MAKING AND SHOOTING THE TORPEDO
THE submarine is first, last, and all the time an engine of death and
destruction. Even in the earliest underwater experiments, you will
remember, it was fitted with a bomb the sole purpose of which was to
blow the enemy ship to atoms.
The old bomb idea proved next to worthless, for it was a very hard job
to fix it to the ship to be sunk, and even if the submarine operator
did succeed in so doing it was at best a dangerous piece of business,
and so the odds for its failure were about as 100 is to 1.
As soon, therefore, as the submarine had been developed to a point
where it was clear that it was the coming weapon of modern naval
warfare, inventors began to rack their brains for some scheme which
would do away with the danger and uncertainty of the old-fashioned
bomb, and to make the submarine safer for its crew and deadlier for the
enemy.
Many attempts were made, but its improvement was very slow, for the old
idea of the simple bomb was firmly fixed in the minds of the inventors
and it was hard for them to break away from it.
After a long time, though—that is to say in 1860—Captain Lupius, an
Austrian inventor, hit upon a new and novel plan for a torpedo which
would travel under water, by means of a little motor in it and a pair
of wires which connected it with the submarine so that it could be
directed at will.
=The First Submarine Torpedoes.=—Lupius took his idea to Whitehead,
an English engineer of genius and ability, and he built the first
controlled torpedo which traveled under its own power in 1864. Then
Whitehead did a little thinking on his own account and he built the
_automobile torpedo_ in 1868, the cleverest and most diabolical
destroyer that man has ever yet been guilty of.
The automobile torpedo is one that not only runs under its own power
but that steers itself as well after it has left the torpedo tube of
the submarine. To Whitehead, then, must be given the credit not only of
having invented the submarine torpedo that is used with such telling
effect in the present war, but of making a success of it. The Germans,
though, with their great dislike for everything of British name and
make call their torpedo of this type _blackheads_.
=How to Make a Model Submarine Torpedo.=—Before I explain how a real
automobile torpedo is made and works, I will tell you how to make a
model torpedo which, while it will not explode at the end of its trip
through the water, will show you how a real torpedo does its work.
=The Body of the Torpedo.=—Get a piece of nice soft pine 1½ inches in
diameter and 10 inches long, and whittle it out to the shape shown
in Fig. 36. Cut a groove down the middle of it ¾ inch deep and ¾ inch
wide, to within an inch of each end. This done, screw a small screw-eye
in the _warhead_ of the torpedo, as the blunt nosed end of it is
called, inside the groove.
[Illustration: FIG. 36. A MODEL TORPEDO.]
Bore a ⅛-inch hole through the propeller end, and slip a piece of brass
tube 2 inches long which has a bore of inch in it to form a bearing
for the propeller shaft. Get a brass rod 1/16 inch in diameter and 2¼
inches long; make an eye on one end and then push the rod through the
brass tube in the tail or propeller end of the torpedo, as shown in
Fig. 36, and this is all there is to the propeller shaft. Now cut a
propeller out of tin, as shown at _E_, in Fig. 37, and solder it to the
end of the propeller shaft.
_The Steering and Diving Rudders._—The torpedo, like the submarine
itself, has two rudders, one for diving and one for steering.
[Illustration: FIG. 37. A, B, C, THE STEERING AND DIVING RUDDERS. D, E,
THE COVER AND PROPELLER.]
To make the _steering rudder_, which is the vertical one, cut out a
piece of heavy tin 1½ inches wide and 1¾ inches long, as shown at _A_
in Fig. 37; cut out one edge ⅜ inch deep as shown by the shaded part,
which will leave a tongue sticking out from each corner, and bend these
to form little tubes.
Cut off two pieces of wire ⅛ inch thick, have each one 2½ inches long,
and bend them as shown at _C_. Next drill two holes through the tail or
propeller end of the torpedo, force the sharp ends of the wires into
them and then put the other ends into the tubes of the rudder.
The _diving rudder_, which is the horizontal one, is made like the
steering rudder except that the tongues for the hinge tubes are dropped
down a little and a slot ½ inch wide and 1¾ inches long is cut out, as
shown by the shaded part at _B_.
This rudder is 1½ inches wide and 2⅛ inches long; it is fastened by a
pair of ⅛ inch wires to the tail end of the torpedo in the same way
as the steering rudder. This arrangement leaves enough room for the
propeller to turn inside of the wires, as shown at _C_.
_The Rubber Strand Motor._—The next thing to do is to fix one end of
the rubber strands to the screw-eye in the warhead and the other end to
the eye of the propeller-shaft. This gives you a cheap and simple motor
that is at once light, powerful, and easy to manage.
