Technical sheet of Agostino Incisa della Rocchetta
The battleships Littorio in 1940 and Vittorio Veneto in 1942
by Agostino Incisa della Rocchetta
In 1934, the major powers each resumed full freedom of action in armaments and the General Staff of our Navy judged that only 2 battleships of 35,000 tons, albeit with the modernization of 4 units already in armament in the First World War, were not sufficient to to deal with any united French and British forces in the Mediterranean; he therefore considered it necessary to build another 2 battleships of 35,000 tons. They had only minor changes compared to the previous ones. One, the Rome, was assigned under construction to the Cantieri Riuniti dell'Adriatico, the other, the Empire, to Ansaldo of Genoa; they were set up in 1938. Vittorio Veneto and Littorio entered service in 1940, shortly before the start of hostilities, Rome in 1942 and the Empire, when the armistice occurred, was never completed.
The most noticeable difference between the last 2 and the previous ones was the line of the prow: Rome and the Empire had a more elevated castle, that is, a more pronounced pony.
The stern was of the cruiser type, slightly more rounded in Rome and in the Empire. The 4 ships of the "Littorio" class had all the other characteristics in common: the arrangement of 3 rudders was remarkable: one main axial and 2 auxiliary, secondary, between the internal and external axes of the propellers, which were 4.
The relationship between the volume of the hull and the overall volume of the superstructures was very harmonious and gave these ships an aggressive aspect. The tower took up the tried and tested scheme of the second series of the "Condottieri" (Muzio Attendere, Eugenio di Savoia, Montecuccoli).
In the center of the ship, 2 large smokestacks close together. The forward one had as an offshoot the platform for the direction of firing of the machine guns. The tallest forward mast was joined to the tower by 4 walkways, one of which served as a signal station. The lower aft mast rose from a structure aft of the funnels which housed the aft command post and projectors. At the extreme stern there was an adjustable catapult, for the launch of 3 planes that were originally RO 43s with stellar engines, reconnaissance biplanes, "boot" seaplanes, that is, equipped with a large central float and 2 smaller ones under the wings. and higher than the central one. At take-off and ditching, the plane kept its balance on the central one, while, when stationary, in the water, it remained slightly heeled, resting on one of the lateral floats. Later 2 of the RO 43s were replaced by King 2,000 fighters.
The resistance of the armor was tested in May 1935 at the Cottrau balipedio in La Spezia. It proved to be capable of withstanding the impact of 406 mm armor-piercing shells fired from a distance of 24,000 m and that of 1,280 kg aircraft bombs, of not excessive armor-piercing capacity but of great explosive power, as well as capable of resisting bombs. armor-piercing of 835 kg, both types of bombs with an impact speed of 250 m / sec, ie the maximum natural rate of fall (there were no rocket propellant bombs at the time). The vertical protection in the central part of the ship, i.e. from the ammunition depot of tower no. 1 gc, at the tower depot n. 3 gc was secured by a 350 mm thick plate, not vertical, but converging downwards with the median plane of the hull, so as to reduce the impact angle of the projectiles, which was equivalent to a greater thickness of armor. The armored belt was reduced to 60 mm in the forward area and 100 mm in the aft area. A short distance from the armored belt was a 36 mm splinter bulkhead; another, also splinterguard, of 24 mm inclined in the opposite direction to the armored belt, placed more internally, also served as a support for the main armored deck. The armored redoubt was completed by 2 armored transoms 210 mm thick in the bow and 290 mm in the stern. The crossbeams were respectively forward of the ammunition depot gc of tower n. 1 and aft of the gc depot of tower no. 3.
Longitudinal section and cross sections of the units of the «Vittorio Veneto» class.
Horizontal protection was ensured by 3 armored bridges: the lower one, called the battery[1], had a maximum thickness of 100 mm, the median, called deck, had one of 12 mm and the highest, the castle, one of 36 mm. However, the thickness of the armor of the battery deck reached 150 mm at the ammunition depots while it thinned up to 90 mm at the bulwarks. Outside the armored redoubt, the battery deck had armor of 70 mm towards the bow and 36 mm towards the stern. The wheelhouse, which was outside the forecourt, had a second armored deck 100 mm thick below the main deck.[2].
