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58
 

DESCRIPTION


Exterior view showing general arrangement
of the 20 mm. A.A. Gun and Mount Mark 5 Mod. 3.
Figure 20-Exterior view showing general arrangement of the 20 mm. A.A. Gun and Mount Mark 5 Mod. 3.

 

59
 

Chapter 3
MARK 5 MOD. 3 GUN MOUNT

GENERAL DESCRIPTION

This gun mount, see Figure 20, is of the Fixed Trunnion Height Type, that is the trunnion cannot be raised or lowered as is possible with the Mark 2, Mark 4, and Mark 6 type mounts. It is, however, possible to train the gun through an unlimited angle when not locked in position by the carriage lock, see Page 61.

The gun can also be elevated between minus 5 degrees and plus 87 degrees. It can be locked in either the plus 5 degree or 87 degree positions with the trunnion bracket and pivot locking bolt, see Page 61.

DETAILED DESCRIPTION

The main view of Plate 2 folded at page 72, is a vertical cross section view of the mount.

Section A-A is a cross section view of the cradle and the counterbalance spring.

Section B-B is a cross section view of the cartridge bag weight attachment to the cradle.

Section C-C is a cross section view of the trunnion bracket and pivot locking bolt arrangement.

Section D-D is a cross section view of the cartridge bag attached to the cradle.

Section E-E is a cross section view of the carriage locking plunger arrangement.

Figure 21 is an exploded view of the gun mount parts.

PEDESTAL AND PIVOT (STAND MARK 5)

The pedestal and base on this type mount are integral. It consists of a hollow casting bored out in the center, near the top to serve as a bearing for the pivot on which the gun carriage rotates. See Figure 21. The cylinder in which the pivot operates is filled with extra light mineral oil, Navy Symbol 1042, 2110 or 2075 to permit easy training of the gun under all temperature conditions.

A shoulder is provided near the top of the cylinder to support the bearing flange of the pivot. Two two-piece large diameter, babbitt faced steel thrust bearings are used above and below the pivot flange to provide easy movement of the pivot. The bearings are provided with locating lugs which ride in corresponding grooves in the pedestal.

As a relatively close adjustment is required on the thrust bearings, a threaded retainer is used at the top of the pedestal to provide proper clearance. This retainer has sixteen holes through one of which a lock screw is threaded into the pedestal after adjustment has been obtained.

A machined relief is provided between the upper and lower bearings on the pivot. An oil filler hole is drilled in the top of the pivot to provide a means of checking the oil level and adding additional oil if required. A headless pipe plug is screwed into the opening at the top.

NOTE-Ordalt No. 1269 provided for installation of a gun cocking rope hook on the stands of all Mark 5 mounts built without them. This addition, plus the installation of the sheave in the left rear corner of the cradle, greatly facilitates cocking the gun.

CARRIAGE MARK 5

The carriage used on Mark 5 mounts serves a purpose similar to that of the trunnion bracket and pivot Mark 4 on Mark 4 mounts, except that it does not operate on roller bearings. See Page 21. It is bolted to the top of pivot (OE-3503), which operates on two babbitt faced steel thrust bearings. See Figure 21. The length of the two arms extending rearward on the carriage are the same on Mark 4 and Mark 5 carriages.

A different type carriage lock is used to prevent rotation of the carriage when the gun is not in action. It is described in detail on Page 61.

 

60
 

Exploded cut-away view of Mark 5 Mod. 3 Mount.
Figure 21-Exploded cut-away view of Mark 5 Mod. 3 Mount.

 

61
 

CRADLE MARK 4 MOD. 2

The original Mark 4 cradles used on Mark 5 mounts were the same as described on page 22 as they applied to Mark 2 and Mark 4 mounts.

The Mark 4 Mod. 2 cradle used on Mark 5 Mod. 3 mount is the same as used on Mark 4 Mod. 2 mounts. See Page 21 for complete information.

