No fool can be silent at a feast. — Solon of Athens

Twentieth Century Inventions - Charles Gibson




Marine Inventions

UNSINKABLE SHIPS—MARINE STEAM-TURBINE—ELECTRIC PROPULSION—JET PROPULSION—PENDULUM PROPELLER—HYDROPLANES—ICEBERG DETECTOR.


Unsinkable Ships


After bulkhead-doors had been recognised to be a necessity for the safety of ships, there remained the danger of the men failing to close the doors. The loss of a large French steamer through this cause brought the subject into prominence, and efforts were made to provide some automatic means of closing all bulkhead-doors from the bridge. The apparatus known as the 'Stone-Lloyd system' came into favour very quickly, and is now in general use on all large liners.

It goes without saying that what is necessary is not only some automatic release of self-closing doors, for this would mean cutting off the possible escape of the men who happened to be working below. The invention provides against this, by leaving each door free to be opened by any individual desiring to pass through, after which the door closes automatically once more. Another necessity is that the doors must not be put out of action by any wilful tampering. When the invention was installed for the first time on a large liner (Kaiser Wilhelm der Grosse), some of the crew working below the water-line did not like the idea of a system of shutting the doors from the bridge. It seemed to them that in case of any accident they would be shut in and drowned like rats in a trap. Repeated demonstrations showing how the closed doors might be opened without difficulty by merely moving a small lever at the side of the door, one being on either side of the bulkhead, served to convince the majority of the crew that the invention was a safe one. But a few refused to be satisfied, and in order, as they thought, to protect themselves, they placed substantial props under some of the doors so that they could not be closed. On the next occasion when the captain tested the working of the doors from the bridge, his indicator showed him that these particular doors had not closed. A hasty examination by the captain and the engineer showed the cause, and brought trouble upon the men who had tampered with the system.

Should anything happen to go wrong with the closing apparatus of any particular door (a very improbable thing), the door closes of itself and will not remain open, although it can be operated by any one desiring to pass through it. The indicator shows the officer in charge that this particular door has closed when it ought to be open, and its mechanism is put right.

It will be of interest to see the means which are employed to bring about these different operations. The inventor (G. C. Ralston) made searching reliability tests with compressed air, electricity, steam, and hydraulic power, and he decided upon hydraulic power as being the most satisfactory motive power for closing and opening the doors; it is free from danger, easily understood, and may be kept in working order by any ordinary mechanic.

In addition to the hydraulic pressure pump, there are four capacious patent steam hydraulic accumulators, capable of supplying power in the event of the pumps being stopped. The hydraulic pump and accumulators are above the water-line, hence the pumps cannot be thrown out of action by water rising in the pump-room.

A branch from the pressure-mains rises to the bridge, where the pressure can be turned into either of two smaller pilot-mains running the whole length of the ship. One of these operates a controlling valve at each door, which in turn causes the door to close, while the other pilot-main operates the power for the reverse action, causing the door to open. Each door is fitted with a hydraulic cylinder, which operates a pinion engaging with a rack on the centre of the door. It is capable of exerting a force of about two tons when closing, and a greater force when opening the doors. This power is conveyed by the pressure-main, while the pilot-main merely operates the valves of the cylinders. Each of these valves is also under direct control by a lever placed on either side of the bulkhead, and it is by means of this lever that any one desiring to pass through may raise the door after it has been closed from the bridge. The door may be opened also by a hand-wheel operating directly on the pinion and rack.

When the doors are about to be closed from the bridge, a warning gong sounds, in each compartment, for about twenty seconds, to give men time to pass through the doors. If any one should happen to remain in the compartment after the door has closed, he has only to move the control lever, whereupon he reverses the action of the hydraulic cylinder, and the door opens to let him through, and then closes automatically behind him. If it should be thought necessary to close the doors during a fog, or when any danger seems imminent, the stokers may still draw coal from a water-tight bunker, by having a boy stationed at the door to hold the lever over in the lifting direction, thus keeping the door open as long as necessary. Immediately the boy lets go the lever, the door will close automatically.

In order to prevent the over-heating of the water in parts of the pressure-mains, which happen to pass across the top of the boilers, or in close proximity to steam pipes, the water is kept in constant circulation. To prevent the water freezing in the mains, some glycerine is added, there being one part of glycerine to three parts of water. This addition of glycerine serves as a lubricant to bearing surfaces, and as a preservative to packing and joints.

