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Cornell University Library
UG409.G8 S38 1887
Gruson's chilled cast-iron armour.
3 1924 032 591 749
olin
GRUSON'S
Chilled
Cast- Iron
Armour.
BY
JULIUS VON
SCHUTZ,
Engineer of Grusonworks.
Translated
Commander
H.
into
H.
English
GRENFELL,
R.N.
gonion
PRINTED BY WHITEHEAD, MORRIS & LOWE,
9,
Fenchurch Street,
1887.
E.G.
PREFACE.
THE
question of National Defence
attention, not only in
'
made
of the experiments
behind
it,
occupying, at the present time, very great
An
also in America.
account
and the development attained from, the only system of
shown itself capable of resisting the attack of the heaviest
with,
armour which has hitherto
modern guns, and
is
England and her Colonies, but
of maintaining the protection given to the artillery
must necessarily be of
who
interest to all
and gunners placed
are professionally engaged on this
important subject.
Armour
is
acknowledged by
the leading authorities to be a necessity for the
all
defence of positions of such importance, that the safety of the State would be compromised
by
and a perusal of the following pages
their loss or destruction,
will
show that
of the tremendous attack capable of being delivered by the heavy guns
in
now
presence
carried
ships of war, no other system of armour offers a security approaching to that given
the
Gruson Chilled Cast-iron Armour.
great merit
Its
is
that
it
is
capable of meeting fully any projected increase in
may
the power of the attack, great as this
it
well
is
not
by
by
known
that the limit to
already been reached.
made
in
certain
penetrable armour
quarters
is
It
to
is
for this
forego
worse than none
from an admission of the
fact of
be,
whereas with other systems of armour
their resisting
the
powers
is
use
of
is
if
it
has
now being
armour altogether, inasmuch as
but military engineers
;
within sight,
reason that an endeavour
know
that this
is
merely
the failure of these other systems of being able to
compete with the guns, and that so long as weapons of the heaviest' nature are carried
afloat, similar guns must be employed for defence, and that in most cases to place
these guns behind efficient armour
is
the only
way
in
which
their full
and
effective
use can be ensured.
Based on
principles
which are technically sound, not only from a manufacturing,
Armour is the only system which
pari passu with the increased development of
the future the same guarantee of effective protection which
but also from a military point of view, the Gruson
has been able to maintain
artillery,
it
and which
offers in
its
position
has abundantly displayed in the past.
June, 1887.
CONTENTS.
PAttE
Introduction
Chapter
5
I.
Description
the
of
Chilled
types of
chief
Armour
Cast-iron
Minimum-Port
and
6
Carriages
I.
II.
III.
IV.
Protected Batteries
9
Armoured Turrets
Ii
Gruson's Hydraulic
Gruson's Hydraulic
Chapter
Minimum
Minimum
Port-Carriage, C/8o
13
Port-Carriage, C/84
16
II.
Firing Trials of Gruson
I.
Preliminary Trials
Gun
(8.3 in.)
Armour during
Chilled Iron
of
Tegel Range, in
at the
the years 1869
Armour Emplacement
the years 1869— 1871
a Chilled Iron
Embrasure Plate of same,
in February,
1.
Trial against the
2.
Trial against the Left Side Plate of same, in April, 1870
3.
Trial against the Right Side Plate of same, in June, 1870
4.
Trial against the dismounted
— 1874
for n
72-pounder
18
March and December,
1869
II.
21
Firing Trials
Roof Plate of same,
against Chilled Cast-iron
in October, 1871
for
...
...
Inland Fortification, in
27
Chilled Iron
Armour Turret
1.
Trial against the
2.
Trial against the second Chilled Iron
first
for
two 5.9
Tegel Range, March, 1873
in.
(15 cm) Guns,
27
,
Armour Turret
for
two
cm)
(15
5-9 in.
...
Guns, at the Tegel Range, May /July, 1874
Trial against the Port Plate of the second Chilled Iron Armour Turret for
two 5.9 in. (15 cm) Guns
Attack of the Port Plate with 193— 5.9 in. (15 cm) Long Shells
a.
...
A
25
26
the
— 1874
years 1873
at the
Armour
25
29
.
:
*.
,,
,,
c.
„
„
„
d.
—
,,
20— 6.7 in.
65— 5.9 in.
,,
Chilled Shells
,,
cm)
(is cm)
(17
,,
„
Iron Armour
32
...
32
...
32
Trial against the Left Side Plate of the second Chilled
C.
for two 5.9 in. (15 cm) Guns...
...
...
...
...
...
...
Trial against the Right Side Plate of the second Chilled Iron Armour Turret,
D.
Trial against the
two 5-9
for
Firing Trials
two 5.9
in.
in.
...
;..
..
(15 cm) Guns ...
Roof Plate of the second Chilled Iron
(15 cm)
...
Turret,
...
Armour
...
for
Coast
Defence,
in
the
years
1873/74
36
Port Plate of a Chilled Iron Armour Battery, for 8.3
Trial against the
2.
Trial against the second Port Plate of a Chilled Iron
first
cm) Guns on Gruson's Firing Ground
at
cm) Guns on Gruson's Firing Ground
(21
Buckau, 5th December, 1873
at
Armour
Battery, for 8.3
in.
...
Buckau, 27th July and 21st
38
Roof Plate of a Chilled Iron Armour Battery, for 8. 3
cm) Guns on Gruson's Firing Ground at Buckau, 21st August, 1874
Trial against the
(21
IV.
Conclusions
...
36
in,
August, 1874
3.
34
35
Armour,
1.
(21
33
Turret,
Guns
against Chilled Iron
31
...
B.
for
III.
10
.
...
...
...
..
.-
...
...
in.
...
42
...
44
3
Chapter
page
III.
Piringr Trials against Gruson Chilled Cast-iron Armour during the years 1882 to 1886...
I.
Firing Trials against Chilled Cast-iron Armour for Inland Fortifications during the
years 1882 to 1885
1.
46
Armour Turret for two 4. 7 in.
on Gruson's Firing Ground at Buckau, in
Trial against the side Plate of a Chilled Cast-iron
(12
cm) Guns 267
calibres long,
the months of December, 1882, to April, 1883
of a Chilled Ii-on
46
Armour Battery
2.
Trial against the Port
3.
Trial against the Port Plate of a Chilled Iron
4.
(15 cm) Guns, 23 calibres long, on Gruson's Firing Ground, l8th August, 1884
Trial against the Glacis Plate of a Chilled Iron Armour Turret for two 4.7 in.
(15
(12
1
cm) Guns, 23
Plate
calibres long,
cm) Guns, 23^
calibres
for eight 5.9 in.
on Gruson's Firing Ground, l6th
Armour Battery
July, 1883
on Gruson's Firing Ground
long,
...
54
for six J. 9 in.
at
60
Buckau,
5o
2th February, 1884
Armour Turret for two 4.7 in.
on Gruson's Firing Ground at Buckau,
Trial against the Port Plate of a Chilled Iron
5.
(12
cm) Guns, 23!
calibres long,
28th August, 1884
63
Armour Turret for two 4.7 in.
on Gruson's Firing Ground at Buckau,
Trial against the Side Plate of a Chilled
6.
(12
cm) Guns, 26 calibres long,
Iron
68
19th and 20th January, 1885
Conclusions
7.
II.
45
Firing Trials
...
...
...
against Chilled Cast-iron
...
...
Armour
...
for Coast
...
...
...
...
1883— 1886
1.
79
Trial against a
12
in.
(30.5
Armour Turret for two
on Gruson's Firing Ground at Buckau,
Glacis Plate of a Chilled Cast-iron
cm) Guns, 35
calibres long,
13th August, 1883
2.
3.
4.
5.
6.
79
Armour Turret for two 12 in.
on Gruson's Firing Ground at Buckau^
Trial against a Side Plate of a Chilled Cast-iron
(30.5 cm) Guns, 35 calibres long,
86
22nd October, 1883
Trial against a Half Roof Plate of a Chilled Cast-iron Armour Turret for two
12 in. (30.5 cm) Guns, 35 calibres long, on Gruson's Firing Ground at Buckau,
26th and 28th May, 1884
9S
102
Conclusions of the Dutch Committee respecting Trials, i
Trial against a Side Plate of a Chilled Iron Armour Turret for two 15.7 in.
...
107
(40 cm) Guns, 35 calibres long, on Firing Ground at Spezia, April, 1886
Second Trial against the Side Plate of a Chilled Iron Armour Turret for two
15.7 in. (40 cm) Guns, 35 calibres long, on Firing Ground at Spezia,
—
118
22nd June, 1886
Chapter
7^
Defence during the years
IV.
Comparative Analysis of the results obtained, and Conclusions
The proportion between the greatest and least thickness of the Armour
1.
2.
The proportion of the expanded length of the unprotected part of the Profile
Curve to the greatest expanded breadth of the Armour
The proportion of the vertical section to the Front Superficies of the Armour Plate
3.
The proportion of the energy of the attack to the weight of the Armour Plates...
4.
;.
Empirical Formula for designing Chilled Armour
6.
Conclusions
Table showing the principal data of the Firing Trials against Gruson Armour.
•
125
126
128
129
130
134
138
THE
extraordinary activity which in the present day
writer
displayed in
is
and developing the materials of war, imposes on every
improving
who undertakes
to describe its existing condition the necessity of
frequently correcting and supplementing the information he furnishes, so
great are the improvements
and progress made
course of
in the
each
year.
Under
in
the
title
of
"The Gruson
Chilled Iron Armour,"
and
Batteries,
and an account
We
submitted.
were able
means
superiority over the
by most authorities on the
trials
took place,
as,
of the firing tests to
published
which they had been
at that time to claim for the
armour a notable
which was then
of attack, a claim
we
Gruson Armoured Turrets
the year 1878 a short description of the
fully
admitted
During the following years no further
subject.
notwithstanding the increasing powers of the attack,
the data obtained remained an
amply
sufficient basis for
determining the
form and dimensions to be given to the armour.
In the meantime, however, great progress
construction
projectiles.
were
still
of
At
guns and manufacture
was made not only
powder, but also
of
in
in the
that
of
the close of the last decade Gruson's chilled iron projectiles
competing favourably with
steel shot, as the
problem
of
making
these latter as hard as glass, and at the same time tough and tenacious, had
not yet been solved.
As
far as
we know,
the credit of this improvement
due to the Krupp Works, whose armour-piercing
is
shells are in the present
day among the best made.
Although the
size of
increased, so long as the
guns and the weight
of
their
charges were
material of which their projectiles were
made
remained the same, the proportionate increase of thickness necessary to
be given to the armour could be calculated
projectiles
was introduced whose
effect
;
but when a
new
material for
on the armour was anticipated to
be much greater, but could not be with accuracy determined beforehand,
the resumption of firing trials
became an unavoidable
necessity.
—
[
6
]
This second series of trials began in the year 1882, and as they may
be considered to have reached a conclusion in the experiments which took
place at Spezia in April and June of 1886, the present time seems favorable
for
supplementing the
and
results,
earlier data
and conclusions with the most recent
establishing a comparison
for
between
We
them.
shall
repeat the earlier results so that, following a brief account of the chilled
armour and minimum-port carriages, a complete resume
of all the trials
will
be presented
which have taken place.
CHAPTER
Description
the
of
I.
chief types
Chilled
of
Cast-iron
Armour^ and Minimum-Fort Carriages.
toEFORE
'
proceeding to a description of the above-mentioned types, a
short notice of the material of Gruson's chilled iron
and
mode
its
of
manufacture may be desirable.
armour plating may be placed
All
Those which by virtue
(a.)
in
two
distinct
categories
:
of their hardness of surface deflect
shot which strike them.
Those
(i,)
into
which shot penetrate, but
in
which the
effect is
localized to the part struck.
The
first
comparatively hard armour was of
was given up on account of the brittleness
into pieces under the blpws of the shot.
For a number
armour,
means
Gruson produced
but the use of this
which shivered
was the only material used for
and by
his chilled cast-iron armour,
of a series of trials established the correctness of his system.
The Gruson
cast in
of years wrought-iron
until, in 1868,
steel,
of the plates,
chill,
to
chilled iron is
which
it
owes
its
a mixture of different blends of pig-iron,
hardness.
In accordance with the two chief qualities which he sought to obtain
in his metal,
each
of
Gruson chose two
which possessed one
steel-hard, white iron,
and a
sorts of pig-iron for his principal materials,
of the desired qualities
soft
grey iron.
—a highly carbonised,
7
[
Although
materials, to
another
way
it
appeared impossible, by the mere mixture
combine hardness and toughness
different
seemed
less difficult,
materials together
is
the
of the
same stratum
if
it
were possible
to
two
of iron,
on a
soft
combine the
with such a gradual change of their
marked
respective properties that no
this
in the
of solving the problem, to produce a hard surface
elastic interior,
two
]
line of separation should
solution which Gruson,
after years
of
effort,
occur
;
and
succeeded
in
reaching in such manner that even at the present day his chilled cast-iron
possesses a superiority over that of other makers.
Gruson attained
his object
by a seemingly simple procedure.
By
the use of iron forms or moulds for casting, he prevented, by a rapid
cooling of the surface, the always existing tendency in
for the
It
a fluid casting,
carbon to separate
off in scales of
would be foreign
to the scope of this compilation to specify the
details of the
graphite.
manufacture of the chilled
iron,
and we
will only describe
the peculiar structure which characterizes the broken section of a piece
of the
Gruson
chilled cast iron.
Fig.
I.
Section of a Chilled Cast Iron Bar.
It will
bar, that
be noticed
the
in
which shows the section of a chilled
of a fine fibrous character, which passes
this figure,
exterior layer
is
without visible lines of separation into the granular structure of the
so-called mottled iron, which in turn gradually assumes the character
and
fine crystalline structure of the soft
This
is
grey iron.
the great difference which distinguishes Gruson chilled iron
A2
8
[
from that of other manufacturers
of
the layers
between the hard and
The Gruson
whose
in
always more or
is
]
of
iron the line
less distinctly
separation
marked, and the edge
soft metal visibly seen.
chilled
possessed consequently
iron
which are appropriate as a material
Hard armour was
for
armour
discredited because brittleness
necessary accompaniment of
the properties
all
plates.
was thought
be a
to
Gruson's metal offers a hard
hardness.
surface on a tough interior, combining thus hardness with tenacity.
The attempt
to
to distribute the effect of a shot over a large surface
be given up on account of the
difficulty of rolling
had
such large plates as
were required for this. Gruson's cast metal permits any required form
and dimensions being given to the plates.
armour was rejected on account
Finally, the curved exterior surface of
of
the impossibility of
giving this form to wrought iron plates.
With
Gruson's metal any required external shape can be adopted.
Fully
the
realising
advantages
of
abandoned the views which prevailed
in
his
respect to the previous course of action.
which
form,
ellipse.
in
vertical
section
Such a
surface,
by
and besides
it
its
metal,
Gruson
completely
England, and returned in every
To
his plates
approached that
of
he gave a curved
a quadrant of an
hardness, deflected the shot striking
it,
possessed this advantage, that, by reason of their arched
form, the plates supported one another, and retained their position by their
weight, without the necessity of securing them by bolts.
came
Following
this
the reduction of the port to a minimum^ so as to prevent the entry of
splinters of
shell,
and, as a consequence thereof, the old type of gun
carriage had to be abandoned, and a
new one devised
round which the gun turned was placed
became considerably reduced
in size,
in
the
in
port
which the pivot
itself.
The
port
and was almost completely closed by
the chace of the gun, so that the port screens in use
were no longer
necessary, as there was but small chance of any splinters of projectiles
entering by the small opening reserved between the sides of the port and
the chace of the gun.
As
the
chilled
iron
can be made to take any desired form,
it
is
applicable to every system of fortification, of which, however, the most
usual forms are protected fixed batteries and revolving turrets.
9
L
Protected Batteries.
I.
Fig. 2 gives
The embrasure
J
an external view of a protected battery for
six guns.
armour, and
or port plates form the chief part of the
stand on the so-called pivot plate, being supported on each side by a pillar
plate
{see also Fig.
At each end
3).
the battery rests against masonry, which
In front of the battery
earth parapets against shot.
protected by
is
a concrete glacis,
is
covered with substantial granite blocks.
Defence against curved
in front to
the port and
fire
is
given by the roof plates which join
pillar plates,
and
in rear rest
on masonry pillars
forming part of the casemates.
Fig
2.
View of a Chilled Iron
Armour
Battery.
J.
The adjoining edges
surface,
when
and each edge
the battery
of the plates
is
-
' i
planed to
a
flat
provided with a groove, into which zinc
is
cast
of
several
plates
are
mounted, or iron keys inserted.
no further
The whole
is
the
t*^ "^
Owing
to the
weight
fitting is necessary.
structure
lies
on foundation
plates,
provided on their
upper and lower surfaces with two ribs, of which the upper clasp the
armour plates and render dislocation impossible, whilst the under ones
are embedded in the masonry forming the foundation.
The form
and
it
of the port, pillar,
and roof plates
is
shown
in Figs. 2
only remains to notice the pivot plates, which take their
the pivot bars of the carriages which are connected to them.
and
3,
name from
As already
explained, the port pivotting or minimum-embrasure carriages are of special
[
10
]
construction, the point round which the
port
gun
rotates being situated in the
itself.
As a
large arc of horizontal training
is
with four rollers travelling on two curved
movement being placed
horizontal
required, the slide
racers,
vertically
is
furnished
and the pivot
beneath the point
for the
in
the
port round which the gun works for elevation or depression, admits of any
exact training, and this
is
effected
by simple winch gearing.
Fig.
Section of an
As
will
structure,
be seen from
which
is
this,
connected
3-
Armoured
Battery.
an armoured battery forms a spacious
in the rear to the
casemates by means of
wide passages.
In the
basement
of the
casemates the magazines are placed, com-
municating with the upper storey by means
of lifts
and
staircases.
11
L
Armoured Turrets.
II.
In cases
]
of horizontal fire is necessary
where a greater arc
be easily obtained from a fixed battery, recourse
whose guns
fire
through the whole
of such a turret,
and
is
circle of 360°.
clearly explains the
mode
had
than can
to revolving turrets
Fig. 4 gives a section
of construction.
Fig. 4.
Section of a Chilled Iron
The dome-shaped cupola
on a
rotates
and
is
live roller ring
rests
A fmour
Turret.
on a wrought iron sub-structure, which
running on a
roller
path fixed to the foundation,
protected from shot by a glacis armour.
The lower
roller
path of the turret which
provided underneath with continuous
masonry
On
ribs,
is
|
j
in section, is
which are embedded
in
the
of the foundation.
this is the live roller ring, which,
being without a central pivot,
12
[
]
gun being capable
allows the whole interior space to be utilized, the
being mounted
On
in position
through
space from below.
this central
the rollers rests the upper roller path which carries
structure
the
of
structure carries on
The cupola has
its
and angles.
the sub-
The sub-
of cupola plates, whilst
lower part support the gun carriage.
the form of a domCj or flat arch, as already mentioned
shape
speaking, the
quadrant of an
iron plates
of
upper surface the ring
its
transverse girders fixed at
(accurately
up
turret, built
of
is
that given
and consists
ellipse),
by the rotation
number
a
of
of
of
the
separate plates,
which, as their centre of gravity, in consequence of their construction and
arrangement, passes through the middle point of the cupola, mutually
balance, and, owing to their weight, do not require to be otherwise
The adjoining
or tied together.
edges, moreover,
are
bound
provided with
grooves, as mentioned in the case of the battery, which grooves are
with zinc or iron keys when the cupola
The dome shape 'has
are deflected
mass
the following advantages:
the blow of impinging shot
space
;
is
economized
is
and
;
is
distributed over the whole
lastly,
there
is
no need
of
for
the
facilitated.
As
being
—Attacking projectiles
and the construction
or nuts to bind the plates together,
bolts
roof
;
of the plate
filled
being set up.
is
in
the battery, the roof plates
filled in
The
in
lie
simple grooves, the joints
on mounting the cupola.
which protects the substructure, consists, as Fig. 4
curved plates, which either partly or completely
glacis armour,
shows, of
a ring
of
encircle the cupola, as
may be
concrete, with granite blocks.
This
advisable.
The cupola
is
covered by a layer of
rotated by vertical pinion
is
gear, working in a circular rack fixed to the upper roller path.
The gear
is
arranged for working either by hand or power.
hand-gear consists of a capstan placed
the right in Fig. 4,
in the
and means are provided
The
lower casemate, seen on
for giving either a quick or slow
turning motion.
Heavier cupolas are
of
which can be placed
If
power
is
fitted
in
with both hand and power turning gear, each
and out
used, the
of action as required.
engine
is
turning gear, or this latter is actuated
either
connected directly to the
by means
of
a hydraulic motor
and accumulator.
The necessary
orders for the turning of the cupola are given through
speaking tubes communicating from the look-out post of the officer in
[
command, who, standing on
13
]
a step, looks through a sighting hole
made
in
the roof of the cupola, and directs the position of the gun.
The employment
of the various
chambers
in the
turret
is
seen in
the Fig. 4.
The
cartridges are passed from the magazine
The
middle platform.
cupola.
A
shell
magazine
upi
through a tube to the
in the central
chamber below the
takes the projectiles on to the platform under the cupola,
lift
from where they are taken by a crane
III.
is
to the
breech of the gun.
Gruson's Hydraulic Minimum-Port Carriage C/80.
As already
armoured batteries and cupolas are furnished
with minimum-port carriages, the special feature of which is that the gun
stated, the
rotates both vertically
and horizontally round a point which
lies
within the
port.
The upper
plates,
and
portion of the carriage, as Fig 5 shows,
on
slides
recoil
on the lower portion or
controlled by two hydraulic buffers.
The
is
formed
of steel
slide, the recoil
being
cylinders of these buffers are
fixed to the slide, the rods of the pistons, which are pierced with holes,
being attached to the upper portion
recoils, the piston
of the carriage.
When
the carriage
rods are drawn out, and the passage of the fluid in the
buffer through the holes in the piston checks the motion.
The gun
is
elevated or depressed by a hydraulic cylinder the ram of
which, by means of a cross-piece, raises or lowers the two trunnion-bearings.
These
last slide
up and down
in circular
grooves fixed to the brackets of
the carriage, the centre of motion being the imaginary pivot in the port.
of the gun is controlled by a slide-bar, which, as the Fig. 4
on
a pivot placed in armoured structures vertically beneath
moves
shows,
the port. The gun is connected to this slide-bar by a clip-shaped guidepiece in such a manner that on recoil it slides on the bar but always
The movement
preserves the axis of
(The axis
its
bore parallel to the upper surface of the slide-bar.
of the bore thus
remains during the movement of the gun
a tangent to an imaginary circle of which the centre
slide-bar.)
is
the pivot of the
14
[
Fig.
]
S-
Gruson's Hydraulic Minimum-Port Carriage C/8o.
In the smaller carriages the hydraulic
worked by hand-pumps
These consist
;
ram which elevates the gun
of long cylinders containing liquid, the pistons of
are weighted and operated upon either by hand or steam power.
which
These
cylinders communicate with the cylinder of the elevating press in
carriage.
ram
opening a valve the
of the press
stops^
the
On
when
gun
and
fluid
raises the gun.
the escape valve
is
the
under pressure passes under the
When
opened the
the valve
fluid flows
closed the
is
gun
out of the press and
sinks.
The accumulators
An
is
with the larger ones accumulators are used.
thus act as reservoirs and distributors of power.
important saving of power
in the
accumulator
is
effected
by using
Gruson's differential piston in the elevating cylinder of the carriage instead
of the ordinary form of piston, but a description of this
is
unnecessary
here.
The
installation of the accumulators
can be carried out in different
ways.
In batteries with
all
the guns are
many guns
worked from one
several accumulators are combined,
central reservoir of power.
and
[
15
]
In isolated turrets the accumulators are located in the basement, and
can serve also as hydraulic cranes for changing the guns if necessary.
Many
carriages are fitted for working both
Fig. 5
shows a carriage
for an
runs on two racers by means of
figure.
by accumulator and by hand.
armoured battery, which
rollers.
In revolving turrets no training
The pivot
movement
for this
is
is
in that case
seen in the
required to be given
to the carriage, the latter being as a rule solidly fixed to the sub-structure,
as before explained.
The leading particulars of a number of carriages type C/8o, which have
been completed, are given in the following table. For other carriages,
compare table (page 17), the data there given are approximately correct
for the type C/80.
Gun.
L
IT.
I
Gruson's Hydraulic Minimum-Port Carriage C/84.
This carriage
ment
16
differs
from the type C/8o chiefly in the altered arrangeIn the latter the elevating press
for lifting the gun.
the carriage, and moves with
it
on
attached to
is
recoil.
Fig.
6.
Gruson's Hydraulic Minimum-Port Carriage, CJS4.
As seen
in this figure, the carriage
proper consists merely of bearings
proper on which the carriage moves in
and out is surrounded by a frame of plates bolted together, fitted on the
is given
inside with guides for the upward and downward movement, which
of the
to both slide and carriage by a press placed beneath the movement
The
for the gun-trunnions.
slide
;
gun
regulated as in
is
piece
the carriage type C/80 by a
is
and the guide-
carried round the chace of the gun, as seen in the figure.
The
of the
slide bar,
slide-bar rotates round a pivot placed
gun remains tangential
the centre during
The
its
under the
to an imaginary circle, of
and the
port,
which
axis
this pivot is
elevation or depression.
recoil cylinders are in this
type of carriage made fast to the
guide-piece, their pistons being attached to the front part of the slide-bar.
As the carriage runs on its slide by means of four rollers, but little of
the force of the recoil
The
carriage
is
shown
received on the slide.
in Fig. 6 is
intended for an armoured battery, and
runs on two curved racers by means of four
horizontal training
is
seen
in the figure.
rollers.
The
pivot for the
[
17
1
Horizontal training being unnecessary in the case of a turret carriage,
the frame
is dispensed with, or rather is embodied in the substructure of the
These carriages can be adapted for either hand or power working.
The type C/84 has several advantages over the earlier form. It is more
turret.
compact, and also simpler, as the elevating cylinder does not take part in
the
movement
of recoil,
and moreover, the
recoil cylinders
being brought close up underneath the gun, the force of
end
of
and the
slide
recoil acts at the
a much shorter lever.
The
principal dimensions, &c., of the carriages, type C/84, ^re given
in the following table
:
Gun,
Carriage.
Extreme
Calibre,
JU
No.
^
-a.
lbs.
(about)
4-1 10.5 30
2,200
4-7 12
30
4,400
5-9 15
30
8,800
6-7 17
30
15,000
8-3 21
30
26,900
9-4 24
30
41,900
10-2 26
30
65,100
11-
28
30
73,900
12-
305.
30
97,000
13-8 35
30 165,400
16-8 40
30 247,000
[
18
CHAPTER
1
II.
Firing Trials of Gruson Chilled Iron Armour during
the years 1869—1874.
As
already stated,
distinct series, those
The
1882-86.
with the Gruson armour are divided into two
trials
between the years 1869 and 1874, and those between
is the first series, which we have
subject of this chapter
already described in a pamphlet, but here again summarise.
In
doing so
" Mittheilungen
The
we
take as our guide Major Kiister's account in the
des Konigl.
quotations which
we
Preussischen
Ingenieur-Comites,"
give from that account are reproduced
part 22.
word
for
word.
I.—Preliminary Trials
72-pounder (8.3
in.)
of
a Chilled-Iron Armour Emplacement
The
trial
a
Gun, at the Tegel range in the years 1869—1871.
Object and Scope of the
was
for
Trial.
was intended to clearly demonstrate if Gruson's chilled-iron
and the programme of the trial did not therefore
suitable for armour,
proceed on the lines of representing, as
attack such as might occur
The
firing
was
in the later ones, the conditions of
in actual warfare.
chiefly carried out with 8.3 in.
and 9.4
iii.
guns, which
On the other hand, the
were principally used against coast batteries.
armour was struck far more frequently than is possible with fire from on
board ship.
