Improvements in the Construction of Ordnance.
Year: 1893

page_text: Date of Application, 28th Apr., 1893
Complete Specification Left, 29th Jan., 1894-Accepted, 3rd Mar., 1894..
PROVISIONAL SPECIFICATION.
Improvements in the Construction of Ordnance.
I WILLIAM HOPE of the Army and Navy Club Pall Mall in the County of
London Lieutenant Colonel V.C. do hereby declare the nature of this invention to
be as follows:-
The structural weakness, errors in design, and unreliability, of our guns have
become, year by year, more and more painfully apparent, and their cost is Bo
oppressive that it is quite impossible to have enough of them for the efficient
defence of the Empire.
It is therefore obvious, that something must be done to make our guns stronger,
and; if possible, cheaper.
One of the things which I have persistently denounced is the theoretical work on
which the designs of the guns are based. This is the mathematical investigation.
by the late Monsieur Lamé of the theoretical behaviour of a thick hollow cylinder
exposed to a uniform fluid pressure. But firstly the pressure is not uniform in the.
powder chambers of our guns, owing to the way in which they are loaded, and in
which the powder ignited. Secondly, owing to the ingenious but erroneous, method
of imparting rotation to the projectile, by means of a projecting band of copper,
the gun is converted into an instantaneous planing machine which throws upon the
inner tube round the powder chamber a tremendous jerk. Thirdly the friction of
the projectile in its passage up the bore of the gun puts on a severe longitudinal
pull or stress on the whole length of the tube. And fourthly the rifling of the gun
forcing the projectile to rotate, subjects it to a very considerable torsion. The fact
that this torsion has actually enabled the projectile, in the case of some of the
that
largest and heaviest guns, made without trunnions, to partially rotate the gun,
is to perceptibly move it, in spite of the grip of the steel straps fastening it down,
is a measure, and a proof of the reality of this torsion.
Now (1) the nonuniformity of the pressure, (2) the jerk of the instantaneous
planing machine, (3) the longitudinal pull, and (4) the torsion, completely upset
Monsieur Lamé's results, or rather show that however true theoretically, in the case
supposed, namely, a thick hollow cylinder exposed to a uniform pressure of freely'
escaping gas, they are quite inapplicable to rifled guns projecting heavy tightly.
fitting elongated projectiles.
Then again supposing that these calculations were in any way applicable to guns,
and that a gun were correctly built up according to these calculations, they are
upset once more the moment firing commences by the rapid, and great increase, of
temperature which starting from the interior, swells the inner parts, of the gun
first and puts an immense additional Stress on the outer parts never estimated or
allowed for. Again when a cylinder is shrunk on to a gun the loss of heat by
abstraction, added to radiation, shrinks the ends of the cylinder first, and compels
them to grip and become rigid and immoveable, while the rest of the cylinder is
still, not only distended circumferentially, but also longitudinally. But the two
ends having already gripped, when the body of the cylinder cooled down, it is
exposed to a dangerous longitudinal tension, and also forced to grip harder than
was intended.
But the finished gun, when cold, being filled with such dangerous, and unknown
tensions and crushing stresses, when it is violently and suddenly heated from the
inside by heavy firing, a farther series of still more dangerous and still more
unknown tensions and crushing stresses is set up, and when we consider that a gun

page_text: so misconstructed is then subjected to conditions 1, 2, 3 and 4, supra, the wonder
is, not that one such gun occasionally bursts, or opens its joints, or..bends, or
otherwise fails, but that such a gun is ever fired rapidly for several rounds without
bursting.
Another thing that I have denounced and laughed at is tempering gun cylinders
in oil. What is tempering in oil? Why chilling! in other words altering the
crystallisation of the steel. But the "chill" only penetrates about half an inch.
Now take a cylinder whose walls are 4 inches thick. The "chill" deducted from
the inner and outer surfaces would leave 3 inches untouched as regards the size
and formation of the crystals. But when the cylinder is dipped in the oil, the two
surfaces become very rapidly rigid; in other words the inner and outer surfaces, and
the metal behind them for a thickness of half an inch, are converted into two rigid
concentric circles, which, being rigid, and concentric, cannot approach each other.
