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United States. Army. Ordnance Dept.

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

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inches . . 15

Diameter of smallest circle in which a transport wagon will turn do 544

Wheels on transport wagons, rubber tired do 60 by 8

Wheels on limber, rubber tired do 49 by 4

Limber wheels:

Width of track, center to center of tire do 60. 83

Bearing surface do 3. 54

Rear wheels:

Width of track, center to center of tire. . . do. . . . 63. 84

Bearing surface do 4. 74

Maximum width of widest transport wagon (platform) do 102

Maximum height of highest transport wagon (top carriage) do 302

Maximum overall length of longest transport wagon (howitzer) do 314



ANTI-AIRCRAFT ARTILLERY.



In considering the question of antiaircraft materiel it is to be re-
membered that the science of anti-aircraft gunnery has changed prob-
ably to a greater extent than that of any other branch of the service.
It was unheard of at the beginning of the war, and in consequence
has grown from nothing at all to an important phase of operations.
As a result, materiel is constantly changing and can not be said to have
reached a definite basis even at this time. The materiel was greatly
affected also by the change from " position warfare" to warfare of
motion; portability changing from a somewhat neglected factor to one
of paramount importance.

In field artillery practice range problems are presented in connection
with mortars, howitzers, and guns, but the results to be accomplished
and the problems in connection with each of these weapons are quite
different. The provided elevation of the guns of some calibers is
small, while the muzzle velocity of some of the howitzers and all of
the mortars is comparatively low; also the traverse of all three differ-
ent types of weapons is limited. The field target is usually stationary,
maps being available for establishing its position, and ample time
is available in which to figure its range. Observation of the point of
fall of one shot serves as a guide in correcting the range for the next
shot. Frequently it is possible to choose atmospheric conditions
under which the weapon would be employed, and assisting or opposing
longitudinal windage, or driftage due to side windage, is calculated
with the aid of wind gauges.

For anti-aircraft service the problem is entirely different. The
single weapon must be able to cover the elevations of all three types
of the field artillery weapons and preferably have a traverse of 360.
These wide variations in elevation introduce serious recoil problems,
andT the difference in the traverse problem may be to some extent
illustrated by reference to the fact that the total traverse of the 75-
millimeter French, model 1897 Ml, field gun is only 6.

Instead of a stationary target there may be presented one whose
speed is one-sixth of the speed of the projectile itself and whose course
can in no wise be forecast by road direction or terrain formation and
whose position may be at any vertical or horizontal angle. The pos-
sible altitude and speed of airplanes increased from time to time,
making useless the earlier and present basic data to be employed in
the design of protective materiel. Under certain conditions of air-
plane approach the range must be calculated on the instant and there
is no choice as to atmospheric conditions. As the target is not sta-
tionary, range corrections are difficult to estimate by observation.

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While gauges may indicate the direction and force of the wind at the
altitude at which they are set, they furnish no indication of air cur-
rents existing at other altitudes through which it might be necessary
for the anti-aircraft projectile to pass. With the flat trajectory of a
fieldpiece at but a few degrees elevation, the density of atmosphere
through which the projectile must pass is largely uniform, while at




high angles of fire with anti-aircraft guns the projectile
through atmospheres of different rarefactions, and hence different re-
sistances to the passage of the projectile. These influences affect the
trajectory of the projectile, the rate of travel of the projectile, and the
time element of the burning of the fuze.

With field artillery, shrapnel is employed with both a time fuze and
an impact fuze, and high-explosive shell with impact fuze only, but



324

anti-aircraft disrupting projectiles are fitted only with time fuzes, as
otherwise a projectile which has missed its aerial mark would be apt
to cause damage within friendly lines through impact explosion on
reaching the ground.

As there is practically no position which is entirely free from the
possibility of aircraft attack, and as there is no means of determining
the direction from which such attack may come, ready mobility of
anti-aircraft guns is most desirable, and as opportunity to reach the
target is frequently only momentary, rapidity of sighting and of firing
is essential. In the case of indirect fire from a camouflaged position,
the gunner has not even had a view of the approaching plane, but
must lay his gun on the basis of telephone data, or data otherwise
transmitted from the battery commander's station.

The anti-aircraft target may be a balloon either stationary or
towed a dirigible, or an airplane, but is most frequently the latter.
Location of the position of balloons or dirigibles is comparatively
simple, as compared with airplane location, owing to the size of the
target and the stationary position or low speed of motion. For night
fire, searchlights or other illuminating means are required, and for
night fire or protective fire in thick weather, sound-locating devices
are employed.

