THE 3-INCH FIELD GUN.
THE GUN.
The =Gun= is known officially as the _3-inch Field Gun, Model 1905_.
It is a built-up construction of nickel-steel and consists of a tube
with a rifled bore, 3 inches in diameter, upon which are shrunk the
jacket, locking hoop and front clip hoop. The jacket reinforces the
rear half of the tube. The locking hoop serves to secure the jacket
from any longitudinal movement to the rear. On the under side of the
gun, extending the entire length of the jacket, locking hoop, and front
clip, are formed two recoil guides or clips which fit over and secure
the gun to the guide rails of the cradle. When the gun is fired, it
slides along the guide rails. The dust guard covers the part of the
guide rails between the locking hoop and the front clip. The rifling
of the bore is right-hand twist and starts with 0 turns at the breech
increasing to 1 turn in 25 calibers at 10 inches from the muzzle, then
uniform to the muzzle.
Weights and Dimensions.
Weight of gun 788 lbs.
Calibre 3 inches
Length about 7 feet
Number of lands and grooves 24
Muzzle velocity 1700 ft. sec.
Maximum pressure per sq. in. 33,000 lbs.
Limit of depression (90 mils.) 5 degrees
Maximum elevation (265 mils.) 15 degrees
Maximum range, trail sunk, about 8,500 yds. (5 M)
Range at 15° elevation (265 mils) 6,000 yds. (3½ M)
[Illustration: _3 Inch Field Gun, Models of 1904 & 1905._
_Breech Mechanism Assembled._]
Nomenclature of parts of Gun:—
Jacket.
Locking hoop.
Tube.
Bore.
Rifling.
Lands.
Grooves
Breech recess.
Front clip.
Muzzle.
Dust guard.
Recoil guides or clips.
Chamber.
Recoil lug.
Line sight (front and rear).
Handy oilers.
THE BREECH MECHANISM.
The =breechblock= is of the interrupted-screw type, and is provided
with four threaded and four slotted sectors. The front end of the axial
recess in the block is closed by a bushing. Four ventholes lead from
a cavity in the bushing and permit the escape of gas to the rear in
case of a ruptured primer. On the rear face of the breechblock are cut
gear teeth, in which the gear teeth of the operating lever bevelgear
mesh. The breechblock is concentrically mounted on a hub on the block
carrier, in which the firing-lock case is fitted. Its position in the
breech of the gun with reference to the axis of the bore is eccentric.
The breechblock is closed or locked by a continuous movement of the
operating lever. When the block is swung to the closed position the
front face of the block latch comes in contact with the rear face of
the breech of the gun, thus forcing the latch out of the notch in the
breechblock and back into a recess in the carrier. By continuing the
motion of closing the mechanism, the breechblock is then rotated on
the hub of the carrier and its threads engage with corresponding ones
in the gun. When the breechblock is in the closed position, a lug on
the firing-lock case serves to lock the carrier to the breechblock and
prevents displacement due to a blowback.
=The firing mechanism= belongs to that type known as a continuous-pull
mechanism; that is, no cocking of the firing-pin is required.
=The firing-lock= case is eccentrically fitted in the hub of the block
carrier, in such a position that the axis of the firing-pin is always
in line with the bore of the gun. The vent bushing in the front end of
the breech block through which the firing pin passes when in the fired
position, is fitted eccentrically with reference to the breechblock.
This eccentric arrangement of the breechblock, masks the point of the
firing-pin and prevents any possible contact between the pin and the
primer in the cartridge case when the block is unlocked. The block will
be practically fully locked before any contact between the firing-pin
and primer can take place.
Nomenclature of important parts of Breech & Firing Mechanism.
