VA1 57 U5 ^v Cornell University Library VM57 .U58 1883 olin 3 1924 030 900 843 Cornell University Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924030900843 47th Congress, ) HOUSE OF EBPRESENTATIVES. ( Ex. Doo. M Session. ] \ No. 48. IMPROVEMENTS IN NAVAL ENGINEERING IN GREAT BRITAIN. LETTER FROM THE SECRETARY OF THE NAYY, IN RESPONSE TO A resolution of the Mouse of Representatives., transmitting a report on the latest improvements in naval engineering in Great Britain. I' January 9, 188S. — Referred to the Committee on Naval Affairs aud ordered to be ( printed. Navy Department, Washington, January 8, 1883. Sir: Iu response to thb^ea'olution of the House of Representatives of January 5, 1 have the honor to furnish the report of Passed Assist- ant Engineer John A. Tobin, United States Navy, made, in 1882, to the Bureau of Steam Engineering of the Navy Department on the latest improvements in naval engineering in Great Britain. A request having been made to the department to promote the trans- mission of this report to Congress with a view to its publication, the following estimate of the cost was obtained from the Government Print- ing (.)ffice : 1,000 copies with illustrations $1,318 62 1,000 copies without torpedo boats >^^ ^? Each additional thousand with illustrations - 731 42 I have the honor to be, very respectfully, WM. E. CHANDLER, Secretary of the Navy. Hon. J. Warren Kbifer, Speaker of the House of Representatives. r ^CORNELL UNSVEH^SiTY! LIBRARY LETTER or TRAN!SMITTA:|p. Washington, D. C, Jtme 26, 1882. Sir: In compliance with orders of the Navj' Department, dated February 10, 1881, detaching me from the United States navy -yard, Portsmouth, N. H., and directing me to proceed to Glasgow, Scotland, for the purpose of procuring professional information deemed useful to the naval service, and to make a written repoi t of the same to the Bu- reau of Steam Engineering, and a subsequent order, dated July 1, 1881, received at Liverpool, England, directing me to procure plans and specifications of the latest war ships, including hulls, armament, ma- chinery, &c., for the information of the Naval Advisory Board, I have the honor to submit the accompanying report. I have to state that in making this general report I have omitted all the important matter furnished by the Lords Commissioners of the Ad- miralty, as it was their expressed wish that such matter be kept confi- dential; and for a like reason I have excluded certain particulars so kindly and generously given to me by some of the leading Clyde builders. My first duty on arriving in Glasgow, Scotland, was to attend the Naval and Marinre Engineering Exhibition, held in the corporation gal- leries, under the auspices of the town council and local engineers and ship-builders. .YMJDU*' '■■ The management of the exhibition was ably carried 'out under the direction of Mr. James Paton. m ]OI)H t": The exhibits, which comprised some very interesting models, were, classified under five headings, as follows : (1) Naval architecture. (2) Marine engineering. (3) Equipment. (4) Navigation and harbor works. (5) Miscellaneous. The fact that the exhibits by the English Admiralty and the various ship-building and engineering firms included but a few of the latest designs, which I subsequently examined with others in course of con- struction at the naval dock-yards and private establishments, is my reason for not .making a special report on the exhibition; but I have frequently, under the different headings, referred to such of the exhibits as I deemed valuable. A series of interesting lectures on the following subjects were de- livered during the time of the exhibition, a copy of which, together with the catalogue of the exhibition, I have had the honor of forwarding to the Bureau of Steam Engineering: (1) On some results of recent improvements in naval architecture. By William Pearce, esq. (2) The laying and repairing of siibmarine telegraph cables. By Andrew Jamieson, 0. E. (3) 4 NAVAL ENGINEERING IN GREAT BRITAIN. (3) The fundamental principles in naval architecture and marine engineering. By Eobert Mansel, esq. (4) Light-house characteristics. By Sir William Thompson, -F. E. S. (5) Progress in yachting and yacht-building. By G. L. Watson, esq. (6) Else and progress of steam navigation. By W. J. Millar, C. E. (7) Eesistance and speed of ships. By F. P. Purvis, esq. {8) The river Clyde and harbor of Glasgow. By James Deas, esq. (9) On steel. By James Eiley, esq. After I had spent a few weeks at the exhibition studying and familiar- izing myself with the objects of interest, the leading Clyde builders kindly extended me an Invitation to visit their works, and, in doing so, provided every facility in the procurement of data and particulars of their latest and most approved productions. Among those who were especially generous were Messrs. D. & W. Henderson, Messrs. John Elder & Co., Messrs. Eobert Napier & Sons, Messrs. A. & J. Inglis, and Messrs. Denny Bros. Concluding my labors at Glasgow, I proceeded to ShefBeld and Lon- don. At Sheffield I made frequent visits to all the leading steel and armor plating works. While in London my time was especially devoted to the fulfillment of the Navy Department's order relative to supplying information for the Advisory Board, and to the study of the latest improvements in engi- neering at the naval dock-yards and various engineering establish- inents. As very little in the way of engineering progress occurs without ibeing made known to the world, either through the columns of the London Engineer and Engineering, or by the able members of the dif- ferent scientific bodies of the kingdom, I have had occasion frequently to refer to these two sources of information ; not, however, without first investigating and deteimining for myself the merits and demerits of the matters which 1 have presented. In addition to the many courtesies received from the eminent Scotch firms, already referred to, I desire to acquaint the department of the invaluable assistance rendered me by Mr. Bret Harte, U. S. consul at •Glasgow, who, from the first, was untiring in his efforts to make my trip all that I could wish, To the Lords Commissioners of the Admiralty : to the director of naval construction, Mr. N. Barnaby ; to the engineer-in-chief of the British Navy, Mr. James Wright, 0. B. ; to Sir Edward Eeed, K. C. B., and his partner, Mr. Francis P. Elgar, I am also greatly indebted for every courtesy and for certain valuable information. I have the honor to be, sir, very respectfully, your obedient servant, JOHN A..TOBIN, Passed Assistant Engineer, U. 8. N. Engineer-in-chief William H. Shock, U. S. N., Chief of Bureau of Steam Engineering, Navy Department, Washington, B. G. IMPROVEMENTS IN iNAVAL ENGINEERING IN GREAT BRITAIN. COMPOUND ENGINES AND OTHER MACHINERY. In the merchant marine the accepted types of compound engines are the two-cylinder inverted compound engine, with intermediate receiver and the cranks placed at right angles, the tandem inverted type having two and three cylinders working on cranks disposed at angles of 90°^ and 120O with one another : the three-cylinder inverted compound en- gine, having the high-pressure cylinder in the middle, with an inter- mediate receiver and the two low-pressure cylinders on the outside, with cranks placed 120° apart, which types have been adopted in the steamships Alaska and Arizona, of the Guion line, and in the Servia, of the Cunard line. The engines of the City of Eome are the largest of the tandem type that have been yet made to work with three cranks set at an angle of 120° to each other. Tandem engines are usually worked on two cranks placed at right angles, as in the Germanic and Britannic, of the White Star line. In the British Navy the foregoing, with the exception of the tandem type, are in use, but are placed in a horizontal position. In some of the later war-ships, as the Conqueror, Ajax, and Aga- memnon, the engines are of the in verted- cylinder type with cranks placed at right angles. The adoption of this type of engine depends very much upon the amount of protection that is given to the vital parts of the ship by coals and deflecting and side armor. At the Naval Engineering ExhibitionI, Mr. John Irving, of Messrs. Denny & Co., of Scotland, exhibited a design of considerable merit of a four-cylinder engine of the tandem type, as one of the most suitable engines for very large steamers, claiming that an engine of this kind can be made economically as to first cost, would be easy to handle and accessible for repairs, and would develop equal power in a space at least one-quarter less than that occupied by the three-oyliuder engine. The difiSculty sometimes met with in removing the low-pressure covers and pistons, he overcomes by making the glands and stufllng boxes between the cylinders in halves. The construction of the low-pressure and high-pressure valve-gear is such that the two balance each other, thus obviating the necessity of balance cylinders. Both pumps are made double acting, and the pump-gear appears very simple and neatly designed. In regard to space, the four-cylinder engine could be quite comfort- ably managed in an engine-room from twelve to sixteen feet shorter than is required for a three-cylinder engine of equal power, which, in. cargo steamers, is an important advantage. (5) 6 NAVAL ENGINEERING IN GREAT BRITAIN. Mr Kirk, of the eminent engineering Arm of Messrs. Eobert Napier & Sons, of Glasgow, had in course of oonstraction an inverted three- cylinder, continuous expansion engine of his own design, intended to develop a little over 2,000 horse-power. The dimensions of the cylin- ders are as follows : Diameter of cylinder inohea.. Stroke of piston feet.. Area of piston square incnea . . p . (4 T^ '=i% tuo -a w S 30 45 , 4.5 4.5 706. 86 1, 590. 43 ^5" 60 4.5 2, 827. 44 Proportion of high-preasure cylinder to mid ^ *'*^ ?* ?t Proportion of mid-preasure cylinder to low i +*^ J Proportion of high-pressure cylinder to low 1 to 4 The steam supplied by steel boilers is expanded successively from a working pressure of 125 pounds per square inch. The point of cut-off is set at six-tenths from commencement of stroke. Under ordinary working, however, the point of cut-off will be thirty- six-hundredths from commencement of stroke. By this plan there is but one cylinder in direct communication with the condenser instead of two, and thus the amount of condensation is much smaller than when the walls and passages of two large cylinders are opened to the condenser at every stroke. By this arrangement, also, no change in temperature takes place be- tween the steam in the high-pressure cylinder, and that in the middle cylinder, save the change from expansion and from other losses com- mon to all engines. The different working parts of the engine are made interchangeable, and the great advantage secured of having the three cranks divide the circle equally, which arrangement, by giving a steady and uniform motion, is known to have produced the most evenly balanced engine yet made. Mr. Kirk, before undertaking the design of these engines, examined the steam log-books of a great many of the most successful merchant steamers engined on the compound system, and found that the best re- sults obtained were not lower than one and eight-tenths pounds of coal per indicated horse-power. Mr. V. 0. Marshall subsequently verified this by the carefully-col- lected data given in Table I, which shows the average consumption of coal per indicated horse-power per hour in compound engines in vessels making long voyages, to be 1.82 pounds. He estimated for the contin- uous-expansion engine a consumption of Impounds of coal per indicated borse-power, this to include all coals used for the various auxiliary en- gines — distilling engines, &c. This plan, as will be remembered, was first carried out in the steam- ship Propontis about ten years ago, when Mr. Kirk was associated with Messrs. John Elder & Go. ; but the full advantages of the system were not attained at the time, owing to a difflculty met with in carrying a sufilciently high pressure in the boilers. I have since learned that, at the offtbial trials of these engines, Mr. Kirk's calculations have been more than realized both as to speed and economy of fuel. NAVAL ENGINEEEING IN GREAT BRITAIN. 