We
have
for that reason styled this trial a preliminary one.
[
19
]
Fig. 7-
Chilled Iron
Vertical
Armour Emplacement
and Horizontal
for a 'j2-pounder 8.yn. Gun.
Section through the centre of the embrasure.
THE MEASUREMENTS IN ALL SKETCHES ARE MILLIMETRES.
;
[
As
the
first trial of chilled
20
iron armour,
and as the design
of the structure
derived from earlier
trials,
of the
power
]
it
possesses an especial interest
had been prepared without any data
and was indeed merely the
of the attack,
it
is
desirable
to
give
result of
an estimate
a somewhat ample
description of the emplacement.
Fig. 7
shows a
vertical
and horizontal section through the centre
of the
embrasure.
side
The emplacement was composed of a curved embrasure plate, two
and two roof plates. The peculiar shape and principal dimensions
are seen in the figure below.
Fig.
Chilled Iron
8.
Armour Emplacement for
a 'j2-pounder 8.3
in.
Gun
in
course of erection.
From a Photograph.
The side plates and also the
roof plates
were tied together by wrought-iron
connecting rods; the edges of the roof plate are shown in the horizontal section
by dotted
lines.
The emplacement
rested against masonry, of which the
21
[
second plate shown
in the figure
covered with earth, as shown
was exposed
The
to the attacking
]
formed the
in
The whole
roof.
structure
was
Fig. 9, so that only the embrasure plate
fire.
peculiar curve at the base of the embrasure plate, seen in Fig.
7,
was formed to receive the pivot of the minimum embrasure carriage, which
was fastened to a ground plate not shown in the figure. All the plates were
cast in a foundry specially erected at
Fig. 8
On
left in
shows the emplacement
Tegel for that purpose.
in course of construction.
the surface of the plates, in Fig.
the casting, which was then
together, and not in one large
made
mould
may be
8,
seen the square seams
in several small chill-moulds
for each plate, as
is
now
placed
the case.
1.—Trial against the Embrasure Plate of a Chilled Iron Armour
Emplacement for a 72-pounder (8.3 in.) Gun.
In February, March, and December, 1869.
The
particulars of
the attack, as well as the effect of the various
rounds, are tabulated in the following table
The
chief data
given in the
first
:
edition
are completed from the
pamphlet, " Vergleichende Zusammenstellung der neuesten Schiessversuche
gegen Panzer von Otto von Giese."
t
No.
of
Round
22
1
[
23
]
24
[
Fig.
]
9.
The Port Plate of the Armoured Emplacement
for a 72
pounder
(8.3 in.)
gun
after the 15th round,
1
1/3/69.
From a Photograph.
Fig. 9
The
shows the armour
at the
end
of the firing with the 9.4 in. gun.
cracks formed were so fine that they do not appear visible in the
photograph.
To
save ammunition, the firing was then continued with the long 8.3
in.
hooped gun at a distance of 166 yards. It should be noted that 8 shots,
rounds 12 and 16 to 22, struck on about the same place, close to the port.
The experiment was intended merely
as a test of the material, without
the conditions of actual warfare, but was, nevertheless, a very severe
trial
on account of the small thickness of the plates.
The Experimental Committee considered
cast-iron as a material for
armour
to
All the shot
which struck broke up.
chilled
be thoroughly demonstrated, even
though doubts were expressed as to the
necessary.
the applicability of
size
and weight
of the plates
25
[
1
Trial against the Left Side-plate of a Chilled Iron
2.
Empla«ement for a 72-pounder
14th
Gun
and
Distance
Shot
in.
(15 cm) gun.
166 yards (152 m.)
:
Solid chilled 76.5
:
Charge
lb.
(347 kg.) weight.
5.5 lb. (2-5 kg.) to 6.6 lb. (3 kg.) P.
•
Armour
Gun.
2 1 St April, 1870.
Rifled bronze 24 pounder 5.9
:
(8.3iii.)
The
7.1
mean
plate at the
— 10. 2
point of impact had a thickness of
Six rounds struck at angles between
in.
The
P.
three
first
no
produced
hits
result
;
So''
and 90°.
the three last
widened a casting seam, and formed several hair cracks
in the
plate.
The
was resumed on the 21st April with the
trial
in.
5.9
hooped gun.
Gun
24 pounder 5.9 in. (15 cm) hooped gun.
Distance: 166 yards (152 m.)
:
Shot
Chilled shell, weighted with sand to 78.3
:
Charge
u— 13.2
:
lb. (5 to
6 kg.) P.
lb.
(35.5 kg.)
P
The rounds were aimed at the left, and the least
portion of the plate.
Mean angle of impact 70°
Thickness of plate 10.2
The
cracks
cracks,
II
in.
six
first
diameter
flat
7
12
to
Rounds
plate.
off
75°.
in.
hits
through the
and broke
— 10.6
—Nos.
injured,
to
pieces.
in the plate.
—caused
12
to
a number of
enlarged
16
the
No. 17 produced a hole of
No. 18 broke
off
several pieces
of the plate.
Trial against the Right Side-plate of a Chilled Iron
3.
Emplacement
for a 72-pounder (8.3in.) Gun.
nth
Gun
June, 1870.
24-pounder 5.9 in. (15 cm) hooped gun.
Distance 82 yards (75 m.)
:
:
Shot
:
Solid chilled 74.9
Charge
:
Angle
The
lb.
(34 kg.) with blunt point.
13.2 lb. ^6 kg.) P.P.
right plate
of
impact about 72".
was
of harder character than the left one.
Armour
[
Mean
thickness of
produced a number
26
]
plate
10.2
The
in.
first
five
rounds
of through cracks.
After the sixth shot, a piece of the plate threatened to
but four additional shots on the same place failed to dislodge
The
cracks showed
that
the
seams
formed
in
fall,
it.
casting
injured the strength of the plate.
Trial against the Dismounted Roof Plate of a Chilled Iron
4.
Armour Emplacement
for a 72-pounder (8.3 in.) Gun.
7th October, 1871.
Gun
8.3 in. (21
:
Distance
Shot
:
Weighted
Charge
:
cm) Mortar.
41 yards (37.5 m.)
:
4.4
Shell, 176.5 lb. (80 kg.) weight.
lb. (2 kg.)
Velocity of impact
:
with the
first,
8.8 lb
(4 kg.)
with remaining rounds.
229 yards (209 m.)
Energy: 581.5 foot tons (180 mt.)
The
plate, of
mean
thickness of 7.1
in.,
was so placed against
its
supports as to be struck in the centre at an angle of 90°.
The
four shots which struck produced no effect.
Summary
of 2,
3,
and 4 :
Considering the moderate thickness of these
plates, the resistance of the
left
side plate
must be considered
excellent.
The
trial
of
the right side plate demonstrated the dis-
advantage of making the moulds
in
pieces, the casting
seams
producing cracks.
That against the roof plate showed the
against iron constructions to be very slight.
All the projectiles
which struck broke up.
effect of
mortar
fire
27
[
J
Firing Trials against Chilled Cast-Iron Armour for Inland
II.
1873—74.
Fortification in the Tears
1.
Firing Trial against the First Chilled Iron
two 5.9 in. (15 cm) Guns.
At the Tegel Range, March,
Scope and Programme
The
in 1871
trial
was intended
to
of several plates;
1873.
of the Trial.
turret designed
by Major Schumann,
the thickness of the port plate was 12.4
in. at
5.9 in.
Guns.
in.
and the
the back of the cupola.
The
Fig. 10.
of the Port Plate of the First Chilled Iron
Armour Turret for two
of
This turret had a cylindrical cupola, formed
thickness of the plates decreased to 4.7
Profile
for
form a comparison with the experiments
— 72 against a wrought-iron
the Royal Prussian Engineers.
Armour Turret
Schumann
the
of
trial
had
turret
given comparatively
favourable results, and as Gruson
Scale 1/40.
had offered to construct at
cost
one
of
his
turrets
equal resisting powers,
desirable to adopt
same programme
less
it
of
seemed
not only the
of trial, but also
to follow the thickness given to
the wrought-iron plates.
cordance with
of
the
given a
this,
chilled
iron
maximum
In ac-
the port plate
turret
was
radial thickness
of 13.8 in. (see figure 10), which,
both in the two side plates, the back plate, and the roof plate, decreased to
4.7
in.
at the back.
The maximum
9.1 in. in front, the height
The weight
radial thickness of the glacis
armour was
and extension to the front being each 3.28
feet.
was 12.4 tons, of the side plate lo.i
was mounted on the same sub-structure which had
served for the Schumann turret.
Guns: Short 5.9 in. (15 cm.) naval hooped gun; 5.9 in. (15 cm.) bronze
tons,
and the
of the port plate
turret
gun.
Distance: 412 yards (377m.)
Shot: 5.9
in. (15
cm)
5.9 in.
filled shell,
(15 cm)
61 lb. (27*7 kg.) weight.
chilled shell,
both
filled
and weighted 77.2
lb
(35 kg.) weight.
5.9
in.
(15 cm) solid chilled shot, about 79.41b. (36 kg.) weight.
—
28
[
Charge: Varying from
3.1 lb.
]
cannon powder to 13.21b.
(1.4 kg)
(6 kg.)
prismatic.
Velocity and energy
On
:
account of the variety in shot and charges
—not
separately recorded.
Major
speaking of the results of
Kiister,
this trial, says:
" On the whole, the front plate received 55 hits, of which
about 60 per cent, were chilled projectiles, the right* (left, looking
from the gun) side plate
projectiles
which 9 were
13 shots, of
the glacis plates 23
;
chilled
being chilled projectiles.
hits, 19
" Against the roof of the turret, 2 hits from the il in. rifled
mortar, distant 1,585 yards, with 8.8
weighted to 441
lb.
"The long
or
produced no
hand the
common
shell
lb.
charge and long shell
which struck the
visible effect at the point of impact,
chilled projectiles
armour
solid
on the other
produced shallow indents and splinter-
ing, for the
most part with concentric and also frequently
hair cracks,
which
last,
by the vibration
radial
of the next hits,
were
lengthened and deepened and eventually divided the plate into
several parts.
off
the
Sometimes
exterior of
also thin pieces of plate
were knocked
the armour, but on no occasion
any penetration into the
was
there
latter."
Additional evidence was furnished of the unsuitability of using chilled
iron in plates of small thickness
when exposed
of the cupola being fully breached
at a distance of 1,585 yards (charge 8.8
By
far the best resistance
to mortar
by the second shot
lb.,
shell
441
was shown by the
not succumb to 23 chilled shots from
the
5.9
fire,
of the
lb.,
the roof plate
1 1
glacis armour,
in,
in.
mortar
elevation 30°).
which did
hooped gun striking
together on a small surface.
Summary: The
general result of the
Kiister as unfavourable.
chilled iron,
it
chilled iron
in
trial is rightly
had been forgotten that the
and wrought iron forbade a
the two systems,
as
considered by Major
In determining the dimensions of the
was the case
radical difference
between
similarity in this respect
in this
consequence the advantageous properties
of
instance,
chilled
and
iron
in
for
armour could not be shown.
Even
right
if
this trial clearly
proved that when the thickness of
* Major Kiister's " right left " means looking from the turret.
As during the new trials,
and left is always taken to mean looking from the attacking guns, we shall adopt this latter
course also.
[
plating
did
is
29
wrought iron
small,
]
is
preferable to chilled cast iron,
it
not the less give indications that in the case of greater
would have the preference.
thicknesses, cast-iron
was noticed that all the projectiles on striking broke up
into countless fragments; and, further, it was proved that the
armour could only be destroyed by breaking it into pieces, which,
however, the extreme hardness of the material and its extraordinary
It
resistance to molecular displacement rendered a very difficult task,
qualities
and
which were greatly assisted by the double curved form,
likely
to be
still
more strongly displayed with increased
thicknesses of iron.
In accordance with these conclusions, the
at the termination of these
iron
chilled
for
glacis
armour,
Committee already,
recommended the use
trials,
first
giving,
of
however, a provisional
preference to the use of wrought iron for the turret
itself.
was considered desirable to undertake further trials, as
seemed in no way excluded of obtaining a
practically favourable result by giving an improved form and
It
the possibility
increased strength to the armour.
2.
Firing Trial against the Second Chilled Iron Turret for two
5.9 in. (15 cm) Guns.
At the Tegel Range, May
Scope and Programme
At the conclusion
his
readiness to
dimensions,
of the
supply,
and more
in
at
—
July,
of the Trial.
above described
his
own
1874.
cost,
Gruson had professed
trial,
a
new
turret
of
increased
accordance with the conditions shown to be
essential.
At the suggestion of the Experimental Committee, the War Department undertook to supply the ammunition, but directed at the same time
that the trial should proceed in accordance with a definite aspect of the
subject obtained from a consideration of the numerous special necessities
of the case
approach
in
brought to light by the preliminary
its
conditions
as
trial,
that the trial should
near as possible actual
determination of which, use was to be
made
reality,
of the data furnished
for
the
by siege
operations.
It
was assumed
that the siege corps would be unprovided with the
heaviest armour-piercing guns, and that the firing would
5.9 in. long shell.
commence with
—
[
„
]
"
'^"
„
30
During a
Profile of the Port Plate of the Second Chilled
Iron
Armour
Turret for 2 5.9
in.
^^^
Guns.
,
thirty
,
,
days'
to 1,500 shells,
entirely
and
sufficient
the turret under
it
r
it
if
,
trial
was considered
a quadrant of
withstood 200
long shells from the 5.9
gun
siege
armour of the
would be struck by from 1,000
turret
Scale 1/40.
,
,
calculated that the
in.
hooped
at a distance of 1,093 yards.
proved to be the case,
this
If
then the armour was to be attacked
by the
dition
hooped gun, a conaccepted with confidence by
in.
6.7
Mr. Gruson.
With
fire
a further
respect to
trial
being made with heavy siege-guns,
would then only be opened on the
allowed
it,
when the
assailant
to 1,093 yards from the turret
turret,
supposing circumstances
had advanced as near as possible
—so
as to
make
—say
the utmost use of chilled
iron shell.
The
second, of 150
And,
named
first
—
series
of rounds
5.9 in. chilled shell,
lastly, as it
battery gun of 4.9
was therefore
was within the bounds
—5.9
to
be followed by a
delivered on the second ring plate.
of possibility that a
heavy coast
tons in weight might be brought to a distance of
1,093 yards from the turret, a third plate was to be attacked with 20 chilled
shells from the 6.7 in. hooped gun, and finally, the roof plate with five hits
from the
1 1
in.
mortar.
The Armour
One
to
be tried consisted of four newly made plates,
viz.
port plate, two side, and one roof plate, which were placed on the
original sub-structure,
at the first trial
The
and supported
on account of
in
rear
by an old port plate rejected
faults in casting.
profile of the port plate is
shown
in Fig. 11,
which exhibits
chiefly
an increase in the radial thickness at the centre of the port from 13.8
21.7
:
in.,
16.5 in.)
remained unaltered and was merely supplemented with an additional
The change
of the port plate
The
in. to
and a corresponding thickness was given to both side plates
The roof plate was also 16,5 in. thick. The glacis armour
in profile
is
first trial
between Figs. 10 and
11
plate.
of the external curve
at once observable.
had brought to
light the fact that shot striking the
part of the curved surface at an acute angle did
upper
more damage than those
31
[
]
which struck lower down at a greater angle.
This curious result was
explained by the fact that the ordinary cast-iron and chilled cast-iron shot
in the first case
broke up into large pieces, which made considerable indents
into the surface of the armour,
causing visibly less
and
In
effect.
in the latter case
consequence of
given a more rounded form, as seen in Fig.
The weights
strike at a greater angle.
plates
were respectively
broke up into atoms,
new
the
this
plate
ii, so that projectiles
of the port, left side,
19.7 tons, 16.4 tons,
and 16.36
and
right side
tons.
Trial against the Port Plate of the Second Chilled Iron
A.
Turret for two 5.9
Guns
:
Two
Distance
Shot
:
:
5.9 in, (15
in. (15
cm) Long Shells.
cm) hooped guns C/72.
165 yards (150 m.)
cm) long
5.9 in. (15
Charge:
Armour
cm) Gnns.
In. (15
Attack of the Port Plate with 193 5.9
(a)
was
should
shell, filled, total
weight about 61. i
lb.
(27.7 kg.)
(4.14kg) P.P., equivalent to 13.71b, (6.2kg.) at 1,093
9.1 lb.
yards (1,000 m.)
Striking velocity
400 yards (366 m.)
:
Energy: 612 foot tons (189,46 mt.)
The
stipulated 193 hits
which ^ struck the
it,
flatly
were obtained
but in general the effort was
whole surface.
in
two days with 200 rounds,
curved part above the port, and
made
The
result of
of
the part beneath
to distribute the hits equally over the
Major Kiister says on page 20
"
|
of his report
this first part of the
trial
on the
trial
was completely
satisfactory, the turret at the end of the firing being practically
uninjured.
"
left
At the 33rd shot a
hit
on the right edge of the right port (the
off apiece about 2 in. wide and
one looking from the gun) broke
deep, which injury, however, though the same spot was repeatedly
struck, was only increased to a small extent, and that only superficially.
The
70th round produced a fine superficial crack, starting
from the injured place and running towards the inside of the port.
"
The
effect of the individual rounds was only recognisable on
by oblique hits, causing indents about 0.08 in. deep
otherwise the hit was unrecognisable except by a discoloration of
the
plate
the part struck."
In
view of
this exceptionally favourable
behaviour of the plate,
decided, before proceeding with the programme, to attack
it
it
with 5.9
was
in.
32
[
]
chilled iron shell so as to establish a
comparison between it and the slighter
was to undergo the same ordeal with chilled shell, previous
more severe injuries with the 6.7 in. shell.
side plate which
to inflicting
(b.)
Attack of the Port Plate with ten
Gun
As
:
Distance
As
before.
(15 cm) chilled shell, weighted about 77.2 in. (35 kg) weight.
in.
Charge: 10.6
in,
(4.8
Striking velocity
:
kg) P.P.
383.6 yards (350 m.)
705.98 foot tons (218.57
:
All 10 rounds struck
These
Chilled Shells.
before.
:
Shot: 5.9
Energy
cm)
5. 9in. (15
hits
"^t.)
between the
2 ports.
produced, as Major Kiister says, no visible
effect.
was therefore decided to proceed with the programme, and
re-commenced with the 6.7 in. gun.
It
Attack of the Port Plate with twenty 6.7
(c.)
in. (17
firing
cm)
Chilled Shells.
Gun
Short naval 6.7
:
Distance
Shot
:
:
(17 cm)
hooped gun.
165 yards (150 m.)
6.7 in. (17
Charge
in.
20
cm)
chilled shell, weighted,
about 12 1.5
(9.10 kg) P.P., equivalent to 26.5
(1,000 m.)
:
lb.
Striking velocity
Energy:
The
:
lb.
lb.
(54.9 kg) weight.
(12 kg) at 1,093 yards
441.6 yards (404 m.)
1,478.05 foot tons (457.6 mt.)
shot struck 7.9
first
and produced no
Rounds
in.
above the glacis plate on the middle
line,
result.
2 to 6 produced
two short cracks running from the upper and
lower edge of the right port.
Rounds
7
and 8 lengthened and deepened these cracks, passing right
through the plate and separating the right corner, attributed by Major
Kiister to the defective condition of the upper girder of the sub-structure.
Rounds 9
in a
to 20
cracking
were
off of
additional cracks
(d.)
The
fairly distributed
the surface 10
in.
over the plate, their effect consisted
long and wide and 0.4
in.
deep.
No
were made.
Attack of the Port Plate with sixty-five 5.9 in. (15 cm)
Chilled Shells.* Details of Attack as under (b.)
first
eleven hits produced a through crack between the two ports,
• This part of the
firing
was only carried out
at the conclusion of the
whole
trial in
July, 1874.
33
[
which ran from the edge
Rounds
]
of the left port to the lower border of the plate.
12 to 47 increased the cracking and disintegration of the plate.
The 49th
produced a vertical crack, running from the horizontal
hit
Nos. 50 to 65 increased the damage.
crack to the lower edge of the plate.
Portions of plate had been shaken loose on the inside, and had fallen down.
Summary The
:
plate
No. of hits.
had altogether received
cm) Long Shell
611. 96 foot tons (189,46 mt.)
193
5-9
20
67
„
(17
„) Chilled Shell
75
5-9
»
(15
..)
ill-
(15
288 rounds with
»
1478.05
„
705-98
,,
..
(457-6o
„
)
(218,57
„
)
200.615 foot tons (62,110 mt.) energy.
...
...
:
Energy.
Projectile.
Nevertheless, in the opinion of the Committee, the breaching of the
plate
was
from being arrived
far
still
at.
Major Kiister sums up (page 24) that the plate had displayed such a
high degree of tenacity that it would doubtless have still resisted a far
number
greater
of such blows.
" That, in addition, the plate had
capable of resisting 6.7
that,
in.
shown
a very considerable number of 5.9
the front plate
itself to
armour piercing
seemed not only
to have
in.
shell
a high degree
;
and, beyond
chilled shell,
satisfied the
so that
programme,
but was capable of withstanding a far severer ordeal, and with
complete success could serve as a basis for future constructions of
this category of armour-plating
both as regards form and thickness."
All the shot which hit broke up.
B.
Trial against the Left Side Plate of Second Chilled Iron
Turret for two 5.9
Gun
:
Two
Distance
:
Shot: 5.9
Charge
5.9 in. (15
in.
:
The
cm)
(15
lb. (4.8
Striking velocity
Energy
cm) Guns.
cm) hooped guns C/72.
165 yards (150 m.)
10.6
:
in. (15
Armour
:
chilled shell, weighted,
about 77.21b. (35 kg weight.)
kg) P. P-
383.6 yards (350 m.)
705.98 foot tons (218,57 i"t.)
hits
were proportionately distributed over the whole
produced abrasions up to 0.3
in. in
plate,
and
depth.
After the 12th shot, hair cracks connecting the points of impact were
:
34
C
The 39th
formed.
edge of the
hit
made a
J
from the upper to the lower
vertical crack
separating the plate into two unequal parts.
plate,
Hits
40 to 64 were placed on the larger portion and caused other two vertical
and horizontal through cracks. Beyond the cracks no effect was visible
on the
inside.
The
firing
was continued against
this plate until the conclusion of the
experiment.
Hits 65
to 103
produced cracks and abrasions up to 3.9
in.
in
depth.
No. 104
hit dislodged small pieces of
metal on the inside.
Nos. 105 to 133 produced a rapidly increasing disintegration of the
fractured parts of the plate, and at the
134th round,
a projecting portion of
armour was raised up,
the
causing an opening through the plate.
C.
Trial against
tlie
Right Side Plate of the Second Chilled Iron
Armour Turret
for two 5.9in. (16
cm) Guns.
Details of attack as under B.
The
The
plate
right
consequence
was harder than the
and
The
Hits 38
in
trial
was discontinued
behaved under the
of
fire
hit,
and divided the
—64 produced two other through cracks,
horizontal, as well as a
Summary
and the abrasions
through crack was produced by the 37th
first
plate from top to bottom.
vertical
left,
less.
number
of hair cracks.
after the 64th round, as this plate
had
exactly as the left one.
B and C
left side plate, the number of
programme had not been reached, but
only 1 34, the Committee considered the behaviour of this plate was
They reported also that the requirement of 150 hits
favourable.
was enormously high, and that the plate had received the last 70
Although, in the case of the
hits (150) assigned by the
hits
under peculiarly unfavourable conditions,
as,
being injured, the proper supports were lacking.
the roof plate
It is of
interest
to note that the Committee, as the result of their observations,
recommended also for the
made to correspond with
be
more
side plates that the profile should
that of
the port plate, that
is,
35
[
]
more sloped
perpendicular, or rounded at the bottom part and
towards the upper portion, because the formation of cracks, as
a
began with oblique
rule,
No
difference of behaviour between the softer left and harder
right plate
was
established.
All the shot
D.
broke up on striking.
Trial against the Roof Plate of the Second Chilled Iron
Armonr Turret
Gun
:
hits.
Rifled experimental
Elevation
Distance
Shot: II
:
:
1 1
two
for
5.9 in. (15
cm) Guns.
(28 cm) mortar.
in.
30°.
962 yards (880 m)
in.
(28 cm), long shell of 441
Striking velocity
:
lb.
(200 kg) weight, weighted.
107.8 yards (98.6 m).
Energy: 319.8 foot-tons (99 mt), equivalent to the energy
(21 cm) shell at 2,732.5 yards (2,500 m).
Five hits were obtained from 45 shots.
Nos. I and 2 struck the sighting hood and had no
of the 8.3
result.
No. 3 made two through radial cracks to the edges of the
No. 4 as I and 2.
plate.
No. 5 made two new radial cracks to the edges of the plate, so that
broken into 5 pieces.
Summary
:
In
in.
it
was
the opinion of the Committee, the roof plate had not
satisfied the requirements,
and they recommended
for subsequent
construction the use of wrought iron roof plates should be retained.
The general
result of the trial as
Kiister to be that not only had
applicable in the fullest
regards
A
to
C
stated
been proved that
chilled
manner
as a material for
armour
turrets for land fortifications, but also that sufficient data
for determining all the
is
it
more important
by Major
was
cast iron
for revolving
had been obtained
details of construction.
[
III—
36
]
Trials against Chilled Iron
in the Years
l.-Trial of the
first
Armour
for Coast Defences
1873—4.
Port Plate of a Chilled Iron Armour Battery
for 8.3 in. (21 cm) Guns.
On
Gruson's Firing Ground at Buckau,
Sth December, 1873.
Scope and Programme of the
Trial.
Fig. 12.
Already, in accordance
Profile of a Port Plate of the Chilled Iron
Battery for 8.3 in.
Armour
with
the
results
Guns,
preliminary
Scale 1/40.
the
trials
ordered
Gruson
in
from
chilled
Langliitjensand.
among
Mr.
armour
for
As some
difference of opinion
vailed
i86g,
Government
Prussian
had
the
of
pre-
engineers on
the subject of these
trials,
a condition was attached
to
order that certain
the
portions
of
were
be subjected to
trial
to
this
battery
under conditions that
they must
satisfy
certain
tests.
These were that a port plate should be struck by 2 shots, one over the
other, close to the edge of the port, from the 11 in. gun with a charge
corresponding to that of 88.
lb.
becoming unserviceable thereby,
(the service charge) at
820 yards, without
or that cracks formed should involve the
plate being unserviceable.
These
trials
inasmuch as there
had an entirely different aspect to the previous ones,
it
was a question
of land fortification, for
which armour
must be capable of withstanding a very great number of hits from medium
guns, whereas coast fortifications are only liable to be attacked by a small
number
of shot, but these of the heaviest guns.
37
[
The
]
subject o£ the trial consisted of
an armoured battery like that
previously described, and was composed of two port and three pillar plates,
together with the pivot and cover-plates belonging thereto.
struction
is
shown
in Figs. 13
and 16
;
Fig. 12
shows the
The con-
profile of the port
CO
06
CM
o.
ni
>.
bD
£
M
E
-?
o
+-»
o
.k
a.
ni
-Si
5
1.
plate, the curve
during the
wooden
corresponding to that which had been shown to be the best
first trials
at Tegel.
The
target
was provided with a strong
shield in front, which protected the attacking
pieces of shot flying
off.
gun against broken
38
[
The breadth of the port
The weight, 42 tons.
top.
Gun
Distance
Shot
ft.
below, and 10.8
(28 cm) chilled shell weighted, total weight, 512
in.
75
:
14.4
at the
ft.
17.5 yards (16 m)'.
:
1 1
:
Charge
was
cm) gun.
II in. (28
:
plate
]
lb.
(34 kg) P.P., equivalent to 88
lb.
lb.
(232 kg).
(40 kg) at 820 yards (750 m).
Velocity of impact: 420 yards (385 m).
Energy
5,685 foot-tons (1,760 mt).
:
The effect of the first shot was a small and hardly perceptible indent
and a short hair crack, and exhibited in a surprising manner the extraordinary reacting power of the material.
