US NAVY PAGES
NAVAL ORDNANCE AND GUNNERY
VOLUME 1, NAVAL ORDNANCE
Chapter 7 Turret Installations
B. Gun and breech assembly
C. Slide assembly
D. Elevating, traning and sight gear
E. Ammunition handling
F. Turrets equiped with case guns
G. 6"/47 dual-purpose gun and turret
H. 8"/55 rapid-fire gun and turret
| B. Gun and Breech Assembly
7B1. The gun
The 16”/50 caliber gun is a built-up gun consisting of a liner, a tube, a jacket, three hoops, and a yoke ring. It has an overall length of 68 feet, and a maximum outside diameter of 46 inches at the slide cylinder. The total weight is approximately 120 tons. The rifling has a uniform twist of 1 turn in 25 calibers. The bore is chromium plated to retard erosion. The powder chamber is slightly less than 18.5 inches in diameter and about 9 feet long.
|The screw-box liner is screwed into the breech, and its inner surface provides the stepped threads which engage those on the Welin-type plug. Ducts between the gun and the liner, and holes through the latter, provide the air leads of the gas-ejector system.
The yoke is mounted around the breech end of the gun to provide the means for securing the recoil piston rod and the two counterrecoil cylinder yoke rods to the gun. See figures 7C1 and 7C2. The yoke also helps to counterbalance the gun. The yoke is secured to the gun by a key, a fixed ring, and a locking ring. A shoulder on the yoke butts against the rear face or breech end of the fixed ring secured to the gun in an annular groove. The locking ring screws into the yoke and holds it in place against the fixed ring. The key prevents rotation about the gun axis.
7B2. Breech mechanism
The breech mechanism is shown in figures 7B1 and 7B2. Its principal parts include: (1) a Welin-type plug, (2) a mushroom and gas-check pad, (3) a carrier, (4) counterbalance springs and closing cylinder, (5) rotating cams, (6) an operating lever and connecting rod, and (7) a salvo latch.
Welin plug and gas seal. The plug rotates 29° to lock to the screw-box liner. The design of the blank sectors permits the two plug-rotating cams to rotate the plug slightly over 6 degrees before the threads engage while the breech is closing. The cam action assists in obtaining a smooth transition between plug translation and rotation.
|The mushroom and gas-check pad are the conventional De Bange type described in article 5B4. An indication of the mushroom size is that its weight is over 220 pounds.
The plug is mounted on the carrier as shown in figure 7B3. The threads on the carrier journal and in the plug recess have a pitch of 0.9 inch. This means that the plug will move aft 0.9 inch per counterclockwise revolution. Since the plug is unlocked by a rotation of 29 degrees, it is evident that it will move aft on the carrier journal about 0.1 inch when the breech is opened. If the gas-check pad is stuck to the seating surface, the plug will pull away from the back of the pad and the compressed spring around the mushroom stem will tend to force the mushroom nut, and hence the pad, aft. This force ordinarily breaks the seal; but if it does not, the continued rearward movement of the plug separates the pad from its seat.
Carrier and associated equipment. The plug and carrier, which have a combined weight about 2,000 pounds, swing about a pivot supported by the hinge lug secured to the gun. The plug is locked in the open position by a holding-down latch until it released by a foot crank near the loading platform.
The opening buffer functions to bring the downward movement of the carrier to a stop without shock. In construction and operation it is similar to a grooved-wall type of recoil brake. The counterbalance and closing cylinders are a combination of spring and pneumatic mechanisms which function to balance and check the weight of the breech assembly in opening and to furnish assistance in closing the breech. The cylinders receive their air supply from the gas-ejector system alter the pressure has been reduced from 200 to about 40 psi. The counter-balance springs are so adjusted that the breech mechanism will swing down and latch without a jarring stop or rebound. The air pressure in the cylinders is set so that, when the air valve is opened by the gun captain, the breech will close and swing the operating lever nearly home. The swing of the lever is always completed by hand.
Operating lever and salvo latch. The operating lever is pivoted on the carrier and is connected to the plug by means of the connecting rod which extends from a pivot on the lever to a pin on the breech-plug rear face. Motion of the operating lever about its fulcrum as it is pulled aft causes the connecting rod to rotate the plug and unlock it from the screw-box liner. A beveled, spring-loaded plunger in the end of the lever engages the operating-lever latch when the breech is fully closed. (See fig. 7B2.) The swing of the operating lever is stopped by the operating-lever buffer, which is similar to the opening buffer.
|The salvo latch is an automatic latching device of the positive action type. It functions to prevent lifting of the operating-lever latch when the breech is closed until after the gun has fired. It releases the lever latch as the gun recoils, so that it may be lifted subsequently. Figure 7B4 shows the assembled arrangement.