Yet the 3 inches of metal in between is still swollen by the previous heating, and
as the oil gradually abstracts this heat, this internal metal makes a violent effort to
compel the two rigid and concentric circles to approach each other. The result is
frightful internal strains which have been known to split a cylinder from end to
end. These strains must also frequently cause internal and unsuspected flaws, in
other words minute ruptures, ready to extend on small provocation. But what
becomes cf. the "temper" sought to be put into steel guns, when they are fired,?
Of course sooner or later it vanishes as the guns heat.
This brief sketch shows, I think, that our present system of constructing guns,
is thoroughly unsound and quite indefensible.
I showed a copy of my report on certain Dutch experiments with bronze guns
lined with wrought iron tubes and rifled to my old friend the late Major Sir William
Palliser, with whom I had been at the same college at Cambridge. He was very
much struck with the results obtained, said that he was contemplating some
experiments in lining cast iron smooth bore guns with wrought iron tubes, which he
thought would strengthen them in a better and safer way than by banding them
with wrought iron hoops outside, as it would permit of the bore being reduced and
these Dutch experiments confirmed him in his view. He also said that he saw
how the tubes might be prevented starting forward and explained his idea of a
screw washer gripping both gun and tube at the muzzle. This system he tried.
successfully, and it was adopted by the War Office for the conversion of muzzle
loading smooth bore cast iron guns into rifled guns.
But the success of these converted guns far exceeded Major Palliser's
expectations. There were eventually 2,500 of them converted, chiefly 32 prs.
and when converted they fired projectiles of double the weight of the spherical
solid shot, and with the full charge of 8 lbs. of powder. That powder too
was "L.G." and "R.L.G.," powders of extreme violence which the makers of
the modern steel guns would not dare to use for a single round. Nevertheless for
a period of very nearly 20 years there were more rounds fired out of these cheap
converted cast iron guns, than out of the whole of our other rifled heavy guns,
of all sorts and sizes put together, yet not one of these Palliser guns burst.
This astonishing result could in no way be explained. Sir William Palliser
and I discussed the reason of this extraordinary and unlooked for endurance many
scores of times, trying to discover the law governing it, so as to be able to make a
proper calculation, for he had been obliged to design his guns more or less
empirically which is never satisfactory, and in such a matter disagreeable because
dangerous. But our utmost efforts, continued down to the time of his death,
altogether failed to penetrate the mystery.
For several years I applied myself to the puzzle, sometimes keeping my mind
on it, and on it alone, and sometimes also considering the alterations which would
be required in the details of construction to adapt it to breech loading guns. In.
the Palliser gun the enlarged bore in the cast iron gun was of course a perfectly:
parallel bore, as was also the bore of the muzzle loading tube which fitted into it,
for the guns were not "chambered." But Hope guns being chambered on a slight

page_text: cone with the double object of holding more powder, and of preventing the empty
metallic cartridge case clinging to the walls of the chamber, when the ejectors are
set in motion to throw it out, it would scarcely be possible to make the bore in
the gun a parallel hore for to do so would necessitate the tube being of undue
thickness at the muzzle end, or unduly thin round the powder chamber or both.
Then came the questions how should the tube be fixed into the gun at the breech
end, or should it be fixed at that end at all?
Here were new problems of evident and great importance, making it more
dangerous than ever to proceed empirically and therefore, I tried harder than ever
to unravel the mystery of the strength of the Palliser guns, and at last my patience
and perseverance were rewarded by making the desired discovery, and I was farther
gratified by seeing, that it was only in a breechloading gun that the system could
be developed properly, and its full advantage obtained.
Sir William Palliser's object being the utilization of our old cast iron guns,
the material for his guns-I mean the gun proper-was. of course not an open
question; and at the date of his experiments, the only material ready to his hand
for the tubes was wrought iron coils. But it is obvious that cast steel would be
superior to cast iron, and, as I shall presently show the higher the grade of the
cast-steel, the more suitable it is for the purpose in one alternative mode of con-
struction. Therefore the gun proper may, to start with have a tensile strength
of 5 and even 6 times the tensile strength of the cast-iron in the Palliser
converted guns.
Then for the tubes, or inner guns, it is obvious that cast, or
forged, steel of suitable tensile strength would be greatly superior to wrought iron.
But some of the new bronzes such as, "Delta" metal, "Heepertz" metal, phosphor
bronze, manganese bronze, aluminium bronze, &c. &c. &c. would all be very suit-
able for the outer gun though perhaps all having too low a melting point for the
inner gun.
