ver firing
Year: 1886

page_text: § 1-Definition. What is called "Converging firing at sea
" is a mode of firing
allowing the effective employment of volleys of artillery in naval engagements.
The problem for attaining this result may be expressed as follows:
To incline and set several pieces of ordnance situated on the same ship in such
a way that the trajectories of their projectiles shall have as mark, at a given
moment, a common predetermined point.
To resolve this problem, we will study separately the two constituent elements :
1stly the convergence in range; 2ndly the convergence in direction.
Whilst considering each of these elements we shall always suppose that the one
not in question has been solved.
§ 2-Convergence in range-The range is a determined function of the angle of
firing of the gun, the problem of convergence in range therefore resolves itself in
giving to a piece of ordnance situated on board a ship, subject to the motion of the
sea, a determined angle of firing at a given moment. This angle of firing is the
angle made by the axis of the gun with the horizontal plane, and should be equal
to the angle of firing given by the tables, for a range equal to the distance
between the gun and the mark, corrected in accordance with the angle of elevation
of the mark.
On board a ship, it is impossible to measure the angle made by the axis of a
gun with a horizontal plane; this axis participates in all the movements of the
ship, and the angle it makes with a horizontal plane varies at every moment.
There is but one way of obtaining at a certain moment the angle of firing
required: this consists in setting the sight for the distance and in aiming: when
the line of sight prolonged passes by the mark, the axis of the gun forms, with
the horizontal plane, an angle equal to the angle of firing corrected in accordance
with the angle of elevation of the mark,

page_text: Let us take on board a ship a plane of reference that will be invariably connected
thereto and let us call for a given gun a the angle of firing given by the tables for
a range equal to the distance between this gun and the mark, w the angle of the
axis of the gun with the plane of reference.
the angle of the plane of reference with the horizontal plane at the moment
the gun is pointed in elevation.
the angle of elevation of the mark: we shall have between these various
whence:
a t = w + B
β
-
Q = α-a).
-
The second member of this equation is known, and the value of ẞ – ø is drawn
therefrom.
-
Now is constant for all pieces of ordnance having parallel planes of firing
to each other.
If we consider a second gun whose angle of firing has a value a¹ for a range
equal to the distance from the mark and if it is made to form with the plane of
reference such an angle w' that :
it will be seen that we have:
w¹ = a¹
-
(B
-
Ø)
a² + 0 = w¹ +.B.
This second gun will be pointed in elevation at the same time as the first, and
the same for all the other guns of the ship.
-
The pieces of ordnance situated on board a ship are not all at the same distanco
above the level of the sea; in order that the value of the angle of elevation of
the mark may be about the same, the tables of firing are made up by calculating
the angles of firing for ranges at the level of the sea."
§ 3-Convergence in direction. The plane for firing guns aimed by the sight is
determined according to the method adopted for obtaining convergence in range.
Let us consider a second gun pointed on the same mark; say P, fig. 1 the distance
to the mark, of the gun pointed in elevation.
:
d the distance of the axis of the pivots of the two guns.
:
a the angle made by the directing plane with a plane perpendicular to the
straight line which joins the axes of the pivots of the two guns.
the angle of the planes of firing of the two guns or angle of correction of the
firing in direction, it will be seen on the figure that:
d cos. a
tgpd sin., a²
The value of the angles of corrections for all the angles and all the ranges, can
therefore be calculated and a double entry table can be made, but the number of
columns would be considerable and the reading of the table difficult.
If be the radius of the circumference on which are measured the angles of
setting of the plane of firing, if BC be led parallel to the straight line which
joins the axes of the pivots, similar triangles will give us :
Px = ld
whence it results that the value of x is only a function of the range. The figure A
BCD is therefore a jointed parallelogram that changes its shape in turning round
the points A and D. The side A B being parallel to the directing plane, the
diagonal line AC is the direction of the second gun for its firing to be converging.
The side B C is inversely proportional to the range.
A mechanical solution of the problem might easily be drawn therefrom, but
the installation of these jointed parallelograms in ships batteries would be
encumbering.