The
effect of the
was cracks
a,
visible at the
b,
c,
back
second shot, which struck on exactly the same place,
about 0.08
of the plate.
in.
broad, of which, however, only a
was
Although the port plate had thus complied
with the conditions of the contract,
it
was decided, on account of the
same spot,
interest attaching to the question, to place a third shot on the
which formed,
crack
e.
addition to a fine crack
in
at the point of impact, the
f.
Summary
:
The
plate had exceeded the conditions of the contract.
however, the result of the
total resisting
power
had thrown no direct
trial
of the material
decided to have a further
light
As
on the
under prolonged attack,
it
was
against the second port plate, and
trial
to represent the conditions of warfare
by
distributing the hits over
the surface of the plate.
All shot broke-to pieces
on impact.
2.— Trial of the Second Port Plate
for 8.3 in. (31
for a Chilled Iron
Armour Battery
cm) Onus, at Gruson's Firing Ground at Buckau.
27th July and 21st August, 1874.
Scope and Programme
The
to
trial of
of the Trial,
the second port plate was, in the strict sense of the word,
be a test of the material, and the
firing to
be continued
until the plate
was breached, without consideration of the accepted conditions under which
in
war the attack
of a coast battery
would be made.
arranged to ascertain the result after the loth
to
be formed with the
hit,
earlier trials carried out in
It
was, moreover,
so as to enable a parallel
England.
39
[
The weight
Gun
1 1
:
Distance
Shot
:
in.
:
(28
of the trial plate
was 44
J
tons.
cm) gun.
17.5 yards (16 m).
II in. (28
cm)
chilled shell,
weighted;
total weight,
512
lb.
(232 kgj.
a
bo
o
o
+j
JZ
a.
o
Charge
:
75
lb.
(34 kg) P.P., equivalent to 88
Velocity on impact
Energy
:
:
lb.
(40 kg) at 820 yards (750 m)
420 yards (385 m).
5,690 foot-tons (1760 mt).
C2
40
[
]
The sequence, as well as the points of striking of the various hits, are
shown in fig. 14. The two first shots, which struck the plate at angles of
79'^
and 52°, had no
crack
a, visible at
The
Rounds
3
back
an angle of
36^*)
caused
b,
under
a, splitting
the plate into two
c.
to 10
5
(at
the back of the plate.
deep near the
The
whatever; the third
fourth hit produced crack
halves, also crack
in.
effect
made an
left
external crack d, and an abrasion about
upper edge
of the port.
condition of the plate after the loth round
of the plate cracks a, b
and
c
were
was observed.
At the
visible.
The trial was considered (Kiister, page 47) to be more severe than
that made with a wrought iron plate in England in 1871, which was judged
to have shown a more than needful resistance when it withstood nine rounds
from a 12 inch gun, with a
trial
total
In that
energy of 43,000 foot tons.
the two external layers of the English armour were perforated by
all
the shot, and the third injured, whilst the chilled armour had received
no material injury on the
and had
inside,
in
no way
lost
its
inter-
connexion.
"We,"
says Major Kiister in conclusion, "
hesitation, that
may
state,
without
a port plate of the construction and dimensions
as in the experimental plate,
would
fulfil
all
probable require-
power of resistance. This
ments
favourable judgment," he adds, page 48, " was further confirmed,
and that to a degree beyond all expectation, by the subsequent
of actual
trial of
warfare as regards
its
the 21st August, 1874."
The conditions of attack were the same as in the
Round 1 1 (continued from the first part) cracked
firing.
first
from the point of striking to the under edge of the plate.
this crack.
plate.
No. 13 dislodged a small piece on the
left
part of the
the plate through
No. 12 increased
upper quarter
of the
Nos. 14 and 15 produced cracks on the inside of the plate, mostly
at the lip of the port.
pillar plate.
No. 16 broke
off
a narrow strip from the adjoining
17 to 19 remained without visible effect.
After the 19th, round the firing was suspended at the request of the
Committee, on account of the demolition of the protecting
having withstood nearly double the number of
assigned as likely to strike
Following
this the
hits
shields, the plate
which probability
it.
middle pillar plate was tested, one shot being
fired
41
[
at
without
it
]
This
excepting a slight indent.
effect,
pillar
plate
was
subsequently used in the construction of the battery at Langliitjensand, as
the effect of the hit was so slight that the point where
it
struck
was with
difficulty discoverable.
Summary
The
:
plate had withstood nineteen
in. chilled
1 1
with a
shells
energy of 108,010 foot-tons, without suffering any material
total
alteration of form.
true that the second series of rounds had
It is
dislodged certain portions which had been loosened by cracks.
Nevertheless, the armour must, in
subsequent condition, be
its
considered to have without question retained
its
protecting power,
which the Experimental Committee admitted.
The
trial
and not a
was, as already stated, a crucial test of the material
trial
under conditions
summarized that the
8.3 in.
of warfare,
power against
surplus of resisting
and the
result
may be
battery had shown a considerable
the
attacking guns of that
date.
Trial of a Roof-plate for a Chilled Iron
3.
8.3 in. (21
2 1 St
Armour Battery
cm) Guns.
August,
1874.
Scope and Programnne
of the Trial.
Firing against the roof plate was not carried out, as in the Tegel
with a
mortar, but with
in.
1 1
an
for
in.
trial,
gun, the attack being arranged to
correspond with the probabilities of hitting armour in coast defences.
2,190 yards was chosen as the attacking distance, and the corresponding
charge and angle of impact determined.
At
that distance the angle of descent of the
was
trial plate
1 1
in.
shell is 5°,
and the
inclined to that extent to the front, the angle of impact on
the curve surface being about 20°.
The
trial
plate
which was
ness,
in
was
10.8
front,
was
thickness was uniformly 0.7
Weight
Gun
:
in.
1 1
Distance
:
ft.
ft.
of plate 28.4 tons.
(28 cm) gun.
17.5 yards (i6 m).
i
wide by 16.4
.08
ft.,
ft.
long.
The
greatest thick-
and from the centre to the back the
42
[
Shot
II in. (28
:
Charge
57.3
:
cm)
lb.
weighted
chilled shell,
(26 kg)
P
P.,
]
;
total weight, 51 1.6 lb. (232 kg).
equivalent to 88
(40 kg) at 2,186 yards
lb.
(2,000 m).
Velocity of impact
:
366.5 yards (335 m).
Energy: 4,306 foot-tons (1,333
The
target
made
is
mt).
shown by
Fig. 15.
Fig. ij.
Profile
and
Iron
Trial Roof Plate of the Chilled
Position of Hits of the
Armour Battery for
8.3 in. (21
cm) Guns.
21/8/74.
Scale: 1.40.
Five
in all
hits
were made
;
of these the
two
first
only starred the
surface, the third cracked the plate as shown, the fourth cracked the plate
into
two
parts, the fifth
made no new crack but extended
to the
under surface, and from crack 4 broke
2.2 lb.
which
Summary
:
fell
off
the previous ones
a piece weighing about
through.
The Committee declared
the plate to
have displayed most
satisfactory powers of resistance, and moreover, considering the
small target exhibited
was
upon
by the
roof-plate
(-^
of the port plate),
improbable that a ship would be able to place so
it.
All the shot broke
up on
striking.
many
it
hits
[
8
.s
43
44
[
IV.
The Gruson armour had
J
Conclusions.
above described
in the
trials
exhibited so
striking a superiority to the guns, of that date that important orders for
and batteries were received from the Prussian Government.
Not only were all those valuable properties attributed by Gruson to his
material shown by the trial to be present, but others were brought to light
which, with respect to the applicability of the metal for armour, were of
turrets
The
not less value.
of the metal, on which
thrown
off at
From
had clearly demonstrated the extreme hardness
trial
all
the impinging shot glanced and broke up, being
large or nearly right angles.
this followed the great
energy of impact was not given
advantage that the greater part of the
off
on the plate, but was expended
in
breaking the shot into fragments.
The hoped
for effect of the soft layer
in the
armour.
under the hard surface was also
by the fact that only continued firing produced cracks
clearly demonstrated
same way, the absence
In the
blows can only be explained by an unusual
and, in fact, experiments have
shown
of effect of such powerful
elasticity of the
armour material,
that the chilled iron does possess this
to a high degree.
Whilst, on the one hand, this elasticity distributes the blow from the
point of impact over the whole mass, so
whose
of the projectile,
The curved form
for not only did
it
effect is in
of the plates
it
also absorbs in part the
energy
consequence considerably reduced.
was shown
to
be highly advantageous,
tend to effect the glancing of the shot, but also in
furtherance of the tendency of the metal only to crack radially, assists in
preventing loospned portions of the plate from being forced through to the
interior
;
in fact,
subsequent
And,
it
was observed that pieces already loosened were, by
hits, firmly
finally,
wedged again
into place.
the weight and thickness of the plates, which at
thought to be defects,
were shown
to
were
first
be advantages, as completely
separated pieces of the armour plates, after continued
displaced from
in
their positions,
firing, were not
and the gunners within the battery remained
complete security.
As already
stated, the trial of the first
Tegel turret had disclosed the
remarkable fact that chilled shells striking normally were shivered into
atoms without causing injury
of
importance; but
if
the shells struck at an
acute angle they broke up into a few large pieces, which produced surface
abrasions to a greater or less extent.
of the first
In consequence, the
Tegel turret was abandoned
shown analogous appearance
adopted seen
in fig. 17 p. 48.
in the second,
disclosed, the
flat profile
curve
and as the also here
rounded curved
profile
was
46
[
CHAPTER
1
III.
Firing Trials of G-rusou Chilled Cast Iron Armour
during the years 1882-1886-
TDETWEEN
1874 and 1882 no firing
armour, as
the
obtained
results
trials
were made against Gruson
had furnished
which to determine the necessary dimensions to
sufficient
resist
data by
the increasing
gun charges.
These were approximately determined by means
a
from the results
derived
formula,
= 0.294
/y/ foot-tons,
energy of the shot
d
is
of
previous
in foot-tons.
In
trials.
thickness of armour in
The above formula
ft.
an empirical
of
the formula
and foot-tons the
applies to coast
fortifi-
In the case of interior fortifications the resulting dimensions for
cations.
the various calibres required to be increased 10
Very soon, however,
in
%.
presence of the entirely altered conditions due
changes
in the velocity and quality of material of the projectiles, it
became a question whether the formula would still be of value. In 1874,
for instance* the heaviest projectile with which coast armour was subject
to attack was the ri in. shell with an energy of 5,685 foot-tons
now we
had to deal with the 12 in. with 16,150 foot-tons energy, entirely excluding
to
;
greater calibres,
the employment of which
will,
probably,
always
be
limited.
At
that time, also, chilled shells
than that of the soft steel shell
;
were used, as
now, hardened
their effect
steel shells
was greater
were employed,
with which chilled shells were no longer able to compete.
As
at the close of the last decade, important orders
from Austria,
trials
of
desirable
the
Italy,
and Holland
metal
were
for
armour
at the
These
projected.
were received
Gruson Factory, renewed
trials
appeared
to
be
from another point of view, as after the manufacture of these
heavy armour plates had commenced,
it
appeared impossible to avoid
[
46
]
the formation of shallow fissures on the hard surface during the operation
of casting.
Although
it
could be anticipated that these cracks, on account of their
would have no prejudicial
slight depth,
on the
effect
the less desirable to determine this point by firing
These
trials
and
fortifications,
fell
{i)
into
two
series
:
5.9 in.
in the case of
seemed not
inland
heavy naval guns against coast defences.
I.— Firing Trials against Chilled Cast Iron Armour
cations, in the years 1882-1885,
The
it
guns against
siege
(a)
plate,
trials.
hooped gun was used
for these trials,
Inland Fortifi-
for
being considered, as
the Tegel experiments, the largest calibre applicable for siege
purposes.
The
trials
formed a complete series
and showed how
was able to recover
in themselves,
the chilled armour, by improving the profile given to
it,
the superiority against shot, endangered by the improvement in steel
without increase of
shell,
size.
1.— Trial of Side-Plate for a Chilled Turret for two
26,7 calibres long, at Gruson's Firing
4.7 in. (12cni)
Ground
at
Guns
Buctau.
23rd December, 1882, loth January, and 27th April, 1883.
Scope and Programme of the
The
chill
on
object of
these
trials
was
to
Trial.
ascertain whether
the so-called
cracks occasionally to be found in chilled armour had any influence
its
endurance.
be thrown on
Target
:
A
The
this point
firing should therefore
side plate of a turret for
cracks of the nature
two
4.7 in. guns,
until light
containing
chill
mentioned, and being rejected by one of the
foreign officers inspecting the construction,
The
be continued
through the formation of fresh cracks.
construction of the turret in
was selected
question
for trial.
corresponded nearly
The cupola had an outside diameter of
shown in Fig. 4.
17 ft., and consisted of a port-plate, four side plates, and a roof -plate
These both together were 10.5 ft. in diameter, and at
in two halves.
to
that
the joining edge had a sighting embrasure for use with a manhole in
the roof.
The height
inside of
the turret from the upper edge of
the plates to the roller path was 11.8
ft.
Below the
roller ring the
47
C
]
space was closed by a masonry arch, differing from the arrangement
shown
Fig. 4.
in
the
5),
glacis
armour was formed
Both guns were placed
chilled iron.
(Fig.
The
axis
minimum
in
the bores being 4.4
of
ft.
six plates of
of
port-carriages C/80
25° elevation,
apart,
10° depression, and 3° lateral training could be given to the guns.
Turret and carriages were worked by hand gear,
revolution of the turret being
The
trial
made by
four
men
in
a complete
one minute.
was placed between two strong iron blocks of
supported by masonry and concrete, on the
plate
nearly similar weight,
same
level as the gun.
A
shot
Fig.
0.08
wooden screen with a small aperture for the passag'e of the
was placed in front as a protection against shot splinters (compare
In the plate was a chill crack a about 18 in. long by
29).
in. wide {see Fig. 17), and this crack was filled in with thin strips of
sheet iron, so as to be able to notice any widening which might be
brought about by the
The
firing.
plate also contained an irregular chill
from a crack in the mould
in.
the cracks
wide.
6.8
Gun: Short
broad.
about 0.47-0.51
in.
deep
were marked.
horizontally
ft.
cm) hooped gun 23 calibres long, mounted
in
ft.,
(15
10.5
ft.
Its
thickness 1.5
5.9 in.
measured
of the plate
height was 4.8
vertical.
ft.
maximum
b'
in.
Before commencing the firing the extremities of
Expanded, the surface
and
seam b which arose
was 0.06 in. deep and 0.08
was a deeper crack
Lastly, beneath b
and 0.08
it
;
actual
1
perpendicular
3.8 tons weight.
Prussian half-slide carriage.
Distance
Shot
24 yards (22 m).
:
Gruson and Ternitz
:
solid shot
and
steel shell 2,5 to 2,7 calibres long,
empty.
Charge
:
17.1 lb. (775 kg)
Velocity of Impact
Energy: 1,129.5
Round No.
Shot
:
seven channelled P. P.
488 yards (446 m), with shot weighing 76
lb.
(34,5 kg).
foot-tons.
1
Gruson's 5.9
Point struck
Angle
:
:
in.
Centre
hardened
steel shell 78.3
line of plate,
of impact: 81°.
(By angle
28
in.
of
empty.
lb.,
above lower edge.
impact
is
meant the smallest
angle between the shot's trajectory and the tangent to the curve
of the surface of the plate at the point struck.)
: :
48
[
An
Effect
:
indent, o.i
round mark
maximum
of
in.
]
depth, formed within a bright
about 6
of
some
in.
diameter, in which
concentric circular rings of compression were seen.
The
was
plate
entirely uninjured, the cracks a
and
nearly
3'
being
neither lengthened nor widened.
The
shot broke up in numerous large pieces.
Bound No. 2
Shot: As
round No.
in
Point struck
:
30
Angle
Effect
i.
6.3 in. left
from the centre
line.
over the lower plate edge.
in.
of impact: 79° 10'.
Exactly the same as No.
:
depth of 0.08
was
Crack
in.
b^
i,
an indent being formed of
showed no change, and the
maximum
plate itself
in all respects intact.
The
shot broke up into numerous pieces.
Bound No. 3
Shot
Gruson's 5.9
:
Point struck
:
The
in.
hardened
steel shell, 78.3 lb.,
37
in.
-Angle of impact: 68°
above the lower edge.
40'.
Fig.
Profile
and
two 4.7
in.
*
The same
NOTE. —The
and horizontal
*
(12 cm) Guns.
Scale
:
17.
Position of hits of the Trial Side-Plate of the Chilled Iron
Armour Turret for
Effect
lines.
as in rounds
i
trial-plate, like all others
These
lines
are
shown
:
23/12/82, lo/i
surface of the Plate
is
shown
as
and
27/4/83.
1.40.
and
2,
an indent 00.8
in.
deep, marked
used later on, was divided into squares by vertical
make our explanations more
in the sketches as they
easily understood.
The
empty.
centre line.
if it
was perfectly
flat.
49
[
by a bright spot 6
in. in
]
The compression
diameter.
rings were
again noticeable.
The
The
As
effect
were unchanged, and the plate
intact.
shot broke up.
5'
had been shown to be absolutely without prejudicial
plate,
crack a was subjected to a similar, and even more
the crack
on the
severe
old cracks
trial.
Eonnd No.
Shot
4.
As
:
before.
Point struck
:
26
in.
to left of centre line.
46
in.
above lower plate edge.
5
in.
under crack
a.
of impact, 50" 5'.
Angle
The
was an indent 0.06 in. deep and about 3 in.
in diameter, marked by an oval bright spot which, however, had
Crack a was
no rings of compression, as before noticed.
Effect
:
sole result
unchanged, the sheet-iron
as before the
filling-pieces entirely closing the crack
hit.
Shot broke up.
Round
No. 5
Shot
:
as before.
Point struck
Angle
:
26
above lower plate edge.
6
in.
above lower end of crack
34°
:
centre of the part struck was marked by a scratch on the
and edge
In
long.
in.
a.
20'.
iron filling-wedge
0.04
of the centre line.
in.
of impact
The
in. left
58
of the crack about 0.08 in.
addition,
a bright spot about 4
going upwards on the plate with an indent about 0.0 1
Crack a entirely unaltered, and
Round No.
Shot
Point struck
:
g
in. right of
20
Angle
Effect
of
:
fully closed
by the
broad,
in.
iron
deep.
wedge.
loth January, 1883.
6:
Gruson's soft forged 5.9
:
still
deep and
in.
impact
in.
:
in. solid steel shot,
80
lb.
in weight.
centre line.
above lower plate edge.
82°.
A bright splash
compression.
Shot broke up.
8 in, in diameter
;
no indent and no marks of
:
50
[
Round No.
Shot
]
7
Gruson's forged and hardened 5.9
:
80
Point struck
:
34
in. left of
55
in.
Effect
weight
impact: 41?
of
A
:
it
crack
a.
20'.
bright splash
As
centre line.
above lower plate edge.
in. right of
3
Angle
solid steel shot,
in.
lb.
no
;
visible indent
;
crack a unaltered.
seem that crack a would be changed by further
did not
the remaining rounds were placed on the middle line of
firing,
the plate.
Round
No. 8
Shot
Gruson's 5.9
:
Point struck
:
Effect
impact
of
An
:
in.
weight 86.7
lb.
above lower plate edge.
78°
:
indent 6
pression
solid steel shot,
15 in. left of the centre line.
26
Angle
hardened
in.
20'.
in diameter,
in.
rings
visible,
also
and 0.08
a fine hair
in.
deep, a few com-
crack
c
6
in.
long,
beginning close above the point of impact, and running to that
round No.
of
dotted line in Fig. 17).
2, [see
Shot broke up.
Round
No. 9:
Shot
As
:
in
Point struck
Angle
:
8.
20
in. left of
27
in.
centre line.
above lower plate edge.
impact: 77° 30'.
of
A
Effect:
round
bright splash, extending to
pression marks.
Hair crack
mark
8.
No
indent or com-
c unaltered.
Shot broke up.
Round No.
10:
Shot: Gruson's hardened
Point struck
:
9
27.6
of impact:
Angle
Effect
:
Crack
in.
79°
weight 81.6
lb.,
empty.
centre line.
above lower plate edge.
10'.
Impact mark 0.2
c closed up.
crack running into
with
steel shell,
in. left of
c.
Shot broke up.
b^
4
in.
in.
deep, and a fine hair
long, but not apparently connecting
51
[
Round No.
Shot
11:
Gruson's 5.9
:
Point struck
Angle
Crack
c
hardened
79°
:
steel shot,
centre
weight 81.2
lb.
line.
above lower plate edge on No.
in.
impact
of
:
in.
in. left of
9
:
28
Effect
1
10.
10'.
unaltered and closed up.
Impact mark deepened to
0.3 in.
Shot broke up.
Round No.
Shot
12
Gruson's 5.9
:
Point struck
24
Angle
Effect
of
in.
hardened
steel shot,
weight 81
lb.
8 in. left of centre line.
:
above lower plate edge.
in.
impact
84° 30
:
'.
A bright splash crack c unchanged.
A new fine hair crack ^ 12 in. long,
;
:
the middle
and
line,
in the centre of chill
beginning 5
crack
in. left
of
b^.
Shot broke up.
Round
No. 13:
Shot Gruson's 5.9
Point struck 5 in.
:
:
in.
hardened
left of
steel shot, 81.2 lb.
centre line.
above lower plate edge.
Angle of impact: 68° 15'.
40
Effect
in.
A bright splash
:
;
crack
d lengthened about
28
in.
Shot broke up.
Round No. 14:
Shot
Ternitz 5.9
:
Point struck
Angle
Effect
of
:
:
in. steel shell,*
empty, weight 82
18
in.
right of the centre line.
30
in.
above lower plate edge.
lb.
impact: 78°-
Indent 2.3
in.
long,
1
in.
wide, and 0.2
in.
deep.
No com-
pression markings were visible.
The
Round No.
shot broke up.
15
Shot: Ternitz 5.9
Point struck
*
The
:
in. steel shell,
empty, weight 81.8
16
in.
right of centre line.
36
in.
above lower plate edge.
steel shell
of the Ternitz works
is
lb.
the armour-piercing shell adopted in Austria,
and displays superior hardness
Untempered
tempered
shell is to
steel shell was not used subsequent
be understood.
to this, so that
by the term "
steel shell
:
52
[
Angle
impact
of
Effect
A
:
]
65°.
:
round mark
in.
i
diameter and 0.09
in
in.
No
deep.
concentric lines.
Shot broke up.
Round No. 16
Shot
Ternitz 5.9
:
Point struck
Angle
of
in. steel sheel,
empty, weight 82.71b.
19
in.
right of centre line.
33
impact
in.
above lower plate edge.
:
70°.
:
Effect: Indent 1.8
in diameter,
in.
and 0.2
in.
No
deep.
concentric
lines.
Shot broke up.
Round No.
Shot
17
Ternitz 5.9
:
Point struck
Angle
10
33
impact
of
Effect
:
in.
and
2
f
4
and 0.2
in diameter,
in.
in.
mark
long, towards
in.
lb.
line.
above lower edge.
Impact mark
:
empty, weight 83.1
centre
72°.
:
hair cracks e
4
in. steel shell,
in. right of
long towards mark
in.
deep, 2 parallel
and one
2,
g
3.5 to
15.
Shot broke up.
Round No.
Shot
18:
Ternitz 5.9
:
Point struck
:
in. steel shell,
31
in.
of impact
Effect
of
:
:
hits
i, 3,
and
mark 2 in. in diameter and 0.3 in. deep.
The crack made by round 10 was extended to the lower edge
the plate, and that caused by round 13 extended to the upper
edge, thus forming a vertical
through the plate and divided
of the crack caused
The
:
17.
73°.
A
plate
Summary
lb.
above lower edge,
between
Angle
empty, weight 83.1
5 in. right of centre line.
it
by round 18
is
the object of
the
of crack
trial
shown
in Fig.
d breaking
was reached,
departure from the middle of the
it
halves.
The lengthening
1
7
by dotted lines.
shot broke up.
With formation
deep)
crack which passed right
two
into
may with
chill
the plate into two halves,
for as this crack took its
crack
b\
(which was 0.5
certainty be considered that the chill crack
entirely without influence in determining the formation of d.
in.
was
[
It is
the
]
further noticeable that 3 hits
fell
in close
proximity to
crack a without either lengthening or widening
chill
want
53
of influence
on the part of the
chill
cracks
This
it.
—which, considering
their very small depth in proportion to the thickness of the plate,
was reasonably
to
be expected
—was confirmed by
all
subsequent
experiments.
As regards
the behaviour of the plate the following
is
to
be
noted
By examination
of the target
it
was found that the plate,
struts, had moved about
through failure of the front supporting
towards the front and,
0.2 in.
in
consequence, had
lost contact
with
the lateral supports.
This, probably, had had a very great influence in diminishing
the resisting powers of the plate during the later rounds, a conjecture which had
edge
sequently, finally
plate
of
all the more weight, inasmuch as the upper
was not supported from the first, and, conwas quite free to move.
of the plate
However, notwithstanding this unfavourable condition, the
had withstood 18 hits, with an energy of 20,329.6 foot tons,
which
14,
with a total energy of 15,810.9 foot tons, had struck
within a small pentagonal space 2.5 square feet in size, before
a through crack was formed.
The
plate
was
1
8th round produced the
in other respects so
the results of the Tegel
breach
through crack, but the
completely intact that, judging by
trial, it
would
still
take a long time to
it.
All the shot broke
considerable
actual,
first
up on impact, but the Ternitz shot showed
superiority to the
Gruson
though small, indents into the
shot,
plate,
been previously observed either with Gruson
as
they effected
which had not
steel
or
chilled
shell.
D
54
[
2.
]
Armour Battery
Trial of a Port-Plate of a Chilled Iron
5.9 in. (15
On
cm) Guns, 23
for eight
calihres in length.
Gruson's Firing Ground at Buckau,
i6th July, 1883.
Object and Programme of the
Test of the armour-metal by means of
small space on the plate from the 5.9
government
the terms of the
Target.
—The
five
Trial.
concentrated on a
hits
hooped gun,
in.
in
accordance with
contract.
armour battery
which the
for
trial-plate
was intended
differed chiefly from the construction shown in Figs. 2 and
was divided
in that the port plate
The
was composed
battery
and the necessary foundation,
The breadth
was
of the port
roof plate 4.6
into
two halves
of 16 half port plates, g
pivot,
and roof
3,
{see Fig. 18).
pillar,
plates.
of the port half plates at the level of the centre
5.6
ft.
that of the pillar plates 2
ft.,
The
latter
had a length
of 14.
ft.,
1 ft.^
and of the
and rested
rear on so-called support plates, borne on one side by iron
in
columns and on the other by masonry
The
led to the casemates.
and
and the height
earth,
of the
front
was
9.2
1
ft.,
were protected by masonry
the battery from base to upper edge
of
The guns were mounted in minimum
The distance between port and port was
ft.
port-carriages C/80.
13.
The space between
pillars.
roof plates
angle of elevation 25°, depression 10°, and training 50°.
The
target
was constructed
as
if
part of the battery, and
consisted of two half port plates, a pivot block, two
three roof
plates,
all
pillar,
and
reposing on both sides against masonry.
was a concrete glacis up to the port, and a stout
wooden screen in front was placed to catch splinters of shot {see
In front there
Fig. 29).
The
half port plate
a dimension
of
5.9
ft.
subjected to attack had on the curve
horizontally
perpendicular height was 6.2
ft.,
and
8.9
maximum
ft.
vertically;
thickness 1.9
ft.,
the
and
weight 10.3 tons.
Gun
:
Italian 5.9 in., 23 calibre gun,
G.C.R,
(ret.)
in
Gruson's
minimum
port carriage C/80.
Distance
:
42.6 yards (39 m), the
gun being
directly opposite the centre of
the port.
Charge: 16.3
lbs.,
Fossano progressive powder, 0.8
—
I
in.