The roller support bracket and roller are mounted on the counterrecoil cylinder. They are the only parts of the salvo latch assembly which do not recoil. As the gun recoils, the salvo-latch lever moves past the roller, and is rotated by it. This turns the shaft and the salvo-latch locking aim. The locking arm is caught and held in its displaced position by a latch catch (not shown in the figure). This action also holds the salvo-latch lever in its displaced position. The locking arm is thus held out of the way of the lug on the latch sleeve. The operating-lever latch, being integral with the latch sleeve, can now be raised against spring pressure to release the breech-operating lever.
After the gun has returned to battery, the plugman opens the breech. His action of raising the operating lever latch rotates the sleeve and depresses the latch catch, so that the locking arm springs back to its locking position. Then, when the breech is closed, the operating lever slides under the operating-lever latch, where it is caught and held.
For drills the salvo latch is secured in its unlocked position, so that the habit of manually unlocking the salvo latch will not be formed. This is accomplished by screwing the latch locking pin in hole B. The pin holds the salvo-latch locking arm in its displaced position. At all other times, it must be kept in the turret officer’s booth.
|7B3. Firing mechanism
The firing mechanism consists of a Mark 14 Mod 5 firing lock and the associated operating devices which synchronize its action with that of the operating lever. The firing lock, shown in figure 7B5, consists of a receiver which is attached to the end of the mushroom stem and a wedge which slides back and forth in the receiver, to open and close the primer chamber in the mushroom stem. The primer-retaining catch helps to hold the primer in place until tire wedge closes; the extractor ejects the primer case as the wedge opens. The wedge contains an insulated firing pin which carries the current to the primer bridge for electrical firing. For percussion firing, a hammer, a contact piece, and a cocking lever attached to the wedge function to deliver a blow to the firing pin. This is accomplished by drawing back the cocking lever, which pulls the hammer with it until a catch on the lever releases the hammer. As the hammer is drawn back, the hammer spring is compressed. When the hammer is released, this spring drives the hammer forward, making the contact piece strike the firing pin, which transmits the blow to the primer.
Safety features incorporated in the lock prevent firing until the gun breech and the firing lock are completely closed. These include:
1. A lug on the hammer slides in a groove in the receiver and lifts the hammer enough to break electrical contact between the firing pin and primer until the wedge is in the closed position.
2. The same lug also prevents the hammer from being drawn back for percussion firing until the wedge is in the closed position.
3. The hammer thrust pin must line up with a hole in the carrier before the cocking lever can be pulled back for percussion firing. This alignment occurs only when the wedge is fully closed.
4. The cocking lever is so constructed that it transmits any accidental blow directly to the wedge instead of to the hammer and firing pin. The hammer placed between the cocking lever and the wedge is amply protected from exterior blows.
The wedge is connected with the breech-plug operating lever by means of a lock-operating bar (fig. 7B2) and a mechanical linkage. The motion is such that the wedge is withdrawn and the primer extracted when the operating lever is pulled aft and down in opening the breech. To reprime in case of a misfire the wedge can he retracted, without opening the breech, by unlatching the retracting lever latch (fig. 7B2) and rotating the retracting lever. This permits downward movement of the lock operating bar without moving the breech operating lever. But the wedge cannot be fully closed unless the breech is closed and locked.
The wedge is secured to the operating bar by means of a pin. The hole in the wedge through which the pin passes is slotted to permit movement of the mushroom stem during fire. The firing lock can be removed by taking out the pin and turning the receiver 90 degrees to unfasten it from the mushroom stem.
7B4. Gas-ejector system
The system includes a series of storage tanks, piping with the necessary swivel and expansion joints, the gas-ejector valve (fig. 7B2), the gas-ejector trip plate, passages through the screw-box liner, and nozzles which direct the air into the bore. Air at 150 to 200 psi from the ship’s compressors is brought into the turret through the central column for the main gas ejectors, the auxiliary gas ejectors, and the pneumatic breech-closing cylinders.
From the tank the air is piped to the slide and thence through an expansion joint to the breech. The gas-ejector valve controls the flow of air in the ejector system. It is automatically opened by the gas ejector trip plate when the plug is turned for opening the breech, and is closed manually when the bore is clear. When the valve is opened. air is admitted to an annular space between the screw-box liner and the gun. Three equally spaced holes extend through the liner from this space, and nozzles are recessed into their ends. The air jets direct their streams forward toward the bore center.
An auxiliary ejector consisting of a hose with a quick-acting valve and nozzle is stowed overhead near the breech. This is a standby device which can he directed into the gun to clear the bore in case normal gas ejection by the primary means fails.