Mod. 1905:—
_Name of Part_ _Where located_
Breech Block On block carrier
Vent Bushing Front end of block
Block Carrier Hinged to jacket; supports block
Block Stop Screwed into front face of carrier
Hinge Pin Hinges carrier to jacket
Hinge Pin Catch In hinge pin
Extractor In breech recess
Extractor Lever Mounted on hinge pin
Operating Lever Pivoted on block carrier
Lever Pivot Pivots lever on block carrier
Lever Latch In operating lever
Lever Latch Spring In operating lever, lower part
Lever Latch Pivot In operating lever, lower part
Block Latch In recess in carrier
Block Latch Spring Around latch bolt
Firing Lock Case In hub of the block carrier
Locking Bolt Nut and Pin On firing lock case, rear face of carrier
Firing Pin In axle hole, center of firing lock case
Firing Pin Spring Around firing pin
Firing Spring Sleeve Around firing pin spring
Sear In slot in firing lock case
Trigger Fork Rear end firing lock case
Trigger Shaft On rear end firing lock case
Trigger Shaft Detent On trigger shaft
Firing Pallet On pallet shank
Pallet Shank On recoil lug of gun
Firing Handle On firing handle shaft
Firing Handle Bracket Attached to right side of cradle
Firing Handle Shaft Assembled in bracket, right side of cradle
Trip Latch Attached to trip latch plunger
Trip Latch Plunger Assembled to firing handle
Adjusting Screw Assembled to firing handle bracket
Check Nut Assembled in adjusting screw
[Illustration: _3 Inch Gun Carriage, Model of 1902._
_Plan_]
THE GUN CARRIAGE.
=The gun carriage= for the 3-inch gun Model 1905 is of the type known
as the long-recoil, in which the gun is permitted a sufficient length
of recoil (about 45 inches) upon the carriage to render the latter
stationary under firing stresses. The gun is mounted upon a cradle
which forms a housing for the recoil controlling parts. The cradle
rests upon the rocker and has a small traversing motion of 70 mils on
each side of the axis of the carriage. The rocker is journaled upon the
axle and its rear end is supported by the elevating mechanism, which is
seated in the trail.
The principal parts of the carriage are the wheels, axle, trail
and elevating mechanism forming the lower carriage, the cradle and
recoil-controlling parts constituting the upper carriage, and the
rocker and traversing mechanism intermediate between the two. In
addition there are provided shields, ammunition carriers, the road
brake, and the axle seats.
=The Wheels and the Axle.= The wheels are a modified form of the
Archibald pattern, 56 inches in diameter, with 3-inch tires. The axle
is hollow and forged from a single piece of steel. The wheels are held
on by the wheel fastenings.
=Trail.=—The trail consists of two steel flasks of channel section with
the flanges turned inward, tied together by transoms and plates to
form the sight and the tool boxes. Attached to the trail are the trail
spade, float trail handspike, trail handles and the lunette.
=Elevating Gear.=—The elevating gear is of double-screw type and
consists of an inner and outer elevating screw, an elevating-gear
bracket, an elevating bevel gear, two elevating bevel pinions, and two
elevating crank shafts. The inner elevating screw is a steel screw,
threaded with a right-hand thread. It is attached at its upper end by
the elevating pin to the rear end of the rocker. The outer elevating
screw is of bronze and is threaded on the exterior with a right-hand
thread to take the inner elevating screw. On the exterior are also cut
two longitudinal keyways, in which the keys of the bevel gear work.
=Traversing Mechanism.=—The traversing mechanism consists of a shaft,
called the traversing shaft, mounted in bearings in the traversing-gear
case, and a traversing nut moving longitudinally on the shaft, but
restrained from turning with it by its bearings in the gear case. A
cylindrical lug on top of the nut fits in a hole in a bronze traversing
link, the right end of which is pivoted by the traversing-link pivot
to the traversing lug on the underside of the cradle. This pivot is
secured to the cradle-traversing lug by a nut and split pin. The left
bearing of the traversing shaft is split for the purpose of assembling
and rests between two collars on the shaft. The bearing, with the shaft
in place, is slipped into its seat in the gear case, where it is held
in position by two pins.