7 Through the kindness of Captain Watson, superintendent captain of the Canard Steamship Company, I am able to show the advantage in economy of fuel of the compound engine over the simple engine, by means of the following official data (see Tables I and II) taken from the records of three of the company's ships, after having madfe flvie voyages between Boston and Liverpool. I have designated the ships by the letters A, B, and C. Table I. — Steamship A. "WITH COMPOUND ENGINES: I. H. P., 1,230. [Showing distance run. Time on passage outward and homeward. Oonsumptiou of coal.] i Bate of leaving Liverpool. Distance run. Outward. April 14, 1880 December 15, 1880. Jannary 19, 1881... March 12, 1881 April 21, 1881 Total . Mean . Knots. 2,975 2,939 2,880 2,917 2,961 Home- ward. Knots. 2,907 2,952 2,952 14, 675 i 14, 657 2,935 2, 931. 4 Consumption of coal. Out- ward. Tons. 349 380 385 374 353 Home- ward. Outward. Tons. 344 407 Time on passage. Draught of .water, leaving — D. B. M. 11 15 13 27 12 21 58 11 23 17 11 11 37 Home- ward. D.S.M. 9 19 45 15 17 37 11 9 13 3 44 11 8 6 1, 841 I 1, 841 I 61 19 61 10 6 ;. 2i 368. 2i 12 4 51 12 6 49 Liver- pool. Ft. In. 20 21 3 20 2 20 9 19 3i 101 5i 20 34 Boston. Ft. In. 22 7 22 4 22 li 21 11 22 7i 111 7 22 3t WITH SIMPLE ENGINES: I. H. P., 1,100. May 18, 1871. July 26, 1871. May 10, 1873 . June 26, 1873. July 31, 1873. Total . . Me^n . . 3,892 2,871 2,964 2,908 2,934 14, 569 2,922 2,854 2,971 2,950 2, 952 . 14, 649 510 480 406 523 562 456 470 510 2,571 I 2,405 514. 2| .481 12 15 44 12 6 39 12 21 50 13 7 25 13 14 16 64 17 54 11 14 11 16 12 12 16 55 12 3 30 12 12 36 60 15 3 21 6 19 5i 19 3} 20 5i 20 8 101 4J 20 3.3 22 li 22 li 20 44 21 4i 21 7i 107' 7i 21 6.3 Steamship C. With compound engines : I. H. P. , 500 ; consumption of coal per day, 14 tons. With simple engines: I.-H. P., 485 ; consumption of coal per day, 23 tons. Table II. — Steamship B. WITH COMPOUND ENGINES: L H. P., 1,.500. [Showing distance run. Time on passage, outward and homeward. . Consumption of coal.] Date of leaving Liverpool. February 14, 1879.. April 23, 1879 Slay 7, 1879 June 11, 1879 July 16, 1879 September 33, 1879. Distance run. I *^°°f™Ji''°" I Time on passage of coal Outward. Knots. 2,955 2,930 2,925 2,934 3,934 Total I 17, Mean Home- ward. Out- ward. Knots. 2,975 2,973 2,970 2,974 2,979 2,972 17,843 2, 937. 6 . 2, 973. 8 Tons. 480 447 386 428 389 409 Home- ward. Tans. 421 410 40S 383 402 390 Outward. D.M.M 13 20 35 12 8 10 12 11 8 10 18 23 11 9 4 2, 4U 70 4 07 65 10 Home- ward. D. S. M. 11 3 29 11 3 25 11 '4 10 5 35 10 3 53 10 14 8 401. s! 11 4 14 I 10 21 45 Draught of water, leaving — Liver- pool. Boston. Ft. In. 20 3 20 19 104 19 9 19 84 21 24 Ft. In. 22 104 23 3 23 22 9 23 2 23 120 64I 138 04 20 14' 23 NAVAL ENGINEERING IN GREAT BRITAIN. Table II.— Continued. WITH SIMPLE ENGINES: I. H. P., 1,300. 1 . , ' J-'ate of leaving Lwerpool. 1 Distance run. Consumption of coal. Time otf passage. Dranght of water, leafing— Outward. Home- ■ward. Out- ward. Home- ward. Outward. Home- ward. Liver- pool. Boston. September 14, 1874 2,933 2,925 2,946 . 2, 922 2,941 2,968 2,960 2,962 2,972 2,970 2,978 2,985 615 1 513 695 558 640 S.'in 12 13 13 20 6 12 3 17 17 2 20 12 3 30 12 16 10 15 11 10 15 10 10 7 50 11 2 35 10 20 40 11 15 30 20 2 20 9 20 li 21 9i 20 10 20 Hi 20 5J 21 4i 20 December 8, 1874 January 12, 1875 .. - 803 590 21 9 fobruary 23, 1875 660 665 594 606 20 9 March 30, 1875 20 7i Total 17, 635 17, 817 4,070 3,411 SO 10 12 65 4 56 124 7i 124 114 2,939 2 qG9 a' fi7ft a 568.5 13 9 42 10 20 49 20 9i 20 95 It will be seen that the decrease iu the consumption of coal by ship A, on the outward vo.vages was 146 tons; and on the homeward voy- ages, 113 tons, after the simple engine was replaced by the compound engine. The time on the passages outward and homeward, as well as the mean draught of water, on leaving Liverpool and Boston, were nearly identi- cal. The difference in the average indicated horse-power was only 150. CRANK SHAFTS. More attention than formerly is now given to the construction and inaterialof crank shafts since somany accidents have occurred from want of homogeneity and from defective forgings of these pieces. The Lon- don Engineer mentions thatnot lessthan one hundred shafts are broken every year iu British ships. M. J. T. Milton, assistant to the chief engiQcer to Lloyd's Eegistry, as- cribes many of these accidents to undue strains resulting from the bear- ings being slack and out of alignment. The common way in engines of . the two-cvlinder type is to make the crank shafts in two pieces coupled in themiddle, each hallLbeinginterchangeable and reversible, while some of the latter and larger ones are built up in pieces. On account of the ductility, tensile strength, and uniform quality of mild steel, this metal bids fair entirely to supplant the best iron as the material for both large and small crank shafts. Crank shafts are now largely constructed both of ingot steel and of scrap steel. The ingot is considered preferable to scrap, owing to its greater homogeneity and freedom from impurities found in wrought iron. The crank shaft of the steamship Alaska, of the Guion line (see Plate 1), made by John Elder & Co., is wmposed of mild steel, and consists altogether of fifteen pieces. This method of building up crank shafts, though attended with a greater first cost and slightly increased weight, is claimed to produce greater strength and sounder work throughout. Plate 2 represents one of the three hollow crank shafts of the City of Eome, composed of Sir Joseph Whit worth's fluid compressed steel and made up of five separate pieces, there being fifteen pieces in all put together in the manner shown. Prominent among the ships of the British Navy fitted with Whitworth's fluid compressed steel shafts are the Inflexible, Iris, Mercury, and Leander (the latter now build- ing). f-^ 10 NAVAL ENGINEERING IN GREAT BRfl'AIN. fitted iu the Eussian imperial yacht Livadia, in H. M. S. I^elsou (see Plate 4), and in the steamships Arizona and Alaska, of the G-uion line, by Messrs. Elder & Co. ; and in the Parisian, of the Allan line, and iu the Leander and class now building by Messrs. E. Napier &. Sons. Thus far they have given great satisfaction, especially in large en- gines, and are found to have the advantage of requiring a smaller per- centage of power to operate them, and much less labor to overhaul, and are less liable to derangement than ordinary slide valves. OAST-STBBL PISTONS. Among the most recent innovations in engineering are the mild cast- steel pistons of the Leander and class, the production of the Steel Com- pany of Scotland. Each engine has two high-pressure and two low-pressure pistons of 48 and 78 inches diameter, respectively. The smoothness and sound- ness of the castings certainly reflect much credit on their makers. They were tested by direction of Engineer in-Chief Wright, and found to possess the maximum of strength and rigidity with a reduction of 30 per cent, in weight from that of cast-iron pistons ot the same diame- ter. This to engineers is an important item in producing a reduction of friction so necessary to the increased piston speed employed in modern marine engineering. Plate 5 is a sketch of a steel piston cast at the works of the Steel Company of Scotland. PISTON-PACKING. Steel piston-packing springs of large size have been in use in many of the ships of the merchant marine for some time past, and favorable results are claimed for them in point of economy and reduced friction. Fig. 1, Plate 6, is known as Buckley's spring compensating piston packing. Fig. 2 is Lockwood's compound-action piston packing. As to what merits one kind may possess over the other, I aui not prepared to say, since both kinds are favorably mentioned. Buckley's helical spring, as will be seen from the sketch, presses the packing rings outwards and apart, while the Lockwood spring has two distinct actions — one to press the packing ring outwards against the wall of the ■cylinder, and the other to press apart against the flat surfaces, each ac- tion being entirely independent of the other. The latter spring, from the nature of its section, has claimed for it the maximum of strength a.nd elasticity with the minimum of weight and friction. The packing rings are those employed by Mr. John Tarnbull, of Glasgow, which have a continuous cavity around their outer circumference to retain ihe lubricant and moisture from the walls of the cylinder, as well as to reduce the friction. BEARINGS. White brass, as an anti-friction lining for crank-shaft and crank-pin bearings, thrust-bearing collars, and otber surfaces which have been increased to meet high velocities, is found to produce the most satis- factory results, and is now universally employed. The proportionate parts used by D. & W. Henderson, one of the leading engineering firms in Scotland, are, zinc, nine parts ; tin, six parts ; copper, one to one and a quarter parts, one and a quarter parts <5opper being used for thrust-bearing collars. & NAVAL ENGINEERING IN GKEAT BRITAIN. 11 CENTRIFUGAL PUMPS. These are now regarded as absolutely essential to the safety of ships of the navy and merchant marine, and especially in war ships with the great number of subdivisions which the exigencies of naval warfare de- mand. Among the pumps that have given the greatest sadsfaction, and have been accepted as the very best types in England, are those manu- factured by J. & H. Grwynne, of London. Their simplicity of construc- tion, and the reliability of their different rods and crank-shafts, which are made of steel, render their action under any circumstances almost a certainty. Table V shows the favor with which they are received as circulating- pumps. By supplying the requisite amount of water with a pump worked by an engine of high speed, better circulation can be obtained and a more perfect vacuum maintained at any rate of steaming, with a consequent reduction in the proportion of refrigerating surface to indicated horse- power in comparison with the ordinary double-acting circulating pump. It is thought that the pumping power of many of the best merchant steamers would be insufficient in the event of serious accident to one of their watertight compartments, of which there are so few, in considera- tion of their small pumping power. On this subject the London Engineer has pertinently stated that not one ship in one hundred has sufficient pumping pow er on board. Mr. Martell, chief surveyor to Lloyd's Registry, in a paper read at the meeting of tlie Institution of Naval Architects in 1880, gives the names of one hundred and forty-eight cargo steamers that were lost from vari- ous causes during the winters from 1872-'73 to 1879-'80. With some knowledge of the pumping power of this class of vessels, and their small number of wat«r-tight compartments, I am perhaps right in stat- ing that a high percentage of the losses during that period may be charged to inadequate pumping power. Mr. W. H. White, one of the chief constructors of the British Admir- alty, in a paper read before the Eoyal United Service Institution during the past year, gives the pumping power of certain classes of war ships and of several modern merchant steamers as follows: Class of ship. Displacemeut. in tons. M Ill First-class ironclad, not rigged 10, 800 9,000 6,000 4,900 2,640 5,800 6,200 4,700 7,300^ 5, 300 ■ 6,700 ' 6, 700 9,600 8,000 8,000 4,300 2,800 5,500 7,300 4,000 2,600 3 300 2, 500 3,400 4,000 6,500 3,500 2,500 1,400 ■Coast-defender, monitor 1,000 2,600 1,700 ■Troon-aliin 1, 40« ■ * Merchant ships : 600 ' I»o '400 450 Do ,. 