Cut out a cover of wood to fit over the groove containing the motor,
as shown in _D_, Fig. 37, and screw it to the body of the torpedo.
Melt some paraffin wax and run it around the cracks to make the motor
chamber watertight.
Bore half a dozen or more holes ½ inch in diameter and about an inch
deep along the exact middle of the bottom of the torpedo; fill each
hole with shot and seal them in with sealing-wax. There must be enough
shot in the bottom to weight the little torpedo so that it will just
sink on an even keel when you put it in the water. Finally, paint the
torpedo all over with black enamel (you can buy it in drug stores for
10 cents a can), and your model torpedo is ready for its deadly work.
=Your Torpedo in Action.=—To set your model torpedo scooting under the
water and, perchance, aimed at an enemy ship, fix the steering rudder
in a line with the long axis of the hull and tilt the diving rudder
at a very slight angle, say about 2 degrees, down from the top of the
torpedo.
Hold the hull with your left hand and wind up the rubber strand motor
good and tight by turning the propeller _clockwise_—that is, in the
direction the hands of a clock move—with your right hand. When you
have done this, push the torpedo down under the water, let go of the
propeller and she will shoot forward as though shot by compressed air
from a torpedo tube.
After it has made a run of from 25 to 100 feet—the distance depends on
the skill you have shown in building it—it will sink to the bottom.
Of course if you are playing a naval war game and you are shooting at
some enemy ship, it will give her a good hard bump, and this counts
ten points in your favor.
=How a Real Torpedo Is Made.=—A torpedo, as you can plainly see, is
nothing more nor less than a miniature submarine boat that moves under
its own power and that is self-controlled. And now that you have
built and experimented with a little model it will be easy for you to
understand how a real one is made and works.
_The Warhead of a Torpedo._—A real torpedo such as is shot by a
submarine to sink real ships is made of three chief parts, as far as
the outside of it is concerned. These are: (1) the _warhead_, (2) the
_body_, and (3) the _tail_.
The warhead is the blunt-nosed hollow part that forms the business end
of the torpedo; it contains two things: (a) the charge of _high powered
explosive_ which plays such terrific havoc when it is touched off; and
(b) the _detonating mechanism_ which fires it.
_The High Powered Explosive._—The explosive used is either
_guncotton_, or _nitrocellulose_, to call it by its chemical name, or
_tri-nitrotoluene_ (pronounced _ni-tro-tol´-u-en_) and which is called
_TNT_ for short.
Guncotton is simply ordinary cotton which has been treated with nitric
and sulphuric acids; when this is done it becomes highly explosive.
_TNT_ is _toluene_, a chemical formed of hydrogen and carbon, which
has been treated with nitric acid. It is used by the Germans in the
warheads of their submarine torpedoes because it is a more powerful
explosive than guncotton. Besides it can be melted as easily as lard
and poured into the warhead, which makes it an easy, quick, and safe
job to fill them. Further, it does not explode easily by shocks when it
is transported but it instantly explodes with a _detonator_.
The reason these explosives cannot be ignited by fire but explode when
struck a sharp tap is because they are very _unstable compounds_; that
is, they are very easily decomposed into their original chemical parts.
Curiously enough, but by the very discovery of this advanced scientific
principle men are now able to make the mightiest, which means the
deadliest, explosives that the world has ever known and this makes
war a thousand times as terrible now as it was in the olden days when
men fought their battles at close range with their ancient lances and
cross-bows.
=The Detonating, or Firing Mechanism.=—A modern submarine torpedo has
a diameter of from 18 to 21 inches through the warhead, and this is
loaded with from 200 to 330 pounds of guncotton or TNT, as the case may
be.
This _charge_ is exploded by a _firing pin_, or _pistol_, as it is
called. This firing pin goes clear through the charge and into a
_percussion cap_, which sets just back of the charge; the other and
front end of the firing pin goes clear through the warhead and has a
threaded end on which is screwed what is known as a _butterfly-nut_.
[Illustration: _Courtesy of E. W. Bliss Co._
A BLISS TORPEDO WITH ROTARY COMPRESSED AIR MOTOR]
The percussion cap is simply a little copper cup and in it is placed
a small charge of an explosive which is easily detonated by the
_percussion_ of the pin, that is by the pin striking it. The explosive
mostly used in percussion caps is _mercuric fulminate_, which is a
compound formed of mercury, carbon, nitrogen, and oxygen.
Since it is the violent explosion of the percussion charge which
strikes the main charge of the high explosive in the warhead, and the
fire made by the explosion of the percussion charge has nothing to do
with it, the main charge of guncotton, where this explosive is used,
is often wet down with water before it is packed in, for by so doing a
great deal more of it can be put in the same-sized space.
