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Title: Manual for submarine mining
Author: U.S. War Department
Release date: May 26, 2024 [eBook #73701]
Language: English
Original publication: Washington: Government Printing Office, 1912
Credits: deaurider and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK MANUAL FOR SUBMARINE MINING ***
Transcriber’s Notes:
Underscores “_” before and after a word or phrase indicate _italics_
in the original text.
Equal signs “=” before and after a word or phrase indicate =bold=
in the original text.
Small capitals have been converted to SOLID capitals.
Illustrations have been moved so they do not break up paragraphs.
Old or antiquated spellings have been preserved.
Typographical and punctuation errors have been silently corrected.
The text has numerous references to “figure 18”, the schematic diagram
for the “Operating Board”, however this figure appears to be not
available.
MANUAL FOR
SUBMARINE MINING
[Illustration]
EDITION OF 1912
[Illustration]
WASHINGTON
GOVERNMENT PRINTING OFFICE
1912
WAR DEPARTMENT,
Document No. 399.
_Office of the Chief of Staff._
This Manual for Submarine Mining, revised to 1912, is
approved and published for the confidential information
and guidance of the Army of the United States. Under no
circumstances shall its contents be divulged to persons not
in the military or naval service of the United States.
By order of the Secretary of War:
WM. H. CARTER,
_Major General, Acting Chief of Staff_.
CONTENTS.
Page.
CHAPTER I. Definitions and general principles 7
II. Matériel of the system 11
III. Loading room duties 34
IV. Locating distribution box, laying multiple cable,
marking out mine field 42
V. Assembling and planting mines 48
VI. Test of mines and apparatus 56
VII. Taking up mines 62
VIII. The mine command 65
APPENDIXES.
1. Explosives 69
2. Oil engine and generator 77
3. Storage battery 84
4. Submarine mine cable 92
5. Care and preservation of matériel 107
6. Instructions for masters of mine planters 111
7. Manual for small boats 115
8. Supply list 121
CHAPTER I.
DEFINITIONS AND GENERAL PRINCIPLES.
A submarine mine consists of an explosive charge inclosed in a
water-tight case, and a firing device, the whole intended to be
submerged in a waterway which it is desired to close against the
passage of an enemy’s vessels.
With respect to the position of the case containing the explosive,
submarine mines are of two classes, buoyant and ground.
In the buoyant mine, the case contains the explosive and the firing
device, and has such excess of buoyancy that it would float were it not
held below the surface by a mooring rope and an anchor. The submergence
is such that, while the mine would be struck by the hull of a passing
vessel, it is not so near the surface as to be seen.
Buoyant mines may be planted and operated successfully in water 150
feet deep. They should not, in general, be used where the depth of
water is less than 20 feet.
In the ground mine, the case contains the explosive and the firing
device, and is heavier than the displaced water; it therefore rests
upon the bottom and requires no anchor. Ground mines are not used where
the depth of water exceeds 35 feet.
With respect to the means used to fire them, mines may be classed as
mechanical and electrical.
Electrical mines are, in turn, of two general classes, controllable—in
which the firing device is under control after the mine has been fixed
in position; and noncontrollable—in which no such control is had.
Mechanical and noncontrollable electrical mines are intended to be
fired only by the blow of a passing vessel. When once in position
they are dangerous alike to friend and foe, while controllable mines
may instantly be made safe for friendly vessels or as quickly made
dangerous to vessels of the enemy.
Controllable electrical mines are arranged so as to give a signal
to the operator when they are struck. They may be set to fire
automatically when struck or tampered with, or may be fired at the will
of the operator. In the latter case the firing may be delayed, in which
case the operator fires the mine some short interval after the signal
indicates that it has been struck; or by observation, in which case he
fires it after the position-finding system shows that the vessel has
come within the mine’s destructive radius.
LOCATION OF MINES.
The considerations involved in the location of mines are of two general
classes, tactical and local.
Tactical considerations deal with the position of mines with reference
to the other defenses. Local considerations deal with the width and
depth of the channel, the swiftness of the current, the variation of
the tide, and the relative importance of the harbor.
Where ordinary ship channels are unobstructed it is possible for modern
battleships, with their high speed and heavy armor, to run by shore
batteries, at least in the night or during a fog; hence the defense of
such channels should not be left to guns alone.
On the other hand, where mines are unprotected by the fire of shore
batteries it is possible for an enemy to remove or disable them.
Therefore guns and mines, the two elements of the fixed defenses of a
harbor, are mutually dependent, and when the location of one has been
decided upon that of the other must conform thereto.
Within the zone between 4,000 and 8,000 yards of the main defense the
fire of heavy guns is destructive for warships, yet the latter are at
such a distance that their rapid-fire guns will be of little effect
against the batteries.
Moreover, at 4,000 yards vessels are just beyond the inner limit of
mortar fire.
If possible, therefore, hostile vessels should be held in this zone by
some obstacle. Such obstacle is afforded by a mine field.
On the other hand, attacks upon a mine field are most liable to be made
by small boats at night. If the mine field be at too great a distance
from the defenses, these boats will not be revealed by the mine
searchlights. Furthermore, for protection against such attacks, the
defense relies upon rapid-fire guns of relatively limited range.
Due to the above considerations the outermost mines are usually placed
between 3,000 and 4,500 yards from the main defense.
In general, there should be in each main channel at least three lines
of mines.
ELEMENTS OF A MINE SYSTEM.
The elements of a mine system are:
1. =The mining casemate=, consisting typically of four rooms: (1) The
operating room, containing the power panel and the operating boards;
(2) the engine room, containing the engine and the generator; (3) the
battery room, containing the storage battery; and (4) the sleeping room
for the personnel.
2. =The multiple cables=, 7 and 19 conductor, leading from the casemate
out to the distribution boxes, one of which is in the center and rear
of each group of mines.
3. =The single-conductor cables=, radiating to the front from the
distribution boxes, one leading to each mine.
4. =The mines=, in groups of 19 or less, extending across the waterway
to be defended, planted approximately 100 feet apart and anchored so
as to have a submergence of about 10 feet at low water. The groups are
numbered 1, 2, 3, etc., from left to right of the observer stationed in
rear of the line, and the mines in each group are numbered similarly,
No. 1 being on the left, No. 10 in the center, and No. 19 on the right.
The groups composing a line of buoyant mines are not usually planted
in prolongation of each other, but with a space for the passage of
friendly vessels, and also for the movement of the planter when at
work upon adjacent groups. Groups of ground mines may be placed in
prolongation of each other or between the groups of buoyant mines, as
they will always be below the hulls of passing vessels.
5. =The mine planters= and other boats with the necessary equipment for
planting and maintaining the planted mines.
6. =The range-finding system=, the same as or similar to that used for
the guns, enabling accurate plotting of the positions of the individual
mines, and consequently permitting vessel tracking and observation
firing.
7. =The searchlights=, for illuminating the mine fields at night.
8. =The rapid-fire guns=, for the protection of the mine fields.
CHAPTER II.
MATÉRIEL OF THE SYSTEM.
=The generating set.=—This consists of a D. C., shunt-wound generator
driven by a kerosene oil engine, or of a direct-connected gasoline set.
(For method of operation of a Hornsby-Akroyd oil engine, see Appendix
2.)
=The storage battery.=—This is a 40-cell chloride accumulator, with
a normal charge and discharge rate of 5 amperes. The voltage may be
taken at 2 volts per cell; the internal resistance is negligible.
Directions for setting up, care, and usage of the storage battery are
given in Appendix 3. The 5-ampere battery is the standard equipment at
the present time, but the new installations will have batteries with a
normal charge and discharge rate of 15 amperes.
=The motor-generator, D. C.-A. C.=—This is a D. C.-A. C. (60-cycle,
single phase) machine, running on D. C. voltage (80-110) and designed
to give one-half kilowatt at 80 volts. To insure against breakdown two
of these motor-generators are supplied to each casemate.
=Starting switch.=—This is a 4-point lever switch and is used to start
the motor-generator and to accelerate it to full speed. To insure
against breakdown two of these motor-generators circuit to the fourth
point. Resistances are connected between the points, as shown in figure
1. The contact made at point 1 is not broken as the lever is moved to
its successive positions. It is seen that the total resistance is 8
ohms; it is all in the armature circuit when the switch blade is in the
first point; 4 ohms when in the second point; 2 ohms when in the third
point; none when in the fourth point. The operation of closing the
lever short circuits in turn the resistances 4, 2, and 2.
=The casemate transformer.=—This is a step-up transformer, of the
oil-insulated core type, and is rated at 60 cycles, 500 watts, 80 volts
primary and 500 volts secondary, when carrying full load.
[Illustration: FIG. 1.—Starting switch.]
=The power panel.=—This panel is shown in figure 2, its wiring diagram
in figure 18 at the end of the book. It consists of an enameled slate
panel upon which the apparatus is mounted. It is 32 inches wide, 69
inches high, and is set up with its face 34 inches from the wall in
rear.
[Illustration: FIG. 2.—POWER PANEL.]
Across the top are two lamps, a double circuit breaker, a D. P. D. T.
switch, and a single circuit breaker. Below these there are an ammeter,
an A. C. voltmeter, and a D. C. voltmeter. Below the ammeter is a
battery rheostat and below the D. C. voltmeter a field rheostat. On a
bracket at the side there is a mil-ammeter, with a 16 c. p., 110-volt
lamp in series with it.
The remaining switches, receptacles, and attachments are sufficiently
well indicated in the figures.
Switch No. 1 controls the lamps at the top of the board. When it is up,
they are supplied from an external source of power. When it is down,
they are supplied from the storage battery.
The D. C. terminals are all carried to one terminal bar, the A. C.
terminals to another. All terminals and all switches are labeled.
Provision is made for energizing the D. C. busses:
(_a_) From an external source of power: Close single circuit breaker
and close switch No. 2 to the right—facing the board.
(_b_) From the casemate generator: Close single circuit breaker and
close switch No. 2 to the left—facing the board.
(_c_) From the storage battery: With switch No. 2 open, close double
circuit breaker.
Feeder switches are plainly marked. The D. C. switches supply power as
follows:
No. 3. When up, supplies the operating boards (negative pole to boards,
positive to earth); when down, it is spare.
No. 4. When up, supplies motor-generator No. 1; when down,
motor-generator No. 2.
No. 5. When up, supplies the mine commander’s station.
No. 6. When up, supplies casemate lamps; when down, it does the same,
but the power is now drawn from an external source and not from the D.
C. busses.
No. 7. When up, grounds the positive bus and connects the negative bus
through the protective lamp and mil-ammeter to the mil-ammeter lead.
The A. C. switches supply power as follows:
No. 8. When up, supplies the operating boards, one pole to boards, the
other to earth through an independent lead; when down, it does the
same, but the side grounded is grounded through a choke coil.
No. 9. When up, energizes the A. C. busses from motor-generator No. 1;
when down, the A. C. busses from motor-generator No. 2.
No. 10 is spare.
No. 11. When up, supplies power to the primary of the testing
transformer; when down, it is spare.
No. 12. When up, supplies power from the secondary of the testing
transformer to the test fuses.
Voltmeter receptacles and plugs, all of which are properly marked, are
provided for obtaining the reading of the A. C. and D. C. voltages. The
D. C. receptacles are on the right and the A. C. on the left. The first
receptacle of each set is spare to hold the plugs when the latter are
not in use.
With the D. C. plug:
In the second receptacle, the voltage of the casemate generator is
indicated.
In the third receptacle, voltage of external D. C. power.
In the fourth receptacle, voltage of storage battery.
With the A. C. plug:
In the second receptacle, voltage of A. C. power on the busses is
indicated.
In the third receptacle, voltage of external A. C. power, if the latter
is supplied.
In general, no external A. C. power should be led into the casemate, as
the system would be unsafe, owing to the liability of a “cross.” The
standard system is perfectly safe, as it is impossible for a mine to be
fired when the motor-generators are idle.
The double circuit breaker is an ordinary single-coil breaker. The
single circuit breaker is an overload and reverse-current circuit
breaker. The reverse-current coil has two windings, one of which is
bridged across the power supply, and the other is in series with it. On
charge, the effect of these coils is differential, and on discharge it
is cumulative and will trip the circuit breaker when the current from
the storage battery exceeds 2 amperes.
[Illustration: FIG. 3.—OPERATING BOARD.]
To charge the storage battery:
(_a_) From an external source of power: Both the single
and the double circuit breakers are closed and switch No. 2
is closed to the right (facing the board).
(_b_) From the casemate generator: Both circuit
breakers are closed and switch No. 2 is closed to the left
(facing the board).
=The operating board.=—A front view of this is given in figure 3, its
wiring diagram in figure 18 at the end of the book. One is required
for each group of 19 mines. It consists of an iron frame to which are
attached a signal block, a master block, 19 mine blocks (1 for each
mine), busses, and a terminal bar with 19 numbered terminals. The frame
is 78 inches high by 24 inches wide. It should be set up so that its
face is 34 inches from the wall in rear.
=The signal block= (see fig. 18).—This is an enameled slate block 24
inches wide and 11 inches high, upon which are mounted three binding
posts, three lamps (red, white, and green), a bell and bell switch, a
90-ohm non-inductive resistance in parallel with the white lamp, and
a 125-ohm resistance in series with the bell. The binding posts are
marked “Earth” or “G.,” “A. C.,” and “D. C.,” respectively. The bell,
the 90-ohm non-inductive resistance, and the 125-ohm resistance are so
indicated on the figure. The lamps are marked as follows: Red, “R. L.”;
white, “W. L.”; green, “G. L.”
The circuit, under normal conditions, is: From negative D. C. bus on
power panel, to switch 3 closed up, to “operating board” terminal, to
D. C. lead, to D. C. post on signal block, through green lamp, to D.
C. jaw on master block, to D. C. bus on operating board, through power
switch P on mine block, through solenoid S, to middle of testing switch
T, to upper contact of same, to upper contact of automatic switch A, to
middle of same, to mine switch M, through same to terminal bar, through
19-conductor and single-conductor cables, through mine transformer
primary, to mine case, to ground, to D. C. “earth” terminal on power
panel, to switch 3, and to positive D. C. bus on power panel.
Green lamps of 8, 16, and 32 candlepower are supplied. The
16-candlepower green lamp glows dimly when 19 mines are connected to
the operating board and all are free from short circuits, grounds,
or abnormal resistances. If it should glow abnormally bright, due to
grounds, a 32-candlepower lamp should be substituted. If it should glow
very dimly, due to a less number of mines connected, an 8-candlepower
lamp should be used.
A short circuit in a mine circuit causes the green lamp to glow more
brightly.
Breaks in conductors not causing short circuits will not be revealed
ordinarily by this lamp. To detect breaks, tests of individual mines
must be made.
The red lamp glows and the bell rings when any automatic switch is
down. The circuit under this condition is:
From negative D. C. bus on power panel to switch 3 closed up, to
“operating board” terminal, to D. C. lead, to D. C. post on signal
block, through green lamp to D. C. jaw, to D. C. operating board bus,
through power switch on mine block whose automatic switch is down,
through insulated pin of lower arm of automatic switch, to lower point
of testing switch T, to operating board lamp bus, through bell, 125-ohm
resistance and bell switch, and red lamp in parallel, to “earth” post,
to earth lead, to D. C. “earth” terminal on power panel, to switch 3,
and to positive D. C. bus on power panel.
The resistance of the bell is such that a resistance of 125 ohms must
be placed in series with it to make the joint resistance of the red
lamp-bell circuit so large that if one automatic switch is down it will
not interfere with the tripping of another.
The white lamp, W. L., is in the firing and A. C. testing circuits. The
90-ohm resistance is in parallel with this lamp, and in addition to
protecting it from excessive current, serves to keep the firing circuit
complete should the lamp burn out.
=The master block= (see fig. 18).—This is an enameled slate block 6
inches wide by 9½ inches high, upon which are mounted two jaws for the
terminals of a jumper, a testing switch, T. S., and a firing switch, F.
S.
[Illustration: FIG. 4.—MINE BLOCK.]
The testing switch, T. S., is used to determine if the A. C. power be
on the signal block. If so, when it is closed the white lamp on signal
block glows. This switch is marked to indicate its “off” and “on”
positions. When “on” the circuit is as given in “test of the delivery
of the A. C. power to the operating board,” Chapter VI.
The firing switch, F. S., is used to throw the A. C. power on the
operating board A. C. busses. This is marked to show its “on” and “off”
positions. No mine can be fired unless this switch is in its “on”
position. When “on” the firing circuit is as follows:
From A. C. bus on power panel to switch 8 closed up, to “operating
board” terminal, to A. C. lead, to A. C. post on signal block, to
white lamp and resistance in parallel, to A. C. jaw, through firing
switch, F. S., to A. C. bus on operating board, to lower point of
automatic switch when it is closed down, to middle point of automatic
switch, through mine switch to terminal bar, through 19-conductor and
single-conductor cables, through mine transformer primary, to mine
case, to ground, to A. C. “earth” terminal on power panel, to switch 8,
and to other A. C. bus on power panel. The white lamp glows after the
mine has been fired.
=The mine block= (see figs. 4 and 18).—This consists of an enameled
slate block, 6 inches wide and 9½ inches high, on which are mounted
four switches.
1. The upper switch is the “mine switch.” When it is open the
corresponding mine is cut out and can not be fired. It is placed
horizontally on the blocks of the old model and vertically on those of
the new model.
2. The right-hand switch, a S. P. S. T. knife switch, is the “power
switch.” When it is closed the D. C. power is on the block and the
automatic switch will function when the corresponding mine is struck.
When it is open the mine can be fired by raising the automatic switch
release, thus tripping the automatic switch.
3. The central switch is the “automatic switch,” a single-pole
double-throw switch, operated by the plunger of a solenoid. Through
its lower arm there passes an insulated pin which, when the switch is
down, makes connection between two contacts to the right and left of
this arm.
If for any cause the current through the solenoid rises above that for
which it is set (normally 0.075 ampere), its plunger is drawn up and
the switch is tripped. Such rise in current is produced when a mine is
struck, the resistance through the circuit-closer circuit being far
less than that through the primary coil of the transformer. Such would
also be the case when a mine cable is grounded.
When the automatic switch is tripped, the D. C. circuit to the mine is
broken at its upper contact (see fig. 18) and D. C. circuit through
red lamp and bell is made through the insulated through pin in the
lower arm, thus giving warning. If at the same time A. C. power be on
the busses and the firing switch on the master block be closed, A. C.
will be thrown on the mine through the lower contact of the automatic
switch, and the mine will be fired.
Just above the plunger of the solenoid there is a red knob attached
to the tripping bar of the automatic switch release. This enables the
automatic switch to be released by hand in observation firing and in
testing.
4. The left-hand switch, a S. P. D. T. switch, is the “testing switch.”
It is used to test the automatic switch, which should open when the
testing switch is thrown down. The bell switch should be opened before
throwing down testing switch. When the testing switch is in this
position, the circuit being broken at its upper contact, the mine is
cut out, and in place of the mine there is thrown in the red lamp of
the signal block. The resistance of this red lamp is greater than that
of the mine circuit when the mine is struck, so that if the automatic
switch works for the current through the red lamp it will certainly
work for that through the circuit closer when the mine is struck.
The circuit when the testing switch, T, is down and _before_ the
automatic switch drops is: From negative D. C. bus on power panel, to
switch 3 closed up, to “operating board” terminal, to D. C. lead, to
D. C. post on signal block, through green lamp, to D. C. jaw, to D.
C. bus on operating board, through power switch, through solenoid to
middle of testing switch T, to lower point of same, to operating board
lamp bus L, through red lamp to “earth” post, to earth lead, to D. C.
“earth” terminal on power panel, to switch 3, and to positive D. C.
bus on power panel. The circuit, when testing switch, T, is down, and
_after_ the automatic switch has dropped, is the same as the above up
to the power switch, then from the power switch through the insulated
pin in the lower part of the automatic switch, to the lower jaw of the
testing switch, and then the same as the circuit above.
A diagram similar to the wiring diagram, figure 18, at the end of the
book should be made of the power panel and of one of the operating
boards of each casemate and posted in a conspicuous place in the
casemate. Any changes made in the wiring of either of these boards
should be made immediately on this diagram.
=Submarine mine cable, 19-conductor.=—This is an armored cable about
1 inch in diameter and contains 19 insulated single conductors of No.
16 American wire gauge wire (51 mils in dia.). The conductors are
arranged in two concentric layers around a single central conductor,
the inner layer containing 6, the outer 12. One conductor in each layer
is distinguished from the rest by some characteristic mark, as a spiral
white thread, a wrapping of tape, or other easily detected mark. The
marked conductor in the outer layer is No. 1, that in the inner layer
No. 13, and the central conductor is No. 19. The other conductors are
numbered at the shore end of the cable in a clockwise direction; at the
distant end in a contraclockwise direction.
=Submarine mine cable, 7-conductor.=—In many cases the 7-conductor
cable now on hand can be used to advantage for mine work, particularly
in planting groups which do not require great lengths of multiple
cable. In all such cases the old grand junction boxes are to be used as
distribution boxes, thus providing for separate groups of 7 mines.
=Submarine mine cable, single conductor.=—This is an armored cable,
about three-fourths inch in diameter, and contains an insulated
conductor made of 7 strands of soft annealed No. 22 American wire gauge
copper wire (25.35 mils in dia.).
=The buoyant mine case.=—The service 32-inch pattern is made of
10-pound, ¼-inch, open-hearth steel, of great toughness and elasticity,
and is thoroughly galvanized. The shell consists of two hemispheres,
ribbed and welded together at the equator, thus avoiding all rivets.
Every case before it is accepted is tested with an internal hydraulic
pressure of 100 pounds per square inch.
The top hemisphere is provided with an external maneuvering ring;
the bottom hemisphere has a hole 5½ inches in diameter at the pole.
The edge of the hole is reenforced by a welded ring 1½ inches thick;
and near it are four bosses, also welded, carrying screw bolts which
project 2½ inches outside to secure the cap.
The cap consists of a hemisphere of 15-pound, ⅜-inch wrought iron,
flanged and dished at the base to fit the case, to which it is attached
by the four bolts already mentioned. They pass through slots in the
flange, which is then held in place by shoes and nuts which are keyed
on. The water has free access to the chamber inside the cap. The uses
of the cap are: To clamp the Turk’s-head of the mine cable, to cover
and protect the portion of the core exposed outside the case, and to
serve as an attachment for the wire mooring rope.
A hole 1½ inches in diameter at the pole of the cap is connected by
means of a slot with a 3-inch hole punched through the cap between
two of the bails. This arrangement permits the entrance or removal
of the Turk’s-head without removing the cap from the mine case. The
mooring attachment consists of a ring of 1½-inch wrought iron, having
a hole 2½ inches in diameter, attached to the cap by three bails of
1-inch wrought iron permanently double riveted to the sides. The cap is
thoroughly galvanized.
[Illustration: FIG. 5.—COMPOUND PLUG, OLD MODEL FUSE CAN.]
[Illustration: FIG. 6.—COMPOUND PLUG, RUBBER FUSE CAN.]
[Illustration: FIG. 7.—COMPOUND PLUG, TROTOL FUSE CAN.]
The large hole in the mine case covered by the cap is closed by a
plug. The joint is made water-tight by a lead washer jammed between
the plug proper and the case and by a coating of red lead or similar
waterproofing material upon the screw threads. In the strong currents
and deep water of some harbors more buoyancy than is possessed by the
32-inch case is required. This is obtained by inserting between the
hemispheres a cylinder of 20-pound wrought iron which is stiffened by
extra welded ribs for the larger sizes. Such cases are designated by
the diameter in inches of a sphere having the same buoyancy. Thus,
a No. 40 case is made by inserting a cylinder 32 inches in diameter
and 20.4 inches in length between the two hemispheres of a No. 32
case; this is sufficient to make the displacement equal to that of a
spherical case 40 inches in diameter. In the latest types the cylinders
are made of corrugated mild steel of less thickness, which diminishes
very materially the weights of the cases.
The following table exhibits the dimensions and weights of buoyant
mines, with trotol fuse cans, complete except the charges and moorings.
The actual free buoyancy when planted will be the difference between
the displacement and weight as given in the table, reduced by the
weight of the charge and of the moorings and cables:
PLAIN CASES.
----+-----------+--------+--------+---------+----------------------
| |Computed|Measured| Length |
No. | Displace- | weight,| weight,| of | Remarks.
| ment. | empty. | empty. |cylinder.|
----+-----------+--------+--------+---------+----------------------
| _Pounds_ |_Pounds_|_Pounds_| _Feet_ |
32 | 635 | 308 | 311 | 0.00 | All are about
| | | | | 33½ inches in
| | | | | outside diameter;
| | | | | the extreme
| | | | | length in each
| | | | | case is 4.3 feet
| | | | | plus the length
33 | 695 | 364 | | .17 |
34 | 762 | 395 | | .35 |
35 | 829 | 427 | | .54 |
36 | 904 | 462 | | .75 |
37 | 982 | 498 | | .96 |
38 | 1,064 | 538 | | 1.20 |
39 | 1,149 | 578 | | 1.43 |
40 | 1,242 | 621 | 625 | 1.70 |
41 | 1,341 | 665 | | 1.96 |
42 | 1,436 | 712 | | 2.24 |
43 | 1,540 | 788 | 759 | 2.53 |
44 | 1,652 | 842 | | 2.77 | One extra welded rib.
