12"/50 Gun

Chapter XII

a. Introduction

The first 12"/50 guns used by the U.S. Navy were installed on the battleships ARKANSAS and WYOMING in 1912. The design of the gun barrel, designated Mark 7, which was completed 1907, fired an 870-pound projectile at 2900 f/s. Six 12"/50 two gun turrets comprised the main battery of the ARKANSAS and WYOMING, which saw service in the Fleet in both World Wars. However, the Navy at no time exhibited a great deal of interest in the use of an intermediate caliber gun and no new developments were undertaken in the 12" gun until 1940. At this time the 12"/50 three gun turrets were designed for ships of the ALASKA CB1 class.

b. History of 12"/50 Three Gun Turret

The design of the 12"/50 three gun turret was undertaken at the instigation of President Roosevelt when he requested the Bureau of Ordnance to investigate the size of gun capable of combating German cruisers of the Deutchland class. The Bureau made a number of preliminary studies of 10-, 11-, and 12-inch, one gun, two gun and three gun turrets before a final decision was reached to develop


a new 12" gun. The original design called for four turrets--- two 2-gun and two 3-gun 12"/50 turrets. The design was carried out to the preliminary procurement stage when the decision was reversed. It was decided to put three 3-gun turrets instead of two 3-gun and two 2-gun turrets on ships of this class. The main reason for this change was to have all the turrets alike in order to simplify the manufacture and procurement of associated equipment.

The ALASKA was the first battle cruiser built since the first World War. The main difference between this type of ship and a battleship lay in the thickness of armor. For this reason the battle cruiser was lighter and therefore had greater speed. At the beginning of the program in 1940, plans called for the building of six cruisers of this type, with the USS ALASKA as prototype. The number was later reduced to three. Actually only the ALASKA and GUAM were finished in time to enter active duty with the fleet. The HAWAII was under construction when hostilities ceased but was scheduled to be finished and placed in the inactive fleet.


One novel feature of the 12"/50 three gun turret was the design of the lower powder hoist which was similar to those employed en cruisers of the BALTIMORE class. In order to increase the rate of fire and insure a greater degree of safety, the powder hoisting stage was broken and an intermediate loading level added. Service between the lower powder handling room and the gun compartments was arranged in two stages of lift. Separate hoists for each gun had separate car-type electro-hydraulic hoists independently controlled but arranged with interlocking controls. This arrangement prevented simultaneous opening of upper and lower hoist doors of either hoist or the two doors in each of the three powder transfer rooms on the machinery flat. The use of the intermediate powder handling level resulted in saving approximately five to six seconds in the firing cycle. The lower hoists used an hydraulic cylinder with an arrangement of multiple block, and fell to the ratio of one to six between the stroke of the cylinder and the motion of the powder car. The upper hoist design, a new type for turret ordnance, employed an hydraulic cylinder with


piston attached to the car, a one-pipe system arrangement between pump and cylinder which raised the car by displacing the piston from the cylinder end lowered by displacing the fluid.

The projectile hoists, were similar to the 16" hoists of ships of the BB61 IOWA class. Projectiles were stowed on two handling levels in each turret. Each turret was provided with a rotating projectile ring which was indexed by an electric hydraulic drive equipment which automatically positioned the projectile at the base of the three projectile hoists. The number two turret had additional projectile stowage on a larger projectile ring at the base of this turret. Projectiles were hoisted to the lower projectile handling level. The rammers were of the conventional block, chain type and were driven by electric hydraulic drive equipments similar to those of the BB55 CAROLINA class.

The pointing and training mechanisms of the 12"/50 turret were similar in design to those of the CA68 BALTIMORE class. There was one pointer to each gun and



two trainer stations per turret, one of which was an auxiliary standby. No manual operation was provided for train or elevation as for hoisting ammunition. In the preliminary design of the hoist, it was decided to use mechanical and hydraulic interlocks but a later decision substituted electric hydraulic interlocks. The main reason for the change was due to the fact that the original design of the lower powder hoist for cruisers of the BALTIMORE class called for electric hydraulic interlocks. This design was changed to mechanical interlock but when the equipment reached the service it was found to possess numerous faults which could not be overcome. Design of the powder hoist-controls and interlocks for ships of the ALASKA class were therefore changed to hydraulic and electric.

Another unique feature of the 12"/50 turret was the provision for a projectile room for transferring projectiles from stowage to the rotating projectile ring. However, this feature was not entirely satisfactory and there was considerable discussion about removal of the transfer ram. The projectile transfer rams were not installed in CB3, the



HAWAII, and were removed from the upper projectile handling flats of the ALASKA and GUAM. The objection to the transfer ram did not stem from any fault in the equipment itself but from the fact that forces at sea were fearful that the turret would be started in motion while the transfer was occurring, thus causing a Jam. For this reason, many officers at sea felt that the projectile ram could be dispensed with, and the turret thus be lightened. It was decided to remove the projectile ram because the original elevation speed gears proved incapable of proper function under the loads imposed on them when in automatic control. They were to De replaced by new, stronger, larger, and heavier hydraulic systems. In order to compensate for the extra weight, the upper projectile transfer rams were removed.

The turret was trained by two pinnions, acting on a conventional type train rack, and driven by two Waterbury size 50 "B" ends which were controlled by one Waterbury size 75 "A" end and Ford Instrument Company automatic control equipments.



Considerable difficulty was experienced with the gun port seal. The Navy tried the British type, but after much experimentation this was found to be unsatisfactory. The Bureau of Ordnance, in conjunction with the Philadelphia Navy Yard, then developed a new type of seal which overcame the leakage of water experienced with the older type of seal. This proved entirely satisfactory and was adopted for 5", 6", 8" and other types of gun turrets

Extreme difficulty was encountered during the early use of the elevating gear drive equipment, which was manufactured by the Waterbury Tool Company, a subcontractor of the Ford Instrument Company. The major trouble occurred about three weeks after the first ship of the program had been commissioned. The elevation hydraulic "A" and "B" end units were not sufficiently strong to do the job. The Ford Instrument Company was held to its contract guarantee and was required to deliver new, stronger "A" and "B" end units to replace the original units. One of the reasons for the failure of the elevating gear drive equipment was the attempt to use hydraulic equipment which was in production rather than design new



equipment. Northern Ordnance Incorporated control valves and solenoids were used for controlling some of the Waterbury Tool Company's hydraulic power and projectile hoist equipment. When this material reached the shipbuilder, a great deal of confusion ensued and some wrong hand valves were Installed on the first ship. This matter was finally straightened out with the assistance of the Bureau of Ordnance.

The 12"/50 gun barrel was developed from the previous Mark 7 and designated Mark 8. It weighed 54 tons, a reduction of eight tons from the Mark 7, had a service pressure of 18 tons and fired 1140-pound projectiles with a charge of 268 pounds and an initial velocity of 2500 f/s.

Unusual difficulties were encountered in installing this turret in the ship. In addition to the faulty elevating gear mentioned above, numerous design changes were necessary to make it operate satisfactory. To accomplish this result, approximately three months of constant modifications to some of the equipment was required. The turret had been designed and manufactured so rapidly that In order to meet the shipbuilder's re-



requirements, it could not be properly tested by the Naval Gun Factory or the Proving Ground. This turret was an outstanding example of a case where prior testing of a new design by the manufacture of a pilot model was required.



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Transcribed and formatted by Thomas Wildenberg, HyperWar Foundation