United States. Army. Ordnance Dept.

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

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firing jacks, but heavier. Their function is to prevent the overturn-
ing of the truck when the gun is'fired at low angles of elevation, and
also to take the firing strains. The stability jacks are hinged to the
base plate, one on each side and each is supported by a strut hinged
in a lug secured to the truck chassis. The stability jack floats are
provided with spades.

When the carriage is in the traveling position, the firing jacks and
stability jacks are folded up and secured by chains. The spades are
removed and placed in receptacles provided on the chassis. The
stability jack struts are unpinned from the forward lugs, removed
and carried in holders on the base plate. The tie rods are folded
with the jacks and chained in position.

Two stability rails and tie rods are provided with each mount, one
being straight and the other having an offset. They are crossed
under the rear axle of the truck, the rear ends being located so that
the firing jack floats set in the spaces between the angles of each rail.
The middle angles at the front ends of the stability rails are attached to
the stability rail tie rods, which in turn are connected to the adapters
on the lugs, directly opposite the firing jack lugs, on the base plate.

When the vehicle is to be emplaced, both of the truck wedges are
placed on the ground with the channel side up, and the front wheels
of the truck are run up the channels between the flanges. The pur-
pose of these wedges is to raise the front end of the truck so that the
mount will be level when the rear end is jacked up. Two steel
blocks are provided for blocking the front wheels when they are run
up on the truck wedges.


Rear axle slings. When traveling, the slings hang loosely under
the truck, one on either side of the transmission. The front ends of
the slings are looped around through holes in the base plate and
clamped in place permanently. Two steel rods are inserted in the
rear loops of the slings and placed across the rear end of the chassis
when the mount is emplaced, and two pieces of pipe are inserted in
the front loops of the slings and placed across the ribs on the front
end of the base plate. The purpose of these slings is to keep the


rear springs compressed and the rear wheels off the ground when the
mount is jacked up.

The electrical equipment consists of five lamps receiving current
from a storage battery, suitable wiring, and switching arrangements.

Two three-cell, 6 to 8 volt batteries are provided, one for reserve,
each of 120-ampere-hour capacity, and are carried in a metal con-
tainer which is bolted to the chassis of the truck. One battery,
when fully, charged and in good condition, will furnish energy for
about 24 hours' continuous service for all lamps.


All wiring is permanent and the connecting wires are protected by
steel armor wherever mechanical injury is likely. Should it be
necessary to remove the top carriage, the lead from the battery
which runs through the pintle bolt may be disconnected above the
top of the bolt by unwrapping the insulation and opening the con-
necting plug there provided.

The lamps are specially designed to withstand the shock of firing
and are rated at 2 candlepower. One lamp is provided for illuminat-
ing each of the following parts :

Deflection correction pointer.

Elevation pointer.
Range disk pointer.
Elevation correction pointer.


A snap switch is provided in the main battery lead which controls
all the lamps, and the lamps should be disconnected by means of this
switch when not in use.

The sight for this antiaircraft vehicle is an instrument which in-
cludes all parts used to direct the elevating and traversing of the
mount so that the gun may be pointed properly in elevation and
azimuth. The parts consist of a sight proper (telescope), the sight
mount, range disk, correction scale and pointer. For any visible
target, the data necessary to properly lay the gun consist of fuze
setter range, travel in elevation and deflection, and any desired
arbitrary correction.

The object is brought into the field of view by turning the azimuth
and the angle of site knobs imparting thereby to the sight a move-
ment in azimuth and elevation respectively. The object is followed
by continuing the movement of these knobs. Detailed description
of the model 1917 anti-aircraft sight may be found in separate
pamphlet covering fire-control instruments.


The trenches constitute the most advanced position of a combat
army and the equipment and supplies placed at the disposal of those
occupying them are generally classified under the broad heading of
" Trench warfare materiel."