GUNNER'S PLATFORM

A circular raised platform having three step levels surrounds the gun. See Figure 20. Because of the fixed height of the gun, this platform is necessary to enable the gunner to fire at various elevations. For example: When operating the gun at high levels, the gunner will stand on the deck; whereas, when firing at lower elevations it will be necessary for the gunner to move up to one of the higher steps on the platform. This platform is not furnished with the mount, but is a part of the ship's structure.

CARRIAGE LOCK

To prevent rotation, the carriage can be locked in place by lock plunger (OE-3515) which engages in holes in the pivot retainer (OE-3504). This plunger slides in a vertically drilled hole located at the front end of the carriage and is operated by lock lever (OE-3512). See Section E-E, Plate 2. The lever is mounted on a pin (OE-3513) in its boss in the carriage. Two spacers (OE-3518), one located on each side of the lever, prevent the lever from shifting sideways. A rubber bellows type water seal (OE-3519) is stretched over the lever and its boss on the carriage to exclude dirt and moisture from the plunger.

A spring loaded locking ball arrangement consisting of ball (OE-3511), spring (OE-3516), and screw (OE-3517) holds the plunger in either the lower (locked) or upper (unlocked) position.

TRUNNION BRACKET AND PIVOT LOCKING BOLT

This lock is the same as used on the right side of the Mark 4 Mod. 2 mount and locks the cradle in either the 5 degree or 87 degree positions. For complete description see page 22. Also see Section C-C, Plate 2.

GUN SECURING BOLT

This bolt is the same as used on Mark 4 Mod. 2 mount to lock the gun in the cradle. For complete description see page 22. Also see Main Section View, Plate 2.

CARTRIDGE BAG

The cartridge bag and weight used on Mark 5 mounts are the same as used on Mark 4 mounts. See Page 22.

 

62
 

LUBRICATION


Lubrication Chart Mark 5 Mod. 3 Mount
Figure 22-Lubrication Chart Mark 5 Mod. 3 Mount

 

63
 
THE PIVOT CAVITY IN THE PEDESTAL, THE CARRIAGE LOCK, TRUNNION BRACKET AND PIVOT BOLT, AND CRADLE COCKING SHEAVE SHOULD BE WELL LUBRICATED WITH "EXTRA LIGHT MINERAL OIL, NAVY SPECIFICATION 1042, 2110 OR 2075." See lubrication chart, Figure 22.

PIVOT (OE-3503)

Before reinstalling the pivot in its cylinder in the pedestal pour 1.65 lbs. (or 1.95 lbs. if cylinder has a machined relief) of the specified oil into the cylinder. After installation is completed check the oil level which should be up to the bottom of filler plug (OE-3525). Additional oil should be added if necessary.

CARRIAGE LOCK PLUNGER (OE-3515)

Remove lock lever water seal (OE-3519) and with an oil can inserted into the lock lever boss in the carriage, inject a small quantity of the specified oil into the plunger hole. At the same time move the lever up and down several times to thoroughly distribute the oil. Wipe off excess and reinstall the water seal on the lock lever.

TRUNNION BRACKET AND PIVOT LOCKING BOLT (OE-2070)

With cradle rotated to vertical position, oil end of locking bolt that engages the cradle with the specified oil, using an oil can. Distribute the oil into the carriage bearing by moving the locking bolt knob in and out a few times.

CRADLE COCKING SHEAVE

Spin the sheave by hand and with an oil can force the specified oil to the sheave pin.

GUN SECURING BOLT (OE-2188)

Just before the gun is installed in the cradle, thoroughly coat gun securing bolt and the inside of the securing bolt hole in the breech casing with "Anti-seize compound, Navy Specification 52-C-19 (Int.)".

USE OS-1350 GREASE IN PRESSURE OILERS AS INDICATED BELOW.

CRADLE TRUNNION PINS (OE-2161 AND OE-2160)

Force grease into pressure oilers (OE-2259) using grease gun (OE-1637) or (299832-5).