The 381 mm towers had plates of maximum thickness of 350 mm, the 152 mm ones were protected by armor of 150 mm. The keep was protected by armor of 260. mm, while the "armored tube" inside it, which connected the floating station 15 to the admiral bridge 16 was 200 mm thick. The "armored tube" was used for the passage of men from one floor to the other of the tower and for the passage of cables, which constituted a real spinal cord of the ship, because they transmitted all orders and received all information concerning weapons, engines, security systems, etc.
The horizontal armor, in correspondence with the smoke ducts of the boilers was replaced by grids formed by plates side by side and arranged vertically, so as to provide a certain protection from bombs even in the funnels.
The underwater protection of the Roma and of the other two 35,000-ton battleships similar to those of the «Cavour» and «Doria» class battleships was obtained with an original system due to Gen. del G .N. Apulian. In the "Vittorio Veneto" class ships, already envisaged in the design of the hull, it was a structure formed by a hollow cylinder with a maximum diameter of 3.80 m, placed under the waterline, along the sides of the ship in correspondence with the reduced armored. Appropriate diaphragms connected it to the external and internal hulls, which consisted of an anti-splinter protection with a thickness ranging from 28 to 40 mm. The cylinder was watertight, it contained only air, while the area between the external and internal hull was filled with fresh water (drinkable or for feeding the boilers, or for toilets) or oil. As these liquids were consumed, they were replaced by sea water.
Master section of the «Vittorio Veneto» class with the Pugliese protection system against torpedoes. (Col. Franco Gay)
Genoa, Cantieri di Sestri, 1935. RN Littorio, twin of Roma, under construction
(photo Ansaldo Genoa Foundation)
For effective protection against torpedoes it was essential that the spaces around the cylinder were always filled with liquid while the inside of the cylinder had to be always empty. The pressure exerted by the explosion of a torpedo was transmitted in every direction by the liquid, which then exerted it on the entire surface of the cylinder, until it broke. In fact, the walls of the tube, less resistant than all the surrounding structures, by breaking through, absorbed most of the burst energy, protecting the vertical bulkhead of the inner hull. The Rome did not suffer from torpedo damage during its short life but both the Vittorio Veneto and the Littorio were torpedoed several times and when the impact of the torpedo occurred in the area corresponding to the armored redoubt, the Pugliese structure worked very well.
The artillery of the 35,000-ton battleships
381/50 guns
The 381/50 guns had the following characteristics:
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weight of the project 822 kg
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initial speed of the project maximum elevation
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maximum depression maximum throw 870 m / sec
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maximum elevation 35 °[3]
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maximum depression 5 °
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maximum range 42,800 m
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firing rate 1 shot every 45 sec.
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shells supplied: 75 shells per gun and 480 charge elements per piece
Cannons from 152/55
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weight of the project 50 kg
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initial speed of the project925 m / sec
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maximum elevation 45 °
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maximum depression 5 °
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maximum range 24,900 m
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firing rate 1 shot every 13 sec.
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shells supplied 210 shots per cannon
90/50 cannons
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weight of the project 10 kg
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initial speed of the project 845 m / sec
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maximum elevation 75 °
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maximum depression 3 °
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maximum range 13,000 m
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firing rate 12 rounds per min.
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5,500 explosive and 240 illuminating grenades
Arranged at the far bow were 4 37/54 machine gunners in single retractable systems. They, of course, could not fire when firing towers No. 1 and n. 2 from 381/50. The other 37/54 in coupled systems were distributed as follows: 2 systems on the top of tower n. 2 and 2 on the sky of tower n. 3 large caliber, the other 16 on the deckhouse to starboard and to the left of the funnel. The 28 20/65 guns were distributed, in twin systems, next to towers n. 2 and n. 3 gc and the others on the castle and on the deckhouse.
37/54 machine gunner
20/65 gunner
The 4 120/40 for the illuminating fire were placed on the side amidships
A very sophisticated system had been applied to stabilize the aim, that is to cancel the variations in elevation and swing 17 of the pieces due to the oscillations of the ship (roll and pitch). In this area our modern battleships were certainly at the forefront, as perhaps only one or two of the strongest Marines in the world possessed anything similar.
