STEAM V. ELECTRICITY.

Auckland Star, Volume LVI, Issue 192, 15 August 1925, Page 17

STEAM V. ELECTRICITY.

FOR DRIVING WARSHIPS.

COMPARISON OF METHODS.

AMERICA'S BIG EXPERIMENTS.

(By Lt.-Com. C. H. ROLLESTON,R.N.)

Six ships of the American JTleet how in these waters are entirely dependent on electric propulsion—an innovation" of recent years, and one 'which has given' rise to a considerable amount of; discussion. Although the older school of sea-going engineers still regards, everything electrical on - board ship • with • a certain amount of suspicion; the fact remains that electrical . propulsion, ' and .in greater degree electrical auxiliaries, are well beyond" the experimental stage, as has been conclusively proved in thecase : of propulsion in the American battleships, and in regard.to auxiliaries in many other veessehV ; There, are,. howeyier, undoubted, objections to the electric drive in ships.; The installation weighs more than the geared turbine or reciprocating ' engine, and where uniform, speeds are /required it lis less efficient than the geared turbine as fitted in the. ships of the Royal Navy. Electric drive occupies more space, and it has not yet been proved to possess that reliability which constitutes the most essential "factor in any- form of marine propulsion.

On the other hand, the Americans claim that the electric drive has many advantages. They say ■ that- the .gear' boing -reversible, no.reversing element is: required in the prime mover, which can; be kept moving in-the same during the "operation of goihg,astern.- • It is claimed also that the electric drive is comparatively. silent, that it has greaterflexibility than the mechanical gear, and, further, that the propeller driving unit, can be dissociated from the prime mover and fitted in the most convenient positionto obtain the desired result.

Furthermore, it is said that'the'electric drive enables full power, to, fbe> utilised for going astern, an advantage not possessed by ships fitted ;with .geared tui> bines. '...,'; '

The six ships fitted with.,• the • electric! drive are the Maryland*, Colorado, West Virginia, California, Tennessee, arid New Mexico. In all these ships'jit.is claimed that the system is entirely successful from every point of view.--The New Mexico has two sister-ships, Idaho and Mississippi, fitted with; geared turbines, so that some comparison' Efts been possible, under identical cofidjifc'ions. It* was reported that the New-.Mexico wa. more economical in fuel consumption at all speeds than her two sifters, ;and that she has far better manoeuvring power: '," All by Electricity. ; In the Maryland, Colorado and: West Virginia part of the mairr boiler, steam is diverted to run six auxiliary turbo-, generators which supply, ; current, for. innumerable purposes. The anchor -gear, workshop lathes, refrigerating plant, bakeries; laundries, galleys;, etc., are all run with electric current. The ammunition hoists and even the guns are electrically manoeuvred. So extensive, indeed, is the system in these latest ships that every possible item of equipment, down to potato jpeelers and ice cream freezers, is electpigß,yy operated. In the California four alternating current moiors are fitted, one to each propeller' shaft, and these are supplied with curfent'vat 3400 volts from two turbo-generators. It is claimed that these shi'ps'when proceeding at full speed of ,20 knots can be brought to rest in minutes, a remarkable indication i of;, the immense power and flexibility of the,, astern movement. . .!?•'■• '.'■ " :,

Steam had a struggle jto supplant sails as the motive power;for ships at sea, and the fight by jiron and steel, to supersede wood in ship .construction was well illustrated in the • wellrfcnowri play " Milestones." .Commercially, the former battle is not yet won, .because transport •per sailing ship is. still j- cheaper than by steamer, whose only ■ advantage is in speed and with some cargoes matter not at all—while, sails score heavily thr6Ugh' absence of all running costs except wages and food. In a sailing ship the winds 'of heaven— and sometimes of the Other; place—take the place of fuel, and a' bit of galley fat will quickly take out..of-'a block or a shackle pin the squeak, "which in an engine room means that the lubricating oil greaser behind-'the oilcan has fallen down on the job. "• '

A Hard Task. But electricity, in spite;, of the American Navy, is going to. have a much harder task in supplanting- steam. Steam, as steam, has never; failed. The human element controlling; it has at times done so, and enclosing and directing it in the, way it should go has occasionally been; found defective. A main- steahi'.. ; bUrst once in H.M.s. Formidable vat Gibraltar, and we buried on the Neutral Ground next the accident was traced to an who opened up the valves dnKai jlong length of cold steam pipe in the wrong order, and thereby .caused a bad "watter-hammer" on the; valve,. which broke. On the other hand, after the main action' at the ' EaUdand Islands, the Kent and pursuit of the German light cruisers,; both .greatly exceeded their original "i.'trial speeds, thought they were old ships.at thetime. One cannot believe, however, that a progressive people like- th£-Americans should have discarded ah;;,old arid tried friend without Granted electricity has >gt;eat economic advantages, but these {are of no consideration whatever if ;,they jeopardise an affirmative answer to the question, "Are we certain that in the stress., of action the engines apd : boilers. and everything connected with them-are; going to do their job?", . 'Costs, either initial or running, matter "not one iota;' efficiency and reliability are -the-para-mount considerations. If electricity and steam can both satisfy those conditions, then cost may he considered. But any shadow of doubt (about the one : or the other should meap-.; its entire elimination. !?Jfr>*j.! . Leaving internal combustion engines out of consicVjration, we nndi that even with an electric behind the electricity. Steam-boilers provide the power for running the generators which operate thoeleptric motors geared to the propeller .shaft. Therefore, as far as boiler installations m concerned, electricity ■:. Can, advantage over steam. : A*y«pg;g to go wrong with the boi era SW||gg driven vessel is just as likely to happen to the boilers of an electric *»«*-*» the question next becomes one of steam turbine against electric motor. But what drives the electric generator, and through it the motor? A steam turbine of course. So electricity again loses any advantage it may have because .one steam turbine is justas likely, to break down as another. So the <I™%°£ resolves itself into-" Lt an moioir more reliable or efficient than a f i . •" - - ' "> -",.. ...•-..

steam tur bine ?" ) Thisflst, a. "question that anyone can really -answer -aftervery little . thought. The - majority, ; of ships in ,the R-X, and, practically all big liners,' which rtin-ifuir speed -all the time, are turbine .driven, and I know of no case where there has been a breakdown, not due to'the human element, though time and again ships have.tried their main engines to\ the utmost* The, same' cannot be said of- electricity./