It will be observed that this automatic system has the great advantage of enabling the captain or other officer in command to close the doors in anticipation of an accident, instead of waiting till there is an impact. If desired, there can be added an automatic control for each door, by means of a bilge float, so that in the event of a sudden inrush of water, when the doors are open, the hydraulic valve will be thrown into action automatically. A further safety device may be added in the form of fusible plugs placed in the coal-bunkers, causing the doors to be closed automatically in case of fire. However, the main feature is the direct control of the automatic doors, by the officer in charge of the ship, leaving it possible for any one to escape, and still leaving the vessel in a water-tight condition. Despite the unfortunate loss of the Titanic, through an unlooked-for ripping of her side, there is no doubt that these automatic water-tight doors rank as one of the greatest contributions ever made towards the unsinkability of a ship.


Marine Steam-Turbines


Apart from the steam yacht Turbinia, built in 1894, and two torpedo-boat destroyers ordered by the British Admiralty in 1899, the application of the steam-turbine to marine propulsion belongs to the present century. But the steam-turbine itself was well-established on land during the nineteenth century.

Up till 1909 there was no outstanding invention in connection with marine turbines, and even then it was a demand for some suitable intermediate gearing in order to make the high-speed turbine applicable to low-speed vessels of twelve knots and under. Mechanical gearing of the double helical type was introduced by the Parsons' Company, but this has little interest for the general reader. Single helical gear had proved remarkably free of the noise associated with geared wheels, the reason being that with helical gear there is always line contact between two meshing teeth. It was found, however, that the obliquity of the teeth set up side-thrust upon the wheel bearings, and to obviate this two separate wheels were used, their teeth being of opposite obliquity. In this way the one side-thrust neutralized the other. Finally the two teeth of opposite obliquity were combined on one wheel, producing a double helical gearing. The introduction of electrical gearing two years later has more interest to the outsider.


Electric Propulsion


The introduction of a dynamo and a motor to act as gearing between the high-speed turbine and the necessary low-speed propeller-shaft was discussed in 1908 by W. P. Durntall, at the Institute of Marine Engineers, and a little later by Henry A. Mayor before the Institution of Civil Engineers, but the first practical demonstration was given by Henry A. Mayor, with the yacht Electric Arc, in 1911. This craft was directly under the control of the navigating officer on the bridge, leaving the engineer-in-charge free to attend to the running of the plant. By operating an ordinary engine-room telegraph on the bridge, the officer himself altered the speed, stopped the propeller, or reversed its direction, while the prime-mover continued at full speed in one direction.

This operation would involve the breaking of large currents which might damage the contacts of the main switch, but an inter-locking mechanism prevents this possibility. The opening and the closing of the circuit can take place only when the exciter circuit is open and no current is flowing.

A vessel of 250 feet in length, 42 feet 6 inches in breadth, 19 feet in depth, and adapted to carry 2400 tons of cargo was launched in 1913. The motor in this vessel, the Tynemount, is of novel construction. It is a three-phase squirrel cage motor, and has two separate windings, one of which is connected to an alternating dynamo having eight poles, while the other winding is connected to a second generator having six poles only. When these two currents of different periodicity are passing through the motor, it runs at full speed. But if one of the generators is switched off, the prime-mover may still run at full speed, while the motor having current in one winding only will run correspondingly slower. Each dynamo has a separate prime-mover, and if the lower speed is to be maintained for any time, the engine of the idle dynamo can be shut down.

It is obvious that even a turbine speed of 3000 revolutions per minute may be reduced to a propeller speed of 100 revolutions per minute, so that whatever the type of the prime-mover may be (steam, gas, or oil), it can be run at its maximum efficiency. It is evident, also, that the control of the ship is very simple, being governed by an electric switch. In this second Mayor boat, the Tynemount, the control has been placed in the engine-room, but if desired it can be on the bridge, as was the case in the Electric Arc.


Jet Propulsion


Attempts to propel a boat by the reaction of a jet of water discharged through a converging nozzle at her stern have not been successful from a commercial point of view, but as mentioned at page 126, this is deemed a possible field for the Humphrey explosion pump. The idea is attractive: a ship whose prime-mover is an explosion pump acting directly upon the water without any intervening pistons, cranks, shafts, or propellers.