55
[
Shot: Krupp steel 2.8 calibre
Velocity of impact
Energy
impact
of
Round No.
Shot
:
:
weight 85.3
shell,
lb.
(38.7 kg) filled.
about 454.7 yards per second.
14.4 foot-tons.
1 1
1
As above, weighted with
:
Point struck
ig
:
in.
3.5 in.
Angle
Effect
]
of impact
sand.
line
above the
OA.
OB.
line
63°.
:
Indent 2
:
from the
in. in
diameter, and 0.4
in.
deep.
Shot broke up into numerous pieces.
Eonnd No.
Shot
:
2
As
before
Point struck
:
4. in.
Angle
of
impact
An
Effect:
from the
line
OA.
under the
line
OB.
19.7 in.
:
74°.
:
oval indent, 7.4
in.
deep, round which was a
5
fine
1.2 in.
and
cracks,
deep
;
c,
a
down
long, about 2 in. broad
in the lip of the port
1.2 to 1.4 in.
surface abrasion about 0.2
flat
to left
hair crack
and
11
(2
in.
in.
deep)
;
d,
in.
in.
3.5
long; d, hair crack 6
a short hair crack
in.
deep,
long,
long,
/.
Shot broke up.
Fig. 18.
Profile
Iron
and Diagram of
hits
of the Trial Port Plate of the Chilled
Armour Battery for Eight
Scale
fl
'
"
^1
5.9 in. (15
:
cm^ Guns.
16/7/83.
1.40
\
D2
56
[
Round No.
Shot
3:
Krupp
:
steel 5.9 in. shell, filled,
Point of impact
impact
of
Effect
A
:
in-
in.
weight 85.3
lbs.
OA
line OB
line
above
61 '^ 30'.
:
round indent 2.4
crack 7.4
/, 5
from
in.
31.5
:
6.8 in.
Angle
]
long and
diameter, and 0.6
in. in
0.6
deep.
in.
reaching to hit No.
in.,
2.
A
fine
Hair crack
long.
Shell exploded.
Bound No. 4:
Shot
As
:
before.
Point struck
30.4
:
in.
4. in.
Angle
Effect
impact
of
Indent
:
:
from line OA.
under
line
OB.
73°.
o.i in.
maximum
depth.
No
cracks.
Shell exploded.
Round No.
Shot
5:
Krupp
:
Point struck
steel shell filled with sand,
:
Effect
impact
of
:
:
in the centre of the four previous hits.
plate
seemed not
Hair crack h 4
deep.
in.
lengthened about 21.7
of
A,
69°.
Indent 0.2
back
lb.
B,
line
and nearly
Angle
O
26.8 in. from line
on the
weight 85.3
{g), also a
in.
a crack in the direction a
to connect
in.
Crack
long.
somewhat widened.
—g,
/
At
which, however,
on the outside with either a nor
i.
Shot broke up.
Summary:
The
space of
plate
0,86
had withstood
square
ft.
conditions of the contract.
cylindrical part in
many
;
five hits
concentrated on the small
and consequently had
fulfilled
the
All the shot broke up, the base
and
pieces, the
head and point were shivered
in shapeless atoms, coloured blue by the heat.
No
superiority in effect of the filled over the weighted shell
could be observed.
57
[
3.
]
Armour Battery
-Trial of a Port Plate of a ChlUed Iron
(15 cm)
5.9 in.
On
Gnns, 23
calibres
for six
long.
Gruson's Firing Ground at Buckau,
1
8th August, 1884.
Object and Programme of the
Proof of the armour metal by
five
Trial.
rounds from the 5.9
hooped gun
in.
corresponding to the terms of the contract with the government.
Contrary to No. 2
trial,
the hits to be distributed over a larger part of
the plate's surface, so as to note the difference of result.
Target
The armour
:
was
battery for which the trial-plate was intended
exactly
of
similar
construction
that
to
under
described
of twelve half port-plates, seven pillar,
and was composed
and the corresponding
foundation pivot and roof-plates.
other respects the des-
No.
number
only differing in the
2,
of guns,
In
cription previously given applies also to this battery.
The
composed
and
target,
of
three
to
two
be attacked
half port-plates,
roof-plates.
It
as
in
one pivot-block, two
was supported
as
No.
in
protected by a similar front screen against splinters.
half port-plate
under No.
2.
was attacked. Its dimensions were
Weight 10.3 tons.
The same gun,
Ronnd No.
Krupp
85.3
The
and
right
same
the
as
charge, and distance were employed,
steel
:
21.7
:
in.
(15
impact
A
depth
:
from
line
under
line
in.
8.3 in.
of
5.9
cm)
shell
weighted with sand to
lb.
Point struck
Effect
pillar^
2,
1:
Shot:
Angle
was
warfare,
actual
77°.
bright splash, 5.5
;
OA.
OB.
in.
in
diameter and 0.4
in.
maximum
a piece of the steel point was found in the metal near
the centre of the splash
;
other small portions of the shot were
similarly found near the point of impact.
The
shot broke up into numerous minute pieces.
:
58
[
]
Fig. 19.
Profile
of the Plate under trial for the Chilled
Battery for six 5.9 in. (15 crn) Guns. 1 8/8/84.
and Diagram of
Iron
Armour
hits
Scale
Round No.
Shot
before.
Point struck
impact
of
in.
35.5
:
in.
4.7
Angle
1.40
2
As
:
:
from line OA.
underline OB.
74" 30'.
:
Indent 5.9 in. diameter and
same a surface abrasion about 26.4
Effect
:
depth 0.8
A
in.
fine
2.8
in.
in.
deep.
Round the
maximum
diameter, and
crack a from the point struck to 4
in.
from the right edge.
The back
was
of the plate
Shot broke up
;
intact.
the pieces of shell
showed very great hard-
ness, exceeding that of the first round.
Bound No
Shot
:
3:
As
before.
Point struck
:
in.
from the
10
in.
above the
Within the
Angle
of
Effect
:
OA.
OB.
abrasion caused by Round
60
impact
:
line
line
II.
54° 40'.
Indent of 6
in.
an abrasion of 0.8
diameter and 2
in.
maximum
in.
depth
depth,
;
round the same
joining that formed
59
[
by Round
A
2.
vertical crack
d
c,
two
stretching to 8
of
right
plate
:
edge
;
formed by Round
Crack a was
under
the level of Shot
from upper edge
i,
and one
II.,
a
;
at the lower
edge
III.
visible,
running to 7.4
this a fine horizontal
crack 14.8
in.
in.
from the
long, about
but not visible in front [see Fig. 20).
Hardness about the same as Round
Shot broke up.
Bound
in.
;
a crack
II.
radial hair cracks at hit
of the abrasion
Back
impact point to crack a
crack b from
in the direction of hit
In addition,
]
I.
No. 4:
Shot
:
As
before, but
Point struck
:
18
in.
filled.
from the
i8'5 in.
Angle
of
impact
:
OA.
line OB.
line
above the
42° 38
Mark blackened by powder, 79
Effect:
right part of
which a
Back
5'5 in. long.
indent of
Two
depth; no abrasion.
and
flat
radial
of plate
in
in.
3T
in.
diameter,
at
lower
diameter and 0*4
hair cracks, e
and
in.
f, 8'7 in.
unchanged.
Shell exploded.
20.
Fig.
Back of the Trial Plate of the Chilled Iron A rmour Battery for
(15 cwi) guns, after the fifth shot,
Scale
:
six 5.9 in.
\'&l'iil'&\.
1.40
Bound No. 5
Krupp's 5.9 in. (15 cm) steel shell, weight 84.1
Point of impact: 24 in. from the line O A.
13.4 in.
Angle
Effect
of
:
impact
:
above the
line
O
lb-,
burster 1.3
B.
50°.
Flat indent 4
in. in
diameter, and 0.5
Hair crack/, lengthened to
hit III.
in.
deep.
lb.
60
[
A
]
fine crack g, 9.2 in.
Back
of plate unaltered.
Shell exploded.
Summary The
:
had complied with the conditions, but no
plate
could be drawn with
trial
No.
were apparently the same.
the
individual
hits
—as
The
and
indents,
also the effects of
rounds 2 and 3
instance,
for
parallel
although the conditions of attack
2,
—were
unexpectedly great, so that the suspicion was entertained that the
armour
[plate
was
on the 16/7/83. This,
pieces taken on casting the plate,
softer than that tested
however, was refuted by the test
and
round No.
also
gave such a
i,
notwithstanding
less effect that
greater angle of impact,
its
undoubtedly there were differences
in
the quality of the shot.
The
superior effect of rounds 2 and
comparison with
3, in
the trial of the previous year, pointed to a better
having
4.—Trial of a
up on
All the projectiles broke
projectile.
shell
less effect
two
On
striking, the
of
filled
than those not charged.
Plate of
Glacis
quality
a
Chilled Iron
Armour Turret
for
calibre 4.7 in. Guns.
23-2
Gruson's Firing Ground at Buckau,
1
2th February, 1884.
Object and Programme of
Test of the plate by
five shots
from the 5.9
Trial.
in.
hooped gun, as
also of
the dimensions prescribed for the armour.
Target
:
The
turret for
corresponded
in
which the plate under
and
dimensions
previously described for two 4.7
'^"
Profile of the
the
Chilled
two
^'"
The
Glacis-Plate for
Armour
5.9 in.
Turret for
in.
was destined
trial
construction
turret
guns, 26.7 calibres long.
glacis
armour was composed
of
"
The maximum diameter
was 23.9 ft.
Each
Guns.
the
to
armour
extreme breadth of 10.2
ft.,
of
the glacis
plate
had an
measured on
the chord.
The
other dimensions are given in the
Fig. 21.
The
-i-
cast-iron
trial
plate
was
fixed
supporting-plates
between two
resting
against
61
[
]
masonry, the lower part being protected by granite blocks, and security
against shot splinters was given by the usual
The weight
Gun
Italian 5.9 in.
:
in a
Distance
Shot
of the trial plate
:
:
in front.
10.5 tons.
cm) hooped gun, 23 calibres long G. C. R.
(ret)
Gruson minimum-port carriage, C/80.
49.2 yards.
:
Krupp
Charge
(15
was
wooden screen
steel sheel, 2.8 calibres,
16.3 lb. progressive
Striking velocity
Striking energy
:
lb.
0.8 in.
454.7 yards per second.
1 1
:
weight about 85.3
Fossano powder
14.4 foot-tons.
Fig. 22.
The Glacis Plate for an Armour Turret for two 4.7 m. (12
after the 6th round.
1
cni)
Guns
2/2/84.
From a Photograph.
Round
1:
]Vo.
Shot:
Krupp
steel shell, 2.8 calibres,
weight about 85.3
lb
,
weighted
with sand.
Point struck: The shot struck 17.7
glacis,
upper edge
Effect
:
A long
of the glacis.
splash.
Shot broke up.
Bound No. 3:
Shot As before.
:
in. in
glanced, and then grazed
front of the
the
plate
6.3
armour on the
in.
above the
62
[
Point struck
Angle
Effect
.
left,
2.4 in.
above the glacis edge.
The only
No
near the centre
2.4 in.
line.
impact: 41° 25'
of
:
]
result
was a bright splash
of o-2 in.
maximum
depth.
hair cracks found.
Shot broke up.
Round
No. 3:
Shot
As
:
before.
Point struck
:
above edge of
3.2 in.
Angle
Effect
of
impact
A
:
near centre
in. right,
1 1
:
38° 40'
bright splash of 0.4
hair cracks of 6
Round No.
after
line.
glacis.
in.
maximum depth
;
four star-shaped
greatest length round point struck
in.,
3, tvio
hair cracks, 4 in. long,
showed
;
also,
at Hit 2.
Shot broke up.
Round
No. 4:
Shot
As
:
before.
Point struck
:
12.6 in. left from the centre line.
above edge of
1.6 in.
Angle
Effect
impact
of
:
The
:
glacis.
40°.
shot struck the upper edge of the covering glacis, making
a cavity there 2.8
in,
deep, also an indent 0.4
in.
deep on the plate
four short hair cracks, of which one connected with hits IV.
and
;
II.
Shot broke up.
Round No.
Shot
:
5:
As above.
Point struck
:
27
in.
right of centre line.
0.8 in. above glacis edge.
Angle
Effect:
impact: 46°
of
A
20'.
cavity 3'i in. deep in the upper edge of the covering glacis.
Indent on plate about 0"4
Hair crack formed by
in.
greatest depth.
hit 3
lengthened, joining hits
III.
and V.
This was the only crack whose depth could be probed.
Its
greatest depth was 1.8 in.
Also two short hair cracks.
Shot broke up.
Round
No. 6:
Shot
:
As
before, charged.
63
r
Point struck
3.5 in. right of the centre line.
:
above glacis edge,
5.5 in.
(between
Angle
Effect
impact: 41°
of
:
hits
II.
and
was a sharp
below to the right a
;
III.).
30'.
Indent, in which
depth
]
mark
chisel
0.3
in.
in greatest
Two
slight abrasion 0.2 in. deep.
fine hair cracks.
The
effect of this hit
was evidently somewhat greater than
the previous ones.
Shell burst.
Sumniary
:
The
resistance of the plate had proved
Of the
fine hair cracks formed, only
with a fine probe.
The
Its
mean depth was
amply
sufficient.
one could be measured
1.2 in.,
maximum
1.8 in.
smaller effect of the shot on the armour compared with
the previous trials showed without question that the effect varies
in inverse ratio
Trials
and
this,
adopted,
with the size of the angle of impact.
made
in
at the
which,
from
departing
approaches that used
The
same time against coast armour confirmed
the profile shown in Fig. 25 was
consequence
the
previous
experience,
in the first plates tried at Tegel.
shot broke up as in the earlier trials into small pieces,
showing an uncommonly hard
touched with a
material,
which could not be
file.
5.— Trial of a Port Plate of a CMUed Iron Armonr Turret for two
4.7 m. (12
On
cm) Guns, 33.5 Calibres long.
Gruson's
Firing
Ground
at
Buckau,
28th August, 1884.
Object and Programme of the
Test of the material by
five shots
Trial.
from the 5.9
in.
(15 cm)
hooped
gun.
The
same turret, of which a glacis
was tried in the last experiment. It was fixed with two
and a roof-plate, so that the whole target formed nearly a
turret.
At the back the target was supported by masonry
plate belonged to the cupola of the
plate
side
half
pillars, tied to
A wooden
the plates
by three
cast-iron struts.
screen with earth was provided in front to catch shot splinters.
:
64
[
At
]
the level of the port the plate had a radial thickness of
expanded width was
greatest
pendicular height, 4.9
Gun:
23
Italian,
calibre,
minimum
Distance
49.2
:
ft.
10.6 ft.;
1.7
height, 6.9
Its
ft.
ft.;
per-
weight 14.6 tons.
;
5.9 in.
(15
cm),
gun, on
hooped
Gruson
port-carriage, C/80.
gun being normally opposite the centre
yards, the
of
the plate.
Shot
:
Krupp
weight about 85.3
2.8 calibre steel shell,
and
steel shell,
Charge: 16.3
progressive powder, Fossano, 0.8
lb.
lbs.
also
;
Gruson
steel shot.
solid
—
i
in.
About 4S4.7 yards per second.
Striking energy: About 11 14.4 foot tons.
Striking velocity
Round No.
Shot
:
1
Krupp
:
Point struck
steel shell,
:
11.8
weighted to 85.3
in. left
lb.
of the centre line.
20.5 in. above lower edge of the plate.
Angle
Effect
of
:
impact
An
this
81° 20'
indent about 8
to the
depth.
:
No
in. in
diameter and 3.5
in.
port a splintering of the surface 4.3
deep.
in.
From
in greatest
crack visible on the exterior of the plate.
The back
of the plate
showed a
fine horizontal crack 15.7 in.
long, beginning at the level of the part struck at the
port and running to the right {see Fig. 24).
Shot broke up, exhibiting extreme hardness
of material.
Fig. 23.
Profile
and Diagram of
Armour
of the trial Port Plate of the Chilled
Turret for two 4.7 in. (12 cvi) Guns. 28/8/84.
hits
Scale
:
1.40.
65
L
Bound No.
Shot
2
As
:
before.
Point struck
12.6 in. right of centre line.
:
over lower plate edge.
in.
34.7
Angle
J
of impact: ']0° 35'-
Effect
Indent 8
:
to this
diameter and
in
in.
1.2 in.
deep; from above down
an unimportant abrasion, 3 radial hair cracks, of which
one, «, stretched 7.1
Back
about 2
down
the plate
of
in. in
in.
:
to the
the
left.
horizontal crack
was lengthened
the direction of the lower edge.
Shot broke up.
Ronnd No. 3
Shot
Krupp
:
Point struck
shell, as before, filled.
25.2
Angle
Effect
impact
of
right of centre line.
7. 1 in.
:
above lower plate edge.
in.
84°, 45 '.
:
Indent and slight abrasion of
:
7.1 in.
(1.2 in.
diameter) fixed in plate.
Crack a
into hit
edge
i
diameter.
Radial crack
and running over
hit 2 to 7.1 in.
Point of shell
down
to right.
from the upper
of plate.
Back
of plate
:
crack a showing as a hair crack.
Shell burst.
Bound No. 4
Shot
:
As
round.
in last
Point struck
:
6
Angle
Effect
in.
over lower plate edge.
impact: 68° 40'.
of
:
centre line.
in. left of
35.8
Indent and slight abrasion
;
point of shell fixed in
plate
cracks b and c; crack a lengthened to upper edge of the plate.
Back
of plate unaltered.
Shell burst.
Bonnd No. 5:
Shot: Krupp flat-headed steel
85.3
lb. (flat of
Point struck
Angle
Effect
:
On
of impact
:
Indent 8
:
head 3
in.
shell 5.9 in,,
weighted with sand to
diameter).
centre line, 46
in.
above lower plate edge.
.52°.
in.
diameter and 2.4
above downwards to
hit.
in.
deep, slight abrasion from
::
C
66
]
Crack d from point struck down to hit 3, and upwards
towards and joining crack a; a radial crack e to a.
Back
unchanged.
of plate
Shot broke up.
The programme was now completed, but
little, it
Eonnd
was decided
as the plate had suffered but
to continue the firing with four shots in hand.
No. 6
Krupp
5.9 in. steel shell,
Point struck
:
9
in. left
weighted to 85.31b.
of centre line.
43.7 in. above lower plate edge.
Angle
of impact
Effect
57°.
:
Indent 4.7
:
abrasion,
diameter and 0.8
in. in
and a
in.
deep
;
beneath, a slight
radial crack in direction of hit 5.
Shot broke up.
Fig. 24.
Back of Trial Plate
of Chilled
Guns
Armour Turret for
Shot
\.'^in. (12 cni)
after ninth hit, 28/8/84.
Scale
Eound No.
two
:
1.40
7
As
:
round
in last
Point struck
:
0.8 in. right of centre line.
35.4 in. above lower plate edge.
Angle
Effect
of
:
impact
A
put,
:
69" 50'.
wedge shaped
maximum
piece,
bounded by cracks,
Also a chiselling of surface, 4
cracks a and b.
Back
of plate
b, c
and d knocked
thickness 4.7 in.
unchanged.
Shot broke up.
in.
deep, at point of junction
of
67
[
Round No.
Shot
8:
Gruson's 5.9
:
Point hit: 13
Effect
in. steel shell,
in. right of
23
Angle
]
in.
79.8
weighted with sand.
centre line.
above lower plate edge.
of impact: 82° 50'
Oval indent about 2.8
:
abrasion around hit
;
in. in
two
under edge
to
of plate
crack
f
diameter and 0.4
A
2.
fine
deep.
Slight
down-
crack, /, from Hit 3
of the plate.
The two cracks lengthened
:
in.
radial hair cracks. 6 in. long,
wards, and one towards Shot
Back
lb.,
to
edges of the plate
;
visible in rear.
Shot broke up.
Round
No. 9:
Shot Gruson's
solid steel shot, 80 lb.
:
Point struck
On
:
centre line.
19 in. above lower plate edge.
Angle
of
Effect
:
impact
:
Indent 5.9
Back
82° 30'
in. in
of plate
:
The
plate
in.
deep.
the piece of plate bounded by cracks a
:
/ forced back about
The cylindrical
Summary
diameter and 0.8
0.04
part of the shot
was found
close to the plate.
had shown a satisfactory resistance
All the cracks, as
and
in.
far as
in
every respect.
could be determined, ran across
nearly radially to the rear, and in consequence even the broken
and loosened parts
of
plate
showed a more
resistance to the blows of the shot.
by shot
9,
to drive
it
than
sufficient
This was especially seen
which separated a piece of plate without being able
to the rear.
As seen by
the sketch of the back of the plate after the
9th round, the protection was
still complete, although these
9
rounds had been concentrated between the ports on a space
6.9 square ft. in superficies.
Of the Krupp
a superiority of
shell,
effect
the
first
over the
showed extreme hardness, and
others,
favoured by the nearness of the port.
which however, was
—
68
[
6.—Trial of a Side Plate
two
Armour Turret
Chilled Iron
for a
cm) Guns, 26.7
4.7 in. (13
On
]
for
calibres long.
Gruson's Firing Ground at Buckau,
19th
and 20th January,
1885.
Object and Programme of the
Trial.
Test of a side plate for the above-mentioned turret by 15 rounds
(eventually increased to 20)
short 5.9
in.
The programme
The
hardened
of
steel shell
from the Prussian
hooped gun.
:
took place with hardened Ternitz
firing
charge of 15.2
ran as follows
P. P. C/68, the equivalent
lb.,
of 1,039 yards,
and was
steel
gun charge
ammunition
directed, to save
with a
shell,
for a
only,
distance
on the
left
half of the plate.
And
was
the endeavour
to
be made by grouping the rounds
i
to
5,
as
shown by hits i, 3 and 5, to make a vertical crack dividing the plate into
nearly two equal parts, so that the following firing should give a result
quite free from objection.
The gun was placed
for the first six rounds, as well as for
No.
normally opposite the centre of the plate, and for the remainder
moved 24°
And
If
it
20,
was
to the left.
of the intended 20 hits 5 to
the plate
was not breached
be with flat-pointed
after the 15th
steel shot.
round (that was about 10
shots per square yard of the vertical projection of the target), and
no loosening of parts at the back injurious to the
showed
stability of the turret,
the resistance to be considered sufficient.
Five additional steel shells were then to be
Target
:
The
ponded
cupola.
turret for
in
which the
the main with Fig.
The
and consisted
turret cupola
The two
ft.
sights
through a manhole.
upper edge
4,
plate
and the
trial
concluded.
was intended
corres-
but differed in the profile of the
had a maximum diameter
of a port plate,
roof plate of II.2
trial
fired,
of 19.7
ft.,
4 side plates, and a wrought-iron
diameter and 4
in. thick.
were placed on the roof and were used
The height
inside
of the cupola plates to the
the
edge
turret
from the
of the roller
ring
I.
69
]
The arrangement of the lower spaces corresponded
The ring of glacis armour consisted
that shown in Fig, 4.
ten chilled iron plates.
The two guns were mounted in
was
to
of
1
1.2
ft.
minimum-port carriages C/80,
and
admitted
25°
of
their
10°
elevation,
axes being 4.4
apart,
ft.
and
depression,
3° side
Turret and carriage were worked by hand, the former
training.
being worked from an adjoining casemate by a capstan, by
means
which four men turned the turret through 360°
of
in
one minute.
The
plate
trial
differed
considerably in form from those
previously tried, being constructed in accordance with the data
established
The
by these previous experiments.
profile
ground angles
The
trial
of
was considerably
so
flattened,
level
impact superior to 46^° were impossible.
was supported between two
plate
side
forming thus together nearly half a cupola.
plate,
on
that
and a roof
In
rear
glacis
it
The
rested on masonry pillars supported by cast-iron struts.
armour was protected as before with concrete blocks to the
upper edge, and a screen was provided
level of its
in front to
catch splinters of shot.
The
thickness and dimensions of the
The
Fig. 25.
glacis 12.5
ft.,
and
at the
The weight was
Gun
:
Prussian short 5.9
Distance
:
trial
plate are
shown
in
greatest width expanded was, at the level of the
upper plate edge
7
ft.
19.6 tons.
in. (15
cm) hooped gun, 23 calibres long.
39.4 yards.
For the
first
seven rounds the gun was placed normally
opposite the centre of the plate
;
for the
other rounds
it
was
inclined at an angle to the left of 24°.
in. steel
Shot: Ternitz, 5.9
76
shell 2.5 calibres
Charge: 15.2
lb.
P. P. c/68
—equivalent
Velocity: About 431,7 yards.
Energy of impact About 687
:
Round No.
long, weighted with sand to
lbs.
to service charge at 1,093 yards.
foot tons.
1.
Ternitz steel
Point struck
edge.
shell,
:
55
as above.
in.
left
of centre line, 37.4 in.
above glacis plate
[
Angle
of impact:
]
340 15'
Effect: Indent 4 in. broad,
No
70
and
0.3 in. deep.
cracks.
bo
Shot glanced upwards and
split into
many
small pieces, which
showed, as did also the subsequent
degree of hardness.
rounds,
a great
71
[
Bound No.
Shot
2:
Ternitz steel
:
Point struck
Effect
impact
of
from
Indent 4.3
:
No
Round
lb.
left
weight.
edge
above edge of
40"
:
76
shell,
in.
54.3
:
22.5 in.
Angle
]
of plate.
glacis.
10'.
broad and 0.4
in.
cracks, shot glanced
in.
deep.
upwards and broke up.
No. 3:
Shot
Ternitz steel
:
The
of flat 5 in.
so that
deep,
shell,
it
headed, 73 lb in weight. Diameter
part was sunk in centre about 0.4 in.
flat
flat
had a sharp cutting edge.
The
shell
was
weighted with lead and sand to 76 lb.
Point struck 46 in. from left edge of plate.
:
58.2
Angle
impact
of
downwards
side
above edge of
glacis.
56'.
and
3 in. broad
Effect: Indent,
5
in.
25°
:
1.3
in.
deep.
Upwards and on
to point hit surface chiselled to
short radial hair cracks.
On
the back of the plate no crack visible.
Shot glanced upwards and broke up.
Round
No. 4:
Shot
Ternitz steel
:
Point struck
50'4
Angle
Effect
of
lb.,
without sand
filling.
in.
above edge of
glacis.
impact: 29° 27'.
Indent 3.5
:
76
shell,
37.5 in. from left edge of plate.
:
No
in.
broad and 0.2
in.
deep.
cracks.
Shot glanced and broke up as before.
Ronnd
No. 5:
Shot
:
As
in last
Point struck
:
round.
68.4
in,
from
left plate
edge.
13.8 in. above glacis plate edge.
Angle
Effect
of
impact
:
Indent 4.7
:
No
43" 22 30".
'
in.
broad and 0.3
in.
deep.
cracks.
Shot glanced and broke up.
Round No.
Shot
:
the
slight depth.
6.
Ternitz Steel Shell, 77.31b. in weight, without sand
filling.
E2
::
.
72
[
Point struck
55 in. from
:
]
plate edge.
left
4.7 in. above glacis plate edge.
Angle
impact
of
5
46°
:
1
'.
and
Effect: Indent 5 in. broad
Two
short hair cracks
0.5 in. deep.
downwards
and
to right
left.
Shot deflected upwards and broke up.
Round No.
Shot
7:
As
:
in
round No.
4.
bringing the gun back to the
order to avoid
In
was directed on the spot
position later on, this round
initial
originally
intended by the programme for the 20th round.
Point struck
55
:
in.
from the
16.5 in. above
Angle
Effect
of impact
A
of glacis.
42° 19'
:
Indent 5
:
broad and 0.2
in.
deep.
in.
radial hair crack to Hit
No
edge.
left plate
edge
No.
6.
crack visible at back of plate.
Shot glanced and brol<e up.
The
in
was suspended
trial
20th January
accordance with the programme.
Round
Round
after
7,
and
the gun, in the meantime, being
;
continued
moved 24°
Distance 39.5 yards.