The earlier fire from anti-aircraft artillery was directed solely from
the burst; that is, by firing a shot, and judging of the direction of the
next shot solely by observation of the nearness to which the burst of
the first shot had approximated the position of the target. In the
meantime, however, the position of the target had changed. This
system has given way to the use of an elaborate system of instruments
for the determination of fire in accordance with certain established
principles.

In the attack upon aircraft the desired end may be accomplished
either by the destruction of the aircraft itself or by the disabling of its
occupants, in which latter case the destruction of the aircraft would
follow. The methods adopted include destruction by incendiarism,
by direct hits, by flying particles from exploding shell or shrapnel,
and by shell shock. Methods of fire may involve explosive projec-
tiles from a single gun, salvos or barrage fire from a number of guns,
rapid firing from pom-poms (small caliber guns, firing explosive pro-
jectiles), or from machine guns firing small arm ammunition.

Because of the important field played by aerial sound-detecting
apparatus, searchlights, and telephony, including wireless, future
progress in the design of anti-aircraft artillery will consider these
subjects. With the perfection of airplane motors and their intercon-
nected functioning apparatus, the design of aircraft, and the art of
flying, other factors upon which the design of artillery equipment
should likewise be based, enter into this problem.



325




3-INCH ANTI-AIRCRAFT GUN MATERIEL, MODEL 1918.



It is hardly possible to estimate how great will be the future
importance of the perfection of the country's aerial defense from a
strategic point of view. Aviation as an offensive arm will remain a
principal arm, and anti-aircraft artillery, as a defense branch, will play
the part that coast artillery plays to the naval squadrons.

Anti-aircraft gunnery differs from other forms of gunnery, such
as field-artillery problems. It is a new subject, one more compli-
cated than any other artillery problem, and consequently one which
essentially demands new methods and modes of measurement. De-
velopment, however, has led to the design of the 3-inch auto-trailer
carriage.

The 3-inch auto-trailer carriage unit consists of a 3-inch gun,
model 1918, anti-aircraft, and a 3-inch auto-trailer carriage, model of
1917, mounted on a four-wheel trailer truck, having springs and solid
rubber tired wheels. The gun and the mount remain fixed on the
trailer, both in traveling and in battery positions.

The muzzle velocity of the gun is 2,400 foot-seconds. Both
shrapnel and high-explosive shells, each weighing about 15 pounds,
are employed. At a maximum elevation of 85 the maximum verti-
cal ordinate, limited by the time fuze, is 7,940 meters. At minimum
elevation of 10 the projectile strikes the ground at approximately
6,100 meters. At 23 elevation the bursting vertical ordinate is
1,176 meters, and the horizontal ordinate approximately 7,025
meters.

The recoil mechanism is similar to that employed with the Ameri-
can 75 millimeter, model 1916, field gun, but with the use of a spear-
head counter-recoil buffer. This recoil mechanism is of the hydro-
spring type and the variable adjustment of the stroke is governed
by a rotating valve, the movement of which moves port holes behind
the edges of three lands permitting the passage of oil to the by-
passing recesses.

The anti-aircraft gun, together with the recoil mechanism, is held
by the cradle and swings from 10 to 85 elevation in the trunnion
bearings of the top carriages. A base plate rigidly bolted to the
trailer chassis supports the top carriage on traversing rollers on which
the top carriage rotates 360 in azimuth around a pintle on the base
plate.

The trailer carriage is equipped with outriggers. Stability and
lifting jacks which, when in firing position, rest on detachable floats

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on the ground and support the entire weight of carriage and trailer.
These outriggers and jacks are employed to stabilize this unit when
in action and to prevent the mount from overturning when the gun
is fired at low angles of elevation.




VIEW OF REAR OUTRIGGERS FOLDED; OUTSIDE END OF RIGHT OUTRIGGER
BRACE READY TO BE PLACED IN RECEPTACLE; SCREW JACK WITH
OUTRIGGERS FOLDED.

In traveling position the outriggers are folded up, the jack screws
raised, the floats and spades being carried in another vehicle, with
the exception of the stability jack floats which are attached to the
jack screws. Traveling locks are provided to lock the gun at about



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331

20 elevation to protect the elevating mechanism. In azimuth the
carriage is locked lengthwise of the trailer to remove unnecessary
strains from the traversing mechanism when the unit is traveling.

