like these stickers They are an absolute hoot.

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