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United States. Army. Ordnance Dept.

Handbook of artillery : including mobile, anti-aircraft and trench matériel online

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girders are riveted to the carriage trail, the carriage and trail forming
a rigid unit, are supported on the carriage axle which turns in hubs
mounted in the truck frames of the track layer.

On the left-hand side of the carriage is arranged the mechanism
for elevating and depressing the gun. The traversing gear, which
provides means for training 2 either side of the center line, is incor-
porated in the rear section of the trail. This gear consists of a steel
plate resting on the ground underneath the trail: a worm shaft oper-

(253)



254



ated by ratchet wrenches shifts the trail with reference to the plate
and enables the gun to be accurately trained.

Navy guns do not carry the trunnions attached directly to the gun,
but are turned to a smooth surface on the outside. The cylindrical
gun slide, on which the trunnions are attached, carries the gun; the
trunnion seats are placed at the upper end of the carriage. The
recoil and counterrecoil mechanisms are also attached to the gun
slide, operating through pistons atttached to the yoke. The gun
runs in and out of the gun slide when recoiling, bronze liners being
fitted to the inside of the slide to enable this to take place easily.
The trunnions of the gun are mounted sufficiently high so that at
maximum angles of elevation only a shallow trench need be dug to
permit clearance for the recoil of a gun.




TOP CARRIAGE AND AXLE DETAILS.



The elevating arc segment, meshing with the pinion of the eleva-
ting mechanism, is bolted to a pad on the left-hand face of the slide.
The teeth of the arc are cut on a pitch circle concentric with the
trunnion centers to permit of a 40 movement of the slide in a ver-
tical plane, starting from horizontal. The upper and lower extremi-
ties of the arc are fitted with limiting stops to prevent j amming.

The hydraulic brake. The energy of recoil is checked and dissipa-
ted by means of a hydraulic brake mounted on the bottom of the
slide. This mechanism is made up of a piston operating in a cylinder
filled with liquid and rigidly fixed to the slide. The piston is attached
to the gun yoke by the piston rod which passes through a stuffing
box in the rear end of the cylinder. Two orifices are provided in
the piston head for throttling rods w^hich are arranged longitudinally
in the cylinder. In battery, all the liquid is in rear of the piston.
As the piston recedes during recoil, the liquid is forced around the
throttling rods through the orifices in the piston to the forward end



255

of the cylinder, dissipating the erffergy through the frictional heat
generated. The cross section of the throttling rods, around which
the liquid must flow in passing through the orifices, is such that a
pressure approximately uniform is exerted upon the liquid throughout
the period of recoil. The length of recoil is 32 inches.
. Incorporated in the cylinder head is a counterrecoil chamber into
which the recoil liquid flows during recoil. When the gun is brought
back to battery by the counterrecoil mechanism, its momentum is




ASSEMBLED VIEW OF HYDRAULIC BRAKE.

checked through the action of a counterrecoil plunger, mounted on
the forward face of the piston, as it enters the chamber and forces
the liquid back into the cylinder through the orifice between the
plunger and the plunger bushing screwed into the mouth of the cham-
ber. This action takes place during only the last 14 inches of coun-
terrecoil stroke.

The liquid used in the hydraulic brake consists of a mixture of 4
parts glycerine and 1 part water, by volume. This liquid is poured
into the cylinder through a filling hole on the right-hand side of the
cylinder head.

18322820 17



256



The upper portion of the cyliiuter head is arranged to form an ex-
pansion chamber to provide for the expansion of the liquid which
results from the f fictional heat generated in the cylinder. When
expansion of the liquid takes place with continued firing, the increased
volume of the liquid simply compresses the air in the expansion
chamber instead of acting to prevent the return of the gun to battery.
To assure the presence of a definite amount of air in the expansion
chamber at all times, the filling hole is fitted with a tube which extends
down into the chamber and traps the desired volume of air when
the cylinder is filled.

Counterrecoil system. Energy to return the gun to battery and to
maintain it in that position at all angles of elevation is obtained by
means of a pneumatic counterrecoil system, mounted on the top of




VIEW OF AXLE MOUNTED IN TRACK LAYER.

the slide. A piston, operating in an air cylinder and connected to
the gun yoke by a piston rod, serves to compress the air within the
cylinder when the gun recoils. At the end of recoil, the compressed
air acts upon the piston to return the gun to battery. On either side
of the air cylinder and connected with it through a port is an air tube
which serves as a reservoir.