45 | 1,767 | 876 | | 3.17 | Do.
| | | | |
| | | | | { Lot of 1879; one
| | | { 899 | } | { extra welded rib.
46 | 1,887 | 952 | { | 3.50 } | {
| | | { 936 | } | { Lot of 1884; one
| | | | | { extra welded rib.
| | | | |
47 | 2,013 | 1,011 | | 3.85 | One extra welded rib.
48 | 2,144 | 1,073 | 1,037 | 4.20 | Do.
----+-----------+--------+--------+---------+----------------------
CORRUGATED CASES.
----+-----------+--------+--------+---------+----------------------
47 | 1,536 | 572 | | 2.24 |
50 | 2,323.2 | 777 | | 4.22 |
----+-----------+--------+--------+---------+----------------------
=The compound plug, with old model brass fuse can.=—A section of this
plug, with the names of all the parts, is shown in figure 5. The brass
fuse can is not used when guncotton is used as a priming charge.
=The compound plug, with rubber fuse can.=—A section of this plug, with
the names of all the parts, is shown in figure 6.
=The compound plug, with trotol fuse can.=—A section of this plug, with
the names of all the parts, is shown in figure 7.
In each plug the main parts are screwed together and held in place by
set-screws. The connection of the compound plug with the mine case
makes an earth plate, of which the electrical resistance in salt water
is about 1 ohm.
=The mine transformer= (see fig. 8).—This consists of a cylindrical
brass case, which contains the primary and secondary coils of the
transformer and the reactance coil. The transformer is screwed into
the brass collar or the reenforce and in turn has the circuit closer
screwed upon its top. The fuses are attached to the secondary and
are fired when proper voltage is applied to the primary. The primary
leads are black; those of the secondary are red. The terminal, P′, of
the primary coil is left free for the purpose of testing, but when
preparing the transformer for use it is attached securely to the
binding post, T. The upper terminal, R′, of the reactance is prepared
for attachment to the ball seat of the circuit closer.
The normal circuit is from P, through the primary coil (the resistance
of which is about 2,400 ohms), to the transformer case, and thence to
earth. However, when the mine is struck, so as to close the circuit
closer, a parallel circuit is closed through the reactance (the
resistance of which is about 130 ohms), thence to the ball seat of the
circuit closer, through the ball and springs to the transformer case,
and thence to earth. In this latter case, therefore, the resistance is
lessened by about 2,300 ohms.
The reactance coil will permit only a small amount of alternating
current to pass through it when the ball is displaced, hence mines may
be fired whether the ball is displaced or not.
[Illustration: FIG. 8.—MINE TRANSFORMER.]
Two fuses are connected in multiple across the ends of the secondary
terminals. These terminals are 10 inches in length, to allow ample
margin for inserting fuses in the primer.
The transformer is of the step-down type and is rated at 22.5 watts, 60
cycles, 500 volts primary, and 14 volts secondary.
The mine circuit when normal is such that 80 volts should give only
30 mil-amperes, but a mine may be fired even when the circuit is so
defective that 80 volts give 120 mil-amperes.
Furthermore, 150 volts D. C. may be applied to the primary without
danger of explosion.
An explosion can not be produced unless the A. C. busses on the
operating board are energized, and as long as the firing switch on the
master block is open, there is no danger from accidental closing of
switches in making mine tests or from short circuits in the mine.
NOTE.—In designing this transformer the following variations were
considered: (_a_) Omitting reactance and tapping to ball seat beyond
primary of transformer; (_b_) using a condenser; (_c_) using two sets
of fuses, so as to be able to fire with either D. C. or A. C. All were
eliminated, as they impaired either the safety, the simplicity, or the
efficiency of the system.
=The circuit closer.=—This, when used with the buoyant mine, consists
of the following parts: The cap, the spring plate, the distance ring,
the steel ball, and the ball seat, which, when assembled, are mounted
on the top of the mine transformer.
=The ground mine case.=—The form and details of construction adopted
for the service pattern are the following (see fig. 9): The case is
cast-iron, in form a segment of a sphere, of which the height is
two-thirds of the radius. The bottom is nearly flat, with a central
sand-hole plug to empty the casting. Six internal radial ribs are added
to give additional supports to the top; the loading hole, 5½ inches in
diameter (3 inches in old pattern), is at the pole and is closed by a
compound plug. Before acceptance a hydraulic pressure of 100 pounds per
square inch must be borne without developing leakage.
Only one size of ground mine has been introduced into our service. This
pattern is designed to contain from 200 to 300 pounds of explosive
and to rest on the bottom in water not exceeding 35 feet in depth at
high tide. The dimensions are as follows: Radius of the sphere, 21⁹/₁₀
inches; diameter of the base, 40 inches; extreme height, 25 inches;
thickness of iron, seven-tenths of an inch; weight, empty in the air,
1,355 pounds; when submerged it loses 515 pounds. The capacity of this
case is about 5 cubic feet.
[Illustration: FIG. 9.—Ground mine case.]
A mine cap is provided to clamp the Turk’s-head of the mine cable, to
cover and protect the portion of the core exposed outside the case,
and to serve as an attachment for the mooring and the raising ropes.
This cap is held to the mine case by six bolts, and is fitted with two
rings, one for attachment of the mooring rope of the circuit-closer
buoy and the other for attachment of the raising rope.
=The compound plug, ground mine.=—This is similar to the compound plug
for buoyant mines. The circuit closer is placed in a buoy above the
mine.
[Illustration: FIG. 10a.—AUTOMATIC ANCHOR.]
=The mushroom anchor.=—The 1,000-pound anchor is in shape a right
cylinder about 10 inches in height and 26 inches in diameter, slightly
dished on the bottom to increase the holding power in mud. For a rock
bottom six projecting toes increase the holding power; corresponding
depressions on the top permit piling when in store. The heavy anchors,
2,000 and 3,000 pounds, are of the same form. The cylindrical form is
adopted to facilitate handling, since in that shape the anchor may be
rolled readily on its edge.
The absolute stress of the mine and its moorings upon a mushroom anchor
of this kind is easily computed, being the square root of the sum
of the squares of the buoyant effort and of the horizontal pressure
exerted by the current. The latter, in pounds per square foot of
exposed cross section, may be estimated at one-half the square of the
velocity of the current in feet per second. A coefficient of safety
should cover the jerking effect of the waves and the shocks of friendly
vessels. It will, of course, vary with the locality and with the
absolute weight of the anchor, but in general a value from 3 to 5 is
considered sufficient.
The holding power of such an anchor varies greatly with the nature of
the bottom. If this be hard, the dead weight alone must be depended
upon; if soft, at least double power may be anticipated. In swift water
the buoyant mine can be better held in position by two anchors chained
together.
=The shackles.=—The wire mooring rope is attached to the anchor and to
the case by shackles, of which there are two sizes. The anchor shackle
consists of a wrought iron strap with two eyes bent into the usual
curved form and offering a thickness of 1½ inches at the bottom, where
the wear and sand cutting is greatest, and of a 1½-inch wrought iron
bolt fitted flush with the outside of the straps. The bolt is held in
position by a split key, which, after insertion through a small hole in
the bolt and one of the eyes (in the old model), is opened so that it
can not work loose.
The mine shackle is lighter, being 1 inch thick at the bottom, with
a 1-inch bolt; otherwise it is identical in pattern with the anchor
shackle.
=Sister hooks.=—They are used to connect the bail of the mushroom
anchor to the anchor shackle. They are of drop-forged steel of high
tensile strength and weigh about 7 pounds per pair.
=The automatic anchor, Artillery type, 1910= (see figs. 10 _a_ and
_b_).—This is a device intended for use with buoyant mines, and by
means of which such mines may be anchored in any depth of water, with
any desired depth of submergence given automatically.
The anchor is bell-shaped, 28 inches in diameter at the bottom, 28½
inches high over all, and composed of the following parts: Body, cover,
reel, journal-box caps, ratchet, pawl, pawl spring, distance rope,
distance weight, brakes, bails, necessary bolts, wrenches, and crank
handles.
The pawl is drawn away from the ratchet by a weight suspended a certain
distance below the anchor. This is called the distance weight, and
the submergence is regulated by the distance this weight is from the
anchor. In falling through the water the mooring rope will unreel and
the mine will remain on the surface, but when the distance weight
reaches the bottom the pawl spring forces the pawl into the teeth
of the ratchet, and as the latter is attached to the reel shaft, it
prevents the reel from turning and hence unreeling.
These anchors weigh approximately 1,500 pounds, including the 200-pound
distance weight.
In order to control the speed of revolution of the reel, the friction
brakes must be adjusted properly. To do this, a pull is put on the
mooring rope with a spring balance rigged to show the amount of pull;
the pull for a particular size of case is determined by experiment.
For a No. 40 mine case the adjusting screws of the brake shoes are
regulated so that the reel will revolve slowly when a pull of 300
pounds is registered.
The pawl spring is 9½ inches long and of such strength that a pull of
36 pounds will extend the spring 1½ inches. The pawl spring bolt is of
such length that the pawl spring will be just at the point of tension
when the top of the pawl spring bolt is flush with the top of the
pawl spring-bolt nut and the pawl fully seated in the ratchet.
When the tidal currents are such as to require a heavier anchor to
hold the mine than the 1,500-pound automatic anchor, the following
combination anchor will be used: Attach a mushroom anchor by means of
a mooring rope (about 8 feet long) and clips to the bail in the bottom
of the automatic anchor. If necessary, two mushroom anchors may be
fastened together by bolts and these attached to the automatic anchor
as stated above.
[Illustration: FIG. 10b.—AUTOMATIC ANCHOR.]
A 3,000-pound automatic anchor, similar to the 1,500-pound automatic
anchor, is supplied for some localities.
=The mooring sockets.=—To connect the wire mooring rope to the shackles
at the mine and the anchor, a closed socket is attached at each end.
The eye of the socket has a clear opening, 1³/₁₀ inches, designed to
receive the bolt of the shackle. The end of the rope is passed into the
socket, spread out, and secured by pouring in a melted socket alloy.
A substitute method for connecting the wire mooring rope to the
shackles is to bend the ends of the mooring rope by means of a small
vise around a galvanized iron thimble and fasten the end by two bolted
clips.
=Wire mooring rope.=—This is the highest grade of ¾-inch
galvanized-steel wire rope, consisting of 6 compound strands, each
made of 19 wires, the whole laid around a steel center. Its breaking
strength when new is about 18 tons. Its weight per running foot,
submerged, is about eight-tenths of a pound. It is used for mooring
mines to mushroom anchors.
=Marline-covered wire mooring rope.=—For mooring mines to the automatic
anchors and for raising rope marline-covered wire rope is used. This
rope consists of five outer strands wound around a central hemp core.
Each of the outer strands consists of a small twisted wire rope wound
around with four strands of marline. One end of the rope is prepared
for attachment to the mine by passing it over a thimble and fastening
it to the standing part by means of two clips. A shackle joins the
thimble and the bail of the mine. The other end of the rope is made
secure to the reel of the anchor. The breaking strength of ½-inch
marline-covered rope is 17,000 pounds, that of ⅝-inch marline-covered
rope is 27,000 pounds. The weight per running foot of the ½-inch rope
is 0.5 pound, that of the ⅝-inch rope is 0.8 pound. The weight of this
rope submerged is about 60 per cent of its weight in air.
About 155 feet of the ½-inch and 85 feet of the ⅝-inch marline-covered
rope can conveniently be wound on the 6-inch reel of the 1,500-pound
automatic anchor.
=Marline-covered wire distance weight rope.=—For attaching distance
weights to the automatic anchor ¼-inch marline-covered wire rope is
used. This rope is identical in pattern with the marline-covered wire
mooring rope.
=The distribution box, 19-conductor.=—This is a circular, cast-iron,
disk-shaped box which receives the end of the multiple cable, in which
taped joints are made between the separate conductors of this cable
and the single-conductor mine cables, and from which these mine cables
radiate. It is about 27 inches in diameter and weighs about 300 pounds.
It consists of two parts, a bowl-shaped bottom 6 inches deep inside and
a slightly curved lid. The latter has an iron ring in its center by
which the box is raised and lowered.
Eight pins, fastened to the bottom, fit in corresponding holes in the
edges of the lid and are slotted for keys by which the two parts are
fastened together.
The vertical edge of the bottom is cut with 20 slots, each about 2½
inches deep. One of these is larger than the others and receives the
multiple cable; the others are for the single conductor cables. When
in use these slots are numbered clockwise from the multiple-conductor
slot, looking down into the box. The lid has corresponding projections
or lugs which enter these slots, and which, in position, fit snugly
against the cable ends. The cables are held from being pulled out by
Turk’s-heads worked upon them.
To prevent the cable ends from accidentally slipping out of the slots
while joints are being made between them before the lid is put on,
the multiple cable is secured by a bolted collar on the inside of the
box, the single-conductor cables by clipping their Turk’s-heads under
claw-like radial projections cast upon the inside rim between the slots.
=The distribution box, 7-conductor.=—This box is used with multiple
cable, 7-conductor. It consists of two circular plates of cast-iron 21
inches in diameter and three-fourths of an inch thick united by four
1-inch bolts, which are placed in rounded projections forming the
angles of a square. The cables are separately clamped, the top plate
overlapping the clamp straps. The multiple cable enters on one side;
three single-conductor cables enter on the opposite side, and two
on each of the intermediate sides. The top plate is provided with a
lowering ring.
=The junction boxes.=—These boxes, in different sizes, are used in
splicing multiple and single-conductor cables; they consist of two
rectangular plates of iron or steel united by four ½-inch bolts at the
corners. The plates are hollowed in the middle to form a chamber to
receive the Turk’s-heads and the joints connecting the conductors. The
ends of the plates are curved to admit the cable ends. The Turk’s-heads
are clamped to the lower plate by straps and screw bolts, the cavity of
the upper plate covering them when bolted in position. Each cable end
is thus made fast before the box is closed.
=The distribution box buoy.=—This buoy is used to mark the position of
the distribution box during the planting of mines and subsequently, in
practice and in service, until such time as the mine commander desires
to remove it. It may be either a can or a keg buoy—a beer keg of
one-half barrel capacity is well suited for this purpose.
=The mine buoy.=—This buoy is used to mark the position of the mine
when planted. It may be a small can buoy, preferably cork filled, or
a piece of wood with a hole bored through it. The size of the buoy
is determined by the swiftness of the current. It is attached to the
maneuvering ring of the buoyant mine by 60 feet of ½-inch rope.
=The measuring reel and frame.=—The frame consists of two longitudinal
pieces, 3 by 4 by 66 inches, placed 17 inches apart, center to center.
At 11½ inches from each end two cross pieces, 3 by 4 by 20 inches in
length, are fastened to the longitudinal pieces with through bolts. At
the center point of these cross pieces are placed standards, 3 by 4 by
16¾ inches, which have journals for the axle of the reel, counter-sunk
in their upper ends. Two iron braces, one on each side, hold each
standard firmly in a vertical position. An iron clamp is also attached
to the upper ends of the standards, by means of which the axle is
prevented from jumping out of the journals. Distance from center to
center of standards is 43 inches.
The iron axle of the reel is 1½-inch round iron, 54 inches in length.
At each end of the axle a screw thread is cut for the nut which holds
the crank in place. Inside the screw thread the axle is squared to
receive the socket of the crank. Two collars prevent the wooden
reel from binding on either standard. The cranks are of the usual
design. The drum of the reel is 8½ inches in diameter; heads are 2½
inches thick, made in two layers, cross-grained, and are 24 inches
in diameter; length of drum over all is 36 inches. Iron plates are
fastened in the center of each head, through which the axle passes. The
reel is prevented from turning on the axle by keys.
Three ¾-inch rods pass through the iron plates and drum and bind these
parts firmly together.
At 6 inches from the ends of the longitudinal pieces a hole is bored to
receive a lag screw, ½ inch by 6 inches, by means of which the whole
apparatus can be firmly fastened to the deck.
The brake is a piece of 3 by 3 by 36 inch hardwood, used as a lever to
bring pressure on the drumhead. There is one for each side, and, when
not in use, each rests on one of the longitudinals, being held in place
at one end by two staples and at the other end by a bolt and pin.
Near the drum on one head is a hole through which the inner end of the
measuring line can be passed and stapled to the outside of the head.
=The cable-reel frame.=—The frame is made in two parts which, when in
use, are held in proper relative positions by means of two iron ties
provided with turnbuckles at their centers. The ends of these ties are
bent over at right angles and fit in sockets in the two end parts.
Each end part consists of a standard having an iron head through which
works a screw turned by a small lever, the upper end carrying a journal
in which the end of the reel axle rests. The lower end of the standard
rests on a horizontal piece and has a diagonal brace on each side, the
outer ends of these braces being dovetailed into the longitudinal piece
and the inner ends into the standard near the top. Dovetailed into the
longitudinal piece at its middle point is a piece extending out at
right angles, bottom flush with bottom of the longitudinal. A diagonal
brace similarly fastened prevents any outward movement of the standard.
The whole is held firmly together by bolts and lag screws.
[Illustration]
[Illustration: FIG. 11.—BOAT TELEPHONE, MODEL 1906.]
Lag screws are also provided, by means of which the ends of the frames
can be fastened to the deck of the vessel if desired.
The reel axle is 2½ by 2½ inch squared iron, rounded at the ends for 6
inches to fit the journals of the frame. A disk secured by a set-screw
at one end of the axle and the friction brake wheel at the other end
hold the axle in position with respect to the reel.
The brake wheel is 18 inches in diameter. The friction band is 1½
inches by ⅛ inch, and is fastened at one end to one of the standards of
the frame. The other end is attached to a lever whose fulcrum is also
attached to the same standard.
=Boat telephones.=—The different models in use are as follows:
(_a_) _Model 1904._—The system consists of two telephone hand sets, a
buzzer, and a battery of dry cells of about 8 volts, all connected in
series by means of cable and earth connections.
In operating the telephones a call is made by pressing the button, and
when talking the lever is held down.
(_b_) _Model 1906._—The system consists of two telephone hand sets,
a reactance coil, and a source of energy that will furnish about 15
volts, dry cells preferred, connected as shown in figure 11. The
terminals do not have to be poled, as the receiver is not in the
primary circuit and can not be demagnetized.
To regulate the buzzer, remove the cap in the base and with a small
screw driver loosen the lock nut on the center screw (a small portion
of a turn is all that is necessary). With a smaller screw driver the
screw may be adjusted to increase or decrease the rate of vibration,
increasing or decreasing the sound. Then tighten the lock nut. In case
the contact is dirty the entire buzzer and condenser may be removed
by disconnecting the cord and removing the screw on the back of the
telephone just below the call button. As the contacts are aluminum,
this will seldom have to be done.
(_c_) _Model 1909._—The system consists of two telephone hand sets, an
apparatus box, and a battery of from 7 to 10 volts, all connected as
shown in figure 12. The talking and ringing circuits are normally open
at the talking and ringing buttons, respectively.
_Apparatus box._—Seven dry cells in series should be connected to the
posts of the apparatus box marked “+” and “-,” and the post marked “G”
connected to a ground plate.
_Shore hand set._—The blue cord of the shore hand set should be
connected to the ground plate. Either of the red cords of the shore
hand set should be connected to the post in the apparatus box marked
“L” and the other to the conductor in the cable that is to be used for
telephoning purposes.
_Boat hand set._—The blue cord of the boat hand set should be connected
to the ground plate and one of the red cords to the conductor in the
cable to which the hand set on the shore is connected. The other red
cord is free.
_Signaling._—From figure 12 it will be seen that in either hand set,
when neither the ringing nor the talking switch is closed, a condenser
within the hand set is in series with the transmitter and the receiver,
so that the practical effect is to permit an alternating or variable
current to pass through the transmitter and the receiver, but to
prevent a direct or continuous current from so doing.
By pressing the ringing key of either hand set the circuit in that
hand set is closed through the 1,000 ohms resistance and the receiver
to ground. Thus, when the ringing key of the boat hand set is pressed,
this allows the direct current from the battery to pass (see fig.
12) through f, e, d, c, “B,” b, a, line, the ringing key, 1,000-ohm
resistance, and receiver of the boat hand set, to ground, and back
through o and p to battery. Similarly, a circuit through the battery,
f, “A,” and a, is made, thus placing relays “A” and “B” in parallel.
The relay “B” operates, but relay “A,” being less sensitive than “B,”
does not operate. Relay “B” closes the circuit at l, and thus completes
the circuit from battery through f, e, d, c, k, l, “C,” o, p, back
to battery. This causes relay “C” to operate and to complete a local
circuit from battery through f, e, d, k, m, s, primary, t, vibrator,
p, back to battery, causing the vibrator to vibrate and inducing in
the secondary winding of the induction coil an alternating current,
which passes through the 1 M. F. and 2 M. F. condensers, through the
hand sets in parallel, and by alternately increasing and decreasing the
attraction of the receiver magnets for their diaphragms produces a loud
humming sound in each receiver.
Similarly the shore station may call the boat station.
[Illustration: FIG. 12.—BOAT TELEPHONE, MODEL 1909.]
_Talking._—When the ringing key is released and the talking key is
depressed the 1,000-ohm resistance is cut out and the condenser in the
hand set is short circuited. The current is then sufficient to operate
relay “A,” and this relay in operating allows the other relays to
resume their normal positions.
When the variations in the pressure upon the transmitter diaphragm
in either hand set varies the resistance of the corresponding branch
circuit a slight variation in the current from the battery is produced.
The internal resistance of the battery is sufficient to produce a
slight variation in its terminal voltage. The resulting variations in
the line voltage, and hence in the drop across the receivers, produce
the usual vibrations in the receiver diaphragms. These variations also
produce slight variations in the current through the primary winding
of the induction coil, resulting in greater variations across the
terminals of the secondary winding. Since the secondary winding is
in series with the battery, the practical effect is to amplify the
variations in the line voltage, and hence in the talking currents.
Successful working of the relays is obtained only by a careful
adjustment of the screws which regulate the throw of the armatures. The
relay “A” is located in front of the “+” battery post, the relay “C” in
front of the “G” post.
In addition to the above matériel there are necessary for the mine
system certain electrical instruments, as well as tools, appliances,
and supplies requiring no special description, which are enumerated in
the supply list. (Appendix 8.)
Figures 17a and 17b, at the end of the book, show the construction of
an improvised mine target.
CHAPTER III.
LOADING ROOM DUTIES.
=Making a telegraph joint.=—The insulation is removed from the ends for
1½ inches and the wires brightened. The ends to be joined are placed
across each other about one-third distance from the insulation, making
an angle of about 45° with each other. The wires are grasped firmly at
the junction and each free end wound tightly around the other wire for
four turns; the winding should be in opposite directions. The ends of
the wires are trimmed down so they will be smooth and present no sharp
points.
When wires are joined with brass jointers three-fourths inch of each
wire is bared and the wires are inserted in the jointer; each end is
crimped with pliers in the direction of the longer axis; the rest of
the jointer is crimped and the ends or sharp points rounded off. When
brass jointers are used care should be exercised not to crimp them
too hard, as the wires may be partly cut through and finally broken.
Special care must be used with the fuse leads, as the secondary circuit
of the mine transformer can not be tested after the compound plug is
assembled.
=Insulating a joint.=—A piece of rubber tape about 2 inches long is
used, with ends cut diagonally. The tape is stretched, and starting
at a point about three-fourths inch back on the insulation, with the
long edge of the tape on the inside, it is wound around the joint under
tension, each turn covering the previous turn about one-third. The
wrapping is continued until the same amount of insulation is covered on
each side, when the wrapping is worked backward over the joint and the
end is secured by pressing it firmly a short time or placing a drop of
cement under it.
=Making a water-tight joint.=—The two ends of wire are scraped clean
for about three-fourths of an inch and joined by a brass jointer,
which is then crimped. The insulation is scraped clean about 2 inches
on each side of the jointer and covered with rubber cement. (Cement
is not absolutely essential.) Two strips of rubber tape are cut about
6 inches long, with diagonal ends, and stretched. Beginning about
1½ inches along the insulation, the tape, with the long edge on the
inside, is wrapped firmly and tightly until about one-fourth of an inch
of the insulation on the other side is covered; it is wound back and
forth over the joint so as to taper toward the ends. The other piece
of tape is used, beginning at the other end and wrapping as before.
The finished insulation should be thick at the middle and taper toward
the ends. It should be firm and tight. The insulation is covered with
tin foil, wrapped with protective tape, and vulcanized for about 30
seconds. The protective tape and tin foil are then removed, the joint
inspected, and new protective tape wrapped on, using two pieces,
starting at opposite ends and finally ending each beyond the center.