No. 8
Shot
As
:
before.
Point struck
6
:
from the
in.
left
edge
of plate.
13.8 in. above the edge of the glacis.
(Hit No. 7 of the programme.)
Angle
Effect
of impact
Indent
;
A
43"
:
5 in.
hair crack
At back
it'.
broad and 0.2
upwards
of plate
in.
deep.
to left, another
no cracks
visible.
Shot deflected upwards and broke up.
Round No. 9
Shot
As
:
before, weighted to 76 lb.
Point struck
:
39.4
Angle
Effect
of
;
impact
:
Indent 4.3
No
in.
in.
1 1
from
left
edge
above edge of
of plate.
glacis.
43°, 44,
in.
broad and 0.4
in.
deep.
cracks.
Shot deflected upwards and broke up.
downwards.
on
the
to the
left,
73
[
Round
]
No. 10
Shot
Flat-headed Ternitz steel shell 73.4
:
lead to 76
Point struck
of
weighted with sand and
29.2 in. from left edge of plate.
:
above the edge of
4.7 in.
Angle
lb.,
lb.
impact: 46°
Effect: Indent
broad and
5 in.
glacis.
28'.
deep; abrasions upwards and
1.5 in.
downwards.
Two
The
cracks, a
cracks, to
the
of
and
all
about 4
b,
in.
deep.
appearance, did not penetrate the interior
but were confined to
plate,
the surface
;
two
vertical hair cracks of small length.
At back
no crack
of the plate
visible.
Shot deflected up and broke up.
Round No,
Shot
11
Flat-headed Ternitz steel
:
and lead
Point struck
:
Impact: 25°
of
Effect
Indent 5.5
:
lb.,
weighted with sand
edge
in.
of glacis.
57'.
broad and 0.4
2 hair cracks, c
No
72.8
7.4 in. from the left plate edge.
59.8 in. above
Angle
shell,
to 76 lb.
and
deep.
in.
d.
crack visible at back of plate.
Shot deflected and broke up.
Round No.
Shot
12:
As
:
in last round.
Point struck
:
26
in.
from
left
edge
of plate.
56.5 in. above edge of glacis.
Angle
of
Effect
impact
An
:
A
26" 22 30".
'
:
indent 3.5
in.
broad and 0.4
crack e between
No
hits 2
and
in.
deep.
4.
visible crack at back.
Shot deflected and broke up.
Round No.
Shot
:
13:
Ternitz steel
Point struck
Angle
of
:
shell,
76
lb.,
without sand
edge
30. Sin.
from
36.2
above edge of
impact
:
in.
34'^ 45'.
left
of plate.
glacis.
filling.
1
:
74
[
Effect
Indent, 4
;
No
in.
broad and
j
o.i in. deep.
cracks.
Shot deflected and broke up.
Round No. 14:
Shot
Flat-headed Ternitz steel
:
lead to 76
Point struck
Angle
Effect
:
weighted with sand and
lb.
edge
13.8 in.
above
34.6
above edge of
of impact:
in.
35^
Indent, 7.1
:
shell, 72. 1 lb.,
left
of plate.
glacis.
30'.
broad and
in.
in.
i
deep.
Irregular chisellings of small depth
3 hair cracks
and h
/,. g,
upwards and to the side.
No.
i, from hit.
a hair crack,
;
1
to the left edge.
No
visible crack at back.
Shot deflected and broke up.
Round
No. 15
Shot Ternitz
:
Point struck
edge
Angle
of
:
steel shell
29.6
in.
76
lb.,
from
without sand
edge
left
of
filling.
plate, 26.7 in.
above upper
of glacis.
impact
:
38° 40'.
Fig. 26.
Back of Trial Side Plate of a Chilled Armour Turret for two
4.7 in.
{12 cm) Guns, after the twentieth round, 20/1/85.
Scale
Effect
:
Indent 4.7
Two
in.
:
1.40.
broad, and 0.2
in.
deep
radial hair cracks.
At' the back of the plate, crack e as
28
in.,
beginning about 21.3
vertically
downwards about
in.
a.
hair crack visible for
from the upper edge, and running
8.7 in.
Shot deflected and broke up.
from the centre
line.
[
75
]
00
o
o
s
s:
a.
ni
L.
bo
bo
-i^
o
+->
o
0.
E
o
u.
::
'
76
[
]
Round No. 16
Shot
Flat-headed Ternitz steel shell weighted with sand and lead to
:
76
lbs.
Point struck
Angle
:
7.4 in.
from
4.7 in.
above upper glacis edge.
impact: 46",
of
Effect
:
An
plate edge.
6'.
indent with surface abrasions.
head fixed
Shot's
left
whose depth could not therefore be
indent,
in
measured.
A
crack k to hit 10 with abrasions.
A
crack
Back
down
/
of plate
to
left.
Hair crack a widened.
unchanged.
Shot broke up.
Round No.
Shot
17
As round
:
Point struck
15.
17.7 in. from left plate edge.
:
25.2 in. above edge of glacis
Angle
impact
of
Effect
:
No
39°.
:
Indent 5
in.
broad and
o.i in. deep.
cracks.
Back
of plate
unchanged.
Shot deflected and broke up.
Round No.
Shot
18:
As
:
round.
last
Point struck
19 in. from left plate edge.
:
50.4
in.
above edge of
glacis.
Angle of impact: 30" 30'.
Effect
:
Indent, 4.7
A hair
Back
broad and 0.3
in.
crack
m
of plate
in.
deep.
to hit 14.
unchanged.
Shot deflected and broke up.
Round No. 19
Shot
As
:
last
Point struck
:
round.
28
1
Angle
Effect
of impact
:
in.
:
left
edge.
above edge of
glacis.
43° 35
Indent 6.7
widened 0.4
Back
from
1.8 in.
in.
broad, 0,6
in.
in.
of plate
unchanged.
Shot deflected and broke up.
deep
;
no new cracks
;
crack a
77
[
]
Round No. 20:
Shot
Ternitz steel shell, 75.96
:
Point struck
28.4
Angle
Effect
in.
left
above
lb.,
weighted with sand to 76
lb.
edge,
glacis.
of impact, 38° 23'.
:
Indent 4
A
Back
The
:
broad, and 0.6
in.
hair crack n to hit
of plate
The
:
in.
deep.
a short hair crack upwards.
8,
Hair crack e lengthened to lower plate edge
no other crack
(see fig. 26),
Summary
from
5.5 in.
:
visible at back.
joint of left support
opened about 0.08
in.
plate had resisted 20 steel shells, each with 887 foot tons
energy; that
is
foot
891.5
tons
per ton weight of plate,
or,
reckoning only the half plate attacked, 1,783 foot tons per ton,
without losing any considerable part of the protection
The only
effect
worthy
was the crack
of note
offered.
e at the back, which,
however, did not extend to the upper edge, and had no influence
on the resistance of the
Crack
a, after
removal of the
the upper surface, but
was
affected
The
itself to
was seen
to run
below
did not reach the edge, so that the piece
effect of the
new
flattened curve of surface had
flat-headed shell had
all
more
shown
the shot glancing.
effect
than the pointed ones,
they did not produce serious injury.
The
was
it
glacis,
connexion with the plate.
be extremely favourable,
The
still
in firm
plate.
that
plate
it
had exceeded the demand made upon
should resist fifteen rounds.
it,
which
Nevertheless, no approxi-
mation could be made as to what further amount of firing would
break
it
up.
The
material,
glass.
of the
Ternitz shell exhibited throughout an extremely hard
the
No
broken
pieces,
as
with Krupp
shell,
scratching
great difference tould be noted between the qualities
two kinds
of projectiles.
78
[
1
Conclusions.
There
is
but
to add to the several
little
summaries
of the trials,
which
are very explicit.
All the plates
had
the
satisfied
demands made upon them, but as
the latter vary greatly, a few remarks are necessary.
The
object of the
first firing trial
injurious or not, the position of
This
was
to determine
if
chill
cracks were
which led to a concentration of the
shot.
as well as the following ones, clearly proved that these chill
trial,
cracks are without any influence on the power of endurance of the
plate.
In trials 2
—
5 a concentration of rounds, fired with full charge, took
number of hits was proporwas to note the behaviour of
place on a small surface of the plate, but the
tionately small, as the only object intended
the plate under this concentrated
Trials
of
i
—
must therefore be considered under the aspect
5
material, but
the
fire.
at
the
same time the
results led to
of a test
an important
the armour, namely a flattening of
alteration in the construction of
the
profile.
An armour
plate,
subject of Trial No.
improved
6,
in
which thus
correspondence therewith, formed the
may be
considered in distinction from
the previous trials as a test of the design of construction.
The
conditions
of
this
trial
were
in
all
respects
those of
actual
warfare.
The number
greater
— 20
of hits
on the half
which the plate had to stand was considerably
plate, equal to
40
for the
whole plate
—
were distributed over the surface, and the attacking gun did not
they
^but
fire
a
full
charge, but only one corresponding to a distance of 1,093 yards.
The
result of this trial
showed most
distinctly that the conclusions
which the construction of this plate had been based were correct;
profile
had proved
itself to
on
the
be advantageous, and the dimensions selected
appropriate.
We
will revert to this subject after describing the trials against coast
defence armour.
79
[
]
II.—Firing Trials against Chilled Armour
for Coast Fortifications in
the years 1883—1886.
For the purposes
of the firing trials against coast armour, a
number
of
were employed, namely
Three side plates for a turret ordered by the Dutch Government for two
i2in. (30.5 cm) 35 calibre guns, and a side plate for a turret ordered by the
The conItalian Government for two 35 calibre i5-7 in. (40 cm) guns.
plates for
two
different chilled
armour
turrets
:
struction of this last followed the experience gained with the trial which
preceded
it,
and
this
whole series of
trials
Like those previously described, these
by the existence of a number of
it
was necessary
to
chill
thus stands complete by
trials
were originally called
demonstrate the absence of injurious influence.
for coast defence, the attack
This
and the
first trial,
subsequent ones treated as tests of material and design.
armour
for
cracks in the different plates, of which
demonstration could be considered as established by the
to the selection of
itself.
Corresponding
was made with the
The number of hits,
(30.5 cm) and 17 in. (43 cm) naval guns.
however, exceeded those which, in all probability, coast armour would be
12
in.
called
upon
to withstand in practice,
forming an opinion on the
results,
if
and attention must be paid
to this in
the trials are to be considered from
the point of view of actual warfare,
1.—Trial against a Glacis Plate of a Chilled Iron Armour Turret
for two 12 in. (30.5 cm) Guns, 35 calibres long.
On
Gruson's Firing Ground at Buckau.
13th August, 1883.
Object and Programme of the
Apart from a general
test of the design
Trial.
and dimensions
by concentrating several rounds from the 25 calibre
J
of the plate,
2 in. (30.5
cm) gun
close to certain chill cracks existing in the plate, to determine whether
these latter influenced
Target.
—The
its
resisting powers.
turret to
which the
the main to the type
shown
trial
plate belonged corresponded in
in Fig. 4.
The cupola was formed of 1 1
diameter of 33.5 ft. The height from
to the
chilled
plates,
and had a
the edge of the roller ring
upper edge of the ring of cupola plates was 15.7
that from the roller ring to the base of the lower storey 19
ft.,
ft.
and
80
[
The
placed
armour was also
glacis
had a height
in front
roof of the cupola, 21
sights placed
]
in
which
pieces, of
1 1
of 5.7
the others 4.1
ft.,
5 plates
The
ft.
diameter, was in two parts, with the
ft.
and used from a covered
in the joining grooves,
man-hole.
The
horizontal training of the turret
was
carried out either
by hand or steam power, a.s convenient, a whole turn being made
by steam in 4 minutes 20 seconds, and j-turn by hand in
4 minutes. The engine was of 26 I.H.P. Ten men worked the
hand gear.
The guns were mounted
in
Gruson's minimum-port carriage
worked by two accumulators. These were placed in the
lower storey of the turret, and served also as hydraulic cranes for
changing the guns. The carriage gave 12° elevation and 6°
depression.
No provision was made for lateral movement.
C/80,
was a
In the trial glacis plate there
chill
crack stretching
almost without break from the upper to the lower edge in the
centre
The
line.
plate
was
built
up with four others so as
to form
almost half a ring of plates, the ends being supported by masonry
Before the lower part of
pillars.
the
protecting layer of granite was placed
similarly covered with concrete
;
plate
(see
fig.
28)
a
the other plates were
which terminated
at the
masonry
pillars.
The
chill
deep, and
The
crack was throughout about 0.4
shown
is
usual
in fig.
wood and
in.
wide and
2.8 in
28 by a dotted line.
earth screen
was
placed.in front to guard
against splinters of shot.
The
thickness of
the
greatest expanded breadth
trial
was
plate
13.8
ft.,
is
given in Fig. 28.
height 8.9
ft.,
Its
and weight
36.9 tons.
Gun: Krupp's 25
calibre,
Gun
carriage C/80.
Distance
:
about 981.3
:
264.6
(30.5
cm) gun
in
Gruson minimum-port
fired with 6° depression.
energy:
shell,
empty, 12
in. (30.5
lb.
lb.
Striking velocity
„
in.
29.5 yards.
Shot: Krupp steel
Charge
12
:
P.P. C/80.
About 486.4 yards per
„
14,519 foot tons.
sec.
cm), 3.5 calibres long, weight
81
[
Round No.
Shot
]
1
Krupp's
:
Point struck
impact
of
Effect
:
lb.
8.7 in. right of centre line.
:
above glacis edge.
2.8 in.
Angle
above, weighted with sand and lead to 981.3
shell, as
48°.
:
Chisel cutting 2.4
near hit on
maximum
deep,
in.
(greatest depth, at left
crack, 1.7 in.)
chill
maximum
Surface abrasion in
Three short hair cracks
and
a, b
19.2 in.
broad and 20
in.
high.
c.
Chill crack unaltered.
Glacis torn up, 6
Back
deep at point struck.
in.
of plate intact.
General state of target
about 0.4
Round
in.,
upper edge of
:
due to movement
of
masonry
trial
plate had dropped
pillar.
Shot broke up.
No. 2
Shot
As
:
in
i
Point struck
Angle
8
:
in. left of
impact
of
Effect: Indent
round
:
and
both
centre line on upper glacis edge.
53°.
chiselling of 'point struck 2.4 in. deep.
20
hits
d
Horizontal crack
greatest
in.
Back
of plate
:
and
through centres of both
crack at right angles.
chill
breadth
Chill crack
Abrasions
22.8 in.
hits,
high.
crossing the
unchanged.
Crack d visible throughout
its
whole length,
dividing the plate into two parts.
General state of target: The plate was pushed back
on the
left
The
and
glacis
on the
1.4 in.
and had dropped about 0.4 in.
was so torn away by hit 2 that the plate was laid
1.2 in.
bare over a breadth of 22.8
right,
in.
and
7 in. in depth.
Shot broke up.
Round
No. 3:
Shot
As
:
before.
Point struck
edge
On
:
centre line
(chill
crack)
2.4 in.
above original
of glacis.
The
chilled
surface
was
entirely
removed
at
the
point
struck.
Angle
Effect
of
:
impact
:
52°
Indent 5.3
in.
broad and 18.5
A
vertical
in.
deep.
Abrasion of surface increased to 30.7
in.
high.
through crack
e,
stretching to the upper edge
82
[
from a point 8
crack 6.7
in.
crack
chill
leaving
;
below, leaving
and finished downwards
crack was
centre line ran along 8
right of
in.
a portion of the
]
this,
lengthened about 8
chill
lower down,
in.
The upper end
to the left.
from
struck into the
again about 10
it
in.
of the chill
by a hair crack, but was
in.
otherwise unaltered.
Back
of plate
:
Crack
throughout
e visible
its
length, dividing
the plate into four parts.
General state of the Target
crack e was
seen to cross the
reaching the lower plate edge
The
On
:
chill
removal of the
crack and
13.8 in.
right
its
from the same.
crack at lower part of the plate was 1.4
Round No.
Shot
The
wide.
in.
two upper parts of the plate had dropped about 4
upper edge pushed back about 5.5 in. more.
The
glacis,
branches,
in.,
and
its
shot broke up.
4:
As
:
before.
Point struck
:
About 27.6
Angle
impact
of
:
centre
in. left of
line.
above glacis edge.
8 in.
About 40°.
The two upper parts of the plate were thrown inwards and a
number of pieces knocked off the piece struck.
The plate was thus breached. A new crack /. Chill crack
Effect
:
unchanged.
Back of the plate The back of the portion still standing
was no longer visible, being covered by broken parts fallen down.
Later it was seen that the crack e was widened at the lower part.
:
General
The
:
target
:
The whole
(«.)
Behaviour of the
for this
line
trial
was
chill
crack.
had
in to 1.2 in.
As already
noted, the chief
to ascertain the influence of the chill crack,
purpose three rounds were concentrated on a straight
15.7 in. long, with a total energy of 43,605 foot tons.
form a test of the design of the
been
target
between the
considerably, as the joints
shot broke up.
object of the
and
moved
and adjacent plates had been opened from 0.4
trial
Siimmai'y
the
of
state
apparently been
distributed,
in
plate,
To
should have
the hits
accordance with the conditions of actual
warfare, over the surface, as
it is
not reasonable to
make
stronger, and so dearer, than actual practice requires.
a plate
[
^
oo
^
s
bo
o
CO
"^
^
I
83
]
84
[
On
]
inspection of the glacis,
of following, as
was seen
it
was supposed, the
that crack
e,
instead
and formed
crack, crossed
chill
a branch towards the bottom edge of the plate {see Fig. 28).
In the upper part of the
armour plate the crack
twice for a short distance the
that the plane of fracture
chill
crack
;
was a constant
but
curve,
clear that the crack e
independent of the
From
chill
it
as might be expected from the
crack (2.8
thickness of the plate (27.6
this
in the interior of the plate entirely
chill crack,
depth of the
small
was
be noted
and only joined
superficially the irregular zigzag of the chill crack
was
e followed
to
is
it
in.)
in
proportion
to
the
in.)
Further evidence that the
chill
crack had no injurious effect
lay in the fact that crack e diagonally crossed, at the under part of
the plate,
the
four-sided
piece,
bounded by the
chill
cracks,
without following either side or running into the lower
chill
crack.
That
chill cracks do
proved, and the
real
no harm seemed by this sufficiently
of the trial was in consequence
object
fulfilled.
Behaviour of the armour plate and
(b!)
close examination of the target
the
plate had sunk about 0.8
trial
of the structure.
A
showed that the foundation under
in.,
so that the nearest part of
the plates adjoining did not rest upon the foundation.
The inner projection of the bed-plate at the left joining edge
was broken away, and both joints between the four plates not
had opened about
fired at
0.2 in.
Lastly an opening between
the concrete covering and the masonry pillar showed that the
latter
left
had been pushed back, the
one 0.3
in.,
masonry had not
part
right
which was accounted
sufficiently set, the
one about 0.4
for
by the
in.,
and the
fact that the
mortar being for the most
wet.
still
The
the target showed
state of
that the four unattacked
plates had moved round on the bed-plate
in a nearly
circular
direction,
and
backward
yielding, together with the sinking of the foundation,
made
it
had
pushed
the
masonry
pillars
back.
possible that the crack e below had opened 1.4
in.
This
without
bringing the lateral joining edges of the plate into contact with
[
85
]
those of the adjacent ones, the point of bed-plate breaking as a
result of this separation, as
it
had alone
tremendous
to resist the
blows given.
From
it is
the sinking of the plate observed after the
movement
evident that the
of the target
first
round,
had already taken
place at this round, and consequently the plate was standing loose
at the next round.
These circumstances explain the
falling out of pieces
by cracks, which never would occur with a properly
loosened
up
built
glacis armour.
which before the third shot was
only loosely resting on the lower half, and had sunk about 1.6 in.,
That the upper half
of the plate
hanging between the adjoining
plates,
was not crumbled up by the
3rd shot into numerous pieces, points to an excellent quality of
material.
The
If
following result was
observed as worthy of notice
:
a shot struck on a part from which the layer of white
iron had
been already removed,
it
did not cause any very
much
greater injury than shots striking on an uninjured part, as the
hardness of surface seemed to extend
The
layer.
away
cutting
much deeper than
of the surface only
the white
showed an increased
toughness of material.
Although the stout resistance offered by the plate to concentrated
fire,
even after the foundation had
failed,
apparently valid conclusion that, in actual practice,
found amply strong enough when made use of
of the turret, the
an
Dutch Committee
it
led to the
would be
in the construction
for the Trial decided to
alteration in the construction of the front glacis plates,
chiefly consisted in the provision of pillars
plate,
which made
broken
it
loose, to fall
which
on both sides of the
impossible for upper pieces, which might be
down.
All the shot broke into pieces,
and excellent
make
material.
showing an unusually hard
[
2.—Trial
against
for
a
On
]
Armour Turret
Plate for a Chilled Iron
Side
two 12
86
in. (30.5
cm) Guns, 35
calibres long.
Gruson's Firing Ground at Buckau.
22nd October, 1883.
Object and Programme of the
Trial.
Test of the armour by 4 shots from the Krupp 12
and also to determine by the trial whether
[a)
The dimensions
selected
for
the
armour
in.
of
{30.5
this
cm) gun,
turret
were
appropriate.
{b)
The behaviour
of chill cracks existing in the plate
the results of the
of influence
trial of
would confirm
13th August, 1883, as regards their lack
on the endurance of the
plate.
Fig. 29.
Structure for the Side Plate of the Chilled Iron
two 12
in.
(30.5 cni) Guns,
Scale
Target
:
The
trial
plate
Armour Turret for
:
1.40.
formed part
of the
cupola of the turret
by the Dutch Government. It
was placed between four other side-plates and a roof-plate, so
previously described as ordered
as to form half
a
turret,
which
rested
at
the rear
against
three strong pillars of masonry, connected with the armour
three stout specially cast struts.
by
87
L
The
structure
Above the
is
shown
]
in Fig. 29.
was a
roof-plates
layer of timber baulks as
a
As seen in the figure, the
roof-plate.
They were weighted with
screen against splinters of shot.
baulks did not
three
layers
some yards
on the
lie
iron
of
and the whole covered with earth
rails,
high.
In the inside of the turret, to which a staging
plummets and gauges
measuring any change
for
masonry
were ten
In the trial plate
of greatest
depth 0.6
which
in.,
numerals
lines with small
The dimensions
Weight
Krupp's 12
Distance
Shot
:
was
lb.
dotted
shown by
9.5
ft.,
height 11.5
Fig. 30.
Its
ft.
calibres,
on Gruson minimum-pt)rt
2*^ 12'
4° 30'.
fired
with a depression of
cm)
steel
—
264.6
(30.5
shell,
calibres,
3.5
empty, about
P.P. C/80.
lb.
of impact
Round No.
in.
weight.
Velocity of impact
Energy
cm) gun, 25
(30.5
The gun
Krupp's 12
:
in
29.5 yards.
:
981.3
Charge
in the casting,
marked
46.7 tons.
in.
carriage C/80.
made
cracks
plate are
the
of
chill
in the figure are
to 10.
i
greatest breadth expanded
:
roof, whilst the
from the centre
was ascertained by three gauges.
pillar
Gun
from the
trial plate
pillar
distance of the bottom surface of the
were
pendulum hung on
the roof-and ring-plates, an exactly adjusted
either side of the central
led,
in the position of
:
About 486.4 yards.
:
About 14,519
foot tons.
1
Shot: Krupp's 12
Point of impact:
in. steel shell,
1.6 in.
empty, about 982.6
right of the
lb.
weight.
centre line of plate, 35.4
in.
greatest depth, 19
in.
above the lower edge.
Angle
Effect:
of
impact: 90°.
An
abrasion
broad, and 20.5
On
round the
in.
hit
1.4 in. in
high.
the point struck, the tip of the shot, which was forced
<was welded on to the plate, and showed as a
diameter, with a slight rise in the
away on
its
flat
flat,
disc about 6 in. in
centre, but
apparently formed on the plate, only a
steel held so firmly to the
flat
no indent was
depression, but the
armour that when cut out
it
brought
point a piece of the chilled metal.
F2
[
88
]
Five short radial hair cracks were formed from the point
struck.
A
the
horizontal crack a reached both edges
left
plate,
49.2
in.,
on the right 35.8
along the crack, to the
broad, and 11.8
in.
by
in.
left of
15.7 in.
of the plate,
Above the lower edge
on
of the
point struck, an abrasion 1.2
long.
in.
89
[
Back
of plate
On
:
1
inspection of the interior the crack a
was
seen to have gone right through and showed as a fine hair crack,
beginning 17.7
8.7 in.
edge
left
off in
to
the middle
long towards the lower edge with a slight bend to
in.
and
left,
and running
of the plate
A crack ^ branched
from the right edge.
about 17.3
the
from
in.
above the edge.
finishing 6.7 in.
General state of the target
By means of the plummet it
was found that the roof-plate had receded about 0.04 in. on the
right and o.i in. on the left hand.
Also at the base the plate fired
at had been pushed nearer to the pillar, as was shown by the
fact that the wooden gauges placed between the pillar and the
:
plate
were
The
in part broken.
between the
joint
trial-and roof-plate
those between the trial-plate and
its
was closed
the inner edge of the joint, an average of o.i
them 0.04
in.
broad on the right and
This condition of
pillars
the
interior
0.1 in.
An
in.
had been made between the masonry pillars and the
to
up,
and
plates at the side opened, on
opening
struts attached
on the
left.
showed that the masonry
had not been able to prevent a movement outwards
the whole structure
;
but this was so slight that
a reason for discontinuing the
it
of
did not furnish
trial.
Shot broke up.
Round No. 2
Shot: Krupp's 12
Point struck
:
On
in. (30.5
cm)
steel shell,
the centre line
empty weight, 984
lb.
:
74.8 in above the lower plate edge.
above Round
in.
39.4
Angle
i.
of impact: 51°.
Effect:
19
A
long chiselling at the point struck 27.6
in.
long,
and
4.7
greatest width, as
Four
A
and
left
in.
shown
in.
greatest depth,
broad, abrasion around about 21.7
in.
in the sketch.
hair cracks about 8 in. long.
crack
b,
bending upwards to the
finishing 19.7 in. from
left
from the point struck,
upper plate edge, and
6.7 in.
from the
edge.
A
crack c from the
after a sharp
A
bend
hit,
curving to the right, and finishing
at the plate edge.
vertical crack, d, joining Hits
of this crack
i
and 2
;
no prolongation
below crack a was observable, but the same pro-
:
90
[
1
bably existed, as a crack in this direction was already formed by
the
round at the back of the plate-
first
Back
of the plate
Horizontal crack a seen to stretch to
:
both plate edges and opened about 0.04
b, c, d,
were not
The
in.
General condition of the target
:
by the plummet the
had further receded on both sides about
plate
distance of the pillar from
The
back
roof-
o.i in., whilst
the foot of the plate
had also pushed
roof-plate
other cracks,
visible there.
had not
slightly
its
the
altered.
supporting
plates.
The
between the
joints
and the roof-plates had,
trial
in con-
sequence, apparently, of the yielding of the support plates of
the latter, gone back to their original dimensions
the
plate
trial
and
its
those between
;
up about
side plates had closed
0.2 in.
This closing of the lateral joints seemed to point to a closing
together and consolidation of the
under external blows.
and
As
yielding of the roof plate o.i
Round
or arch of the target
the joints between the masonry pillars
the supporting struts
The
dome
showed no material widening, the
in. did not seem important.
shot broke up.
No. 3
Shot
As
:
before, weighted with sand
Point struck
26.8
:
in.
53
33.6
Angle
Effect
impact
of
:
:
and lead to 978.6
lb.
right from the centre line.
in.
above the lower edge.
from shot
in.
i,
35.4
in.
from shot
2.
72".
at the point struck a chiselling out 2 in. deep, with abrasions
around, as in Fig. 33.