Since it is necessary for the counterrecoil system to support the
weight of the gun and breech mechanism against gravity, the system
is charged initially with air at 300 pounds per square inch, gauge pres-
sure. This pressure assures the proper functioning of the counter-
recoil mechanism at angles of elevation up to approximately 34.
It is apparent that the factor of gravity decreases with the angle of
elevation and hence less pressure is required to bring the gun to bat-
terv when it is fired at angles near horizontal.



257

When charged to 340 pounds pressure, the mechanism will func-
tion properly at all angles; however, if the cylinder should be charged
only to, say, 225 pounds, the mechanism may be relied upon to return
the gun to battery at angles of elevation up to 23 or 24. To insure
return of the gun to battery when firing at angles above 34, air
cylinders should be charged in accordance with the instructions, and
to prevent breakage of the gauge glass and to preserve the accuracy
of the instrument, it is recommended that the pressure gauge be
removed before firing.

The elevating gear train from the rack on the slide to the handwheel
on the left side of the trail is made up of a pinion and shaft in mesh
with the elevating arc. One turn of the elevating handwheel moves
the gun 56' 17" in elevation or depression.

The axle, a steel forging extending across the width of the carriage
is supported in the track layer by a hub bracket which in turn is
carried by the structure of the girder on which the sprocket and truck




L



SIDE ELEVATION OF TRACK LAYER.



wheels are mounted. This bracket is held by oscillating bearings
and is spring supported so that the caterpillar may adjust itself to
any unevenness in the road when the gun is in motion. When the
gun is placed in firing position, the springs are taken up by means
of holding down screws in order that the mount may keep steady on
the point of aim while firing.

The function of the hub springs is to impart to the mount a degree
of resiliency during transit. However, when firing, resiliency in the
mount is undesirable and often dangerous, thus before firing the
springs are compressed until the hubs bear directly upon the truck
frames. This is accomplished by means of adjusting screws screwed
down on the hub bearing blocks until the springs are compressed and
the hubs rest solidly upon the truck frames.

The trade itself consists of an endless belt of cast steel links connected
by hardened pins, each link carrying a corrugated forged-steel plate
which makes contact with the ground. The plates overlap when
horizontal so that a continuous surface is presented. To prevent the



258

corrugated surface of the tread from slipping in soft ground, de-
tachable grousers are provided.

The track links run over a large idler wheel, a sprocket wheel,
seven truck rollers, and four track rollers on each caterpillar track
layer. The sprocket wheels carry but little of the load except when
the gun is descending a grade or when the brake is applied to the
mount. For smooth running and reliability, roller bearings are fitted
in the truck and idler rollers, the ends of the rollers being closed by
steel plates to prevent the entrance of dirt when the mount is hauled
through mud, sand, or soft earth. A brake is provided to permit
control of the mount when descending hills and also to lock the cater-
pillar in position when the gun is set up for firing. The brake con-
sists of a toggle joint operating on the rim of one of the sprocket
wheels, the tension applied being controlled by an adjustable spring.




CARRIAGE IN BATTERY POSITION, SHOWING MAXIMUM ELEVATION OF GUN.

Simple as the brake is it has been exceedingly satisfactory in opera-
tion in controlling the heavy mount on steep grades and in checking
any tendency of the mount to move on firing.

The track is carried around two track idler wheels which are pro-
vided with bearings mounted on the extremities of the track frame.
The aft idler wheel bearings are so mounted that they may be moved
backward or forward as necessary to adjust the tension and to take
up wear on the links and shoes.

Friction brakes operating against the forward idler wheels are
mounted on the truck frames. These brakes are of the spring release
type and are applied by means of handwheels functioning through
yokes and levers to the brake shoes.

The quadrant sigJit (Schneider} is mounted on the left trunnion of
the carriage both in traveling and in action.



8-INCH HOWITZER MATERIEL (VICKERS).



Success has been obtained with the 8-inch howitzer artillery for
preliminary bombardment which precedes an infantry attack. This
caliber is mobile in a sense, but there are limits to its mobility, for
there comes a time when its advance must stop. When these
howitzers have to be transported over land full of huge craters r
with the roads entirely destroyed, the country encumbered with
all kinds of debris and frequently reduced to a sea of mud, it can be
easily seen why a successful "push" usually nets a considerable
gain in captured artillery. If the trenches give way, it is almost
impossible to get the heavy howitzers away quickly enough to save




CARRIAGE IN BATTERY POSITION.

them from being captured by the enemy. Thus, by mobile artillery
is meant that which can be moved around essentially as part of the
infantry.