Resuming the equation
:

page_text: 1-Directing apparatus--fig. 3 is a side elevation thereof and fig. 4 a rear
elevation; fig. 5a view of the foresight for night firing. The method resulting
from the preceding considerations consists in pointing or aiming a gun by elevation
and deducting from the position of this gun the positions. of all the guns that are
to take part in the converging firing.
Although possible, the direction of the firing by the aid of a single gun would
not be very practical; it should therefore be reserved for certain special cases:
generally speaking the aim of directing pointing should be made by means of a
special apparatus more handy and whose situation can be chosen on each ship:
this is the directing apparatus.
This
It is composed essentially of a line of sight a provided with the necessary
devices for effecting the pointing in elevation and in direction, that is to say a
device for giving the angle of firing and a deflection slide b, figs. 3 and 4.
metal sight is connected to an axis C on which is also secured a toothed segment &
whose movement of rotation is controlled by an endless screw e moved by the hand
with crank f. Such is the device adopted in figures 3 and 4; it is obvious that
any other transmission can be applied to the production of the movement of
rotation of the line of metal a around its axis c.
The toothed sector & thus set in motion, gears with a pinion g whose radius is
a determined fraction of that of the toothed segment: this device has for object
to multiply the movement of rotation of the pinion g so as to allow of measuring
small fractions of the angle of rotation of the line of sight a.
On the same axis has the pinion g is secured a drum i on which is drawn a
graduation in ranges at the sea level in function of the angles of firing given to
the line of sight; these latter are also indicated at the line of sight by the
appertaining ranges.
This apparatus is carried by a frame j movable on a pivot. In the sent of the
axis h, of the pinion g and of the drum i, a spring k, shown in dotted lines in
fig. 3, secured to the axis h and to the frame j suppresses all play in the transmis-
sions. This frame also supports a segment i, fig. 4, divided in degrees and sub-
divisions from 0 to 10°. The subdivisions correspond to a rotation of the line of

page_text: sight a of 2' so as only to cause an error of less than one minute. The position of
this segment is regulated in such a very way that when the axis of the pivot
of the frame j is vertical and the mark aimed at the level of the sea, if the elevation
of the distance is given and the pointing made, the graduation of this same range
on the drum i will be opposite the division. 5° of the graduated segment.
The frame; and the apparatus can turn around a pivot carried by the stand m
of the apparatus, so as to permit of being directed in any position. This: movement
of rotation is obtained by the aid of any mechanical transmission such as an endless
screw n controlling a toothed wheel o, or better still, gearing with a stationary
toothed wheel, so as to move on the circumference. In this way, the crank p of
the mechanism always preserves the same position relatively to the man who lays
the gun. The stand m of the apparatus bears a graduation in degrees or in scales
and the frame an index permitting the fixture of the line of sight at the chosen
or determined setting of the plane of firing.
The series of operations to perform with the directing apparatus in order to
prepare a converging firing will be:
Firstly to give the elevation of the distance of the mark. Secondly to determine
the setting of the plane of firing. Thirdly to communicate these data to the guns.
Fourthly to lay or point the guns on the mark. Fifthly to read the sum of the
angles of keel of the ship, and of elevation of the mark. Sixthly to communicate
the result of this reading to the guns. Seventhly to bring the line of sight to the
setting of the plane of firing.
To allow of night firing a lighted line of sight, fig. 5 may be substituted to the
line of sight used in the day time.
$2 Apparatus for convergence in range-fig. 6 is a side elevation thereof, and
fig. 7 a rear elevation. Each piece of ordnance receives an apparatus which allows
of measuring the angle of its axis with the plane of reference. To this end,
a toothed sector A is secured on the face of the trunnion A¹ or a toothed segment
on the reinforce of the gun. The center of this sector or of the segment must
coincide with the axis of the trunnion of the gun.
The sector or the segment A gears with a pinion B whose radius is a fraction of
that of the segment or of the sector, so as to multiply the angles of rotation of the
gun to allow of estimating small fractions thereof.