A _safety pin_ (see Fig. 38) is set into the firing pin, so that by
no possible chance can the latter pin work loose and explode the
charge until it strikes the ship it is intended to destroy. Also the
butterfly-nut, which I spoke of above, is used as a further safety
factor.
The safety pin is simply a pin which is threaded on one end and which
extends down through the steel casing of the warhead and screws into
the firing pin, or pistol, and holds it securely so that it cannot
strike back against the charge until it is unscrewed and taken out or
broken off, when it strikes the ship.
The butterfly-nut is simply a thumb nut with a couple of wings on it.
When the torpedo is shot out of the torpedo tube the butterfly-nut,
which is screwed up close to the warhead on the firing pin, begins
to unscrew itself by the action of the water on the wings, which now
form little propeller blades; by the time the nut reaches the end of
the firing pin and drops off, the torpedo is quite a distance from
the submarine which shot it. In this way, all danger of the torpedo’s
exploding when it is in, or leaving, the submarine, is done away
with. Fig. 38 shows a cross-section of the warhead and just how the
detonating mechanism is made and works.
[Illustration: FIG. 38. THE BUSINESS END OR WAR HEAD OF A REAL TORPEDO]
The warheads of the latest torpedoes, especially those used by the
Germans, are fitted with steel cutters, so that they can cut their way
through nets which ships may spread out to protect themselves.
_The Body of the Torpedo._—The next part of the torpedo is the body,
and there are five separate and distinct parts to it. These we have
named in the order of their position, and they are,
(1) The _air pressure chamber_; (2) the _balance chamber_; (3) the
_power chamber_; (4) the _buoyancy chamber_, and (5) the _tail-piece_
which supports the propellers and the rudders.
_The Compressed Air Tanks._—The air pressure chamber is simply a large
steel tank and air is pumped into it until it is under a pressure of
about 2,000 pounds to the square inch; this means that for every square
inch of the surface of the tank there is a force pressing against it of
about one ton.
The air is let out of the tank through what is known as a _reducing
valve_, which is in turn connected to the engines, and more about it
will be said a little later. A reducing valve is simply a valve that
regulates the amount of air which flows from the tank into the engine
and keeps it at the same pressure all the time.
If the valve were not used, the air in the tank, which is at first
under 2,000 pounds pressure, would drive the torpedo forward at a
tremendous rate of speed at first, but as the air from the tank was
used up by the engine it would lose pressure and the torpedo would soon
stop altogether. But when a reducing valve is used the torpedo keeps up
its same high speed until it has run its course and has either hit the
ship or missed it.
_What Is in the Balance Chamber._—In the balance chamber is the
mechanism that controls the steering and the diving rudders, and it is
these that keep the torpedo on a straight course and at the right depth
under the water.
The controlling mechanism is formed of four chief devices, which are
(1) a _gyroscope_ (pronounced _ji´-ro-skop_); (2) a _compressed air
motor_, which drives the gyroscope; (3) a _water pressure control_; and
(4) a _pendulum control_.
_The Automatic Gyro Control._—The gyroscope, or just _gyro_, as it
is called for short, is a kind of spinning top and you can buy a toy
one for a quarter.[22] It is simply a heavy wheel fixed to a shaft, or
spindle, and this is pivoted in a ring, as shown at _A_ in Fig. 39.
[Illustration: FIG. 39. THE GYROSCOPE.]
Now hold the gyro as shown at _B_ and give the wheel a good spin.
This done, walk straight ahead, and as long as you do so you will
hardly know that you are carrying the gyro, but the moment you try to
change your direction you will feel the gyro twisting in your hand to
counteract the movement.
This is the purpose of the gyro in a torpedo, but in this case the
wheel is very heavy and it is revolved at a high speed by a compressed
air motor. The gyro is set with its shaft at _right angles_ with the
long axis of the torpedo, as shown at _C_.
Now, just as long as the torpedo moves straight ahead in its course,
the gyro has no effect on it, but the moment the torpedo tries to
swerve from one side to the other, or shift out of its course, the
gyro pulls it back by acting on the steering rudder; it does this
by regulating the air supply of a compressed air motor, called the
_servo-motor_, and this in turn works the rudder by means of a series
of levers. In this way the torpedo is automatically kept to its course.
_The Hydrostatic, or Water Pressure, Control._—The water pressure
control is one of the devices which keeps the torpedo at the right
depth in the water.