900 Do 1 1,100 Do ,.-. 1,200 12 NAVAL ENGINEERING IN GREAT BRITAIN. Besides the great difference in pumping power between the early types of ocean steamers and some of the latest war ships and merchant steamers, there is the difference in the number of water tight compart- ments, which deserves some mention. The Alaska, of the Guion line, has eleven such compartments; the Servia has the same number; the City of Eome has ten, two of these not being carried higher than the main deck. These three ships are the largest ocean going stealers afloat. Among the largest war ships the Italia, of the Italian Navy, has one hundred and fifty water-tight compartments ; the Inflexible, of the > British Navy, has one hundred and thirty-fl%'e, and the Admiral Du- perrez, of the French Navy^i has about two hundred. According to Mr. White, some of the latest ships of the British Navy, have from four to six of their largest compartments amidships bilged simultaneously and yet keep afloat. Plate 7 is a sketch by this gentleman, showing the general arrangement of pumps and the manner of leading the pipes ta the different compartments. Following is the table of references to this sketch : A A. — steam pumps for pumping double bottoms and main drain-pipe. B B. — Main suction-pipe connected witli eacli of tlie steam-pumps. C C. — Stand pipes connected with the main suction-pipe, and communicating with the several compartments of the double bottoms. D D. — Non-retnrn valves in suction-pipe. E E. — Stop- valves. F F. — Discharge-pipe from fire steam-pump. G G. — Main drain-cisterns. H H. — Main drain-pipe. 1 1. — Branch drain-pipe for conveying water from above water-tight compartment to main drain-pipe. K K. — Screw-down valves fitted in the upper cuds of branch drain-pipes and worked from deck above L. W. L. L L. — Screw-down valves iu main drain-pipe for regulating admission of water to tlie main diain. M M.— Sluice-valves in ends of main drain-pipe. N N. — Circulating-pumps connected with main engines. Since it has been proposed to have highspeed passenger steamships running between the United States and England, builders have given some attention to the growing importance of providing more minutely divided water-tight compartments, with a longitudinal bulkhead run- ning the entire length of the ship, and of fitting vessels with greater pumping power than is to be found in many of the steamships of to- day. This needed change, together with the introduction of subdivided cel- lular double bottoms, already adopted by the best builders (see Figs. 1 and 2, Plate 8, Denny's system) will render ships much safer against foundering in the event of any one compartment's becoming bilged. DtlNXOP'S GOVERNOR. One of the best governors for controlling the action of marine steam engines is Dunlop's patent pneumatic governor. It has been fitted to the engines of several vessels in the English Navy and is spoken of in the highest terms by Engineer-in-Ohief Wright, of the British Navy. It completely prevents racing, as will be seen from its principle of construction; and is not dependent for its action upon accelerated speed of the engine, thus greatly reducing undue strains, and wfear and tear of the machinery. Vt m X a o o o c V o o o o b«, V »^ ? k o f n B ;f o S o ;■ S o V o o o ^ s -^ I. 1 ■^ SPEED Uh z BOAT 8 9 IN $0 ADMIRALTY // /o /^ 14. ■ KNOTS if t^ /V" S'/o ! .. ■.^— 560 i 1 1 1 sy« 1 1 r SioO 1 550 \ J . ^ 1 ) 1 ! J 1 54-0 i \ 55 1 1 520 Sio 1 ■ 1 500 1 1 1 f^o 1 1 ' 1 1 \ 1 460 ' 1 i i j 4.70 ! i i ; 1 ^(cO 1 1 1 '^so ; i A i — 440 J , 1 i #30 1 - fzo i 1 4/0 i i 1 ■ - - ■ T i 400 1 ' 1 390 4_.._. 1 ^ C^sec I i ' i ( j;^ 57 3^0 1 { 1 1 1 1 S-S^fl i i 1 I ' ' n ^'^ I ; 1 1 1 rn 520 1 1 1 i '1 '1 1 1 ; i (1 3- nsoo i 1 1 • r -,''-, / 1 ;2^<» 28i> / ' ^J 1 / / 7/ 1 1 270 / 14/1 ^ 2A« 1 ■ ' / // / i T 1 [ // 1 1 / ^M / / I •---i,./ '// // 1 220 1 :// / // CO 2/0 ! 1 // // LlI^^'o 1 1 " i /TT // 19 ! 1/7 y 7' ! 160 i ! - /// /T / n» 1 ^^/f^/ / K,o 1 ^ 1 //// / / ISO V/ //' / ! X tio /I/ If'/ / /so 1 i ''iX ^^)h / /zo ""1 . '//%i y no '^/^ / I too f/j / i VO 1 1 X'^ ¥ X 80 ^ '//J/ y 70 / 1 //^ /^ t,0 -i /^^ 50 /^ 3=rf=i ! 40 ,<»' ^V^ ■^ \ 30 ,< c ^^ ^ 1 i ! i ko c^ "O^ 1 1 1 to 1 ( — — *f^^^ — > A i 1 ) / 2. 3 ^- 5 4 7 e 9 A /s /v > l\ y 1 s a i / 7 5 PER HOUR EXPLAMTION OFOI/KGRm ^CrydC/ iP/Xt^t^-r irCL\AjLi A^ ckjb CAxSt irh~fjnt/ iAiitLti.^ C&fnm^-n.co^ -iu 'bbCaJLi Uti^v irn.^un^uS ^jx Uy^i^JJe-rri , tilt -fixLttuULtOyr^iyi- 'c nuinGtoeac h curve. nESCRIPTICIM CF PRp PEL L E R. C CR.RESP> ; P/rcMoiA'f hi ^aaii ARBA\ SHA PE o r 3LAa£ laio fiat C URVE S SHOWING THE ErnClENCY OF DIFFERENT KINDS or PROPELLERS A T V/\RIOUS gPEEPg YARROW & CO . LONDON bl ^ •» ? I 1-1 ! ■ I :A JrMQri^t^ctrcnir(rCLdZ(r-rL. i r s Sfhuui ^^S^^j^JLajaen'yjinii^ SPEED SCALE -HMS IRIS- ^trnat^v. 30o' W'TCrfudti/^ ^/iaym^tin- n'-/k' ^,'vULcltAy. 4^5' ' PctiJv -Zl^3±' Qe.fvt/v: 27-1' o^yuJUccdjuL Sl6o-r^ty iP^vuv^ --^Sys JIa^^ toi^jmnfi/nu/rLi^ 3C SqJiyoo. ,MoircLi.pjuL &'rxltct*u. ■jtx/yfuUyrs 2 -l&uUi ^TtL.^ -fcrrurw-rxl /;$'-«'' &/^/4- T° T°T "^ ?; =^- >^U£u-n^ on,M^ ,oooZod(s % S 3 S H.EX.D0C.48. ^.M^vxrCutc.^nd. - p f } ^/iuJ ^szs^i:i^r;^zi.i^' 36 4(mjta'>iZ=---j- = s.C^as = 2.6.169 ^^^^^^^^1^ ^1 Jii J(t. If i[i i]i y t|f i)if yi yi ^t ifi If I — If I — i fi ifi - ijfi tf i Mfi ipg ipn fB ■ [» ») rt t fo i p^ [PEEO SCALE — ^^i Ti ci ila/rs oi iMMjL— si^ztc ^txuxL, - — ii'^jt^'yp, i^h^'yp. ^Olcc, yktjirrvci^lib . Si Mft ^rw^^ci^- 1?i-f---. -lS-6i" •Mt. je'.s'-- -16-9" oMevan', - - iS-O^" t^'-7i' @.uUvC^ri.<:c-rn.tyr-vt 4^ timJr SJt2S- ---)iSi5 cHful^kifu ad^iv^; - -.--*757/^ i^Si^ <0'r^/idUr/^itc.k, S1-d- !S/:6' iani<.tt^ /A-6- iW-S' H. EX. DOC. 48 FEEO ^ POWER OIUBVES OyARLES (QiyiNX Tried JD^aiu^/ot , Forwcwci , -^"^/^ Ikins. Afl, 16' 6i' " " AfecL}T.j, 14'W DvsptcvceTrienl i>vlorv^, Z478. Atccl- of 1^ vtivn lyenseci , ^p ft. 42^0. Aizff. Suj^ctce (inchidxnff heel) ^pj'^ .-25266. H. EX. DOC. 48. H.EX.D0C.48. H. EX. DOC. 48. if'-fU£jcLS(^ P^at.trOT,' ^tOfty^ir Z^, ^^^gyrnsAi/l/'t^ ^eot^Z^x^ - 'l^T-iA.etzA'- 3iamv t>^CMli^i.c/Ur>s, — .9W)&r .— - 7Z' -xs' NAVAL ENGINEERING IN GREAT BRITAIN. 15 The adoption of a plan like this in ocean steamers would be a source of much comfort to passengers, since they would know that even if one engine was disabled by serious accident there was still another engine capable of propelling the ship safely at a moderate speed. Mr. William Denny's system of progressive trials, which has been adopted by many of the builders on the Clyde and by the British Ad- miralty, consists in obtaining a regular progression of the different powers from the highest to the lowest, and in correlating this progres- sion with the varying speed of the ship by means of curved lines, of which is given an example in the speed and power curves of H. M. S. Iris, the steamship Eotomahana, built by Messrs. Denny Bros., of Dum- barton, Scotland, and also in the speed and power curves of the steam- ship Charles Quint, built by A. & J. Inglis, of Glasgow, Scotland. (See Plates 14, 15, 16.) Plate 17 is another example of the speed and power curves from a steamer of one of the leading steamship lines of Eng- land. These vessels are the best modelled steamers in the world ; and in point of speed are without superior for the same i)Ower and displacement.. Following, are the leading particulars : H. M. S. lEIS.' Lengtb between perpendiculars 300 feet. Mean breadth 45 feet. Mean draught 18 feet 1 inch. Displacement 3,290 tons. Horse-power 7, 575 Mean speed dnring trials 18. 6 knots. STEAMSHIP ROTOMAHANA. Length between perpendiculars 285 feet. Mean breadth 35 feet 2 inches. Mean draught 15 feet 0^ inch. Displacement 2, 425 tons. Horse-power 2, 907 Mean speed during trials 15. 3£ knots. STBAMSUrp CHARLES QUINT. Length between perpendiculars .• 323 feet. Mean breadth 33 feet 9 inches. Mean draught 18 feet. > Displacement 3, 200 tons. Horse-power 2, 300 Mean speed during trials 15.25 knots. In these trials four or five runs are usually made with and against the tide, and the average of the double run recorded. This plan en- ables any difference in point of efficiency, between different kinds of propellers, to be noted when driven at varying speeds and under differ- ent kinds of trim, both by the head and by the stern, and thus affords a good opportunity to make comparison of results thus obtained with those obtained under normal immersion and normal trim (notably so in the case of the Eotomahana). The best pitch and diameter of propel- lers and the proportion of projected area of immersed midship section* of hulls of ever- varying size and form to the projected area of the pro- peller blades are questions which will be determined more quickly and accuratelv by means of the ascertained data of progressive trials and 16 NAVAL ENGINEERING IN GREAT BRITAIN. the complete history of the particulars attending them than by any ■other method yet made known. It has been frequently stated that the efftoiency of some propellers is much greater at low rates of speed than at-high, and of others, vice versa. One of the best examples iu proof of this belief is the record of the working of six different kinds of propellers, whose respective effi- -ciency at various speeds the English torpedo-boat builder, Mr. Tarrow, *hows by means of curves (see Plate 12). Curve A is produced on the assumption that the horse-power varies as the cube of the speed, com- mencing at 400 horse-power and 20 knots. The other curves represent results obtained by trials of various pro- pellers, the particulars of which are given. Mr. Charles Hall, of the Peninsular and Oriental Steamship Com- pany's engineering staff, London, is at present engaged in investigating the science of screw propulsion, and certainly deserves great praise for his earnest efforts in this direction. His method of experimenting is to drive with small propellers models of steamships by powerful clock- work, the speed of which can be varied to produce three or four ditter- «nt rates of speed. Plate 13 is the curve obtained by Mr. Hall from experiments with the model of the steamship Ravenna, of the Peninsular and Oriental line. He afterwards compared this with the vessel's actual power curve when on its trial trip. These experiments of Mr. Hall's, though not yet completed, serve to show how much importance should be attached to carefully conducted model experiments for the purpose of determining not only the resist- ance of hulls, but the efficiency of propellers as well. MARINE HYDRAULIC MACHINERY. This kind of machinery is now successfully and efftciently applied to various uses in merchant and war vessels of the most recent construc- tion. Through the courtesy of Mr. Peter Denny, of Dumbarton, Scotland, I attended the trial of the steamship Quetta, built by his firm for the British India Steamship Company, and fitted with h, complete set of hydraulic machinery, the design of Mr. A. Betts Brown, of Edinburgh. In the eugiue-room, a pair of engines capable of working above 100 Tiorse-power were employed to maintain a pressure of 700 pounds per square inch the accumulator. From the accumulator pipes are led to all parts of the ship where power is required. The hydraulic power is used in this ship for reversing the main en- gine, which operation is effected with the greatest ease and rapidity, for operating the capstan, for loading and unloading cargo, and for clos- ing the water-tight doors. The hydraulic capstan, situated in the bow, was driven by three hy- draulic rams, equidistant from each other, which acted upon the same crank pin. The hydraulic hoist for loading and unloading is, in principle, the same as that represented in the sketch, Plate 18, Pig. 1. The ram, which has a speed of about 5 feet per second, carries the movable pulleys (A) on a crosshead. The cylinder end has a similar arrangement of pulleys (B). A chain passes around the pulleys, one end beiiig fixed to the cylinder and the other end passing over a jib into the hold. CO o a D X Lul ^P' NAVAL ENGINEEEING IN GREAT BRITAIN. 