[Illustration: (E)]
In the centre of the priming case is a brass tube in which the exploding
bolt works, and at the bottom of this tube is a steel-pointed pin, which
pierces the capsule on the muzzle of the exploding bolt, when the bolt is
forced down. At the side of the brass tube, and near the base of the pin,
is a small hole, covered with thin brass foil, which will allow of an
escape of water into the priming case, should any have collected at the
bottom of the tube. The loading hole of the priming case is at the bottom
of the case, and arranged with cork and cap upon the same principle as
the loading holes for main charge. A powerful spanner is provided for
screwing in the priming case and caps of main loading holes, which are
fitted with leather washers to form a water-tight joint. The priming case
can be stored separate from the torpedo if preferred, but there is no
necessity for so doing unless it is charged with a dangerous compound.
When the torpedoes are being stored, a wooden plug is inserted into the
brass tube of the priming case; there is a cavity in the plug at the
lower end; the cavity is filled with a greasy composition, into which
runs the pin of the priming case when the ping is in its place; the pin
is thus protected from corrosion, and the tube of the case secured from
any foreign matter getting accidentally into it.
The exploding bolt is fitted to work with a pressure of about 50 lbs. on
the head of the bolt for the large torpedo, and 20 lbs. for the small.
[Illustration: (F)]
On account of the great proportional length of the stuffing box, it is
quite impossible for water to enter into the tube, and the pressure can
be regulated to the greatest nicety by the quantity of thread wound on.
The bolts are easily kept in order by turning them round occasionally in
their tubes, stored as they would be in the bolt magazine (see p. 20,
Fig. Y). The best lubrication for them is hog’s lard free from salt,
beeswax, neat’s-foot oil, in proportion 3, 1, 1. The bolt has several
grooves for the thread stuffing to be wound on, and in the event of its
working too easy, a few turns of whity-brown thread on the two lower
stuffings will suffice; should it work too stiff, revolve it in the
magazine tube until it works with the desired amount of pressure, which,
after a little practice, is well known by the hand. In the event of a few
drops of water entering the tube, which has never occurred, a provision
is made for its escape (see priming case), that it may not impede the
descent of the bolt. The cavity in the bolt for containing the exploding
composition is, in length and diameter, sufficient to contain a charge
that will of itself explode the torpedo (see Fig G), without depending
upon the priming case. The bolts are all the same size, and differ only
in the direction of the slot for safety key, being port or starboard
bolts accordingly.
[Illustration: (G)]
[Illustration: (H)]
The muzzle of the exploding bolt stands one inch off the pin when in
safety position, that is, when the safety key rests on the brasswork of
the priming case. This can always be ascertained before entering the bolt
(if thought necessary) by a wooden gauge forced down until it touches the
point of the pin, which measurement transferred to the bolt will show the
distance of the muzzle when forced down to the safety position.
The safety key is secured in the slot of the exploding bolt by eight or
nine parts of strong whity-brown thread secured to the key, as shown
in Fig. J (p. 10), passed round the bolt, and securely knotted in this
manner; the parts of the thread come away with the key when drawn,
in order that none of the parts may be worked down the tube by the
exploding bolt.
[Illustration: (I)]
[Illustration: (J)]
In the event of the large torpedo being cut away in deep water after
withdrawal of the safety key, it will explode by pressure on the head of
the bolt at about sixty fathoms depth. The small one at about thirty.
The brass guard for the exploding bolt is an extra precaution (suggested
by Capt. A. Hood, R.N., Director-General of Naval Ordnance) should any
person by mistake attempt to place the bolt into the torpedo without
the safety key in its place. It is placed over the head of the bolt and
pushed down until the thumb-screw on the side works into a small hole in
the shoulder of the bolt.[1] The manner in which this guard is fitted
ensures its removal before launching, since the after lever cannot be
placed until it is. It also makes a convenient handle for turning the
bolt in the magazine.
[1] As the certainty of explosion depends mainly upon the exploding
bolt being properly charged, the inventor takes entire charge of this
important detail.
[Illustration: (K)]
The explosive composition in the bolts is powerful and safe; so packed
that no amount of concussion can explode it; the bolt must be pierced
through the capsule at the muzzle for that purpose. The bolts are
hermetically sealed at the muzzle by a metallic capsule, and can be
stored for an indefinite length of time without chance of deterioration.
The exploding point of the composition in the bolt is 420° Fahrenheit.
[Illustration: (L)]
The side and top levers are so arranged, that when driven close into
the torpedo, the bolt is down to the shoulder; and, since there are
three explosions to take place, it is calculated the torpedo will be in
hugging contact when the main charge explodes, and exploded by a powerful
discharge in the centre, thereby disposing of the explosive force to the
greatest advantage.