Adjustable seats and foot rests for the gunners and platforms that
fold up when traveling are fastened to the top carriage. This unit
is considered able to negotiate any roads suitable for field artillery.
Weight of complete unit is approximately 14,000 pounds.

Fixed ammunition is used with these guns, consisting of time-
fuzed high-explosive, illuminating shell, tracer shell, and shrapnel.
All the shell and shrapnel are issued fuzed.

3-INCH AUTO-TRAILER CARRIAGE.

The 3-inch auto-trailer carriage consists of a 3-inch gun, model of
1918, anti-aircraft, and a 3-inch auto-trailer carriage, model of 1917,
mounted on an autotrailer. -

The gun, of which there are two models, 1918 and 1918MI, is built
up of nickel-steel forgings and consists of a tube, a jacket, and a
breech ring, the latter being screwed to the rear end of the jacket
forming a housing for the breech mechanism. Lugs are provided at
the top and bottom of the breech ring to which are secured, respec-
tively, the recoil cylinder and counter-recoil spring rods. The 19 18MI
model differs from the 1918 model only in the jacket which is 1.6
inches longer at the threaded part allowing a greater thickness of
metal in rear of the jacket, thereby strengthening the gun around
the chamber.

The breech mechanism is practically the same as that used on the
75-millimeter field gun, model of 1916 (American) (see p. 73), being
of the drop block type, semiautomatic, and operated by a handle on
the right side of the breech which is pulled backwards and down to
open the breech.

Weights, dimensions, and ballistics of gun.

Weight of gun (including breech mechanism ). pounds . . 1, 966

Caliber inches. . 3

Total length of gun -do. ... 129. 69

Length of bore : do 120

Volume of chamber : cu. in . . 200

Length of rifled portion of bore inches. . 95. 87

Number of grooves 24

Width of grooves inches. . 0. 2927

Depth of grooves do 0. 03

Width of lands do. ... 0. 10

Muzzle velocity ft. per sec. . 2, 400

Twist, right hand increasing from one turn to 50 calibers at the origin to one

turn in 25 calibers at a point 8.87 inches from the muzzle and uniform from

that point to the muzzle.



332

The carnage comprises the top carriage and cradle. The top
carriage consists of two side frames bolted to a bottom plate which
in turn rests on a circular roller frame and rotates about a pintle on




VIEW OF RIGHT REAR OUTRIGGER WITH JACKSPADE AND FLOAT REMOVED AND
BRACE DROPPED FROM SHACKLE AT INSIDE END; LEFT REAR OUTRIGGER IN
POSITION, WITH FLOAT CONNECTION FOLDED.

the base plate. The base plate is rigidly bolted to the trailer chassis
and is equipped with outriggers and stability and lifting jacks which
when in firing position, rest on detachable floats on the ground and
support the entire weight of the carriage trailer. The top carriage



333



is prevented from tipping or lifting from the traversing rollers by a
front and rear clip which are fastened to the bottom plate and which
engage an annular flange on the base plate.




The recoil mechanism is of the variable recoil hydro-spring type
and operates the same as that of the 75-millimeter field gun, model
of 1916. The only noticeable difference between the two is that a



334

spear buffer is used instead of a valve in the buffer rod head as is
used in the 75-millimeter gun. The length of recoil varies from 16
inches at 85 elevation to 40 inches at 10 elevation.

An elevating arc having teeth is secured to the lower side of the
cradle and meshes with a Hindley worm which is driven through
bevel and spur gears by a handwheel located on the right side of the
top carriage.

The traversing mechanism is attached to the left side of the top
carriage. The handwheel, through bevel gears, a worm, a worm
wheel, and a friction clutch, rotates a pinion which in turn meshes
with an annular rack bolted to the base plate. The pinion when
rotated causes the top carriage to revolve about its pintle on the
traversing rollers.

Four seats are attached to the top carriage, two on either side,
which are used by the personnel who operate the sights and elevating
and traversing mechanisms.

Platforms are bolted to both sides at the rear of the top carriage
for the personnel who load and fire the piece. The platforms may
be folded up and the seats swung to one side for traveling.

When traveling, the gun is locked at an elevation of about 20
and lengthwise of the trailer by upper and lower traveling locks for
the purpose of taking up any strains or shocks which might come on
the elevating or traversing mechanisms.

Weights and dimensions of Carriage.