 

64
 

OPERATION OF MOUNT


As the height of the mount is fixed only two steps are involved in its operation. The first step is to press down on carriage lock lever (OE-3512) to disengage plunger (OE-3515) from the retainer. This will then permit the gun to be trained without restriction.

The second step is to pull out trunnion bracket and pivot locking bolt knob (OE-2072) to disengage bolt (OE-2070) from the cradle and turn it one-quarter turn to permit the gun to be elevated without restriction.

 

65
 

PIVOT THRUST BEARING ADJUSTMENT


If, after extensive service, excessive clearance develops between pivot (OE-3503) and its two thrust bearings (OE-3506) correct clearance can again be restored by tightening retainer (OE-3504). This can be done without removing carriage (OE-3520), in the following manner:

Operation
Number

1. Pull out pivot locking bolt knob (OE-2072), see Plate 1, and raise gun to 87 degree position and lock in place.

2. Remove lock screw cover plug (OE-3526) from the carriage. Disengage lock plunger (OE-3515) from retainer (OE-3504) by pushing down lock lever (OE-3512). Rotate carriage (OE-3520) until the head of retainer screw (OE-3505) is visible through the plug hole in the carriage (location of screw indicated by arrow on pedestal just below top edge). Remove the lock screw. See Figure 21.

3. Engage the carriage lock plunger in the retainer and rotate the carriage (OE-3520) and retainer (OE-3504) clockwise (viewed from the top) as far as possible to tighten retainer down on thrust bearings.

4. Release plunger from retainer and rotate carriage clockwise until the plug hole lines up with the locating arrow on the front of the pedestal. Rotate the carriage clockwise until the plunger has passed the first hole in the retainer from the locating arrow. Drop the plunger into the second hole and rotate the carriage and retainer locked together counter-clockwise until the plug hole is in line with the arrow on the front of the pedestal.

Install retainer screw (OE-3505) in retainer. Install hole plug (OE-3526) in carriage.

 

66
 

STRIPPING


The following instructions for stripping the Mark 5 gun mount should be performed in the order given to facilitate the procedure and prevent injury to the personnel.

Precautions should be taken when removing the shield assemblies to be assured of adequate support when loosening and removing the shield bracket to carriage bolts to prevent the shields from dropping.

As instructions call for removing the gun before stripping the cradle and since the cradle spiral spring is under heavy load, note carefully the following precaution. Without the gun in the cradle, the cradle spring and cradle weight will cause the cradle to spring down violently when unlocked from the 5 degree position. It is best for one man to hold the rear end of the cradle while another is unlocking it.

In some instances, the carriage may stick to the top of the pivot. In this case it will be necessary to tap the underside of the carriage lightly with a soft face hammer. To prevent the carriage from dropping off, reinstall two of the carriage to pivot bolts a few turns or use headless guide screws if available. Screws (299989-4) will serve the purpose.

Due to a slight vacuum in the bottom of the pivot cavity in the pedestal it may be difficult to lift out the pivot. Removing the oil hole filler plug in the top of the pivot will facilitate this operation.

For location of the parts by part number, refer to Plate 2-Sectional Details of Gun Mount-which is folded at page 72.

Operation
Number

1. MAGAZINE-Unship the magazine by pushing forward on the magazine catch lever. Uncock the gun.

2. SIGHT-Unship the sight by loosening the three clamping screws (OE-1192), using sight universal spanner (OE-1189). The center screw must be backed out five or six turns and then pushed toward the left side until the stop piece is disengaged from notch in the breech casing. Then slide the sight assembly back toward the trigger cover and lift it off the gun.

3. SHOULDER REST-Press the catch that retains the handgrips and remove the shoulder rest and handgrips by unscrewing counter-clockwise.

4. GUN-Pull down on gun securing bolt withdrawing head (OE-2190) to disengage bolt (OE-2188) from the breech casing and slide the gun out of the cradle to the rear.