The trench forms protection against horizontal firing and permits
of secret massing of troops for surprise attacks, and it is the constant
aim of the Air Service, with its photographic equipment and tele-
graphic communications, to reduce this element of surprise. Con-
cealment of the general outline from airplane observation is impos-
sible, but details may be concealed, for an observer in an airplane
can not see whether a trench is occupied unless the airplane flies
dangerously low.

The trenches are carried up to within 200 yards or less of the ene-
my's front line and are the scene of constant watchfulness to prevent
enemy advance and of constant attempts to reduce the enemy per-
sonnel, lower his morale, capture prisoners for the purpose of obtaining
information, and to advance the position of our own lines.

The field artillery is located from 1 to 5 miles or more behind the
front line, in order to protect it from sudden rushes by the enemy,
while the infantry, machine gun, and trench mortar personnel occupy
the trenches interlaced through the intervening terrain to afford this
protection and also to place the personnel of the army in a position
to come into contact with the enemy without being obliged to pass
over a wide intervening stretch of terrain under enemy fire.

The operation of all branches of the service are interrelated, and
nothing is haphazard or independent of the comprehensive plan,
save during the heat of action or in the event of units becoming
isolated, and such movements are temporary only in their inde-
pendence, as their effects are consolidated with the complete plan
so soon as opportunity permits. The air service, field artillery, the
signal service and the tanks are all coordinated through headquarters
with the service of the trenches and communication is maintained
through an elaborate system of telephone and telegraph wires, pyro-
techinic flashlights, flare, or other visual signals.

The trench system includes a front-line trench of broken line for-
mation, whose individual straight lines are from 9 feet to 18 feet in
length. An enemy entering this trench can sweep only the length of





the straight line, and must fight around a barrier for the balance of
the trench. This trench is connected by communication trenches
to a supervision trench located to the rear, and thence by other
trenches, possibly several miles further back, into friendly territory.
The communication trenches are curved, elbowed or zigzagged and
have T or L connections, island pockets, tunnels, bombing pits,
strong points, keeps, shelters, dugouts, or other provisions as the
conditions may demand.

Traps are arranged for the confusion of an enemy entering the
trench, positions are arranged for dropping barbed wire, knives, or
frames quickly into position to retard the advance of the enemy
troops who have gained the trench. Machine gun and mortar em-
placements are built where needed and bomb-proof dugouts pro-
vided for rest quarters, storage and forward dressing stations for the
treatment of wounded.

The narrower a trench is the better the cover which it affords.
Communicating trenches are made of sufficient width to permit of


the carrying of stretchers, and thus allow for the evacuating of the
wounded during daylight. The wider trench submits it to greater
effect from enemy artillery fire, but if trenches are not wide enough
for stretchers, losses result through the detention of casualties in
the trenches until darkness permits of their removal to dressing sta-
tions. The wider trench also permits a more rapid movement of
men and supplies between the front line and rear areas, and thus
reduces the time during which men and supplies are detained under
concentrated fire, and hence reduces the casualties and destruction
from this cause.

Gas is a constant menace in the trenches, as it is heavier than air,
and its effects vary with the nature of the gas employed. Flame or
liquid fire is employed both with a view to inflicting injury to the
enemy and lowering his morale. The presence of water is always
taken into consideration, for the trench is open to water resulting from
rainfall. Provisions are made for footing and drainage, advantage
being taken of natural slope where possible.
183252820 24


Trench warfare has shown the necessity for hurling large charges of
high explosives for comparatively short ranges. This necessity has
led to the development of the trench mortar, a type of weapon that
is a short smooth bore of simple construction. They are muzzle
loaders and use as their projectile a thin- walled shell, known as a
trench-mortar bomb.

In trench warfare the role of trench artillery is to harass the enemy
by engaging living targets where opportunity offers, to attack and
destroy enemy defensive works and obstacles within range limits,
and to prevent the construction of new works.

The trench mortar is essentially a trench artillery weapon of limited
range which will render very efficient service when properly emplaced,
skillfully handled and served.

The trench mortars are divided into three classes, light, medium,
and heavy calibers.

