[Illustration]
SHRAPNEL SHELL
MANUFACTURE
A COMPREHENSIVE TREATISE ON THE FORGING,
MACHINING, AND HEAT-TREATMENT OF SHELLS,
AND THE MANUFACTURE OF CARTRIDGE CASES
AND FUSES FOR SHRAPNEL USED IN FIELD
AND MOUNTAIN ARTILLERY, GIVING COMPLETE
DIRECTION FOR TOOL EQUIPMENT AND METHODS
OF SETTING UP MACHINES, TOGETHER WITH
GOVERNMENT SPECIFICATIONS FOR THIS CLASS
OF MUNITIONS
By DOUGLAS T. HAMILTON
ASSOCIATE EDITOR OF MACHINERY
AUTHOR OF “ADVANCED GRINDING PRACTICE,”
“AUTOMATIC SCREW MACHINE PRACTICE,”
“MACHINE FORGING,” ETC.
_FIRST EDITION_
NEW YORK
THE INDUSTRIAL PRESS
1915
COPYRIGHT, 1915
BY
THE INDUSTRIAL PRESS
NEW YORK
PREFACE
The design of shrapnel and the machining of its component parts
are matters which, at the present time, are of world-wide interest
to manufacturers, engineers, toolmakers, and mechanics in general.
Shrapnel is used in enormous quantities in the great European war,
and American machine tool builders have been called upon to provide
machines and tool equipment of the latest and most efficient design to
meet the demands made upon the manufacturers of shrapnel. Many shops
are running full force, day and night, and are months behind with their
orders. The great importance of shrapnel manufacture, at the present
time, is, therefore, unquestioned.
A small percentage of shrapnel shells are now made from bar stock, but
most shrapnel bodies are made from forgings, formed hollow in hydraulic
presses or in forging machines. The forging processes, which are of
extraordinary interest, especially to those who know something of the
difficulties attending them, are, however, not finishing processes.
Whether made from the bar or forged hollow, all shrapnel shells must be
very accurately finished by machining.
This book has been brought out to meet the demands for a treatise
dealing comprehensively with the construction, forging and machining
operations, and the tool equipment used for making the shell, fuse
parts, and brass cases. In this book are included not only the
unusually complete articles on shrapnel manufacture contained in the
April, 1915, number of MACHINERY, of which 5000 extra copies were
printed and 5000 additional reprints made, all of which have been sold,
but it also includes all other material that has been published at
various times in MACHINERY relating to shrapnel manufacture, together
with a great deal of material obtained by the Editors especially for
this book; and, in addition to this, it contains abstracts of the
official specifications, together with line-engravings of the details
of Russian, British, and American shrapnel shell bodies, fuses, and
cartridge cases. Hence, it is believed that the book will prove
the most valuable addition to the literature on the manufacture of
munitions that has been made since the beginning of the great war.
D. T. H.
NEW YORK, _October, 1915_.
CONTENTS
CHAPTER I.
Shrapnel Shells 1-19
CHAPTER II.
Forging Shrapnel Shells 20-39
CHAPTER III.
Machining and Heat-treatment of Shrapnel Shells 40-74
CHAPTER IV.
Machines and Tools for Shrapnel Manufacture 75-142
CHAPTER V.
Making Fuse Parts 143-171
CHAPTER VI.
Making Shrapnel Cartridge Cases 172-193
CHAPTER VII.
Specifications for the Manufacture and Inspection of the
Russian 3-inch Shrapnel Shell 194-212
CHAPTER VIII.
Specifications for the Manufacture and Inspection of the
Combination Fuse for Russian 3-inch Shrapnel Shells 213-230
CHAPTER IX.
Specifications for the Manufacture and Inspection of
Russian 3-inch Shrapnel and High-explosive Cartridge Cases 231-250
CHAPTER X.
Specifications for British 18-pounder Quick-firing
Shrapnel Shell 251-259
CHAPTER XI.
Specifications for British Combination Time and Percussion
Fuses 260-275
CHAPTER XII.
Specifications for British 18-pounder Quick-firing
Cartridge Case and Primer 276-285
CHAPTER XIII.
