Steamships and their story

by E. Keble Chatterton

From a Photograph. By Permission of the Cunard Steamship Co.

Another great fault of the turbine is that it can only go one way, so that in order to enable a ship to go astern, she has to be fitted with an additional propeller and turbine, the blades in the latter being placed in the opposite way; when the ship is going ahead, these just revolve idly. In practice it is usual to employ two propellers and turbines for going astern instead of one. For driving other than fast ships the turbine was found not to be economical, but the reader may ask the question: “Why not let the ship go fast? Why detain her, if she is anxious to get to port?” The answer is that she wouldn’t get there as fast, for the reason that unless the ship is designed to travel at very high speeds, the propeller, revolving at a great rate, loses its efficiency; for, instead of being able to use the water, much as an oarsman uses the water for his oar to get a good grip, the water is simply carried round with the screw. In order to counteract this failing, therefore, it has been suggested that the turbine should not drive the propeller direct but drive a dynamo, the current from which should actuate electric motors for such a speed as will suit the propellers. With this would also vanish the reversing difficulty, for a motor is easily reversible. But a paper was read by the Hon. C. A. Parsons, the Vice-President, at the annual meeting of the Institution of Naval Architects, in March, 1910, in which he gave particulars of a scheme to enable a high-speed turbine to be suitable for a low-speed tramp steamer. As Mr. Parsons’ theory has actually been put into practice, and will no doubt be found to be the solution of the problem, we may here outline so interesting an experiment. In a word, the method employed is just that which we saw was used in those early days, when the screw engines were first brought in. As the reader will recollect, the difficulty was then overcome by means of gearing, instead of the engines working directly on to the shaft; so, in principle, at least, is it in the present instance.

With a view of putting to a test turbines mechanically geared to the propeller shaft, an old screw steamer, named the Vespasian, was purchased in 1909. She was built in 1887, and has a displacement of 4,350 tons. Originally, she was fitted with ordinary triple-expansion engines, and before making any alterations it was decided to run trials with those engines in use. But in order that these should show their best performances, they were overhauled, and rendered thoroughly efficient. It was further decided, in order that the proper data under service conditions might be obtained, that she was to be run properly loaded. Arrangements were therefore made with a firm of shipbrokers to take a cargo of coal from the Tyne to Malta, and during this voyage a special recording staff on board made careful measurements of the coal and water consumed. She then returned to the Turbinia Works, and her triple-expansion engines were taken out, and in their place were installed two turbines, one high-pressure and one low-pressure, the former being placed on the starboard side, the latter to port, a reversing turbine being incorporated in the exhaust casing of the low-pressure turbine. By means of mechanical gearing the power was conveyed from the turbine to the shaft, and without having made any alterations to the propeller, the vessel was loaded again to her proper trim and sent out to sea in February, 1910. The results are significant, and may be summed up thus: the Vespasian was found to possess under normal full-speed conditions an increase of about one knot per hour owing to the higher efficiency of the turbine, but with reduced water-consumption, and consequently coal consumption, amounting to nearly 20 per cent. Further, the weight of the reciprocating engines was 100 tons; that of the turbines is only 75. Thus the ship is enabled to carry a larger amount of cargo, whilst simultaneously she effects a saving in coal, in oil, in engine-room staff and in up-keep. Mr. Parsons asserts that the turbines and gearing have given no trouble, have caused very little noise or vibration, and there is no appreciable wear on the teeth of the gearing.