The light trench mortar is very mobile. Its effect against material
is inconsiderable, but is particularly effective against massed troops,
or troops driven into the open, due to its rapidity of fire. These mor-
tars are used to form a barrage behind the hostile line to prevent
reserves and ammunition being brought up. Owing to their high
mobility, limited only by the difficulty of ammunition supply, they
are especially fitted to accompany the infantry as it advances, and
are used to attack machine-gun shelters and other points which have
temporarily checked the forward movement of the infantry.

The medium trench mortar, with its range of approximately 1,200
meters, is very effective against wire entanglements, machine-gun
shelters, strong points, trenches, and other similar objectives not
too strongly protected.

The heavy trench mortar is designed for the attack of heavily pro-
tected shelters and dugouts, trenches, machine-gun shelters, and
strong points. It is seldom used against wire entanglements because
of the large crater formed by the explosion.

In most types of trench mortars the propelling charge is carried
at the base of the bomb and is ignited by striking a pin at the breech
of the piece. The bomb is dropped into the muzzle and slides down
by its own weight until the firing pin ignites the charge.

The types now issued to the service are :

3-inch Stokes trench mortar, Mark I.
6-inch trench mortar, Mark I.

The characteristics of each type will be discussed on the following


The 3-inch Stokes trench mortar is of British origin, and proved a
very useful and excellent weapon owing to its simplicity, light weight,
and the principle of auto-ignition. Its principle has practically been

copied by both the French and our 'armies and applied to other

The mortar essentially consists of the following components: A
smoothbore barrel, a bipod, and base, the complete unit weighing
108 pounds. The barrel is a seamless drawn steel tube, lapped to



size and necked down at one end and called the breech or base end.
To the breech end is fitted a base cap, within which is secured a
firing pin protruding into the barrel. The barrel is supported near
the muzzle end, by a steel bipod fitted with elevating and traversing
screws. The recoil of the mortar is taken up by a base plate against
which the base cap of the barrel rests.


The elevating stand is made of tubular steel, consisting of two
legs attached to a center trunnion by means of a compass joint; these
legs are held apart by a cross stay which is arranged to spring just
past the dead center in such a manner as to hold the two legs rigidly
apart. The trunnion standard is fitted with a pair of bevel gears
operated by a handle, by means of which the elevating screw can
be rapidly raised or lowered. The upper end of the elevating screw
is fitted with a yoke to support the transversing screw shaft, which,


together with a traversing handle and a dog clutch, forms a bolt
and is held in position by a locking pin. A traversing screw carried
by the traversing screw shaft and driven by the dog clutch forms the
means of traversing the mortar by engaging a nut fixed to the barrel.
The barrel can be quickly disconnected from the mounting by lifting
the locking pin and withdrawing the traversing bolt. The barrel may
then be lifted out of position.

The base plate has three depressions. The shape of the base cap
permits the lower end of the barrel to rest in any of these depres-
sions, and by shifting the barrel from one to another a change of 6


in direction of line of fire can be made on either side of the center

In firing position the base plate is embedded in the ground at
about a 45 angle. The lower end of the barrel is placed in the
indentation in the base plate which gives the barrel the direction
nearest to that desired, the upper end of the barrel being supported
by the legs of the bipod. Minor adjustment for direction is secured
by means of the traversing screw. The barrel is then given the ele-
vation corresponding to the desired range by operating the elevating
screw. The range quadrant (or clinometer) , being set for the desired
range, indicates when the barrels has the proper elevation.


The shell or bomb used with this mortar is a cylinder loaded with
high explosive, fitted at its head with a detonating fuze. The weight
of the shell is approximately 11 J pounds. The propelling charge
consists of 12-gauge shotgun shell, which fits in a cartridge container
at the rear end of the shell. To secure additional range, 1 to 3 rings
of ballistite can be placed around the cartridge container. The
range secured with cartridge alone varies from 150 yards at 75
to 300 yards at 40. With cartridge and three rings, the range
reaches a maximum of 750 yards at 40 elevation.