Weight of carriage unit complete (including spare ammunition chest filled

with ammunition, tools, and accessories) pounds . . 14, 085

Weight of cradle (recoil cylinder complete, including oil, trunnions, gun
slides, piston rod bracket complete, and spring cylinder with springs assem-
bled) pounds . . 1, 2Q3

Weight of trailer (with ammunition chest only, without tools and accessories

or ammunition) pounds . . 4, 085

Weight of trailer with carriage, gun, and ammunition chest only do 13, 200

Weight under front wheels (fully equipped) do 7, 075

Weight under rear wheels (fully equipped) do 7, 010

Weight of one round of ammunition (complete) do 26. 8

Maximum angle of elevation degrees . . 85

Minimum angle of elevation do 10

Traverse of carriage do 360

Maximum length of recoil inches . . 40

Minimum length of recoil do. . . . 10

Number of rounds in ammunition chest 14

Number of rounds in spare ammunition chest 16

Height from ground to center of trunnions inches . . 85

Height from ground to top of gun (in traveling position) do 119

Maximum width of carriage do 77

Maximum length of carriage (drawbar up) do 230

Maximum length of carriage (drawbar down) do. . 243



335



CO




18322820 22



336



The trailer upon which the carriage is mounted consists of two
parallel side frames, between which are secured the cross members,
bracing and making up the complete chassis. Between the front and
rear wheels the frame is so depressed that the base plate of the car-
riage is on the same plane as the hubs of the wheels, thus bringing
the center of gravity of the carriage lower and lessening the possi-
bility of overturning. The space at the front of the trailer formed
by the side frames and cross members is provided with a bottom




FRONT VIEW.

plate, a top plate and hinged cover, and is utilized as a tool box.
The rear section is similar to the front, except that a support is
provided for the ammunition chest. The chest which carriqs 16
rounds of ammunition also serves as a seat for the operators of the
carriage. A foot rest is fastened to the rear tool box cover. The
chassis is supported on the axles, both front and rear by semiellip-
tical springs.

The trailer is towed and steered by a drawbar equipped with a
lunette and fastened to the front axle in such a manner that the




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339

trailer will actually follow in the path of the truck or tractor by
which it is drawn. The trailer may also be steered by the rear
wheels when the rear wheel lock is released and the steering bar is
inserted. A pintle is provided on the rear end of the trailer to accom-
modate any vehicles which may be attached thereto.

This vehicle is equipped with a brake of the internal expanding
type operating within drums attached to the rear wheels and applied
and released by a lever on the right side of the trailer by one of the
personnel seated on the ammunition chest.

Weights and dimensions of Trailer.

Wheelbase inches. . 156

Width of track do 60

Length of frame over all do 200

Width of frame over all do 48. 125

Weight of chassis pounds. . 3, 800

Size of tires inches. . 37

Width of tires .do 6

Height from ground to center line of drawbar do 15

Height from ground to top of frame, empty do 13

Diameter of brake drum .do 16. 625

Turning radius feet. . . 28. 6

Road clearance under front axle inches. . 10. 281

Road clearance under rear axle do 11. 375

Height from ground to center line of pintle do 20. 5

Over-all width at widest part do 77. 25

Center to center at spring pads, front do 28. 5

Center to center to spring pads, rear do 28. 5

The sight issued for anti-aircraft carriages, model of 1918, consists
of two units, one being mounted on the right trunnion of the cradle
and the other on a bracket attached to the left side of the carriage, the
two units being connected by a coupling shaft. The elements on the
right side are the range and elevation corrector and those on the left
side are the angle of site and deflection corrector. An open sight is
attached to the sight proper for rapid location of the target.

All necessary points for night firing are illuminated by the electri-
cal equipment. A 6-volt system is used, the current being supplied
by dry batteries, storage battery, or by a manually operated genera-
tor. Small lamps of one or two candlepower shielded by reflectors,
are used to illuminate the necessary scales and cross hairs.



3-INCH ANTI-AIRCRAFT GUN MOUNT, MODEL OF 1917.



The principle use of anti-aircraft artillery is mainly to hinder avi-
ators from carrying out their missions. The destruction of airplanes,
with the means actually at its disposal, is still a question of luck.
Experience has taught aviators to defend themselves against fire by
continual changes in direction.

