Bertha Gross
Bertha Gross is the French name of a very large part of terrestrial used by the army at the time of .
It is by error that one often gives this name to the gun which bombarded Paris (cf will infra).
Synopsis |
History
In , the German staff charged the arms factory of Friedrich Alfred Krupp, located at Essen, to work out a part of able to bore three of armed and to break the turrets in with of the fortifications .
One entrusted the design of with professor Rausenberger and them with the Becker captain. After having tested a large variety of, the best compromise enters the performances and the capacities of penetration was obtained with a shell of 1150 kg in charge of 144 kg with. However, the gun corresponding - called Gamma-Gerät (apparatus Gamma, still called "not G") - could be transported only by , what limited its mobility and increased its vulnerability.
From Gamma-Gerät, one was thus developed lighter (of 70 tons all the same!) and more mobile, the M 42. In accordance with the tradition of the Krupp factories, which wanted that the machines were baptized name of a member of the family, the M 42 was famous Dicke Bertha (Bertha Gross), in the honor of Bertha Krupp, the girl heiress, and of her size (of the gauge of the howitzer, not of Bertha Krupp). The artillerists called it Fleissige Bertha (assiduous Bertha).
Use
The Bertha Gross entered in service it at the time of the seat of . , thirteen forts girdling the Belgian city (of which it Extremely of Loncin) had been destroyed. Bertha devastated the fortresses of, , , , Ypres as well as Russian defenses of . If the damage caused at the forts, considered indestructibles, impressed the allies, the celebrity of the Bertha Gross came from confusion with the long guns which bombarded in and that the Germans called Ferngeschütz or Pariser Kanonen : Rausenberger had adapted tubes large gauge intended for cruiser Freya Substitute, whose construction had been suspended. In the same way, the Maginot Line was bombarded by a Czech howitzer of origin, manufactured by the Skoda factories.
At the end of the war, the Bertha Grosses were destroyed not to fall between the enemy hands. Only the affected gun with the field of fire of Meppen survived, slightly was altered then gone up. Renamed Gilda Gross (Large Gilda), it was used in December , at the time of the seat of and, two years later, at the time of the insurrection of . It also bombarded , without much result. Because of his age, one could not draw more than fifteen blows with Large Gilda. Germany preferred to develop the missile-rockets, of which the famous ones and V2.
According to testimonys' of time, neither the Bertha Gross, nor Large Gilda were guns.
Characteristics
- Name: M 42
- Nickname: Dicke Bertha (Bertha Gross), Fleissige Bertha (Assiduous Bertha)
- Type: heavy mortar
- Gauge: 420 mm
- Range of shooting: 12,5 km
- Total mass: 70 tons
- Mass shell: 800 kg
- Initial speed of the projectile: 400 m/s
The gun which bombarded Paris (Ferngeschütz)
Although having existed, this gun was not a Bertha Gross.
, starting from 7h15, the Parisian ones were astonished enough (of course!) to hear several explosions with fifteen minutes of interval and not to see any plane in the sky. The effects were especially psychological. Not obtaining the anticipated result, the Germans judged that it was preferable to get rid of this cumbersome weapon. It was returned to Germany and was remelted.
This gun had the following characteristics:
- Length of the tube: 34 m (a device of stay prevented bending)
- Gauge: between 210 and 240 mm (the tube was worn after 65 blows)
- Maximum range: 108 km (130 km according to certain sources)
- Mass shell: 103 kg
- Mass of powder necessary (1): 145 kg
- Initial speed of the projectile with maximum loading: 1600 m/s
- Apogee (1) : 38,6 km
- Time of flight of the projectile (1) : 176 S
Deviation of Coriolis shooting
A simple calculation makes it possible to estimate the deviation of a ballistic trajectory due to the rotation of the Earth. Since the analysis that had made the artillery captain of it Coriolis (1792-1843), it is known that the projectile deviates on the right in the Northern hemisphere and on the left in the Southern hemisphere, so that it is possible to highlight in experiments the diurnal swivelling of the Earth. This theorem encouraged Foucault (1819-1868) to carry out its famous pendulum.
The order of magnitude can be obtained while placing the piece of artillery, not in Meaux, but with the North Pole, and while drawing in the direction from the meridian line from Greenwich. By considering G = 10 N/kg and V° = 1600 m/s, one calculate a maximum range "in the vacuum", IE. in absence of frictions, - L° = 2 H° - of 256 km, theoretical range much higher than reality, and a duration - t° = 160.(2)½ - of 226 S, to compare with the real duration of 176 S.
By applying the formula of Coriolis, one finds easily:
D(t) = -2/3.<maths>\Omega</maths>t/\1/2.G.t² -<maths>\Omega</maths>t/\V°.T
By breaking up V° into his components vertical V1 and horizontal V2, one can simplify the expression:
D(t°) = -<maths>\Omega</maths>t°/\V2.t° = -<maths>\Omega</maths>t°/\L°:
This result, completely intuitive, is the arc time the ray, where the arc that is described by the Earth in its diurnal swivelling, during the duration of the shooting (it is considered that the Earth is punt with the Pole on 256 km of ray): 2<maths>\pi</maths>.L°.t°/T with T = 86164 S.
The numerical application gives 4,2 km (1608.226/86164), correction which the artillerist should apply. In fact, these calculations are not right because of action of the air on a whirling shell, which justifies the distress of the commander of battery!
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(1) Maximum range