[Illustration: _TRAVERSING GEAR, VERTICAL SECTION_]
[Illustration: _Elevating Gear_ _Half Elevation and Half Section_]
=The Cradle Complete.=—The _cradle_ supports the gun, guides it in
recoil, and forms a housing for the recoil-controlling parts; it
consists of a flange steel body with the upper edges flanged outward.
The flanges are bronze lined, engage the clips on the gun, forming the
guide rails for the gun on recoil. Riveted to the bottom of the cradle
are four steel forgings, the pintle, traversing lug, rear clip, and
elevating and traversing lock lug. The pintle fits the pintle socket
in the rocker and forms a bearing upon which the cradle is traversed.
The traversing lug has been heretofore mentioned as affording a point
of attachment for the traversing-link pivot. The cradle rear clip, in
addition to embracing the rear end of the rocker, has a broad bearing
on the latter directly over the point of attachment of the elevating
screw.
To relieve the pointing mechanism from all strains in travelling, an
_elevating and traversing lock_ is provided, by which the cradle may be
securely locked to the trail.
The _recoil-controlling_ parts contained inside the cradle are the
_cylinder_, the _piston rod_, the _counter-recoil buffer_, the
_counter-recoil springs_ and the _spring support_.
To the rear end of the cradle is riveted a steel cradle head, rear,
through which the cylinder moves in recoil and projects for attachment
to the recoil lug on the gun by means of the cylinder end stud and nut.
The front end of the cradle is closed by the cradle head, front, and
the retaining ring.
[Illustration: _Recoil Controlling Mechanism_]
The =cylinder= lies inside the cradle and is surrounded by the
counter-recoil springs. Its rear end is closed and has a projection on
the inside to which is screwed the counter-recoil buffer, a tapered
bronze rod which fits with small clearance into a bore at the rear end
of the piston-rod. The front end of the cylinder is closed by a bronze
oiltight gland, through which the piston-rod slides. The cylinder
is filled with a neutral oil called hydroline. The interior of the
cylinder is cylindrical. Three longitudinal ribs or throttling bars of
uniform width but varying height extend along the interior from the
rear end to within 19 inches from the front end. Three notches are
cut in the piston head, forming ports for the passage of the liquid
from one side of the piston to the other. The height of the throttling
bars is calculated so that the resistance which the liquid offers, plus
the resistance of the springs, is constant and such that the recoil
will be checked at the desired point. During recoil the front end of
the cylinder is supported by the spring support.
The _piston rod_ is of steel, and is provided with a bronze piston
head, screwed against a shoulder at the rear end. The head has three
notches cut in its perimeter, which fit over the throttling-bar
projections on the cylinder wall. The rear end of the piston is bored
out to take the _counter-recoil buffer_. In counter recoil the oil in
this bore can escape only by a small clearance. In this way the return
of the gun into battery is so eased and regulated that very little
shock and consequent derangement of the aim of the piece occur. The
front end of the piston-rod is attached to the cradle head, front, by
means of the piston-rod nut.
The _counter-recoil springs_ (three in number each 36 inches long)
are helical, being made from a rectangular steel bar coiled on edge.
They are assembled in the cradle, end to end around the cylinder and
bear in front against the spring support and in the rear against the
cradle head, rear. They are assembled under an initial compression
of approximately 750 lbs. which is sufficient to return the gun into
battery at the maximum elevation. In place of the single counter-recoil
springs a set of three inner and three outer counter-recoil springs is
also being issued.
The _spring support_ forms a support for the front end of the cylinder
and a bearing for the front end of the spring column. It has guide lugs
which fit into and glide along guide rails inside the cradle during
recoil. The spring support is held in place by the retaining ring.
Action of the Mechanism.