=Making a Turk’s-head.=—The cable is trimmed square and a wrapping
of four or five turns of marline is made about 15 inches from the
end. The collar, flat side first, is slipped on until it rests on the
marline; the iron wires are bent back regularly over the collar. The
jute wrapping is unwound to the collar and trimmed, and all the iron
wires are cut with the pliers, removing all but 4 inches and 6 inches
from alternate strands; the iron wires are bent separately to fit the
collar closely (making two right angles with the pliers), and the ends
arranged smoothly along the cable; the end of a piece of marline is
engaged under one of the wires near the collar and wrapped regularly
and closely around the cable, and the free end of marline secured with
two half hitches. About 15 feet of marline are required for single
conductor cable; 24 feet for multiple cable.
=Testing fuses.=—The following apparatus is used for testing in the
loading room: A double-pole double-throw switch, a 150-volt voltmeter,
and sufficient dry cells to give a full throw when using the lower
scale of the voltmeter. The apparatus is connected up on the testing
table so as to make resistance measurements by the voltmeter method.
To test fuses, leads are carried from the switch to an iron or other
suitable receptacle outside of the building and the fuse leads joined
thereto. A full deflection should be obtained when the circuit is
closed through the fuses.
=Preparing a compound plug for service.=—The transformer to be used is
first tested for a good circuit between the red wires, a poor circuit
between the ends of the black wire, a good circuit between the black
or primary lead and the reactance terminal, no circuit between the red
and black wires, and no circuit between any wire and the case. The
resistance of the circuits is determined by the voltmeter method. The
upper end of the black wire (see fig. 8) is prepared for use by baring
the wire for about one-half inch and securing it to the binding post in
the neck of the transformer. The ball seat is screwed home. The spring
plate, distance ring, and ball are placed in the circuit-closer cap,
which is held inverted and the transformer screwed into it, the threads
being coated with ruberine.
(_a_) =Old model, brass fuse can.=—Starting with the compound plug
dismantled.
A piece of loading wire is cut about 3 feet long and the ends bared.
One end is joined by a telegraph joint to the primary terminal of the
transformer and the joint is taped. This wire and the two secondary
wires are drawn through the fuse can, which is screwed on the
transformer, the threads of the latter having first been coated with
ruberine.
Two mine service fuses, which have been tested for continuity of
circuit, are connected in multiple across the secondary (red) terminals
and the joints taped.
The can is held vertically and the explosive, if trotol, poured in
up to the screw threads for the fuse can cap; if dynamite, inclosed
in a cloth bag and placed in the can. The fuses are embedded in the
explosive.
The loading wire is drawn through a lead washer and the fuse can cap;
the latter, its threads having been coated with ruberine, is screwed
into place.
A rubber packing is pushed over the loading wire into the stuffing
box in the fuse can cap, a brass gland is threaded down so that it is
close against the rubber packing, and the follower is screwed home with
moderate pressure. The lower tube is screwed into place, compressing
a lead washer between it and the fuse can cap. The threads of the
follower and lower tube are coated with ruberine.
The loading wire is drawn through a lead washer and the hole in the
plug proper, and the latter screwed hard against the lower tube.
A rubber packing and a brass gland are placed upon the loading wire and
forced into their seat in the plug proper by means of the follower, the
threads of which have been coated with ruberine.
(_b_) =Rubber fuse can.=—Starting with the compound plug dismantled.
Two mine service fuses, which have been tested for continuity of
circuit, are cut with 9-inch leads, wires bared for about 1 inch and
connected in multiple. A piece of loading wire is cut about 3 feet long
and the ends bared for telegraph joints. It is threaded through a hole
in a cake of dry guncotton. The two fuses are inserted by pushing each
separately into the same hole and the loading wire drawn up until it is
the same length above the cake as the fuse leads.
Three other primer cakes are threaded on the wire; two above the fuses,
and one below. This arrangement will leave the fuses in the third cake.
The cakes are held in one hand with the fuse leads upright, and the
fuse can slipped over the cakes, being careful to thread the fuse leads
and loading wire through the opening.
The screw threads of the fuse can cap are covered with ruberine and it
is screwed firmly into place onto the fuse can. The stuffing box of the
cap is assembled.
The plug proper is held upright in a vise. The fuse can, the threads
of the cap having been coated with ruberine, is screwed home and
secured by its set-screw. The loading wire must be pulled through the
opening in the plug proper with extreme care. It must not be injured
in placing the fuse can in position and in screwing it home. The
transformer leads are cut about 6 inches long, and the ends bared for 1
inch. The brass collar is screwed on the transformer; a little ruberine
on the screw threads facilitates the operation. The connecting collar
is slipped over the fuse leads and loading wire and allowed to rest
on the fuse can. The transformer is supported by allowing two of the
connecting bolts to slip into the holes in the collar; telegraph joints
or brass jointers may be used between the secondary leads and the fuses
and between the primary lead and the loading wire. The joints are wound
with rubber tape, care being taken that there are no sharp ends to cut
through the tape.
The transformer is raised vertically above the fuse can until the lead
wires are extended. It is lowered and at the same time the leads are
coiled in the base of the transformer. As the transformer and collar
approach their position on the connecting bolts, the connecting collar
is screwed on the transformer, the threads of the transformer having
been covered with ruberine. The connecting collar will take care of
the remainder of the leads and joints. The set-screw in the connecting
collar is screwed home; the brass collar is placed on the connecting
bolts and secured in position by the nuts and cotter pins.
The lips of the fuse can and connecting collar are covered with a
thin covering of rubber cement. A piece of rubber tape is cut about
18 inches long and laid around this opening without stretching. A
piece of protective tape is cut about 18 inches long and laid over the
rubber tape with considerable stress. This forces the soft tape over
the lips on the connecting collar and the fuse can and makes a tight
but flexible joint. The stuffing box in the plug proper is prepared as
under (_a_).
Great care must be taken not to injure the insulation of the loading
wire in tightening up the follower in the stuffing box of the fuse can
or of the plug proper.
(_c_) =Trotol fuse can.=—Starting with the compound plug dismantled.
Two mine service fuses, which have been tested for continuity of
circuit, are cut with 12-inch leads, the wires bared for 1 inch and
connected in multiple. A piece of loading wire is cut about 3 feet long
and the ends bared for telegraph joints. The loading wire is threaded
through the fuse can and cap. The threads of the fuse can are covered
with ruberine. The can is screwed into the cap. The threads of the
connecting collar are coated with ruberine and the collar is screwed
down entirely. The loading wire should project about 4 inches above the
connecting collar. The stuffing box of the cap is prepared. The plug
proper is held upright in a vise. The fuse can cap, its threads having
been coated with ruberine, is screwed firmly into the plug proper by
means of a spanner wrench. The loading wire must be pulled through the
opening in the plug proper with extreme care. It must not be injured in
placing the fuse can in position and screwing it home.
The fuses are inserted in the fuse can, which is filled with trotol
to the top of the connecting collar. The transformer leads are cut 4
inches long and the ends bared for 1 inch. The threads of the brass
collar are covered with ruberine. It is screwed on the transformer.
The latter is raised vertically above the fuse can and lowered on the
connecting bolts.
Telegraph joints are made between the secondary leads and the fuses
and the primary lead and the loading wire. The joints are wound with
rubber tape, care being taken that no sharp ends cut through the tape.
The leads and joints are coiled in the base of the transformer. The
connecting collar, its threads having been covered with ruberine,
is screwed upon the transformer against the brass collar. The
bolt-securing nuts and cotter pins are placed in position. The stuffing
box in the plug proper is assembled as under (_a_).
The actual resistance of the assembled plug in the vertical and the
horizontal positions is determined by testing with a voltmeter.
In service, after the loaded plug tests out satisfactorily, all set
screws are set up.
When compound plugs are prepared for drill or for instruction purposes
the use of ruberine or other waterproofing material on the screw
threads is omitted; care must be taken that the transformer leads are
not needlessly shortened.
=Loading a mine.=—The mine case is carried from the storeroom to the
loading room and placed on a loading skid or other receptacle with
the loading hole up. The plug is removed and the screw threads are
thoroughly cleaned. The explosive detail brings in a box of explosive
from the explosive house and inserts a loading funnel into the loading
hole. The charge for a 32-inch mine case is 100 pounds of explosive.
For the larger cases, the charge should be the maximum that the
conditions warrant; it is specified at present as 200 pounds, though
larger charges are desirable if enough explosive can be obtained and
the excess buoyancy of the case will warrant the use of more than
200 pounds. The cartridges of dynamite, the trotol, or the blocks of
guncotton are inserted by hand and so placed in the mine case that
there will be ample room for inserting the compound plug. Only one box
of explosive for each mine being loaded is brought into the loading
room at one time. After the proper amount of explosive has been placed
in the mine case the screw threads are thoroughly cleaned with button
brushes and then coated with ruberine or other material to prevent
access of water. The compound plug, with its screw threads similarly
coated, is screwed home with the socket wrench, a lead washer being
used between the plug and mine case. A bar put through holes in the
sides of the skids and through the maneuvering ring will prevent the
case from falling over and from turning while the compound plug is
being screwed home.
In order to insure setting the compound plug tight, it is advisable to
tap the end of the lever of the socket wrench a few times with a large
mallet or a large wooden bar. The mine cap is bolted on and the mine
put in a tank for test. If time admits, it may remain in the water 24
hours. It should show practically the same resistance as the compound
plug. If this test be made, the loading wire must be long enough for
this purpose.
Upon completion of this test the mine is taken from the tank, the
loading wire pushed inside the cap to avoid injury in handling, and the
loaded mine taken to the planting wharf.
The precautions to be observed in handling explosives and loading mines
are given in Appendix 1.
CHAPTER IV.
LOCATING DISTRIBUTION BOX, LAYING MULTIPLE CABLE, AND MARKING OUT MINE
FIELD.
(NOTE.—The operations in Chapters IV and V are
described in what is thought to be the logical order, but
circumstances may alter their sequence, and, in fact,
several of the steps may be carried on simultaneously.)
For the work on the water there will be needed five boats, viz., a mine
planter or suitably fitted-up heavy tug, a small tug or heavy launch
called the distribution box boat, and three launches or yawls. The
capacity of the planter is such that a group of 19 mines can be handled
at one time.
The instructions to be observed by the master of a mine planter in
marking out a mine field and in planting mines are to be found in
Appendix No. 6.
=Determining location for distribution box.=—From an examination of
the chart, or of the approved scheme for mining, the locations of the
lines and groups of mines are determined. A distribution box is to be
placed about 350 feet in rear of the center of each group of mines. The
locations for the distribution boxes are marked on the plotting board
and their azimuths from each of the ends of the horizontal base or
their azimuth and range from the vertical base station are determined.
=Marking location of distribution box.=—An anchor with buoy attached
is placed upon the deck of a small tug and carried out to one of the
selected spots. By a system of signals the boat is directed to the
location determined and there the anchor is thrown overboard. The
locations for the other distribution boxes are marked in a like manner.
=Laying multiple cable.=—The cable-reel is placed upon the forward
deck of the planter and raised on the jacks. The planter then proceeds
as near the mining casemate as the depth of water permits, and one end
of the cable is passed ashore, either by a launch, by yawls, or by any
other suitable method. In case the planter can not approach nearer the
shore than 100 yards it will be necessary to coil more than enough
cable to reach the shore in a figure of eight in a yawl, which is then
towed toward the desired point on shore, the men aboard the yawl paying
out the cable as it proceeds. This end is drawn in through the conduit
or gallery to the casemate or terminal hut. It may be secured by taking
a telegraph hitch around it with a chain and spiking the chain to some
heavy timbers or fastening it to some holdfast. When cable ends have
already been laid they will be picked up and joined to the multiple
cable for the groups.
The shore end having been secured, the planter moves out to the
position of the distribution box, unreeling the cable as it goes.
If the water be very deep, a friction brake must be extemporized to
prevent the reel from overrunning. (While the planter is laying the
cable, the casemate party tags and attaches the shore end as explained
later.) To prevent kinks as far as possible cable should be laid with
as much tension as practicable.
If the cable is not long enough, a second one must be joined to it.
This is preferably done by passing the ends to a small boat. The
junction is made, either using a junction box with Turk’s-heads and
taped joints, or opening back the armor for about 5 feet from the ends,
making taped joints, protecting them with tape, and then rewrapping the
armor and seizing the ends with wire. Care must be taken to join the
proper conductors of the two ends.
In the meantime the distribution box boat with a detachment of one
noncommissioned officer and five men takes the distribution box and
moves out to the spot marked by the buoy. It picks up the buoy and
makes fast to the anchor line.
The planter continues laying the multiple cable until it reaches the
distribution box boat. The multiple cable is then cut and the end
passed to the distribution box boat, usually by a heaving line. The
cable is lashed to the boat; a Turk’s-head is worked upon the end and
then secured in the distribution box. As a precautionary measure for
the recovery of the distribution box, should it be lost overboard
during mine planting, it is well to have the multiple cable buoyed
about 100 yards in rear of the distribution box.
In case it may be desired not to use the distribution box at once, the
separate conductors of the multiple cable should be tagged, tested,
and insulated. The cable should be buoyed and dropped overboard to be
recovered subsequently.
=Identifying, tagging, and testing the conductors of the multiple
cable.=—_Tagging._—In the casemate the conductors are separated,
carefully identified, tagged, and attached to the corresponding
terminal of the terminal bar on the operating board. The mine switch
for No. 19 is opened and the telephone terminal attached to its stud
so as to use No. 19 for communicating with the distribution box boat.
The ends in the distribution box boat are separated, one terminal of a
boat telephone is attached to No. 19, and the other earthed either by
attaching to the cable armor or to an earth plate hanging overboard in
the water. Communication is thus established with the operator in the
casemate. Nos. 1, 13, and 19 are picked out easily; the remaining ones
are tagged in contraclockwise direction.
_Verifying the tagging._—The casemate is then notified that the boat
party is ready to check the tagging. This is done as follows: The power
switches on the operating board are all closed, except 19, and direct
current put on the cable by closing switch No. 3 up. The casemate
operator then directs the boat party to earth in regular succession the
various conductors. This is done most quickly by touching the conductor
to the cable armor. The corresponding automatic switch on the operating
board should drop. Any errors in tagging detected by this test should
be corrected at once. This test also checks the continuity of circuit
of each conductor.
_Insulation test._—The operator then directs the boat party to prepare
the cable end for insulation test. This is done by separating the
conductors, holding them in the air, and drying them if necessary.
When prepared, word is sent to the casemate operator, who tests as
follows: He closes switch No. 7 up. This throws D. C. power on the
mil-ammeter plug of the operating board and introduces in the circuit
the mil-ammeter and its protective lamp. The green lamp is then
unscrewed and the mil-ammeter plug used on the D. C. jaw.
If there be no leak in the multiple cable, since the ends at the
distribution box boat are held in the air, there will be no appreciable
reading of the mil-ammeter.
If there be a leak, this fact will be revealed by a reading on the
mil-ammeter. To discover the particular conductor or conductors on
which this leak exists, each power switch is opened in succession and
the mil-ammeter plug inserted on the jaw of the power switch.
No. 19 is now tested in the same way by first shifting both telephones
to No. 1, the boat end being held in the air. The operator reports the
result of the test.
Upon completion of these tests the power is turned off. Post power
should not be used for testing, because the negative side of the post
power may be grounded.
=Marking out the mine field.=—In using automatic anchors it is not
necessary to mark the mine field; but in using mushroom anchors it is
generally done. The material required consists of 1 measuring line with
reel and frame, 5 anchors, 5 keg buoys, and 5 raising ropes.
A buoyed anchor is dropped about 350 feet in front of the
distribution box buoy. This marks the position of mine No. 10 and of
the center of the group.
This marking buoy is picked up by a launch which makes fast to the
anchor rope. The planter now passes to the launch one end of a
measuring line, which has marks at 280, 300, 350, 580, and 600 feet.
These marks may be made by painting 3 feet of the measuring line
some distinctive color at the designated points. The planter moves
out slowly along the line to be occupied by the mines, unreeling the
measuring line as it goes, and drops buoys at the 300 and 600 foot
marks. It then returns and does the same for the other side of the
line. These five buoys mark the line to be occupied by the mines,
indicate the positions of mines Nos. 4, 7, 10, 13, and 16, and in
addition cut up the distance into 300-foot lengths, which enable the
planter to plant mines at a close approximation to 100 feet apart.
=Taking soundings on line of mines.=—When automatic anchors are used,
such information as may be required about depth of water may usually
be obtained from charts. This may not be sufficiently accurate for
planting with ordinary anchors. In the latter case soundings must be
taken at the spots where the mines are to be planted.
These soundings are made from the launches. The launches take a
measuring line marked at every 100 feet, stretch it between the planted
buoys, and take the soundings at every 100-foot point. The soundings
are recorded in a blank book showing the number of the corresponding
mine and state of the tide. It may be found more satisfactory to hold
one end of the measuring line at the buoy and circle across the line of
mines with the launch, getting the sounding at the point of crossing.
=Preparing mooring ropes.=—The mooring ropes are cut off with square
ends, and the ends passed through the holes in the mooring sockets. The
strands and wires are untwisted and spread out for a length equal to
the length of the socket hole. The rope is pulled back until the ends
are about flush with the top ends of the hole; a piece of marline is
tied about the rope below the socket. If necessary to hold the socket,
a piece of burlap may be wrapped around below the socket, and a fold
allowed to fall over the hand. Generally, means can be found to set
the socket upright while pouring full of alloy. The alloy consists of
9 parts of lead and 1 part of antimony melted together. A melting pot
heated by a plumber’s furnace, or preferably a Khotal lamp, is used for
this purpose. Great care must be taken to see that there is no oil or
water on the socket or mooring rope before pouring the alloy.
The length of the mooring rope for buoyant mines No. 32 equals the
depth at low tide, less 15 feet. This allows 5 feet for the length
of the mine, anchor, and shackles, and 10 feet for submergence. When
thimbles and clips are used the mooring rope is cut 3 feet longer and
is bent back a foot and a half at each end for the thimbles and clips.
For the larger mine cases, an additional allowance must be made for the
length of the cylindrical part of the case.
Each mooring rope is carefully tagged at each end with the number of
the corresponding mine.
CHAPTER V.
ASSEMBLING AND PLANTING MINES.
NOTE.—The instructions to be observed by the
master of a mine planter in marking out a mine field and in
planting mines are to be found in Appendix No. 6.
=The planter detail.=—This consists of the chief planter and 3
noncommissioned officers and 16 privates, distributed in three details,
as follows: One noncommissioned officer and six privates on each side
of the planter and one noncommissioned officer and four privates aft.
=Tools and supplies.=—The tools and supplies to be taken aboard for the
work described are:
On the planter.
Alcohol.
Anchors.
Axe.
Boat hooks.
Buoy, key.
Buoys, mine.
Cable cutter.
Cables, multiple.
Cables, single conductor.
Cable tags.
Clips, cable.
Cotter pins.
Crank handle for automatic anchor.
Dry cells.
Grappling hooks.
Hammers.
Heaving lines.
Kerosene.
Knives, submarine mine.
Lamps, alcohol (2).
Life buoys (3).
Marline.
Marlinespikes.
Matches.
Megaphone.
Mines.
Monkey wrenches.
Nuts.
Ropes, mooring.
Ropes, raising.
Shackles, anchor.
Shackles, mine.
Shoes, mine-cap.
Sister hooks.
Spring balance.
Stamping outfit.
Tools and materials necessary to make Turk’s-heads and joints.
Voltmeter.
Washers.
Waste.
Wire, soft-drawn copper.
Wrench, socket, for automatic anchor.
On distribution box boat.
Alcohol.
Anchors, boat (2).
Axe.
Boat hook.
Boat telephone with connectors and earth plate.
Breaker of drinking water.
Buoy.
Cable tags.
Compass, boat.
Distribution box.
Flags, boat (2).
Gasoline (tankful).
Green light.
Hammers.
Heaving lines.
Kerosene.
Knives, submarine mine.
Lamps, alcohol (2).
Lashings.
Life buoys (2).
Life preservers, one for each man.
Marline.
Marlinespike.
Matches.
Megaphone.
Monkey wrenches.
Notebook and pencil.
Red light.
Rope, raising.
Ropes, buoy (2).
Shackles.
Tools and materials to make Turk’s-heads and joints.
Waste.
White lights (2).
In each yawl.
Anchor, boat.
Anchor line.
Boat hook.
Heaving line.
Life buoy.
Life preservers, 1 for each man.
Marline.
Megaphone.
Oars and locks (7).
Sounding line.
=Preparing mine cables.=—A reel of single-conductor cable is taken from
the tank and placed on a cable-reel frame. A piece 20 feet long is cut
off the end to eliminate the part which was above water during storage.
The cable for the mines is now unreeled, cut to the following lengths
_plus twice the approximate depth of the water_, and each end carefully
tagged with the number of the corresponding mine. A Turk’s-head is made
on each end.
Feet. Feet.
No. 1 1,425 | No. 11 425
No. 2 1,225 | No. 12 475
No. 3 1,025 | No. 13 525
No. 4 825 | No. 14 625
No. 5 725 | No. 15 725
No. 6 625 | No. 16 825
No. 7 525 | No. 17 1,025
No. 8 475 | No. 18 1,225
No. 9 425 | No. 19 1,425
No. 10 375 |
The mine cables are coiled in figure 8’s. In order to secure uniformity
in the size of the coils, they may be coiled on a rack (improvised
at the post). This rack is made of one 12-foot length of 4 by 6-inch
scantling, crossed at right angles by two 6-foot lengths (4 by 6 inch)
placed 5 feet apart. Four 1-inch holes are bored through each of the
timbers about 2 feet from each of the crossings, and a 2-foot length of
gas pipe is inserted in each hole. These pipes make the form on which
the coils are made.
A cable must be coiled for planting so that both ends are free, one to
be passed to the distribution box boat, the other to be carried forward
on the planter and attached to the mine. This is accomplished by
starting the coil about 135 feet from the mine-cap end, the approximate
length required to run forward when using a mine planter. The cable
is coiled on the form, spreading out the laps at the center to reduce
the height at that point, until the entire length is coiled. The outer
loops and the center of the figure 8 coil are lashed, leaving the ends
sufficiently long to lash the part of the cable remaining uncoiled. The
mine-cap end of the cable is then coiled on top of the coil and lashed
with the ends of the rope.
Single-conductor cables when coiled should be tested for continuity of
circuit and grounds before being placed aboard the planter.
For continuity of circuit the two ends of the cable are connected to a
battery and voltmeter in series. If the cable has no break, the reading
of the voltmeter should show approximately the same deflection as when
the battery circuit and voltmeter alone are in circuit.
To test for a ground the cable is submerged in a testing tank, leaving
both ends out. It is advisable, when practicable, to extend a lead
from one of the operating boards of the mining casemate to the cable
tank. One end of the cable to be tested is connected to this lead and
the test made as prescribed for “insulation test” on page 44. The
condition of a multiple-conductor cable can be quickly determined by
this arrangement. If the above method is not practicable, a dry-cell
battery with a mil-ammeter and protective lamp may be installed at
the cable tank; or, in place of the mil-ammeter and lamp, a voltmeter
placed in series with the battery and cable may be used, the resistance
being obtained by the voltmeter method. One side of the battery should
be grounded by touching the cable armor or by using an earth plate. In
actual service, cable which tests under 1 megohm should not be used;
for practice, cable under 10,000 ohms should not be used. If post power
is used as a source of energy for testing, the system should be free
from grounds. Care should be taken to have the cable ends and battery
leads free from grounds and dry.
Cables are raised and lowered into the tank by means of a cable
yoke, which consists of an 11-foot length of 4 by 6 inch scantling,
with three hooks on the lower side and a ring on the upper side at
the center for hoisting. The lower hooks, which are secured to the
scantling by a bolt and ring, hook into the lashing on the cable.
Washers are placed under the bolt heads to prevent their slipping
through the holes.
Swinging or traveling cranes with triplex blocks are used for lowering
and raising cable and yoke.
The coils of single-conductor cable are carried aboard the planter,
to the aft deck, by the cable detail, or they may be lowered onto the
deck by means of the cable yoke and a derrick on the wharf. The cable
for mine No. 1 is placed on the starboard side of the aft deck and its
mine-cap end is carried forward on the cable racks close to the mines.
The other cables, Nos. 2 to 9, inclusive, are placed in succession on
the starboard side in the same manner. The cables, Nos. 19 to 10 are
placed in succession on the port side, with No. 19 at the bottom. The
coils on each side are placed on top of each other. The cable should be
removed from the racks when its corresponding mine is being prepared
for planting.
At the same time the other apparatus and appliances are carried aboard
and placed forward, the proper supply on each side. The anchors are
placed as convenient to the forward davits as possible.
Finally, the loaded mines are put aboard. If they contain dynamite they
should be protected from the direct rays of the sun by being covered
with a paulin.