Several fire-floats, stationed in canals and harbours, have been driven by jet propulsion, but in such cases the question of speed does not count. The pumping plant of the floating fire-engine has been used as the prime-mover. In one recent case, a boat 50 feet long, 11 feet broad, 5 feet deep, 3 feet draught, with a relatively small pumping outfit (1000 gallons per minute), was fitted with two one-and-a-half-inch nozzles fore and aft. The speed was only about five miles per hour, but the distances to be covered were very short. This method of propulsion was found to be extremely convenient for maneuvering purposes, as the boat could be steered and reversed by the operation of two valves. These valves are controlled by two levers, by means of which two jets of water can be sent astern for going ahead, or they can be directed forward for going astern, or with one jet forward and one jet astern, operating at opposite sides of the hull, the vessel can be turned round in her own length.


Pendulum Propellers


The screw-propeller has had a distinguished career during the two last generations, and still holds the foremost place in marine propulsion. Indeed, one finds it difficult to imagine any better mechanical means than to screw the ship's way through the water. But an inventor in Denmark has succeeded in propelling a ship in somewhat the same manner as a fish propels itself.

In this invention there is a pendulum propeller, which is analogous to the fish's tail. This propeller oscillated 180 double swings per minute, and produced a speed of 7.7 knots, when fitted in an officers' launch for the Russian Navy. The pendulum propeller was three feet long, with an area of 1*2 square feet, and weighed 40 lbs. Each swing was 72 degrees (30 degrees on each side of the vertical). In an attempt to increase the speed of the launch, the propeller was caused to oscillate 230 double swings per minute, but the vibration became very disagreeable. In any case, the increased oscillations did not advance the speed of the boat, but actually reduced it to 7.4 knots. In order to obtain a higher speed it was found necessary to increase the amplitude of the pendulum propeller instead of its frequency.

A vessel of 83.3 feet along the water-line, 19 feet broad, and with a draught of 8.3 feet was fitted with two pendulum propellers. These were arranged one on either side of the stern, and in this way it was found possible to dispense with the ordinary steering rudder.

The inventor claims that the pendulum propeller-rudders would render navigation much safer during foggy weather, or in navigating rivers and harbours, for no matter how little way the ship has on, the pendulum propellers can pull her stern round at once. The propellers are turned into any desired position by means of the steering wheel and a worm gear.

It is the novelty of the invention which interests us, but it may be noted that the inventor says (1913):—"The latest investigations have proved that two pendulum propellers, 12 feet long, and in certain positions in which they are able to swing 90 degrees instead of 60 degrees, can transmit, without any trouble, 1200 horse-power at 40 double swings per minute, sufficient for a ship of 8000 tons displacement at 10 knots."


Hydroplanes


The idea of driving vessels over the water instead of through it is not new. A clergyman conceived the idea about fifty years ago; he even made experiments in the British Admiralty tank, but the weight of the steam-engine prevented success; the possible ratio of power to weight was very poor.

Some of us may remember that a very eminent scientist of last century declared that flying machines would be impossible for the very same reason, but the advent of the internal combustion engine altered the factors.

So long as a vessel had to be driven through the water, it was of little use to keep on adding more powerful engines, not because of the additional weight, but because of the fluid resistance (surface friction and wave-making) to the boat's motion. Of course, the internal combustion engine added great speed to small boats, as is evidenced by the fast-speed motor boats; but these also reach a speed limit because of the friction of the supporting fluid In the hydroplane this friction resistance is very greatly reduced; the boat is analogous to a skipping-stone, which, though heavier than its displaced water, remains on the surface by constantly moving over thy, water.

While at rest the hydroplane is floated in water, just as any other craft, by its static buoyancy; but when driven along by its engine at a high rate, the resistance of the plane bottom causes the boat to rise to the surface with very little displacement of water. In 1902 we thought twenty-one miles per hour an excellent speed for a motor boat, but the hydroplane can 'walk' round having attained a speed of forty-six miles per hour.

The hydro-aeroplane, sometimes called a water-plane or seaplane, belongs to the subject of aviation, which has been dealt with in a special volume in this series, by the well-known aviator, Claude Grahame-White.


Submarine Sound Telegraphy


While it has been known for a very long time that water is an excellent conductor of sound, approximately five times better than air, it was not till the opening years of the present century that the knowledge was put to a practical use at sea.

