The Grosse Bertha is the French name for a very large piece of land artillery used by the German army during the First World War.
It is by mistake that this name is often given to the cannon that bombarded Paris (see below).
History
In 1908, the German General Staff commissioned the armaments factory of Alfried Krupp von Bohlen und Halbach, located in Essen, to develop an artillery piece capable of piercing three meters of reinforced concrete and breaking the turrets in nickel steel from the French fortifications.
The design of the weapon was entrusted to Professor Rausenberger and the calculations to Captain Becker. After testing a wide variety of shells, the best compromise between ballistic performance and penetration capabilities was obtained with a 1150 kg shell loaded with 144 kg of explosives. However, the corresponding gun - called Gamma-Gerät (Gamma device) - could only be transported by rail, which limited its mobility and increased its vulnerability.
From the Gamma-Gerät, a lighter (70 tons all the same!) and more mobile howitzer was therefore developed, the M 42. In accordance with the tradition of the Krupp factories, which wanted the machines to be baptized with the name of a member of the family, the M 42 was renamed Dicke Bertha (Big Bertha), in honor of Bertha Krupp, the daughter heiress, and its size (howitzer caliber, not Bertha Krupp). The gunners nicknamed him Fleissige Bertha (hardworking Bertha).
Use
The Grosse Bertha entered service on August 12, 1914 during the siege of Liège. On August 15, the thirteen forts surrounding the Belgian city (including Fort de Loncin) had been destroyed. The Berthas devastated the fortresses of Antwerp, Maubeuge, Namur, Ypres as well as the Russian defenses of the Danube. However, in front of Verdun and Manonviller the Berthas showed their limits. These forts, modernized with a thick layer of concrete resisted the impacts. If the damage caused to the forts impressed the allies, the fame of the Big Bertha came from the confusion with the long guns which bombarded Paris in 1918 and which the Germans called Ferngeschütz or Pariser Kanonen:Rausenberger had adapted large caliber tubes intended for the cruiser Ersatz Freya, the construction of which had been suspended.
At the end of the war, the Big Berthas were destroyed so as not to fall into enemy hands. Only the gun assigned to the Meppen firing range survived, was slightly reworked and then reassembled.
Renamed Große Gilda (Great Gilda), it returned to service in World War II. It was used in May 1940 against the Maginot line, the Schoenenbourg structure, without much result. It was used again in 1942, during the siege of Sevastopol and, two years later, during the Warsaw uprising. However at that time, Germany had developed other more powerful guns, the Karl and Gustav.
Features
* Name:M 42
* Nickname:Dicke Bertha (Big Bertha), Fleissige Bertha (Assidue Bertha)
* Type:heavy mortar
* Caliber:420 mm
* Firing range:12.5 km
* Total mass:70 tons
* Mass of the shell:800 kg
* Initial speed of the projectile:400 m/s
The cannon that bombarded Paris (Ferngeschütz)
Contrary to rumor, this gun was not a Big Bertha.
On March 23, 1918, from 7:15 a.m., the Parisians were quite surprised (of course!) to hear several explosions a quarter of an hour apart and to see no plane in the sky. The effects were mostly psychological. At the end of the war, not wanting it to fall into the hands of the allies, the Germans decided that it was better to get rid of this cumbersome weapon. It was sent back to Germany and recast.
This gun had the following characteristics:
* Length of the tube:34 m (a forestay device prevented sagging)
* Caliber:between 210 and 240 mm (the tube was worn after 65 shots)
* Maximum range:108 km (130 km according to some sources)
* Mass of the shell:103 kg
* Mass of powder required (1) :145 kg
* Initial speed of the projectile at maximum load:1600 m/s
* Apogee (1):38.6 km
* Projectile flight time (1):176 s
Coriolis deflection of shot
A simple calculation makes it possible to estimate the deviation of a ballistic trajectory due to the rotation of the Earth. Since the work carried out by the physicist Coriolis (1792-1843) on the subject, we know that the projectile deviates to the right in the northern hemisphere and to the left in the southern hemisphere, so that it is possible to highlight experimentally the diurnal rotation of the Earth. This theorem encouraged Foucault (1819-1868) to make his famous pendulum.
The order of magnitude can be obtained by placing the artillery piece, not at Meaux, but at the North Pole, and firing in the direction of the meridian of Greenwich. By considering g =10 N/kg and V° =1600 m/s, we calculate a maximum range "in a vacuum", i.e. in the absence of friction, - L° =2 H° - of 256 km, a much greater theoretical range to reality, and a duration - t° =160.(2)½ - of 226 s, to be compared with the actual duration of 176 s.
By applying the Coriolis formula, we easily find:
D(t) =-2/3.Ωt/\1/2.g.t² -Ωt/\V°.t
By breaking down V° into its vertical V1 and horizontal V2 components, we can simplify the expression:
D(t°) =-Ωt°/\V2.t° =-Ωt°/\L°:
This result, quite intuitive, is the arc times the radius, where the arc is that described by the Earth in its diurnal pivoting, during the duration of the shot (we consider that the Earth is flat at the Pole over 256 km of radius):2π.L°.t°/T with T =86164 s.
The numerical application gives 4.2 km (1608.226/86164), which the gunner should apply. In fact, these calculations are not correct because of the action of the air on a spinning shell, which justifies the confusion of the battery commander!