The pinion B is fixed on a sleeve Bt movable around an axis Bª carried by the
cheek of the carriage. On this sleeve is secured a drum C. A spring taking its
bearing on the axis as well as on the sleeve, and placed so as to bend in all positions
of firing of the gun, prevents all play in the transmissions.
The drum receives the graduations in ranges at the sea level in function of the
angles of firing, and in the position of the ship wherein the plane of reference and
the ship lie along neither on one side nor on the other of the keel.
These graduations are equal in number to the charges and projectiles fired by
the gun.
An arm D movable around the axis B² or a movable slide on its surface can be
fixed on the desired point of the drum. The arm D or the slide bears a certain
number of indexes EEE corresponding to the various graduations of the drum,
plus an index, the use of which is hereafter given. Each of these indexes bears
a mark of reference.
On the carriage is fixed a segment F whose curvature is equal to that of the
drum, and divided in degrees and subdivisions of the degree from 0 to 10°. The
subdivisions correspond to the segment of 2' of rotation of the gun, so as only to
cause, in the measure of the angle of firing, an error of less than 1 minute.
The position of this graduated segment F is regulated in such a way that when
the axis of the gun nakes with the plane of reference an angle equal to the angle
of firing calculated for a certain range at the sea level, the division which repre-
sents on the drum this range for the charge or the projectile used being set opposite.
the index appertaining thereto, the reference mark of the arm or of the slide will
be exactly in front of the division 5° of the graduated segment.

page_text: When the directing apparatus, figs. 3 and 4, communicates the range and the
setting of the plane of firing, the following operations are effected with the gun :
Firstly reading on the racer the difference of distance between the gun and
directing apparatus and the mark; concluding therefrom the distance of firing of
the gun.
Secondly bringing the mark indicating on the proper graduation of the drum C,
opposite the graduated segment F.
Thirdly fixing the arm or the slide D in the proper position on the drum C.
Fourthly when the directing apparatus communicates the reading made on the
graduated segment F, bringing the index E of the arm D in front of the same
division of the graduated segment F.
The converging firing range is then prepared.
§3-Convergence in direction-fig. 8 is a rear elevation of the apparatus, fig. 9
a plan-fig. 10 a section through a, a¹, fig. 8. Fig. 11 a section through b, b¹, fig. 8,
and fig. 12 a section through j, ¹, fig. 9.
The preparation of the converging firing in direction includes two perfectly
distinct operations:
Firstly Measuring the angle of correction of the firing in direction.
Secondly Introducing this angle of correction into the preparation of the laying
of the gun.
The first operation is effected by means of an index table established for the field
of firing of the gun according to the method above described.
In order to simplify the preparation of the said table, the equilateral hyperbola
will be replaced in their useful parts by one of their chords or by an inscribed
or circumscribed polygon. The error that results from this modification can be
absolutely neglected when the chord or the polygon is properly chosen.
When the directing apparatus, figs. 3 and 4, shall communicate the distance of
firing and the setting of the plane of firing, the operator will only have to go back
on the index table to the point of intersection of the lines figuring these two data
and will read thereon directly the value of the angle of correction of the firing in
direction and the meaning of this correction.
In order to introduce this angle of correction into the preparation of the pointing,
the carriage of each gun carries an apparatus for pointing in direction, figs. 8 to 12.
At the rear of the frame, on one of the cheeks or on both is fixed a curved
rule A, figs. 8 to 12, whose center is on the axis of the pivot of the gun.
Two collars C C placed on this rule support two rules E E in the interval of
which moves a vernier or sliding gauge G. On each of these rules is a graduation
in segments of 10' and the vernier is at 6. There will therefore always be caused
an error of less than half a minute.
The graduation of each rule is made for one of the directions of correction of the
firing according as the gun is on the right or on the left of the plane of firing of
the directing apparatus. The necessary indications to avoid all confusion are made
on the index table and on the rules.
A set screw allows of fixing the vernier G in the proper position.
To the vernier G is secured an index H on which is a reference mark.