The action of the recoil mechanism when the gun is fired is as
follows:—The gun moves to the rear 45 inches on the cradle, carrying
with it the cylinder and compressing the recoil springs. The piston
rod being attached to a fixed part of the carriage in front, (the
cradle-head) does not move. Therefore, since the cylinder moves to
the rear, the oil in it must pass from one side of the piston head to
the other. The energy of recoil of the gun is therefore absorbed by
the resistance which the oil offers when being forced through small
openings between the notches in the piston head and the throttling bars
along the inside of the cylinder and also by the resistance of the
counter-recoil springs to additional compression. The energy stored up
by the springs during this compression, returns the gun and cylinder
to the firing or original position. This return movement is eased and
regulated by the counter-recoil buffer. The piston rod pull and the
spring resistance are transmitted to the carriage, but owing to the
latter’s weight and the resistance opposed to the trail spade by its
engagement in the ground the carriage remains stationary.
Weights and Dimensions.
Weight of gun and carriage complete 2,520 lbs.
Width of track 60 inches
Length of recoil on carriage 45 inches
Amount of traverse of gun on carriage 140 mils
Nomenclature of important parts of the Gun Carriage:—
Axle
Trail, consisting of—
Flasks (right and left)
Tool box
Elevating gear transom
Rear sight box
Spade
Spade Edge
Float
Handspike fulcrum
Cradle, head, rear
Gun slides or Guide Rails
Cradle Pintle
Traversing lug
Rear clip
Lug for elevating and traversing lock
Bracket seat, firing handle
Quadrant fastening
Rear-sight bracket support
Front-sight bracket support
Spring-support guides
Retaining ring, with hasp and fastening
Cradle head, front
Shoulder guard
Cradle brush
Recoil-indicator throw
Recoil indicator
Cylinder head
Cylinder with cylinder end screwed in
Cylinder end stud and nut
Counter-recoil buffer
Rings, packing
Gland
Piston rod, with plug, screwed in
Piston
Piston-rod nut
Filling plug with gasket
Drain plug
Spring support
Counter-recoil springs
Rocker
Cradle Pintle socket
Elevating and traversing lock
Traversing mechanism, consisting of—
Traversing-gear case
Traversing plate
Handwheel with handle and spindle
Traversing shaft
Traversing-shaft bearing in two parts
Traversing link with bushing
Traversing-link pivot with nut
Azimuth pointer and scale
Elevating mechanism, consisting of—
Elevating pin
Inner elevating screw
Outer elevating screw
Wheels guards
Trail handles
Trail seats
Trail-seat supports
Sponge-staff socket
Name plate
Handspike
Lunette
Cradle, consisting of—
Cradle body
Elevating bevel gear
Elevating bevel pinions
Elevating crank shafts, with handles
Elevating screw cover
Axle seats, include—
Seat arms
Seat-arm guards
Foot rests
Tie rods
Shield braces
Apron shield
Apron latches
Main shield, consisting of—
Main shield
Hood
Shutter, open-sight port
Shutter, panoramic-sight port
Top shield, consisting of—
Top shield
Top shield fastenings
Road brake, includes—
Brake beams
Brake shoes
Springs with covers
Brake rods
Brake lever
Brake shaft
Brake segment with two segment racks
Ammunition carriers
Range quadrant case
Panoramic sight case
Front sight
Rear sight, consisting of—
Rear-sight bracket with shank socket
Rear-sight shank
Panoramic sight
Range quadrant
Wheels, consisting of—
Felloe, segments
Spokes
Tires
Hub boxes
Hub liners
Hub-latch plungers
Oil Valve
Carriage bolts and nuts
Hub bands
Hub caps
Wheel fastenings
Plugs
THE 3-INCH GUN (CAISSON) LIMBER.
The =limber= is of metal throughout excepting the spokes and felloes of
the wheels. The principal parts are the wheels, axle, pintle, frame,
ammunition chest, pole, doubletree, singletrees, and neck yoke.