=Preparing mines for planting.=—The detail on each side of the planter
prepares a mine on its own side. The loading wire from the mine is
cut to the proper length, a water-tight joint is made with the single
conductor of the corresponding cable, and the Turk’s-head is clamped
in place, care being exercised that no part of the leading-in wire is
caught under the clamp. The cable is lashed with soft-drawn copper wire
or secured by clips to the bails just above the ring.
The proper mooring rope is now shackled at one end to an anchor, at the
other end to the mine, and is lashed to the mine cable with soft-drawn
copper wire at every 5 feet. If automatic anchors be used, the mooring
rope is shackled to the mine after the anchor and mine are swung
outboard; the lashing of the cable to the mooring rope is omitted.
A rope for raising the mine is cut to the length of 80 feet plus the
depth of water. One end is attached to the anchor by an anchor knot or
bowline, the other to the mine cable by two half hitches and a seizing
of soft-drawn copper wire. It should not be secured at other points.
The mine buoys have attached to them 60 feet of ½-inch rope, which is
marked at every 5 feet. The free end is slipped through the maneuvering
ring of the mine and tied to the buoy.
When planting mines for practice, marline may be used to seize the
raising rope to the cable and to lash the cable to the bail and mooring
rope.
A mousing must be put around the upper hook of the differential block
to prevent the block from jumping off the hook when the mine or anchor
is tripped. The tripping hook of the differential block on the forward
davit is attached to the anchor and it is hoisted and swung outboard
clear of the rail. The mine is similarly slung from the after davit by
its maneuvering ring or by a rope sling through the latter. Both mine
and anchor are lowered as close to the water as conditions will permit.
A heaving line is bent onto the free end of the mine cable, generally
by means of a clove hitch and two half hitches.
The aft detail now removes or cuts the rope lashings of the coil of the
corresponding mine cable. A detail sees that the cable and raising rope
are held on the gunwale ready for planting. These should not be allowed
to trail in the water. A man stands near the mine davit ready to throw
the mine buoy clear of the planter when the mine is tripped. (Fig. 13
shows the mine and anchor slung for planting and fig. 14 shows the
relative position of the various parts in the water. In these figures
the cable should be shown as lashed to the mooring rope.)
=The distribution box boat= should precede the planter to the mine
field. The distribution box buoy, to which the anchor rope is fastened
by a bowline, to the bight of which the raising rope is secured, is
taken aboard at the bow, if the tide is coming in toward the box, and
the anchor rope is made fast. The distribution box is then raised by
its raising rope and secured in the stern. The boat is thus anchored
fore-and-aft, perpendicular to the line of mines, with its bow pointed
toward the position of the center mine of the group. If the tide is
running out from the box, the buoy should be taken in at the stern, the
boat being held in position by the raising rope of the distribution box
and then by the multiple cable. The anchor rope is finally made fast in
the bow. During the planting of mines a man should always stand ready
to slacken away on the anchor rope if necessary.
[Illustration: FIG. 13.—MINE READY FOR PLANTING.]
[Illustration: FIG. 14.—MINE PLANTED.]
If the buoy for the distribution box is not in place, the cable must be
underrun, either from shore or from a buoy planted for this purpose.
This is done preferably with a yawl. The cable is raised, taken aboard,
and placed over a roller or rowlock in the stern. The cable is then
pulled in over the stern and lowered over a roller or rowlock in the
bow. If the planter is to underrun cable, a cathead is put in place
and a snatch block is lowered by a raising rope secured to a hoisting
windlass. The cable is placed in the snatch block and the planter moves
forward slowly. When it is desired to transfer the cable to a small
boat the snatch block is lowered into the boat and the cable removed.
After the distribution box boat has secured the box in position,
the lid is removed and the cable is tested as prescribed on page
44. A signal is then raised to indicate to the planter that the
distribution box boat is ready for the planting of mines.
=Planting the mines.=—If there be a strong tide, the mines should, if
possible, be planted at such time that the planter, in going out toward
the line of mines, moves against the tide.
The planter moves out and passes close to the distribution box boat,
with the latter to port. As it passes slowly by, a heaving line is
thrown by a man forward of the beam to the distribution box boat, whose
party immediately hauls in the mine cable, bends on another heaving
line, and lashes the cable to the boat. It is desirable to have a
second heaving line ready in case the first one fails. If the water be
rough the cable end is passed to the boat by a launch.
The planter moves forward to the position to be occupied by mine No.
10. If automatic anchors are used, the distance weight is lowered at
the command “Lower weight,” given after the cable is secured in the
distribution box boat. As the planter approaches this position the
command “Get ready” is given. As the forward davit comes abreast of the
position of No. 10 mine, the officer in charge of the planting commands
“Let go”; the tripping hook of the mine is released first and that of
the anchor immediately thereafter. The mine buoy, cable, and raising
rope are then thrown overboard.
(Caution.—The men operating the tripping hooks must be very careful
that they stand back of all cable and rope, so that they may not be
caught. All others must stand clear.)
The planter turns so that the stern will be thrown away from the
planted mine. When the stern is clear of the mine buoy “All clear” is
signaled from the stern.
The planter then executes a sweeping circle to starboard, passes to
the rear, and comes up with the distribution box boat to starboard. As
it moves by, the free end of mine cable No. 9 is passed to the boat
and secured as before. The planter moves ahead to a point 100 feet to
the left of mine No. 10, and as it crosses the line, plants mine No.
9, swings off to port, circles and comes up from the rear with the
distribution box to port, and so on alternately until all the mines are
planted.
As soon as a mine is dropped the detail for that side of the planter
prepares another for planting. There is ample time to do this while the
vessel is turning and planting the other mine.
Two small boats, one on each side of the line, work as follows: As soon
as a mine is dropped the boat on the corresponding side moves to it,
picks up the buoy, pulls the rope taut, notes the submergence of the
mine, transmits the data to the planter, and holds up an oar or a flag
in prolongation of the buoy rope. The observers at the ends of the base
line take observations on this marker and are thus able to plot the
position of the mine accurately. This process is repeated for each mine.
These boats also serve as guides to the planter in dropping mines by
holding on to their buoys until the adjacent mines are planted. With
automatic anchors the line may not be marked otherwise than in this
manner.
After the mine is dropped, the members of the distribution box boat
party remove the lashing from the cable, insert the Turk’s-head in the
proper slot, make a temporary joint between it and the corresponding
conductor of the multiple cable, and telephone to the casemate
operator. The latter opens all the power switches on the corresponding
operating board, closes switch No. 7 up (this throws D. C. power on
the mil-ammeter lead), and then plugs in on the upper jaw of the
power switch of the mine under test. If the D. C. voltage be 110, the
mil-ammeter should read about 40 mil-amperes; if the voltage be 80, the
reading should be about 30. If this test be satisfactory, the joint is
made permanent.
For the last mine the telephones are removed from the corresponding
conductor, a temporary joint is made in the boat, and the test made
as above. By arrangement with the casemate operator the mine is left
on two minutes for test. At the end of this time the joint is opened
and the telephones put back. If the casemate operator reports the test
satisfactory, the telephones are again removed and a permanent joint is
made.
When the last joint has been made, the distribution box is closed and
the raising rope fastened to its lid. The box is then lowered. This is
done by the distribution box boat if it is provided with the necessary
davit and power, otherwise it is done by the planter. Generally the
anchor rope is made fast to a buoy by a bowline, and the raising rope
of the distribution box is secured to the bight of the bowline.
After the distribution box is lowered all buoys are removed except that
for the box, and such others as it may be desired to place for marking
the ends of lines. The marking boats may remove the mine buoys as they
work, provided they are notified from the mine commander’s station that
proper observations for plotting have been obtained. Such notification
is usually sent by telephone to the distribution box boat.
In time of war decoy buoys judiciously placed would be very useful in
deceiving the enemy.
CHAPTER VI.
TESTS OF MINES AND APPARATUS.
After the mines have been planted the following tests are made daily,
or more frequently if need be, the results being recorded carefully on
the form given at the end of the chapter. (Note: This applies also to
such test mines as may be kept planted for purposes of observation and
instruction.)
=Caution.=—If A. C. power be supplied from the casemate motor-generator,
there is no possibility of accidental firing of mines if the
motor-generator is not running; and when it is running the chance
is remote, since it would require the committing of three blunders.
However, the following precautions must be enforced rigidly:
(_a_) _Never start the motor-generator during the planting of mines nor
when any friendly vessels are in the neighborhood of the mine field._
(_b_) _Before starting the motor-generator for testing it, see that
all automatic switches are up, all firing switches open, and the A. C.
operating switch (No. 8 of the power panel) open._
1. =Test of the D. C. voltage.=—Plug in at the proper receptacle and
read the voltmeter.
2. =Test of the A. C. voltage.=—_Caution._—_First see that all
automatic switches are up, that the firing switches are open, and that
the A. C. operating switch No. 8 is open._
Close switch No. 4 up; close starting switch of motor-generator, and
when the latter has attained its full speed close switch No. 9 up; plug
in at the proper receptacle, and read the voltmeter. When the source of
power is the storage battery, the battery rheostat should be adjusted
until the A. C. voltage is 500 or above; when the casemate generator is
used, its field rheostat should be adjusted for the same purpose.
3. =Test of the mines.=—Leakage in mine circuits will be indicated
automatically by an increased brightness of the green lamp on the
signal block; an excessive leakage in any mine circuit may cause the
automatic switch to trip.
However, each mine should be tested separately, as follows:
With the D. C. on the D. C. busses of the power panel, close switch
7 up, open the power switch on the mine block of the mine circuit to
be tested, and put the M-AM “plug” on the upper point of the power
switch. If the automatic switch falls, adjust the solenoid or hold the
switch up while testing the circuit, otherwise the reading obtained
will be that of the red lamp and bell circuit. These operations put the
mil-ammeter and its protective lamp in series with the mine circuit.
The circuit is as follows: From the negative D. C. bus on the power
panel, to switch 7 closed up, through the mil-ammeter and its
protective lamp, to the terminal bar, to the M-AM lead, to the plug,
to the upper point of the power switch P, through the solenoid, to the
middle of the testing switch T, to the upper point of same, to the
upper point of the automatic switch, to the middle of same, to the mine
switch, through same, to the terminal bar, through the 19-conductor and
the single-conductor cables, to the mine transformer primary, to the
mine case, to ground, to the D. C. “earth” terminal on the power panel,
to switch 7, and to the positive D. C. bus on the power panel.
With from 80 to 110 volts these readings should normally be between 30
and 40 mil-amperes. A mine may be fired if the reading with 80 volts is
between 14 and 120 mil-amperes. These limits increase with the testing
voltage. If the mine tests within the firing limits, the solenoid
should be adjusted if the current is above its normal setting (0.075
amperes). If the test indicates that the mine can not be fired, the
mine switch should be opened.
4. =Test of the automatic switch, red lamp, and bell.=—Throw the D. C.
power on the busses of the operating board by closing switch 3 up. Open
the bell switch. Next close the testing switch down on the mine block
under test. The red lamp should glow and the corresponding automatic
switch trip. (For circuit see fig. 18.) Now close the bell switch,
throwing the bell in parallel with the red lamp; the bell should ring.
Next open the bell switch and repeat the test for each mine block in
turn.
5. =Test of the alternating circuit.=—This circuit is tested with D.
C., as follows: Connect the A. C. and D. C. jaws on the master block
with a jumper, open the power switches, close switches 3, 8, and 9 up
on the power panel. The green and white lamps of the operating board
under test should glow. A break or an excessive resistance in the
casemate grounds, or elsewhere in the circuit, will be indicated by the
lamps not glowing, or glowing dimly.
The circuit is as follows: From the negative D. C. bus on the power
panel, to switch 3, to the “operating board” terminal, to the D. C.
lead, to the D. C. post on the signal block, through the green lamp, to
the D. C. jaw on the master block, through the jumper, to the A. C. jaw
on the master block, through the white lamp and resistance in parallel,
to the A. C. post on the signal block, to the A. C. lead, to the A. C.
“operating board” terminal, to switch 8, to the A. C. bus, to switch
9, to the casemate transformer secondary, back to switch 9, to the
other A. C. bus, back to switch 8, to the A. C. earth, through ground,
to the D. C. earth, to switch 3, and to the positive D. C. bus on the
power panel. With this circuit on, remove the 90-ohm resistance in
parallel with the white lamp; the white lamp should glow more brightly,
indicating continuity of circuit through the resistance as well as the
white lamp.
It will be observed that the above test is for only a part of the A.
C. circuit. To test the firing switch and the lower contact of the
automatic switch, open switches 3, 8, and 9, close 7 up, remove the
jumper, put the M-AM “plug” on the A. C. jaw on the master block, close
the firing switch, and trip in turn each automatic switch by raising
the corresponding knob on the solenoid and observe the reading of the
mil-ammeter. Close each automatic switch up before tripping the next
one.
The mil-ammeter reading should be from 30 to 40 mil-amperes, indicating
a circuit through the firing switch and the automatic switch. The
circuit is as follows: From the negative D. C. bus on the power panel,
to switch 7 closed up, through the mil-ammeter and its protective lamp,
to the operating board terminal, to the M-AM lead, to the “plug,” to
the A. C. jaw on the master block, through the firing switch F. S.,
to the A. C. bus on the operating board, to the lower point of the
automatic switch which was tripped, to the middle of same, to the mine
switch, through the same, to the terminal bar, through the 19-conductor
and the single-conductor cables, to the mine transformer primary, to
the mine case, to ground, to the D. C. “earth” post on the power panel,
to switch 7, to the positive D. C. bus on the power panel.
6. =Test of the delivery of the A. C. power to the operating
board.=—_See that all the automatic switches of the operating boards
are up and all the firing switches of the master blocks open._ Close
switches 4 and 9 up (or down) and 8 down; close the testing switch
T. S. on the master block. The white lamp should glow and the A. C.
bus-bar voltage should drop appreciably.
The circuit is as follows: From the A. C. bus on the power panel,
to the lower right terminal of switch 8, to the “operating board”
terminal, to the A. C. lead, to the A. C. post on the signal block, to
the white lamp and the resistance in parallel, to the A. C. jaw on the
master block, to the testing switch T. S., to the “earth” post on the
signal block, to the earth lead, to the D. C. earth, through earth, to
the A. C. earth terminal on the power panel, through the choke coil, to
switch 8, to the other A. C. bus on the power panel.
In this test it is imperative to see that all the automatic switches
are _up_ and all the firing switches are _open_.
7. =Test of the power.=—Insert two fuses in multiple across the fuse
leads from the power panel. Put the fuses in a place prepared for the
purpose outside of the casemate, so that there will be no danger from
flying fragments. With all the switches on the power panel open, all
the automatic switches up, and the firing switches on the master blocks
open, energize the D. C. busses of the power panel, close switch No.
4 up (or down), and close the starting switch; close switch No. 9 up
(or down); close switch No. 12 up (which connects the mine transformer
secondary to the fuses); and, finally, close switch No. 11 up (which
throws the A. C. power on the mine transformer primary). The fuses
should explode.
If fuses are not available for this test, a low-voltage lamp or a short
piece of fine wire may be heated to incandescence.
8. =Test of grounds.=—(_a_) “Separate” grounds shall be made for the A.
C. power and the D. C. power on the power panel. The word “separate” as
here used means actual connection to earth without metallic contact of
the earth leads. A convenient method of making a ground is to connect
to the armor of a cable running to salt water, a bond being made in
case the armor of the cable in the casemate does not reach water before
a joint is made. If a cable armor is used for one ground, the other
ground lead must go to earth without contact with that armor. This may
be accomplished by using the conductors of a cable, the ends of which
are grounded to an earth plate in salt water.
(_b_) Neither of the grounds made should have more than 10 ohms
resistance. To verify this, tests should be made as follows:
Close the double circuit breaker; close switch 7 up and plug the
extension cord of the mil-ammeter lead of the power panel on the upper
left-hand terminal of switch 8, the mil-ammeter extension cords for the
operating boards being disconnected.
Ascertain the voltage across the mil-ammeter and lamp, and across the
bus bars. Read the mil-ammeter.
From these readings the combined resistance of the grounds can be
determined.
A table or chart may be prepared giving the resistances for various
testing voltages and mil-ammeter readings.
[Illustration: _Form for record of tests, Group No._]
CHAPTER VII.
TAKING UP MINES.
Mines should be raised in the reverse order from that in which they
were planted if the conditions of wind and tide are favorable. With
a cross tide or a strong cross wind, the mines should be taken up in
regular order from one side so that the planter will not drift onto the
mine field.
A yawl or launch takes position at the outer mine on each side. The
mine-buoy rope is hauled up taut in order to locate the exact position
of the mine. The boat holds fast until directed from the planter to let
go. While the anchor and mine are being taken aboard the planter, the
boat remains off the bow to render assistance if necessary.
The distribution box is raised by underrunning the multiple cable, or
by means of its raising rope if the buoy has not been removed. The box
is taken aboard the distribution box boat, the lid is removed, and the
mine cables, in turn, disconnected from the multiple cable. The planter
passes close to the distribution box boat. A heaving line which has
been made fast to the outer mine cable is thrown to the bow of the
planter. If this should fail, a man throws a heaving line from the bow
of the planter. If the conditions be unfavorable for passing a heaving
line, a launch may carry the line to the planter. The heaving line
attached to the cable is hauled aboard and the cable placed over the
cathead. The planter then proceeds to underrun the cable. If the water
be shallow, the cable is carried through a snatchblock to the aft deck
and coiled, or it may be carried to a cable-reel forward. If the water
be deep, or the cable can not be raised easily by hand, it is carried
through a snatchblock to the drum of a hoisting windlass and coiled
as before mentioned. (If placed on a cable-reel, the ends should be
insulated and tagged. Mine cables Nos. 1 to 9 should be placed on one
reel and Nos. 10 to 19 on another, both reels being carefully marked.)
When the raising rope is reached, it is carried with the cable over the
cathead. The bight of the rope is hauled in quickly, carried through a
snatchblock, and a few turns taken on the drum of a hoisting windlass.
The rope is untied from the cable as soon as possible. If there be
danger of losing the rope, it should be made fast at once. The anchor
is raised until within a few feet of the cathead. It is lifted aboard
by means of the boom, or by the differential block on the anchor davit.
At the same time a man is sent over the side of the planter near the
mine davit (a rope ladder may be used) to secure the hook of the
differential block in the sling attached to the maneuvering ring of
the mine when it comes to the surface. To bring the mine to the proper
place to accomplish this, a man should be ready to secure the mine-buoy
rope with a boathook; other men should be ready to pull the mine
forward, if necessary, by means of the cable. The mine is raised by
the differential block of the mine davit. It may be raised by the boom
and fall; or by means of a tackle secured to the mine davit, the end
of the rope running through a snatchblock to the drum of a windlass.
The distance weight of the automatic anchor may be raised by the fall
of the boom, or by an improvised tackle. An eye should be made in the
distance rope for this purpose.
If the end of the cable is lost, the work may proceed as follows: The
planter moves out to the mine if its buoy is still in place. A sling
made of raising rope may be thrown over the mine, or two raising
ropes are tied together and one end is passed to a launch which moves
around the mine and brings the end back to the planter. Both ends are
placed over the cathead, through a snatchblock, and around the drum
of a hoisting windlass. The mine is hoisted, bail up, until near the
cathead. It can then be transferred to the anchor davit. The mine cable
is pulled in until the raising rope is reached. The work then proceeds
as before. If the mine buoy has been removed, a yawl may drag for the
cable with a grappling iron. If the raising rope should break or be
lost, the mine may be raised as mentioned above, except that the mine
must be transferred to the fall of the boom and the anchor raised by
means of its mooring rope, or the mine may be transferred to the anchor
davit, as before, and a raising rope made fast to the mooring rope of
the anchor and carried over the cathead, through a snatchblock, to a
hoisting windlass. The mine, as soon as the strain is taken up by the
raising rope, is unshackled. The anchor is then taken aboard in the
usual manner.
As soon as the mines are taken aboard they are disconnected, the
ropes are coiled, and all matériel placed so as not to interfere with
subsequent work. As soon as the matériel is unloaded on the wharf it
should be cleaned thoroughly and stored.
If the multiple cable is to be left down, the ends of the conductors
are insulated, the lid replaced, and the box lowered by means of a
raising rope, the end of which is made fast to the bight of the bowline
of the anchor rope.
If the multiple cable is to be taken up, the end is passed to the
planter, run through a large snatchblock on the bow, and coiled on a
cable-reel as it is raised. Whenever a multiple cable is coiled on a
reel it should be secured so that both ends will be available for test
when the cable is stored.
=Unloading mines.=—Should any of the mines be loaded with dynamite
the utmost care must be exercised in unloading them. (See p. 76.)
Some contrivance must be rigged up so that the first few turns of the
compound plug may be accomplished by the operator at a distance, as
there is great liability of explosion, due to leakage of nitroglycerin
into the screw threads. After the compound plug is removed the
precautions to be observed are given in Appendix No. 1.
Should the mine be loaded with guncotton or trotol, no danger is to
be apprehended in unloading; the usual precautions in handling high
explosives must, of course, be observed.
CHAPTER VIII.
THE MINE COMMAND.
A mine command consists of the mine groups and rapid-fire batteries
specifically assigned for their protection, which are controlled by a
single individual.
The mine commander is in direct command of the elements of the mine
defense during drill and action. His station is at the mine primary,
which is connected by telephone to the battle commander’s station.
He bears the same relation to the battle commander as do the fire
commanders, and his duties are similar to theirs.
The mine commander is responsible that the property officer requests
for all matériel necessary to carry out the approved scheme for mining
the harbor; he is responsible, further, that the property officer keeps
this matériel in proper condition for immediate service.
The senior company officer of the mine command is the property officer
and obtains from the district artillery engineer all necessary matériel
for the mine defense. He has direct charge of the storeroom, cable
tanks, loading room, wharves, boats, boathouses, and mining casemate.
The personnel of the mine companies are subject to his orders for
service in connection with caring for and maintaining this matériel.
The officers of the companies of the mine command will be assigned by
the mine commander in accordance with their special fitness.
The enlisted personnel of mine companies will be divided into sections,
detachments, and details, as follows:
(_a_) Fire-control and power section.
(_b_) Planting and loading section.
(_c_) Gun and ammunition sections.
(_d_) Reserve section.
These will be subdivided as follows:
(_a_) Fire-control and power section:
1. Observing detachment—
_a._ M′ detail.
_b._ M″ detail.
_c._ M‴ detail.
2. Plotting detachment—
_a._ Plotting board detail.
_b._ Communication detail.
3. Power detachment—
_a._ Casemate detail.
_b._ Searchlight detail.
(_b_) Planting and loading section:
1. Planting detachment—
_a._ Planter detail.
_b._ Small-boat details.
2. Loading detachment—
_a._ Loading room detail.
_b._ Explosive detail.
_c._ Cable detail.
(_c_) Gun and ammunition section:
_a._ Gun details.
_b._ Projectile detail.
_c._ Powder detail.
(_d_) Reserve section: As required.
In each company assigned to the mine defense, a permanent manning table
will be made out and always kept up to date. A copy of this manning
table will be posted in the mine commander’s station. In addition,
a copy of such portion of this table as pertains to any particular
station will be posted therein.
=Plotting board.=—The plotting board differs from that used for guns in
that it requires no gun arm and corresponding attachments. Furthermore,
since the distance at which mines are planted will in general be small,
the board, without any change in size, may be used with a much larger
scale, say, 150 yards or even 100 yards to the inch, and the arms
graduated accordingly.
The stations are manned during the planting of mines and the location
of distribution boxes, as well as during operations.
[Illustration: FIG. 15.—PREDICTION RULER.]
For planting buoys signals may be made from the primary, from the
secondary, or from both, as conditions warrant.
Observations are taken on each mine as planted, the data are recorded,
and the position of each mine is plotted.
During operations vessels may be tracked by the vertical or by the
horizontal method of position finding. If by the former, either the
command “Fire” may be given when the vessel is on the cross wires of
the instrument set at the range and azimuth of a mine, or the time from
any point to the instant of passing over a mine may be found by means
of the prediction ruler (see below) and the command “Fire” be given at
the proper instant, as indicated by the stop watch. For the horizontal
base system the latter method must be used.
=Prediction ruler= (fig. 15).—This is a 10-inch white celluloid slide
rule with a beveled edge. The slide is graduated in “Yards in 15
seconds,” and on the left and right of the runway, respectively, are
a “Fire at time” and a “Yards to mine” scales. The beveled edge is
graduated from the center outward in both directions with “0” in the
center of the scale and “500” at either end. Each 50 and 100 has its
value engraved on the scale.
_Method of using._—Plot the position of the target for a 15-second
interval. With the beveled edge find the distance the target has
passed over during the interval; and also determine the distance
from the last plotted position to the mine. Move the slide until the
graduation corresponding to the “Yards in 15 seconds” is opposite the
graduation corresponding to the “Yards to mine,” and read the “Fire at
time” scale opposite the arrow on the slide. The reading will be the
number of seconds from the last plotted position to the mine which the
vessel is approaching. A stop watch is started at the time of the last
observation on the target, and at the expiration of the time obtained
from the “Fire at time” scale the command “Fire” may be given.