To the Allan Line belongs the honour of having been the first to introduce the turbine upon the Atlantic, and at the beginning of the year 1905, the Victorian and Virginian, which had been contracted for two years earlier, began running. These two ships are employed on the Liverpool-Montreal service, and were built to be of as great a size as safe navigation of the river St. Lawrence would permit. They displace 12,000 tons each, and are fitted with Parsons triplicate turbines, driving three independent shafts and maintaining a speed of 17 knots average; but on her trials the Virginian attained a speed of 19·8 knots, and the Victorian 19·2 knots. Three propellers are used for steaming ahead, and two low-pressure turbines are employed for manœuvring either ahead or astern; these are provided with a supplementary turbine for going astern. When going ahead, the steam is first used in the high-pressure turbine engine and then allowed to flow therefrom to the two low-pressure turbines, after which it passes to the condensers. Owing to the turbine system the vibration is reduced to a minimum, and since it is possible, from their nature, to place the turbine engines very low in the hull, it follows that the screws also can be placed very low. The practical effect of this is that the propellers are rarely out of the water in a heavy sea, and so the objectionable “racing” disappears. The Virginian soon showed that she was not merely a comfortable, but a comparatively fast ship, for she made an eastward trip in the shortest time hitherto occupied between Canada and England.

In the same year the Cunard Line followed with the Carmania, their first turbine liner, fitted with three turbines and three screws. She was preceded a little by the Caronia, a sister ship in every way except that the latter is propelled by two sets of quadruple-expansion reciprocating engines, driving twin-screws. These ships have a displacement of 30,000 tons, and a length over all of 675 feet. They were built of a strength that was in excess of Board of Trade and other requirements, and when we state that no fewer than 1,800,000 rivets were used in the construction of each, one begins to realise something of the amount of work that was put into them. Their steel plating varies in thickness from three-quarters of an inch to an inch and an eighth in thickness, the length of each plate being 32 feet. Fitted with a cellular bottom which is carried well up the sides of the ship above the bilges, they can thus carry three and a half thousand tons of water-ballast. The principles underlying the design and construction of these ships were steadiness and strength, and in the attainment of this they have been eminently successful. There are eight decks, which may be detailed by reference to the photograph of the Carmania [facing page 188]. Immediately below the bridge is the boat deck. Then follow successively the upper promenade deck, the promenade, the saloon, upper, and main decks. Below the water-line come two other decks for stores and cargo, the depth from the boat deck being eighty feet. Both of these ships are fitted with the now well-known Stone-Lloyd system of safety water-tight doors, which renders the vessel practically unsinkable. This enables the doors to be closed by the captain from his bridge, after sufficient notice has been given by the sounding of gongs, so that everyone may move away from the neighbourhood of these doors. But should it chance that, after they have been shut, any of the crew or passengers have had their retreat cut off, it is only necessary to turn a handle, when the door will at once open and afterwards automatically shut again. The system is worked by hydraulics, and is a vast improvement on the early methods employed to retain a ship’s buoyancy after collision with an iceberg, vessel or other object. A glance at the illustration will show that a very great amount of consideration was paid to the subject of giving the Carmania a comprehensive system of ventilation, a principle which has been carried still further in the Mauretania and Lusitania.

In the event of war the Carmania and Caronia would be fitted with twelve large quick-firing guns, for the hulls were built in accordance with the Admiralty’s requirements for armed cruisers. For this reason, also, the rudder is placed entirely under water, and besides the ordinary set of steering gear, there is another placed below the water-line.

A STUDY IN COMPARISONS: THE “MAGNETIC” AND “BALTIC.”

From a Photograph. By Permission of the London & North Western Railway.

On her trials the Carmania attained a speed of over 20 knots, and the saving in weight by adopting turbine engines as compared with the Caronia’s reciprocating engines was found to amount to 5 per cent. In actual size these fine ships are inferior to the Great Eastern, but they were built with meticulous regard for strength, and needed 2,000 tons more material than was used in the old Brunel ship. The arrangements of the Carmania’s turbines are worthy of note. There are three propellers and shafts. That in the centre is the high-pressure turbine, whilst the “wing” (or two side) turbines placed respectively to starboard and port are the low-pressure and astern turbines. Steam is supplied by eight double-ended and five single-ended boilers, which are fitted with Howden’s system of forced draught. This latter enables the air to be heated before it enters the furnace, and was patented in 1883. It is also in use on the Mauretania.