But now for the solution of the mysterious strength of the Palliser converted
guns. The explanation is exceedingly simple, and it is also one of the very
prettiest things in applied mechanics, and metallurgy.
can
A tube of no matter what size, proportion, or material, cannot be circum-
ferentially distended at any point, or points, or for any length, without being
proportionally reduced in length. Without going into mathematics, any one.
satisfy himself of this axiom by a very easy and simple experiment with an india
rubber tube of a few inches in length, and half an inch, or an inch, in diameter.
When a Palliser gun is fired therefore, the violent powder suddenly enflamed in
the powder chamber presses the breech of the tube violently against the breech of
the gun, and it also makes a prodigious effort to circumferentially distend the tube
round the powder chamber. But it cannot do this because, the tube, being fixed
in the muzzle of the gun by the screw washer, cannot shorten itself by even as
much as a hair's breadth. Consequently scarcely any circumferential tensile stress
is put upon the gun proper, the cast-iron of which is so ill adapted to withstand
that kind of stress, but a great part of the circumferential stress on the tube is
converted into a longitudinal pull, and distributed, instantly, along the whole
length of the tube, while it is applied to the gun in the form of a crushing stress,
also distributed along the whole length of the gun, by the tremendous efforts of
the tube to shorten itself, which efforts, through the medium of the screw washer
are in their turn converted from a longitudinal pull in the tube to a crushing stress
in the gun, the- very stress which cast-iron, or high grades of cast steel can best
resist.
By this means not only are those stresses set up in the inner and outer metals
which those metals are precisely best adapted to resist, but they are distributed,
instantly, along the whole length of the gun, and the entire resisting force of the
whole length of the gun is exerted the very moment that the flash enters the
powder chamber. No wonder that the Palliser guns bad such phenomenal
endurance!

page_text: =
This general system of construction is obviously the safest and most durable,
as well as the cheapest.
:
Now let us consider its application to a breech loading gun with an enlarged
powder chamber.
The tube, or inner gun, of a gun of this construction should obviously not be
parallel in its outside lines, because if so made, it would be either unduly thick at
the muzzle, or unduly thin round the powder chamber. It is not absolutely
imperative that such a tube should be fixed into the gun at the breech end,
especially if the breech block be of the Krupp principle" going through the two
side walls of the gun, but I strongly advise the tube being securely fixed in the
'gun at both ends. Moreover it is only by this means that the full advantage of
the system can be obtained because such a tube, when the powder gas is trying to
distend it circumferentially, would make a tremendous effort to shorten itself, and
in doing so would seek to pull the two ends of the gun proper closer together;
in other words, the whole of the longitudinal pull on the tube would be converted
into crushing stress in the gun, whereas in a muzzle-loader, it is only a portion of
the longitudinal pull on the tube which is converted into crushing stress in the
*gun.
.'
In the case of the Palliser converted guns the coiled wrought iron tubes,
pressed in from the muzzle end, did not fit with any mathematical precision,
moreover the metal being coiled was not as solid as homogeneous metal. Conse-
quently there was a certain room for both consolidation of the metal, and
circumferential dilatation, and this would secure a permanent longitudinal pull
being put on the tube by the few trial rounds which were always fired, not indeed
with that object in view, which was not thought of, but with the view of con-
solidating the coils, and making them fit tight, and also of pressing the solid breech
of the tube home against the breech of the gun.
But it must be remembered that wrought iron is plastic, in other words it can
be deformed with comparative ease, and so it is quite possible, that in the case of
all, or many, of the Palliser guns, what was originally a longitudinal pull upon
the muzzle of the tube communicating a longitudinal crushing stress to the gun,
may have, by degrees, become changed into a longitudinal thrust on the muzzle-
end, as it always had been on the breech-end, communicating a longitudinal tensile
stress along the whole length of the outer gun.
This would also be the case in a breech-loader, if the inner gun stopped at the
front face of the breech-block. Such an arrangement would not be a bad one, but,
as I said before, I recommend the alternative arrangement of the inner gun running
'through the entire length of the gun, and being securely fastened to the outer gun
at both ends, and to make this union as perfect as possible, and to prevent jar, a
cementitious process may be applied to the metal at each end. The outer gun
may be, more or less, warmed before the tube is introduced, and, to further facilitate
the introduction, the metal of the inner gun should be longer at both ends than
the outer gun. It will also be desirable to introduce the inner gun or tube-before
it is bored..