The howitzer, being comparatively thickset and short when com-
pared with a gun of the same .caliber, is capable of greater angle of
elevation than the same caliber of gun. The gun is primarily
intended for attacking troops, while the chief aim of the howitzer
is to destroy incumbrance such as trenches, barbed wire, pill boxes,
and the like. A shell that travels from the howitzer ascends at a
high angle and drops almost vertically. The explosion of a shell so
fired is much more effective than one that is fired with only a slight
elevated trajectory, as in the case of the field gun.

(259)



260




261

The 8-incli howitzer, being mounted on a wheeled carriage and
not having to he disassembled for transportation, is much more
mobile than the 9. 2-inch or 240-millimeter howitzer. This howitzer
when set up ready for firing rests on and is braced upon a firing plat-
form, which is transported on a two-wheeled wagon, the wagon being
attached to the howitzer carriage and drawn as part of the unit
with the carriage and limber by a tractor. On reaching the spot
selected for position the firing platform is buried flush with the
surface of the ground, furnishing a steady emplacement from which
to fire.

The 8-inch howitzer materiel is called the "Vickers" model of
1917, of which there are in use two types, the Mark VI and Mark
VII. The main differences between the Mark VI and the Mark VII
being that the former has a lower muzzle velocity and consequently
a shorter range than the latter, also that the Mark VII has a barrel
of the "wire wound" construction, whereas the Mark VI type is of
the "built up" construction. The Mark VII is also longer and heavier
than the Mark VI.

The Mark VII has lately been superseded by a Mark VIII^, the
difference between the two being that the powder chamber walls of
the Mark VII proved to be too thin, while the Mark VIII^ overcomes
this defect by having thicker powder chamber walls. Due to the
fact that the Mark VIIIJ howitzer has a greater muzzle velocity,
and consequently a greater maximum range than the Mark VI by
some 15 to 20 per cent, the former is the preferred type.

The life of the howitzers before relining is necessary varies greatly.
'Hie number of rounds they are capable of firing before the lining
becomes badly worn depends on whether light or heavy propelling
charges are used. The use of light propelling charges and greater
trajectory elevation to get the desired range is recommended rather
than heavy charges and low elevation. From information based on
actual experience the average life of the 8-inch howitzer, Mark VI,
is 7,800 rounds, while that of the Mark VHIi is 3,000 rounds.

Comparative table of weights, dimensions, and ballistics for 8-inch hoivitzers, Marks VI
and Vlin and 6-inch gun, Marie XIX.







Mark VI
howitzer
(Mark

VT


Mark
VIII*
howitzer
(Mark


Mark
XIX








VII


VIII-A








carriage).


carriage).


Weight of howitzer or gun, including breech mechanism..
Weight of gun or howitzer without breech mechanism
Total length of howitzer or gun
Length of howitzer or gun


.pounds..
do
..inches.,
calibers


6,552
6,132
127.6
15 9


7,730
7,310
148.3
18 5


10,248
9,940
219.22
36 5


Distance to center of gravity from breech, unloaded . .


inches


42.6


50.5


71 95


Distance to center of gravity from breech, loaded


do


42 3


50 6


71 65


Length of bore.


do


117 7


138 4


210


Length of bore




14 7


17 3


35


Length of rifling...


..inches..


102. 11


99.52


170. 75



262




~ *






263



Comparative table of weights, dimensions, and ballistics for 8-inch howitzers, Marks VI
and VIII\ and 6-inch gun, Mark XIX Continued.







Mark VI
howitzer

(Mark
VI
carriage).


Mark
VIIIJ
howitzer
(Mark
VII
carriage).


Mark
XIX

gun
(Mark
VIII-A
carriage).


Number of grooves




48


48


36


Twist (uniform)


R. H


Iinl5


Iin25


lin 30


Travel of projectile in piece


inches..


104. 96


102 72


174.0


Weight of projectile
Weight of powder charge


pounds . .
do


200
10.75


200
17.5


100
23.0


Max imum powder pressure . . .


...do....


30,250


30,240




Muzzle energy


foot- tons


2 345


3,228


3,308


Muzzle velocity .


feet per second. .


1,300


1,525


2,350


Length of recoil


inches.


60-24


52-24


42-20


Maximum elevation


degrees. .


50


45


38


Range at 15 degrees elevation

Range at 20 degrees elevation


yards.,
.do


6,430
7 S10


7,400
8,900


11,300
13,100


Range at 25 degrees elevation


...do...


8,920


10,500


14,600


Range at 30 degrees elevation . .


.do ..