The wheels and wheel fastenings are the same as, and interchangeable
with those used on the carriage. Seats for three cannoneers are
provided by a perforated metal bucket-holder on top of the chest. The
paulin issued to each limber serves as a seat cushion and is held in
place by paulin straps. Grip straps are also provided for use by the
cannoneers when the carriage is moving at rapid gaits. On the sides and
front of, and under the ammunition chest, suitable straps, brackets
and connections are provided for securing all tools and accessories.
With each limber are issued three tubular oil cans, each in the form of
a cartridge and with a capacity of two-thirds of a gallon. These are
intended to hold hydroline, lubricating and coal oil and are carried in
the central row of cartridge holes in the ammunition chest.
[Illustration: 3 INCH GUN CAISSON LIMBER, MODEL OF 1916
SIDE AND REAR VIEWS.]
Weights and Dimensions.
Weight of limber, completely equipped and loaded 1740 lbs.
Weight of gun, carriage and limber, completely
equipped and loaded 4260 lbs.
Number of rounds carried 36
Nomenclature of important parts of limber:—
Pole, complete, consisting of—
Pole body
Neck-yoke counter stop
Neck-yoke stop
Neck-yoke chafing plate
Butt reinforce
Doubletree
Doubletree rods
Name plate
Limber prop
Foot rest
Tie-rods
Pintle with bearing, consisting of—
Pintle
Pintle latch
Pintle latch spring
Wheels and wheel fastenings
Axle
Middle rail
Side rails
Ammunition chest, consisting of—
Hand rail
Door chains
Shot bolts
Bucket holder
Chest rails
Chest-rail connections
Body
Door
Cartridge holes
Diaphragms
Lantern brackets
Grip-straps
Paulin straps
Various tool brackets
Various tools
Paulins
Picket ropes
Lanterns
Canvas buckets
THE CAISSON
The Caisson is made of metal throughout with the exception of the
spokes and felloes of the wheels. The principal parts are the wheels,
axle, pintle, lunette, apron shield, fuze setter bracket, frame, road
brake, and ammunition chest.
[Illustration: _Caisson, Plan_]
The wheels and wheel fastenings are interchangeable with those of
the gun carriage and the limber. The caisson road brake is modeled
after that of the gun carriage, all parts as far as possible being
interchangeable. The frame upon which the ammunition chest rests,
is diamond shaped, and consists principally of two steel side rails
riveted to lugs on the axle, meeting in front to form the lunette for
attachment to the limber, and in rear to form a pintle for attachment
of another caisson in case it is desired to tow several caissons by
one team and limber, as for instance in the ammunition train. In other
respects the construction is similar to that of the limber excepting
that the ammunition chest is much larger and has a capacity of 70
rounds. The front of the chest and the chest door are made of armor
plate. A bracket for the fuse setter is also provided. An apron shield,
similar to the one on the gun carriage is hinged under the axle, giving
the cannoneers at the caisson full protection. A spare-pole body can be
carried under the caisson frame, large end of pole to the front. On the
sides and front of, and under the ammunition chest, suitable straps,
brackets and connections are provided for securing all tools and
accessories. To lock the caissons and limbers, a padlock is provided.
These locks are interchangeable and can be unlocked by the same key.
This key is marked “Ammunition.”
Weights and Dimensions.
Weight of caisson only, completely equipped and
loaded 2820 lbs.
Weight of caisson and limber, both completely
equipped and loaded with 106 rounds 4560 lbs.