It is obvious that with homogeneous tubes a new condition of things arises, for
assuming the tube to fit the gun with a theoretically perfect fit, there could be no
circumferential dilatation, and as the walls of the tube are already solid, all that
could happen in such a case would be an effort at dilatation on the part of the tube,
which, being prevented by the gun, would be converted into a molecular movement
setting up a longitudinal thrust, instead of a longitudinal pull, against the metal of
the outer gun. This would equally be a distribution and conversion of the original
local stress in the metal round the powder chamber, and distribution and conversion
mean of course diminution of local stress. In other words the metal along the
whole length of the gun is brought up to the assistance of that round the powder
chamber. But to get the full benefit of the different and opposite qualities of
metal, the tube, in the case just suggested, should be of a high quality of steel, to

page_text: resist the thrust, which is really a crushing stress, and the outer gun should be of
a mild steel to resist the pull put on it by the thrust of the tube.
If however the tube is made to fit the gun loosely round the powder chamber,
and the steel of the tube be mild and untempered, the conditions of the Palliser
guns, when first fired, would be restored.
But it is possible that after a time repeated rounds might gradually set up a
molecular movement in the tube which would eventually convert this pull into a
thrust. The experiments which could alone determine such points as this are
beyond my means, therefore in their absence I. recommend that both tube anil
gun be made of a medium steel, well adapted to stand both tensile and crushing
stresses, say, a steel, whose tensile strength is of about 45 tons to the square inch,
and that a space be left round the powder chamber of the tube, between it and the
gun sufficiently large to put a pull on the tube, and sufficiently small to be well
within the elastic limit of the steel of the tube.
1
The tube of such a gun may be made of several different diameters externally,
each part of a given diameter being parallel in its outside lines, but I strongly
advocate the exterior of the tube being made on a long taper, if not throughout
its entire length, at all events outside the enlarged powder chamber. Then a
short length at each end must in any case be parallel in its outside lines, to admit
of being fixed into the gun proper, and this may be done either by screw washers,
or, as
greatly prefer and recommend, by being screwed direct into the gun. If
this is done, then, as the tube must be introduced from the rear, the male thread
of the muzzle secrew must be cut in the gun, and the female in the tube; while at
the breech end just the reverse must be done, and the male thread must be on the
tube, and the female thread in the gun.
1
The thickness of the tube should not be less than one third of the bore at any
point, and it may be more with advantage, say three quarters of the bore.....
The external form of the tube, may be one long taper, or a long taper outside
the powder chamber, beyond which the outside lines may be on a more gentle
taper or be parallel, and if the male thread of the muzzle screw is left standing
out on the muzzle, cut in an extra thickness of metal left on the tube for that
purpose, then the long parallel part between the muzzle screw and the taper
outside the powder chamber, should-as tbe bore of the gun must be large enough
to admit the outstanding male screw thread introduced from the rear-be covered
either with two thin half tubes, merely to fill up the air-space otherwise existing
between that part of the tube and the bore of the gun, or the outside of that part
of the tube may be more usefully covered with steel tape tightly wound round it..
If desired, a jacket may be put on outside the powder chamber, in that case the
jacket should carry the trunnions. Such a jacket should be put on from the rear,
and there ought to be a step, or shoulder in the gun and jacket through which to
communicate the recoil.
'
The metal of the tube may be made longer than the gun at either or both
ends, and it may be expanded and turned up in front or in rear of the gun, or
both, when it is intended that the powder gas shall put a pull on the tube, and a
compression or crushing stress on the gun.
The bore of the tube, or inner gun may be usefully covered by deposited
platinum which will effectually minimise the erosion by plugging up the pores of
the steel, and so preventing the gas catching hold of the roughnesses, and so
producing molecular disintegration.
3.
The outer surface of the tube, or inner gun and the inner surface or bore of
the gun proper may similarly be protected against corrosion by being.covered with
deposited nickel.
Dated this 28th day of April 1893.
CARPMAEL & Co.,
Agents

page_text: Improvements in the Construction of Ordnance.