The torpedo must be closing to the ship when the levers are acting and
the bolt descending; no experiment for the force of explosive agents,
with a cushion of water intervening, is required. The amount of explosive
agent, when in contact, is all that is required, and the torpedo can be
manufactured to contain a larger charge, if thought necessary, with a
very small increase of dimensions; but the present size is convenient for
handling and launching; and if loaded with any of the powerful blasting
powders, would, in all probability, prove sufficient to bilge or destroy
the largest iron-clad.
[Illustration: (M)]
[Illustration: (N)]
The lanyard or side-lever is permanently secured to the short arm of the
lever; the end is rove under the fair lead on the deck of the torpedo
up through the brass oval hole in the after top lever, then down under
the fair lead (abaft the first turn), and across the deck of the torpedo
to the handle, and secured with a round turn and two half-hitches. Care
should be taken that the short arm of the lever is brought close into
the fair lead, and the lanyard should be set up sufficiently taut to
give a slight spring in the after top lever by the strain brought on it.
This lever has a steel fish on the top, in order to prevent it taking
a permanent bend. If the side-lever lanyard is properly set up, the
bolt will spring down about one-eighth of an inch when the safety key
is withdrawn, owing to the spring in the lever and shrinking of the
lanyard; this brings the muzzle one-eighth of an inch nearer the pin
without disturbing the side lever. The lanyard should be made up like a
reef-point; it should be well-greased immediately before launching.
[Illustration: (O)]
[Illustration: (P)]
[Illustration: (Q)]
To secure the fore top lever to the after, in order that a back hit
may not separate them, the small lanyards, with an eye in one end, and
whipped at the other, are first placed over the eyes in the fore top
lever, then rove through the brass hole in the after top lever, in
opposite directions, passed up through the eyes in the fore top lever,
and knotted over it. The distance from the eyes in the fore top lever
to the hole in the after top lever is so arranged that it will not
interfere with the descent of them. The fore-locks for the various bolts
which fix the levers are made of fishing-line. After knotting them, the
ends should be secured together by a seizing of thread.
[Illustration: (R)]
[Illustration: (S)]
The handles, formed of iron straps passing under the torpedo, and
terminating in four eyes above the deck, are principally for handling it;
one of the foremost eyes is made use of as a fair lead for the safety-key
lanyard, and to stop it to; the other foremost is made use of to secure
the side lanyard to Fig. N (p. 12).
The ballast is composed of iron and sheet lead; the former, a fixture
to the wooden bottom of the torpedo; the latter, screwed on with long
screws into the iron. A thin sheet of lead is always kept on the
bottom, affording a soft material for moving them about on, removing
the objection that may be made to the friction caused by an iron bottom
in the moving of them in the torpedo-room. By taking out these screws,
several more thicknesses of sheet-lead can be screwed on, the same
screws binding all together. On leaving the manufacturers, there is
sufficient lead placed on the bottom for a speed between three and ten
knots. A very large increase of ballast would require another buoy to be
strung on over and above the usual complement.
[Illustration: (T)]
The proper adjustment of the slings is most important, as the divergence
depends upon it. The after legs of the slings, when stretched out
alongside the torpedo, should extend one foot beyond the stem iron of
the torpedo for the large torpedo, and eight inches for the small one;
the distance on the slings being reckoned from the seizing round the
thimble. This first adjustment is near enough if within two inches of the
regulation.
The thimble of the slings is made suitable for wire or hemp rope, the
fore surface of it being bell-mouthed, to prevent chafe of the tow-rope;
the thimble is so constructed that the parts of the slings cannot escape
from the groove should the seizing become slack; it will be observed that
by this arrangement the edge of the thimble is not brought in contact
when rounding the stem or stern of a vessel, the nip after leaving the
tow-rope coming direct on to the fore span, and thence to the projecting
curve of the side lever.
When all four legs are pulled out, in direction of the tow-rope, they
bear an equal strain; the junction of the four legs should be on a level
with the upper towing-irons, at the same time the upper fore span should
make an angle between 80° and 85° with the near side of the torpedo.
This arrangement gives the best divergence with the least strain on the
tow-rope, and is suitable when the torpedo is kept at short scope, as
well as when a long length of tow-line is out. The slings are made of
the best Italian hemp (not laid up too hard), the rope being of the same
strength as the tow-rope; for although in towing four legs divide the
strain, yet during collision the strain might be brought on one or two.[2]
[2] It may be here remarked, the small rudder on the stern of the torpedo
is not for the purpose of increasing the divergence, but to control the
direction of the torpedo when the tow-rope is suddenly slacked.
[Illustration: (U)]
[Illustration: (V)]
The tow-rope for large torpedo can be of 2½ in. or 3 in. hemp, or 1½ in.
flexible galvanized iron wire. For small torpedo, 1½ in. to 2 in. hemp,
or ⅞ in. wire.
The buoys are made of solid cork (such cork only being used as will
ensure great floating power after being immersed for a time), it is built
up on a galvanized iron tube, running longitudinally through; on the
ends of the tube are screwed wooden cones, which bind all together and
render the buoy indestructible. The iron tube gives great facility for
stringing on the number of buoys required.
[Illustration: DRAWING (W).