Number of rounds of ammunition carried in caisson only 70
Nomenclature of important parts of Caisson:—
Wheels
Wheel fastenings, complete
Axle
Middle-rails
Side rails
Pintle with bearing, consisting of—
Pintle
Pintle latch
Pintle-latch spring
Name plate
Channel supports
Frame handles
Lunette, with nut
Caisson prop, with chains
Road brake, consisting of—
Brake-beams
Brake shoes
Brake rods
Brake-rod springs and covers
Brake shaft, with two keys
Brake segment
Segment rack
Brake lever
Spare-pole fastening
Ammunition chest, consisting of—
Diaphragms
Grip-straps
Paulin-straps
Chest rails
Foot rest
Handrails
Door props
Door handles
Hand rails
Supports and Brackets for attaching various tools and accessories
Apron
Apron latches
Fuze-setter bracket
Fuze-setter latch
Fuze setter
Paulin
Picket ropes
Various tools and accessories
Spare pole
To Dismount and to Assemble Parts of the Gun and Carriage.
=To dismantle and to assemble the breech mechanism.=—Grasp the
operating lever and open the breech; when the block is open, force the
block latch out of its seat in the block by gently pressing it into
its seat in the carrier. Take hold of the block and revolve it to the
left until it stops; then pull it to the rear, taking care not to drop
it. The block latch can now be readily removed. After the firing-lock
case has been removed the operating lever can be removed by forcing
its pivot up from beneath by a gentle pressure from the palm of the
hand. The lever latch can be removed by pressing in on the latch at
a point near its lower end opposite its pivot; a hole in the latch
is cut eccentric with reference to the pivot and a shoulder on the
pivot prevents their displacement until the latch is forced in and the
hole is concentric with the pivot. When this occurs, the pivot can be
readily pulled out and the latch removed. To remove the block carrier
force the hinge pin up by hand until it can be caught by the head,
and by swinging the carrier back and forth, if the pin sticks, it can
readily be removed, taking care not to drop the extractor lever. The
extractor can now be removed from the gun.
=To dismantle and to assemble the firing-lock case and mechanism.=—Take
hold of the milled headed locking bolt situated at the lower end of
the firing-lock case, pull it to the rear; at the same time revolve
the firing-lock case upward about 45° and pull it gently to the rear.
This will remove the case with the firing mechanism complete from
the gun. Press the trigger-shaft detent until it disengages from the
notch in the firing-lock case. This will allow the trigger shaft with
its detent, to be withdrawn. Then gently press on the front end of
the firing pin, forcing it back into the casing. This will allow the
trigger fork to fall out. Then, with one finger placed on the front
end of the sear, force it outward; at the same time grasp the front
end of the firing pin, which is roughened for the purpose. Give it a
sharp pull. This will remove the firing-pin spring and sleeve from the
casing. Then place the front end of the firing pin against a block
of wood, bear down on the firing-spring sleeve until the spring is
compressed sufficiently to disengage the slot in the rear end of the
sleeve from the small lug on the rear end of the firing pin; slightly
turn the sleeve, and then the sleeve can be separated from the spring
and pin. By an unscrewing motion the spring can be removed from the
pin. The sear can be removed by gently pressing it in toward the center
of the casing.
To assemble, reverse these operations, taking care before driving
too hard on the end of the trigger shaft that the square hole in the
trigger fork is in position to receive the tapered end of the trigger
shaft. No tools are required for assembling or dismantling this
mechanism.
=To remove the recoil indicator.=—The ends of the clips of the
recoil-indicator guide are bent down to form stops to hold the
indicator in place. To remove the indicator, these parts are opened up
sufficiently to permit sliding the indicator out of the guide. When the
indicator is assembled, these clips should always be closed down to
prevent its loss.
=To dismount the gun.=—Elevate the muzzle slightly. Remove the recoil
indicator throw, unscrew the cylinder-end stud nut, and shove the gun
to the rear until the clips are free from the guides. As the gun slides
off the cradle, it must be properly supported. For this purpose, from 6
to 8 men working in pairs with lifting bars are required.
=To mount the gun.=—Depress the muzzle slightly. Shove the piece from
the rear over the cradle guides with the clips engaging the guides.