I, WILLIAM HOPE, of the Army and Navy Club, Pall Mall, in the County of
London, Lieutenant Colonel, V.C., do hereby declare the nature of this invention
and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement :-
The structural weakness, errors in design, and unreliability, of our guns have
become, year by year, more and more painfully apparent, and their cost. is so
oppressive that it is quite impossible to have enough of them for the efficient defence
of the Empire.
:
It is therefore obvious that something must be done to make our guns stronger,
and, if possible, cheaper.
One of the things which I have persistently denounced is the theoretical work on
which the designs of the guns are based. This is the mathematical investigation by
the late Monsieur Lamé of the theoretical behaviour of a thick hollow cylinder
exposed to a uniform fluid pressure. But firstly the pressure is not uniform in the
powder chambers of our guns, owing to the way in which they are loaded and in
which the powder is ignited. Secondly, owing to the ingenious but erroneous
method of imparting rotation to the projectile, by means of a projecting band of
copper, the gun is converted into au instantaneous planing machine which throws
upon the inner tube round the powder chamber a tremendous jerk. Thirdly the
friction of the projectile in its passage up the bore of the gun puts on a severe
longitudinal pull or stress on the whole length of the tube. And fourthly the rifling
of the gun forcing the projectile to rotate, subjects it to a very considerable torsion.
The fact that this torsion has actually enabled the projectile in the case of some of
the largest and heaviest guns, made without trunnions, to partially rotate the gun,
that is to perceptibly move it, in spite of the grip of the steel straps fastening it
down, is a measure, and a proof, of the reality of this torsion.
Now (1) the nonuniformity of the pressure, (2) the jerk of the instantaneous
planing machine, (3) the longitudinal pull, and (4) the torsion, completely upset
Monsieur Lamé's results, or rather show that however true theoretically, in the
case supposed, namely, a thick hollow cylinder exposed to a uniform pressure of
freely escaping gas, they are quite inapplicable to rifled guns projecting heavy
tightly fitting elongated projectiles.
Then again supposing that these calculations were in any way applicable to guns,
and that a gun were correctly built up according to these calculations, they are
upset once more the moment firing commences by the rapid, and great increase, of
temperature which, starting from the interior, swells the inner parts of the gun
first, and puts an immense additional stress on the outer parts, never estimated or
allowed for. Again, when a cylinder is shrunk on to a gun the loss of heat by
abstraction, added to radiation, shrinks the ends of the cylinder first, and compels
them to grip and become rigid and immoveable, while the rest of the cylinder is
still, not only distended circumferentially, but also longitudinally. But the two
ends having already gripped, when the body of the cylinder is cooled down, it is
exposed to a dangerous longitudinal tension, and also forced to grip harder than was
intended.
But the finished gun, when cold, being filled with such dangerous, and unknown
tensions and crushing stresses, when it is violently and suddenly heated from the
inside by heavy firing, a farther series of still more dangerous and still more
unknown tensions and crushing stresses is set up, and when we consider that a gun
so misconstructed is then subjected to conditions 1, 2, 3 and 4, supra, the wonder is,
not that one such gun occasionally bursts or opens its joints, or bends, or otherwise
fails, but that such a gun is ever fired rapidly for several rounds without bursting.

page_text: Another thing that I have denounced and laughed at is tempering gun cylinders
in oil. What is tempering in oil? Why chilling! In other words altering the
crystallisation of the steel. But the "chill" only penetrates about half an inch.
Now take a cylinder whose walls are four inches thick. The "chill deducted
from the inner and outer surfaces would leave 3 inches untouched as regards the
size and formation of the crystals. But when the cylinder is dipped in the oil, the
two surfaces become very rapidly. rigid; in other words the inner and outer
surfaces, and the metal behind them for a thickness of half an inch, are converted
into two rigid concentric circles, which, being rigid and concentric, cannot approach
each other. Yet the 3 inches of metal in between is still swollen by the previous
heating, and as the oil gradually abstracts this heat, this internal metal makes a
violent effort to compel the two rigid and concentric circles to approach each other.
The result is frightful internal strains which have been known to split a cylinder
from end to end. These strains must also frequently cause internal and unsuspected
flaws, in other words, minute ruptures, ready to extend on small provocation. But
what becomes of the "temper" sought to be put into steel guns when they are:
fired ? Of course sooner or later it vanishes as the guns heat.