It consists of a steel cylinder with a piston working in it. A cylinder
which is open at both ends is set in the hull of the torpedo so that
one end opens into the water outside. A spring presses against the
piston on the inside of the hull and the water presses on the piston on
the outside.
The spring can be adjusted by a screw to just balance the pressure of
the water at any depth. A small valve rod is fixed to the piston, and
this opens a valve which lets compressed air into a motor when the
pressure of the water is greater or lesser than the pressure of the
spring and this in turn works the diving rudder as shown in Fig. 40.
Suppose, for example, that the captain wants the torpedo to travel
at a depth of exactly 15 feet during its whole course. The spring is
adjusted to offset the pressure of the water at this depth, and the
torpedo is launched. Should it for any reason try to go deeper than 15
feet or to rise above 15 feet, the spring or the water presses on the
piston and closes or opens the air valve of the motor, when it moves
the diving rudder up or down until the torpedo is brought back to its
right depth.
[Illustration: FIG. 40. HOW THE WATER PRESSURE CONTROL ACTS.]
_The Automatic Pendulum Control._—The water pressure control, however,
is not enough to make the torpedo stick to an absolutely constant
depth, and so to help it a _pendulum control_ is also used.
This control consists of a pendulum which swings to and fro from
fore to aft as the torpedo dives and rises, and it also starts the
compressed air motor which operates the diving rudder, and this brings
the torpedo back to its proper depth. It is shown in Fig. 41.
=The Engine That Drives the Torpedo.=—Next comes the engine that drives
the torpedo, and it, too, is run by compressed air.
As I mentioned before, the air which runs it is regulated by a
reducing valve, but there is another important part of the power plant,
and this is the _heater_ for heating the compressed air before it is
admitted to the engine.
[Illustration: FIG. 41. THE PENDULUM CONTROL.]
Compressed air is as good to run an engine with as steam, for both
of them have tremendous powers of expansion. As soon as the air is
released from the supply tank—which keeps it compressed in a space that
is many times smaller than it would take up when it is free—and has
passed into the cylinders of the engine, it begins to _expand_, or to
spread out in every direction, exactly as steam does.
Now when air is pumped into the tank it gets very hot and this heat
is stored up in the air as _energy_; this makes the air when it is
released expand with much force and gives it the power to do useful
work.
But as the air is let out of the tank through the reducing valve it
expands and loses its energy—or _latent heat_, as it is called—and
this makes it lose its power to keep on expanding to its greatest
extent and so it gets weaker and weaker.
To overcome this bad feature of compressed air, a heater is fixed on
the engine, and just as the compressed air reaches the cylinders of the
engine it is suddenly heated and this gives it all the expansive force
it needs. The heater consists of a small oil-burner which is so fixed
that the instant the torpedo is shot from the tube an electric spark
ignites the oil, and there is, in consequence, neither the loss of time
nor power.
The engine is often of the cylinder and piston type and is built quite
like an automobile engine, except that the _inlet valve_—which lets
the air into the cylinders—is disk-shaped so that it can operate all
the cylinders one after another. The exhaust ports open outside of the
torpedo, and it sets up a tell-tale white streak of bubbles on the
surface of the water.
Some torpedoes as, for instance, the Bliss-Leavitt, use a rotary
engine. But whichever kind is used, the power plant develops from 30
to 50 horsepower, and thus each torpedo weighs about as much and is as
costly as a high-priced motor car.
_The Propeller-Shaft and Propellers._—_The Propeller-Shaft._—The
engine drives the _propeller-shaft_, or, as it is called in England,
the _cardan-shaft_. To the end of this shaft outside of the torpedo is
fixed one of the propellers.
Another hollow shaft is slipped over the first shaft and one end is
connected to the engine and to the other and outside end of the shaft
another propeller is _keyed_ on. This shaft is driven in the opposite
direction to the solid shaft inside of it by _gears_ that is, a set of
cog-wheels.
_The Propellers._—The propellers have four blades; and the reason two
propellers are used is to counteract the force of each other. That is
to say, if only one propeller is used, the force of the blades striking
the water tends to tilt the craft to one side, and hence by using two
propellers this effect is very largely offset.
_The Steering and Diving Rudders._—The vertical or steering rudder
and the diving or horizontal rudders are hinged to a frame around the
propellers as shown in Fig. 42.
As it takes a lot of power to move these rudders against the varying
water currents, an air engine must be used to work them instead of
levers that are connected directly with the gyro, pendulum, or water
pressure controls.
=How a Torpedo Is Shot at a Ship.=—And now comes the most exciting
moment of all, and that is when a torpedo is shot from a submarine at
an enemy ship.