5. CARTRIDGE BAG ASSEMBLY (OE-2198)-Remove the two cartridge bag anchor bolts (OE-2172), nuts (OE-2173), and cotter pins (OE-2231) from the carriage and cradle and remove the bag. See Section D-D, Plate 2.

6. WEIGHT AND BAND ASSEMBLY (OE-2207)-Raise the cradle to the 87 degree position and lock in place with trunnion bracket and pivot locking bolt (OE-2070). Cradle spring and cradle weight will cause cradle to spring down violently. Handle with care. Remove weight band pivot bolt (OE-2177), nut (OE-2178), and cotter pin (OE-2230) and remove the weight. See Section B-B, Plate 2.

7. SHIELDS-Remove shield strap (OE-2226) by taking out four bolts (OE-2227) and nuts (0E2229). Remove the right and left shield assemblies by taking out four bolts (OE-3535), nuts (0E2217), and lock washers (OE-2275) attaching each bracket (OE-2220) right and (OE-2221) left to the carriage. One man should hold the shield while the other is removing the bolts.

STRIPPING SHIELD ASSEMBLIES-

Stripping the shield assemblies, if necessary, is accomplished as follows: Remove four bolts (OE-2228) and nuts (OE-2229) attaching brackets to the shield plates.

 

67
 
Operation
Number

8. CRADLE ASSEMBLY (OE-2327)-With the cradle locked in the 87 degree position remove cradle spring housing retaining nut pin (OE-2268) by driving it out with a punch. See Section A-A, Plate 2. Unscrew and remove retaining nut (OE-2163), using wrench (OE-2904).

NOTE-When the spiral spring and housing assembly was assembled to its cover (0E2165), it was turned clockwise two or three notches before its serrations were engaged with those of the cover to keep spring (OE-2169) under tension. Keep hands clear when stripping to prevent injury.

Pull off the housing and spring assembly.

Remove the housing cover by taking out four screws (OE-2256). Drive out cradle trunnion pin securing nut pin (OE-2269) with a punch. Remove retaining nut (OE-2162), using wrench (OE-2904) and spanner (OE-3157). See Figure 52. Drive both cradle trunnion pins (OE-2161) right and (OE-2160) left inwards, and remove from their holes. Lift off the cradle. Key (OE-2191) in trunnion pin (OE-2160) is a press fit in the pin and should not be removed. Any attempt to remove it will result in damaging the pin.

STRIPPING CRADLE ASSEMBLY-

Stripping the cradle, if necessary, is accomplished as follows : Remove cheek plates (OE-2175) right and (OE-2174) left by taking out four screws (OE-2263) from each plate. See Section A-A, Plate 2. Unscrew and remove oiler (OE-2259). Drive out gun securing bolt withdrawing head pin (OE-2261), using a punch and take off head (OE-2190). The bolt (OE-2188) and spring (OE-2189) can then be removed. Drive pin (OE-2262) out of bolt (OE-2188), using a punch. Drive out cocking sheave pin taper pin (12-Z-49-63) from the bottom, cocking sheave pin (299950-3), and remove sheave (299950-2).

STRIPPING CRADLE SPRING AND HOUSING ASSEMBLY-

To strip cradle spring and housing assembly (OE-2312), if necessary, proceed as follows: Remove spring anchor bolt (OE-2168) and its lock washer (OE-2278). Spiral spring (OE-2169) can then be removed. Bushing (OE-2166) is pressed in the housing and should not be removed unless it is desired to replace the bushing.

9. CARRIAGE ASSEMBLY (OE-3508)-Unscrew and remove pivot retainer lock screw cover plug (OE-3526). See Main Section View, Plate 2. Push down on carriage lock lever (OE-3512) to disengage plunger (OE-3515) from retainer (OE-3504) and rotate the carriage until the pivot retainer lock screw cover plug hole is directly over the head of pivot retainer lock screw (OE-3505). The position of this screw is indicated by an arrow on the front of the pedestal, near the top. Remove the screw with a screw driver. Engage carriage lock plunger (OE-3515) with retainer (OE-3504) by raising lock lever (OE-3512) and rotate carriage counter-clockwise until the retainer is unscrewed from its mating threads in the pedestal.