The idea is to sound a gong below the water, say on a buoy or lightship, and to have a sound-receiver, also below the water, and attached to the hull of the steamer desiring to pick up such signals. The steamer itself is fitted also with a sounding gong, so that signals may be sent by it to other ships. The United States Navy have such apparatus installed on their submarines and on the parent ships, and it is claimed by American naval officers that it is this signalling apparatus which has enabled them to avoid such terrible disasters as have occurred to British and French submarines.

Some of the steamers plying between New York and Boston are equipped with sub-marine sound telegraphs, and signals may be picked up by a steamer when distant seven miles from the sounding gong. The receiver need not be on the outside of the hull, but may be clamped to the hull on the inside, for the sound vibrations can be transmitted through the iron plates to water in the receiver on the other side of the plates. The receiver consists of a cup-shaped metal cylinder, having the open end edged with rubber and clamped against the inside of the hull. There is a microphone of special construction contained in the sound-receiver, so that the sound-vibrations conducted by the water will control an electric current in the microphone. This electric current is conducted to an ordinary telephone receiver situated in the pilot-house.

The steamer has a sound-receiver on each side of the ship, and as the particular receiver which is acted upon more directly by the sound-vibrations will be operated much more vigorously than the other one situated on the opposite side of the ship, it is easy to detect from which direction the signals are proceeding. The exact location may be found by turning the ship's head about until both impulses are equal, and then noting the compass position. It is sufficient to have one telephone receiver with a switch, by means of which the receiver may be connected to either circuit at will.

It has been found that high-frequency vibrations carry better than those of lower frequency. The pitch of the bell which has been adopted by the United States Navy is about 1200 vibrations per second, the pitch of a soprano voice. The bell may be operate l compressed air or by electricity; or in the case of an isolated buoy the motive power may be obtained by means of a spring, which is wound up by the rise and fall of the buoy. Even in calm weather the ordinary swell is found to give several signals per minute.

The suggestion has been made that a steamer should carry a starboard and a port bell, each of different pitch, so that in foggy weather ships approaching one another might know exactly the position of the other—the case being analogous to what is done in clear weather at night by a starboard and a port lamp—each sending out a definite frequency of a ether waves.


Iceberg Detector


There are several inventions by which a distant iceberg may be detected and warning given on board an approaching vessel. One of the most ingenious of these is based upon a discovery of nearly a century ago that an electric current may be generated by heating or cooling the junction of two pieces of dissimilar metals. In the present case there are two half-rings of dissimilar metals, and a number of such couples form a thermopile. This current-generator may be placed on the hull of the vessel below the water-line. As in the case of the submarine telegraph, it is not necessary to have the apparatus on the outside of the hull. In the present case the thermopile is fixed to the inside of the hull, below the water-line, and the changes of temperature are conducted through the hull, iron being, of course, an excellent heat conductor.

If there is a cooling or chilling of the junctions in the thermopile the electric current will be generated in one direction, whereas an increase in temperature will generate a current in the opposite direction. These two different currents operate two different relays. The relay responding to the current generated by a decrease in temperature switches on a local current to a red lamp and to a shrill-sounding bell. The other relay, which responds to the current due to an increase of temperature, switches on a green lamp and a low-toned bell, while an indicator records the variations of temperature.

The signalling apparatus may be placed in the chart-house, the electric current being led there by means of wires from the detecting apparatus. There would be danger if the thermo-electric apparatus should happen to be out of working order when the officer in charge was depending upon it to give warning. This possible danger is obviated by the officer having a simple means of testing the apparatus at any moment. For this purpose a separate wire circuit is run down from the chart-house to the detecting apparatus. By closing a switch in the chart=house, an electric current heats a small resistance placed in proximity to the thermopile, and thus increases the temperature of the junctions. This will generate a current in the signalling circuit, causing the green lamp and low-toned bell to be energised, and the officer is satisfied that the apparatus is in good working order. The changes of temperature due to the presence of icebergs is very marked even several miles distant from the bergs.

That there does exist a very sharply defined change of temperature in the water is evident from a report which was made by one of the Inspectors of Lighthouses (Dominion Government), in the New York Sun of 26th May, 1912:

"Latitude 41 degrees North, Longitude 50 degrees West. Approaching this vicinity from the eastward, . . . we got a temperature of 60 degrees at the bow and 48 degrees at the stern."

Within the next ten miles they encountered a huge iceberg.