Specifications for American Shrapnel Shells 286-292
INDEX 293-296
CHAPTER I
SHRAPNEL SHELLS
In naval, coast defense and artillery operations, several types of
explosive shells are used; the chief ones are: the armor-piercing
shell, made to pierce armor-plate before exploding; shells exploded
by means of a timing fuse; shells exploded by either a timing or
percussion fuse; and shells exploded by percussion only. Each different
shell has some definite function to fulfill, and is designed for
that purpose. For field or artillery operations, the shrapnel and
lyddite are the two principal types used. Of these, shrapnel is the
most prominent, because of its destructive power and its interesting
mechanical construction.
=Early Development of Shrapnel.=--The shrapnel shell was invented
in 1784 by Lieut. Henry Shrapnel, and was adopted by the British
Government in 1808. As is shown at _A_ in Fig. 2, the first shell was
spherical in shape, and the powder or explosive charge was mixed with
the bullets. Although this type of shell was an improvement over the
grape and canister previously used, its action was not altogether
satisfactory, as the shell, on bursting, projected the bullets in all
directions and there was also a liability of premature explosion. In
order to overcome the defects mentioned, Col. Boxer separated the
bullets from the bursting charge by a sheet-iron diaphragm, as shown at
_B_ in Fig. 2. This shell was called a diaphragm shell to differentiate
it from the first shell of this type.
In the shell made by Col. Boxer, the lead bullets were hardened by the
addition of antimony, and as the bursting charge was small, the shell
was weakened by cutting four grooves extending from the fuse hole to
the opposite side of the shell. Shells of spherical shape were first
fired out of plain-bored guns, and upon the advent of the rifled gun
it was necessary to add a circular base, which was made of wood and
covered with sheet iron or steel to take the rifling grooves. The first
shrapnel shells were made of cast iron, but a later development was to
use steel and elongate the body, reducing it in diameter. The diameter
of the bullets was also reduced so that a greater number could be
contained in a slightly smaller space. The improved shrapnel was also
capable of being more accurately directed.
=Shrapnel Shells of Present-day Design.=--Shrapnel shells, as used
at the present time by the different governments, vary slightly in
construction and general contour as well as in the constituents
entering into their different members. As shown in Fig. 1, a completed
shrapnel comprises a brass case carrying a detonating primer and the
explosive charge for propelling the projectile out of the bore of
the gun. The projectile itself comprises a forged shell that carries
the lead bullets and bursting charge. Screwed into the front end is
the combination timing and percussion fuse which can be set so as to
explode the shell at any desired point, and from which the flame for
exploding the bursting charge is conveyed through a powder timing train
and a tube filled with powder pellets down through the diaphragm to the
powder pocket.
Of these members of a shrapnel, the shell and timing fuse present the
most interesting features from a mechanical standpoint. The shell used
by most governments is made from a forging, machined to the desired
dimensions in hand and semi-automatic turret lathes as well as in
ordinary engine lathes. The fuse is an extremely accurate piece of
mechanism, and is largely produced from screw machine parts, some of
which, however, are forged previous to machining. The brass cartridge
case--the next member of importance--is drawn from a brass blank by
successive operations in drawing presses, and is indented and headed.
Following this, several machining operations are performed on the head
and primer pocket.
[Illustration: Fig. 1. Types of Shrapnel Shells used by the American,
Russian, German, French, and British Governments]
=Types of Shrapnel Shells.=--Shrapnel shells are made in two distinct
types, one of which is known as the common shell, and the other as
the high-explosive. The common shell is a base-charged shrapnel,
fitted with a combination fuse, whereas the high-explosive shell is
fitted with a combination fuse and, in addition, with a high-explosive
head, the head also bursting and flying into atoms upon impact. The
high-explosive shell is not ruptured upon the explosion of the bursting
charge in the base, but the head is forced out and the bullets are
shot out of the case with an increased velocity. In the meantime,
the head continues in its flight and detonates on impact. This type
of shell is not used as extensively as the common shrapnel, and,
therefore, the common shrapnel shell alone will be taken up in the
following.