Assemble the cylinder-end stud nut, taking care that the locking stud
on the recoil lug enters one of the recesses provided for it in the end
of the cylinder. Assemble the recoil indicator throw. The dust guard
should be assembled with the gun.
In moving the gun on or off of the cradle particular care must be taken
to support the breech end so that the gun clips remain in line with
the gun slides. The firing shaft is also quite liable to injury during
this operation, and care should be taken to prevent its being struck by
the nozzle of the gun or by implements in the hands of the cannoneers.
The cradle should be placed at the desired elevation and azimuth
before beginning either of these operations and not changed during
its progress, since the working of either the elevating or traversing
mechanisms when the gun is only part way in battery brings an excessive
and unnecessary strain and wear upon those parts.
=To dismount the cylinder.=—Bring the gun to approximately zero degrees
elevation; unscrew the cylinder-end stud nut and the piston-rod nut;
remove the cradle head, front. The cylinder is now free and may be
pulled out to the front.
=To assemble the cylinder in the cradle.=—The counter-recoil springs
and the retaining ring being in assembled position, shove the cylinder
(turned so that the drain plug in cylinder head comes on top) into its
seat from the front, with the projecting stud on the recoil lug of
the gun entering one of the recesses provided for it in the cylinder
end; assemble the cradle head; screw in place the piston-rod nut and
cylinder-end stud nut.
_Be sure that the projecting stud on the gun enters one of the holes
for it in the cylinder end before screwing the cylinder-end stud nut up
all the way._
=To assemble the parts of cylinder after cleaning.=—The parts should
be reassembled immediately after cleaning and inspection, and the
cylinder filled with hydroline oil issued for that purpose. The piston
should be moved back and forth in the cylinder by hand to make sure
that all parts are correctly assembled and are without interference.
The cylinder should then be assembled in the cradle and the gun pulled
from battery by hand and permitted to counter recoil rapidly to insure
that all parts are in proper position for firing. _This should never be
done, however, unless the cylinder is known to be filled with oil._ In
reassembling the parts the condition of the vulcanized-fibre washers
between cylinder head and cylinder, and between cylinder-end stud
and cylinder end should be noted; they should be replaced whenever
necessary to prevent leakage. In removing and inserting the piston rod
care should be taken to keep it central in the cylinder, so as not to
bind, burr, or spring any parts. _The dismounting and reassembling
of the parts of the cylinder should in every case be supervised by a
commissioned officer._ Before firing an inspection should be made to
ascertain that the different parts, especially the piston rod and the
cylinder-end stud nuts, are correctly assembled.
=To pack the stuffing box.=—The stuffing box is packed with five rings
of Garlock’s hydraulic waterproof packing, 0.25 inch square. The
packing is issued cut into rings of such size that the ends meet around
the piston rod. The latter being assembled, each ring, placed so as
to break joints with the preceding one, is forced in succession into
its seat by a packing tool of copper or hard wood, one end of which is
shaped like a carpenter’s gouge and the other end forms a handle strong
enough to stand light taps from a hammer. Such a tool may be readily
improvised by one of the battery mechanics. After the five rings are
firmly seated in the box, screw the gland down on the packing.
In assembling the glands be sure that _at least four_ of its threads
are engaged with the threads of the cylinder head; otherwise the
threads of the gland may be stripped in firing. With new packing it may
be found difficult to insert more than four rings and secure sufficient
engagement of the gland. In such a case the box should be packed with
four rings and the piece fired a few rounds, after which the fifth ring
should be inserted.
=Adjustment of the gland.=—The adjustment of the gland will require
the exercise of some judgment. If screwed up too tight, the frictional
resistance of the packing on the piston rod will be increased so much
that the counter-recoil springs may fail to return the gun to battery,
especially at high angles of elevation. _It should be screwed up just
tight enough to prevent the leakage of oil through the stuffing box._
Ordinarily this can be done by hand, but in cases where hand power is
not sufficient the wrench provided for the purpose should be used. When
its proper adjustment is determined, the gland should be lashed with
copper wire to prevent it from screwing up or unscrewing.