Eight radial cracks from the
f
joining 2 and
plate
;
f
3,
hit,
and running upwards
did not run into
e joining
but ran parallel to
b,
hits
to the right
it
i
and
edge
3,
of the
for a short
distance.
c
was lengthened upwards,
Back
round
3,
of
the
plate
:
Two
b
widened to about
additional
cracks
0.3 in.
showed
after
starting from a point on the left edge, one with a nest
of small branches ending in crack a. the second finishing 8 in.
above
this.
It
seemed possible
that the larger of
these two
cracks connected with crack b on the inside, although on the
outside b reached nearly to the upper edge.
[
The
state of the
in Fig. 32.
back
91
]
of the plate after the 3rd
The few through
as not of serious
round
is
seen
cracks seemed for so heavy a plate
moment.
General state of the target
:
The gauges showed
that the roof
-1
o
00
K
^
a
nS
i.
an
o
o
+j
s:
S
B
o
had been pushed back a further 0.08 in., and also that the whole
On
right edge of the plate had moved inwards some millimetres.
the left the roof and edge of the plate had apparently not moved.
The
joints
between the
roof-
and
trial -plates
were opened
to
92
[
J
a further considerable extent as also the joints of the
right plate at the side,
below 0.4
that with the left plate
in.;
trial
and
which showed an opening, on top 0.2
was
0.2 in.
on top and
in.,
0.2 in.
below.
The
left pillar
showed an important change, the joint between
in.
No change was visible on
and the strut having opened 0.2
it
the right.
It
was unmistakeable,
that on the
of the plates, the strength of the
but
it
seemed nevertheless capable
The
left,
dome was
owing
to the yielding
considerably reduced,
of withstanding a fourth hit.
shot broke up.
Fig. 32.
Back of the Trial Side Plate of the Chilled Iron Armour Turret for two
12 in. (30.5 cm) Guns after the third round, 22/10/83.
Scale
:
1.40.
Bound No. 4:
Shot: Krupp's 12
lead to 981.3
Point struck
:
in.
steel shell,
980.31b., weighted with
sand and
lb.
29.6
in.
from the
left
plate edge.
25.6 in, above the lower plate edge.
33.1 in. from hit No.
Angle
Effect
of
:
impact
The
:
About
750.
fourth round breached the plate
bounded by cracks
pillar,
i.
a,
g and
h, inside
and forced a piece
of plate
the turret against the centre
which caused other pieces of plate on the
left to fall
down,
so as to partly close the breach again, the separated pieces of
armour remaining
The
plate
therein.
was broken
into 6 pieces
by cracks
a, b, c, d, f, g.
[
Back
of the plate
:
93
The
]
cracks at back were
much widened by
new cracks were
the falling of the parts of the plates in front; but no
observed, as the effect of the round had been concentrated on the
5^
5"
!^
o
CO
s:
a
bo
o
o
a.
ho
:-
*<
«
£
o
8
piece bounded by cracks a and g.
of the shot lay
on the
Several pieces of plating and
inside.
General state of the target
:
The
roof plate had not receded
94
[
by Round
further
and
pillars
4,
]
but the opening of the joints between the
had increased to 0,6
struts
yielding of the whole structure
in.,
was shown
so that a sideways
to have occurred.
This was confirmed when the earth was removed from the
Between the
target.
roof
and side plates on the
which
left,
before the firing were placed close together, an opening i.2in.
wide had been formed, and showed that both the
side plates,
left
with their bed plates, had been pushed outwards.
The
Summary
:
shot broke up.
The
plate resisted three rounds, with a total energy of 43,508
foot tons, or 914 foot-tons per ton of armour, without decrease
in the protection
afforded
After
to the interior of the turret.
these rounds the plate was separated into several large pieces
by numerous cracks passing partly from side to side, and through
the thickness of the plate, but no displacement of parts had
occurred.
The
surface
showed
injuries
round the points
hit,
which had
a certain extension, but only a few inches of depth.
No
penetration of the shot, or of their points into the plate,
had taken place.
Several obvious circumstances brought about the breaching
of the plate
Crack
at the
by the fourth round.
g was formed
back
already, before the round,
of the plate.
and
visible
Crack a went right through the
plate,
was already loosened.
not moved, the piece would
so that the upper small part on the left
Had
the other plates and the pillars
was, the
in all probability
have withstood another round, but as
whole
the shot could be expended in dislodging the
effect
piece of
of
plate,
which, as a natural
inwards to the interior of the
The
chill
it
consequence, was driven
turret.
cracks in none of the four rounds had shown to
have any injurious influence on the plate.
As seen
in the drawings, the cracks set
their course quite
independent of the
was even a lengthening
of the latter
chill
up by the shot took
cracks,
and
in
no case
produced by the blow
of
a
shot.
The
viz.
:
steel shells
behaved
in this trial as in all
previous ones,
they broke up into numerous pieces of the size df a
that of a pea.
fist
to
95
[
3.
—^Trial
]
against a Half-roof Plate for a Chilled Iron
Armour
Turret for two 12in. (30.5 cm) Guns, 35 caUbres long-
On
Grason's Firing Ground at Buckau.
26th and 28th May, 1884.
Object and
Programme
of the Trial.
Proof of the roof for a turret by 4 shots from the Krupp 12
(30.5
cm) gun.
The
trials
in.
had
directed
had
test in this case
shown
sufficiently
discover
to
less reference to chill cracks, as the previous
their
want
the dimensions of the plate were
if
withstand the attack of the Krupp 12
Target
:
The
No.
trial
The shape
corresponding
rib in the other plate
in
The
to
is
seen in Figures 34
straight edge, which rested on a
its
The manhole
mentioned
sufficient
gun.
in.
i.
as also the rib on
35,
was rather
plate formed one half of the roof of the turret
trial
described under
and
of injurious effect, but
when placed on
the turret.
the centre, as well as the sighting holes, are
in the previous description.
trial
plate was, corresponding
to
its
position in the
supported by three cast-iron plates of 39.1 tons weight
"
placed in a half ring and keyed together. The other " half plate
turret,
was replaced-by three
masonry
of ribs to
similar cast-iron plates resting against three
The
pillars.
cast-iron ring plates
were fixed by means
a base plate, and also the centre ring plates were
bolted together with two bolts.
In order to obtain increased angles of impact the trial plate
was not placed
horizontally, but at
imaginary plane of
its
location
an angle
of 5°, that
made an angle
the
is,
of 5° with the
horizon.
A
number of small chill cracks existed in the trial plate,
which were closed with steel wedges, and there were further in
the plate three holes 4.7
in.
in
diameter for use in placing the
plate in position on the turret.
The
usual
wood and
earth screen against shot splinters
was
provided.
The
Its
chief dimensions of the trial plate are given in Fig. 34.
weight was 46.7 tons.
Gun: Krupp's 25
calibre
I2in. (30.5
cm) gun
in
Gruson's minimum-port
carriage C/80.
The gun was
fired
with a depression of from
3''
44' to 5°
6'.
[
]
Distance: 31.7 yards.
Krupp's 12 in. 3.5 calibre steel shell empty, weight about 981.3
Shot
:
Charge
:
176.4
Velocity of impact
Energy
of
lb.
P.P. C/80.
lb.
impact
:
:
392 yards per sec*
About 9,503
foot-tons.
Kound No. 1:
Shot: Krupp's 12
lead to 981.3
Point struck
:
in.
steel shell, 978.61b.
lb.
19.7 in. left of the centre line.
13.4
in.
from the round edge of the plate.
Fig
Iron
Armour Turret for
two 12
Trial Roof-plate of a Chilled
the
in. (^30.5
Scale
-910
34-
and Diagram of Hits of
Profile
:
Angle
Effect
of
:
cm) Guns.
26 ak^ 28/5/84.
1.60.
6400
«
>,
weighted with sand and
impact
:
Chiselling
23 by
1
A
1.4 in.
24°
14'.
surface
out of
radial crack a
3 hair cracks h,
of
in.
deep,
with abrasions of
from the point struck, and finishing 24.4
from the straight edge
Back
0.9
greatest extension.
plate
c,
:
in.
of the plate.
d.
crack a was visible throughout
its
entire
length.
—
* NOTE. This figure is taken from the Official Reports of the Dutch Commission, and
probably more correct than the figure 377 yards previously given.
is
97
[
1
General state of the target
:
The
the plate in
position of
was apparently unaltered, the
showing no change.
the structure of the target
between the ring plates
The
joints
shot broke up.
Bonnd No. 2:
Shot
Krupp's i2
:
Point struck
Angle
Effect
of
a
1
impact
The
:
On
:
in. steel shell;
centre
line,
weight 984.5 lb., empty.
in. from the round edge.
49.6
19° 35'.
:
made
mark on the upper half 4 in. deep with abrasions of
by 19.7 in. greatest extension and small depth. Crack b
shot struck the central hole for lifting the plate and
chisel
1.8 in.
was lengthened
to the
round edge of the
from the point struck ran upwards to the
under the straight edge.
crack a at
a.
f
Hair crack
sharp angle, h 12.6
in.
A new
plate.
crack e
right, finishing 25.2 in.
15.7 in. long,
^
crossing
long.
Back of plate Crack a extended from edge to edge, e began
back 25.2 in. below the straight edge, passed through the
centre mounting hole and stretched in zig zag to the round edge.
Crack y ran nearly radially from the centre mounting hole to the
:
at the
edge 38.2
straight plate
in. in
length, the direction differing con-
siderably to that on the front of the plate.
back as
Crack
g was
visible at
far as crack a (see fig. 35).
General state of the target
:
The
radial crack in the central
had widened, and the plate sunk about
of the ring plates were unaltered.
plate of the base ring
0.06
in.,
but the joints
The
shot broke up.
Bound No. 3
Shot
Krupp's 12
:
steel shell, 980.3 lb.,
in.
weighted with sand and
lead to 981.31b.
Point struck
Angle
Effect
:
28.3
in.
right of centre line.
27.6
in.
from the round edge.
of impact:
:
22°
52'.
A long indent without
struck running to crack
abrasions.
e,
reaching the round edge.
ending 4
in.
Back
A
crack / from the point
m, the
last
Crack a extended upwards to the
left,
three short cracks,
k,
I,
from the straight edge.
of plate
:
Crack
i visible
throughout
its
length, / con-
necting with d, separating, as seen in the figure, a piece of the
plate.
Crack
m visible,
apparently connecting with
k.
98
[
General state of the target
plate
0.08
Shot
:
to 0.1
in the centre
supporting
right half of the plate
sunk
in.
shot broke up.
Krupp's steel sheel 981.5
hits
of impact
:
The
and,
weight, empty.
:
i
and
from the round edge
3.
23^ 25
'.
shot hit the piece of plate loosened by cracks
addition to an
in
rounds
lb. in
11 in. right of centre line, 17.8 in.
:
between
Effect
The crack
4:
Point struck
Angle
:
was somewhat widened and the
in.
The
Bound No.
]
i
and
indent, caused
shown
3, as
b,
h and
/,
abrasions upwards like
in Fig. 34.
Fig.
3S-
Back of the Trial Roof Plate of the Chilled Iron Armour Turret for
two 12
Guns after
in. (30.5 cni)
the sixth round, 28/5/84.
r edits
New
to hit
I.
about 1.4
cracks n,
The
0,
p,
d
to the
piece of plate
edge
of the
plate,
bounded by crack
b
h lengthened
was
thrust
up
in.
examination of crack b showed that it ran in the metal
not visible at the
close, to the round edge of the plate, but was
An
back
of the plate.
Back
of plate
:
the 4th round had not produced any
new
cracks
crack, but had caused the sinking of the piece bounded by
99
[
and
/
0.4
This was 6
d.
on the
in.
in.
]
on the
left,
The separated
right.
0.6 in. in the centre,
and
part remained fixed in the
cracks.
The
general condition of the target was apparently unaltered.
Shot broke up.
The
had thus
plate
it seemed
was continued on the
the terms of the contract, but as
fulfilled
yet completely able to afford protection, the
trial
28th May.
Round No. 5:
Shot: Krupp's flat-headed 12
Diameter
Point struck
Angle
Effect
A
:
41.7
:
empty, weight 981.31b.
steel shell,
of flat part, 5.4 in.
in. left of
impact: 12°
of
in.
long indent 0.4
3 cracks,
in.
in.
above the straight edge.
deep without abrasions.
which were
r, s,
q,
centre line, 23.6
18'.
all
back of the
visible at the
plate.
General state of the target
/
and d had further sunk about
The crack
plate.
:
i
The
in.,
piece separated by cracks
but
still
remained
fast in the
supporting plate was widened
in the central
to 0,4 in.
Shot broke up.
fionnd No. 6
Shot As
in
:
Point struck
Angle
Effect
t
:
On
impact
of
:
round
A
and
5.
centre line of plate 33
:
13°
in.
under the straight edge.
14'.
long indent without surface abrasions.
Back
and u
Two
fine cracks
Crack / lengthened.
u.
of
plate
visible.
/
:
No
lengthened to the edges of the plate,
further drop in part broken loose.
General state of the target
:
The
trial
had to be stopped
after the sixth round, as the butt for stopping the shot
much
injured
as
to
offer
no further guarantee
for
was so
arresting
subsequent rounds.
Moreover, as the
official
report of the Trial Committee stated,
was not to be expected that a few more
effect any great change in its condition.
it
The
shot broke up.
hits
on the plate would
[
100
J
•-1
1^1
k 00
a
bo
o
o
!->
is.
ba
s
JS
a.
S
o
s
<4j
t-1
101
[
Snmmary: The
plate had withstood six rounds with a total energy of
57,016 foot tons, that
armour,
the
]
and
1
is,
198.3 foot tons per ton of material of
displayed
thus
an
beyond
endurance
the
necessities of actual service, as in this case the shot could never
an angle.
strike at so great
The dimensions
selected had proved
appropriate, and the advantage of the arched form had been clearly
demonstrated,
as, for instance,
round 4 struck a piece of plate
completely loosened, but was unable to drive this piece into the
owing
interior of the turret, although the resistance of the arch,
bed
to the cracking of the
The
plate,
had been considerably reduced.
6th round, also, struck an already loosened piece without
being able to dislodge
The
chill
towards the
interior.
cracks proved, as before, to have no effect on the
endurance of the
menced and ran
The
it
plate, as the cracks
produced by the
hits
com-
quite independent of the former.
great effect of the angle of impact on the injuries
resulting from the hits
was
of interest.
The
directed against the lower part of the plate
greater than that of rounds 5 and
struck the plate, found
after the ogival
it
6,
although these,
already weakened.
head of the shot had
effect of the
rounds
was disproportionately
To
all
hit the plate,
when they
appearance,
a second blow
was struck by the base of the shot, and this blow, to which
seemed that most of the shot's effect was due, was heavier
proportion as the angle of impact increased.
of
The
it
in
greater angle
impact obtained by depressing the gun and inclining the
may be considered, in view of actual service, to have
more than balanced the higher powder charge. Moreover, this
heavy blow of the base of the shell may explain why they all
plate
broke to pieces on impact, which, considering the quality of
Krupp's
steel,
would have been a matter
of
assumption of a mere twisting of the ogival part.
surprise on the
—
[
102
]
4.— Conclusions of the Dutch Commission respecting Trials
As
to 3
1 to 3.
already mentioned at the beginning of the chapter, the Trials
were undertaken
the Dutch Government,
at the instance of
i
who
appointed a Commission to carry them out, consisting of Lieut.-Colonel
Voorduin, of the Engineers, Captain Scherer, of the Artillery, and Captain
Snyders, of the Engineers.
report of this commission was subsequently published by the
Ministry
of War, entitled " Verslagen omtrent schietproeven tegen
Dutch
The
pantseringen, 1884."
The
report contains, in pages 149
obtained, which
we now reproduce
—
157, the conclusions
on the results
verbatim.
Conclusions and Decisions arising tlierefrom.
As regards
the first trial, the
glacis
tendency to crack through under the blows
armour plate
of the hits,
exhibited
a
independent of the
upper surface of the plate, or of their direction,
the direction of a plane in respect to which the moment of
chill cracks existing in the
but exactly in
the part of the plate which
be nearly a maximum.
section of
hung
If
it
over,
and was separated by
the plate at the point attacked was
too small
adequate resistance to fracture, on the other hand,
that, in
consequence
fracture,
must
followed from this circumstance that -the
it
was
to
offer
clearly
of its unfavourable profile, the plate, in
an
shown
whose section
a considerable arching existed, was thereby in a measure already prepared
for fracture.
Moreover,
this
first
trial
clearly
between the plates placed together
the pushing
away
showed that the
glacis was too
in the
of separated portions, so that
In opposition to these serious defects, the glacis
An
appropriate
prevent
of the cupola placed
armour can very soon be compromised.
following good properties during the
{a)
connection
in the actual structure
movement
these defects cannot be avoided, the free
inside of the ring of glacis
if
side
slight to
degree
trial
of
armour showed the
:
hardness
on
the
surface,
which
apparently renders penetration by the shot impossible.
(b.)
Great resistance against such penetration also in the so-called
transition layer, and, within
soft metal.
certain limits also, in the interior of
108
[
of the so-called "
Complete homogeneity
{c.)
]
Gruson metal "
the
in
different layers, with great fineness of crystals and entire absence
of internal casting faults.
Non-injuriousness, within certain
[d.)
On
at
in the
close
the
of
trial
that,
subject to
Minister, the glacis armour, on account of
inappropriate proportions of
a request would be
made
chill
which
surface,
manufacture.
the ground of these considerations, the manufacturer
the
the
in
faults
or projections on the upper
casting, as cracks
sometimes arise
of
limits,
its sections,
to replace
it
its
of
War
the
dimensions and the
slight
was not
by other
was informed
approval of
the
and that
satisfactory,
improved construction,
also
measures should be taken to increase the connection, both
of the plates
forming the ring, as well as of parts of the same loosened
and that
by blows.
The second trial against a cnpola plate made
under the influence of such hard shot as those used in
it
appear
likely that,
this trial, the
armour
in question
would break up into large pieces sooner than any part
plate would
be penetrated or loosened.
These plates certainly soon showed through cracks, which, as
of the
in the
glacis armour, all ran in the plane of the least section, but with the great
difference, that so long as the parts of the plate
lose
all
place,
were not so cracked as
to
connection between themselves, no displacement worthy of note took
and not once the
slightest
dislodgement of these parts occurred.
As good properties of the Gruson armour system, the following were
by the trial
{a.) The degree of hardness of the surface was sufficient to prevent
disclosed
:
-
penetration into the plate, even of normally striking shot, and
the system offers consequently complete resistance to perforation,
or anything like
{&.)
The
it.
so-called chill cracks or similar defects on the hard part of
the plate, which were the cause of the
trial,
occasioned no special
disadvantage.
{c.)
Lastly,
it
appeared that after three rounds with such great energy,
and so large angles
of
impact, as in this case, not even
the
was dislodged from the inside of the
this armour offers a protection
the advantages of the simple construction and
smallest piece of plate
armour or thrown inwards, so that
apart
from
advantageous external form peculiar to
this
system
—superior
that of any other system in existence or in construction.
02
to
—
104
[
The
]
forcing through of a comparatively loosened piece of the plate
by the pushing
the fourth round, which was necessarily followed
glacis armour, a necessary result of
exclusively,
be explained by the
as in the case of the
was nowise,
rear of the upper part of the plate,
the form, but must
failure of lateral
by
to the
chiefly,
if
not
connection between the
plates, principally at the lower edge, as also by the fact that one
shot struck a very small piece of the plate already entirely separated by
armour
this defective
This pointed to the necessity of providing against
cracks.
condition as far as possible in the actual structure of a turret.
showed
Further, the effect of the different hits
—
against the
^greatly
original view of the manufacturer, who, however, later on, entirely agreed
with this opinion
of the
armour
—that
was desirable
it
(as far as this could
so to construct the external curve
be done), that normal
hits
should be
almost impossible.
With regard
it
may be remarked
1.
The
trial
contract,
ground
on
decisions
the
to
was made under the very severe conditions
were
part
at such
of the
gained in former
maintained,
a
trials,
conditions which
used
although
For instance, the
point that the part
of
a manner
in
first
was
shot
the plate, below an
had a
imaginary horizontal line through the point of
impact,
mass, by which,
cracking of
relatively small
plate
2.
considerations,
these
which had been accepted by the manufacturer on the
unfavourable to the plates.
aimed
from
:
of the experience
our
arising
by the
The two
first hit
perhaps,
the
can be completely accounted
the
for.
following shots were placed close to the
first hit, but,
notwithstanding these three rounds which were close together,
and struck almost normally, not the
produced on the inner side
slightest
of the cupola,
change
of
form was
nor had a single piece
been loosened either from the plate struck or those adjoining, so
that in reality the
working of the guns could have been carried
on within the cupola without any interruption, a result which must
truly
be termed astonishing.
conclusion of the
trial
The expectations which,
against the glacis armour were
at
the
somewhat
diminished, were by this result after the 3rd shot considerably
surpassed.
3.
The 4th
shot
was directed against a portion
of the armour,
which
was not only completely separated from the plate by cracks, but
Moreover, through the yielding
also was of very small dimensions.
105
[
had acquired a certain amount
consequence the piece of the plate most
of the incompletely fixed plates,
of play,
and became
1
in
it
incapable of withstanding a blow.
Without doubt
is
it
to the
which
mass and the immovable locking together of parts to
nature of armour owes in particular its powers of resistance.
Had
4.
what
not, following
is
stated under
3,
this
a part of the separated
piece hit by round 4 been completely forced out of the armour,
there would naturally have been no consequent falling
the parts lying above
it
down
of
so that the plate, after the 4th round,
;
although injured and cracked, might have been expected to remain
nearly,
5.
The
if
not entirely, in
m.ode
its
original state.
determining the resisting power of the plates
of
previously employed, by adding the total energies developed by
the different rounds, without taking into consideration the angle
which the shot struck,
at
The energy
used, and above
is
of but little value.
of the individual rounds, the quality of the shot
the part of the energy thrown on the plate, due
all,
to the greater or less approach to striking normally,
compose the
proper measure for determining the above-named resisting power.
greater in the
trial
In the usually
and coast
of
demand made on
was considerably
than is actually to be feared in war time.
very short duration of an action between ships
In this respect the
batteries, in
the plate
which the former are limited
ammunition, both as regards number and kind,
expected that four of the same kind should
one plate
6.
at nearly
The circumstance
had
play, forbade
in their
supply
it is
hardly to be
hit close
together on
go° with such an energy as occurred
in this trial.
that in this trial really less favourable factors
coming
to the unreserved conclusion that all
the other cupola plates as well would be reduced by four shots to
the
all
same condition
appear
To
plates
as the trial plate, so that a condemnation of
the other plates on the ground of the result obtained did not
justifiable.
reach entire security in this respect, further
trials
against several
would have been necessary.
As, however, the
trial
had shown already that apparent defects
in the
plate could not rightly be treated as such, although the value of the plate
as
armour had been
called in question
ground for demanding a
cost of the maker.
trial
of the
thereby, the contract afforded no
other plates, entirely or partly, at the
106
[
To
own
]
what was ready for use and paid for
and then replace it by similar material without security
of having for the probably trebled expenditure an armour offering a proportionate increase of resistance, would have been a useless waste of money.
reject lightly at our
most
for the
cost
part,
This was
all
the more so because
armour did not
the
if
satisfy all the
extremely stringent terms of the contract, which the manufacturer had
bound himself
to accomplish,
still
armour
the
in question did constitute the
really best possible material for coast defences available at the time.
Moreover, it appeared very probable that the resisting power of the
armour already delivered could be considerably increased by very simple
means.
On
all
trial, that,
these grounds the manufacturer was informed, the day after the
War
subject to approval of the
Minister,
and irrespective
of all
considerations as to the issue of this test, as well as of the consequent
now made
estimate of the value of the cupola plates
as armour, these would
provisionally be accepted according to the terms of the contract.
condition was added that, as far as
already completed, use was to be
improve the said armour
trial to
substructure,
and
also as
possible, without
made
sacrificing
The
work
of the experience gained in the
in respect to fixing it
on the wrought-iron
touching the danger of the forcing through of
pieces broken loose.
For the armour of the
whole arrangement and
It
was shown
even more
was
forts at
Ymuiden, the improvements
in the erection of the
in the
armour must apply.
also in the three firing trials against the cupola roof plate
clearly, that a
probably general feature of the chilled iron plates
and separated into numerous pieces
and weights by the impact of hardened forged steel shell
that they soon cracked through
of different sizes
—such as those delivered by Krupp.
At the same time it was irrefutably
shown that even in this case no failure of protection ensued, so long as a
displacement and corresponding yielding of the different parts into
which the plate is divided, does not occur.
The claim of the manufacturer that his system of armour owes the
greater part, if not the whole, of its value to the dome or arched form,
which only can be used in this manner, received a striking confirmation
in this trial. The trial gave, therefore, no reason for demanding any
change
in the roof plates already cast or those to
be made, but warranted,
on the contrary, the very valuable assurance that a means of protection
had been found
in the plates
which
offers
a sufficient cover for the safety
and other fire, as well as the
mechanism for laying the guns."
of the interior of the cupola against direct
greatest security to the turret motor and
107
[
]
Committee mentions the changes
In conclusion, the report of the Trial
recommended
in the glacis
These were,
and cupola armour
for the glacis plates^
plates.
an increase
in
weight and thickness,
decreasing and supporting the overhanging part by means of brackets,
and improving the connection between the plates by means
of
wrought
iron keys.
For future cupola
a flattening of the profile curve, increase of
plates,
weight, and adoption of wrought-iron connecting keys.
To
briefly
satisfied the
sum up what has been
said
:
The
glacis plate
had not
requirements, the cupola plate had done so, but for future
construction changes were desirable, whilst the roof plate had surpassed
the tests arranged and had
shown a considerable excess
of strength.
5.—Trial against a Side Plate of a Chilled Iron Armour Turret
cm) Guns 35
for two 15.7 in. (40
On
the Firing
Ground
2oth, 24th,
della Castagna, near Spezia.
Seno
at
calibres long.
and 29th
April, 1886.
Object and Programme of the
Trial.
Test of a cupola plate of a coast turret for two 35 calibre long 15.7 in.
guns, ordered by the Italian Government, by 3 shots from the 100 ton
Armstrong
The
i6.9in.
gun (Type Lepanto).
points of impact to be separated at least
Target
its
of
:
The
turret to
which the
15
of 46.6
metre, or 39 inches.
plate belonged corresponded in
trial
The armoured cupola
chief points to the type Fig. 4.
plates
i
consists
a ring, and has an extreme diameter outside
in
ft.
The
opening,
roof,
is
which
is
provided with a manhole and sighting
put together in two parts, like the Dutch turret, and
has a diameter of 21.7
height of 6.6
ft.
;
ring of glacis armour has 15
The
ft.
plates, which have on the side
of the turret
on the others 4.3
the glacis armour ring
is
64.6
ft.
exposed to attack a
The extreme diameter of
The guns lie in Armstrong
ft.
hydraulic minimum-port carriages.
The
trial
plate
was made
gained in the previous
so
flat
a
profile, that
seemed excluded.
trials,
in
accordance with the experience
and, in correspondence therewith, had
angles of impact of shot of more than 50°
108
[
The
of the
plate
Seno
was
della
]
built into the
limestone rock on the shore
Castagna, near Spezia
(See Fig.
37),
and
rested on a bed plate let into the rock, weighing 40.8 tons.
Fig. 37-
Structure for the Side Plate of the Chilled Iron
15.7 (40 cm)
for two
Scale
:
Armour Turret
Guns.
1.200.
-"
'-Vj
.'>»ll'*.»-'*i
The
side connection to the rock
two specially cast
work.
The
plates,
trial plate
was obtained by means
was connected
to its
plates, as in the construction of the turret,
and grooves.