17 In connection with the winch and hoists are swinging jibs that are suspended from the masts and are used for putting cargo over the side of the vessel. A pair of small hydraulic cylinders and rams are at- tached, one on each side of the mast. Each ram carries a pulley, around which a chain passes, as shown by iPig. 2. Fig. 3 is the hydraulic steering-gear, placed aft for direct connection with the rudder. / Fixed to the rudder-post (A) is the main tiller (B). The end of the tiller is turned cylindrical to allow the sliding block (C) to move rap- idly upon it. This blocli, as will be seen from the figure, is connected by trunnions with the hydraulic rams (D D). A wire cord is carried in each direction from the hydraulic rams to a •quadrant (G), so that any motion which takes place in the rudder-post communicates a similar motion to the quadrant. The simplicity, fewness of parts, absence of gearing, and the prompt- itude, certainty, and silence of action of these machines render them more suitable than steam machinery, when used for like pi^rposes, in cargo and passenger steamers engaged in any trade where much of the loading and unloading of cargo is accomplished during the night time. On board of heavy turreted war ships, hydraulic machinery has now, on account of the great power it exerts so noiselessly, become a necessity for rotating the turrets and for loading, elevating, and depressing the heavier guns. Especially is this so in the case of the Inflexible and the war ships for foreign governments, the machineryfor whichis being made by Sir William Armstrong & Go. For the fast cruisers of the Chinese and Chilian Governments, the same firm constructed the Albini hydrau- lic gun-carriage, a sketch of which is given in Plate 19. The cylinder is divided transversely into two chambers, the pistons being in the lower chamber. Valves are fitted in the divisional diaphragm, which are kept in po- sition by powerful springs capable of being adjusted to any required pressure, and the lower chamber is filled with water. When the gun is fired, the force of the recoil is transmitted through the piston-rod and piston to the water iu the lower chamber. This causes the spring valves to open, and a portion of the water passes through the valves into the upper chamber, where it surrounds the springs. As soon as the whole energy of the recoil has been expended, the spring valves close themselves, the weight of the gun causes it to fall into its original position, and the water which has escaped into the upper chamber runs back through the non-return valves to the lower chamber. In later gun-carriages is applied a design of Mr. George Eendel's, which facilitates the training of the gun. It consists in operating the carriage by two oscillatory rams placed at right angles with each other. BOILERS. By the best engineering practice in Scotland, boilers of the cylindrical type are now made with about 2.88 square feet of heating surface and 0.102 square feet of grate surface per indicated horse-power. The pro- portion of heating to grate surface averages about 26.89 to 1, as will be seen by Table IV. H. Ex. 48 2 18 NAVAL ENGINEERING IN GREAT BRITAIN. o o> t> o t- t- t- i2 g i^ir e ir S E o CC s j9J4.od-o9jOTi pa^^o -ipui JO uoi^odojj oi 00 oi OD o> o o 'j9Jiiod-9ejoti p9!^B0Tpat 0^ ao-Ejane Sni!('eeq jo noi^odoj; j (N CO cjn cj c4c4 C" SB SujlB9ii JO uoi:jJodoad[ er & s in CO CO CO o 00 C£ CM 58 to OOlBJjnS 3nt!^'B9T[ l-Bi^QX O O OO O ■fl'-^ 1= 00 >~t CO t- 11<'9t O U3 00« ^ OCO CO o o i O CO iri" T-t C =r ■;^99j erenbe w t- CO io M w CO CO c: o CO in CC i s s i -j9Aiod-9eioq pa^'BOipaj CO CO mo m c-Ctt ir CO o g • o CO o o CO- •!ja9j 9J'Bnbe ni 'ESJl'B SBOJO tn «?CO lO t-to t- CO CO CO CD in CO CO t- ■saqoni HI J9^9td'Gia; CO CO CO CO CO c; CO CO He CO COCO CO " " " -tn CO cr CO N ■joqran^ M « ■»* -* OS 00 CX) iH m N >n CO tH ri a s ^ a CD CO CO r-t •B9qont ai ee9n^'oiqx rw -«« HW^H r«m .r*«nW 1 1 CO EC ^ H- r*l ^ ,*1 ft*: o CO -4n .*• •B9qoni pU-B 399J CO CO OJ 00 OO CO CO "J- CO CO NM CO a- cr CO COCO CO II £1 CO CO CO CO d ■s o •Boqom ni Bsaujioiqx 1 II CD a; cc •>* a IH 1-1 ^nH II - c-to u5oooa» c CO o c III bo 43 : 'jj o ^ -J3 d d -eejoq p9)'Boipiii -[000 JO aoi'^iodoj J ■^9aj -JOB Sni^ooo I'B+ox ■^OOCOtOOOOOOOTf*J«SOt-COOOOO-^ «Dciaipir-iosi-iioo)oe(icoc <0 lA iH ea 04 C4 CO o o o s <=i •=> o o 0-* m o '199J nt 'QTlOl^S JO TI(j3a91 IS C00D00e400C40>0DOD-0000OC0a>C0O<0t>t H H o o o .- 6" © d" n" fr-" HHHoa H H Hg|^ H H o o o H HH 20 NAVAL ENGINEERING IN G"EEAT BRITAIN. In the merchant marine, the single and double-ended boilers are generally adopted with two, three, and sometimes four furnaces in each. The double-ended boiler is generally used in ships of large boiler power, where there is plenty of room, in a fore-and-aft direction ; and, according to the experience of Mr. Marshall, is 10 per cent, more economical than the single-ended boiler. In the British Ifavy, the most recent cylindrical boilers are single- ended, with two or three furnaces in each boiler. When the amount of available space in a war ship will permit, the boilers are placed back to back against a longitudinal bulkhead, and the fire-room containing them is traversed by transverse bulkheads so as to divide it into watertight compartments, usually four in num- ber. Plate 20 is a sketcTi of a locomotive boiler such as is used in large war ships to utilize the advantages of forced combustion. Plate 21 is a sketch of the boilers of the Chinese and Chilian cruisers, known as the " navy type." The most recent boilers are designed to carry working pressures as high as one hundred pounds, and the tendency io to go even higher. Mr. Kirk has constructed a set of steel cylindrical boilers for a con- tinuous-expansion engine, already referred to, which carry 12.5 pounds working pressure per square inch. The average working pressure of a large number of the most recent boilers constructed by the leading Glasgow iirms, as will be seen by Table VI, is 77.5 pounds per square inch. See also Table Y, by Mr. Marshall. Table VI. Diameter of oylinders, in inchea. « t, i Higli pressure. Low pressure. 1 2 47 82 2 .t4 94 SJ - 42 80 17 4 Two, 44 Two, 82 IS •> 73 120 19 2 72 120 4 3 63 Two, 90 .5 •■! (50 Two, 85 6 H 68 Two, 100 20 4 Two, 48 Two, 83 21 2 48 90 24 2 44 80 11 3 64 Two, 80 14 4 Two, 60 Two, 104 25 6 Two, 58 Two, 74 o. a 5.5 5 6 5 4 4 3.5 3.9 Crank pin. Diameter, ^"^l?"^' "5, in inches. inclies. <] Steel, 2 I 15.ii 13 15 20 2 1 20 1 2 20 I 3 23 ; 3 21 ! 3 I Steel, 25 i 3 I 20 ! 15* 14.i 21 3 ' 4 ; 6 ! 21i 19 j 16 1 15i 18 , 18 25 i 22 I 22 24 21 26 21} 16 16 164 I 18 Main journals. Diameter, Length, in in inches. inches. 90 90 90 90 120 120 120 90 90 90 90 120 Steel, ^^ \ Two, .., I Two, "* \ Two, Four, 18 15 : 20 20 20 20" 24 19 15 14 ; ; Three, I One, „,. f Xwo, -^' 1 Three, 16J. 21 35 i«4 27 19} ' 33 38 33 i 33 i 26 23 39 i 28.5 19i i 18 i 32J ; 75 75 75 90 75 100 70 7S 80 For boiler construction, mild steel by both the Bessemer and Siemens- Martin process is, as far as my observation extended, meeting with equal favor both in England and Scotland, the superiority of one make over another, when it does exist, depending upon the quality of the pig metal and the efiBciencj'^ with which the whole operation is conducted. o o o oj ^ € 00 o o Q NAVAL ENGINEERING IN GREAT BRITAIN. 21 The superior strength and homogeneity of steel not only permits a higher working pressure with a greater margin of safety than an iron boiler, but also effects a saving in space occupied for a given power, which is accompanied by a saving of fuel. The practice of welding the back tube plate to the furnace, and the longitudinal seams of shell plates and furnaces, has been attended with success. At the works of Messrs. E. Napier & Sons, I have seen steel furnaces for the new cruisers welded their entire length with no more difiicalty than if they were of iron. Those who have made this practice a spe- cialty claim that by it furnaces and shells can be made more nearly cir- cular, and by a reduction of the joints corrosion and wasting from leaks, so common in the bottoms of boilers with seams, is prevented. The method of welding thick shell plates, as accomplished by one of the leading firms, is done by beveling the edges of the plates to an angle of about forty degrees by planing. The edges of the plates, after being heated to a degree sufficient to insure good welding, with a bar of the best low-moor iron between them, are, by the aid of a quick working steam hammer, firmly united. Furnaces and combustion chambers are now liiade larger with bene- ficial results by the attainment of more perfect combustion. In some cases it has been necessary to contract the mouths of furnaces to ob- tain the requisite grate area, as shown in Fig. 1, Plate 23, as has been done in the boilers of the Eussian war ship Peter the Great, and the steamship Arizona, of the Guion line. One of the most recent additions contributing to the efficiency of the high-pressure marine boiler is Fox's corrugated flue (see Fig. 2, Plate 22), made by the Leeds Forge Company, Yorkshire, of a soft grade of Siemens mild steel by means of special machinery which renders them truly cylindrical. It has claimed for it greater strength by 100 per cent, than the ordinary flue; greater evaporative efficiency and economy, owing to the reduced thickness of the metal; extra heating surface presented by the corrugations ; absence of undue strain from unequal expansion common to plain flues; elasticity in the direction of the length of the furnace, which, by the slight opening and shutting of the corru- gations at the different temperatures of the boiler, prevents any incrus- tation from attaching to the corrugated flues. Tests of the metal composing the flues, made by Professor Kennedy, of the University of London, gave a breaking strain varying from 26.54 to 27.56 tons per square inch, with extension, on the eight- inch length, of 22.5 to 30.2 per cent. ' The boilers of the steamship Servia, of the Cunard line, built by James & George Thomson, of Glasgow, have thirty-nine corrugated flues 4 feet in diameter, 6 feet 6 inches in length, and y'^ inch in thickness. The steamship Alaska of the Guion line, built by John Elder & Co., of Glasgow, has fifty-four corrugated flues; diameter, 3 feet 9 inches; length, 6 feet 8 inches ; thickness, j\ inch. They have been introduced into two ships of the British Navy, and into many merchant steamers, with results, as far as 1 could asceitain, which were very satisfactory. Unequal expansion, due to difference of temperature of water in high pressure cylindrical marine boilers while steam is being raised, which has always been a source of .more or less trouble and expense to engi- neers and steamship owners, Messrs. 