The latest type of submarine usually has eight torpedo tubes, four of
them fore, and four aft. These tubes are shaped as shown in Fig. 43,
and are built right into the hull of the craft.
Now, when we say that a torpedo is _shot_ from a submarine we do not
mean that it is _fired_ from it, for it does not explode until it hits
the ship it is aimed at, but we simply mean that it is _forced_ out of,
or _driven_ from, the tube of the boat.
[Illustration: FIG. 42. HOW A REAL TORPEDO IS MADE.]
The force that drives the torpedo from the tube is our old friend
_compressed air_, and this is taken from the _torpedo air tanks_ of
the submarine; they are placed just above the torpedo tube and are
connected with the rear part of it.
[Illustration: FIG. 43. THE TORPEDO TUBE.]
_Shooting the Torpedo._—Now let’s see just what happens from the
moment an enemy ship is sighted up to the time the torpedo hits it and
explodes.
An up-to-date torpedo makes about 40 knots, and it will travel about
six miles before its compressed air is used up. But it cannot be aimed
and shot with certainty at a distance of over half a mile. So when an
enemy ship is sighted, the submarine creeps up upon her, with nothing
but her periscope out of the water, until she is within accurate
shooting range.
In the meantime the speed of the enemy ship has been calculated, the
depth at which the torpedo must travel to strike the ship below the
water-line has been determined, and the angle, or course, the torpedo
must take to hit the ship is figured out.
Due allowance must be made for the speed of the ship and the speed of
the torpedo to the end that the distance both will travel in a given
time may be known. Of course, if the ship is speeding along and the
torpedo is shot point-blank at her it will pass a good many yards
astern of her.
This operation is very much like that of rabbit hunting, in which you
do not fire directly at the running rabbit, but aim several feet ahead
of him, and he simply runs into the bullet or shot. So it’s all his
fault if he gets killed. Just so with the ship and the torpedo; for
instead of the torpedo running into the ship, the ship runs into the
torpedo, and so if the ship sinks it isn’t the fault of the torpedo—or
at least that is the way the German captain of a U-boat looks at it.
Before the torpedo is loaded into the torpedo tube the safety pin is
taken out of the firing pin and the butterfly-nut is loosened so that
it will unscrew easily. The torpedo is then slipped into the tube and
the _breach-block_ of the tube is closed. The compressed air is now
turned on at the torpedo air tank; when the air rushes into the torpedo
tube behind the torpedo, but the latter is kept from being forced out
by a lock.
_The Course of the Torpedo._—Next the captain sights his ship and finds
its speed and its distance from his own craft. To direct the torpedo
so that it will hit her target fairly, an instrument called a _torpedo
director_ is used. It is shown in Fig. 44, and this picture also shows
how the torpedo and the ship come together.
[Illustration: FIG. 44. HOW THE TORPEDO DIRECTOR WORKS.]
Now as the torpedo tube is fixed in the hull of the submarine the
_whole craft_ must be turned and aimed at the enemy ship. To do this
the _torpedo arm_ of the director is set parallel with the torpedo
tube; then the _torpedo speed scale_ is adjusted at the speed that the
torpedo makes and which is known.
The speed of the distant ship having been calculated, the _ship speed
scale_ is set at that speed and parallel to the ship’s course, and this
brings the sight arm in line with the observer’s eye and the line that
the ship is sailing.
When the ship crosses the line of sight the catch of the lock is
released, the compressed air blows the torpedo out of its tube, and
away she goes. The instant the torpedo has left the tube the engine and
other contrivances start to work and it then moves swiftly and surely
over a straight course.
[Illustration: FIG. 45. THE GARDINER CURRENT-CONTROLLED TORPEDO.]
Long before the torpedo reaches its goal the butterfly-nut drops off,
and so when it strikes the ship the firing pin which projects out of
the warhead is pushed back with a deal of force and explodes the charge
which either sinks the ship or cripples it.
=A Torpedo with a Cannon in It.=—Lieutenant Davis, of the U. S. N., has
invented a new kind of warhead for torpedoes, one that is even more
deadly than the style I have described.
It is made by placing a cannon in the warhead. When the torpedo
strikes the ship the cannon shoots a projectile clear through the hull
and into the inside of the ship, where it explodes. As the projectile
is fitted with a _time fuse_, it does not explode until it gets well
into the ship, and then it does far more damage than the old-style of
warhead, which explodes just as it strikes the hull. The projectile
is loaded with 250 pounds of guncotton or TNT but the warhead is not
loaded at all.
On the submarines that are now being built cradles which hold several
extra torpedoes are fitted to the decks, and in this way the number of
torpedoes which can be shot is increased.