[Illustration: Fig. 2. Original Shell designed by Lieut. Henry Shrapnel
and Col. Boxer’s Improvement]
=The Explosive Charge.=--Reference to Fig. 1 will show that as far
as the construction of the shrapnel shell and case is concerned,
there is very little difference in those employed by the various
governments. Starting with the cases, it will be seen that these are
almost identical, except for length and the arrangement of the head for
carrying the detonating primer. There is a marked similarity in this
respect between the Russian, the British, and the German, and between
the American and the French. The form of the explosive charge held in
the brass case differs in almost every instance, but without exception
smokeless powder in some form or other is used. In the American shell,
nitrocellulose powder composed of multi-perforated cylindrical grains
each 0.35 inch long and 0.195 inch in diameter are used. In the Russian
case, smokeless powder of crystalline structure is used. In the German,
smokeless (nitrocellulose) powder in long sticks and arranged in
bundles is held in the case. The French use stick smokeless powder
¹⁄₂ millimeter (0.0195 inch) thick by 12.69 millimeters (¹⁄₂ inch)
wide. Two lengths or rows of this powder are arranged in the case.
The British use a smokeless powder of crystalline structure somewhat
similar to the Russian, but in some cases cordite has also been used,
although of late this type of powder has not been quite as commonly
employed.
The detonating agent or primer held in the head of the case varies in
almost every type of shrapnel. Practically all primers are provided
with “safety heads,” so that the shrapnel can be handled without danger
of premature explosion. The object, of course, of the detonating agent
or primer is to detonate or cause the sudden explosion of the explosive
charge in the shell for propelling the shrapnel out of the field gun.
=The Shrapnel Shell.=--The shell itself, as previously mentioned,
is made either from a forging or from bar stock. Forgings, however,
are used to a greater extent than bar stock, because the forged
shell is more homogeneous in its structure than the bar-stock shell,
and piping--a serious objection in the bar-stock shell--is entirely
eliminated. The shells used by the British, Russian, and German
governments are made almost exclusively from forgings, whereas those
used by the French and American governments are made both from forgings
and bar stock. When the French shell is made from bar stock, an
auxiliary base is screwed into it to eliminate any danger of piping.
Near the base of all shells is a groove in which a bronze or copper
band is hydraulically shrunk. This is afterward machined to the desired
shape and takes the rifling grooves in the gun so as to rotate the
shell when it is expelled. The body of the shell itself is slightly
smaller than the bore in the gun, and the rifling band, which is
larger and which is compressed into the rifling grooves, rotates the
projectile, thus keeping it in a straight line laterally during flight.
The bursting charge, which in practically all cases is common black
powder, is carried in the base of the shell and is usually enclosed
in a tin cup. Located above this is the diaphragm which is used for
carrying the lead bullets out of the shell when the bursting charge
explodes and distributes them in a fan shape. In most shells, upon
exploding, the nose blows out, stripping the threads that hold the
members together. It will, therefore, be seen that, in the explosion,
the entire fuse, fuse base, tube, diaphragm and bullets are all
ejected, the shell itself acting as a secondary cannon in the air.
The number of lead bullets carried in the 3-inch shrapnel shells ranges
from 210 to 360. In all cases, the lead bullets are about ¹⁄₂ inch in
diameter, weigh approximately 167 grains, and are kept from moving in
the shell by resin or other smoke-producing matrix. The matrix put
in with the lead bullets, in addition to keeping them from rattling,
is also used as a “tracer.” It is of importance in firing shrapnel
that the position of the explosion be plainly seen. With large shells
this is not difficult, but with shrapnel for field guns at long range
certain conditions of the atmosphere make it difficult to see when
the shell actually bursts. Various mixtures are used to overcome this
difficulty. In some cases, fine-grained black powder is compressed in
with the bullets in order to give the desired effect. In the German
shrapnel, a mixture of red amorphous phosphorus and fine-grained
powder which produces a dense white cloud of smoke is used, and in the
Russian, a mixture of magnesium antimony sulphide is used. The range of
a 3-inch shrapnel shell is about 6500 yards, and the muzzle velocity
of the quick-firing field gun ranges from 1700 on the American to 1930
feet per second on the Russian field gun. The duration of flight ranges
from 21 to 25 seconds.