0. & J. Weir, of Glasgow, over- come by a hydrokineter or water-circulator, by which a current is in- S2 NAVAL ENGINEERING IN GREAT BRITAIN. •duoed for the purpose of equalizing the temperature of the water in the t)oiler. The hydrokineter is now successfully used on all the boilers of the -Peninsular and Oriental line, the State, and other steamship lines. Fig. 1, Plate 23, is a section of the three-nozzle hydrokineter. The flange of the first or steam nozzle is fixed on the inside of the "toiler shell, and set in the direction the circulating current is to take. On this nozzle are fixed two outer or induction nozzles, and the back •«nd of the one and the outer ring of the other are perforated to admit water between. Steam from the winch boiler is admitted by the check and stop valve a (Fig. 2) to the steam nozzle, and being condensed, throws a jet ■of water through the second nozzle. The volume of water is increased in passing through the outer noz- -zle. It then enters the bottom of the boiler and induces a current, as «hown by the arrows in Fig. 2. The purpose the two outer nozzles .«erve is more effectually to direct the force of the jet in the direction in which circulation is desired. i When a jet of steam is introduced, the water in immediate contact •with it, becomiug heated, expands and impairs the force of the jet. "With the three-nozzle arrangement this is obviated. The water being directed on the steam-jet, the steam is condensed 'between the first and second nozzles, until the temperature of the water Teaches about 170°. The outer nozzle then comes into play as a condenser, keeping the -«team from expanding, and directing the jet straight into the water in ® ® ® • .§ n-$ -«^^. a ® " ® ® ^ ft h^aS; ^ ^ T* eo II II II :« 'fi , P CO S a ^^ V " is JS o ^ • i eg-" ■s ■: i-H ai O OS O I to ' (O M rt CM ■f-i CO ■ga go CO «oo S-iJtCD II II cei t- ^ E3S - ft * w ■ g .-aP-oS ■S t,T r-\ r^ r\ ■i>a) ■* ooo . "* ■>*- O iH CO ~ O) CO ^ II II oo . O I— ^o to §^g'S' B> n ^

< 15 a p « *%J^ ^ H M (S X § i a 1 O <-> g w ■£ 'e3 u 's 1 H 13 M R i?i Oi •g "fe> (45 2 r^^\ r-\/'~\ ' \ \ 1 ss^; 1 OtO 1 ©t© . H s o o I © ® 1 Sao o DO 5 « (M -t-co -C » CO ^ +5 Ti ^C-l d *^ h<^ •^\nm . in t~ t- w . . . s: ci c^ o ooo . o in m NAVAL ENGINEERING IN GREAT BRITAIN. 27 PS II II lo o irf dbii 3 ■s 3« 5 bo a 1^ is «•- .a ft 5g, £3 ^ I" i s "* Is a-9 II' •a ■2 ® a & s HI o" O 28 NAVAL ENGINEERING IN GREAT BRITAIN. Table X. Report C. — Summary of ike results of experiments to ascertain the elastic and ultimate tensile strength of spedmene cut out of steel riveted joints received from Messrs. Denny f Co. [Nomiual tMcknees, seven-eiglitlis inch.] LENGTHWISE. Pieces cnt (»ut of riTeted joint. N 3426. N 3422 . N 1406. N 1430. H 3474 s Extension-fset in S * ten inches. 3 1 O rt a eg P. P. _g t ^ & (S Q s* "^S B'o ■43 o.g o2 1 1 o g o P,g o « S ^ 1 p 1 1 m 1 o 1 O Lbs. 5 a ■s N. Inch. lAs. Tons. Lbs. Tons. P.ct. P.ct. p.ct. p.ct. P.CL 1420 .88 33, 700 61, 980 54.3 37.2 98, 807 1.89 6.94 28.6 1419 .87 Mean . . . .87 32,900 60, 820 54.0 35.8 94, 741 2.92 6.61 27.7 33, 300= 14.9 61, 400= 27.4 54.2 36.5 96, 774 2.40 6.27 28.1 1428 33, 800 61, 410 65.0 26.8 91, 793 1.72 1 5.92 23.« 1427 .85 Mean . . . .87 33, 500 60, 925 64.9 38.6 99,302 2.45 6.68 1 27.2 33, 650= 15.0 61, 167= 27.3 55.0 32.7 95,547 2.08 6.30 1 25.4 1424 33, 500 61, 130 64.8 39.1 100, 534 2.78 6.32 27.1 1423 .86 Mean . . . .88 83, 500 60, 375 66.4 45.5 110, 945 2.78 6.39 1 29.3 33, 500= 14.9 60, 752= 27.1 55.1 42.3 100, 738 2.78 6.35 28.2 1407 36, 500 62, 590 58.3 37.0 99, 420 1.42 5.48 : 27.2 1408 .87 Mean . . . .88 35,300 60,410 58.4 34.5 92, 366 2.90 6,6a 26.4 1412 35, 900= 16.0 61, 600= =27.4 68.3 36.7 95, 893 2.16 6.05 1 26.9 33, 600 63, 310 53.0 38.9 103, 747 1.41 1 5.78 ; 29.2 1411 1431 .90 Mean . . . .87 33, 600 62, 480 53.7 42.3 108, 346 1.41 6.07 1 29.8 33, 600= 15.0 62, 895= 28.1 63.4 40.6 106, 046 1.41 6.92 ] 29.5 33, 600 61, 086 54.8 42.4 106, 079 2.62 j 6. 00 i 2a « 1432 1416 .89 Mean . . . .87 32, 800 60, 310 54.3 47.2 114, 437 2.91 6.62 1 29.6 33, 150= 14.8 60, 697= 27.1 54.6 44.8 110, 258 2.76 6.26 29.1 35, 500 63,396 55.9 46.2 117, 849 0.33 5.25 32.7 1415 .86 Mean . . . Tot. m'n 35, 200 63, 370 55.5 36.5 98, 371 0.40 6. 41 28. 1 35, 350= =15.7 63, 382= =28.2 55.7 40.8 108, 110 0.36 6.33 30.4 34,064 = 16.1 61, 685= =27.1 55.2 39.0 101, 909 1.99 6.07 ,28.1 Appearance of fi'iicture, 160 per cent. eilt)'. NAVAL ENGINEERING IN GREAT BRITAIN. 29 CROSSWISE. Stress. i £ 1 1 Bxtension-set in ten inches. ' •§ 1 IS ■3 s £ S? S! Pieces cat out 3 g- 5 .S| p. P< of riveted .S c8 ^ g3 !l joints. 1 a oi IS . ■3 O 3.13 g^£ a t s 3 1 1 i s" s" i B Inch. Lba. Tons. , u M o i6«. p.ct. <( ' N. Lbs. Tons. F.ct. P.ct. p.ce. p.ct. N 1418 1421 .875 36,800=16.4 63, 055=28. 1 58.3 43.3 111,235 1.32 4.52 22.6 K 1426 1429 .860 36, 300=16. 1 61, 105=27. 2 59.4 26.5 83, 214 1.84 5.11 19.2 Jf 1422 1425 .865 34, 700=15. 5 61, 310=27. 3 58.5 31.0 88,906 2.42 5.69 23.8 M" 1406 1409 .875 37,600=16.7 63, 160=28. 1 59.5 22.2 81,272 0.46 4.54 16.3 N 141U 1413 .890 37, 800=16. 8 63, 595=28. 4 59.4 36.4 99,999 0.39 4.41 22.1 N 1430 1433 .880 34, 900=15. 6 60, 160=26. 8 58.0 44.8 109, 155 2.31 5.72 23.7 l«f 1414 ,.. 1417 .865 Tot. m'n 38,400=17.1 63, 790=28. 5 60.1 24.0 83,984 0.25 5.02 19.1 36,643=16.3 62, 310=27. 8 58.7 32.6 93,966 1.28 5.00 2«.9 One hondred per cent, silky. DAVID KIRKALDY, 99 Southwark street, London, S. E., May 28, 1879. Mos-srs. Denny & Co., Enginaers, Dumbarton. Copy o/parliculars received from Messrs. Denny ^ Co. »ESCR1PT10N OP RIVETED JOINTS SENT FOR TESTING TOD. KIKKALDY, KSq., BT MESSRS. DENNY * CO. The uumber of specimens is seven, marked, respectively, 1, 2, 3, 4, and A, B, C. The rivet holes of those marked with figures were drilled separately with an l-j'j- inch drill. The plates were then heated as the boiler plates themselves would be foe rolUng, and after cooling were put together and the holes reamed out to H incli diameter. The rivet holes of those marked with letters were pnnched separately with a punch i inch diameter on a die 1-^ inch diameter. The plates, after heating and cooling as above, were then put together and the holes reamed out to H inch diameter. All the samples were riveted together the full width of the plates (24 inches), and ^reie then slotted out to the shape for testing. Riveting all done by a steam riveting machine. Dumbarton, March 24, 1879. DENNY & CO. David Kirkaldy, 99 Southwark street, London, S. E., May 29, 1679. 30 NAVAL ENGINEEKING IS GREAT BBITAIN. Table XI. Report D. — MeeuUs of experiments to ascertain the elastic and ultimate tensile strength ani qvality of the steel rivets used ly Messrs. Denny 4" Co. in steel riveted joints. p„i Original. Stress. o Fractnred. S£ 1 ■43 "1 li Differeuce. o Test No. 1 ■? (3© «r.S II f f 5 . < -5 f4g Stresi) -D inch of area. p. 1 N. Inch. Lis. Tons. id*. Tons. Pr. cent. In^h. Sq. in. iTUih. Lis. 1435 .798 .500 37,400=16.6 69, 680=31. 1 63.6 .69 .273 .227 45.4 127, 619 SUky. 1434 .798 .500 37, 100=16. 5 67, 410=30. 1 55.0 .52 .212 .288 57.6 158, 995 Do. 1437 .798 .500 36,500=16.2 64, 240=28. 6 56.8 .49 .188 .312 62.4 170, 861 Do. 1439 .798 .500 36, 200=16. 1 63,880=28.5 56.6 .49 .188 .312 62.4 169, 893 Uo. 1436 .798 .500 34, 800=15. 5 62, 460=27 9 55.7 .48 .181 .319 63.8 172, 541 Do. 1438 .798 .500 33, 300=14. 8 61,370=27.4 54.2 .48 .181 .319 63.8 169, 630 Do. 35, 883=16. 64, 840=28. 9 55.3 59. 2 161. 571 1 NominaX size of rivets and corresponding number of riveted joints. — Diameter. -^ inch : N, 1418, 1426, 1422, 1406, 1410, 1430, 1414. Extension. — Too short for ascertaining theextension. Messrs. Denny & Co., Engineers, Dumbarton. For high-pressure marine boilers the direct spring-loaded safety- valve, which is now used in preference to the deadweight safety-valve, has been adopted by the Board of Trade in England. (See Plate 24.) Silicate cotton and asbestos are about the best compositions used to prevent boiler radiation. The most recent asbestos boiler covering is made of refuse asbestos mixed with a small quantity of flour and alum. In some cases a slight amount of sawdust is used to make it elastic and more adhesive. It is put on in three layers, three-eighths of an inch thick, after tlie boileris thoroughly dried. AETIFICIAI COMBUSTION AS APPLIED TO WAR-SHIPS AND TOB- PEDO BOATS. The system of forced combustion, which is attracting the atten- tion of the foremost engineers with a view to its application to mer- chant as well as naval vessels where speed is the desired object, was, according to Prof. E. H. Thurston, introduced many years ago by the late R. L. Stevens, and also used in large naval steamers by Pro- fessor Thurston himself when an engineer ofiicer of the United States Navy, as stated by him in his description of the Stevens battery. Mr. John I. Thorneycroft, the distinguished torpedo-boat builder of England, by putting the system into practical operation in the yacht Gitana (built by him in 1876), first demonstrated what could be 'practi- cally attained by means of forced draught. He used a fan-blast to force air into an air-tight fire-room. It is upon the studied application of this system that Messrs. Thorneycroft & Co. and Messrs. Yarrow & Co., of London, have built so many fast torpedo-boats for foreign gov- ernments. Messrs. Hanna, Donald, Wilson & Co., torpedo-boat build- ers of Paisley, Scotland, have used the same system in torpedo-boats and in a small passenger steamer (about 130 feet long) with an excellent effect with respect to speed. m X a o o "•^ NAVAL ENGINEERING IN GREAT BRITAIN. 31 It has been introduced in two cruisers recently built from the designs of Mr. George Kendel (of Sir William Armstrong & Co.), for the Chi- nese Government, and in one for the Chilian Government, with most satisfactory results on trial. The principle is in use in the torpedo-ram Polyphemus, and is to be adopted in the Leauder, one of the three fast steel cruisers which Messrs. E. Napier & Sons are building for the English Government. It will be adopted in the new turret-ship for the Government of Brazil, now in course of construction by Messrs. Samuda & Co., of England, and in several vessels to be built for the English Government, In which speed is the desideratum. In torpedo-boats, the system consists in closing in, air-tight, the en- tire space about the boiler — one of the high-pressure locomotive type. (See Plates 25 and 26.) The centrifugal ventilator-fan is usually placed against the bulkhead^ and takes air for the fire-room from a pipe or cowl, having communication with the deck, and, forcing the air into this closed space or fire-room,, causes it, as its only mode of exit, to pass under and through the fur- nace to the uptake, thus creating the artificial air current so necessary to produce the quick combustion required to develop the engine-power of these boats, which is unusually high in comparison with the displace- ment of the boat. In one of Messrs, Yarrow & Go's second class torpedo-boats, with the fan making 1,200 revolutions per minute, there was attained in the fire- room an air-pressure equal to the weight of a column of water 4 inches high. The extent of the pressure, however, depends very much upon the tightness of the compartment, quality of fuel, manner of firing, and the length and diameter of the tubes. Mr. Thorneycroft, in describing the unusual proportions of the blow- ing-engine of the yacht Gitana, gives the