=Observation firing.=—The mine commander’s station is connected with
the casemate by telephone. At the command “Observation firing” sent
to the casemate, the casemate operator will see _that all automatic
switches are up, and that all firing switches are open_. He will then
close the double circuit breaker, and switches 4 and 9, which will
energize the busses of the power panel. At the command “Group ——, mine
——,” the operator will close switches 3 and 8 on the power panel,
thereby putting both D. C. and A. C. power on the operating boards. At
the command “Ready,” given from the mine commander’s station at the
proper time, the operator will stand ready to trip the corresponding
automatic switch. At the command “Fire” the automatic switch will be
tripped and the firing switch will be closed. Without delay, after the
mine is fired, the firing switch and the power switch will be opened,
the automatic switch closed up, and the mine switch opened on the mine
block.
If the mine is struck before the command “Fire” is given, the automatic
switch will fall, and the mine should be fired by closing the firing
switch unless there are positive orders to the contrary.
=Contact firing.=—For contact firing the mine system will be set so
that a signal will be sent to the casemate and the mine will be fired
when the latter is struck by a passing vessel. This is the normal
method of firing in actual service. At the command “Contact firing,”
which may be given for all groups, or certain individual ones, the
casemate operator will see _that all automatic switches are up, power
and mine switches closed, and firing switches open_; he will then close
the double circuit breaker, and switches 4, 9, 3, and 8 on the power
panel. This puts both D. C. and A. C. on the operating boards. He will
then close the firing switches on all the boards or on such as may have
been indicated. When a mine has been fired, the corresponding mine
block will be cut out.
If it is desired to delay the firing of a mine after being struck, the
command “Delayed contact firing” is given. The operations are the same
as for contact firing except that the firing switch is closed by the
operator a short time after the mine has been struck or when directed
to do so. After the mine has been fired the firing switch will be
opened, and the corresponding mine block will be cut out.
APPENDIX NO. 1.
EXPLOSIVES.
The latest adopted explosive for submarine mines is trinitrotoluol,
also called trotol. The commercial names for this explosive are trinol,
trotyl, and triton.
Wet guncotton is used extensively for submarine mines and in emergency
other commercial high explosives may be employed, preferably dynamite.
=Trotol= is a fine crystalline yellow powder, much resembling brown
sugar. It is manufactured by nitrating toluol. It is very insensitive
to shock or friction, insoluble in water, very stable in storage, and
very powerful when detonated. Its melting point is about 81° C., its
ignition point is about 197° C., its specific gravity in powdered form
is about 1.55; it has no dangerous chemical action on metals.
The priming charge is a fuse can full of crystalline trotol.
Trotol is supplied in wooden boxes doubly lined with wax paper, each
box containing about 50 pounds of explosive. The date of receipt
at the post and the name of the explosive shall be painted on each
box. The boxes should be stored in tiers with the marked end out,
the bottom tier resting on skids. The explosive is not dangerous to
handle, but the same care should be observed in storing and handling
as with other high explosives. It should be stored in a perfectly dry
place, preferably in a magazine. If it is impracticable to store in a
magazine, the explosive may be stored in the driest place available
where it is protected thoroughly from all fire risks. If from any cause
the boxes of explosive are wet and there is reasonable assurance that
the interior has become wet, a box should be selected and opened. If
the interior is wet, a full report of the circumstances shall be made
to the War Department. Boxes should be opened and the contents dried in
open air out of the direct rays of the sun.
Trotol may be stored with wet guncotton, explosive D, and dynamite.
Inspection at posts will be limited to seeing that the rules for
storage and care are strictly observed. Technical inspections will be
made, when required, by the Ordnance Department.
=Wet guncotton= in the form of compressed cakes is supplied in boxes
lined with zinc, the lid being screwed down upon a rubber gasket so
as to prevent the loss of water by evaporation. Each box contains 100
pounds of dry guncotton. In the lid is a small flush cap which screws
down upon a rubber washer and closes a tube communicating with the
interior of the box. Upon each box there is painted by the manufacturer
the net and total weights. Shipping regulations require that guncotton
should be wet with water so that the water is 20 per cent of the weight
of guncotton and water. This is too much water for full detonation, and
the guncotton upon receipt at a post should be dried out so that the
weight of water is from 12 to 15 per cent of that of the dry guncotton.
The guncotton is dried by opening the box and pyramiding the guncotton
on the lid and in the box so that there will be free circulation of air
between the cakes. The use of an electric fan in this connection will
ordinarily materially facilitate the operation. By weighing pilot cakes
it may be determined when the proper amount of water has evaporated.
The guncotton is then repacked, lid screwed down, and the weight
chalked upon the end of the box. The guncotton should be placed while
drying so that it is not in the sunlight and should be handled with
clean cotton or rubber gloves.
In addition to the regular monthly inspection the boxes are reweighed
quarterly under the supervision of the officer responsible for
submarine mine explosive, and the gross weight so found chalked upon
the end. Should any box show any decided decrease in weight the screw
cap in the lid is removed, enough fresh water, preferably distilled or
rain water, added to bring it up to its original weight, and the screw
cap replaced.
Magazines in which guncotton is stored should not be allowed to attain
a temperature as high as 100° F. for any length of time.
Guncotton which is kept wet may deteriorate after long storage, but
will not become dangerous.
Wet guncotton can not be ignited by a flame, but gradually smoulders
away as the outer portions in contact with the flame become dried.
A brownish or reddish shade is sometimes seen in cakes of guncotton.
This is due to the presence of iron in the wash water and does not
indicate decomposition.
When storing guncotton in the magazine the piles of boxes should be
made so as to give free circulation of air and the greatest convenience
in handling consistent with the capacity of the magazine.
In the event of damage to any case, which may cause loss of water by
evaporation, the contents shall be removed at once, repacked in a
guncotton box which has been washed with soda solution, the proper
amount of water added to the contents, and the box closed. The gross
weight shall be marked on the case. In repacking avoid as much as
possible handling the cakes with the bare hands. This is for the
protection of the guncotton from oil or acid of any kind. Clean cotton
or rubber gloves are suitable covering for the hands when engaged on
this work.
If for any reason the cases are subjected to dampness sufficient to
cause unusual deterioration of the cases, they should be removed from
the magazine and dried, out of the direct rays of the sun.
Guncotton containing 12 or 15 per cent of moisture may be stored with
explosive D, trotol, and dynamite, but never with dry guncotton.
Empty cases, before being placed in storage, must be washed thoroughly
to remove all traces of guncotton.
For a charge of wet guncotton, the priming charge is dry guncotton.
This may be either of crumbled guncotton or cakes made to fit the fuse
can. The compressed primer cakes are supplied wet and bored with holes
to receive the fuses and the loading wire.
Should the supply of guncotton primers become exhausted fresh ones may
be prepared as follows: Two blocks of soft pine are used, one 3 inches
square, the other circular and 2.9 inches in diameter. A cake of wet
guncotton is clamped between these blocks. Using a fine joiners’ saw
and the circular block as a gauge, a cylinder is sawed from the cake.
The cylinder is then smoothed down with a rasp. Four of these are
prepared for each charge and in each one of them a hole about ⁹/₁₆ inch
in diameter is bored. While boring the hole the cake must be tightly
clamped between two pine blocks to prevent it from splitting; to insure
that all the holes will be in alignment it is advisable that the upper
wooden block be provided with a ⁹/₁₆-inch hole and be thick enough to
enable this hole to serve as a guide for the bit. The boring is done
with the ordinary bit, which must be sharp, so as to cut clean. _It is
not safe to saw or bore a dry guncotton cake._
It is essential that the guncotton primer be thoroughly dry. The
primers may be dried by exposure to the air or by means of drying ovens
supplied especially for the purpose. To air-dry a primer, it is placed
on edge upon a shelf of wire gauze or netting which is hung up indoors
where there is a free circulation of dry warm air. Drying should
continue until weighings on two successive days show no appreciable
loss. This may require a week or more.
In drying with an oven the cakes are laid on edge on the shelves
and the temperature of the oven is kept at about 100° F.; it should
not exceed 104° F. The heat is provided by means of a bank of lamps
placed under the hood and the current of warm air regulated by the
size of the lamp bank and the openings in the top of the oven. Under
no circumstances must an open flame be used as a source of heat. The
drying in this case also is continued until successive weighings of
samples show no appreciable loss.
Whenever it is necessary to dry more than 50 pounds of guncotton
primers for immediate use the guncotton should be placed in the drying
oven and exposed to the action of an electric fan placed about 4 feet
in front of the open door until the moisture content is reduced to
about 6 per cent, when the drying should be completed by the use of the
bank of lamps as described in the preceding paragraph.
In each case, to test the dryness of the primers, take a cake and split
it in four or five pieces and detonate each separately with a fuse.
It has been determined that about 5 per cent of water is the maximum
content for unconfined guncotton capable of detonation by a Du Pont No.
30 fuse.
Priming charges are not to be prepared until just previous to the time
they are to be used in loading. When the primers have been dried, they
should be kept in well-sealed jars unless they are to be used very soon
after drying, in which case they will be stored in assembled fuse cans;
when thus stored the assembled fuse cans should be kept in a cool, dry,
and secure room away from other explosives. If, however, the primers
are to be stored for any length of time, two strips of blue litmus
paper are inserted between the cakes, which are inspected from time to
time. If the litmus paper shows decided redness, it should be removed
and fresh strips inserted. If these strips turn red in a few hours,
the primers should be thoroughly wet with fresh water. In general, the
period of storage will be short and no particular examination of the
dry guncotton will be required.
Dry guncotton should be handled as little as possible, to prevent
crumbling and scattering of guncotton dust. Finely divided guncotton is
difficult to remove by brushing and if allowed to collect about a room
may give serious trouble by flashing should a portion become ignited.
This dust may be removed with a damp sponge or cloth.
Dry guncotton which is not used as contemplated shall be rewet with the
proper amount of water and repacked.
Samples of each lot of guncotton issued to the service are preserved
in the laboratory of the Ordnance Department for chemical test. These
retained samples are subjected regularly to technical inspection and
test by that department to determine their condition as to stability.
This will insure the detection of lots that are deteriorating and
their removal from the posts or their destruction before they have
deteriorated to such an extent that they become dangerous.
=Dynamite.=—Dynamite cartridges are packed ordinarily in sawdust
in wooden boxes. Each cartridge is wrapped in paraffin paper. The
cartridges are arranged in the box so that when they are transported
all cartridges will lie on their sides and never on their ends. Usually
the amount of explosive in a single package will not exceed 50 pounds.
The boxes must never be allowed to stand so that the cartridges will be
vertical.
Like other nitroglycerin, dynamite freezes at about 40° F., and in
its frozen condition is, under ordinary circumstances, less liable
to explosion from detonation or percussion than when thawed, but
more susceptible to explosion by simple ignition. Should any of
the nitroglycerin be exuded, the dynamite cartridges are much more
sensitive to explosion by a blow.
It is important that dynamite cartridges be kept dry. If exposed to a
moist atmosphere, there is a tendency of the water, condensed from the
air on all exposed surfaces, to displace the nitroglycerin.
The cases should be raised from the floor on skids and the floor
underneath covered with clean sawdust. The sawdust should be removed
from time to time, the old sawdust being burned in the open air.
Rubber gloves should be worn in handling this explosive, or in the
absence of rubber gloves cover the hands with grease and wear cotton
gloves. This is for the protection of the skin from the injurious
effect of nitroglycerin.
Dynamite may be stored with wet guncotton, explosive D, and trotol.
Date of receipt at post shall be marked on each box.
The priming charge for dynamite is a pound of loose dynamite contained
in a small bag which fits easily into the fuse can. In filling the bag
rubber gloves must be worn. To insert the fuses the bag is opened and
the fuses embedded in the explosive, the choke being tied around the
fuse wires.
At the monthly inspection all boxes shall be examined to see if they
are dry. If not dry, all shall be exposed to the dry air out of the
direct rays of the sun.
The principal source of danger from dynamite is in the exudation of
the nitroglycerin. Exudation is indicated by the presence of small
white, oily, lustrous globules of liquid, either among the particles
of dynamite or on the packages. If such globules are discovered, they
may be identified positively as nitroglycerin by absorbing a drop in a
piece of unglazed paper, which should be placed on an anvil or other
piece of metal, and striking it a sharp blow with a hammer. If it be
nitroglycerin, an explosion will occur. Another test is to set fire
to the paper, and if the liquid be nitroglycerin it will burn with a
crackling noise and a greenish-yellow flame.
If exuded nitroglycerin has stained floors or other material not
readily destroyed, the nitroglycerin may be decomposed and rendered
harmless by washing with “sulphur solution.” This solution may be
made by boiling 50 pounds of lime in a barrel of water and adding
powdered sulphur until the solution will take up no more. This will
require about 20 pounds of sulphur. The resulting bright orange-colored
solution should be filtered and only the filtrate used. A suitable
filter for this purpose is a piece of thin cheese-cloth. Sodium
carbonate may be used in the place of lime.
Dynamite may be destroyed by burning in small quantities at a time.
Slit the cartridge with a knife, spread out the contents over some
straw or shavings, and ignite carefully. Do not attempt to burn frozen
dynamite.
=Mine fuses.=—These are regular commercial electric fuses, extra
quality, and each contains about 25 grains of mercury fulminate. Fuses
are supplied in pasteboard boxes containing 50 each, pasteboard boxes
being shipped in suitable wooden boxes. They are supplied with long
leads which are cut to proper length when the mines are loaded. _They
must not be stored with other explosives._
=Loading mines.=—In loading mines the following precautions are
observed:
(_a_) Funnels are used to cover the screw threads.
(_b_) Trotol is poured through the funnels.
(_c_) Cakes of guncotton or packages of dynamite are
passed through the funnels by hand.
(_d_) The screw threads are wiped carefully before
the compound plug is inserted.
(_e_) Pieces of canvas or paulins should be spread upon the
floor of the loading room. After the loading has been
completed the canvas should be removed and thoroughly
cleaned. The floor of the loading room should be
scrubbed and all refuse destroyed.
=Unloading mines.=—Mines charged with trotol or wet guncotton may be
unloaded without danger; the compound plug being unscrewed, the cakes
of wet guncotton are removed by hand, repacked in the original boxes, a
little fresh water added, and the boxes closed. If loaded with trotol,
the charge is poured out into the boxes, which are then closed. Trotol
should be inspected carefully when removed from the case, and if there
is indication that any of it has undergone a change while the mine was
loaded, a report should be made to the War Department.
In unloading mines charged with dynamite too many precautions can
not be taken. The mine should be held either in an opening in a raft
or behind an earthen traverse and the compound plug removed by some
arrangement which may be operated from a safe distance. If the mine has
been planted for some time the recovered dynamite is usually destroyed.
Sometimes the interior of the mine case may be found coated with an
extremely thin film of exuded nitroglycerin. This film may be destroyed
by filling and thoroughly rinsing the case with “sulphur solution.”
APPENDIX NO. 2.
THE HORNSBY-AKROYD OIL ENGINE AND GENERATOR.
(See also Artillery Notes, No. 12.)
=The engine.=—This is a horizontal, single-acting, single-cylinder
kerosene engine, having a flyball governor and operating on a
four-stroke cycle. This cycle consists in turn of the explosion on the
first outstroke, the expulsion of the products of the explosion on the
following instroke, the intake into the cylinder of a mixture of air
and oil vapor on the following outstroke, and the compression of this
explosive mixture on the next instroke. This cycle therefore requires
two complete revolutions of the crank shaft for one complete set of
operations.
On one side of the cylinder near the closed end is a valve box
containing two valves, the air-inlet valve and the exhaust valve. The
air-inlet and the exhaust valves are actuated by separate levers, each
lever being moved by a cam mounted on a horizontal shaft, driven by
the crank shaft through worm gearing. This horizontal shaft makes but
one revolution while the crank shaft makes two; thus the air-inlet and
the exhaust valves are each opened once every two revolutions of the
flywheel.
At the back of the cylinder, in prolongation of its axis, is a
cast-iron box called the vaporizer, which is always open to the
cylinder. Before starting the engine this vaporizer must be heated by
an external lamp, so that it will vaporize the oil when it is first
pumped into it. After the engine has started running, the lamp is no
longer required, as the vaporizer is kept at a sufficient heat by the
internal explosions.
A small oil pump, worked by the air-valve lever, draws oil from the
oil tank under the engine and forces it into the vaporizer at the
proper time. The oil, on its way from the pump to the vaporizer, passes
through a valve box attached to the vaporizer; this valve box has two
valves in it, a horizontal one, kept closed by a spring which the oil
forces open as it goes into the vaporizer; the other, a vertical one,
also kept closed by a spring. Should the engine run too fast, the
governor opens this latter valve and allows some of the oil to flow
back to the oil tank through the waste pipe. This valve can also be
opened by turning the little regulating handle, which will stop the
supply of oil to the vaporizer and thus stop the engine.
INSTRUCTIONS FOR WORKING.
=Frosty weather.=—If there is danger of freezing, on shutting down
drain the water from the circulating pipes and cylinder jacket, and
valve box if water-jacketed; otherwise they may burst or crack.
=Caution.=—Before starting, see that the cocks which admit water to
the water jacket of the vaporizer valve box are open; that the cock on
the main water pipe from the bottom of the water tank is open; that
the water in the tank is above the upper circulating pipe; that the
drain cock is closed; and that the oil tank is filled with kerosene.
_Gasoline must not be used with this engine._
=Heating the vaporizer.=—Open the relief cock on top of the engine
cylinder. Place the lamp on the stand under the vaporizer; fill the
lamp with oil by means of the filling pipe till the oil is 1 inch below
the pipe; and put a piece of wick into the cups which are formed around
the pipes. These wicks, which should consist of a piece of ordinary
asbestos packing, will last for several weeks. Place the lid of the
vaporizer cover crosswise on the cover to allow the escape of heated
gas and air.
A little alcohol or kerosene should be poured into the cup under the
coil and lighted. The cups may be filled with kerosene by closing the
air-escape valve and working the air pump. The pressure forces oil out
through the vapor nozzle and it will run down into the cups. When this
is nearly burned out pump up the reservoir with air by the air pump.
Oil will issue from the small nozzle and give a clear flame. When it is
desired to stop the lamp, turn the thumbscrew on the reservoir filling
nozzle to let the air out. Should the nozzle become choked it should be
cleaned with the small needles for that purpose.
The heating of the vaporizer is one of the most important things to be
attended to, and care must be taken that it is hot enough at starting.
The attendant must see that the lamp is burning properly and that a
good clear flame is given off for from 5 to 10 minutes, according to
the size of the engine. If, however, the lamp is burning badly, it may
take longer to become heated sufficiently. It is important that this
should be carefully attended to, for though the engine may start, if
the vaporizer is not as hot as it should be the engine will run badly
and perhaps soon stop altogether. Failures of engines to run properly
can in most cases be traced to this source.
No time should be lost in starting the engine after the vaporizer has
been sufficiently heated, as the engine may not run satisfactorily if
the vaporizer is allowed to cool after heating it. The lamp should be
left burning a few minutes after starting.
=Oiling the engine.=—Oiling the engine should always be done during the
heating-up of the vaporizer.
See that the oil cups on the two main crank shaft bearings are fitted
with proper wicks and filled with oil. Adjust the lubricator on the
large end of the connecting-rod and oil the small end which is inside
the piston.
Oil also the following: The bearings on the horizontal shaft and the
skew gearing, the rollers at the ends of the valve levers and their
pins, the pins on which the levers rock, the governor spindles and
joints and the bevel wheels which drive the same, and the joints that
connect the governor to the vertical valve of the overflow. For such
bearings none but the best engine oil should be used.
It is necessary that a suitable oil should be used for lubricating the
cylinder, and unless such an oil be used for this purpose the engine
may run badly and perhaps stop altogether. Under no circumstances
must a thick cylinder oil be used, and the oil must not be used over
again on the piston. Do not use ordinary lubricating oil. A high-grade
gas-engine oil especially suited to this engine should be used and the
piston should be kept flooded with it.
=Starting the engine.=—Throw the hand lever to “To start.” Turn the
small crutch-handle regulator Y to the position “Shut” and work the
pump lever up and down until oil is seen to pass the overflow freely.
Turn the regulator back to “Open,” work the pump lever up and down a
few strokes. Vapor should issue with some force from the relief cock
on the cylinder. This indicates sufficient heat. Close the relief
cock and pump a few strokes. Man the flywheel and start the flywheel
backward, using the weight of the body if necessary, bringing the
piston up against compression as sharply as possible, and then release
the wheel, when an explosion should take place and the engine start
forward. As soon as the engine has sufficient speed to carry it past
a full compression, throw the lever to “To work.” When full speed is
obtained, cut down the pump stroke to correspond to the load, open the
oil feeders, and go over the engine carefully, seeing that the cylinder
oil feed is working.
=Oil pump.=—When the cylinder is working at its full power the distance
between the round flanges on the pump plunger should be such that the
hand gauge (supplied with the engine, and to be found in the tool box)
will allow the part stamped “1” just to fit in between the flanges;
if at any time the positions of these flanges be altered they can be
readjusted to this gauge. The other lengths on the hand gauge are
useful for adjusting the pump to economize oil. When running on a
medium load, use length marked 2; on a light load, use length marked 3.
See that the pump packing is not too tight.
=Running the engine light.=—When the engine is to run light—that is,
with no load or with a light load—it is best to alter the stroke of
the pump to the amount of oil that will keep the engine running.
This amount can be reduced so that the speed of the engine is a few
revolutions under the normal, which will allow the vaporizer to get a
small charge each time and keep it from cooling. The cock on the return
of the water circulating pipe may be nearly closed to keep the cylinder
warmer. These remarks do not apply when the load is intermittent and
the engine is running light for a short time only.
=Air-inlet and exhaust valves.=—See that the air-inlet and the exhaust
valves are always working properly and drop onto their seats. They can
at any time, if required, be made tight by grinding with a little flour
of emery and oil.
To insure a good seat to the valves when the stems are expanded by heat
the stems should clear the set-screws on the levers at least ¹/₁₆ inch
when the air and the exhaust levers are clear of the cams. A greater
clearance is undesirable, as it prevents the full opening of the valves.
If at any time the air-inlet or the exhaust valves appear to be opening
or closing at the wrong time, take off the nut on the end of the lay
shaft which holds the skew-wheel on and see that the chisel cuts on the
shaft are opposite to one another. The lay shaft is coned where the
skew wheel is fixed on and it is held on simply by friction, the nut
being tightened against it.
Should it at any time become necessary to take out the crank shaft,
always be sure that the skew-wheel gearing is put together so that the
tooth marked “0” on the crank shaft skew-wheel fits in between the two
teeth marked “0” on the oil-shaft skew-wheel.
=Vaporizer valve box and pipes attached to vaporizer.=—In this box
there are two valves. The vertical one is regulated by the governor,
and when the engine runs faster than its proper speed the governor
pushes it down, thus opening it and allowing some oil to return to the
oil tank. The horizontal valve in this box is a back-pressure valve.
If at any time this valve is not working properly, vapor will be seen
coming out of the overflow pipe; in this case the valve should be
examined. By screwing off the outside cap the tail of this valve can
be seen; if the valve is turned around a few times it will probably
dislodge any dirt that may be under it; if, however, this does not stop
the leakage the valve should be taken out for inspection.
If the horizontal valve and sleeves are taken out at any time, great
care must be taken in replacing them to use the same thickness of
jointing material as before or the distance the valve opens will be
altered.
See that the pipe from the pump to the vaporizer valve box is inclined
upward all the way from the pump. If this is not so, an air pocket will
be formed in which a certain amount of air will be compressed upon each
stroke of the pump. This will cause the oil to flow in slowly and not
suddenly as it should. If the oil tank be emptied of oil at any time,
air will get into the suction and delivery pipes of the pump and it
will take some time before the oil going through the pump and pipes
will be free of this air; for awhile thereafter, the engine will not
work properly, as the air, by being compressed as the pump works, will
interfere with oil being pumped in suddenly. It is best, if the oil
gets below the filter in the tank, to work the pump by hand for about
10 minutes, holding the relief valve (on the vaporizer box) so as to
get air well out of the pipes.
=To stop the engine.=—Turn the crutch-handle regulator to “Shut.” Close
the automatic lubricator. If it is desired to stop the engine for a
short time only, put the lamp back under the vaporizer to keep it hot.
=Setting the oil engine and the generator.=—The engine and generator
should be so located that the distance from center to center of pulleys
should be as nearly correct as possible when the generator is at the
middle point of the base rails, so that the proper tension of the belt
may be obtained within the limits of adjustment allowed by the rails.
The two pulleys should be accurately in line and the belt not too
tight. The generator base should rest on a wooden frame to separate it
from the concrete pier. Both engine and generator should be held firmly
in position by anchor bolts.