Remove the eight carriage to pivot screws (OE-3521) with a 3/8" special male socket and 1/2" drive swivel end wrench handle. Lift off carriage. If it is necessary to tap the bottom of the carriage to break it loose from the pivot, it is advisable to leave at least two of the carriage to pivot screws turned in a few threads to prevent the carriage from dropping off.

STRIPPING CARRIAGE ASSEMBLY-

To strip the carriage assembly, if necessary, proceed as follows : Unscrew and remove carriage lock spring and ball retainer screw (OE-3517), spring (OE-3516), and ball (OE-3511). Remove lock lever water seal (OE-3519). Drive out lock lever pivot pin (OE-3513), using a punch, and remove lever (OE-3512) and two spacers (OE-3518). See Section E-E, Plate 2. Pull out lock plunger (OE-3515. It is not necessary to remove lock lever plug (OE-3514) unless it is desired to replace it.

 

68
 
Operation
Number

Drive out carriage lock pin and bushing assembly retaining pin (OE-2260) and remove carriage cradle locking pin bushing (OE-2071). Drive knob pin (OE-2140) out of bolt (OE-2070) and remove knob (OE-2072). Remove bolt (OE-2070) and spring (OE-2074) from bushing (OE-2071). Drive the two bushing pins (OE-2141) out of the bushing. See Section C-C, Plate 2.

Unscrew and remove oiler (OE-2259).

If carriage packing (OE-3522) is damaged, remove it with retainer (OE-3523) by driving out the four sheet metal screws (OE-3524) with a small punch inserted from inside. Otherwise the packing and retainer should remain in place on the carriage.

10. PIVOT RETAINER (OE-3504)-Lift the retainer out of the pedestal. Some of the early mounts were equipped with a retainer fitted with an oil seal. If the seal is damaged or otherwise unusable, it may be discarded as it has been found to be unnecessary.

11. PIVOT (OE-3503)-Unscrew and remove pivot oil passage filler plug (OE-3525). With two lifting eyes screwed into the carriage to pivot screw holes in the top of the pivot, lift out the pivot. This should be done slowly to give the oil an opportunity to drain through the oil passage hole into the sump at the bottom of the pedestal and break the vacuum. Upper pivot thrust bearing (OE-3506) will come out with the pivot. The lower pivot thrust bearing can be lifted off the shoulder in the pedestal.

 

69
 

REASSEMBLY


The following instructions for reassembling the Mark 5 gun mount cover the complete reassembling of the mount starting with all serviceable units completely stripped. These instructions should be followed in the order given to facilitate the operations. Adjustment procedure of the pivot retainer is important to assure easy, smooth pivot rotation.

Extreme care should be taken to see that all parts, particularly machined surfaces are wiped clean of dirt, moisture, etc.

For location of parts by part number, refer to Plate 2 Sectional Details of Gun Mount-which is folded at page 72.

Operation
Number

1. PIVOT (OE-3503)-If the pedestal bore has a continuous straight wall, install 850 CC. (1.65 lbs.) of extra light mineral oil, Navy Symbol 1042, 2110 or 2075, in the bottom of the bore. If there is a machined relief in the bore between the upper and lower pivot bearings, install 1000 CC. (1.95 lbs.) of oil. This will provide proper lubrication for all bearing surfaces.

Install two pivot bearing halves (OE-3506) -lower bearing-in bottom of pedestal pivot shoulder. See Figure 21. Assemble this bearing with the babbitted side toward TOP of pedestal, engaging the lugs on the bearings in the notches in the pedestal. Lubricate the bearing with the same oil specified above.

Wipe pivot (OE-3503) clean, lubricate with the same oil specified above and lower it slowly into the pedestal to prevent loss of oil.