This brief sketch shows, I think, that our present system of constructing guns is.
thoroughly unsound and quite indefensible.
I showed a copy of my report on certain Dutch experiments with bronze guns
lined with wrought iron tubes and rifled, to my old friend the late Major Sir William
Palliser, with whom I had been at the same college at Cambridge. He was very.
much struck with the results obtained, said that he was contemplating some
experiments in lining cast iron smooth bore guns with wrought iron tubes which he
thought would strengthen them in a better and safer way than by bauding them
with wrought iron hoops outside, as it would permit of the bore being reduced and
these Dutch experiments confirmed him in his view. He also said that he saw how
the tubes might be prevented starting forward and explained his idea of a screw
washer gripping both gun and tube at the muzzle. This system he tried successfully
and it was adopted by the War Office for the conversion of muzzle loading smooth.
bore cast iron guns into rifled guns.
But the success of these converted guns far exceeded Major Palliser's.
expectations. There were eventually 2,500 of them converted, chiefly 32 prs. and
when converted they fired projectiles of double the weight of the spherical solid.
shot, and with the full charge of 8 lbs. of powder. That powder too was "L.G."
and "R.L.G.," powders of extreme violence which the makers of the modern steel.
guns would not dare to use for a single round. Nevertheless for a period of very
nearly 20 years there were more rounds fired out of these cheap converted cast iron
guns, than out of the whole of our other rifled heavy guns of all sorts and sizes put.
together, yet not one of these Palliser guns burst.
This astonishing result could in no way be explained. Sir William Palliser and.
I discussed the reason of this extraordinary and unlooked for endurance many.
scores of times, trying to discover the law governing it, so as to be able to make a
proper calculation, for he had been obliged to design his guns more or less.
empirically, which is never satisfactory, and in such a matter disagreeable because
dangerous. But our utmost efforts, continued down to the time of his death,
altogether failed to penetrate the mystery.
For several years I applied myself to the puzzle, sometimes keeping my mind on
it, and on it alone, and sometimes also considering the alterations which would be
required in the details of construction to adapt it to breech loading guns.. In the
Palliser gun the enlarged bore in the cast iron gun was of course a perfectly
parallel bore, as was also the bore of the muzzle loading tube which fitted into it,
for the guns were not chambered. But Hope guns being chambered on a slight
cone with the double object of holding more powder, and of preventing the empty
metallic cartridge case clinging to the walls of the chamber, when the ejectors are
set in motion to throw it out, it would scarcely be possible to make the bore in the
gun a parallel bore, for to do so would necessitate the tube being of undue thickness

page_text: at the muzzle end, or unduly thin round the powder chamber, or both. Then came
the questions how should the tube be fixed into the gun at the breech end, or
should it be fixed at that end at all.
3
Here were new problems of evident and great importance, making it more
dangerous than ever to proceed empirically, and therefore I tried harder than ever
to unravel the mystery of the strength of the Palliser guns, and at last my patience
and perseverance were rewarded by making the desired discovery, and I was
further gratified by seeing that it was only in a breechloading gun that the system
could be developed properly, and its full advantage obtained.
Sir William Palliser's object being. the utilization of our old cast iron guns, the
material for his guns, I mean the gun proper, was of course, not an open question
and at the date of his experiments, the only material, ready to his hand for the
tubes was wrought iron coils. But it is obvious that cast steel would be superior
to cast iron and as I shall presently show the higher the grade of the cast steel,
the more suitable it is for the purpose in one alternative mode of construction.
Therefore the gun proper may to start with have a tensile strength of 5 and
even 6 times the tensile strength of the cast iron in the Palliser converted guns.
Then for the tubes, or inner guns, it is obvious that cast, or forged, steel of suitable
tensile strength would be greatly superior to wrought iron. But some of the new
bronzes such as "Delta" metal, "Heepertz" metal, phosphor bronze, manganese
bronze, aluminium bronze, &c., &c., &c., would all be very suitable for the outer
gun though perhaps all having too low a melting point for the inner gun.
.
But now for the solution of the mysterious strength of the Palliser convertel
guns. The explanation is exceedingly simple, and it is also one of the very
prettiest things in applied mechanics, and metallurgy.
