To substitute the electrical method of firing the torpedo for the
mechanical one, all that will be necessary is to unscrew the priming
case from the centre hole of the mechanical torpedo, and screw in the
electrical arrangement which contains McEvoy’s patent circuit-closer,
especially adapted by him to suit this particular torpedo.
The electrical arrangement has its own exploding bolt, which differs
from the other only below the safety key, which key is fitted and worked
in the same manner as the mechanical one, in order that the electrical
arrangement might not be disturbed by an accidental blow when launching.
The insulated conducting wire is carried along the whole length of
the tow-rope in the centre, forming a core. The tow-rope, as in the
mechanical one, is bent on to the hemp buoy-rope by a sheet bend, the
strands at the end are then unlaid, sufficiently so to form a connection
between the insulated wire in the tow-rope and that projecting from
the centre hole of the torpedo; this connection can be best made with
McEvoy’s patent jointer. The other end of the tow-rope on the barrel of
the brake passes through the hollow spindle of the brake at one extremity
and is connected with the constant battery, which must be suitable for
heating platinum at the distance of 100 fathoms, the return circuit being
by the water. The levers act in the same manner as in the mechanical one,
forcing down the bolt and thereby closing the circuit through the fuze
and exploding the torpedo.
This system of exploding the torpedo may be preferred in rivers or
shallow water, where it would be considered dangerous to leave a
mechanical torpedo at the bottom; but it cannot be reckoned upon with
the same certainty as the mechanical one. It is necessarily more costly,
complicated, and delicate; the two latter conditions rendering it
unsuited for the rough work it will have to encounter.
The torpedo being provided with this centre tube in addition to the
usual priming case, admits of its being used upon an emergency, special
ones not being at hand, for various other purposes, _viz._ clearing
away obstructions; as land torpedoes; as stationary torpedoes, provided
they are not to remain a very long time in the water. In these cases
the ordinary insulated wire and jointers are all that is required. If
required to be fired at will, it will be only necessary to force down the
bolt sufficiently to close the circuit through the fuze and then secure
it. If to be self-acting, leave the bolt up in its position, as when
working at sea, to be acted upon by pressure.
DESCRIPTION OF CAPT. C. A. MCEVOY’S CIRCUIT-CLOSING ARRANGEMENT FOR
HARVEY’S SEA TORPEDO.
[Illustration: _Fig: 1._ _Fig: 2._
London: E. & F. N. Spon, 48, Charing Cross.
Kell Bros. Lithrs.
FIG. 1.—An exterior tube, _a a_; screw-head, [= _a_]; interior tube,
_b_; intermediate tube, _d_; firing bolt, _e_; spindle, _f_; long brass
spiral spring, _g_; short spiral spring, _h_; socket for spindle, _i i_;
insulated wire from battery, _k k_; insulated terminal, _l_; electric
fuze, _m_; priming space, _n n_; charging hole, _o_; insulated bridge,
_p_; metal bridge, _u_.]
The electric wire _k k_ passes through the screw-head [= _a_] of external
tube _a a_, and winding spirally around the intermediate tube _d_,
terminates in a connection with the insulated bridge _p_ at _s_. The
intermediate tube _d_ is attached to the head of the spindle _f_ at _t_.
When pressure is brought to bear on the firing bolt _e_, the spindle _f_
is forced down, and carries with it the insulated bridge _p_, until the
bridge touches the insulated terminal _l_. It will be seen that the
long spiral spring _g_ and short spiral spring _h_ serve to support
the spindle _f_, and keep the bridge _p_ off the terminal _l_ until
they are forced into contact. Whilst the insulated bridge _p_ remains
above the insulated terminal, the former is in constant contact with
the metal bridge _u_; but this contact is broken when the metal bridge
moves downward and before it makes contact with the insulated terminal
_l_. When the insulated bridge _p_ is in contact with the metal bridge
_u_, the electric fuze is out of circuit; and a current sent through
the torpedo will return by way of the earth without firing the torpedo;
but when contact with the metal bridge _u_ is broken, and contact with
the insulated terminal _l_ is made, the current is directed through the
electric fuze, and the torpedo fired.
The priming in the tube is sufficient to rupture the tubes and ignite the
charge in the torpedo.
Fig. 2 shows a section of the circuit-closer, with the spiral spring
slightly compressed, and the insulated bridge in contact with the
insulated terminal, and the circuit closed. By dispensing with the
electric fuze, and using in its place a piece of copper wire, any number
of experiments may be made with an uncharged torpedo without adjustment
or manipulation of any kind; it only being necessary to attach to the
return wire near the battery a galvanometer or electric fuze to indicate
the time of the impact.
The torpedoes here described are manufactured by J. Vavasseur
and Co., at the London Ordnance Works; at which establishment
the inventor has every facility in the supervision of the
various details in the construction of the torpedoes, buoys,
and brakes. Such supervision of the torpedoes and their
equipments is highly essential to secure safety and efficiency.