The system adopted on our 35,000-ton battleships was, briefly, the following: a gyroscopic power plant determined the variations in the attitude of the ship both in speed and in acceleration (i.e. oscillations in roll and pitch as well as rotation under lock) through special electric machines called "metaconformers" and "metadynamo" the gyroscopic system [4]it commanded the movement of electric motors that acted on the elevation of the pieces and on the traverse of the 381 and 152 towers, so that the lines of sight were not altered by the movements of the ship (stabilization of the lines of sight). Also the lines of sight of the general aiming apparatus (called APG) of the 381, which was located at the top of the tower, the lines of sight of the aiming devices and of the direction stations of the night shooting of the 152 and of the 90, and even those of the sighting columns of the machine guns were stabilized.
But there was more: the turrets of the direction of the day shot of the 152 and those of the direction of the shot of the 90 were completely stabilized, that is to say they kept themselves automatically with the horizontal floor despite the oscillations of the ship. The men inside it did not perceive any pitch or roll; in addition, the turrets kept constantly in the direction of the target with the swing, when the ship was under close. Not enough: even the platforms of the 90 systems were stabilized, which therefore had movements identical to those of the DT turret. The servants of the pieces, in other words, rested their feet on a plane that was always perfectly horizontal. The anti-pitching, anti-roll and anti-approach movements were carried out by electric motors that moved worm screws placed orthogonally under the DT turrets and under the platforms of the 90 systems.
Even the anti-aircraft lookout stations were completely stabilized. They were like large eggs with a large window protected by a crystal. The lookout men took their places in it from a rear opening; they had powerful binoculars with which they had to explore a certain sector of the sky. On Rome, there were 12 lookout stations, 6 on each side, immediately below the 90-degree DT turrets and each had to monitor a 30 ° spherical segment of opening. The sighting was communicated by means of an acoustic signal and an index on a dial, both to the dashboard and to the DT turret of the homologous side.
The engine system
The 8 boilers, Yarrow type, with oil, with superheaters, were placed in the center of the ship in separate rooms. They powered 4 engines: 2 under the tower, which operated the 2 external propellers; 2 under the stern shaft, which moved the 2 internal propellers. The operating pressure of the steam produced by the boilers was 25 kg / cm2. Each engine was composed of a high pressure turbine, a medium and a low pressure turbine and was equipped with a speed reducer.
Water heater
The supply of naphtha for the engines and auxiliary machinery was about 3,700 t at normal load and about 4,000 / 4,500 at full load (they differed slightly from one to the other of the 3 ships).
The reserve water supply for the boilers was 375 t. The power developed was approximately 135,000-140,000 hp overall.
[1]Armored room, placed under the tower, from which, during combat or an air attack, the ship's commander in 2 "gave instructions for the intervention of the fire fighting teams, for the balancing of the ship, by flooding special compartments on the side opposite to the one in which a leak had occurred, from which the sea water invading some rooms, had produced a heeling.
[2]Bridge from which the admiral, commander of the division or squad, gave orders to units dependent on him. Rome had become flagship of the Naval Forces on 8 September 1943. The admiral bridge was located on the tower, immediately above the ship's command bridge. Both consisted of a circular shelf outside the tower. At the front this shelf was covered and equipped with a series of 7 rectangular windows, at the back and laterally it had a simple leg protector; sideways 2 short flaps. The 2 90 mm anti-aircraft fire direction turrets were on the starboard and left side of the dashboard and very close to it, so much so that, by climbing over the leg protector, it was possible to easily pass over the sky of the turrets themselves.
[3]Elevation: angle that the cannon axis makes with a plane parallel to the ship's deck; tilt: rotation on that same plane (if the ship is in calm water the tilt is on a horizontal plane
[4]The gyroscope is a heavy disk (flywheel) whose axis is keyed on a gimbal suspension and, therefore, it can orient itself in any direction as well as being able to rotate on itself. if you give the gyroscope a rapid rotation motion, it tends to keep its axis always oriented, in space, in the direction in which it was when it started to rotate. Using this principle, the small toy gyroscopes keep themselves balanced on a taut wire. The most modern compasses are no longer with magnetic needles but gyroscopic. They have the wind rose oriented north by a gyroscopic system. Similarly, the stabilization system of the lines of sight and platforms applied on our battleships was based on a gyroscopic system