Opposite this index, is fixed, on the deck, a racer K graduated in degrees and
whose center is at the axis of the pivot. The graduations correspond exactly to
those of the graduation of setting of the plane of firing at the directing apparatus,
figs. 3 and 4.
The index H is movable to allow of its being taken off or displaced so as to be
safe from shocks in ordinary times.
There will only be made on the vernier G the correction of the fraction of degree
of the angle of correction of the firing in direction, the entire degrees will be
corrected directly on the racer K by carrying the index H to another division than
the one given by the directing apparatus, and properly chosen by remembering
that the correction should always be made so as to turn aside the rear part of the
plane of firing of the directing apparatus, figs. 3 and 4.

page_text: When the directing apparatus, figs. 3 and 4 gives the setting of its plane of
firing, the apparatus of pointing in direction of the carriage is worked in such a
manner as to bring the gun almost in the proper position that is to say in such a
manner that the index H shall be near the division indicated. During this operation,
the index table is consulted, and the magnitude and side of the correction are, read.
The vernier G is displaced in proper manner and fixed in this position. The
apparatus for the pointing in direction of the carriage is worked anew until the
reference mark of the index H be exactly opposite the proper division of the racer.
The setting is such that when the vernier G is at the 0°, the indicators of the
directing apparatus and of the apparatus of convergence in direction opposite the
same divisions of their respectivo racers, the planes of firing of the directing
apparatus and of the gun are parallel..
The racer K fixed on the deck is also used to indicate the differences of distances
between the guns and directing apparatus and the mark. Opposite the corre-
sponding settings, these differences from metres to 5 metres are indicated on.
shoulders secured to the racer and the sign + or
to or deducted from the distance given.
-
- indicates if they must be added
The operator should always take the number of decametres (10 metres) the
nearest to the setting given, so as to commit an error of less than 5 metres on the
distance between each gun and the mark,
For guns mounted in barbett turrets and in armored cupolas, the racers K will
be replaced by cylindrical surfaces secured to the stationary part of the turret or
of the cupola and the vernier and the whole apparatus of convergence in direction
are carried by the rotating part.
§4. Leeway The leeway can be generally corrected on the directing apparatus
by adopting for its value the arithmetical mean of the drifts of the various guns of
the ship on condition that these various drifts shall be in the same direction. The
error that will result therefrom will not be of great importance.
If the guns are not all rifled in the same direction or if it is desired not to
commit this error, the operator must be able to give each gun its leeway.
To this end, he can operate in various ways, for instance by inscribing on the
index table the value of the angle of leeway of each range which he would add to
or deduct from, as the case might be, the angle of correction of the firing in
direction.
He can also by means of any appropriate mechanism, displace sufficiently and
in the proper direction, either the index H in relation to the vernier G, or the
apparatus of convergence in range, figs. 8 and 9 in relation to the rule that carries
it, or this latter in relation to the carriage..
These figures represent a very precise arrangement which has for its object
to displace the apparatus of convergence in range in relation to the rule that
carries it.
On the curved rule A figs. 8 to 12, secured to the rear of the carriage, and which
carries the apparatus of pointing in direction,. the operator will displace the
collars CC which carry this apparatus of a quantity equal to the leeway for a
length of line of sight equal to the radius of this rule A. To this end, one of the
collars carries a projection T on which acts a segment of an involute of a circle
properly chosen. This segment is carried by a plate D that can be rotated by
hand and which is fixed in the proper position by means of a set screw M.
A graduation in ranges drawn ou this plate is displaced in front of an index i
carried by the rule A. A distance being given by the directing apparatus, the
plate D will be turned until the mark of the distance be opposite the reference
mark. The whole apparatus of pointing in direction is then displaced in the
proper direction, a quantity corresponding to the leeway corresponding to the
range indicated.
§ 5. Corrections of the movement of the mark and of the effects of the wind.
The corrections of the movement of the mark and of tho effects of the wind are
made on the directing apparatus.