A tube of no matter what size, proportion, or material, cannot be circumferentially
distended at any point, or points, or for any length without being proportionally
reduced in length. Without going into mathematics, any one can satisfy himself of
this axiom by a very easy and simple experiment with an india rubber tube of a
few inches in length, and halt an inch, or an inch, in diameter. When a Palliser
gun is fired therefore, the violent powder suddenly enflamed in the powder chamber
presses the breech of the tube violently against the breech of the gun, and it also
makes a prodigious effort to circumferentially distend the tube round the powder
chamber. But it cannot do this because the tube, being fixed in the muzzle of the
gun by the screw washer, cannot shorten itself by even as much as a hair's
breadth. Consequently scarcely any circumferential tensile stress is put upon the
gun proper, the cast-iron of which is. so ill adapted to withstand that kind of stress;
but a great part of the circumferential stress on the tube is converted into a
longitudinal pull, and distributed, instantly, along the whole length of the tube,
while it is applied to the gun in the form of a crushing stress, also distributed along
the whole length of the gun, by the tremendous efforts of the tube to shorten
itself, which efforts, through the medium of the screw washer are in their turn
converted from a longitudinal pull in the tube to a crushing stress in the gun, the
very stress which cast-iron, or high grades of cast steel can best resist..
By this means not only are those stresses, set up in the inner and outer metals
which those metals are precisely best adapted to resist, but they are distributed,
instantly, along the whole length of the gun, and the entire resisting force of the
whole length of the gun is exerted the very moment that the flash enters the
powder chamber. No wonder that the. Palliser guns had such phenomenal
endurance !
This general system of construction is obviously the safest and most durable, as
well as the cheapest.
Now let us consider its application to a breech loading gun with an enlarged
powder chamber.
The tube, or inner gun, of a gun of this construction should obviously not be
parallel in its outside lines, because if 20 made, it would be either unduly thick at
the muzzle, or unduly thin round the powder chamber. It is not absolutely

page_text: imperative that such a tube should be fixed into the gun at the breech end,
especially if the breech block be of the Krupp principle going through the two
side walls of the gun, but I strongly advise the tube being securely fixed in the
gun at both ends. Moreover it is only by this means that the full advantage of
the system can be obtained because such a tube, when the powder gas is trying to
distend it circumferentially, would make a tremendous effort to shorten itself, and
in doing so would seek to pull the two ends of the gun proper closer together; in
other words, the whole of the longitudinal pull on the tube would be converted into
crushing stress in the gun, whereas in a muzzle-loader, it is only a portion of the
longitudinal pull on the tube which is converted into crushing stress in the gun.
In the case of the Palliser converted guns the coiled wrought iron tubes, pressed
in from the muzzle end,' did not fit with any mathematical precision, moreover the
metal being coiled was not as solid as homogeneous metal. Consequently there
was a certain room for both consolidation of the metal, and circumferential
dilatation, and this would secure a permanent longitudinal pull being put on the
tube by the few trial rounds which were always fired, not indeed with that object
in view, which was not thought of, but with the view of consolidating the coils, and
making them fit tight, and also of pressing the solid breech of the tube home
against the breech of the gun.
But it must be remembered that wrought iron is plastic, in other words it can be
deformed with comparative ease, and so it is quite possible, that in the case of all,
or any, of the Palliser guns, what was originally a longitudinal pull upon the
muzzle of the tube communicating a longitudinal crushing stress to the gun, may
have, by degrees, become changed into a longitudinal thrust on the muzzle end, as
it always had been on the breech end, communicating a longitudinal tensile stress
along the whole length of the outer gun.
This would also be the case in a breech-loader, if the inner gun stopped at the
front face of the breech-block. Such an arrangement would not be a bad one, but,
as I said before I recommend the alternative arrangement of the inner gun running
through the entire length of the gun, and being securely fastened to the outer gun
at both ends, and to make this union as perfect as possible, and to prevent jar; a
cementitious process may be applied to the metal at each end. The outer gun may
be, more or less, warmed before the tube is introduced, and, to further facilitate
the introduction, the metal of the inner gun should be longer at both ends than the
outer gun. It will also be desirable to introduce the inner gun or tube before it
is bored.