The firing operation is as follows : The shell with propelling charge
in position (the cartridge inserted in the cartridge container and the
rings around the container) is dropped into the muzzle of the mortar,
cartridge end first, and slides down the barrel. The primer of the car-
tridge is fired on impact with the firing pin. Ignition of the ballistite
rings is obtained from the flash of the cartridge through ports in
the cartridge container. The shell, carrying the cartridge case with
it, is projected from the barrel and the mortar is ready for another

The extreme rate of firing under average conditions is about 25
rounds per minute, but 10 rounds per minute is considered the
average effective rate. The crater formed by the shell has a depth
of about 2 feet and a diameter of about 4 feet.

Weights of mortar.


Barrel, ring, clamp, traversing screw, and base cap 43

Bipod (mounting complete) 37

Base plate__ 28


This mortar is an American adaptation of the British 6-inch
Newton trench mortar. It is operated by dropping the shell down the
barrel of the gun and thus igniting the propellent. While the prin-
ciple of firing is the same as in the 3-inch Stokes mortar, the mount-
ing is somewhat different, in that no bipod is employed; the breech
end of the barrel resting on a cupped base plate and being supported
in an overhanging position therefrom by three guy rods. This
weapon is a most effective agent against machine-gun nests, barbed-
wire entanglements, fortifications, etc., but is seldom used against

This mortar consists of the following essential components :

Barrel with clinometer.

The platform, base, guys, and fittings.

The sub-base.

The barrel is of one piece, muzzle loading, having a smooth bore.
The breech is closed and rests in a hemispherical socket supported
upon a stationary platform to which the barrel is stayed by three
adjustable guys. The elevation, which varies from a maximum of 75 to
a minimum of 40, and lateral deviation is made by altering the length
of the guys, which are adjustable by means of handwheels. These
adjustments are determined by the setting of the clinometer attached
to the barrel. The range can be varied by changing either the eleva-
tion of the gun or the weight of the propelling charge.

The setting up of this mortar is a more elaborate proceeding than
the setting up of the 3-inch Stokes mortar. The cast steel base is
bolted to a hardwood platform, which is mounted on a sub-base made
up of timbers and a rectangular iron frame bolted together. The sub-
base may in some cases be dispensed with, as shown on page 373.

The barrel is furnished internally at the breech end with an axial
firing pin or anvil and externally with a guide stud and a misfire
plug. Should the ignition cartridge fail to function when the shell
is dropped down the barrel, the misfire plug permits of the intro-
duction of a small powder charge with fuze for the ignition of the
propelling charge. Graduations are engraved on the barrel on the
right and left of a zero line and are used for traverse setting of the




The base is a steel casting having a machined hemispherical socket
on the upper side to receive the rounded end of the barrel and pro-
vided with a guide groove which engages the guide stud on the barrel
when in position.

The base is bolted to the hardwood platform. Elevating and
traversing guys are anchored to the upper side of the platform, while
the free ends of the guys are hooked into devices on the barrel when
the latter is mounted on the base. Special hooks provide a method


of fastening the guys during transportation. Four wire-rope han-
dles are provided as a means for carrying the platform.

The clinometer consists of a quadrant graduated with an elevation
scale and straddled by a bubble carrier which oscillates about a center
on the quadrant. The bubble carrier is provided with a pair of cross
bubbles. The clinometer is attached to the mortar barrel by steel
bands and a clamping screw.

In laying of the piece, an arrow on the quadrant is set to coincide
with the desired traverse and the indicator on the bubble carrier is
also set coincident with the desired elevation. The guys are then


adjusted so that both bubbles are exactly level, the barrel of the gun
in the desired direction.

The gas ejector consists of a metal head to fit the bore and a tube
at one end of which is a handle. When the gase ejector is pushed down
the barrel the burned gases are forced up through the handle and
out of the gun. When the gas ejector is removed cold air is sucked
through the handle and into the gun. The head is threaded to
receive a wire brush or a sponge head whenever it is desirable to clean
or sponge out the bore.