On
two side-supporting
by means
of tongues
the left side a tongue was cast on to the plate,
which entered a groove formed
tongue was
in the side plate, whilst
on the
and the groove in the trial
In the groove on the upper edge of the trial plate, and in
right the
plate.
of
each 44.1 tons in weight, with masonry
in the side plate
109
[
]
the corresponding recesses in the supporting plates
traverse, representing the roof
was placed a
plate of the turret, 5.2 tons in
weight, which rested sideways, like a wedge, against the masonry.
This
a free opening, by which access could be had to the
left
inside of the armour.
The rock above
about 10
wood
the
target was removed to a height of
This space before each round was
feet.
to diminish the injury to
filled
with
and
the overhanging rock
to
partially protect the target.
The gun was protected against splinters of shot by a strong
wooden screen in front.
The upper part of glacis armour in front of the trial-plate
was represented by a glacis of concrete.
were a number of cracks formed in
shown by dotted lines in the figures, which also
In the trial plate there
casting in
chill,
give the dimensions of the plate.
The breadth
was
9.8
ft.,
upper edge
at the level of the
at that of the
armour plate
6.2
of the
and
ft.,
its
glacis
weight
86.5 tons.
Gun:
Armstrong, 16.9
(Type
in.
(43
Lepanto),
cm),
100
ton
Armstrong
in
gun,
hydraulic
calibres
long
minimum
port
27
carriage.*
order to increase the
In
angle
of
impact, the
base
of
was inclined 1° 29' to the front, and the axis of
the gun was at such a level as to point, with 1° depression,
the plate
at the base of the plate at a spot 8 in.
above the upper edge
of the glacis.
Distance
146.5 yards.
:
Shot: Krupp 2.8 calibre 16.9
cm)
steel shell,
empty, about 2,205
in.
(43
P
(one hole) from the Rhenish- Westphalian
'bs.
in weight.
Charge
827.5
:
lb.
brown
P.
Powder Factory.
Striking velocity (mean)
„
energy
Round No.
Shot
is
A
:
1
:
(
„
:
587 yards per second.
): 47,481 foot tons.
20th April, 1886.
Krupp
shell as above,
weighted with sand and lead to 2,205
'b.
* The gun was placed in a pontoon anchored to the shore. A good description of the carriage
found in the Mittheilungen Tiber Gegenstande des Artillerie und Genie Wesens 18S3, page 34.
further description
is
given in the "Italia Militare" and Engineer 1883, page 73.
[
Velocity
<u
:
110
]
At the muzzle, 591.5 yards.*
„
93 yards from the muzzle
„
At
the target:
:
588.7 yards.
587.1 yards.
111
[
Point struck
8 in. right of centre line.
:
46.4
Angle
impact
of
A
Effect:
J
{See Fig. 38.)
above upper glacis edge.
in.
44° 30
:
18 in. long, 13.4 in. broad, and
chiselling of the surface
deep.
2 in.
Also the following
A
:
crack a 0.2
edge of the
crack c 0.3
in.
wide from the points
A
plate.
of
impact to the right
wide running downwards to the
in.
and one horizontally
and
e,
At the point struck
A
of the surface.
A
hair crack b to the right plate edge.
finally
some short
there were
some
right.
A
crack
d
hair cracks.
insignificant abrasions
scaling off of the surface at the lower part of
c, which ran close below the upper layer of the surface,
and separated a piece therefrom of 4 in. greatest thickness was
more important.
crack
Back
of the plate
At
:
the back of the plate {see Fig. 42)
only one crack was found proceeding from the right edge of the
plate,
and ending about
From
the
position
1
the
of
above the lower plate edge.
1.8 in.
crack,
it
nected with the crack in front marked
General
target
in.
condition of
showed that
it
was assumed
the target.
had moved
An
slightly, as
owing
trial.
to the destruction
Shot
by the blast from the gun
was moored.
:
shot broke up.
2: 24th April, 1886.
As
in
Round
I.
Velocity at the muzzle
592.3 yards per second.
at 93 yards from the muzzle
,,
at the target
„
Energy
of
impact
Point struck
:
:
:
:
589.4 yards.
588 yards.
47.632.8 foot tons.
19.7 in. left of centre line.
27.6
31.5
Angle
:
of impact:
in.
above edge of
in.
from
48°
hit
No.
its
two
no way prevent
This, however, had to be suspended
stage to which the pontoon
The
con-
openings about 0.04
wide had been formed between the armour plate and
the continuation of the
it
examination of the
side supporting plates which, however, could in
Round No.
that
a.
I.
glacis.
of the
wooden
[
112
]
UiHlHIHIHHii'
o
g
Ss.
^
s
s
>
:A
113
[
Effect:
Surface excision
maximum
in.
0.3 in.
mean
The cracks a and
abrasion between hits
g
width,
0.6 in.,
h
0.2 to 0.6
in.
0.4
in.,
to 0.4
in.,
in., i
were widened on an average
c
i
Deserving of mention was an
to hit 2.
and
which, running obliquely on both
2,
had a depth
sides to crack a,
0.8 to
and 4
broad,
width, as also several short hair cracks.
and the former extended
At
13.8 in.
running radially from the point struck to the edge.
Cracky
I
long,
15. 8 in.
depth, surrounded by irregular abrasions of the upper
layer, also
and k
1
of 1.2 in. to 1.6 in.
the upper edge of the glacis a small three-cornered piece,
was knocked out (marked
1.2 in. large,
also a four-sided piece
The
greatest
^ under
number
hit
x' in
Fig. 38), as
i.
of cracks ran with the strong projecting
lower part of the plate, but, on account of the glacis covering,
it
could not be seen whether they reached the lower edge of the
Cracks h and
plate or not.
i
apparently ran under the upper
layer and joined in the interior with d, as the piece of plate
bounded by these and crack k was pushed out about
k had a width of
i
in.
or a depth of 1.6 in.
confirmed by the fact that cracks h and
of 0.4 in. to 0.6 in.
were not
Back of the plate
round was extended to
off
visible at the
(Fig.
42)
:
i
in.
back
of the plate.
high,
in.
2.4
wide
in.
in.
at
above the lower edge appeared a nearly
in.
wide, with a branch to
the left and another to the right, running into crack
ing apparently with exterior cracks, f, g and
quently marked with these letters in Fig. 42.
In other respects, the back of the plate
General state of the target
between the armour plate and
:
its
On
was
k,
a,
connect-
and conse-
quite intact.
examination, the
right supporting
o.i in., whilst the left joint
joint
plate
remained 0.4
in.
was
wide,
was cracked at a level of 27.6 in.
edge which crack however was not discoverable
also the left supporting plate
inside the target.
first
thick.
Also about 19.7
above the glacis
and
notwithstanding a M'idth
crack a formed by the
horizontal zigzag crack, 0.06 in. to o.i
found widened
in.,
the lower edge of the plate, breaking
a small three-cornered piece 8
bottom, and
/
0.8
Thii supposition was
[
114
J
a
bo
o
o
s:
CL
£
o
115
[
]
In presence of this general loosening of the structure of the
target, the
manufacturer had the
right,
contract, to postpone the third round
by the terms
until
the
of
structure
the
was
again consolidated.
As
and the plate by
excess of resisting power seemed able to
its
would have occupied a long time,
this
bear the 3rd round without additional support, the manufacturer
waived
and the 3rd shot was delivered without repairing
his right,
to replace the
the structure further than
wooden
pier broken
previously.
The
Round No.
Shot
:
shot broke up.
3: 29 April, 1886.
As
Rounds
in
and
I
Velocity at the muzzle
S90.3 yards.
93 yards from the muzzle
at the target
586 yards.
at
,,
„
587.5 yards.
:
:
Energy
at impact: 47,322.7 foot tons.
Point struck
4
f
in. right of
90.5
44
Angle
:
II.
of impact:
Effect: Excision
in.
in.
centre line.
above glacis edge.
from Round No.
I.
35° 30'.
15.7
in.
long,
11. 8 in.
broad, and 1.6
in.
deep^ with
surrounding abrasions also running radially from the point struck
to the edges hair-cracks
/,
m,
n, 0,
p, and a vertical crack q 0.2
in.
want of lateral support the upper
was forced downwards a little, so that the under
parts stood out along crack a about 0.4 in. and along crack e
about 0.2 in., and, in consequence, at the right edge a large piece
of plate, seen in Fig. 38, had broken away and was pushed out.
The greatest thickness of this fracture was 10 in., the other
wide.
In consequence of the
part of the plate
dimensions are seen
No
in the Fig.
widening of cracks formed by the previous rounds had
occurred.
[
s
o
116
J
117
[
^'^'
]
^'
Back of the Trial Side Plate
Back
,
of the plate
A
:
new
after the third round.
crack running upwards -and to
Scale: 1.60.
29/4/86.
was
the left from the centre line
seen apparently
connection
in
the hair crack
with
front surface
to the lower
on the
/
k was lengthened
;
edge
of the plate,
and between k and b a nest of
several small cracks had appeared
owing
links
rechlsi
which a small wedgepiece weighing about
to
shaped
4.4
shown
lb.,
in
dotted lines, had
from the inner surface.
fallen
measured
3.5
Close
by
4.3
by
It
3.2 in.
there was a
to this
small surface abrasion about 0.4 in. deep.
The sinking
the
of
upper
part
of
the
plate
was
also
observable on the interior of the plate, the upper part of which
stood outwards along cracks
0.8
and
in.,
a,
and
k
General condition of the target
between the armour plate and
two
first
on the
the
about 0.6
in. to
0.9
in.,
its
:
The openings
in the joints
side supports formed
by the
rounds had, by the sinking of the former, closed up again,
left
As
/,
0.2 in. respectively.
completely, on the right to 0.4
in.
wide.
the 3rd round completed the stipulations of the contract,
trial
was stopped, although the
plate doubtless
would have
withstood further shot.
Sumniary
:
The
shot broke up.
The
plate under trial had in every respect complied with the
conditions of the programme.
These maybe considered extremely
gun used in the trial displays
severe, as the energy which the
under normal conditions, at the same distance,
tons (charge 772
lbs.
Italian
powder;
shot,
is
only 44,251 foot-
weight 1,841.2
but in this case was increased by using a heavier charge.
lbs.),
Further,
the small distance between gun and target, which alone rendered
possible the development of so high an energy,
sidered
;
and
lastly,
the
number
as very large, in respect of the fact
most powerful
in existence,
must be con-
must be looked upon
that the gun is one of the
of rounds
and that the cupola,
of
which the
trial
118
[
plate
it
was a
]
section, consists of 15 similar plates; and, moreover,
may be added
were proportionately
that the points of impact
very near each other.
The
energy
three rounds which struck the armour represented an
of 142,465.6 foot tons, or 1,618.2 foot tons
The
of plate.
per ton weight
however, did not suffer to such an extent as
plate,
appear incapable of withstanding further shot of the same
to
calibre,
and
it
has to be added that the third round was received
under very unfavourable conditions, as the
Nevertheless, the cracks
failed.
were
of very small dimensions,
visible at the
The
back
chill
lateral
support had
caused after the third round
and only
in the slightest
degree
of the plate.
previously existing in the plate proved
cracks
themselves to be, as in
all
previous
trials,
The
absolutely without effect
on the endurance of the
plate.
crossed the former in
directions without once following their
all
cracks formed in the firing
course.
The
profile of the plate as selected
was proved
to
be correct.
The
penetration of the shot was proportionately very slight, and
the
cracks formed were neither so numerous or so serious as
might have been expected from the severity of the attack.
Krupp's
as
steel
shell
showed the same excellence
usual with the smaller shells of this firm.
is
broke
in
pieces on striking
whole after striking
no shot having ever yet remained
;
chilled
of material
Naturally, they
armour obliquely.
6.— Second Trial against the Side Plate tested in April, 1886, for a
Chilled Iron Armour Turret for two 15.7 in. (40 cm) Guns,
35 calibres long.
On
the Firing
Ground
at
Seno
della Castagna, near Spezia.
22nd June, 1886.
Object and Programme of the
To supplement
Trial.
the results obtained in April,
1886,
by testing the
behaviour of shot of different calibres and manufacture on striking the
armour already
chilled
The new
16.9
in.
pieces,
tried.
was occasioned by the circumstance that the three
had broken up on striking the chilled armour into small
firing trial
steel shells
whereas
in earlier trials
Krupp's
5.9 in. shell
iron plates without showing the least deformation.
had perforated wrought
119
[
Doubts had
consequence arisen whether Krupp's 16.9
in
same good
of the
]
quality as the
shells
of smaller
suggestion of the Trial Commission, the Italian
continue the
still
with several Krupp 5.9
trials
steel shot of St.
Chamond make
calibre,
shells.
in.
and, at the
Minister decided to
a 16.9
First,
in.
(France) was to be fired at the upper and
intact part of the plate, so as to
Krupp
War
were
in, shells
compare
effect with those of the
its
shell.
The
Gruson
was, therefore, chiefly as a test of projectiles, for which the
trial
chilled
War
already definitively accepted by the Italian
plate,
Minister, served as a target.
Target
The
:
structure
shown
in Fig. 42,
and previously described,
had seriously suffered by the preceding
the armour plate and
latter
its lateral
trial,
between
so that
between the
supports, as well as
and the masonry, openings had been formed
at the joints.
In order to restore as far as possible, the lateral support, these
openings were now
poured
Weight
Gun:
of the trial plate
:
Armstrong's 5.9
I,
filled
with steel wedges, and zinc was also
in.
86.5 tons, kg.
in.
cm) gun, 28 calibres long,
(15
in
Albini
carriage.
Armstrong's
2.
16. 9 in. (43
Both guns
Distance
in the
cm) 100 ton gun, as
in last trial.
pontoon moored to the shore.
146.5 yards (134 metres).
:
Shot: Krupp 5.9
steel shell, 2.5 calibres,
in.
Chamond
a St.
weight 79.4
lbs. (36 kg.),
and
16.9 in. steel shot 2.5 calibres long, weight 2,205 'bs.
(1,000 kg.)
To facilitate
reference in the following account, the numbering
and the lettering
of the shots
of the cracks follow those of the
(See Fig, 38).
last trial.
Round No. 4:
Shot
Krupp's
:
Charge
:
32.2
steel 5.9 in. shell,
lbs.
progressive Fossano
Velocity at impact
Energy
Angle
Effect
of
:
:
34
impact
in.
:
powder
weight 79.4
(0.8 to 0.9 in
lbs.
)
546.5 yards per sec.
:
right of the centre line, 52
in.
above the glacis edge.
44°
Unimportant abrasion
Back
calibres,
1482.6 foot tons.
„
„
Point struck
empty, 2.5
of the surface at the point struck.
of plate unaltered.
Shot broke up.
H2
[
^
120
]
121
[
]
Ronnd No. 5:
Shot
As
:
Charge
:
before.
39.7 lbs. progressive Fossano
Striking velocity
powder
(0.8 to 0.9 in.)
616.4 yards per sec.
:
energy: 1886,3 foot-fons.
„
Point struck
40
:
in. right
of the centre line, 9 in.
above the glacis
edge.
Angle
of impact
50°
:
30'.
Effect: Abrasion of surface 2 to
It
4
appeared that cracks b and
in.
deep between cracks
b
and
c.
c ran superficially under the upper
layer of the armour, as the plane of fracture of the abrasion
was
covered with a layer of rust.
Back
of plate
unchanged.
Shot broke up.
As both
the 5.9
in.
shells
Committee considered the
proceeded with the
had broken up on striking the armour, the
first
firing of the
part of the
programme was
satisfied,
and
Armstrong 100 ton gun.
Round No. 6
Shot:
Chamond
St.
steel
16.9 in.
shot,
2.5
calibres
long; weight
2,205 ^^•
Charge
:
827
Powder
one-hole
lbs.,
Velocity at the muzzle
at the target
„
Energy
of the shot
Point struck
brown
P.
P.
(Rhenish-Westphalian
Factory).
:
:
589 yards.
584.7 yards.
on impact
:
47,167.7 foot tons.
Aim was taken on
:
the upper and
still
intact part of
the plate.
20
in. left of
89
in.
the middle line.
above the glacis edge.
(See the cross in the diagram of
movement
of the
In consequence of the
hits).
pontoon by the waves, the shot struck too low,
exactly on hit No. 2 of April 24.
20
in. left of
27.6
Angle
of
and
above the upper glacis edge.
in.
impact
the centre line,
:
The
shot struck a
much
injured point, where the
surface presented a nearly vertical plane.
[
to
s
o
00"
bo
[i,
s
•5^
g
k^
^
Co
'SI
122
]
123
[
The angle
of
]
impact was therefore apparently between
80''
and 90°.
Effect
The
:
shot struck out of the plate between cracks e and
already existing,
maximum
20
a number of pieces of different thickness
in.)
Crack p was lengthened
thrust outwards
Back
therefore,
m
to
which pushed the piece y,
e,
by the previous shooting,
of the plate
with cracks
g
(in
and
:
Two
to the right.
fresh cracks, probably connecting
on the front
n, visible
marked with the same
of the plate,
and
are,
Also a short crack r
letters.
in
the left pillar.
Between cracks k and
out of the surface 27.6
in.
appeared a wedge-shaped
b
broad, 8
high,
in.
and
splitting
6.3 in. deep.
loosened pieces had fallen perpendicularly and so were not
Between crack a and the
lodged.
three-cornered piece, 8
about 2.4
in.
The
dis-
right edge of the plate a small
long in the side, was pushed out
in.
The lower
part of the plate
along crack d about 1.4
1)
)i
„
„
J
r
was forced inwards by
the shot
in.
>>
2.4
))
„
1.6
,,
beyond the upper
part.
The displacement of the left pillar took place along the previous
crack
whose under part appeared
k,
on the front surface, but
visible
to connect with cracks i or
the
displacement
h
was not
observable on the front.
General condition of the target
whose
of
:
The
left
supporting plate,
had suffered considerably from glancing pieces
showed a through crack opening 0.4 in. to 0.8 in,,
front surface
broken
shot,
as also the upper traverse which took the place of a roof-plate of
a
turret.
The upper
part of the plate was, notwithstanding, in close
contact with the supporting plates, and
still
possessed adequate
power of resisting other shot from the same gun, but the trial had
be discontinued as no further 16.9 in. shot were at hand.
to
It is
last
to
be noted that the heated pieces of the shot at the
round set
fire
to the timber baulks of the screen in front,
which was speedily consumed.
The
shot broke up.
t
Back of
124
the Trial Side Plate of the Chilled Iron
Turret for two
\t,-T
ifi-(\o
cm) guns after
Scale
22/6/86.
:
]
Summary
Armour
more that
1.60.
The
:
first
part
had showed once
O^ the trial
the sixth round.
steel shot of small
up on striking
calibre break
an oblique surface of armour,
16.9
way
same
the
in
in. shell fired in
as
the
April.
The second part of the programme produced no tangible
result, as the St. Chamond
shot struck the cracks on the
redds
most injured part
and a comparison
linlcs
of the plate
of its effect
with that of the Krupp shell
was
in
consequence excluded.
This shot was, nevertheless,
of great interest,
the
little
showing how
time of breaching a plate can be judged by cracks
whose point of striking was marked by
a circular and on the right and below, sharply edged erosion of
the surface, hit a part of the plate already much injured by
round 2, and its angle of impact must have been between 80°
already formed.
and
90'^,
The
shot,
which was proved by the
the shot were not deflected
fact that the
broken pieces
upward on the curve
but were thrown directly at right angles to the
left,
where they
Not-
injured the projecting part of the side supporting plate.
withstanding
this,
the armour withstood also this round, or an
attack in total of 192^970 foot tons, that
per ton of plate.
back
The
is,
same by the
2,196.5
foot
tons
dislocation of the left pillar, visible at the
of the plate, must, in consideration of the
of the
of
of the plate,
earlier rounds,
weakened support
be reckoned as inconsiderable.
Without doubt the whole upper part
of the
armour would
have been equal to further shots from the same gun, and
be consequently affirmed that the
trial
it
may
plate possessed a resisting
capacity considerably in excess of what was necessary against
the attack of even the loo-ton gun.
Any
Chamond
difference
steel shell
between the material
of the
Krupp and
St.
could not be determined on account of the
facts previously stated.
125
[
]
CHAPTER
IV.
Comparative Analysis of the results obtained, and
Conclusions.
THE
result of
the
series
of
trials
is
best
dimensions of the armour which were
shown by the
finally
profile
and
designed in consequence
thereof.
The
against armour for inland fortifications, and those
firing trials
against coast defence armour, described on pages 45 and 76, afford this
information.
and from the
From
the former arose the armour profile, shown in Fig. 25,
latter the profile of the plate tried at Spezia,
given in Fig. 38.
Both profiles proved at the trials to be correct, and both agree in regard
to the external curve.
—neglecting the
Comparing the
the profile of the
last
mentioned, the later
trials
which Gruson, by the
for the first
We
change
Tegel
Tegel turret
first
dimensions for the
(Fig.
10),
we
moment
—with
find that, as already
brought them back to a profile similar to that
results of the preliminary experiments,
had chosen
turret.
have before stated the reasons which seemed to necessitate a
in this profile,
and
shall later
on have occasion to give them more
in detail.
To form an opinion of the results of the trials it is indispensable
compare them together, and we have consequently drawn up the Table
data of the
trials to
The Table
to
of
be found at the end.
contains, in the columns 3 to 9, the guns
in the attack at the different trials, the figures
and charges used
being extracted directly from
the reports of the trials.
10 to 21 contain the chief dimensions and weights of the
The columns
plates tried, either taken from the drawings or calculated from them, and
for the
value
most part
when
it
left
can
other material tried.
out in the
be
official
reports, as each figure
compared with
the
is
only of
corresponding figures of
126
[
It
may be asked
]
beyond the thickness and the
if
profile of a plate there
are other proportions requiring consideration.
In the literature of chilled cast-iron
armour these are not given, and even
the empirical formula for finding the thickness of chilled armour follows
by
analogy the formula for determining wrought-iron armour, and neglects
the other dimensions.
we
If
reflect that the destruction of chilled
takes place not by perforation, but only by breaking up, then
dimensions seem more or
easier within
certain
be of value, as
less to
say within certain
has been always
of the
limits, for
same
thickness.
a limit doubtless exists, and indeed
we presumed, from
if
must without doubt be
and respected by the Constructor.
felt
promise too much
the
all
break up a small plate by cracks into
limits to
numerous pieces than a large plate
We
it
armour
the
i8 firing
We
should
to exactly
trials,
define the most favourable dimensions to give to an armour plate, but
it
nevertheless seems well worth while, in so entirely empirical a subject, to
closely
examine the
We
results of the trials, so as to obtain a clear view,
if
what these dimensions should be.
possible, of
now proceed
examination of the Table, and remark, in
to an
passing, that the figures given for the
first
made use
complete the Table, and are not
of,
Tegel turrets are merely to
as a rule, in our comparative
analysis.
The Proportions between the Greatest and Least Thickness
1.
of the
Armour.
In columns lo and
1 1
of the
Table
we have placed
and least thicknesses of the plates of armour tried.
the profiles shows that the greatest thickness
level of the centre of the port,
and the
is
together the greatest
A
comparison with
throughout found at the
least at the
upper edge.
The few
variations are given in the Table.
Column
radial
12 contains the proportion of the smallest to the greatest
thickness, a proportion
endurance of the
which has the greatest influence on the
plate.
In the Tegel turrets for land fortification, these figures vary
I
:
2.3
and
between
In
i
I
:
the
:
2.5,
1.3
and
and
earlier
i
in the later plates, for the
:
same
I.7
plates,
coast batteries,
the
proportion
(excluding the roof plates); in the later plates between
(excepting the glacis
between
class of fortification,
armour
plates).
i
:
1.4
was
and
i
:
i
;
2.6
1.7
127
[
The decrease
recent types
is
]
upper part
in the thickness of the
of the plates in the
way
so small that the respective figures point the
to a
comparison between the behaviour of older and newer armour plates.
led
As already
to the same
commencement
stated in the
profile as that
of this chapter, the later trials
chosen for the
first
Tegel
This early
turret.
had been g^ven up because chilled iron shell used against the upper
oblique portion of the plates had a greater effect than those hitting the
profile
lower and more perpendicular part.
This fact was made apparent at the
Tegel
turrets,
and
is
confirmed in the
"
second question
is,
first
and second
Proceedings of the Engineer
Committee," so that there can be no doubt about
A
both the
of
trial
it.
whether the explanation commonly given, and
adopted by ourselves, of the circumstance that chilled iron projectiles shiver
into atoms on striking normally, but break up into large pieces when
striking obliquely, which pieces
correct.
injure the
In presence of the figures of
upper part
column
weak
hits was
opinion that the earlier plates were too
that the greater effect of the oblique
12,
we
in their
of
the plate,
is
incline rather to the
upper portions, and
and
entirely due to this fact,
not to the material of the projectiles used.
Major Kiister remarks, on page 28
of
the
Proceedings, that the
Experimental Committee recommended that the thickness of the plate,
They proposed at
less rapidly.
sharper
curve,
a
more
perpendicular
by
means
of
a
the same time to give,
profile to the lower part and a more oblique one to the upper, and stated
from the roof downwards, should decrease
that the cracks had, generally, originated with glancing shot.
for a
that
The demand
more perpendicular lower section apparently rested on the assumption
normal hits had less effect than glancing ones, and this demand was
perhaps the cause of the frequently given explanation of the varying
behaviour of the projectiles.
The
is
figures of
column 12 seem to us
to
show
that this explanation
not correct, inasmuch as no solid reasoning can be adduced
shot hitting normally should have less effect than a glancing
why a
Also,
hit.
the explanation that the larger pieces of chilled projectiles did more
to the
upper part
of the
armour than the smaller pieces did
seems to us incorrect, as the
to
harm
the lower
earlier reports of trials expressly state that
the cracks began with the glancing hits, but the cracking of the plate
must be independent
of
the greater or less injury to the surface,
be chiefly proportional to the strength of the blow
thickness of the armour.
in relation
and
to the
;
[
We,
spite of
lastly,
steeper profile, but was,
its
due to the dissimilar greater thickness of
it,
Tegel Turret
consequence of erroneous assumptions, that the success
in
second Tegel turret was not due to
of the
and
]
therefore, are of opinion that the profile of the first
was discarded
in
128
that the
Tegel turret was
cracking noted
due
to
the
plates
decrease in thickness of
too rapid
still
the
upper part of the second
the
in
this part.
2.—The Proportion of the Expanded Length of the Unprotected
Part of the Profile Curye to the Greatest Expanded
Breadth of the Armour Plates.
Before mentioning this proportion, given in column 13 of the Table, a
word may be
said as to the reason for calculating this ratio.
under-
It is
stood at once that a narrow plate will not resist shot so well as a broad
plate of the
same
and
profile,
establish a proportion
for this reason
between the
would seem desirable to
it
and the breadth.
total length
This,
however, was found to be impossible, as the profile curve at the base of the
plate
makes a sharp bend^ and
taken into consideration
it
the profiles, to a false estimate
curve throughout
is fairly
the whole curve from top to bottom were
if
would
;
lead,
owing
to the different character of
but on the upper part of the plates the
regular,
and can be well made use
of in obtaining
a ratio with the breadth.
column 13 the
In
given as
1:2;
in
Tegel turrets
ratio of length to breadth in the
the later armour for coast batteries, VI. to
becomes (excepting the
glacis armour)
half-port plates of the batteries
show a
i
:
1.8 to
i
ratio of
the length was greater than the breadth, which
i
and only the two
0.9.
In the last, too,
is still
more apparent when
the part of the plate's profile covered by the glacis armour
This
ratio,
which
differs
from the others, had
this
2.3,
:
:
XL,
is
its
own
is
reckoned.
special reason.
In the battery plates the port occupies a large proportion of the external
surface,
and
in
consequence, in the relatively slight parts above and below
the port, the metal
left
is
by the casting
facilitates the early formation of cracks.