page_text: The corrections of the normal components to the plane of firing are made by
displacing the connection part, the required number of divisions in the proper
direction on the deflection slide. A division of this rule corrects a knot of speed
of the mark, normal at the plane of firing, or 1 metra at 1.000 metres.
The corrections of the components situated in the plane of firing are made on
the length of the line of sight by taking as basis the principle sufficiently exact in
pretty confined limits that, for a same elevation, the range is inversely proportional
to the length of the line of sight. To this end, the foresight is movable. One
division of the graduation on which it is displaced corrects 1 knot of speed of the
mark in the plane of firing, that is to say 1 metre at 1.000 metres.
When, at the moment of firing, the officer notices that he has committed an
error on the distance of the mark, he will turn his line of sight of an angle equal
and contrary to that which gives this difference of range without modifying the
elevation nor changing anything in the position of the guns. In this way, when
through the movements of the ship, the line of sight will pass by the mark, the
angle of firing of all the guns will be corrected very approximately, provided
however that the elevation of the directing apparatus be the mean of the elevations
of the cannons on this side and that the difference of range to correct be not too
Other Applications.
§ 1. Pointing of cannons in armour clad cupolas. The ports by which are fired
pieces of ordnance in armour clad cupolas are of too small dimensions to allow of
convenient practice of pointing. The directing apparatus, figs. 3 and 4, can be used
for this operation. To this end, it should be fixed on the outer part of the turret,
in such a way that the box being fixed at the zero of the deflection slide, the line
of sight shall be in a vertical plane parallel to the axis of the gun. The sight of
the directing apparatus will be that of the gun, the derive will be given to the
directing apparatus either by hand or automatically. The arrangement relating
to the pointing in direction will be suppressed.
§ 2. Employment of volleys in the firing of coast batteries on movable mark.
The method which has just been described can allow the firing in volley of coast
batteries on movable mark. We will only have to suppress all that concerns the
pointing in elevation which will be done at each gun by means of a spirit level
graduated in ranges at the sea level and in angles.
The racers placed on the platforms will bear for each setting the differences of
distance between the gun and directing apparatus and the mark.
This apparatus will be replaced by a simple graphometer which be may be one
of the telemetric stations.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that
what I claim is :-
:-
First. The directing apparatus, figs. 3 and 4, having for objects to give the lino
of sight pointed on the mark to strike, and to measure the algebraical sum of
the angles of keel and of elevation of the mark, which apparatus is composed -
essentially firstly of a line of sight a consisting in a fore sight and a notched
sight, the latter carried by a sliding sight and being used to lay or point the gun;
secondly of a drum i bearing the graduations in distances, receiving the movements
of rotation of the pointing apparatus multiplied by a certain coefficient. This
drum is displaced opposite a divided segment & fixed to the frame in a position
determined by the ruling. It is used to read the algebraical sum of the angles of
careening or keeling and of elevation of the mark.
Secondly. The apparatus of convergence in range figs. 6 and 7, having for object
to give each gun such an inclination that the simultaneous firing of all the guns
shall be converging and composed essentially of a drum C receiving the graduations

page_text: in ranges of the various modes of firing of the gun. This drum receives the move-
ments of rotation of the gun, multiplied by a certain coefficient. It is displaced
opposite a divided segment F allowing the introduction into the angle of firing, of
the correction of the angles of careening and elevation of the mark, the extent of
which corrections has been measured on the directing apparatus, figs. 3 and 4.
Thirdly. The apparatus of convergence in direction, figs. 8, 9, 10, 11 and 12,
having for object to give to each gun the proper setting for the simultaneous firing
of all the guns to be converging, and which is composed: firstly of an index table
giving the value of the angles of correction of the firing in direction in function of
the distance from the mark and of the setting of the plane of firing of the directing
apparatus, figs. 3 and 4; secondly of the apparatus of convergence in range, figs. 6
and 7, which has for object the introduction of this correction into the laying or
pointing of the gun, and which is composed of a racer graduated in degrees placed
at the rear of the carriage and of a curvilinear vernier carried by the frame of the
carriage. This vernier carries an index opposite the divisions of the circular, the
whole substantially as herein set forth.