For the generator bearings a quantity of the best dynamo oil is
furnished; the commutator should be clean and smooth, and the brushes
should fit the surface. The commutator should be cleaned occasionally
with a little paraffin on canvas, and the brushes should be adjusted,
so that when running at full load no sparking occurs.
All electrical connections should be firmly made and kept thoroughly
clean. A cover should be kept on the generator when not in use. If the
machine be damp it should be allowed to dry before running at full load.
=NOTE.=—A few new installations have been
supplied with 5-kw. gasoline electric sets, and future
installations will be similarly equipped. Wherever
installed, pamphlets on the care and operation of the
gasoline sets have been furnished, containing full
instructions for the guidance of those concerned.
APPENDIX NO. 3.
THE STORAGE BATTERY.
(See pamphlets issued by the Electric Storage Battery Co.,
Philadelphia, Pa., on General Instructions for the Operation
and Care of the Chloride Accumulator.)
=Unpacking material.=—Great care should be taken in the unpacking and
subsequent handling of the various parts of the battery, as many of
them are easily broken or bent out of shape by rough handling.
Open the crates or packing boxes on the side marked “Up” and carefully
lift contents out; never slide them out by turning the crate on its
side.
Upon opening the crates and boxes, carefully count the contents of each
package, and check with the shipping list. A number of small parts will
usually be found in each shipment, and care should be taken to examine
the packing materials to determine that no parts have been overlooked.
Immediately upon opening the crates the materials should be carefully
examined for breakage. Cracked jars, whether of glass or rubber, should
not be set up, for if put into use leakage of electrolyte may cause
annoyance or trouble.
=Location of battery room.=—The proper location of the battery is
important. It should be in a separate room, which should be well
ventilated, dry, and of moderate temperature. Extremes of temperature
affect the proper working of a battery. The air should be dry, for if
damp there is danger of leakage due to grounds.
The ventilation should be free, not only to insure dryness, but to
prevent chance of an explosion, as the gases given off during charge
form an explosive mixture if confined. For this reason never bring an
exposed flame near the battery when it is gassing.
Direct sunlight should not fall on the cells.
The trays, the benches on which the cells rest, and all metal work
(iron and copper) should be painted with asphaltum varnish.
=Assembling and placing cells in position.=—Place the jars, after they
have been cleaned, in position on the stands, which should be provided
for the purpose and which should be so situated in the room that each
cell will be easily accessible. The jars are set in the trays, which
previously should be filled with fine dry sand even with the top, the
trays resting on the glass insulators.
Place the elements as they come from the packing cases on a convenient
stand or table (the elements are packed positive and negative plates
together; the positive has plates of a brownish color, the negative
of a light gray—the negative always has one more plate than the
positive), cut the strings that bind them together, and carefully pull
the positive and negative groups apart, throwing the packing aside.
After carefully looking over both groups and removing any dirt or other
foreign matter, assemble them, with separators between each positive
and negative plate.
When putting into the jars be careful that the direction of the lugs
is relatively the same in each case, thus causing a positive lug of
one cell always to connect with a negative of the adjoining one, and
vice versa. This insures the proper polarity throughout the battery,
bringing a positive lug at one free end and a negative at the other.
Before bolting or clamping the lugs together, they should be well
scraped at the point of contact to insure good conductivity and low
resistance of the circuit; this should be done before the elements are
taken apart and directly after unpacking, if the battery is to be set
up at once. The connections should be gone over and tightened several
times after the lugs are first fastened together to insure good contact.
=Connecting up the charging circuit.=—Before putting the electrolyte
into the cells, the circuits connecting the battery with the charging
source must be complete, care being taken to have the positive pole of
the charging source connected with the positive end of the battery.
=Electrolyte.=—The electrolyte is dilute sulphuric acid of a specific
gravity of 1.210 or 25° Baumé, as shown on the hydrometer at
temperature of 70° F.
The electrolyte should cover the top of the plates by one-half inch to
three-fourths inch, and must be cool when poured into the cells. The
jars should be numbered with asphaltum varnish and a line made with the
same material to indicate the height at which the electrolyte should be
kept.
=Initial charge.=—The charge should be started at the normal rate as
soon as the electrolyte is in the cells and continued at the same
rate, provided the temperature of the electrolyte is well below 100°
F., until there is no further rise or increase in either the voltage
or specific gravity over a period of 10 hours, and gas is being given
off freely from all the plates. Also, the color of the positive
plates should be a dark brown or chocolate and that of the negatives
a light neutral gray. The temperature of the electrolyte should be
closely watched and, if it approaches 100° F., the charging rate
must be reduced or the charge stopped entirely until the temperature
stops rising. From 45 to 55 hours at the normal rate will be required
to complete the charge; but if the rate is less, the time will be
proportionately increased. The specific gravity will fall rapidly after
the electrolyte is added to the cells, and may continue to fall for
some time after charging begins. It will finally rise as the charge
progresses, until it is again up to 1.210 or possibly slightly higher.
The voltage for each cell at the end of charge will be between 2.5
and 2.7 volts, and for this reason a fixed or definite voltage should
not be aimed for. It is of the utmost importance that this charge be
complete in every respect.
At the end of the first charge it is well to discharge the battery
about one-half and then immediately recharge it. Repeat this treatment
two or three times and the battery will be in proper working condition.
After the completion of a charge (initial or with the battery in
regular service) and the current off, the voltage will fall immediately
to about 2.20 volts per cell, and then to 2 volts when the discharge is
started. If the discharge is not begun at once, then the pressure will
fall quite rapidly to about 2.05 volts per cell, and there remain while
the battery is on open circuit.
=Battery in regular service.=—A battery must not be repeatedly
overcharged, undercharged, overdischarged or allowed to stand
completely discharged. After the initial charge is completed, the
battery is ready to be put into regular service.
A cell should be selected as a “pilot cell”; that is, one that is in
good condition and representative of the general condition of the
battery. The height of the electrolyte in this cell must be kept
constant by adding a small quantity of water each day. This cell is to
be used particularly in following the charge and indicating when it
should be stopped.
When the battery is in regular service, the discharge should not be
carried below 1.75 volts per cell at full load. Standing completely
discharged will cause permanent injury; therefore the battery should be
immediately recharged after a heavy discharge.
In usual service, with the normal rate, it is advisable to stop the
discharge at 1.90 volts per cell. If the discharge rate is considerably
less than normal, the voltage should not be allowed to fall as low
as 1.90 volts per cell, for the reason that with a very low rate of
discharge the voltage will not begin to fall off until the limit
of capacity is almost reached. The fall in specific gravity of the
electrolyte also serves as an indication of the amount taken out and is
in direct proportion to the ampere-hour discharge, thereby differing
from the drop in voltage, which varies irregularly for different rates
and degrees of discharge. For this reason, under ordinary conditions,
the fall in specific gravity is to be preferred in determining the
amount of discharge.
The actual amount of variation in the specific gravity of the
electrolyte between a condition of full charge and a complete discharge
is dependent upon the quantity of solution in the containing vessel
compared with the bulk of the plates. When cells are equipped with
the full number of plates, the range will be about 35 points (0.035
sp. gr.); for instance, if the maximum specific gravity reached on
the preceding overcharge is 1.209, the extreme limit beyond which the
discharge should not be carried is about 1.174. If the cells have less
than the full number of plates, this range in specific gravity is
proportionately reduced, except in the case of the “pilot cell,” which
should be equipped with a device for displacing the excess electrolyte.
The available capacity is temporarily reduced at low temperatures; with
a return to normal temperature the capacity is regained.
The battery should preferably be charged at the normal rate. It is
important that it should be sufficiently charged, but the charge
should not be repeatedly continued beyond that point. Both from the
standpoint of efficiency and life of the plates the best practice is
the method which embraces what may be called a regular charge, to be
given when the battery is from one-half to two-thirds discharged, and
an overcharge to be given weekly if it is necessary to charge daily, or
once every two weeks if the regular charge is not given so often.
The regular charge should be continued until the specific gravity
of the pilot cells has risen to within five points of the maximum,
as shown on the last previous overcharge. For example, if on the
previous overcharge the maximum is 1.210, then on the following regular
charges the current should be cut off when the specific gravity of
the pilot cell reaches 1.205. The pilot cell method of noting the end
of charge should not be used with a battery unless all the cells are
approximately in the same condition. With an old battery whose plates
are not uniform, readings should be taken on each cell to determine the
end of charge.
The overcharge should be prolonged until all the cells gas freely and
until no rise in the specific gravity and voltage of the pilot cell is
shown for five successive 15-minute readings.
Just before the overcharge the cells should be carefully examined to
see that they are free from short circuits. If any short circuits are
found they should be removed with a stick or a piece of hard rubber; do
not use metal.
As the temperature affects the specific gravity this must be considered
and correction made for any change of temperature. The temperature
correction is one point (0.001 sp. g.) for 3 degrees change in
temperature. For instance, electrolyte, which is 1.210 at 70°, will be
1.213 at 61° and 1.207 at 79°.
=Inspection.=—In order that the battery may continue in the best
condition it is essential that specific gravity and voltage readings be
taken on all cells in the battery at least once a week; the specific
gravity readings on the day before the overcharge and the voltage
reading near the end; the voltage readings must always be taken when
the current is flowing, open circuit readings being of no value. Also,
at the end of each charge it should be noted that all of the cells are
gassing moderately and at the end of the overcharge very freely.
=Unevenness of cells; cause and remedy.=—If any of the cells should
read low at either time and do not gas freely with the others at the
end of charge, examine them carefully for pieces of scale or foreign
matter which may have lodged between the plates. If any are noted,
remove them by pushing down into the bottom of the jar with a strip of
wood. Never use metal of any kind for this purpose.
If, after the cause of the trouble has been removed, the readings do
not come up at the end of the overcharge, then the cell must be cut out
of circuit on the discharge, to be cut in again just before beginning
the next charge, during which it should come up all right.
Impurities in the electrolyte will cause a cell to work irregularly
and the plates to deteriorate. Should it be known that any impurity
has gotten into the electrolyte, steps should be taken to remove it at
once. The solution should be replaced with new immediately, thoroughly
flushing the cell with water before putting in the new electrolyte.
The change should be made when the battery is discharged, for the
impurities will be in the electrolyte when the battery is discharged.
Immediately after the change the cell should be charged. If in doubt
as to whether the electrolyte contains impurities, a half-pint sample,
taken at the end of discharge, should be submitted for test.
=Sediment.=—The accumulation of sediment in the bottom of the jars must
be watched and not allowed under any circumstances to get up to the
plates; if this occurs, rapid deterioration will result. To remove
the sediment, the simplest way, if the cells are small, is to lift the
elements out after the battery has been fully charged, draw off the
electrolyte, and then dump the sediment, and clean the jar with water,
getting the elements back and covered with electrolyte again as quickly
as possible, so that there will be no chance of the plates drying out.
Electrolyte, not water, will be required to complete the filling of the
cells, the specific gravity being adjusted to standard (1.210 at the
end of charge).
=Evaporation.=—Do not allow the surface of the electrolyte to get down
to the top of the plates; keep it at its proper level (one-half inch to
three-fourths inch above the top of the plates) by the addition of pure
water, which should be added at the beginning of a charge, preferably
the overcharge. It will not be necessary to add electrolyte except at
long intervals or when cleaning, as noted above. Electrolyte added to
replace loss should be of specific gravity 1.210.
=Battery used but occasionally.=—If the battery is to be used at
infrequent periods, it should be given a “freshening” charge every two
weeks.
=Putting the battery out of commission.=—If it is thought best to put
the battery out of commission for a time, then it must be treated as
follows: After thoroughly charging, syphon off the electrolyte (which
may be used again) into convenient receptacles, preferably carboys
which have been previously cleaned and have never been used for other
kinds of acid, and as each cell becomes empty immediately fill it with
fresh, pure water. When water is in all the cells allow them to stand
12 to 15 hours, then draw off the water; the battery may then stand
without further attention until it is again to be put into service;
then proceed as in the case of the initial charge, as described above.
If for any reason any cell becomes discharged before the others, it
should be cut out on discharge and worked up to normal before being
used.
Should the battery sulphate, charge and discharge frequently, not using
less than one-half normal rate at any time and increasing to full rate
as the plates show signs of recuperation; keep the temperature of the
cells below 100° F. Frequent exercise will clear the plates in a badly
sulphated battery.
Keep careful records of all charging voltages, specific gravities, and
troubles with the cells.
The following is a recapitulation of the important points in operating
a storage battery:
CONDENSED INSTRUCTIONS.
1. Excessive charging must be avoided. A battery should not be
undercharged, overdischarged, or allowed to stand completely discharged.
2. Keep the electrolyte at the proper height above the top of the
plates.
3. The daily and weekly readings should be regularly and accurately
taken and recorded.
4. Inspect each cell of the battery carefully at regular intervals.
5. If any low cells develop do not delay in bringing them back to
condition.
6. Do not allow the sediment to get up to the plates.
7. Do not allow impurities, either solid or liquid, to get into or
remain in the cells.
8. Have the battery room well ventilated, especially while charging.
9. Never bring an exposed flame into the battery room during or shortly
after the gassing period of a charge.
10. Keep the floor and other parts of the battery room clean and dry.
11. Keep the iron, copper, or other metal work about the battery room
free from corrosion.
12. Keep all connections clean and tight.
13. Post a copy of these condensed instructions in a conspicuous place.
APPENDIX NO. 4.
SUBMARINE MINE CABLE.
Submarine mine cable is shipped on reels having an outer sheathing for
protection in transit, with at least 12 feet of both ends of the cable
brought out and coiled on the head of the reel for test purposes. If
the cable is not for immediate use, it should be moved to the cable
tank, and by means of the overhead trolley and cable tongs put in its
position in the tank, the two ends being properly tagged and firmly
fixed so as to allow it to be tested. In arranging the multiple cable
in the tanks that which is to be used first should be most readily
accessible.
The cable tank should be provided with a cover to keep it clean, as
well as to lessen as much as possible variations of temperature. Enough
clean water to cover by several inches the outer sheathing of the cable
reels should be kept in the tanks, but in climates where the water in
the cable tanks would normally freeze to a depth exceeding 2 feet, the
water should be let out of the tanks before ice begins to form and
not again admitted until the following spring. In localities where
the tanks may become a breeding place for mosquitoes, as a preventive
measure, salt water from the ocean or bay should, when practicable, be
used for filling the tanks, or where it is necessary to use fresh water
sufficient salt should be added to produce a 3 per cent solution. No
oil or kerosene should be used in the tanks.
The methods of recording tests and of classifying and transferring
submarine mine cable are prescribed by orders from the War Department.
The tests of submarine mine cable at posts will consist in determining
the insulation and conductor resistances.
The insulation surrounding the conductor of a cable is supposed to
be uniform in regard to quality of material, density, and thickness.
The resistance which it offers to the passage of a current through it
will then vary inversely with its length. In comparison the insulation
resistance of 1 mile of cable is taken as the standard. This insulation
has a large negative temperature coefficient; that is, an increase
of temperature lowers its resistance. It is customary to reduce all
insulation resistance to that at a standard temperature of 60° F.,
and for this purpose reduction factors applicable to the particular
insulation compound should be furnished with the cable. (Note: It has
been found that for most compounds, if the logarithms of the resistance
are plotted as ordinates against the temperature in degrees F. as
abscissæ, the resulting curve will be very nearly a straight line.)
The ordinary methods of measuring resistance—that is, by means of a
Wheatstone bridge, or by fall of potential, or by voltmeter—can not be
used in measuring resistance as high as that of the insulation of a
submarine cable. For this the direct deflection method is employed.
In brief, this consists of the following steps:
First. The deflection produced in a galvanometer by a current from
a battery through a known resistance, usually 100,000 ohms, is
determined, whence is calculated the resistance through which this same
battery would produce a deflection of one point using the unity shunt.
This is expressed in megohms and is called the galvanometer “constant”
under the conditions.
Second. The deflection produced by the current from the same battery
through the insulation of the cable is determined, whence, from
“First,” the corresponding number of megohms is calculated.
Third. This multiplied by the length of the cable in miles and
corrected for temperature gives the required insulation resistance per
mile.
This testing can be made most satisfactorily on dry days, but a close
adherence to the instructions herein given relative to the preparation
of the cable ends, the insulation of the cable lead and of the battery,
and the drying out of the test room and instruments should enable
satisfactory work to be done under adverse conditions of weather or
climate. The following apparatus is required: Reflecting galvanometer,
universal shunt, special testing key, 100,000-ohm resistance box,
battery of dry cells giving approximately 100 volts, and stop watch.
Figure 16 shows diagrammatically the arrangement of the apparatus for
testing a reel of cable. As a rule the instruments should be so placed
that one person may manipulate the key and the shunt while at the same
time observing the galvanometer.
The 100,000-ohm box, as a protection to the galvanometer in testing, is
always kept in the circuit and its value should be subtracted from the
resistance determined, except in the case of high insulation resistance
when it will not be necessary to make the subtraction.
The universal shunt is always employed with the galvanometer and is
used both to vary the current through the latter and to protect it from
a violent throw at the instant of making or breaking the circuit at the
testing key. This last is accomplished by having the shunt on zero at
such times.
The galvanometer being a very sensitive instrument must be solidly
supported so as to be free from jars or vibrations.
The special testing key, shown diagrammatically in the figure, has its
binding posts plainly marked. It is a double-throw key and has two
positions upon each side. When completely closed to the right, the
cable is charged through the galvanometer from the positive pole; when
to the left, from the negative pole of the battery. In each case the
deflection of the galvanometer is in the same direction. When partly
closed on either side, the cable is discharged to earth through the
galvanometer. (Note: It will be observed that the connections are such
that the galvanometer is always connected to the cable core and never
to the ground. With this connection, _so long as the lead PX is free
from leaks or grounds_, the galvanometer measures only the current
actually passing through the core and not that leaking through any
imperfect insulation in the battery and leads.)
Cable testing is a very simple operation, but extreme care is necessary
in all operations.
[Illustration: FIG. 16.—CABLE TESTING.]
The following is a detailed description:
=I. Preparing the cable for testing.=—1. Closely examine each conductor
end. Look particularly for unusually hard or brittle insulation and for
torn, pinched, or punctured insulation, especially near the ends of the
armor wires. If any of the ends are not in perfect condition, cut off
enough cable to secure good ends. (_Caution._—Do not cut off more than
enough to secure good ends, for after three or four tests it may be
necessary to unreel the whole cable to secure enough of the inner end
above water.)
2. Verify the tagging. Remember that the “shore end” is the end from
the outer coils on the reel and is numbered clockwise. The other end is
numbered contraclockwise.
3. The “ground” should be made by taking several turns of bare copper
wire around the armor of the cable to be tested and soldering them in
position. One such ground in each tank is sufficient. Whenever “ground”
or “earth” is subsequently spoken of, this ground in the tank is meant,
and not a connection to ground at some point outside the tank.
4. The leads PX and BY (fig. 16) should be of loading or other heavily
insulated wire. They must be carefully insulated from each other, from
the ground, and from the walls or other parts of buildings. This is
especially true of the cable lead PX. In damp weather porcelain-knob
insulators and porcelain tubes (the latter for use in passing through
walls or partitions) may not be sufficient to afford proper insulation
for the cable lead. In such case the latter should be suspended _in
the air_ from the testing switch to the cable tank by means of several
chains of paraffined porcelain insulators suspended by marline or
protective tape which has been boiled in paraffin. These suspensions
should be in each case under cover and should be kept as dry as
possible. The length of the leads is immaterial. If loading wire is
used, the distance between supports should be short (not over 50 feet),
as this wire stretches considerably from its own weight, pulling out
the insulation and giving a very thin wall, particularly at points
of support. Extreme care should be taken to tighten up on the knob
insulators, in case they are used, just enough to hold the wire without
pinching the insulation.
5. Using a double connector, join the lead BY to the ground wire on the
cable above the surface of the water. Put a connector on the end of the
other lead so that it can be readily attached in turn to each conductor.
6. Any protective covering, such as armor, jute, etc., should be
removed from the ends of the conductors for a distance of about 12
inches, thus laying the insulation coating bare. This latter should
not be handled and must be kept scrupulously clean. With a _clean dry_
knife prepare each conductor of the cable to be tested by cutting
off about 1 inch of the insulation from each end of the wire and
then tapering the end of the insulation for about 1 inch, leaving a
perfectly clean surface. In damp weather dip each end of each conductor
into melted paraffin (not boiling, but heated above 212° F.). Secure
one end of the cable so that it is well separated from the surrounding
objects and separate the conductors so that no ends are touching.
7. Take one strand of a loading wire about 4 feet long and wrap it
two or three times around the projecting copper end of each conductor
at the other end of the cable, then connect it to earth. See that the
conductors at this end are dry. Leave the lead PX disconnected and
suspended in the air.
=II. Setting up the testing apparatus.=—1. Select a light, dry room as
near the cable tank as practicable.
2. Use dry cells for the battery. The voltage of the battery should be
such as to give a full scale deflection of the galvanometer through the
resistance employed for taking the constant (with shunt at ¹/₁₀₀₀).
Large galvanometer throws are essential for reliable results.
Set up the cells on shelves in a small closed closet or box, with
narrow strips of wood or heavy cardboard laid between each row of
cells, lengthwise and crosswise. The height of each strip should be
about half the height of a cell, so that the two layers of strips will
come nearly to the tops of the cells and keep them well separated.
Wire the cells in series and bring the terminals out to a double-pole
single-throw switch, which should be on a heavy porcelain or slate
base and rated for at least 250 volts. (It may be found desirable to
install some electric lamps in the closet to keep the battery dry.)
If difficulty is experienced in eliminating grounds from the battery
set up in this manner, the battery box should be suspended in air by
means of chains of paraffined cleats.
3. Set up the galvanometer on a pier or on a window sill if the
building is of masonry. It should be insulated by placing its feet on a
slate or ebonite slab, or in glass insulators. Remove the cover. Adjust
the level until the suspended coil hangs freely. Maneuver the suspended
coil, by means of the knob at the top of the tube, until its face is
parallel with the face of the instrument. Then adjust the level until
the upper suspension hangs in the center of the supporting tube, and
the air gap between the coil and armature is symmetrical. Replace the
cover. Put on the scale and the telescope. Turn the mirror so that it
reflects the 0 of the scale approximately, getting exact adjustment by
moving the scale. Be careful (particularly in dry weather) not to touch
the glass of the cover or to do anything which will produce a static
charge on the glass.
The galvanometer scales are usually graduated in equal divisions
corresponding to 1 millimeter on the circumference of a circle whose
radius is 1 meter. Each tenth division is usually marked with a number.
This number is sometimes 1 instead of 10, 2 instead of 20, and so on.
The number of divisions to read and record is the number of smallest
(millimeter) divisions. Do not try to read closer than ½ of one
division. The larger the throw the less the personal error. No accurate
conclusion can be drawn from a very small throw.
4. Place a table or low shelf conveniently to one side and place the
shunt, the testing key, the ⅒ megohm box, and a voltmeter on it. The
apparatus should be insulated by an ebonite or slate slab, or glass
insulators. Fasten the shunt and the key securely to the table or the
shelf. (The use of paraffin paper for insulating instruments is a
makeshift at best. It soon gets soiled and creased, then it has to be
replaced.)
The use of lamps to keep the apparatus dry may be desirable, or it
may be found convenient to expose the apparatus to the sun for a
few minutes before beginning the test on any day. The use in the
testing room of a small stove or of a gasoline torch for two or three
hours before the beginning of the testing will ordinarily prove very
advantageous.
5. Wire up as in figure 16, except that the leads from the testing key
should be carried to the battery through the double-pole single-throw
switch above referred to. (The battery switch should be opened whenever
any connections are made or altered.) All leads used in connecting up
the instruments should be of heavy copper, and stiff enough to hold
permanently any shape to which they are bent. They should be supported
at points of connection only, and should not lie on the table or within
an inch of each other.
=III. Testing the insulation of the apparatus.=—1. _Voltmeter test of
battery insulation._—This is a rough test, but should be included. A
serious ground can be much more quickly located with a voltmeter than
with the galvanometer.
(_a_) Disconnect the battery leads at the battery switch; connect +
lead of battery to + post of the voltmeter; connect the B end of the
lead BY to - post of the voltmeter; - lead of the battery should be in
the air. Close the voltmeter switch and read.
(_b_) Disconnect the voltmeter. Connect - lead of the battery to -
post of the voltmeter. Connect the B end of the lead BY to + post of
the voltmeter; + lead of the battery should be in the air. Close the
voltmeter switch and read.
If any deflection is obtained in either case, the battery or its
connections are grounded. Locate and remove the ground. (See Foster or
some other practical handbook.)
2. _Testing the battery voltage._—Connect the voltmeter across the
battery terminals. Read and record the voltage. (If there is no
voltmeter available which will read as high as the battery voltage,
take the voltage of the battery in sections and add, or make a
multiplier of one of the resistance coils in the ⅒ megohm box.)