8.3 in. battery in 1873
reason
it
—
in
a state of tension, which
For example,
74, cracks of this nature
in the trials of the
were formed, and
for this
appeared preferable to divide the plates down the centre, and to
obtain the accurate connection of them by keys placed therein, submitting
in this alteration to the
We
undoubtedly unfavourable loss of weight and mass.
find greater differences in the coast
in that for inland forts.
armour
(XII. to XVIII.) than
_
129
[
1
For instance, comparing the rdof plates (XIV., XVII.) and the
(XV.),
plates
breadth of
i
we
find
1. 4,
and
:
the older battery plates a ratio
in
in the later turret plates
These varying figures have
well
the weight of
as
the
the
weight by
:
0.9 to
is
the bridges
0.6.
The form
as
governed
and other railway
and as the length
of the plate
profile cannot be diminished, the breadth must be kept down.
battery armour this
is
only
a
withstand
:
Gruson armour plates are transported on special wagons,
that for the Spezia plate having 12 axles,
to
i
by the
the railway truck and
plates
the size of
the carrying capacity of
All
structures.
i
also their special reason.
heavy armour
The form by
conditions of transport.
from
it is
glacis
length to
of
In coast
not of great importance, as they are called upon
small
relatively
number
of
The
shot.
fact
is
Dutch as well as the Spezia plate only horizontal
characteristic that in the
or oblique cracks were formed and not vertical ones, as observed in the
higher
which
plates,
is
natural,
as the vertical section
is
very large
in
proportion to the horizontal section.
3.—The Proportion of the
Tertical Section to the Front Superficies
of the
The
Plate.
ratio of the vertical section to the
the plate
give the
Armour
expanded front
given in columns 14 to 19 in two forms.
is
amount and
ratio of the total superficies
and
superficies of
Columns 14
to 16
total vertical section,
whilst columns 17 to 19 exhibit only the ratio of the part of the surface
The cause
exposed to shot to the corresponding vertical section.
two-fold ratio
is
shot possesses a uniform curve, the rest
making a sharp bend under the
glacis armour, but the figures in columns 16 and 19 show so
that
we may
the
falls in
armour) to
i
little
difference
confine our analysis of them to those in column 16.
In the second Tegel turret
which
of this
again the fact that only the part of the profile exposed to
:
7.6 to
The reasons
and we leave
newer
it
i
:
we
find the ratio to
be
i
:
11
and
i
:
12.2,
turrets for inland fortification (excepting the glacis
6.8,
and
in battery plates to
for dividing the battery plates
to be gathered from
i
:
3.8.
have already been explained,
them whether the plane
of section,
preserving nearly the normal weight, might not have been increased.
As regards
the
newer
turret plates (VI., X.
and
XI.), the proportions,
notwithstanding the decrease of superficies in relation to the Tegel plates,
was, without doubt, more correct, as horizontal cracks, in particular, were
not formed
in
them.
130
[
]
That, with the same vertical section, a broader and heavier plate
possesses a greater proportion of resisting power than a narrower and
lighter plate
we
is,
think, a certainty,
casting the former.
trial
what
is
It
would only give
is
avoided in
is
by-
the best ratio of the vertical section to the superficies for a
given constant weight.
it
a state of tension
if
would, however, be of great interest to establish
Such
reliable results
fortunate that such
trials,
however, would be very costly, as they
conducted on a large
if
scale.
In consequence,
though interesting, are not absolutely
trials,
necessary, as the proportions of the plates tried (VI., X., and XI.) proved
generally favourable.
In particular, the last
named
displayed such resisting power, that practically
whether
the
it is
plate of
new
profile
really not in question
same endurance would have been reached
had
a small
reduction in weight been made.
We
consider the ratio of
superficies to be correct, as
it
i
:
between the
7.4
seems to
offer a
vertical section
and the
guarantee against the pro-
duction of a state of tension in the casting.
In the earlier coast
turret plates in question
armour the
it
was
i
:
was
ratio
and
1.3
i
:
i
6.9
:
;
with the two
As already
2.2.
new
stated, the
form of these plates was governed by the necessities of transport, and as
the Spezia plate showed a considerable excess of resisting power,
a matter of
resisting
little
moment
it
becomes
with the same vertical section, the
whether,
power would have increased
to a certain extent with the breadth
or not.
4.—The Proportion of the Energy of the Attack
Armour
of the
most important
factor
desirable to establish a ratio
in
its
the attack expressed in foot-tons.
of the
amount
and though
this
the
resisting
between
We
this
weight of
power,
a plate to be
which
weight and the
makes
it
energy of
obtain thereby a sort of measure
of the unit of attack in relation to the size of the plate,
measure may not be
of great accuracy, the figures are of
interest as completing the data relating to the trials
Had
Weight
Plates.
As already mentioned, we consider
the
to the
the various plates been fired at
until
made.
they were breached,
it
would have been best to establish a proportion between the total energy
exerted by the whole number of hits and the weight of the plates.
This breaching was only effected in particular cases, so that it only
remains to proceed on the assumption that armour of the same character
—that
is,
for inland or coast defences
—
is
intended to withstand approxi-
131
[
mately the same number of
number
to be exposed
must vary with
of
(This assumption
hits.
correct, as the
]
is
rounds to which a turret
Among
position.
its
only conditionally
may be expected
the turret plates
however, no such great differences arose as to need special con-
tried,
sideration
in
attack which
withstood
had
a plate
to
whilst
expect,
measure
only gives a
ratio
only be ascertained from
can
it
Our
respect).
this
a
manner
the
the
of
which
in
it
comparison of the firing
results.
We
in
pass to a consideration of columns 20 and 21 of the Table,
now
which are given the weights of the plates with reference to the energy
per ton of plate.
For the port plate
of the
second Tegel turret
this
simply expressed, as a change was made from the 5.9
and ordinary cast-iron as well as
same
side plates of the
turret
we have
per ton of plate, which in the later
108.2 foot-tons, falling again in
It
chilled iron shells
XL
in. to
cannot be
the 6.7
were used.
in.
gun,
For the
the figures 43 and 43.2 foot-tons
trials {VI. to X.)
trial
ratio
become
76.3, 81.9
and
to 35 foot-tons.
appears from this that the work thrown on the metal of the plates
VI. to X. of the Table, was extremely high in comparison with
in the trials
that of the Tegel trials, even excluding the difference in the quality of the
shot.
The
first
ratio
between the weight
time restored in
trial
XL,
and the attack
of the plate
the favourable issue of which
is
for the
was due not
only to the good profile adopted, but also to the greater weight of the
plate.
The
performance of the plate
total
Tegel side plates
is
In the latter the
first
was produced by rounds 37
on
its
whole
half section
plate.
No
in
comparison with the two
therefore of interest.
through crack from edge to edge of the plate
to 39.
from steel
The new
shell,
plate (XL) received 20 hits
equal to 40 shots distributed on the
crack through from
edge to edge was formed, and
although the formation of such a crack
may
not be considered as an
unconditional measure of the resistance of the plate,
state that the total
older one,
exceeded
showed that
the
armour
is
its
superiority
projectiles used in
It
endurance of the later plate
we
think
we may
in respect to that of the
construction and material had more than
of
the
the respective
steel
shell
over
the chilled iron
trials.
evident that the ratio of the attack, in the case bf the heavy
for coast defences, to the unit
of
weight can be carried much
higher, as these plates are only liable to be struck
by a few
projectiles.
132
[
With
1
the older sort of coast defence plates, the attack, as seen in our
These
Table, increases from 128.9 to 1354, and 151.6 foot-tons.
however, are small to those of the later
trials,
between 205.6 and 548.9 foot-tons per ton
our ratio
If
of plate.
may be
accurate, which
is
is
enormous.
exactly,
was the case
Spezia
in the
Several points, however, have to be considered in
this respect before attaching value to
Speaking
question, then the
called in
attack of 548.9 foot tons per ton of plate, as
armour,
XV.
figures,
to XVIII., which vary
our
ratio.
cannot be said
it
many
armour, a plate has withstood so
that,
the
in
trial
inclined
of
foot-tons of energy, but only that
a vertical plate in the place of the one fired at would have resisted such a
number
of
This advantage applies to
foot-tons.
according to their curve of
in
profile,
armour,
chilled
all
greater or less degree, and can,
consequently, be neglected in comparing different forms of this nature of
armour.
On
the other hand there
is
a factor which cannot be neglected
every
:
projectile shivers to pieces on striking chilled cast iron armour, and, con-
sequently, cannot deliver a greater blow thereon than that which
to break
up the projectile into the pieces into which
difference in the effect of
an inclined
strike
two shots
of the
same
size
it
and
plate, as well as the different energies
is
necessary
The
separates.
quality
which
due to different
charges of powder, would, consequently, be proportionately small, supposing
each shot broke up
in the
same way
into small pieces
;
but
it is
a matter of
with increased energies, the breaking up
no doubt that with shot
fired
or similar deformation
more complete, and the blow delivered on the
plate
is
is
also greater, but this last in
no way increases directly with the
energy of impact, but after passing a certain limit increases more slowly the
higher the energy
An
an
increase in the
increase in
calibre
the
may
be.
power
and a better quality
principal
of the attack consequently
seems to follow
the energy of impact only in a secondary degree
influencing
—
of shot
that
factors
in
is
;
toughness and hardness
augmenting
the
power
a larger
—
^being
of
the
attack.
If
why
we examine
the Spezia trials from this point of view
the Gruson factory confidently exposed
the
we understand
plate to the enorm'ous
attack of 548.9 foot-tons per ton of plate, as, in reality, only that part of
the blow would be borne by the plate which was necessary to break up the
shot.
How
great that part was could neither be assumed nor calculated,
but in no case could
it
be equal to the
total energy.
133
[
A
third factor to be
mentioned
J
in this connection,
to
which
lately
considerable importance seems to be attached, as regards the effect of the
attack,
the form of the shot.
is
In
papers
technical
it
frequently stated
is
that
cylindrical
armour
cannot be considered as absolutely inferior to inclined armour, seeing the
latter
can probably be overcome with flat-headed projectiles.
We
have carefully examined the
trials
with this kind of shot, and do
not deny that flat-headed shot have a greater effect on inclined armour
than pointed ones, and
we admit
at the
same time that by placing a point
be obtained
of soft metal on a flat-headed shot, accuracy of flight can
without interfering with
its
efficacy
on
striking,
but
we
cannot hold the
superiority of the flat-headed projectiles to be so great as to
believe that this
importance
superiority
in the
is
sufficient to
call
make
us
a change of any
for
present relationship between gun and armour.
Even
flat-headed shot are always broken up on striking chilled armour, and
consequently only give out on the plate that portion of their energy which
corresponds
to
their
power
of
resisting
fracture.
This
portion
will
probably be greater than in the case of pointed projectiles, as the
headed shot
effect will
flat-
bite better into the surface of the plate, but the increased
probably be shown
in greater injury to the surface of the
and not have great influence in forming cracks, which mainly
the weight of the blow inflicted.
Certainly,
the effective component
of
armour
from
arise
the total energy, as regards
must only remain a fraction of that energy, and the relation
betw^een flat-headed shot and inclined armour will consequently never equal
inclined armour,
that of pointed projectiles against vertical armour.
A
certain excess of
power being always provided for in the construction of the chilled
armour, as was shown to be the case in the various firing trials, we
do not think that the employment of flat headed shot would render any
increase in the weight and thickness of the armour necessary, even if no
resisting
technical difficulty stood in the way.
Reverting
now
to the
main point
of our
argument,
it
appears that,
as that portion of the energy delivered on the plate by the projectile can
neither be estimated nor calculated, so the relation between the energy
and
the weight of plate can be used as an approximate measure only in the case
of trials
where shot
This condition
trials,
of the
is
not
same
quality and calibre are used.
fulfilled
when comparing
the earlier and later
as the chilled iron projectiles used in the former were far inferior to
I
134
[
the steel shell employed in the
endurance was
and the demand on the metal's
latter,
the greater in the later
all
trials, as,
amount
dissimilarity of the projectiles, the
on the plate was much
chilled shot
]
less
corresponding to the
energy delivered by the
of the
than that exerted by the steel
projectiles.
Naturally the Gruson Factory thoroughly noted this relation
in the
construction of the later type of armour, but they could with confidence
submit to the increased severity of the tests
improvements effected
the Factory
went
presence of the great
in
these later types of plates.
in
so far as to
make but
little
As we have
seen,
provision by an increase in
the size of the plates against the nature of the attacking projectiles, and
even considerably reduced them
Empirical Formula for Designing Chilled Armour.
5.
We
in proportion to the attack.
have made frequent reference,
relation of the dimensions
and weight
in
the previous sections, to the
of the chilled armour, both in con-
nection with the question of resisting power, as also as completing our
review of the results of the
It is
in
trials.
obvious that a formula for calculating the design of armour plates
harmony with
this relation will, in
proportion to
its
accuracy, be of
much
utility.
Should a
plate, for instance, for
some reason have
to be
made narrow,
same
would be convenient, but the sole
existing formula proposed by the Gruson Factory only takes notice of the
it
would appear desirable
it
thicker in order to reach the
in other circumstances,
weight than,
maximum
to cast
thickness of the plates.
the formula a
number
The
difficulty consists in
of different factors, without
the particular influence of each
;
bringing into
an exact knowledge of
and, on the other hand, as
we
shall see,
a
formula based on correct data would give results incapable of being used
in practice.
The Gruson
and leaves
it
formula, as
we
say, only refers to the
maximum
thickness,
to the constructor to estimate the other dimensions according
to his judgment.
The formula
to the fourth
gives the
root of
attacking shot, and
the
maximum
number
thickness of the armour in proportion
of
foot-tons
of
the
energy
of
the
applies, in the first instance, to coast defence armour.
135
[
For such armour
this
formula
is
]
:
i
1.
^ 0.29 V foot-tons.
d = 0.27 'y foot-tons.
d
For port plates
4
2.
For side plates
4
3.
For glacis plates with earth
in front
d
.
= 0.22
'y foot -tons.
4
4.
for
For
glacis plates with granite in front
d
^ 0.2
These dimensions are increased ten per cent,
inland fortifications, the formula becoming
-y foot-tons.
in the
case of armour
:
4
1.
d
For port plates
^
0.32
V
foot-tons.
4
2.
For side plates
3.
For
d
=
0.29 -Y foot-tons.
4
glacis plates with earth in front
.
d =^ 0.24 'y foot-tons.
4
4.
For
glacis plates with granite in front d
Before discussing these formulae
it
will
maximum thickness of all the plates
formula. The following Table gives this,
actual
same
as in the Table at the end.
be
=
0.22
V foot-tons.
of interest to
compare the
with the thickness given by the
the reference
number being the
—
136
[
It will
]
be seen that the difference between the actual and calculated
armour thicknesses
difference of 2.9
in trials III. to XI. is
in
in.
very
Trial VI.
slight.
favour of the calculated thickness, and
shows a
trial
XI.
4.1 in. in favour of the thickness actually given.
In the coast defence
earlier battery plates XIII.
armour the differences are greater.
and XIV. the actual thickness
is
two
In the
4.8 in. in excess
of calculation; in the turret plate XVI., 6.3 in., whilst in the Spezia plate,
XVIII., the figures are approximately the same.
On
agree
we may
the whole
fairly well,
say that the actual and calculated thicknesses
and though not
accordance throughout, the
entire
in
dimensions given to the later plates approximately agree with calculation.
The formula was
originally based
iron projectiles,
and armour plates
tion (Fig. 30).
The
latter
chilled shots
on the
results obtained with chilled
of nearly vertical profile in the
were superseded by
lower por-
proved that the dimensions calculated for plates of the above
were proportionately too weak, but as
profile
this
more sloping one, the formula again regained
Spezia plate could be calculated by
its
which
steel projectiles,
profile
was abandoned
for a
correctness, so that the
the formula obtained with chilled
it,
projectiles serving thus for steel shell as well.
The Gruson
formulae, since their first publication in the year 1882,
been repeatedly discussed by the technical press.
examination of them
is
found
in
have
The most comprehensive
the recent essay of Engineer Josef
Schwartz of the Imperial Austrian Marine Artillery, entitled " Ueber die
Panzerwirkung der Geschosse.
Pola, 1886."
Mr. Schwartz, on page 54 of his pamphlet, gives a graphic illustration
armour thicknesses obtained by the formula varying from o to 41.990
foot tons, the foot tons being shown as abscisse and the calculated thickof 14
nesses as ordinates in his diagram.
"The
first
curve
itself
follows a
He
remarks (page 53)
somewhat curious
course, increasing at
very quickly, but soon an increase of 3,230 foot tons energy requires
only a very slight addition of thickness in the armour."
he adds, "that an 11
instance,"
energy
it is
:
is
in.
steel
shell,
with
" Suppose,
12,920
foot
for
tons
an exact match for a chilled plate of 37.6 in maximum thickness,
why a 12 in. steel shell with 19,380 foot tons
impossible to understand
energy should not be more than a match for a plate 41.5 in. in greatest
number of normal hits (angle
thickness " and he concludes later that the
;
of impact 90°) will
be always very small*
in proportion to the total
and
* Mr. Schwartz proceeds on the assumption that the armour is always hit at an angle of 90",
which, however, as Column 9 of our Table shows, is not the case, even with armour of the pld
profile.
137
[
number
equally small
of
hits,
]
from which
may be assumed
it
that the
formula gives good results up to 19.380 foot-tons of energy.
Mr. Schwartz's deductions seem at
we
but
rely,
first
sight convincing in
notwithstanding, on the subsequent Spezia
proof that the formula,
when a
correct profile
is
trial,
all
respects,
which gave
adopted for the plates,
gives accurate results, even for the highest energies (47,481 foot-tons).
To
shot's
we must
explain this apparent contradiction
conclusions of the last section, where
energy took
effect
we saw
refer again to the
that only that portion of the
on the plate which was requisite to break the
Consequently, the greater the energy of the shot becomes,
shot to pieces.
its nominal energy, and
by Mr. Schwartz, has in
consequence probably hardly any noticeable effect on the armour.
the farther does
increase
the
its
effective
energy
6,460 foot-tons,
of
The nature
differ
referred
of the curve, calculated
increases quickly and then
from
to
from the formula, which at
more slowly, seems to us to show
formula though somewhat arbitrarily constructed from
relations
between the dimensions
of
the
plates,
among
first
that this
the numerous
does for the present
correspond very well to the actual conditions, and that no reason has been
shown on the ground
that
of those relations to construct a
on the contrary the simplest and most
new
correct
constructor of the armour to continue as before to calculate
thickness,
and
his experience
formula, but
plan
is
its
for
the
maximum
to determine all the other dimensions in accordance with
and the
results obtained
from the
trials
made
with the
plates.
Should the breadth of the
to
an unusual extent,
it
plate, then, for other reasons,
becomes necessary
be decreased
to restore, as far as possible,
the normal weight by increasing the thickness.
[
138
]
6.— Conclusions.
was natural that the enquiries which we undertook
It
in the previous
sections should be based throughout on a comparison of the earlier
later plates tried,
and
superiority of the
armour over the gun was generally admitted.
and
their results, as after the earlier series of trials the
between the series, the attack had made very great
was necessary to determine whether the armour had
advanced or had been left behind. It was shown by the trials that
In the interval,
progress, and
similarly
it
the form of the older type of plates was not the most favourable, even for
the shot of those days, the thickness having been too
upper edge
was shown
It
and new
in the old
remained within admissible
we
at the
also that the ratio of the superficies to the vertical section
was correct both
In
much reduced
of the plate.
plates,
and
in
the latter always
limits.
comparing the weights
of the
armour with the energy
The
arrived at a very important difference.
earlier
armour was so much more favourable
recent
trials,
in the
armour.
ratio
of the shot,
the case of the
in
to the plate than in the more
shown by the latter to the improved shot
and heavier charges could only be explained by an important improvement
that the endurance
In the concluding trial against armour for inland fortifications,
armour of improved
shown
that
to the
power
of the attack
in the case of the
Tegel
profile, in
which the proportion
of
it
was
weight
was nearly restored to that which was established
plates,
gave entirely analogous
if
not
results as regards resistance than the Tegel plates, so that the
still
better
armour had
entirely kept pace with the notable progress in artillery.
The
trial at
Spezia against a plate of recent and improved profile gave
the same indication as regards coast defence armour, so that
we may
affirm,
without exaggeration, that the superiority of the armour to the attack shown
has been maintained, practically without change, to the
in the earlier trials
present day
trials
—that
;
is
and
this is
proved to be the case both by the results of the
by the behaviour
of the
new
plates under fire
the fact that the thickness of these recent plates
to that given
earlier trials.
—as well
as
by
corresponds almost exactly
by the formula which was obtained from the
results of the
139
[
Of
the
all
recent
]
those carried at Spezia in April and June
trials
naturally have a claim to chief attention.
For a long time previous
in
professional
circles
rounds from the
to the
had been much discussed
trial it
whether an armour plate could withstand three
gun with an energy
lOO-ton
of
which
was
it
natural that
numerous representatives
foot-tons, the
47.481
opinion being generally against such a possibility.
consequence of
In
of foreign
governments
War
availed themselves of the permission granted by the Italian
Office
to attend the trials.
As a matter
of fact,
it
was not the private
Factory which were at stake in
this trial,
interests of the
Gruson
but in great measure the whole
Had
the plate failed, it is more than 'probable that
would have been given up, to which the opinion
of many was already tending, and the proof of the disproportionate
severity of the test of the plate, which we still maintain to have been
armour.
future
of
armour
for coast defence
demonstrated, would hardly have received
of such a result,
A
plate
and have averted
its
due attention
in presence
this conclusion.
correct estimate of the severity of the test applied to the Spezia
is
only obtained by a review of the earlier
the heaviest calibre against
compound and
trials
made with guns
of
steel plates.
made at Spezia with the Armstrong
gun against wrought-iron plates manufactured by
Brown, Cammell, and Marrel, and a forged steel plate by Schneider.
In the year 1876 trials were
l6.g in. muzzle-loading
had a thickness of 21.7
All the plates
in.
Gregorini chilled cast-iron
were used, weighing 2,002 lbs., maximum charge 341. 8 lb., giving a
velocity of 492.7 yards, and an energy of 30,058.4 foot-tons.
The targets
were in all cases perforated by the shot. In trials which took place in
shells
December
of the
same year
the charge
was increased
Fossano powder, but without marked increase
Heavier charges were employed
with the Armstrong 17.7
compound
All
in.
in the trials
muzzle-loader.
The
made
of 1.6
ft.
plates
The compound
1882
in
were two
by Schneider.
8.5
and a breadth
ft.,
Gegenstande des
1883, p. 241).
plates had a facing of steel about 6 in. thick;
Schneider plate was of forged
backing 47.2
in. thick.
of
plate
(For further details see " Mittheilungen fiber
und Geniewesens,"
Spezia
at
plates tried
by Cammell and Brown, and a steel
three plates had a thickness of 10.8 ft., a height of
Artillerie
to 396.9 lbs.
in the velocity.
steel.
All three plates
were
fixed to a
the
wood
—
[
The
140
]
following Table gives the chief data of the trials
:
Experiments against Armour-Plates with the Armstrong
17.7 in. M. L. Gun in the year 1882.
=1
[
The
141
]
following Table gives the principal data
:
Experiments against Armour Plates with the 16.9
Armstrong
Target.
B. L.
Gun,
in
the year 1884.
in.
—
142
[
three rounds, and also withstood
a fourth
hit
]
—apart
from the two
shells
5.9 in.
from the loo-ton gun, striking on the most unfavourable and
most injured spot
at
an angle of
80'^ to 90°, the lateral
support being
at the time entirely insufficient.
A
glance at Fig 45 shows that the plate, even
would have
given
every security
to
the
after
this
round,
gun detachment behind
it,
and the large and almost uninjured part of the upper half of the plate
proved that it was still capable of withstanding further rounds from the
same gun.
The more unfavourable
the anticipations were before the
trial
as to
the endurance of the plate, they only gave additional point to the result
turned out, and the technical journals did not
as
it
as
we
fail
to recognise, as far
have seen them, the striking and exceptional issue of the
trial.
Our own opinion that the terms of the trial were beyond those to
which coast defence armour can ever be called upon to resist, did not affect
this favourable issue.
We
do not mean to affirm that
development, although
limit of its
we
which the
already have reached the
certain the velocity of the 16.9 in.
was only reached by means
shot used at Spezia
charge;
may
artillery
it is
of
an exceptionally heavy
prefer to point more to the short range of
Assuming
148.5 yards, at
was conducted.
firing
that in the future guns are
develop the energy of the Spezia
trial
employed which are able
from a fighting range,
we
ask
:
to
How
many rounds could such a ship's gun place on a single one of the 15 cupola
Any one who had noted how great was the difficulty of laying
?
plates
gun from the pontoon, when the motion was very slight, comes
necessarily to the conclusion that it would be an entire impossibility to
systematically place three rounds on one and the same plate from a heavy
the
gun on board ship
—an
opinion repeatedly expressed by naval officers at
Spezia.
Even supposing
on board
We
ships,
and
being breached
be
fulfilled
that
the
still
more powerful guns are in future mounted
guns will a fleet possess ?
of such
consider the object of coast defence armour to be
guns
the
that
how many
gunners
against
shell
fire,
hits.
This
object
by casual single
by a much
dimensions
slighter
of
the
and
hostile
armour,
plate
to
would,
to
defend
withstand
however,
and we therefore do not think
tried
at
Spezia
will
constitute
a
143
[
measure
for
1
the subsequent armour to be constructed, which opinion
all
does not, however, detract from the high value of the issue of the Spezia
trial.
The small penetration of the shot
maximum 4 in. on the parts not already
portion of
the
their
total
penetration,
the
into
the
armour
chilled
shows how small a
injured)
The deeper
energy was delivered on the plate.
greater
blow on the
the
is
we
diminishing of the effective blow,
(in
and
plate,
in
the
of
the
see the special advantage
system of chilled iron armour over armour of wrought
iron.
Quite apart from cylindrical wrought-iron armour, inclined armour of
the same nature invariably suffers
much
heavy guns, and the blows
injury in partial penetration from
of the striking shot are so
heavy that
the
fire of
we
seriously doubt whether the ports of a turret carrying such
which
effect or give
armour
scope for the revolving movement, could be
made
strong enough to withstand them.
still
The case is more favourable as regards steel and compound armour
we do not believe that in the present condition of manufacture these
last
can have given to them the same hardness as chilled iron armour
without at least
its
having serious influence on their tenacity.
Moreover, with armour of
this
amount
class the smaller
of weight,
which contributes so much to compensate the blows received, always acts
unfavourably in the presence of the heavy projectiles used
It
indeed
may be
possible to
make wrought-iron
in the
attack.
or steel plates of equal
weight to that of the Spezia plates, but for practical purposes such a pro-
We
ceeding would involve too great an expenditure.
are consequently
that the chilled iron armour is in the present day in a
more favourable position as regards the guns for the attack than the other
systems of armour, in which as yet, so far as we know, no attempt has been
made to construct turrets and batteries to protect 15.7 in. guns.
of opinion
Although
accustomed
technical matters,
armour
will
qualities
we do
be disturbed
which
to
radical
and improvements
changes
in
not think that this superiority of chilled iron
in the
distinguish
this
near future, as
system
from
is
it
based upon two
others,
all
namely,
its
hardness and weight.
Whether those who,
like ourselves,
hold the
above opinion
as to
the object of coast-defence armour are right or not, or whether the future
will bring
about a great increase
in
guns, which formed the basis of the
the precision of the
programme
of
fire
from ships'
the firing trials at
[
Spezia, can with as
in
the
future
increase, but
the latter
of the
shot
the
we
case,
little
power
believe
144
certainty be decided as
of
tried at Spezia,
will
receive
weapons
a great
with confidence that, even
be necessary
in the
in
dimensions
Should we, however, be also
this respect, the superiority of the chilled cast-iron
relation to the
difficulty,
question whether
inasmuch as the whole energy, of a
never takes effect on the armour.
mistaken in
tlie
the attacking guns will
we may assume
no important increase
armour plate
]
of attack could hardly
be
affected, as
armour
no technical
as we have shown above, exists to increasing the strength
chilled iron plates.
FINIS.
in
of the
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Armour
for Coast Defence.
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for Inland Fortification
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