combined length of the main bearings as 18 inches, diameter 2 inches, while the diameter of the steam- cylinder is only 5 inches. The crank-pin is 4 inches long by 2 inches in diameter. With this engine, a speed of 1,700 revolutions per minute or 50 strokes per second was obtained. Upon Mr. Thorneycroft's kind invitation, I attended the official trial of a second class torpedo-boat, built by his firm for the French Govern- ment. • During the trial I availed myself of the opportunity of being in the fire-room while making the run over one measured mile. With the air-pressure in the fire-room equal to a column of water 3 or 4 inches high, I experienced no unusual sensation from being in an atmosphere above the normal density, and found the temperature but a few degrees above that of the outside atmosphere. In the bulkhead separating the engine-room from the fire-room is a side light. Fixed to this bulkhead is an apparatus of simple construc- tion arranged to indicate the pressure of air in the flre-room, with a communicating pressure-gauge in the engine-room. To avert the danger to the lives of the men employed in the closed fire-room from the bursting of tubes and the consequent rush of steam into the flre-room, Messrs. Thorneycroft & Co. provide self-closing ash- pit doors and also a passage to the deck to facilitate the escape of o+^o in For the same purposes, Mr. Yarrow has patented a special arrange- ment which is adopted in all those torpedo-boats of his construction^ which have their boilers placed in an hermetically closed fire-room. The 32 NAVAL ENGINEERING IN GREAT BRITAIN. arraDgement consists in fixing an extra bulkhead around the fire-box part of the boiler, and hermetically closing the ash-pit from the fire- room side of the compartment. To admit to the boiler the necessary air forced by the ventilator-fan, holes, twenty inches in diameter, are cut in the bulkhead at each side of the boiler. These boilers are provided with a light valve or flap hanging on hinges on the side of the bulkhead opposite to the fire-room, where, also, is the ash-pit, which is left open. By the action of the fan, forcing air into the fire-room, the holes in the bulkhead are kept open and freely admit air to the ash-pit, and from there it passes to the furnace. (See Fig. 31.) In case of any of the tubes bursting or of other damage happening to them, the steam from the boiler, rushing into the ash-pit and forcing its way toward the fire-room, overcomes the comparatively insignificant air-pressure in the fire-room, shuts the valve against the bulkhead, and thus closes the only channel by which steam could enter the fire-room. The steam can, therefore, only accumulate on the ash-pit side of the bulkhead and must return through the furnace tubes, and ultimately escape through the funnel. Following are the results of some experiments recently made by the English Admiralty for the purpose of determining the evaporative effi- ciency of the boilers of a first-class torpedo-boat under different press- ures of air in the fire room : Pressure of air in the fire-room, in incbes of water _ . Pressure of air in the ash-pit, in inches of water Pressure of air in the furnace, in inches of water Temperature : On deck °F.. Of furnace °F.. Of feed-water °F.. Of funnel "F.. -Steam -pressure, in pounds per square inch Eevolmions of fan per minute - Coal used per hour, in pounds 'Coal used per hour per square foot of grate, in pounds Water evaporated per hour, in gallons Water evaporated per hour per square foot of grate, in gallons Water evaporated per pound of coal, in pounds W ater evaporated per hour, calculated from 100° feed- water, in gallons Water evaporated per hour per square foot of fire-grate, calculated from 100° feed-wator, in pounds Water evaporated per hour per pound of coal, calculated from 100° feed- water, in pouuds Total evaporation per hour, [reduced to pounds of water from 100°] at 212°, in gallons Evaporation per hour per square foot of fire-grat«, [reduced to pounds of water from 100°] at 212° Evaporation per hour per pound of coal, reduced to pounds of water from 100° at 212° Thickness of fire at mouth, in inchos Thickness of fire at back, in inches 1.47 1.35 464 75 53.5 1, 073. 5 117 575 925 48.94 653.5 34.5 7.08 , 680.7 360 7. 35 704.6 372.6 7.61 3i F-J ^ ■c a 03 ^ ^ 4 6 3.26 5.25 49i 78 54.5 1,260 115 818 1, 472 • 77.88 932.5 49.3 6.33 970.5 513.4 6.58 1,004 531.4 6.81 4 11 4.33 58 82.0 56 1,444 115 986 1,815 96. 03 1, 084. 1 57. 3 5.97 1, 126. 8 596.1 6.2 1,166 617.1 6.41 14 I 3 2.29 1.87 57i 85.3 57.5 1,192 117 665 1,177 62.2 777 41-1 6.6 806.6 426.7 6.84 835 441.7 7.03 54 14 The same system (that used in torpedo-boats) as carried out in larger vessels, such as the torpedo ram Polyphemus, and the large ships al- ready mentioned, consists in making the space between the skin of the ship, the deck, and the bulkheads which form the boiler-rooms practi- cally air-tight. KAVAL ENGINEERING IN GKEAT BRITAIN. 33 Tlie boilers of the Polyphemus are of the locomotive type, ten in number, and divided into two groups of three and two respectively, with a fore-and-aft bulkhead between the groups, which forms four fire-rooms in water-tight compartments, with the uptakes all leading into one chimney. The boilers of each of the Chinese and Chilian cruisers are four in number, of the English Navy pattern, similar to those of the Comus class and are placed in a fore-and-aft direction. The absence of hatches in these ships allows a coal-bunker to be ■carried over the entire length of the air-tight boiler-room. Entrance to the fire-rooms of the larger ships is gained through a passage or entry closed by two doors with India rubber joints. The space between the doors, which open iuwards, is sufficient to contain a man. Situated above each compartment of the fire-room of the Poly- phemus is a. Brotherhood engine, which draws air through a ventilator pipe and discharges into the fire-room below. Each fan engine is ca- pable of giving the fan fifteen hundred revolutions per minute, and of supplying air to two fire-rooms in order to provide for the contingency of one engine breaking down, the air in this instance passing through a door in the division bulkhead. This door, which is of glass, permits the attendants in each fire- room to have a general knowledge of the work going on in the room adjoin- ing, ard also furnishes a ready means of escape in case of accident. During a recent trial of a portion of the boilers of the torpedo ram Polyphemus, the temperature of the fire-room was 100°, while the tem- perature on deck was 80°. The practicability of causing the fan-engine to draw^ air from the en- gine-room and of having a constant current and change of air has been suggested for the purpose of escaping from the excessive and uncom- fortable heat of the engine-room, experienced during the active maneu- vering of the ship. This system of forced combustion which, in fact, would seem an al- most absolute necessity in modern war ships, has many advantages claimed for it when applied to larger ships, as well as torpedo boats and torpedo rams, and especially at the critical moment when the power must be kept at the maximum, as in ramming and in quick evolutions. ■Quick and effective work at such times is, to commanding officers, of prime importance. The present great hatchways, fire-rooms, and engine-rooms, so neces- sary to natural combustion, could, by the system of forced combustion, be dispensed with, and thus would be prevented all possibility of shells damaging the machinery. The space occupied by hatchways in ships dependent upon natural combustion could be utilized in handling the long guns now coming into use. > Smaller boilers could be used, leaving greater space for bunkers along the sides and over the fire-rooms, as in the Chinese and Chilian cruisers. These bunkers provide not only greater coal capacity, but also, when filled with coal, greater protection to the vital parts of the ship, With this system, the height of the smoke-pipes could be greatly re- duced in fast cruisers ; and in torpedo-boats and rams the smoke-pipe could be dispensed with by delivering the products of combustion through suitable openings, controlled by dampers, at either side or at both sides, just below the deck as has already been done by Messrs. Yarrow & Co. in some of their late torpedo-boats. This plan carried H. Ex. 48 3 34 NAVAL ENGINEERING IN GREAT BRITAIN. out in boats low down in the water, using anthracite coal, would prevent the smoke from betraying the boat's position to the enemy ; and would do away with the high smoke-pipe, which is so objectionable on ships of war. Goals of inferior quality could be used ^frithout materially re- ducing the power of the boilers. With steam in one of the auxiliary boilers to work the centrifugal ventilating fans, steam could be quickly raised in the remaining boilers— a mattet of vital importance in war time. As to the cost, under ordinary circumstances, of producing a forced draught, I would refer to a paper read by Mr. Josiah McGregor before the Society of Engineers and Ship-builders during the year 1879. After considering that it takes about one quarter of the available heat of combustion to produce a chimney draught, and that this heat goes to waste up the chimney, he states that the temperature reached by a fire produced by natural draught is about 2,240°, while with forced draught and with half the quantity of air for dilution, the temperature is 3,200°. By the following formula, he expresses the power required to supply artificial draught to boilers in order to indicate about fourteen hundred horse-power — using a grate area of 50 square feet and burning 56 pounds of fuel per square foot of grate per hour, or .0155 pound per second, with an air pressure equal to 3 inches of water or 16 pounds per square foot — P = pounds pressure = P ro ..0155 X 225 X 511 w = fuel per second = 16 2.93 2 Vo = volume of air at 32°, per indicated horse-power, 57.8 foot'pouuds. 57.8 X 60 X 50 33000 X 2 =10.5 H. P. r = absolute temperature of air = ro = absolute temperature of Vo. c = coefficient, say = 2. In the same paper Mr. McGregor gives for comparison the following dimensions and weights of two boilers of nearly the same power, one of the cylindrical type and one of the locomotive type : Diameter Length rnrnaoe Thictness of shell Thickness of furnace Grate area Total heating surface Working pressure Water-steaming surface . . . Weight of boiler Weight of water in holler.. Weight of super-heater — Type of boiler. Cylindrical. Sfeet 9 feet 5 inches 2 feet 9 inches diameter. . § inch J, inch... 55 square feet 1,445 scfuare feet 80 pounds 128 square feet 19 tons 11 tons 8 cwt 1 tonl2owt LocomotiTe. 4 feet 9 inches. 15 feet 5 inches. 4 feet li inches by 6 feet. g inch. § inch. 50 square feet. 1,48S square feet. 80 pounds. 133 square feet. 12 tons 10 owt. 9 tons. 1 ton 12 cwt. From the foregoing it will be seen that the locomotive boiler con- tains 2 tons 8 cwt. less water than the cylindrical boiler, and is seven tons lighter. The great difference in height between the two types is another no- ticeable point worthy of consideration iti war-ship construction. The torpedo ram Polyphemus, with locomotive boilers and forced NAVAL ENGINEERING IN GREAT BRITAIN. 35» draught, is designed to develop 5,500 horse-power, while the Leander and its class, with the ordinary single-ended cylindrical boilers, are de- signed to develop 5,000 horse-power with natural draught; and perhaps. 