Install the second set of thrust bearing halves (OE-3506) on the flange of the pivot with the babbitted side toward the BOTTOM, engaging the lugs on the bearings in the notches in the pedestal. Lubricate the bearing with oil the same oil specified above.

2. PIVOT RETAINER (OE-3504)-Place the retainer with the flat 6% inch diameter bearing surface down into the pedestal and screw it in as far as it will go by hand. With a IA inch dowel draw the retainer down tightly on the thrust bearings. Then back off the retainer about two holes until the nearest hole is in line with the arrow on the front of the pedestal indicating the lock screw position. Install lock screw (OE-3505) and tighten securely.

3. CARRIAGE ASSEMBLY (OE-3508)-REASSEMBLING-Reassemble the trunnion bracket and pivot locking bolt assembly (OE-2009) as follows: Drive the two retaining bushing pins (OE-2141) into bushing (OE-2071) until the outer ends are flush. Place spring (OE-2074) on the small end of bolt (OE-2070), dip it into extra light mineral oil, Navy Symbol 1042, 2110 or 2075 and insert in bushing (OE-2071). Place knob (OE-2072) on end of bolt (OE-2070) and secure it with pin (OE-2140). Place the assembly in the hole in the right side of the carriage, lining up the pin hole in the bushing with the one in the carriage, and drive retaining pin (OE-2260) into the carriage boss to lock the assembly in place. See Section C-C, Plate 2. Check operation and place in unlocked position by pulling out knob and turning it one-quarter turn.

Install pivot retainer lock screw cover plug (OE-3526).

If carriage lock plunger hole plug (OE-3514) was removed, install a new one by setting it in the hole in the carriage with the hollow side toward the bottom and striking the center of the plug with drift (OE-1616) until a dimple is formed in the center of the plug. Assemble carriage lock plunger (OE-3515) after dipping it into extra light mineral oil, Navy Symbol 1042, 2110 or 2075. The grooved end of the plunger should be entered in the hole first.

Install lock lever (OE-3512) and two lock lever spacers (OE-3518) in their hole in the carriage and drive lock lever pivot pin (OE-3513) through the holes in the lever and spacers. See Section E-E, Plate 2. Stake the pin securely at both ends to prevent it from coming out.

 

70
 
Operation
Number

Slide lock lever water seal (OE-3519) over lock lever and seat it in the grooves in the boss on the carriage and lock lever.

Place lock plunger ball (OE-3511) and spring (OE-3516) in their hole in the carriage and screw in retainer screw (OE-3517).

Screw oiler (OE-2259) into its hole in the carriage.

In the event that a new carriage packing (OE-3522) is to be installed, do not assemble it to the carriage at this time. It may curl over and restrict movement of the carriage. However, place the packing in retainer (OE-3523) and place it in position on the pedestal.

4. CARRIAGE ASSEMBLY (OE-3508)- INSTALLATION- Install the carriage on pivot (0E3503) and secure in place with eight carriage screws (OE-3521). These screws should be tightened to 75 foot pounds torque. This torque may be applied by a load of 75 pounds on a wrench handle one foot long, or by the use of a torque tension wrench, if available.

Line up the four holes in packing retainer (OE-3523) with those in carriage (OE-3520) and drive in the four sheet metal screws (OE-3524). Check operation of carriage for binding.

5. PIVOT OIL LEVEL-Check the oil level in filler hole in pivot (OE-3503). If necessary, add extra light mineral oil, Navy Symbol 1042, 2110 or 2075 to bring it up to level of bottom of plug (0E3525). Then install plug and tighten securely.

6. CRADLE ASSEMBLY (OE-2327)- REASSEMBLING-Place cocking sheave (299950-2) in position in slot in rear end of cradle (OE-2325). Drive cocking sheave pin (299950-3) through cradle and sheave and lock in place with taper pin (12-Z-49-63) driven in from the top face of the cradle.