=Development of Timing and Percussion Fuses.=--The first fuses used
in field ammunition were short iron or copper tubes filled with a
slow-burning composition. These were screwed into a fuse hole provided
in the shell, but there was no means for regulating the time of
burning. Later--about the end of the seventeenth century--the fuse
case was made of paper or wood so that by drilling a hole through into
the composition the fuse could be made to burn for approximately the
desired length of time before exploding the shell, or the fuse could be
cut to the correct length to accomplish the same purpose.
For a considerable time all attempts to produce a percussion fuse were
unsuccessful. Upon the discovery of fulminate of mercury in 1799,
the chief requirement of a percussion fuse was obtained. About fifty
years elapsed, however, before a satisfactory fuse was made. The
first percussion fuse was known as the Pettman fuse, and comprised a
roughened ball covered with detonating composition that was released
upon the discharge of the gun. When the shell hit the desired object,
the ball struck against the inner walls of the fuse, exploded the
composition and powder charge, thus bursting the shell. There are at
the present time three principal types of fuses in use: First, those
depending on gas pressure in the gun setting the pellet of the fuse
free--this is a base fuse; second, those relying on the shock of
discharge or the rotation of the shell to set the pellet free--used in
nose and base fuses; third, those depending on impact.
In shrapnel shells advantage is taken of two types of fuses, one of
which is the combination timing and percussion fuse used on common
shrapnel, and the other the combination timing and percussion fuse of
the high-explosive type used on high-explosive shrapnel. These types of
fuses are again sub-divided, but only in the manner of construction.
The most common fuse is that known as the combination timing and
percussion fuse of the double-banked type. This is used in practically
all shrapnel fuses except the French. The advantage of the double ring
of composition shown at _A_ and _B_ in Fig. 3 is to give a greater
length of composition and more accurate burning. Triple-banked and
quadruple-banked fuses on the same principle have been designed, but at
the present time have not been introduced.
=Operation of Combination Timing and Percussion Fuses.=--The manner
in which the combination timing and percussion fuse is regulated to
discharge the bursting charge in the shrapnel shell is interesting and
involves extremely difficult mathematical calculations. Before going
into the method of setting the fuse, it would probably be advisable
to describe briefly just how the fuse operates. As an example of the
double-banked fuse, Fig. 3 shows that adopted by the United States
government. The following description applies to this type of fuse.
[Illustration: Fig. 3. American Type of Combination Timing and
Percussion Fuse used on Shrapnel Shells]
Assume, first, that the timing ring is set at zero. The propelling
force given to the shrapnel shell in leaving the bore of the gun is
such as to sever the wire _C_ from plunger _G_. Plunger _G_ carries a
concussion primer which is discharged by hitting firing pin _D_. The
flame passes out through vent _E_, igniting the powder pellet _F_ and
the upper end of train _A_, and then through the vent _H_. From here,
the flame is transmitted to the lower timing ring _B_ through vent _I_
and the magazine _J_, and from there through the tube to the bursting
charge in the base of the shrapnel shell.
Assume any other setting, say 12 seconds. The vent _H_ is now changed
in position with respect to vent _F_ leading to the upper timing
train, and the vent _I_ leading to the powder magazine _J_ is also
changed. The flame, therefore, now passes through vent _E_ and burns
along the upper time train _A_ in a counterclockwise direction until
the vent _H_ is reached. It then passes down to the beginning of the
lower timing train and burns back in a clockwise direction to the
position of vent _I_, from which it is transmitted by the pellet of
compressed powder in this vent to the powder magazine _J_. It should be
understood that the annular grooves in the lower face of each timing
train do not form complete circles, a solid portion being left between
the grooves in the ends of each. This solid portion is used to obtain
a setting at which the fuse cannot be exploded and is known as the
“safety point.” As shown in Fig. 6, it is marked _S_ on the adjustable
timing ring.
[Illustration: Fig. 4. Russian Type of Combination Timing and
Percussion Fuse used on Shrapnel Shells]
The timing fuse shown in Fig. 3 is of the combination timing and
percussion type, and if the wire _C_ fails to release percussion
plunger _G_, the shell is exploded by means of a percussion fuse
which comes into use when the shell strikes. The percussive mechanism
consists of a primer _K_ held in an inverted position in the center
of the fuse body by a cup located beneath the percussive primer.