5,500 horsepower with artificial draught. I have roughlj- estimated the cubic space occupied by the boilers of" both the Polyphemus and the Leander, and find that the boilers of the latter occupy something like 9,000 more cubic feet than those of the former, while the Polyphemus' boilers have also the advantage of being, placed some 5 feet below the load water line. Mr. P. C. Marshall, of the firm of R. & W. Hawthorne, of Newcastle- on-Tyne, who recently constructed the machinery and boilers for the Chinese and Chilian cruisers, designed by Mr. George Eendel, of Sir William Armstrong & Co., has given the following results of the trials : With a pressure of air represented by 2 inches of water, the indicated horse-power of the engines was 2,800 as against 1,875, when working- by natural draught. The boilers, as before mentioned, are of the navy type, and made throughout of Siemens-Martin's mild steel, and riveted with steel rivets. He gives the following table for the purpose of comparing these boil- ers with the ordinary double-ended iron boilers used in merchant steam- ers, in regard to weight and power under different conditions of draught : Weight in tons HoTse-power — UTam^nt Donble- ended. 135 1,400 Natural. Navy. 146; 2,76a PoToed. The expediency of applying this principle to passenger steamers, where high speed for continuous steaming is of the first importance, is receiv- ing the attention of some of the leading Scotch engineers. For land purposes, where space is of secondary importance, it would seem that the high chimneys built to produce a natural draught, could be dispensed with and forced draught sub^stituted, perhaps, with. economy. TORPEDO-BOATS. Torpedo-boats built in England are classed in two divisions, known respectively as first and second class. The first class, being intended for attacking from the shore, or other fixed base, have a length usually of 100 feet, but extending sometimes to 110 feet. The second-class are smaller, being from .60 to 70 feet in length. This length admits of their being carried on shipboard or in a store-ship specially fitted up, to carry a number of them, together with a supply of torpedoes and their amu- nltion. Following are the dimensions and description of one of Messrs. Yar- row & Co.'s small torpedo-boats built for a foreign government (see- Fig. 31).: Length on water line 71 feet 3 iacliesi Breadth 9 feet. Mean draught, loaded, without propeller 3 feet 3 inches. 36 NAVAL ENGINEERING IN GREAT BRITAIN. Mean draught, loaded, with propeller 3 feet 7 inches. Displacement with torpedo-gear, coa], and equipment on beard 23 tons. Indicated horse-power 280. Weight of machinery, with water in boiler 10^ tons. Weight of hull — about 6 tons. Speed in knots 16. Diameter of propeller 5 feet 2 inches. Pitch of propeller 4 feet. Materi-al of screw Steel. The boat is built of steel. The deck above the boiler and the look- out (a) are covered with plate steel ^% and ^\ inch in thickness, which has been proved by experience to be (under normal circumstances) im- pervious to rifle balls at the shortest range. The hull is divided by water-tight bulkheads into six compartments, as follows : First. The stern aft compartment for the captain and steersman. Here is the steering-gear, and above it the tower or lookout on deck. Speaking tubes lead from this compartment to the engine-room, boiler- room, and torpedo-room. Second. The engine-room compartment. Third. The boiler compartment or fire-room. Fourth. The torpedo compartment, in which is the gear to work the bow spar-torpedoes. Fifth. The chain locker, for stowing anchor chains and various ship stores and gear. Sixth. The foremost, a very small compartment which is designed to prevent leaks in the chain locker and torpedo compaitmeut, and the more probable damage which the boat may receive by striking with the stern. The bulkhead on frame Xo. 14, through which goes part of the boiler, is not quite water-tight, but can be made practically so if constant attention is paid to fitting up and keeping closed the space between the shell of the boiler and the bulkhead. The bulkhead ISTo. 12 is for the purpose of isolating the torpedo compartment from the heat accumulated in the steam chest. To free the vessel from water in case of a leak, two ejectors {a, a, iu drawing) are fixed in the largest compartments of the vessel, one in the engine-room, the other in the boiler compartment. It is estimated that the displacement of the other compartments, viz, the aft and torpedo com- partments and of the chain locker, is so insignificant — the lines in these parts of the boat being so sharp — that if one of these three compartments is damaged and filled with water, such circumstance could, at the most, only affect more or less the draught of water, but could not place the boat in any danger of sinking. To Ifet the water from the torpedo compartment and the two com- partments formed by bulkheads on frames Nos. 12, 14, and 19, into the fire-room, to be thence ejected by the ejector, iron pipes 1^ inches in diameter are fixed in the floor parts of. these bulkheads ; and the bulk- head on frame ISo. 19 is provided with a limber-hole. These holes, if required, can be closed from the fire-room by means of plugs. To let the water out of the stern compartment into the engine-room, a valve is provided which is worked in the stern compartment. A similar valve worked in the engine-room, is fixed in the bulkhead separating the engine-room from the boiler compartment. This valve is designed to be used when water accumulates in one of these com- partments to such an extent that, to keep it under control, the simulta- neous working of both ejectors is required and even the taking of water from the bilge by the condenser may be necessitated. This latter NAVAL ENGINEERING IN GREAT BRITAIN. • 37 means of getting rid of the water is resorted to only in the extreme case when the boat is in danger of foundering. The main machinery of the boat consists of a compound surface-con- densing engine (A) for driving the propeller only. To obtain the desired lightness of the mechanism in this engine, all its parts are, as far as possible, made light, without sacrificing strength, by the use of steel and bronze. The parts are further lightened by making the rods tubular, the hollows iu this case serving as receptacles for oil. The pistons are made of wrought steel. The framing of the engine consists of steel columns which connect the cylinder with the bed-plate. The auxiliary engine (B), a two-cylinder one for driving the air:pump, circulating-pump, and two feed-pumps, is placed on a separate bed -plate and works independently of the main engine (A). The ventilator engine (0), a one-cylinder engine, works independently of both of the other two engines and is fixed upon the water-tight bulk- head in the engine-room. It drives the ventilator fan (D), which is erected on the boiler compartment side of the same bulkhead, and is in- tended to supply the fire-room with air. This fan can easily make 1,200 revolutions per minute, and, with the deck-door tightly closed, an air pressure equivalent to three inches of water can be obtained in the fire-room. \ It has been found by experience that with the boiler in good condition, without the aid of the fan, and with the deck-door of the fire-room open, a steam pressure of 65 to 80 pounds can be maintained and the boat run at a speed of 12 knots per hour. A high-pressure locomotive boiler is placed in a special compartment, isolated from the engine-room (G). The shell of its boiler and its tube- plates are made of steel, the fire-box of copper, and the boiler tubes of Muntz metal. The boiler is constructed to work at 130 pounds pressure per square inch, and has been tested to 240 pounds per square inch, hydraulic pressure. To protect the men in the closed fire-room from injuries which would otherwise result from the bursting or serious and sudden leaking of tubes, Mr, Yarrow has patented an arrangement which consists in sep- arating the fire-room compartment from that part of the boiler from which, in case of such mishap to the boiler tubes, the steam would rush into the fire-room, as previously described under the head of " artificial combustion." In some of their torpedo-boats Messrs. Yarrow & Co. have dispensed with standing funnels, as will be seen by Plates 26 and 34. The smoke- pipe can be so arranged at the side of the boat as to carry the heated gases so far aft that no inconvenience can be caused by them. With dampers fitted in the pipes the smoke and gases are turned off through openings in either side or in both sides together, the object being to be able to discharge the products of combustion on the lee side. This arrangement, it would appear, might possess still another ad- vantage, were the pipes carried well aft, by deceiving the enemy as to the exact location of the boiler. It has been proposed by the Eussians to eover the deck immediately over the boilers in future torpedo-boats with heavy plate sreel to resist the penetration of shot from machine guns. The steering resources of torpedo-boats have been greatly increased by the introduction of a bow rudder, which acts simultaneously with the after rudder and by the same steering gear. (See Fig. 1, Plate 58 NAVAL ENGINEERING IN GREAT BRITAIN. 27.) It can be raised out of the water and placed in a well inside of -the boat or dropped off altogether in event of fouling. For torpedo boats as well as torpedo-rams this arrangement would seem to possess great advantage. The Polyphemus is fitted with a bow rudder operated by a separate engine. The advantages of bow rudders are shown by the diagrams (see Plate 21), taken from the London Engineer (vol. xlix, p. 23). The respective areas of the two rudders represented in the diagrams -are as 3 to 1, the stern rudder having an area of 1,500 square inches and the bow rudder of 500 square inches. Plates 28 to 34 show several photographs of the latest torpedo-boats "built by the firms of Messrs. Yarrow & Co. and Messrs. Thorney- croft & Co. Plate 32 is one of Messrs. Yarrow & Co.'s first class tor- pedo-boats, constructed for the Eussian Government. Length 100 feet; breadth, 12J feet ; depth, 3J feet ; speed, 22 knots per hour. The stem is formed like a sharp ram ; and, as will be seen by Figs. 1 and 2, Plate 33, the forward portion of her deck forms a kind of hood, Teaching back to the conning tower. Under this hood or turtle-back are the two ordinary launching tubes placed side by side, parallel with the middle line of the boat. These tubes contain the Whitehead torpedoes, arranged to be dis- -charged by the officer in charge, without exposure and without loss of -speed to the boat. Motion is imparted to the torpedoes by impulse tubes of the ordinary piston-rod type, which can be worked by compressed air or steam. In one of Messrs. Thorneycroft & Co.'s latest second-class torpedo- boats, built for the French Government, the torpedo is placed in a launching tube situated on the deck about 4 or 5 feet irom the bow. Extending from the launching tube to the bow is a concave roller- track to guide the torpedo in its passage overboard. A catch, which holds the torpedo, can be disengaged by apparatus worked from the conning tower. As soon as the torpedo is disengaged, steam is admitted to the im- pulse-tube and motion thus given to the torpedo, which, in its passage overboard, strikes a tappet fixed in the top of the launching-tube, by which the propelling machinery of the torpedo is set in operation. This system seemed to work well on trial. It is very simple, and dis- penses with air-compressing machinery. On the latest first-class torpedo-boats not less than two, and some-, times four. Whitehead torpedoes