9,800


11,540


15,960


Range at 45 degrees elevation


do


10 710


12 300






do


10 760


12 360


17,5CO













The Mark VI howitzer has a muzzle velocity of 1,300 feet per
second and a maximum range of 10,760 yards and is of British design
and of both British and American manufacture. The Mark VII
howitzer has a muzzle velocity of 1,525 feet per second and maximum
range of 12,280 yards and is of British design and manufacture.
The Mark VIII| is an American modification of the British wire-
wound Mark VIII howitzer to permit of a built up type of construc-
tion and is strictly of American manufacture. The Mark VIIIJ has
the same muzzle velocity and range as the Mark VIII.

Due to the combination of British and American manufacture,
there are several types of breech mechanism in service; the two
main types are the T and the French percussion type.

The three types of carriages differ but slightly in design. Each is a
two-wheeled vehicle with a box-shaped trail, the latter being cut
away to provide clearance for the recoil of the howitzer or gun when
fired at high angles of elevation. The trails of the Mark VII and
VIII-A types are modified to provide a larger clearance to accommo-
date the Mark VIII^ howitzer and Mark XIX gun (see p. 246) and
are also strengthened to withstand the greater energy of recoil.

The howitzer is mounted in a cradle in which it is free to recoil
under the control of a hydraulic recoil cylinder. After recoil it is
returned to firing position by means of a pneumatic recuperator.
The carriage permits of firing at high angles of elevation, and as the
elevation is increased the length of recoil is proportionally decreased
by a cut-off gear fitted to the cradle and buffer in order that the
howitzer will not strike the trail or ground when fired. The recoil
mechanism is of the hydropneumatic type with a variable recoil
mechanism which lessens the length of recoil the greater the elevation
given the howitzer or gun. The liquid used in the mechanism is
British buffer oil.



264

The elevating mechanism permits a movement of 50 maximum ele-
vation for the Mark VI carriage, 45 for the Mark VII carriage, and
88 for the Mark VIIIA carriage.

The cradle pivots on its trunnions and rests in bearings provided
in the top carriage, which in turn is pivoted at its front center to a
transom on the trad in such a manner that it is free to rotate under




REAR VIEW OF CARRIAGE, SHOWING MAXIMUM ELEVATION OF HOWITZER.

control of the traversing gear, 4 to the right or 4 to the left of the
center line of 'the trail, a total of 8 traverse for each of the three
types.

A quick-loading gear is fitted to the cradle for bringing the howitzer
rapidly to the loading position (7 30' elevation) after firing, and vice
versa.

The trail is composed of two side members supported at the front
end of the axle and terminating in a spade at the rear end. Screw
brakes for use in firing or traveling are fitted to either side at the for-
ward end of the trail.

A traveling lock is provided on the trail to lock the trail and cradle
together to prevent strains on the elevating and traversing mechan-
isms when traveling.



265

The wheels are made entirely of steel and have wide 1 ires fitted wil li
steel cleats to ensure good traction.

The sighting gear is composed of a rocking bar sight with panoramic,
sight and clinometer for the usual method of sighting and a dial sight
for the quick laying of the piece.




RIGHT SIDE VIEW OF CARRIAGE IN BATTERY.

Comparative table of weights and dimensions of 8-inch howitzer carriages, Marks VI and
VII, and 6 -inch gun carriage, Mark VI II- A.





Mark VI.


Mark VII.


Mark VIII-A.


Weight of carriage (only)

Weight of carriage, limber, and howitzer or gun
Weight behind team, heaviest load


pounds..
do....
do


12,548
21,700
29,540
19, 100
528
54.0

"76.6
685
1,008
60
69
95.8
!4 right
4 left
26 right
26 left
66
12
76

256.5
260


12.320
22,650
30,490
20.050
532
64.8
1.700
76.8
749
1,859
60
69
95.8
4 right
4 left
26 right
26 left
66
12
76

276.5

280


12,548
25,110
32,950
22,796


Weight of howitzer or gun carriage in firing position
Weight at end of trial


do....
do


Volume of liquid in recoil cylinder
Volume of air in recuperator cylinders
Volume of liquid in recuperator cylinders
Initial pressure " poun<


.'.pints. .
cu. in..
pints..
Is per sq. in..


64.8
1,693
76.8
740
1;678
60.5


Maximum air pressure


Height of bore above ground


inches . .




do


Width of carriage over axle .


do


95.8
4 right
4 left
26 right
26 left
66
12
76

322.5
325


Angle of traverse


degrees.,
do


Diameter of wheels


inches . .