3. _Testing the battery and the apparatus for grounds with the
galvanometer._—With a camel’s-hair brush go over all the instruments
and carefully remove dust. See that the instruments and connections are
dry. Do not blow on the instruments.
Open the battery switch. Connect the battery leads to the battery
switch. Disconnect lead PX at P and connect the earth leads BY and EY
to the key at “_cable post_.” (Y is grounded.) _Both_ battery leads are
left connected to the key. The shunt should be on 0. Close the battery
switch. Close the testing key to the right. Turn the shunt gradually to
the unity post. The galvanometer deflection should be zero. Turn the
shunt to 0. Reverse the testing key. Turn the shunt to the unity post.
The deflection should be zero. If any deflection is obtained, there is
a ground in the battery, the apparatus, or the connections. The test
of the cable should not proceed if a deflection is obtained in either
position of the key.
In reporting the voltage + to earth and - to earth as “zero” on form,
it will be understood that this means zero using the galvanometer, as
herein described.
4. _Insulation of leads._—Turn the shunt to 0. Open the battery switch.
Connect the earth leads BY and EY to their proper posts. Connect the
cable lead, PX, to “cable” post. See that the cable tank ends of the
lead PX is disconnected at X and suspended in the air. Close the
battery switch. Close the key and turn the shunt to the unity post.
Deflections should be as small as possible and in any case _must be
steady and uniform for several trials_. Turn the shunt to 0. Reverse
the key, stopping at the discharge position. Turn the shunt to the
unity post and wait until the galvanometer rests at 0, indicating that
the leads are discharged. Turn the shunt to 0. Close the key all the
way down. Turn the shunt to the unity post. The deflection should not
differ materially from that noted above. If there is a deflection, the
trouble is in the lead PX or its connections. Go over these, carefully
examining for dust and moisture and noting particularly the proximity
of all wires of opposite potential which cross or lie near each other.
If there is a small deflection which can not be removed, a correction
must be applied subsequently to the deflection obtained in the test for
the insulation resistance of the conductor.
Using proper care, there are very few days when perfect insulation
of the instruments can not be secured. The lead leakage with
well-insulated wire put up properly will be noticed rarely.
5. _Use of Price guard-wire._—As an additional precaution against
surface leakage across the insulation at the ends of the conductor
it will sometimes be advisable to install an additional lead (not
necessarily as carefully insulated as PX) running from the testing
switch to the cable under test. This lead should be connected in at the
testing switch to the post carrying the lower blade between “D” and “C”
(fig. 16); the tank end should be bare of insulation for a sufficient
distance to enable the bare wire to be wrapped firmly, without
pinching, around the insulation at each end of the particular conductor
under test, just below the tapered portion.
The potential difference between the cable core and this guard-wire
is thus made practically nil, so that any leakage will be from the
guard-wire to the tank, consequently this leakage will not be measured
by the galvanometer.
=IV. Take the galvanometer constant as follows=: Open the battery
switch.
With a short piece of wire connect the hinge post of the testing key
marked “cable” to either “earth” post of the key, the leads to the
cable tank being disconnected at E, B, and P. Turn the shunt to 0.
Examine the ⅒ megohm box and see that all the resistance coils are
in the circuit. Close the battery switch and the testing key. Turn
the shunt to the ¹/₁₀₀₀ post. Watch the swing of the galvanometer and
when it has come to rest, read and record. Turn the shunt to 0. The
galvanometer should return exactly to 0. If it does not, readjust and
repeat until it does. The galvanometer constant is numerically equal to
the total throw in _smallest_ divisions of the scale multiplied by 100.
Remove the connecting wire and replace the leads to the tank.
If at any subsequent time during the test the galvanometer adjustment
is disturbed—that is, if it does not return accurately to zero when the
shunt is at 0—the constant should be redetermined.
=Testing the cable.=—1. See that the testing key is open and the shunt
at 0. Connect the earth lead to ground on the cable armor. Remove the
earth connection from No. 1 conductor and connect the cable lead to
this conductor; in wet weather the connector joint should be dipped in
melted paraffin. (In using paraffin to insulate joints or ends bring it
just above 212° F. to evaporate any moisture present. It should not be
boiling. The paraffin coating should be at least as thick as the rubber
insulation and extend back over the rubber for an inch or more.)
2. Close the testing key to the left (+ to earth), stopping at the
discharge position, and turn the shunt to the unity post. There should
be no deflection. If there is, it is due either to a charge on the
cable, which will disappear after a moment, or to earth currents. (It
is assumed that the testing apparatus has been thoroughly tested for
insulation.) If due to earth currents, the conductor is probably a
poor one. Earth currents are readily recognizable by their fluctuating
character. Before assuming that the trouble can not be removed, the
joint between the lead and the conductor should be examined again.
Moisture on the cable end will give a path for earth currents. Note the
value and direction of the throw of the galvanometer and record it.
3. Turn the shunt to 0, close the testing key all the way down (+ to
earth), noting the time to the second, or starting the stop watch at
the same time, if one is available. The time must be accurately noted.
The insulation resistance at the end of one minute’s electrification is
the resistance to be reported.
4. When 35 seconds have elapsed, turn the shunt to the ¹/₁₀₀₀-post and
watch the galvanometer throw; if small, move the shunt successively to
the ¹/₁₀₀-post, to the ¹/₁₀-post, and to the unity post. This operation
must be completed before 45 seconds have elapsed from the time the
key was closed. With good cable the unity post will always be reached
without danger of throwing the galvanometer reading off the scale.
Remember that each successive post should give 10 times the throw of
the preceding post.
5. At the end of one minute read the deflection, correct for the
leakage of the leads and the earth currents, and record. (See example
following.)
6. At the end of two minutes read the deflection, correct and record
it. For good cable it should be less than the deflection observed at
the end of one minute.
7. Turn the shunt to 0, and reverse the key, stopping at the discharge
position. Turn the shunt on gradually until the unity post is reached
and wait until the reading is 0, indicating that the conductor is
discharged. If earth currents are present, 0 will not be reached
or will be passed. In this case proceed as before described. A
submarine mine cable conductor a mile long will discharge ordinarily in
about three minutes.
8. Turn the shunt to 0, stop and start the stop watch; at the same time
close the key all the way down (- to earth).
9. After 35 seconds, start turning the shunt, ceasing at 45 seconds.
(See paragraph 4, above.)
10. At the end of one minute read the deflection, correct and record
it. For good cable it should be substantially the same as the
deflection observed at the end of one minute with + of the battery to
earth.
11. Turn the shunt to 0, and reverse the key, stopping at the discharge
position.
12. Disconnect No. 2 conductor from ground. Disconnect No. 1 from the
lead and connect up No. 2. Connect No. 1 to ground. It is not necessary
to wait for No. 1 to be discharged completely before disconnecting it.
13. Proceed with No. 2 as with No. 1 and repeat with each conductor.
14. On the completion of the test all conductor ends should be
carefully taped.
15. To determine the correct value of the insulation resistance it is
essential that the negative pole of the battery be connected to the
core of the cable, otherwise the products of electrolysis will tend
to seal up any fault which may exist and will cause the conductor to
appear better than it really is. With the negative pole of the battery
to the core the tendency is to deposit copper on the core and thus
to lay bare any fault. The insulation resistance of any conductor is
therefore found by multiplying the corrected deflection at the end of
one minute, with + of battery to earth, by the denominator of the shunt
used, and then dividing the galvanometer constant by this product. The
resistance of the ¹/₁₀-megohm box is neglected unless the insulation
resistance determined is very low, say, under 1 megohm, when the
100,000 ohms should be subtracted from the above quotient.
16. To determine the insulation resistance per mile at 60° F., multiply
the actual insulation resistance found by the length of the cable in
miles, and this result by the multiplier furnished by the torpedo depot
for the particular make of cable, corresponding to the temperature of
the water in the tank observed during test.
_Example._—Leakage of the leads found to be one-half division. Earth
currents found to give 1½ divisions in a negative direction from 0 of
the scale. Galvanometer throw at the end of one minute (+ to earth), 15
divisions. The corrected deflection is, 15 - ½ + 1½ = 16 divisions.
The galvanometer constant (450 divisions through ¹/₁₀ megohm, shunt
at ¹/₁₀₀₀), 45,000 megohms. That is, the battery will give ¹/₁₀ of
450 divisions = 45 through 1 megohm, the shunt at ¹/₁₀₀₀; or, what is
the same thing, one division through 45 megohms, the shunt at ¹/₁₀₀₀;
therefore with the shunt at unity the battery will give one division
through 45 × 1,000 = 45,000 megohms. The insulation resistances =
45,000 ÷ 16 = 2,813 megohms. If the cable is three-fourths mile long,
the insulation resistance in megohms per mile is 2,813 × ¾ = 2,110
megohms.
Manufacturer, Safety Insulated Wire & Cable Co.
Temperature of water in tank, 80° F.
Multiplier, 1.7056; 2,110 × 1.7056 = 3,599 megohms insulation
resistance per mile at 60° F. This result is recorded on the form.
=VI. Copper resistance.=—1. The drop of potential method is quicker
than the bridge method under the usual conditions and should be used if
the apparatus is available.
_Apparatus required._—(_a_) Source of power (110 volts D. C. lighting
circuit, casemate battery or generator); (_b_) a double-pole
single-throw switch to which the power leads are attached; (_c_) a bank
of ten 110-volt lamps in parallel; (_d_) a D. C. ammeter of not more
than 0-25 scale; (_e_) a D. C. voltmeter, 0-150 scale.
Place the lamp bank and the ammeter in one side of the power line from
the switch to the conductor, and the other end of the conductor to the
other side of the power line. Connect the voltmeter across the ends
of the cable so as to measure the drop of potential between the ends
of the conductor being tested. Close the switch, take simultaneous
readings on the voltmeter and the ammeter and calculate the resistance.
With the apparatus described a conductor 1 mile long will receive about
2½ amperes and show a drop of about 50 volts. The lamps are inserted
as a safety precaution. In no case should the current through the
conductor exceed 6 amperes. If the cable has been tested for insulation
resistance and all the conductors show high insulation, the lamps are
not necessary, provided the cable is at least a mile long.
2. The copper resistance found is reduced to that at 60° F. by
multiplying by the coefficient found in the following table with the
temperature of the water in the tank at the time of the test as an
argument:
_Reduction of copper resistance to 60° F._
+--------------+--------++--------------+--------+
| Temperature. | δ || Temperature. | δ |
+--------------+--------++--------------+--------+
| _°F._ | || _°F._ | |
| 10 | 1.1252 || 55 | 1.0113 |
| 11 | 1.1224 || 56 | 1.0090 |
| 12 | 1.1196 || 57 | 1.0068 |
| 13 | 1.1168 || 58 | 1.0045 |
| 14 | 1.1141 || 59 | 1.0023 |
| 15 | 1.1113 || 60 | 1.0000 |
| 16 | 1.1086 || 61 | .9978 |
| 17 | 1.1059 || 62 | .9956 |
| 18 | 1.1032 || 63 | .9933 |
| 19 | 1.1005 || 64 | .9911 |
| 20 | 1.0978 || 65 | .9889 |
| 21 | 1.0952 || 66 | .9867 |
| 22 | 1.0925 || 67 | .9846 |
| 23 | 1.0899 || 68 | .9824 |
| 24 | 1.0873 || 69 | .9802 |
| 25 | 1.0846 || 70 | .9781 |
| 26 | 1.0820 || 71 | .9759 |
| 27 | 1.0794 || 72 | .9738 |
| 28 | 1.0769 || 73 | .9717 |
| 29 | 1.0743 || 74 | .9695 |
| 30 | 1.0717 || 75 | .9674 |
| 31 | 1.0692 || 76 | .9653 |
| 32 | 1.0667 || 77 | .9632 |
| 33 | 1.0641 || 78 | .9611 |
| 34 | 1.0616 || 79 | .9591 |
| 35 | 1.0591 || 80 | .9570 |
| 36 | 1.0566 || 81 | .9549 |
| 37 | 1.0542 || 82 | .9529 |
| 38 | 1.0517 || 83 | .9508 |
| 39 | 1.0492 || 84 | .9488 |
| 40 | 1.0468 || 85 | .9468 |
| 41 | 1.0443 || 86 | .9448 |
| 42 | 1.0419 || 87 | .9428 |
| 43 | 1.0395 || 88 | .9408 |
| 44 | 1.0371 || 89 | .9388 |
| 45 | 1.0347 || 90 | .9368 |
| 46 | 1.0323 || 91 | .9348 |
| 47 | 1.0300 || 92 | .9328 |
| 48 | 1.0276 || 93 | .9308 |
| 49 | 1.0252 || 94 | .9288 |
| 50 | 1.0229 || 95 | .9269 |
| 51 | 1.0206 || 96 | .9250 |
| 52 | 1.0182 || 97 | .9231 |
| 53 | 1.0159 || 98 | .9211 |
| 54 | 1.0136 || 99 | .9192 |
+--------------+--------++--------------+--------+
The true length of a cable should be that of its center conductor.
From the size of the conductor and its copper resistance the length of
the cable may be computed by use of the following wire table:
_Table of resistances of pure copper wire
at 60° F._
+---------+---------+-------------+
| Size | Dia. in | Ohms per |
| B. & S. | mils. | 1,000 feet. |
+---------+---------+-------------+
| 1 | 289 | 0.11999 |
| 2 | 258 | .15130 |
| 3 | 229 | .19080 |
| 4 | 204 | .24058 |
| 5 | 182 | .30338 |
| 6 | 162 | .38256 |
| 7 | 144 | .48245 |
| 8 | 128 | .60831 |
| 9 | 114 | .76696 |
| 10 | 102 | .96740 |
| 11 | 91 | 1.21960 |
| 12 | 81 | 1.5379 |
| 13 | 72 | 1.9393 |
| 14 | 64 | 2.4453 |
| 15 | 57 | 3.0134 |
| 16 | 51 | 3.8880 |
| 17 | 45 | 4.9030 |
| 18 | 40 | 6.1827 |
| 19 | 36 | 7.8024 |
| 20 | 32 | 9.8316 |
| 21 | 28.5 | 12.397 |
| 22 | 25.3 | 15.625 |
| 23 | 22.6 | 19.712 |
| 24 | 20.1 | 24.857 |
| 25 | 17.9 | 31.343 |
| 26 | 15.9 | 39.535 |
| 27 | 14.2 | 49.839 |
| 28 | 12.6 | 62.848 |
| 29 | 11.3 | 79.250 |
| 30 | 10.0 | 99.932 |
+---------+---------+-------------+
The objections to the use of a bridge for measuring copper resistance
are the difficulty of eliminating the resistance of the plug contacts
and the time required to secure balance. The resistance of the plug
contacts may often be as high as 20 ohms, particularly if used at the
tank.
If the bridge is used at all, it should be placed in the testing room,
and the same leads employed for testing insulation should be used. The
resistance of these leads should first be determined by connecting
them together and measuring; this resistance is subtracted from each
resistance measured.
=VII. General.=—The key to success in cable testing is great care
in every detail. The cable now being furnished is all tested with
galvanometers having constants from 200,000 to 250,000 megohms. It has
all been accepted after most careful test. The chances are that it
is good when it arrives at the post, unless it has been mechanically
injured in transit, which should be ascertained by careful inspection
when delivered at the post.
Do not accept a single measurement if it shows low resistance, but
repeat until certain of results. The time between trials on the same
conductor should be as great as practicable. For example: Measurements
showing low resistance made in the morning should be repeated in the
afternoon; those made in the afternoon should be repeated the next day;
the conductor being connected to earth during the interval between
tests.
APPENDIX NO. 5.
CARE AND PRESERVATION OF SUBMARINE MINE MATÉRIEL.
Frequent inspections of all articles of submarine mine equipment
should be made, not only to check up the property, but also to
determine the condition of all matériel, and especially to see if it
has been affected by dampness. These inspections should be thorough
and detailed, as only in this manner can there be impressed on those
directly charged with the care of the property the importance of
ventilation, dryness, and the proper use of preservatives.
The generating set, storage battery, motor-generators, casemate
transformers, power panel, and operating boards will be installed in
the mining casemate, and such tools, appliances, and materials as may
be used when this apparatus is in commission will also be kept there.
The explosive will be kept in the magazines and tested and cared for in
the manner prescribed in Appendix No. 1.
The multiple and single conductor cable will be kept in the cable tanks
as described in Appendix No. 4.
All other articles of equipment will ordinarily be kept in the
storehouse, and a noncommissioned officer will be placed directly in
charge. It shall be his duty to keep the matériel in the best possible
condition, using such details from the submarine mine detachment from
time to time as may be necessary to assist him in this work. He shall
check up all articles taken from the storehouse during practice and
report at the end of the day’s work any shortage in tools or appliances
that he may discover.
Paints and oils should be kept separate from other stores, and the
floor where kept should be covered with 2 or 3 inches of sand, to be
renewed occasionally. Sawdust should never be used for this purpose.
Cotton waste which has become unfit for use should be promptly burned.
Fuses must not be stored with other explosives.
Gasoline in considerable quantities should be stored in tanks
underground and never inside of buildings. Small quantities should be
kept outside of buildings in some safe place.
When oil engines or generators are out of commission, their bright
parts should be covered with light slushing oil. Brass screw threads
and parts of tools that are liable to rust should be covered also. In
all cases the light slushing oil should be applied in a thin coat,
since this is all that is necessary to give good protection. Before
applying the light slushing oil to any surface it should be thoroughly
cleaned, so as to be free from rust, water, kerosene and lubricating
oil, as their presence will cause rusting underneath the slushing oil.
The protected surfaces should be occasionally inspected and the coating
of slushing oil renewed as often as required.
Screw threads of mine cases, steel screw threads of compound plugs,
bolts, nuts and washers, and surfaces of flat joints should be kept
coated with the light slushing oil or a mixture of machine oil and
graphite.
No oils or grease should ever be placed on points where metallic
contact of electrical instruments is necessary, nor on india rubber,
ebonite, or slate.
Mine cases should rest on racks or skids, and where space permits
should not be in contact with each other. In handling mine cases
care must be taken not to damage the bails and bolts. They should be
arranged so that the holes in the mine cases can be seen easily; these
holes should be fitted with a wooden plug which has been thoroughly
greased all over its surface. New mine cases, if galvanized, usually
will not need painting until they have been in the water. When taken
from the water they should be thoroughly dried, and if they should
show signs of rust they should be gone over thoroughly with steel wire
brushes until the rust is removed. Parts which can not be reached with
the brush should be cleaned with three-cornered steel scrapers. A
heavy coat of red lead should then be applied. Seven gallons of this
paint can be made by mixing 100 pounds of red lead ground in oil with 5
gallons of raw linseed oil. This mixture should be applied within two
or three weeks after mixing. One gallon of paint should give 10 mine
cases one coat. After this coat has been allowed to dry there should
be applied a coat of white lead toned down to a neutral gray. Seven
gallons of this paint can be made by mixing 100 pounds white lead, 2½
gallons raw linseed oil, 2½ gallons turpentine, 1 gallon liquid drier,
and adding about 1 pound of lampblack to tone down the mixture.
Mines treated in this way, if kept in a dry storehouse, and not put in
the water, should not require repainting for several years. Frequent
inspection should be made, however, for in handling the cases and
changing their positions on the racks, it will often happen that an
abrasion will be made in the surface of the paint, which if neglected
may serve as the starting point of a progressive corrosion, which may
extend rapidly under the surface of the paint. Should loose paint or
rust be seen the case should be repainted. A small wooden mallet may be
used to tap the case at all points to loosen scales of rust or paint;
then the surface should be thoroughly wire brushed or scraped and the
cases repainted as stated above. The inside of mine cases must be
inspected to see that the interior surfaces are kept free from rust.
Ground mines and ground mine buoys should be treated in the manner just
described for buoyant mine cases.
If the oil engine has not been painted, it should be given a priming
coat of red lead mixed in oil. This should be rubbed down with pumice
stone and two coats of steel-colored paint applied. The second coat
should be rubbed down and two coats of varnish then applied. After this
the engine should not need repainting for a couple of years. When,
however, repainting is necessary, the engine should be rubbed down
until all the varnish is removed and a coat of steel-colored paint
applied. This coat should be rubbed until no brush marks remain, and
one or two coats of varnish should then be applied. The steel-colored
paint should be applied flat; that is, the color which is ground in
Japan should be mixed with turpentine. One gallon of this paint is more
than sufficient to give an engine two coats.
The motor-generators and the casemate transformers usually will not
need the priming coat of red lead, as they come from the factory
painted. When it is necessary to paint them, one coat of the
steel-colored paint and one of varnish will usually be found sufficient.
Anchors, distribution boxes, junction boxes, mooring sockets, shackles,
sister hooks, and the ironwork of operating boards and power panels
should be painted with asphaltum varnish.
Paint brushes when new, and before use, should be wrapped or bridled
with strong twine and soaked in water to swell. After use they should
be cleaned with turpentine and put away in water to keep them from
drying and becoming unpliable.
Large ropes should be stored on skids, allowing a free circulation
of air. Small ropes should be hung on wooden pins. Ropes should be
uncoiled semiannually in dry seasons and stretched out for several
days to dry. Wire rope must be stored in a dry place where it will not
rust. Marline-covered wire rope should be stored where there is a fair
circulation of air. The date of receipt should be stenciled on each
reel. If not used at the end of five years it should be run through
a bath of pure distilled tar oil. This may be done by setting up an
empty reel 20 feet in front of the full reel and placing a tub of the
tar oil midway between them. As the rope comes off the full reel it is
passed through the oil and the surplus oil slicked off with a piece
of burlap, thus returning the oil to the bath. The freshly oiled reel
will continue to drip for several days, and sand should be put on the
floor under the reel to take up the excess oil. After use in water the
marline-covered rope should be thoroughly dried out and then reoiled as
above described.
APPENDIX NO. 6.
INSTRUCTIONS FOR MASTERS OF MINE PLANTERS.
The matter contained in this appendix is primarily for the information
of the masters of those vessels which are called into service for
mine planting purposes upon the outbreak or threatening of hostilities.
The master shall request to be supplied with a copy of Regulations for
Mine Planters, U. S. Army.
To each vessel will be assigned a coast artillery officer, who shall
be the commanding officer of the vessel. All orders for the vessel
shall be given to and through him. He shall have general charge of its
business and be responsible for the proper care and disposition of
all stores aboard, leaving to the master of the vessel the full and
unquestioned control and authority over all matters for which he is
professionally responsible.
Any orders to be given by the commanding officer concerning the vessel
or its crew will be given to or through the master, except that when
planting mines or operating any of the mining appliances or machinery
aboard the vessel, the commanding officer, or an officer designated by
him, may give instructions directly to any of the vessel’s officers or
to members of the vessel’s crew who have duties directly connected with
the mining work.
The duties and responsibilities of the master of a vessel engaged in
submarine mine work do not differ materially from those devolving
upon him when his vessel is otherwise employed. With respect to every
duty the vessel may be called upon to perform, it may be stated that
explicit directions as to where the vessel is to go and just what
maneuvers it is to execute in the mine field will be given by the
officer aboard, and it is then incumbent upon the master to execute the
maneuver according to his best judgment.
The duties that vessels employed as mine planters are likely to be
called upon to perform are as follows:
1. To lay out the mine fields.
2. To lay the multiple cable.
3. To plant mines.
4. To take up mines (including replacing defective mines
by good ones where necessary).
5. To take up the cable.
The commanding officer of the vessel is responsible for the proper
equipment of the vessel with the necessary apparatus for mine planting,
for the loading of all the matériel prior to the planting, and for the
method of procedure under the above heads.
The master of the vessel will carry out the orders of the commanding
officer and is concerned only in the handling of his boat to prevent
accidents to it and to the boats engaged in the planting.
The following precautions will be observed by masters:
1. If current flows across the mine field the planting vessel, to avoid
accidents, should always pass on the downstream side of the yawl boat
holding the measuring line.
2. The greatest care should be taken that the measuring line and buoy
ropes are not caught in the propellers. If the vessel has twin screws,
the upstream propeller should be stopped as soon as the measuring line
has been passed to the marking boat. In all cases a man with a boat
hook should be posted near the anchor davits and another amidships, to
hold the measuring line above the water and clear of the sides of the
vessel. Keg buoys, and as much of the buoy rope as possible, should be
held on the rail near the stern, letting the rope pay out slowly and
under tension, until the propellers are past the rope, then the keg and
the remainder of the rope may be thrown overboard.
3. A general rule is never to back either propeller when buoy ropes,
measuring lines, or cables are being handled overboard at or near the
stern of the vessel.
4. If it becomes absolutely necessary to reverse the propellers when
paying out cable, men paying it out must haul it in taut and keep it
above the wheel and clear of it. The planting vessel should not pass
nearer than 25 feet to the distribution box boat when cable is leading
out from the latter, nor should it pass over any cable, if it can be
avoided, if the depth is less than 16 feet.