The earlier anti-aircraft artillery fire was directed by observation
of the burst, but that eventually gave away to direction of the fire by
carefully deduced principles. Nevertheless, the anti-aircraft artil-
lery theory lays but little stress upon the possibility of inflicting




GUN MOUNT IN ACTION.



damage through a direct hit by the projectile which is fired from the
gun, as it is considered that the possibility of such hit is too remote.
The artillery practice is, therefore, to so direct the projectile that it
will explode at a more or less predetermined position and cause
damage either by the fragmentation of the projectile, which covers a
very much larger volume than the intact projectile, or through the
concussion caused by the exploding projectile and whose effects would
also be felt through a considerable sphere.

No one t}-pe of anti-aircraft gun carriage or mount can possibly
satisfy all conditions of modern warfare. It is, however, possible to

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design a standard gun and top carriage having a wide range of action
and by means of interchangeability enabling Jthis mount to be used
on either a truck mount, a two or four wheel trailer, a caterpillar
tread trailer, or as a semifixed mount, as each of these types of vehi-
cles has its own sphere of action. However, the problem of seacoast
defense and for the defense of depots, etc., led to the design of the
3-inch anti-aircraft gun mount, model of 1917.

The 3-inch anti-aircraft mount is of the barbette type, with con-
stant recoil, designed to be mounted on a solid concrete base about




VIEW SHOWING RIGHT SIDE OF MOUNT.

30 inches thick and IS feet in diameter. The gun mount is designed
to mount the 3-inch anti-aircraft gun, model 1917, 1917, MI, or 1917
Mil, commonly known as the 1 5-pound er gun.

The gun has a 12-inch recoil and a muzzle velocity of 2,600 foot-
seconds. Both high explosive shell and shrapnel may be employed,
the weight of the projectile being 15 pounds, and of the complete
round of fixed ammunition being 28.38 pounds.

The gun is mounted on a cradle of the sleeve type, which also
serves as a housing for the spring and recoil systems. The cradle is



344

suspended by the trunnions from the top of the pivot yoke. The
pivot yoke is bolted to the racer, which rests and revolves on 30
rollers on the roller path of the base plate. The base plate is held
in position in the emplacement by 16 anchor bolts set in the concrete.

The field of fire is 360, to 90 elevation. Removable stops
are provided, however, to limit the elevation of 85, due to possible
injury to the personnel when the piece is fired at a higher angle.

Fixed ammunition is used in these guns, consisting of a time-fuzed
high-explosive shell, illuminating shell, tracer shell, and shrapnel.
Each round consists of the cartridge case with its primer and powder
charge; also the filled and fuzed projectile.

Weights, dimensions, and ballistics.

Weight pounds. . 3, 105

Caliber inches. . 3

Total length do.... 174.65

Length of bore in calibers . 55

Length of rifled portion of bore inches. . 137. 28

Rifling:

Number of grooves 24

Width of grooves .'. inch. . 0. 2927

Depth : do 0. 03

Twist, right hand, 1 turn in 50 calibers atorigin to 1 turn in 25 calibers at 9.28
inches from muzzle; thence uniform.

Weight of projectile, filled and fuzed pounds. . 15

Weight of charge do 5. 32

Weight of fixed ammunition (1 round) do 28. 375

Travel of projectile inches. . 139. 33

Volume of chamber . cu. in . . 296

Muzzle velocity ft. per sec. . 2, 600

Maximum pressure per square inch pounds. . 32, 000

Maximum horizontal range yards . . 12, 755

Maximum vertical range do 9, 000

The model of 1917 gun is built up of alloy steii, consisting of tube,
jacket, and locking hoop. The jacket envelops the rear portion of
the tube and forms the recess or seat for the breech mechanism. A
r ecoil lug projects from the upper surface of the jacket near its
extreme end and affords a point of attachment for the piston rod of
the recoil cylinder. A lug also projects from the under surface, to
which are attached the counterrecoil spring rods. The locking hoop
is forced on the tube and forward end of the jacket, securing the
latter against any rearward movement of the tube under firing
stresses.

The model of 1917 MI gun is similar in general construction to the
model of 1917 gun, except that instead of the breech ring being
integral with jacket, it is a separate piece. The breech end of jacket
is threaded to receive the breech ring, which is screwed and shrunk
on the jacket and held by a lock screw. The locking hoop is omitted.



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The model of 1917 Mil is similar in general construction to the


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Online LibraryUnited States. Army. Ordnance DeptHandbook of artillery : including mobile, anti-aircraft and trench matériel → online text (page 16 of 19)