Percussion plunger _L_ works in a recess in the base of the fuse body
and is kept at the bottom of the recess away from contact with the
primer by a light spring in plunger _M_. The firing pin _N_ is mounted
on a fulcrumed pin, and is normally kept in the vertical position by
means of two side spring plungers. When the shell strikes, the impact
causes the plunger to snap up against the primer after compressing the
spring in pin _M_. This causes the firing of the primer _K_ and the
explosive charge passes out through a hole in the percussion plunger
chamber, not shown, to the magazine _J_ and from there down to the
powder in the base of the shell
=Russian Fuse.=--The Russian fuse shown in Fig. 4 differs only in a few
minor details from the American fuse, the chief difference being in
the arrangement of the percussive mechanisms. The percussive plunger
for the timing arrangement is kept up from the firing pin by means of
a spring bushing _E_ surrounding the body of the plunger. This bushing
is expanded by the plunger which is forced through it due to the force
of the shrapnel in leaving the bore of the gun. The spring _B_ in the
head of the fuse assists the plunger in expanding bushing _E_ and in
dropping down onto the firing pin _C_. The flame from the exploded
primer then travels down to the powder in the shell in practically the
same way that it does in the American fuse, except that the magazine
chamber is located at _D_ and explodes through the impact fuse chamber.
The percussive arrangement for setting the shell off by impact is
slightly different from that in the American fuse, in that the primer
and firing pin are held apart by means of springs, the inertia of which
is overcome when the shell strikes an object.
=French Fuse.=--With the exception of a few minor details, the timing
fuses used in American, Russian, British, German, Japanese, etc.,
shrapnel shells are the same. The French timing fuse, however, as shown
by the diagram Fig. 5, operates on an entirely different principle. In
this fuse, the firing for the timing train is contained in a sealed
tube of pure tin and is wound spirally around the head of the fuse.
Inside of the head is the ignition arrangement. To set the timing part
of this fuse, it is placed in a fuse-setting machine attached to the
field gun and, by forcing down a handle on this device, a piercing
point is thrust through the outer cap of the fuse, penetrating to the
interior space of the head as shown at _A_. Upon the discharge of
the shell from the gun, the gas pressure forces firing pin _B_ back,
hitting the percussive primer _C_. This causes a flame which passes out
through the opening previously punched at _A_ and ignites the “rope”
powder fuse which is wound around the head of the fuse body. This type
of fuse is also provided with a fuse which sets off the shell by impact
should the timing fuse fail to work. The head of the fuse is covered
with a cap with holes for the piercing point, and the whole cap can
be shifted around for a short distance and set by the corrector scale
marked on the body, as shown in Fig. 1. A projection on the cap engages
a recess in the fuse-setting machine and provides for this movement.
[Illustration: Fig. 5. French Type of Combination Timing and Percussion
Fuse]
=Firing of Shrapnel.=--The accuracy with which a shrapnel can be
exploded in the air at any desired point is remarkable, considering
the number of variable quantities that enter into the construction of
the timing fuse and powder train, etc. The calculations necessary for
finding the correct setting on the timing ring involve, however, the
use of higher mathematics and are consequently not within the scope of
this treatise.
In Fig. 6, the timing ring used on the American fuse is shown. Here
it will be seen that the ring is provided with twenty-one graduations
corresponding to twenty-one seconds in the duration of flight of the
projectile. It will also be noticed that the spacing of the graduations
differs. The reason for this is found in the relation of the vents,
the positions of the lower timing train, the trajectory of the flying
missile, and the decrease of velocity.
[Illustration: Fig. 6. Diagram showing how Timing Ring on the American
Combination Timing and Percussion Fuse is laid out]
Diagram Fig. 7 shows in an interesting manner just how a shrapnel is
fired. The range is approximately obtained by panoramic sights or
other means, and a test shell fired, the point of explosion noted, and
the necessary corrections made. A table which has been worked out for
different distances is then used. In Fig. 7 the diagram shown pertains
to the American quick-firing field gun having a muzzle velocity of 1700
feet per second and the American shrapnel of 3-inch size. It will be
noted that at 2000 yards the terminal velocity of the shrapnel is 1038
feet per second and the time of flight for the projectile 4.75 seconds.