Screw oiler (OE-2259) into hole in trunnion pin boss.

Assemble cheek plates (OE-2175) right and (OE-2174) left, using four attaching screws (OE-2263) in each plate. Assemble the plates with the extensions on the plates forward.

Drive securing bolt locating pin (OE-2262) into hole near center of bolt (OE-2188). Place spring (OE-2189) on small end of bolt and insert bolt into hole in the cradle from the top. Press down on top of bolt, install withdrawing head (OE-2190) and secure it in place on the bolt with securing pin (OE-2261).

7. CRADLE ASSEMBLY (OE-2327)- INSTALLATION-Hold the cradle on the carriage with the gun securing bolt forward and the trunnion pin holes in the cradle and carriage in line. Drive trunnion pins (OE-2161) right and (OE-2160) left outwards so that they pass through the cradle and carriage. See Section A-A, Plate 2. Key (OE-2191) should be in place in trunnion pin (OE-2160) before driving the pin into place. Screw retaining nut (OE-2162) onto trunnion pin (OE-2161), using wrench (OE-2904) and spanner (OE-3157), Figure 52. Lock the nut in place with securing pin (OE-2269). If the holes in the nut and pin do not line up when the nut is tight, back nut off until the holes do line up.

Slide spring housing cover (OE-2165) over carriage pin (OE-2160) and secure it to the carriage with four screws (OE-2256).

Build up cradle spiral spring and housing assembly (OE-2312) as follows: If bushing (0E2166) was removed from housing (OE-2164) press in a new one. Place spiral spring (OE-2169) in housing so that the spring winds clockwise toward the center when looking into the housing. See Figure 23. Install spring securing bolt (OE-2168) and lockwasher (OE-2278) in housing so that the stud end of the screw passes through the anchor hole in the outer end of the spring.

Raise the cradle to the 87 degree elevation and lock it in place by releasing trunnion bracket and pivot locking bolt knob (OE-2072). Slide the cradle spring and housing assembly onto the left trunnion pin with the radial portion of the spring sliding into the spring slot in the trunnion pin, until the notches in the housing are just clear of those on the housing cover.

 

71
 

Correct position of spiral spring in housing.
Figure 23-Correct position of spiral spring in housing.

Operation
Number

NOTE-Keep hands clear of the serrations to prevent injury.

Turn the spring housing clockwise until spring tension is felt, then turn further in the same direction to the second place where the notches in the housing and cover will engage. Force the housing into engagement with the cover. Install spring housing trunnion pin nut (OE-2163) and tighten, using wrench (OE-2904). Lock the 'nut on the pin by driving securing pin (OE-2268) through nut and pin. If holes in the nut do not line up when the nut is tight, back nut off until the holes do line up.

NOTE-In order to improve the balance of the gun when installing the Mark 14 Mod. 2 sight on the rear end of the cradle, or when interchanging solid and ribbed gun barrels, the cradle spiral spring housing may be adjusted one or two notches from the standard setting. Cradle spiral spring spanner (367543-1), Figure 52, will be found helpful when making this adjustment.

8. WEIGHT AND BAND ASSEMBLY (OE-2207)-With the cradle in the 87 degree position install the weight and band assembly to the cradle cheeks, using pivot bolt (OE-2177), nut (OE-2178), and cotter pin (OE-2230). See Section B-B, Plate 2.

9. CARTRIDGE BAG ASSEMBLY (OE-2198)-Lower the cradle to the 5 degree position and lock in place. Place weight and band in bag. Fasten bag to cradle and carriage, using two bolts (OE-2172), nuts (OE-2173), and cotter pins (OE-2231). The nuts should be left sufficiently loose so that the cartridge bag ends can rotate on the bolts. See Section D-D, Plate 2.

10. SHIELD ASSEMBLIES (OE-2316) RIGHT AND (OE-2317) LEFT-Assemble shield plates (OE-2219) or (OE-2289 right and OE-2290 left) to shield brackets (OE-2220) right and (OE-2221) left, using four bolts (OE-2228) and nuts (OE-2229) in each plate.