The projectile is a cast iron fragmentation shell with vanes, weigh-
ing approximately 42 pounds unloaded, and containing a bursting
charge of approximately 11 pounds of high explosive. The pro-
jectiles are fitted with delay and nondelay fuzes.

The propelling charge consists of sporting ballistite contained in
silk bags of 1 and 2 ounces capacity. With these two sizes of bags
a number of combinations can be obtained and the range can be
varied according to these combinations. The maximum charge is


9 ounces and the minimum 3 ounces. The bags are held in place
between the vanes of the shell by a propelling bag holder. The
charge is ignited by an ignition cartridge made from a standard rifle
cartridge which is fired when it strikes the firing pin as the shell
reaches the bottom of the barrel.


Weights, ballistics, etc.

Overall length of barrel inches. . 57

Weight of barrel pounds. . 162

Weight of base do 75

Weight of platform do 160

Weight of sub-base do 530

Weight of shell, loaded (approximately) do 53

Weight of shell box do 10

Range, minimum meters . . 200

Range, maximum do 1, 700


The trend of design for field artillery now proposed and under way
shows several digressions from the present practice.

Motor transportation promises to almost completely revolutionize
artillery design. A motor-drawn carriage is not so limited in weight
as the horse-drawn type, thus permitting heavier and more powerful
weapons. At the same time the carriage must be designed to with-
stand the more severe usage of motor traction.

A further development along the line of motor transportation is the
self-propelled caterpillar mount for field artillery. The performance
of the experimental mounts of this type has been very satisfactory,
and no doubt manufacture in quantity will be ordered in the near
future. The piece is mounted with a suitable top carriage directly
on the caterpillar, and thus forms a self-contained unit capable of
rapid and easy maneuvering. This type of mounting permits of
carrying various calibers of guns and howitzers, and has the further
advantage of permitting all around traverse by maneuvering the
vehicle under its own power. They are also able to negotiate rough
and difficult terrain more readily than any other type of vehicle yet

The self-propelled caterpillar, Mark II, 8 units of which have been
recently issued to the service, is a road vehicle of the track-laying
type; that is, the power is transmitted to the ground through a
flexible, endless track composed of steel shoes, instead of directly
through the drive wheels as in the usual type of truck construction.

This caterpillar has been designed and constructed to mount the
155 mm. gun, and be able to withstand its firing stresses. Although
not primarily a hauling or towing type of machine, it is provided with
a rear pintle for towing an ammunition trailer or similar vehicle. On
each side at the front of the main frame draw hooks are provided for
towing the mount when necessary.

The various units composing the vehicle are assembled on the main
frame which is a rigidly reinforced steel casting. The main frame is
supported on the track by truck roller frames on which it rests
through the medium of an equalizing mechanism and spring buffers.

The power unit of this vehicle is mounted longitudinally at the
forward end beneath the muzzle end of the gun, consisting of a
Sterling U FT" six-cylinder internal combustion engine with its fuel,
carburetion, ignition, lubrication, and cooling systems.



The power developed is transmitted to the drive sprockets, which
drive the track through the following power system. A master clutch
controls the application of power between the engine and main trans-
mission unit containing selective gears by which the speed and direc-
tion of travel are controlled. From the transmission unit the power
is transmitted to two propeller shafts through the steering clutches
and reducing planetaries. These propeller shafts transmit the power
from the intermediate transmission to the final drive gears on the
drive sprockets.


The driving mechanism is so designed that the forward travel of
the vehicle is the pointing 'direction of the gun. The combination of
selective and planetary gears provides four speeds forward and two
reverse. The direction and speed of travel are under the direct con-
trol of a single operator, seated where he is able to obtain full view
ahead and may readily gain access to engine in case of emergency.

The planetary brake, the master clutch, and the gear shift are
operated by hand levers. The planetary brake and steering clutch

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Online LibraryUnited States. Army. Ordnance DeptHandbook of artillery : including mobile, anti-aircraft and trench matériel → online text (page 18 of 19)