In other words, the timing train to explode the shrapnel at this point
would be set at _A_ in Fig. 6. The range of a 3-inch American shrapnel
is 6500 yards and at this point the terminal velocity is approximately
724 feet per second, the time of flight 21.92 seconds. The shrapnel,
when exploded, shoots out the bullets at an increased velocity or from
250 to 300 feet per second, covering an area of about 250 by 30 yards,
half the bullets falling on the first 50 yards of the beaten zone.
[Illustration: Fig. 7. Diagram Illustrating Path of a Shrapnel and the
Time of Explosion at Various Distances]
In manufacturing shrapnel shells, a test shell is taken from every 120
shells, which is actually fired out of a quick-firing gun into a bank
of sand. If the contour of the shell in the neighborhood of the powder
pocket is expanded during this test, the shell is discarded because of
the liability of tearing out the rifling grooves in the gun
=Propellants and Explosives used in Shrapnel and High-explosive
Shells.=--As has been previously explained, a shrapnel shell contains
three principal parts, _viz._, the projectile that carries the
destructive charge of lead bullets, the fuse that carries a detonating
arrangement for exploding the charge in the base of the projectile,
and the cartridge case that carries the powder charge used in
propelling the projectile out of the bore of the gun. A high-explosive
shell also comprises three principal parts, but the projectile,
instead of carrying a charge of bullets and black powder, is filled
with a high-explosive material, which, when detonated, bursts the body
of the projectile into small pieces that are thrown off with great
velocity and destructive effect. Shrapnel is used against troops in
the open field, whereas high-explosive shells, which may be either
of the ordinary or of the armor-piercing type, are used against
fortifications, etc
=Classification of Explosives.=--The explosives used in shrapnel and
high-explosive shells may be divided into three general classes: 1.
Progressive or propelling explosives--known as “low” explosives. 2.
Detonating or disruptive explosives--known as “high” explosives. 3.
Detonators--known as “fulminates.” The first of these includes black
gun powder, smokeless powder, and black blasting powder. The second,
dynamite, nitroglycerine, gun cotton, etc. The third includes chiefly
fulminates and chlorates. In all classes of explosives, the effect
of the explosion is dependent upon the quantity of gas and the heat
developed per unit of weight and volume of the explosive, the rapidity
of the reaction, and the character of the confinement, if any, of the
explosive charge.
_Low Explosives._--For certain explosives, such as smokeless powder,
the explosive action does not differ in principle from the burning
of a piece of wood or other combustible material. The combustion is
very rapid, but is a surface action, progressing from layer to layer
until the entire grain is consumed. Such materials are known as “low”
explosives, although the power developed through the combustion of
a unit weight may be very great. The progressive emission of gas
from a low explosive, such as burning gun powder, produces a pushing
effect upon a projectile without unduly straining the gun, whereas
the sudden conversion of an equal weight of a high explosive, such
as nitroglycerine, into gas, would develop such high pressures as to
rupture the gun.
_High Explosives._--In high explosives, such as nitroglycerine, gun
cotton, picric acid, etc., the progress of the explosive reaction
is not by burning from layer to layer, but, instead, consists of an
initial breaking up of the molecules, giving rise to an explosive wave,
which is transmitted with great velocity in all directions throughout
the mass, and causes it to be converted almost instantly into a gas.
The velocity of this explosive wave has been determined, for some
materials, to be more than 20,000 feet, or approximately four miles,
per second.