Width of tires carriage


rin


Width of track, center line to center line of wheels do
Maximum length of carriage, firing position (howitzer or gun hori-


Maximum length of carriage, traveling position (howitzer or gun
horizontal) innhAs







The carriage limber is made of steel and has wide steel-tired wheels.
At the rear is* a limber hook which engages the lunette at the trail
end of the carriage. A chest is mounted on the limber, providing
seats for the personnel, and fittings on the interior for carrying tools.

The limbers which were manufactured in England have wooden
chests, while those manufactured in America have steel chests. A
connecting pole provides for motor transportation when traveling,
the units being arranged in the following order: Limber, gun or
howitzer carriage, and platform wagon, which combination is drawn
by a tractor.



266

These types of carriages are provided with a platform by means of
which a traverse of 26 right and 26 left is obtainable. The plat-
form is used whenever conditions and time permit emplacement.
For transportation the platform is disassembled and placed- on a
transport wagon, which consists of two wheels and an axle, to which
the parts of the platform are securely clamped.
Eight-inch howitzer materiel (British) consists of:
Model of 1917 (Vickers Mark VI and Mark VII).
Model of 1918 (Vickers Mark VII).
Limber, model of 1917 (Vickers).
Firing platform and wagon, model of 1917 (Vickers).
The 8-inch howitzer materiel, model of 1917 (Vickers Mark VI) ,
consists of:

Carriage, model of 1917 (Vickers Mark VI).
Howitzer, model of 1917 (Vickers Mark VI).
Limber, model of 1917 (Vickers).
Firing platform and wagon, model of 1917 (Vickers).
The 8-inch howitzer materiel, model of 1918 (Vickers Mark VII) ,
consists of:

Carriage, model of 1918 (Vickers Mark VII).

Howitzer, model of 1918 (modified from Vickers Mark VIII to

United States Mark VIIIJ).
Limber, model of 1917 (Vickers).
Firing platform and wagon, model of 1917 (Vickers).
The above materiel is of British design and of both British and
American manufacture.



267




* s
B

I s



8-INCH HOWITZER AND CARRIAGE (BRITISH).



The Marie VI howitzer is of the built-up-construction type and
consists of a tube over which is shrunk a jacket. Front and rear
guide rings provide means of supporting the howitzer in the cradle.
A breech ring is also shrunk on for additional strength and carries a
lug for connecting the gun to the recoil mechanism, and a breech
bushing is provided for reception of the breechblock. The total
length of this howitzer is about 10 J feet and its maximum range is
approximately 10.760 yards; this howitzer is mounted on the Mark
VI carriage.




REAR RIGHT SIDE OF CARRIAGE IN FIRING POSITION.



The Mark VI 11$ howitzer is also of the built-up-construction typo,
but differs from the Mark VI howitzer in that it consists of two tubes,
an inner and an outer, over which is shrunk the jacket. The jacket
in this case supports the howitzer without the use of guide rings. A
breech ring is shrunk on over the jacket and carries a lug for connect-
ing the gun to the recoil mechanism. A breech bushing similar to
that of the Mark VI is fitted for the breech mechanism. The total
length of this howitzer is about 12 i feet and its maximum range is
approximately 12,360 yards. This howitzer is mounted on the Mark

VII carriage.

(268)



269




270




271

The breechblock is of the interrupted-screw type. It is operated
by a lever on the right-hand side of the breech, which by one motion
releases the screw threads and opens the breech, or vica versa, on
closing.

The forward mushroom-shaped head of the breechblock is equipped
with a flexible asbestos ring, known as the obturator pad. On firing,
this ring is compressed and acts as a gas check to prevent the leakage
of powder gases back through the breech. It has sufficient resili-
ency to resume its original form after firing, as described on page 216.

For firing the charge, two separate types of igniters or primers are
used. The one known as the T tube consists of a. small T-shaped
copper tube which fits into a suitable socket in the breech; it is fired
by pulling a friction wire out of the tube by means of a lanyard. The




BREECH BLOCK.

other type, the percussion primer, is very similar in construction to a
blank rifle cartridge. It fits a percussion firing mechanism on the
breech which fires the primer by means of a hammer operated by the
lanyard. This mechanism is common and interchangeable with the
155 millimeter gun and howitzer; also the 240 millimeter howitzer.

Howitzers fitted for one type of primer will not permit the use of
the other type. Both types have a safety lock, which prevents
firing when the breech is not entirely closed.

The recoil mechanism is of the hydropneumatic long-recoil type and


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Online LibraryUnited States. Army. Ordnance DeptHandbook of artillery : including mobile, anti-aircraft and trench matériel → online text (page 13 of 19)