It is obvious that with homogeneous tubes a new condition of things arises, for
assuming the tube to fit the gun with a theoretically perfect fit, there could be no
circumferential dilatation, and as the walls of the tube are already solid, all that
could happen in such a case would be an effort at dilatation on the part of the tube,
which, being prevented by the gun, would be converted into a molecular movement
setting up a longitudinal thrust, instead of a longitudinal pull, against the metal of
the outer gun. This would equally be a distribution and conversion of the original
local stress in the metal round the powder chamber, and distribution and conversion
mean of course diminution of local stress. In other words the metal along the
whole length of the gun is brought up to the assistance of that round the powder
chamber. But to get the full benefit of the different and opposite qualities of
metal, the tube, in the case just suggested, should be of a high quality of steel, to
resist the thrust, which is really a crushing stress, and the outer gun should be of
a mild steel to resist the pull put on it by the thrust of the tube.
If however the tube is made to fit the gun loosely round the powder chamber,
and the steel of the tube be mild and untempered, the conditions of the Palliser
guns, when first fired, would be restored.
But it is possible that after a time repeated rounds might gradually set up a
molecular movement in the tube which would eventually convert this pull into a
thrust. The experiments which could alone determine such points as this are
·B'

page_text: beyond my means, therefore in their absence, I recommend that both tube and gun
be made of a medium steel, well adapted to stand both tensile and crushing
stresses, say, a steel whose tensile strength is of about 45 tons to the square inch,
and that a space be left round the powder chamber of the tube between it and the
gun sufficiently large to put a pull on the tube, and sufficiently small to be well
within the elastic limit of the steel of the tube.
The tube of such a gun may be made of several different diameters externally,
each part of a given diameter being parallel in its outside lines, but I strongly
advocate the exterior of the tube being made on a long taper, if not throughout
its entire length, at all events outside the enlarged powder chamber. Then a short
length at each end must in any case be parallel in its outside lines, to admit of
being fixed into the gun proper, and this may be done either by screw washers, or,
as I greatly prefer and recommend, by being screwed direct into the gun. If this
is done, then, as the tube must be introduced from the rear, the male thread of the
muzzle screw must be cut in the gun, and the female in the tube; while at the
breech end just the reverse must be done, and the male thread must be on the tube,
and the female thread in the gun.
The thickness of the tube should not be less than one third of the bore at any
point, and it may be more with advantage, say three quarters of the bore.
The external form of the tube, may be one long taper, or a long taper outside
the powder chamber, beyond which the outside lines may be on a more gentle
taper or be parallel, and if the male thread of the muzzle screw is left standing
out on the muzzle, cut in an extra thickness of metal left on the tube for that
purpose, then the long parallel part between the muzzle screw and the taper
outside the powder chamber should-as the bore of the gun must be large enough"
to admit the outstanding male screw thread introduced from the rear-be covered
either with two thin half tubes, merely to fill up the air-space otherwise existing
between that part of the tube and the bore of the gun, or the outside of that
part of the tube may be more usefully covered with steel tape tightly wound
round it.
If desired, a jacket may be put on outside the powder chamber, in that case the
jacket should carry the trunnions. Such a jacket should be put on from the rear,
and there ought to be a step, or shoulder in the gun and jacket through which to
communicate the recoil.
The metal of the tube may be made longer than the gun at either or both ends,"
and it may be expanded and turned up in front or in rear of the gun, or both,
when it is intended that the powder gas shall put a pull on the tube; and a
compression or crushing stress on the gun.
The bore of the tube, or inner gun may be usefully covered by deposited
platinum which will effectually minimise the erosion by plugging up the pores of
the steel, and so preventing the gas catching hold of the roughnesses and so
producing molecular disintegration.
The outer surface of the tube, or inner gun and the inner surface or bore of the
gun proper may similarly be protected against corrosion by being covered with
deposited nickel.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. The construction of ordnance with a view to convert, and distribute, the
dangerous local circumferential stress set up, round the powder chamber, when the
gun is fired into longitudinal stresses along the whole length of the gun.in
the various alternative methods fully explained hereinbefore.
2. The protection of the bores of the guns from erosion, by depositing platinum
in them, and so preventing or retarding and minimising the disintegration of the
molecules of steel by the powder, explosive, or gun-fuel gases.

page_text: 3. The protection against oxidation of the steel forming the inner and outer
parts of guns by depositing nickel on the inner and outer surfaces, or either
of them.
W. HOPE.