_Detonators or Fulminates._--The action of fulminates is much more
powerful than either the low or high explosives described. They can
be readily detonated by slight shock or by the application of heat,
and are used in primers, for setting off the propelling charge in a
cartridge case, and in fuses, either of the plain percussion or of
the combination time and percussion types. The most common fulminate
is made by dissolving mercury in strong nitric acid and then pouring
the solution into alcohol. After an apparently violent reaction, a
mass of fine, gray crystals of fulminate of mercury is produced. The
crystalline powder thus produced is washed with water to free it from
acid and is then mixed with glass ground to a fine powder. Because of
its extreme sensitiveness to heat produced by the slightest friction,
it is usually kept soaked in water or alcohol until needed
=Manufacture of Black Powder.=--Black powder, because of its “pushing”
effect when exploded, is used extensively as a base charge for shrapnel
shells in expelling the bullets from the projectile. It comprises
three principal elements in about the following proportions: 75
parts of saltpeter, 15 parts of charcoal, and 10 parts of sulphur.
These ingredients must be absolutely free from impurities and, in
manufacturing, great care is taken in refining the saltpeter and
sulphur, and in burning the charcoal, to prevent the introduction
of any foreign substances. After purification, the ingredients are
carefully weighed in the proper proportions and mixed for about 5
minutes in a revolving drum provided with mixing arms. The mixed
charge is now ground for several hours, the charge being moistened
occasionally with distilled water, the resulting mixture being what
is called a “milk cake.” It is then reduced to fine meal in a machine
having Tobin bronze or gun-metal rollers, after which it is compressed
under hydraulic pressure.
The next operation comprises the granulating of the powder, which is
done in a strong Tobin bronze or gun-metal framework carrying two pairs
of toothed and two pairs of plain Tobin bronze or gun-metal rollers.
The “cake” is cut into pieces by these rollers and falls on screens
which sift it into grains of the required size. The grains are then
separated from the dust in a revolving screen, and the high polish or
glaze is produced by putting the powder into drums or glazing barrels,
which revolve constantly for several hours. Graphite is generally used
to provide the glazing effect. The powder is now dried in a stove
heated by steam pipes, and is spread upon canvas trays placed on shelves
=Manufacture of Smokeless Powder.=--Smokeless powder, which is used
in various forms in cartridge cases, was discovered in 1846 by a
German chemist Schoenbein. The chief ingredient of smokeless powder
is cotton. The portion of cotton used is generally the short fiber.
The first attempts to produce gun cotton were unsatisfactory, and
several very serious explosions occurred. Many of the difficulties in
its manufacture were overcome by an Austrian, von Lenk. Still further
progress was made by a Swedish engineer, Alfred Nobel, and the improved
explosive was patented in 1888 under the name of “ballistite.” One of
the principal smokeless powders is known as “cordite”, this name being
derived from the cord-like form it assumes in manufacture. The first
compositions of cordite were: 58 per cent of nitroglycerine; 37 per
cent of gun cotton; and 5 per cent of mineral jelly. This composition,
after considerable use, was found to have a slight deteriorating effect
on the bore of the gun, and after ten years’ use was modified to the
following proportions: 30 per cent of nitroglycerine; 65 per cent of
gun cotton; and 5 per cent of mineral jelly.
The brand of smokeless powder used most extensively as a propelling
charge in shrapnel or high-explosive shells is known as nitrocellulose,
and, as is common with cordite, the base of this is cotton, as
previously explained. It is manufactured as follows: After bleaching
and purifying, the cotton is run through a picker which opens up the
fibers and breaks up any lumps. It is then thoroughly dried and is
ready for nitration. The most generally used method of nitration is
to put the cotton into a large vessel filled with a mixture of nitric
and sulphuric acids. The sulphuric acid absorbs the water developed
in the process of nitration, which would otherwise too greatly dilute
the nitric acid. After a few minutes’ immersion, the pot is rapidly
rotated by power, and the acid permitted to escape. Following this,
the nitrated cotton is washed for a short time and then removed from
the nitrator or pot and repeatedly washed or boiled to remove all
traces of free acid. As the keeping qualities of the nitrated cotton
are dependent upon the thoroughness with which it is purified, the
specifications for powder for the United States army and navy require
that the nitrocellulose shall be given at least five boilings at this
stage of the manufacture, with a change of water after each boiling,
the total time of boiling being forty hours. Following this preliminary
purification, the nitrocellulose is cut up into shorter lengths, by
being rapidly run between cylinders carrying revolving knives. This
operation--known as “pulping”--is necessary because of the difficulty
experienced in removing the free acid, unless the fibers are cut up
into short lengths.
