Danish cannons for 3D printing

[Waldemar]

 

33 minutes ago, Beckmann said:

Hi Thorbjørn, 

This is a phantastic and very impressive collection. Well done.

Matthias 

 

Yes, absolutely. Until quite recently, such effective 3D modeling was not possible. If you do decide to make these 3D models from the era of Christian IV available, I will also download them. It is possible that I will also find a use for these models.

 

 

7 hours ago, TJM said:

@Waldemar, thanks you so much! This does make sense - at least it is completely systematic and, which is more important, practical from a real-world use perspective. 

 

And while your numbers vary from Blom in the outer ranges, as you mention, they are close enough to still 'fit' the known nominal calibers for bore and shot weight.

 

The table you made is really useful 😁

 

Thank you. However, this may not be the final version of the caliber scale, because other combinations are indeed possible, for example, using the Rhenish (Cologne) foot instead of the Danish foot. Nevertheless, the very essence of this method of calculating calibers must be correct, and finding the base values for this construction can be indeed useful in practice. Anyway, I am continuing my work on this scale, and now I am translating the entire passage from Blom's work (pages 100-110), because there he quotes specific readings from sources of the era, in particular specific values from actual gunner's rules. 

 

[Waldemar]

 

Now, after reading the relevant passage from Blom's work, it is at least known what he did, what he didn't do, and why. Although I generally consider Blom's work to be reliable, apt, and cognitively valuable (as far as I can judge based on other passages), it is, unfortunately, weaker when it comes to determining calibers and the way of their defining by the contemporaries. First of all, on this particular issue, he essentially rejected the analysis and general conclusions of the Danish general and historian Fibiger that the basis for calculating calibers in Danish artillery of that period was the method invented and defined by Hartmann (see above for the definition of this method). Instead, he engaged in rather esoteric comparisons of the total weights of projectiles taken from contemporary documents, which could not even provide any precise results.

In addition, it turned out that Blom, in a partially arbitrary and, consequently, quite unrealistic way, matched the poundage of shot to the poundage of bore for specific sizes of cannons known from inventories (tables on p. 103 and 192 in Blom's work). This is why, according to Blom, the windage for an 8-pounder cannon is absurdly significantly greater than for a 30- or 26-pounder cannon , which is in obvious contradiction to the commonly known mathematical and geometric methods of determining the mutual relationship between bore and shot diameters, which are (almost) always uniformly proportional (for example, the rule: shot diameter = 20/21 bore diameter, regardless of caliber). 

Fortunately, Blom quoted specific values read from a contemporary gunner's rule (caliber scale), which I also included in the below table for comparison (here, there is perfect coverage across the entire caliber range with the reconstructed caliber table). In addition, Blom also cited a reading of the length of one inch (according to the Danish measure) from the same gunner's rule. The length of this one inch is not entirely consistent with the caliber scale from the same gunner's rule, but the difference from the length of one inch in the reconstructed base foot length is very small (0.13 mm) and can be considered within the measurement tolerance or workmanship tolerance of the gunner's rule itself.

I came to the conclusion that the values read from the contemporary gunner's rule refer to the diameters of the bore of cannon barrels, which are intended for firing cast iron shot of this poundage (for the construction of the previous table, I made the opposite assumption, i.e., that they refer to the diameters of the shot). It can therefore be said that in Denmark it happened in exactly the same way as in Sweden (or vice versa), i.e. around 1600 (in Sweden in 1616) the 24-pound caliber was assigned to the diameter of the bore, while in 1687 (in Sweden in 1684), the same 24-pound poundage was assigned to the diameter of the shot.

The reconstructed length of the base foot for calculating the caliber scale is 288.4 mm, which is one millimeter more than the length of the Cologne foot (287.396 mm, according to a value given in a mid-19th century work, or more precisely from 1838).

I have adopted a number of 21 as the base poundage for calculating the diameters of the shot. This number yields realistic windage values and, at the same time, is also consistent, as far as possible, with the data given by Blom in his work. The difference (i.e., three pounds for the base poundage of 24) is the same value known to be adopted in Swedish artillery in the 1684 reform. If someone prefers a smaller windage, they should change the base value of 21 to a larger number, for example 21.5 or 22, and vice versa.

As it stands now, here are a few examples for typical calibres:

 

A 48-pounder cannon fires shot of nominal poundage of 42

A 36-pounder cannon fires shot of nominal poundage of 31.5

A 30-pounder cannon fires shot of nominal poundage of 26.25

A 26-pounder cannon fires shot of nominal poundage of 22.75

A 24-pounder cannon fires shot of nominal poundage of 21
A 20-pounder cannon fires shot of nominal poundage of 17.5
A 16-pounder cannon fires shot of nominal poundage of 14
A 12-pounder cannon fires shot of nominal poundage of 10.5

An 8-pounder cannon fires shot of nominal poundage of 7
A 6-pounder cannon fires shot of nominal poundage of 5.25
A 4-pounder cannon fires shot of nominal poundage of 3.5

It is also graphically shown in the diagram below.

Just in case, so as not to leave this reconstruction anonymous, I sign it with my name: Waldemar Gurgul.

 

 

 

 

Edited 5 hours ago by Waldemar

[Lieste]

Windage ratios are not universally geometric progressions as used by the British with Bogard/Armstrong/Armstrong-Frederick. The French Manson pattern (extended by the 1820 30 livres) had quantised windage for 36/30/24/18/12/8/6/4 livre guns as 30/27/27/24/21/21/18/18 pts with 1 livre seeming to be defined a little higher. (these windages for the boulet, appear to be for the middle of the forges gauge (+/-3 pts) with the places gauge between (+3/-6) pts (same high/smaller low gauge).

This is a windage proportion a little tighter than the 20/21 definition for the AF low gauge (with 1/3rd allowed for the high gauge within this interval) (roughly 24.5/25.5 mean) for the larger calibres, but significantly looser than the British stated standard for the smaller natures.

It would be unusual for 'same service' windage allowances to substantially increase for smaller calibres, but I would note that the French land service pattern for shot is a tighter windage definition than the corrosion tolerant naval allowances - the same shot manufacturing techniques (and perhaps (aside from 16livre/18livre calibre differences) the same moulds) but are gauged according to use with a differing degree of hammer finishing and the same 6pt tolerance between gauges with different gauges for the two services. 

It would be possible to see a larger shot defined for the land service guns than in naval stores - and by inappropriate data combination see an anomalously tight windage for 'say' the 12livre gun (Land patterns are given to the high gauge, apparently, with 15pts allowance - equivalent to the naval 18pts - for 12, 8, 6, 4, 3 livre gun patterns. - the 16 livre and 24 livre patterns of siege/garrison artillery have looser gauges)