5. The vessel should proceed after passing the distribution box boat
on such a course that cable will pay off smoothly without becoming
entangled. If a cable becomes fouled and entangled, the end should
be “let go” at once at the distribution box boat—the planter should
proceed on, not stop nor back its propellers. Mine cable should
never be made fast in the distribution box boat until after a mine
is dropped. It is much better to drop the mine out of position than
to endanger the propellers of the vessel. The propeller nearest the
distribution box should be stopped the moment the bow of the vessel
passes the distribution box boat on its course to drop a mine.
6. If, in planting, the vessel moves _against_ the direction of the
current, there is little danger of overturning the distribution box
boat if ordinary caution is observed. Should it be necessary to plant
against a cross current or with it, it is best to pass the cable end to
the distribution box boat by a launch or small boat. In this way the
planter need not pass within 50 or 75 yards of the boat.
7. To avoid getting foul of the buoy rope or mine after the mine is
dropped, the helm should be put over so as to throw the stern away
from the mine. The vessel should be under good headway so that the
propellers may be stopped until they are well past the buoy and buoy
ropes of the mine. These points are important; failure to observe them
will result disastrously.
In laying multiple cable, the course of the vessel invariably should
be against the current. Rather than lay cable with the current it is
advisable to postpone laying the cable until a change of the tide
causes a favorable direction of current. In the end, time will be
saved by waiting. Cable should pay off on the _upstream_ side of the
vessel if any cross current is running. All care should be taken that
the cable does not get caught in the vessel’s propellers. This is of
the greatest importance.
As the cable pays out over a chock near the bow of the vessel a man
should stand by with a 3-inch strap in readiness to stop the cable
should it be necessary, and two men should manipulate brakes to prevent
the cable from paying out too rapidly. This is especially necessary if
the water is deeper than 50 feet.
Especial care is necessary in planting mines to avoid: (_a_) Colliding
with yawl or distribution box boat; (_b_) picking up cable in the
propeller; (_c_) getting the mine cable tangled; (_d_) drifting over
the mine after it is dropped.
APPENDIX NO. 7.
MANUAL FOR SMALL BOATS.
The left-hand side of a boat or ship, looking toward the bow, is the
_port_ side, and the other is the _starboard_ side. The men who row
on the port side are called the _port oars_ and those rowing on the
starboard side are called the _starboard oars._
Boats are called single or double banked, according as they have one or
two oarsmen to a thwart.
_Thwarts_ are the seats on which the crew sits; the space abaft the
after thwart is called the _stern sheet_.
_Floorings_ and _gratings_ are the bottom boards of a boat. They
prevent the weight from bearing directly upon the planking.
The _gunwale_ of a boat is the upper rail.
The _yoke_ is an athwartship piece of wood or metal fitting over the
rudderhead.
_Yoke lanyards_ are the small lines made fast to the ends of the yoke,
by which the rudder is turned and the boat steered.
The _stem_ is the upturned portion of the keel at the bow of the boat,
to which the forward ends of the planks are secured.
Oars are said to be double banked when two men pull one oar.
The blade of an oar is the broad flattened part. The handle is the
small part of an oar on the inboard end of the loom, which the oarsman
grasps when pulling. The loom is the portion of an oar extending from
the blade to the handle. The leather is the portion of an oar which
rests in the rowlock. This is sometimes covered with canvas, but is
usually covered with leather; hence the name.
_Feathering_ is the term applied to the operation of turning the blades
nearly flat to the water after the stroke, with the upper edge turned
forward, especially valuable in rowing against a head wind.
_Rowlocks_ are forked pieces of metal in which the leather of the oars
rests while pulling. Swivel rowlocks are movable, a pin on the rowlock
fitting into a socket in the gunwale.
_Thole pins_ are pins set vertically in the gunwale and are used in
place of rowlocks.
The _steering rowlock_ is a peculiar form of swivel rowlock (fitted
near the stern of a boat) in which the steering oar is shipped. This is
sometimes called a crutch.
The _painter_ is a rope secured in the bow for towing or for securing
the boat.
_Boat-falls_ are tackles made with two blocks and a length of rope;
used for hoisting boats.
The _plug_ is the wooden stopper fitted into a hole in the bottom of a
boat to let water in or out.
A _boat breaker_ is a small keg used for carrying fresh water.
A _boat-recall_ is an understood signal made to order a boat’s return.
BOAT ORDERS.
Oars and rowlocks having been placed in the boat, blades of oars
toward the bow, rudder and yoke, if any, stepped and the yoke lanyards
clear, the men board and take their proper seats. The man pulling the
bow-oar is No. 1, the next man is No. 2, and so on, to the man pulling
the stern-oar, who is called the “stroke-oar.” The men being seated,
with oars handy, the bow-man, who may be No. 1 or an extra man, as
convenient, holds onto the wharf, side, or piling, as the case may be,
with his boat hook.
_Shove off._—At this command the bow-man shoves the boat clear, giving
her headway if possible. He boats his boat hook and takes his seat.
_Up oars._—The crew simultaneously seize and raise their oars smartly
to the vertical (guiding on the stroke-oar) and hold them directly in
front of them, the blades fore-and-aft, inboard hands grasping the
handles, holding the same well down between the knees, outboard hands
grasping the looms at the height of the chin.
_Let fall._—The oars are eased down into the rowlocks together,
brought level with the gunwale, blades horizontal and all trimmed on
the after oars. Oars must not be allowed to splash.
(1) _Give way together_, (2) _GIVE WAY_.
At the first command the men reach well forward, blades nearly
vertical, ready for the stroke. At the second command they dip their
oars at the same time as the stroke-oar and commence rowing, keeping
stroke exactly and all lifting their blades to the height of the
gunwale on the return. (Or higher if waves render this necessary.)
TO MAKE A LANDING.
In running alongside a vessel or up to a float-stage or wharf, when
several lengths away from same, give the command (while the oars are in
the water), _IN BOWS_. The bow oarsman (if there be no extra man in the
bow) finishes his stroke, then “tosses” and “boats” his oar, blade to
the bow, and stands ready with the boat hook to fend off and hold the
landing. When there is sufficient headway to carry the boat properly to
the landing, give the command, _WAY ENOUGH_. This order is given while
the oars are in the water; the men finish the stroke, then toss and
boat their oars with as little noise as possible. The oars are next the
rail, the after oars outboard of the bow oars. If the stroke oarsman is
provided with a boat hook, he grasps it and stands ready to help the
bow man.
If it be desired to stop rowing temporarily, give the preparatory
command, (1) _Stand by to lay on oars_, at which the crew pays strict
attention. Then, when ready, give (2) _OARS_. At this command, given
while the oars are in the water, the crew finishes the stroke and
brings the oars level with the gunwale, blades horizontal, trimmed
on the after oars. This position is also used for salutes, as noted
hereafter.
If about to pass so close to another boat that a collision of oars
seems probable, command (1) _Trail_, (2) _OARS_. At the second command,
given while the oars are in the water, the men finish the stroke, and
then, while the oars are still in the water, by lifting the handles
with their outboard hands the looms are thrown out of the rowlocks. The
men carry their hands outboard till the backs of their wrists rest on
the rails and the oars trail astern. (This movement is used in shooting
bridges, where lack of head room precludes _tossing_.)
To bring the oars inboard, command: _OARS_.
At this command the men raise the handles, =lower= the looms into the
rowlocks, and then raise the blades out of the water and swing the oars
to the regular position of _Let fall_.
In order to turn the boat short around (being stationary or nearly so)
command: (1) _Give way, starboard_; _back port_, (2) _GIVE WAY_; or (1)
_Give way, port_; _back_, _starboard_, (2) _GIVE WAY_. The crew keeps
stroke just as regularly as in pulling straight away. As soon as the
boat points in the desired direction command: (1) _Give way together_,
(2) _GIVE WAY_.
If it be desired to check the boat’s headway, command: _HOLD WATER_.
At this command the men drop their blades vertically into the water,
tops of blades inclined slightly forward, inboard hands grasping the
handles, outboard arms over the looms to steady the oars against the
chest. To prepare the crew for rowing command _OARS_, at which they
resume the position described under the heading _Let fall_.
To move the boat astern command _STERN ALL_.
At this command the men back water, keeping stroke as regularly as in
ordinary rowing. To resume the position of attention give the command
_OARS_, as before.
To toss oars command: (1) _Stand by to toss_, (2) _TOSS_.
The command of execution is given while the oars are in the water,
the stroke is completed and the oars raised smartly to the vertical,
with blades in fore-and-aft plane, handles of oars on bottom boards,
the wrists of the inboard hands resting on the thighs, outboard hands
grasping the looms at the height of the chin, crew sitting upright. To
place the oars in the boat give the command _BOAT YOUR OARS_. At this
command the oars are lowered toward the bow (not swung outboard) and
laid in the boat as before described. This command may be given from
the position of _Let fall_, in which case the men toss their oars and
proceed as above.
NOTES.
In rowing the blade of the oar should be raised as high as the gunwale
after leaving the water and feathered by dropping the wrist. A barely
perceptible pause should be made, and the oar next thrown well forward
and dropped edgewise into the water, taking care to avoid splashing and
chopping. Now swing the oar smartly through the water without giving it
any final jerk, and repeat as above. With green crews it may be found
necessary for the coxswain to call _stroke, stroke_, in order to get
the men to pull exactly together.
There should be a mark on the loom of the oar (about the height of the
eyes when the oar is at _toss_) to show when the blade is fore-and-aft,
thus avoiding the necessity of the men gazing up for the purpose of
finding out when this is the case. Never allow a boat’s crew to splash
with the blades when executing _Let fall_. When resting on oars, insist
that they be kept level with the gunwale and at right angles to the
keel. Talking among the crew and turning the heads to look at any
object should never be allowed while the boat is under way. In most
cases, boats should be permanently equipped with a small breaker of
fresh water, a spare oar and oarlock and a suitable anchor or grapnel.
The anchor rope to withstand a storm should be six (6) times as long
as the greatest depth liable to be used as an anchorage. For any small
boat in our service a 20-pound anchor and 12-thread (about 1 inch)
manila hawser should easily weather a hurricane. A boat should never
go out at night without a good, well-filled lantern. Many a boat has
been run down through its inability to make its presence known. Before
leaving the shore in foggy weather, provide the boat with some sort
of a foghorn and a compass, and calculate as nearly as possible the
bearings of the landing you wish to make. Take the opposite of this
upon returning, making due allowance for tide and wind in both cases.
To ride out a gale of wind in an open boat, lash the oars and grating
together, making them into a bulky bundle and weight them if possible;
span them with the painter and pitch them overboard. This will keep
the boat’s head to the sea and prevent her from drifting fast. Assist
the boat to take the seas head-on by means of a steering oar. In
rowing through a chop, where the rudder is apt to be pitched clear of
the water, it should be unshipped and a steering oar used instead.
Remember, in making a landing, that the heavier the boat is laden the
longer she will keep her way. If you are being towed by a steamer, make
her give you a line, instead of using your own, and belay it so it can
be cast off in a hurry. Carefully avoid weighing down the bow; always
use a short towline when the boat is empty and a long towline when
the boat is laden. If the boat’s painter is used for a towline, have
a knife ready for cutting it if it becomes necessary. Never go close
under a steamer’s stern unless it is absolutely unavoidable.
Officers in boarding a ship, use the starboard gangway, although they
may use the port gangway. Enlisted men use the port gangway or the
booms, unless otherwise ordered.
_Boat salutes._—The following salutes should be exchanged between boats
meeting or passing each other. No junior should pass ahead of a senior
without permission.
The junior should always salute first, and the senior should return the
salute by touching his cap.
Salutes should be exchanged whenever boats pass near enough to each
other for the senior officer to be recognized, whether he be in uniform
or not.
Officers without a flag or pennant flying should be saluted with the
hand only; those with a flag or pennant flying should, in addition, be
saluted by laying on oars.
When a noncommissioned officer is in a boat and meets another boat
containing an officer he stands and salutes. If the boat flies a flag
or pennant, the noncommissioned officer, in addition, lays on oars.
Officers of the Navy and Marine Corps and foreign officers in boats
should always be saluted when recognized.
In laden boats, towing boats, or boats under sail the hand salute only
is made on all occasions.
Coxswains in charge of boats shall always rise and salute when officers
enter or leave their boats.
Boat keepers shall stand up and salute officers passing in boats and
remain standing until the boat has come alongside or passed.
APPENDIX NO. 8.
SUPPLY LIST.
APPARATUS.
Ammeters, portable, 0-25 scale, 1 to each post.
Anchors, buoy, 500 pounds, 5 to each group of 19 mines.
Anchors, mine, 1 to each buoyant mine.
Axle, cable-reel, 1 to each cable-reel frame.
Balances and weights, 1 set to each post.
Battery, storage, 1 to each casemate.
Boards, operating, 1 to each group of 19 mines.
Boxes, distribution, 1 to each group of 19 mines.
Boxes, distribution, 1 to each group of 7 mines.
Boxes, junction, large, 3 to each mile of multiple cable.
Boxes, junction, small, 1 to each mile of single-conductor cable.
Buoy, distribution box, 1 to each distribution box.
Buoy, marking, 5 to each group of 19 mines.
Buoy, mine, 1 to each buoyant mine.
Cable, submarine, 19-conductor, according to project.
Cable, submarine, 7-conductor, according to project.
Cable, submarine, 1 conductor, according to project.
Cases, guncotton, as required.
Circuit closer, 1 to each mine transformer.
Clips, cable, 2 for each mine.
Engine, internal combustion, 1 to each casemate.
Frame, cable-reel, 3 to each post.
Fuse can, 1 to each compound plug.
Generator, casemate, 1 to each casemate.
Mine cases, according to project.
Motor generator, D. C.-A. C., 2 to each casemate.
Panels, power, 1 to each casemate.
Planting equipment for emergency vessels, 1 to each vessel:
Each planting equipment consists of—
1 axle, cable-reel.
4 blocks, snatch.
4 blocks, triplex, 2-ton.
2 come-alongs.
2 davits, anchor.
2 davits, mine.
1 frame, cable-reel.
4 hooks, trip.
Plugs, compound, 1 to each mine case.
Reels, cable, according to cable on hand.
Reel and frame, measuring, 1 to each mine field.
Shackles, anchor, 2 to each anchor.
Shackles, mine, 2 to each mine.
Sister hooks, 1 pair to each anchor.
Sockets, mooring, 2 to each buoyant mine, for wire rope only.
Springs, automatic anchor, 6 extra for each group of 19 mines.
Switches, starting, 1 to each motor generator, D. C.-A. C.
Telephones, boat, 4 to each mine field.
Testing set, insulation, 1 to each post having a cable tank:
Each testing set consists of—
1 box, resistance, 100,000 ohms.
2 cases for instruments.
1 galvanometer, D’Arsonval, reflecting.
1 key, special insulation testing.
1 repair kit.
1 shunt, Ayrton Universal.
Transformer, casemate, 2 to each casemate.
Transformer, mine, 1 to each mine.
Voltmeter, portable, 0-3-volt scale, 1 to each storage battery.
Voltmeter, portable, 0-150-volt scale, 2 to each post.
Weights, distance, for automatic anchor, 6 extra for each group
of 19 mines.
UTENSILS.
(Supply for each post, unless otherwise indicated.)
1 anvil, 50-pound.
3 axes, handled.
6 basins, wash.
24 binding posts (to each casemate).
2 blocks, tackle, double.
2 blocks, tackle, single.
6 boxes, tool.
6 brushes, battery.
6 brushes, dust.
6 brushes, paint, flat.
6 brushes, paint, oval.
12 brushes, sash.
12 brushes, scratch.
6 buckets, galvanized iron.
1 chest, carpenter’s tool:
The chest contains the following tools—
1 bits, set, of 13.
1 bit, expansive,
1 brace, ratchet.
1 chisels, carpenter’s, set of 6.
1 hammer, claw.
1 knife, drawing.
1 level, carpenter’s.
1 oilstone.
1 plane, jack.
1 plane, smooth.
1 rule, 2-foot.
1 saw, compass.
1 saw, hand.
1 saw, rip.
1 saw set.
1 square, carpenter’s.
6 chisels, cold.
4 clips, wire rope (for each buoyant mine).
4 coppers, soldering.
3 crowbars.
6 cups, drinking.
2 cutters, cable.
1 dies, letters, set.
1 dies, numbers, set.
1 drill, breast.
1 drill points, set of 15.
6 files, 6-inch, flat bastard.
3 files, 6-inch, slim taper.
6 funnels, loading, large.
6 funnels, loading, small.
1 gloves, rubber, pair (to each storage battery).
1 grindstone.
24 hacksaw blades.
4 hacksaw frames.
6 hammers, ball peen.
6 hammers, smith’s.
2 handles, with tools.
3 hatchets.
6 hooks, boat.
2 hydrometers, battery (to each storage battery).
3 irons, calking.
4 irons, grappling.
120 knives, submarine mine (for each mine company,
to be issued as part of equipment).
3 ladles.
6 lamps, alcohol.
2 lamps, battery inspection (to each storage battery).
3 lamps, Khotal.
5 leads, sounding.
12 levers for socket wrenches.
12 life buoys.
12 life preservers.
2 mallets, large.
2 mallets, small.
12 marlinespikes.
6 megaphones.
1 oilers and tray, set (to each casemate).
12 padlocks, brass, with chain.
2 pitchers, acid (to each storage battery).
2 plates, earth.
70 pliers, side cutting, 5½ inch
(for each mine company, to be issued as part of equipment).
50 pliers, side cutting, 8-inch
(for each mine company, to be issued as part of equipment).
3 pots, melting.
4 pumps, boat (to each mine field).
2 scales, extension spring, reading 200 pounds.
1 scales, portable platform.
6 scissors, 8-inch.
6 scoops, large, for trotol only.
6 scoops, small, for trotol only.
12 scrapers, iron, with handle.
4 screw-drivers, large.
4 screw-drivers, medium.
4 screw-drivers, small.
6 switches, assorted (to each casemate).
2 syringes, battery (to each storage battery).
3 tapes, measuring.
2 thermometers, battery (to each storage battery).
2 thermometers, cable tank.
2 thimbles, galvanized iron (to each buoyant mine case).
2 tongs, cable-reel.
6 torches, gasoline, hand.
2 trucks, mine case.
6 vises, bench, large.
6 wrenches, monkey, 8-inch.
6 wrenches, monkey, 15-inch.
12 wrenches, =S=.
6 wrenches, socket.
6 wrenches, spanner.
3 wrenches, Stillson.
6 wrenches, =T=, small.
EXPENDABLE STORES.
Alcohol, wood, 5 gallons to each post.
Antimony for socket alloy, 10 pounds to each 19 mines.
Books, record of cable test, 1 to each post.
Books, daily test, 2 to each post.
Books, note, 24 to each post.
Brushes, carbon, 4 extra for each machine requiring them.
Brushes, wire, 4 extra for each machine requiring them.
Cells, dry, large, 25 to each post.
Cells, dry, small, 100 to each post.
Cement, rubber, 3 pounds to each 19 mines.
Cleats, porcelain, 1-wire, 50 to each casemate.
Cleats, porcelain, 2-wire, 50 to each casemate.
Collars, Turk’s-head, large, 10 to each mile of 7-conductor cable.
Collars, Turk’s-head, medium, 10 to each mile of 19-conductor cable.
Collars, Turk’s-head, small, 5 to each mine.
Compound, commutator, 1 stick to each casemate.
Connectors, double, 25 to each casemate.
Cords, telephone, 4 extra.
Crayons, marking, 12 to each storehouse.
Cut-outs, porcelain, 2 to each casemate.
Drier, as required.
Electrolyte, specific gravity 1210, 4 carboys to each casemate.
Explosive, according to project.
Fuses, service, 4 to each mine.
Gasoline, for torches, 10 gallons to each post.
Glands for compound plugs, 2 extra for each plug.
Glue, 5 pounds to each post.
Graphite, as required.
Handles, assorted, as required for repairing tools.
Insulators, glass, 25 to each storehouse.
Jointers, copper, 1 pound to each 19 mines.
Keys, distribution box, flat, 4 extra to each box.
Keys, distribution box, split, 4 extra to each box.
Keys, mine case, 2 extra for each mine case.
Keys, shackle, 1 extra to each shackle.
Knobs, porcelain, 100 to each post.
Lampblack, 2 pounds to each 100 pounds of white lead.
Lamps, incandescent, white, 110 volts, 16-candlepower,
12 to each casemate.
Lamps, incandescent, white, 80 volts, 16-candlepower,
12 to each casemate.
Lamps, incandescent, red, 80 volts, 8-candlepower,
3 to each operating board.
Lamps, incandescent, green, 45 volts, 8-candlepower,
3 to each operating board.
Lamps, incandescent, green, 45 volts, 16-candlepower,
3 to each operating board.
Lamps, incandescent, green, 45 volts, 32-candlepower,
3 to each operatingboard.
Lead, for socket alloy, 90 pounds for each 19 mines.
Lead, red, as required.
Lead, white, as required.
Line, cod, 2,000 feet to each post.
Line, measuring, 2,000 feet to each post.
Line, sounding, 500 feet to each post.
Lye, as required.
Marline, 1 pound to each mine.
Nails, assorted sizes, 25 pounds to each post.
Needles, cleaning, for Khotal lamps, 6 to each post.
Nipples, soft rubber, 1 to each hard rubber fuse can.
Oakum, 50 pounds to each post.
Oil, cylinder, 5 gallons to each casemate.
Oil, dynamo, 1 gallon to each casemate.
Oil, lubricating, 1 gallon to each storehouse.
Oil, linseed, as required, 3 gallons to 100 pounds of lead.
Oil, slushing, 5 gallons to each post.
Oil, tar, as required for marline-covered rope.
Oil, transformer, 1 gallon to each casemate transformer.
Packing, asbestos sheet, 2 pounds to each casemate.
Packing, asbestos wick, 1 pound to each casemate.
Packings, rubber, 100 to each 19 mines.
Paint, acid-resisting, as required.
Paint, steel color, for casemate apparatus, as required.
Paste, soldering, 1 pound to each post.
Paraffin, 10 pounds to each post.
Pencils, lead, 6 dozen to each post.
Plugs, attachment, 6 to each post.
Pomade, Putz, 3 pounds to each post.
Primers, explosive, 1 to each mine charge.
Pumice stone, 2 pounds to each casemate.
Resin, 2 pounds to each post.
Rope, for distance weight, 20 feet for each automatic anchor.
Rope for heaving lines, 1,200 feet to each post.
Rope for lashings, 1,200 feet to each post.
Rope, marline-covered, according to project.
Rope, raising, 50 per cent more than of mooring rope.
Rope, wire mooring, according to project.
Rosettes, 24 to each post.
Ruberine, 5 gallons to each post.
Sandpaper, 48 sheets to each post.
Sapolio, 10 cakes to each post.
Screws, brass, assorted sizes, 1 gross when required.
Screws, iron, assorted sizes, 1 gross when required.
Screws, set, for compound plugs, 1 extra set for each compound plug.
Screws, set, for mine transformers, 1 extra set
for each mine transformer.
Shellac for insulation purposes, 5 pounds to each post.
Soap, 25 cakes to each post.
Sockets, lamp, 12 to each casemate.
Solder, wire, 5 pounds to each post.
Staples, large, 20 pounds to each post.
Staples, small, 1 pound to each post.
Suspensions, galvanometer, lower, 3 to each insulation testing set.
Suspensions, galvanometer, upper, 6 to each insulation testing set.
Tags, brass, 50 per group of 19 mines.
Tags, lead, 50 per group of 19 mines.
Tags, linen, 50 per group of 19 mines.
Tape, protective, 5 pounds to each 19 mines.
Tape, rubber, 5 pounds to each 19 mines.
Tinfoil, 1 pound to each 19 mines.
Towelling, 10 yards to each post.
Tubes, porcelain, 12 to each post.
Turpentine, as required.
Twine, 3 pounds to each 19 mines.
Varnish, asphaltum, as required.
Varnish, spar, as required.
Washers, brass, 100 to each 19 mines.
Washers, lead, 1 extra set for each compound plug.
Waste, cotton, 50 pounds to each post.
Wire, casemate, extra, 100 feet each of black, blue, red, and brown
to each casemate.
Wire, fuse, 1 pound each of 3, 12, and 25 ampere to each casemate.
Wire, lamp-cord, extra 100 feet to each casemate.
Wire, loading, 20 feet to each mine.
Wire, soft-drawn copper.
_Remarks_:
(_a_) Clips and thimbles, scales, extension spring, marline-covered
rope, and parts for automatic anchors are required only at posts
supplied with automatic anchors.
(_b_) Loading scoops are required only at posts supplied with trotol.
(_c_) In the case of articles to be supplied “as required” it is not
contemplated that they shall be kept on hand in larger quantities than
required for immediate needs.
[Illustration: FIG. 17a.—IMPROVISED MINE TARGET.]
[Illustration: FIG. 17b.—IMPROVISED MINE TARGET.]
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