After pulping, the nitrocellulose is given six more boilings, with a
change of water after each, followed by ten cold water washings. The
material is now known as gun cotton or pyrocellulose. Previous to
adding the solvent, this must be free from water. This is generally
accomplished in a circular wringer, and in addition by compressing
the pyrocellulose into solid blocks. Alcohol is forced through the
compressed mass. Ether is then added to the pyrocellulose already
impregnated with alcohol, the relative proportions being two parts,
by volume, of ether to one part of alcohol. After the ether has been
thoroughly incorporated in a kneading machine, the material is placed
in a hydraulic press and formed into cylindrical blocks about 10 inches
in diameter and 15 inches long. It is then transferred to a finishing
press where it is again forced through dies and comes out in the form
of long strips or rods, which are cut into pieces of the length and
widths required. It is in this finishing process that the various
governments differ in their methods of manufacture. The United States
Government uses a short perforated circular block, whereas the French
use flat sticks about 0.0195 inch thick by ¹⁄₂ inch wide. Two lengths
or rows of these sticks are arranged in the cartridge case. The cut
up pieces are subjected to a drying process which removes nearly all
the solvent and leaves the material in a suitable condition for use.
The drying process is a lengthy one, amounting to as much as four or
five months for powder in large pieces. Upon completion, the powder is
blended and packed in airtight boxes
=Manufacture of High Explosives.=--The explosive charges used in
high-explosive shells are known by various trade names, such as:
emmensite, lyddite, melinite, maximite, nitrobenzole, nitronaphthalene,
shimose, trinitrotoluol, turpenite, etc. The base of such explosives as
emmensite, maximite, lyddite, melinite, and shimose, is picric acid,
which is secured from coal tar, subjected to fractional distillation.
The liquid which comes off when this is raised to a temperature of
150 degrees C. is called “light” oil, and when these light oils
have been again distilled, the next fraction or “middle” oil yields
phenol or carbolic acid. This substance when nitrated gives off
picric acid. Experiments with lyddite shells showed their behavior
to be very erratic, some exploding with great effect, while others
gave disappointing results. This was due to the fact that picric
acid requires a powerful detonator to obtain the highest explosive
effect. The use of such a detonator, however, is dangerous, and
extensive experiments have brought forth a new high explosive known as
trinitrotoluol--generally termed T.N.T. Although the explosive force of
trinitrotoluol is slightly less than that of picric acid, the pressure
of the latter being 135,820 pounds per square inch as against 119,000
pounds for trinitrotoluol, its advantages more than compensate for the
difference.
Trinitrotoluol is obtained by the nitration of toluene, contained in
the crude benzol distilled from coal tar and washed out from coal gas.
The crude benzol contains roughly:
Per cent
Benzine 50
Toluene 36
Xylene 11
Other substances 3
Toluene to be used for the manufacture of trinitrotoluol should be a
clear water-like liquid, free from suspended solid matter, and having a
specific gravity of not less than 0.868, nor more than 0.870, at 15.5
degrees C. Trinitrotoluol when pure has no odor and is a yellowish
crystalline powder which darkens slightly with age. It cannot be
exploded by flame or strong percussion, and a rifle bullet may be
fired through it without any effect. When heated to 180 degrees C., it
ignites and burns with a heavy black smoke; but when detonated by a
fulminate of mercury detonator, it explodes with great violence, giving
off a black smoke. Shells containing this explosive, first used on the
western battle front, were given such names as “coal boxes,” “Jack
Johnsons,” “Black Marias,” etc., by the allies.
The Russians and Austrians use a high explosive known as ammonal in
which 12 to 15 per cent of trinitrotoluol is mixed with an oxidizing
compound, ammonium nitrate, a small amount of aluminum powder, and a
trace of charcoal. This high explosive gives somewhat better results
than plain trinitrotoluol, but has the one disadvantage of easily
collecting moisture, and consequently must be made up in airtight
cartridges. The British are now using an improved compound of this
character, which is so prepared that trouble is not experienced with
the collection of moisture.