Bolt the right and left shield assemblies to the carriage, using four bolts (OE-3535), lock washers (OE-2275), and nuts (OE-2217) on each bracket.

Bolt shield strap (OE-2226) to the shield plates, using four bolts (OE-2227) and nuts (OE-2229).

 

72
 

Notes

 

Plate 2
 
PLATE 2
General Arrangement of Mark 5
20 MM Antiaircraft Gun Mount
Between page 72 and 73 (Large size image.)
 

73
 

Notes

 

74
 

LUBRICATION


Lubrication Chart Mark 5 Mod. 4 Mount
Figure 24-Lubrication Chart Mark 5 Mod. 4 Mount

 

75
 

DESCRIPTION


Chapter 4
MARK 5-MOD. 4 GUN MOUNT
MOUNTED ON SUBMARINE

GENERAL DESCRIPTION

This mount is a modification of the Mark 5 Mount for use on submarines. Except for the pedestal, which is designated Mark 5 Mod. 2, all assembled units are the same as used on the Mark 5 Mount. The following changes were made to the Mark 5 pedestal:

(a) The pedestal is cut in two approximately 19" above the base and the upper portion telescoped into the lower part and welded in place. The overall height is reduced approximately 11" 1/2 which reduces the mount trunnion height to 50" 3/4.

(b) Flooding and draining of the pedestal is accomplished by drilling a number of holes in the pedestal. Near the top are four 1" vent holes. Midway between the top and bottom are three 3" holes, and in the edge of the base flange are five 1" 3/4 holes.

(c) The large pipe plug in the lower end of the pedestal pivot cylinder has a 1/2" hole drilled in the center to provide free drainage.

(d) The pivot (299964-1) is modified to provide pressure fittings for the lubrication of the upper and lower radial bearing surfaces. One grease fitting is fitted in the oil passage at the top of the pivot and an additional fitting is located in the side of the pedestal casing approximately 15".4 below the top.

SERVICE DATA

The maintenance, stripping, and reassembly data are the same as applies to the Mark 5 Mount. See Pages 65 to 71. Figures 20 and 21 will suffice for illustrative purposes.

Because of the conditions under which the gun and mount are used there are new problems involved in the maintenance and lubrication of this unit. Additional care is necessary to assure efficient operation upon surfacing and to provide adequate protection to the parts while submerged.

The carriage lock, trunnion bracket and pivot locking bolt and gun securing bolt in particular require frequent servicing to prevent their freezing tight due to accumulation of rust and corrosion. A hole is provided in the pedestal pivot cylinder plug to permit water to drain out. All parts must be frequently cleaned and adequately lubricated with special water resistant grease. See lubrication chart, Figure 24.

CLEANING

Strip the carriage lock, trunnion bracket and pivot locking bolt, and gun securing bolt completely (see Stripping Cradle Assembly and Carriage Assembly, Pages 66 to 71). Wash all parts carefully with Diesel fuel oil. Examine them carefully and remove all traces of rust and corrosion by rubbing with a cloth saturated with Diesel fuel oil.

LUBRICATION-(See lubrication chart, Figure 24)

Apply a light coat of (OS-1350) grease to all bright and cadmium-plated parts. This applies particularly to the carriage lock plunger, trunnion pivot locking bolt, and the gun securing bolt all of which must operate freely in their respective bores.

Apply a generous coat of (OS-1350) grease to the cradle trunnion pin grease fittings, using grease gun (OE-1637).

After initial greasing, lubrication of the pivot should be limited to two strokes of grease gun (OE-1637), With (0S-1350) grease, for each of the two fittings. This is necessary to insure that the pivot reliefs are not filled with grease. An excessive amount of grease would require excessive force to train the gun in cold weather. Rotate the pivot when greasing it.

 

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Notes

 

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Notes

 

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