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DESCRIPTION


Exterior view showing general arrangement
of the 20 mm. A.A. Gun and Mount Mark 10
Figure 53-Exterior view showing general arrangement of the 20 mm. A.A. Gun and Mount Mark 10

 

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Chapter 6
MARK 10 AND MARK 10 MOD. 1 GUN MOUNTS

GENERAL DESCRIPTION

These two mounts are of the Fixed Height Type similar to Mark 5 Mounts, except for the stands. The difference between Mark 10 and Mark 10 Mod. 1 Mounts is in the design of the stand and is explained in greater detail later. Mark 10 Mount is illustrated in Figure 53. Mark 7 or Mark 7 Mod. 1 stands, Mark 7 carriage and Mark 5 cradles are used on these mounts.

The gun can be elevated between 15 degrees below horizontal (depression) and 90 degrees above horizontal the same as Mark 6 Mount. The gun and its cradle can be locked in either the 5 degree or 90 degree above horizontal positions by the cradle lock built in the right side of the carriage. When the mount is installed within splinter bulwarks, carriage extension screws (299946-4) described on page 88 and illustrated in Figure 29 may be used to limit the gun's depression to 3 1/2 degrees.

DETAILED DESCRIPTION

PEDESTAL MARK 7 AND MARK 7 MOD. 1 AND PIVOT

The two pedestals Mark 7 and Mark 7 Mod. 1 are of the tripod type hut differ in manufacturing details. They are made up of a number of steel stampings or rolled shapes and plates welded together. The stand legs on Mark 7 stand are "T" shaped and are 2 inches shorter than the "U" shaped legs used on Mark 7 Mod. 1 stand. These legs are welded at one end to the stand sleeve and at the other end to the base. The base is provided with a number of foot holds for the gunner's convenience.

The pivot housing used on Mark 7 stand is 19 1/8 inches long or 2 inches longer than the one used on Mark 7 Mod. 1 stand. The pivot housing is held stationary in the stand by a draw bolt fitted with a lock washer and nut. The upper end of the housing is threaded for a retainer, the same type as used on Mark 5 Mounts. The same retainer lock screw is also used. The steel cap and gasket secured to the lower end of the pivot housing have four bolt holes on the Mark 7 stand and six bolt holes on the Mark 7 Mod. 1 stand. These caps are fitted with a pipe plug. The plug should be removed when the mount is installed on a submarine.

The pivot is similar to that used on Mark 5 Mounts except that it is hollow and is lubricated with grease instead of oil. A grease fitting located in the top provides lubrication to the two babbitt faced thrust bearings used above and below the pivot flange. The thrust bearings are the same as used on Mark 5 Mounts. Circumferential grooves are provided in the upper and lower pivot radial bearings. These bearings are lubricated by two grease fittings in the stand. One is located near the upper end of the pivot housing and the other fitting is near the lower end of the stand sleeve.

CARRIAGE MARK 7

The arms extending rearward on the carriage are the same length as those on Mark 6 carriage. The base of the carriage is similar to that on Mark 5 carriage, except that the boss for the carriage lock is located slightly to the left of the centerline instead of being on the centerline as on the Mark 5 carriage.

CARRIAGE LOCK

This lock is the same as used on Mark 6 Mount and described on page 83.

CRADLE MARK 5

The cradle is the same type as used on Mark 6 Mounts. See Page 81 for description and operation.

CRADLE LOCK

The cradle lock is the same type as used on Mark 6 Mounts. See page 83 for description and operation.

 

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GUN SECURING BOLT

This lock is the same as used on Mark 6 Mount and described on page 84.

SHIELD

When a shield is used on Mark 10 Mounts it is the Mark 4 Mod. 1 type which employs the offset type shield strap (299951-1) to allow the gun to be depressed 15 degrees.

RING STEP

A ring step 8" high and 8' 10" in outside diameter may be used with this Mount. The lowest angle of elevation attained by a gunner 5' 9" in height, using a shoulder rest and without the ring step, is 4 1/2° elevation. With the 8" ring step, this angle is approximately 6 1/2° depression. Limiting angle changes approximately 4° with 3" change in height of gunner. The ring step is part of the ship's structure and is not furnished by the Bureau of Ordnance. See Figure 53.

 

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LUBRICATION


Figure 54-Lubrication Chart Mark 10 Mount-Surface Vessels
Figure 54-Lubrication Chart Mark 10 Mount-Surface Vessels

 

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PIVOT THRUST BEARING ADJUSTMENT

The procedure of this operation is the same as that applying to the Mark 5 Mount. See page 65.

STRIPPING AND REASSEMBLY

In general the procedure outlined for the Mark 5 Mount applies. See pages 66 to 71. If necessary to remove pivot housing (365904-1) or (367544-1) from pedestal (365900-1) or (367528) remove nut (12-Z-9-245) and lock washer (12-Z-22-255) from the end of draw stud (365905-3) and withdraw the stud from the pedestal. The housing can then be lifted from the pedestal.

Before reinstalling the pivot, coat the inside of the pivot housing lightly with (OS-1350) grease.

LUBRICATION

Three grease fittings are used on this type mount to lubricate the pivot. These are located as follows: One in the top of the pivot, another in the side of the pivot housing near the top and the third in the side of the stand sleeve, near the bottom.

After initial greasing, lubrication should be limited to two strokes of grease gun (OE-1637), using grease (OS-1350), for each of the three 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.

When mounted on surface vessels, lubricate all other parts as described on lubrication chart, Figure 54.

When mounted on a submarine, all other parts should be lubricated as described on lubrication chart, Figure 55.

 

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Figure 55-Lubrication Chart Mark 10 Mount-Submarines
Figure 55-Lubrication Chart Mark 10 Mount-Submarines

 

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Notes

 

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Notes

 

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Notes

 

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