=To remove the piston rod.=—Unscrew the gland sufficiently to release
the pressure of the packing upon the rod; unscrew and remove the
cylinder head. The rod may then be withdrawn from the cylinder. In
dismounting and assembling the cylinder head (and also the cylinder-end
stud), the cylinder should be held from turning by a spanner applied
to the head retainer or flange on the front end of the cylinder. _It
should never he clamped in a vise_, as its walls are thin and not
intended to withstand such usage.
=To remove the counter-recoil buffer.=—Remove the cylinder-end stud
screw; unscrew and remove the cylinder-end stud; the counter-recoil
buffer is attached to the latter.
=To dismount the springs.=—Bring the gun to approximately zero degrees
elevation; unscrew the cylinder-end stud nut and the piston-rod nut;
shove the gun about 1 inch from the battery; attach the sleeve end
of the spring compressor to the cylinder-end stud and put sufficient
strain on the compressor to relieve the retaining ring from spring
pressure; then remove retaining ring (and cradle head) by loosening and
swinging aside the retaining-ring bolts; ease off slowly on the spring
compressor until the springs are free.
=To assemble the double counter-recoil springs.=—With the cradle at
maximum elevation and the trail horizontal, place one outer and one
inner spring in the cradle until the front ends are about 2 inches
in; set up a separator against the forward end of these sections and
enter the second outer and inner springs, keeping the separator upheld
between the sections; similarly when the outer end of the second
section is 2 inches inside the cradle set up the second separator;
place the third outer and inner sections on the recoil cylinder. Screw
the spring centering tool onto the cylinder-end stud, the small end
pointing rearward; pass the sleeve end of the spring compressor through
the gun lug and the inner springs and attach it to the cylinder-end
stud. Enter the rear end of the cylinder in the spring at the front
end of the cradle and push the cylinder back until the springs are at
free height, keeping the spring compressor taut. Attach the block and
fall carried in the battery wagon to the spade of the carriage or to
some improvised support and connect it to the spring compressor; put
sufficient strain on the spring compressor to bring the spring column
to its assembled height.
As the spring column approaches its assembled height the spring
support must be turned so that its guide lugs properly enter in the
spring-support guide grooves in the cradle; assemble the retaining
ring, disconnect the spring compressor and the spring centering tool
from the cylinder-end stud; push the gun back into battery and assemble
the cylinder-end stud nut. When the retaining ring is assembled the
nuts for the retaining ring bolts should be screwed up until they just
come into contact with the retaining ring. If these nuts are screwed up
too tight they will deform the retaining ring, with the result that it
becomes difficult to assemble and dismount the cradle head. A wrench is
provided for turning the spring support to its proper position.
=To assemble the single counter recoil spring.=—The same method is
followed except that no separators are used. The spring compressor is
provided with a second eye at its large end which may be used in case
the sleeve end should become broken; in case this end is used, however,
it will be necessary to pass the compressor through the cradle from
front to rear, through the gun lug. For disconnecting the compressor
the method used is identical to that previously described.
_The cylinder-end stud nut should never be removed when the gun is at
an elevation_, and the gun should not be elevated when the cylinder-end
stud nut is not in place. To prevent the cylinder-end stud from
rotating a screw for the cylinder end is provided. _This screw for
the cylinder end must be removed before attempting to unscrew the
cylinder-end stud._
Since the springs are assembled under an initial load of over 750
pounds, a pull of more than 750 pounds must be exerted upon the spring
compressor in assembling them. This can be done by passing a handspike
through the loop at the rear end of the compressor and making use of
the service of the entire gun squad, or the block and tackle may be
used as described above. _To avoid the possibility of injury to the gun
squad in compressing or releasing the springs, all should be required
to keep arms and bodies away from the front of the spring column during
these operations._