are carried. Having two torpedoes on board doubles the chances of accomplishing the object. When ships are protected by nets or other rigging placed for the pur- pose of resisting the attacks of torpedoes, it is intended that the first will break through such obstruction, and thus clear a passage for the second, which will act on the enemy's side. Plates 30 and 33 show the outer rigging for operating torpedo spars. The spars for large torpedo-boats are made hollow, of thin steel. Fifty feet is about the gTcatest length used: the greatest diameter, about 6 inches. They are bolted in halves, through and through, and riveted •over in the manner of a screw stay-bolt for the fire-box of a locomotive boiler. The spar is connected with the boat by means of flexible wire-rope, -and operated by a windlass situated in the bottom of the boat under the conning tower. By turning the windlass the pole can be run outwards or inwards, ^nd depressed to a depth of 10 or 1 2 feet. m X b o o CX) Showing both torpedoes housed. Fig. I. House Ex. Doc. 48. Showing port torpedo being lowered. thorneycrofts torpedo boais. Fig. 2. PLATE 28. Showing boat attacking in front. Fig. I. House Ex. Doc. 48. Showing boat attacking on broadside. THORNEYCROFIS TORPEDO BOAT. P"'lG. 2. PLATE 29. YARROWS TORPEDO BOAT. Ready for action. Fig. I. House Ex. Doc. 48. THORNEYCROfTS TORPEDO BOAT. Arranged with transporting and gnn carriage, for discharging the Whitehead Torpedo. Fig. 2. PLATE 30. House Ex. Doc. YARROWS CRUISING TORPEDO BOAT. PLATE 31. Fig. I. House Ex. Doc. YARROW'S TORPEDO BOAT. Showing bow discharging tube. Fig. 2. PLATE 32. Fig. I. House Ex. Doc. 48. YARROWS TORPEDO BOAT With bow discharging tube and spar torpedo ready for action. Fig. 2. PLATE 33. Fig. I. House Ex, Doc. a YARROWS TORPEDO BOAT, Showing funnel turned back. Fig. 2. PLATE 34. NAVAL ENGINEERING IN GREAT BRITAIN 39 PROPOSED INSTRTJCTIONS TO BE OBSERVED IN WORKING MESSRS. YAR- ROW & OO.'S TORPEDO BOATS, OR OTHER VESSELS HAVING COMPOUND SURFACE CONDENSING ENGINES AND A FORCED DRAUGHT. 1. The officer in charge should coustantly bear in mind that the hull is built of very thin steel, and therefore the utmost care is required for its preservation. 2. No portion of the hull should on any account be devoid of paint or other anti-corrosive composition. The whole of the paint or composi- tion should be kept in good condition inside and out. 3. All surfaces, both inside and outside, should be very carefully ex- amined frequently, and where the paint or composition is defective the places should be carefully cleaned and recoated. A report, showing that the examination has been made, should be sent to the proper authorities. 4. To reduce the amount of corrosion to a minimum, should any of the inside of the vessel be bare of paint or composition, pieces of zinc may be placed on the inside of a vessel about every 5 or 6 feet apart, as low down in the hull as possible, so as to be immersed in the bilge water, should there by any. The zinc should be in metallic contact with the frames of the vessel or other part of the structure. 5. Special attention should be given to detect any working of the seams in the skin and the deck plating, and in the event of any symptoms of movement in the butts at the top-sides or deck plating amidships be noticeable, the attention of the proper authorities should be drawn to the circumstance at once. One mode of detecting any movement in the butts is through the paint round the countersink of the rivets and along the butt itself being removed, and the parts exposed getting rusty. 6. No bilge water should be allowed to remain in the boat, and the water ways should be kept clean. MACHINERY AND BOILEU. 7. On lighting the fire tlie boiler should be filled within an inch of the top of the glass, and before/ starting it can be blown out from the sur- face blow-ofE, so that there remain 5 inches of water over the fire-box top. 8. Excepting in cases of urgency, the fire should be lighted and the steam raised very gradually ; at least an hour and a half to two hours should be allowed, it being of the most essential importance that the boiler should not be subjected to any but very gradual variations of temperature. 9. Before raising steam the drain cocks of the cylinders should be open and the links fastened in mid-gear. The leakage through the valves on the steam pipe will generally allow the heated air and vapor to warm the cylinders gradually. In all cases, on starting the engines, even after they have been standing a short time only, the cylinders are to be pre- viously cleared of water. On starting the main engines care should be taken to open the main stop valve very gradually, so as to allow the various parts and pipes to come under pressure slowly. 10. As soon as there is sufficient steam to work the pumping engines, say 20 to 30 pounds, they may be started, care being taken that the ex- haust-cock is open direct to the condenser;, and the circulating inlet on the boat's side also open. The fan engine may likewise be started very slowly, only sufficiently fast to reduce the excessive heat of the stoke hole ; the door on the deck being open, care should be taken that the 40 NAVAL ENGINEERING IN GREAT BRITAIN. fan-exhaust is led to the condenser. Before raising steam the ash-paa door should be secured and the springs on the fire-door examined to see that they are working eflSciently. Care should be taken that the ash- pan is full of water, which can be seen through a peep hole provided for the purpose. Never allow the fan engine to run unless the pumping engines are at work. 11. -When the main engines are stopped with steam up the pressure in the boiler can be kept down by blowing the steam direct into the condenser, the pumping engines being kept running all the time. 12. The best lard-oil only should be used for lubrication. 13. When under way the water in the boiler will be maintained at a constant level, so long as the feed pumps are working satisfactorily, and the boiler not priming. Should either of these contingehciesoccur, warn- ing will be given, either in the engine-room or on deck, by the water rushing out of the overflow pipes from the hot well. 14. It must be clearly understood that sea water is only to be let into the boiler on an emergency, and more than ordinary care mil be re- quired with a boiler of this type to prevent priming under such circum- stances. Care should be taken to change the fresh water in use when the service in which the launch is engaged will permit, as it is consid- ered that the boiler can be kept in a better state of iireservation by this means than if the same water were used continuously. 15. Should a boiler tube give way, or any sudden leakage occur, the engines should be driven at full speed, or the steam blown through into the condenser, so as to reduce the boiler pressure as rapidly as possi- ble; and, in cases of emergency, the steam may be turned on to the fire extinguisher, so as to speedily arrest combustion. 16. The boiler should be cleaned and examined as frequently as the ser\ace will permit, and it, together with its fittings, should be tested by water pressure, not exceeding 200 pounds on the square inch, after one year's service, and afterwards at yearly intervals. The tests are to be conducted and the results reported. The working pressure of the boiler is in this case to be kept at 120 pounds, so long as no defects are shown under the test pressure of 200 pounds. Should it, however, appear, during any of the water tests, that the boiler is be- ing permanently distorted or strained before the pressure of 200 pounds is reached, the test is to cease and the circumstance is to be reported. It is considered desirable to reduce the working pressure each year by 10 pounds after the second year of service. With regard to the other parts of the machinery subject to steam pressure, the fact should be kept in view that the engines are lightly constructed, and that the joints, especially those of the steam pipes, are subject to injury from vibration. The main steam pipes, together with any of the otlier pii)es which appear to suffer in this way, should therefore be tested at the same time and to the same pressure as the boiler. The cylinders need not be tested unless they should be found on ex- amination and gauging to be wearius unfairly"; gauges for this purpose should be carefully prepared by the engineer officer in charge of the machinery of the vessel. 17. Special attention should be siven to the examination of the fire- box, both inside and out, to see that the stays are iut^ct. Should any bulging of the copper fire-box take place between the stays, it is generally an indication that the water space is filled with sediment, which must be at once thoroughly cleaned out. If such an accumula- NAVAL ENGINEERING IN GREAT BRITAIN. 41 tion of sediment collect and the inside box be of iron the plate will proba- bly crack and may cause a serious accident. 18. The boiler should be cleaned very frequently, say once a fort- night, if at work every day. The manhole door should be removed and a hose turned into the boiler to wash it out, the mud-hole plugs and doors being removed. All the plugs should not be taken out at the- same time, so as to concentrate the flow of water as much as possible ;; the water will then flow into the bilge of the boat and must be pumped out. Lights should be put inside the boiler so as to examine every portion of it, and no dirt or grease must be allowed to collect. Steps should be taken at once to dissolve the grease should there be any. 19. When the engines are done with, all connections with the boiler and all sea cocks should be shut off. The fire is not to be drawn, but allowed to die gradually out ; when the fire is out, which shoiild oc- cupy at least a couple of hours, the water may be blown out of the boiler through the brine and blow-off cocks, at a pressure not exceeding 10 pounds, and the boiler should not be refilled with fresh water untiJ it is quite cool ; care must be taken that no water is allowed to return through the blow-off cock being left open too long. 20. Asbestos packing may be used for the steam glands, and the feed pumps packed with spun yarn and tallow. 21. When running continuously, it will be desirable to turn the exhaust steam of the pumping and fan engines into the receiver of the low-pressure cylinder, but if the boat is maneuvering considerably it will be found handier to turn the exhaust direct into the cylinder. 22. The utmost care should be taken to keep an even fire, and it will be found easier to work with a thick fire than with a thin one, although with gcJbd stoking the thin fire will give the better result. If a hole in the fire is allowed, so that the bars are exposed, the immediate result will be an inrush of cold air through the tubes, causing them to leak. The stoking should be performed as steadily as possible, and the fan should be maintained, as nearly as practicable, at an uniform speeds Bapid fluctuations in driving the fan will be very likely to injure the boiler, and bad stoking is sure to give rise to leaky tubes. 23. Neither emery paper nor emery should be used in the engine room. 24. The air pressure in the stoke-hole (as per clause 22) should be maintained as nearly uniform as possible ; for moderate speeds, say not exceeding 16 knots, 2 inches air pressure will be found ample, and should not be exceeded ; and for a full speed run, with good fuel, 5 , inches air pressure will be sufficient, and on no consideration whatever must it be exceeded, and even this air pressure must not be resorted to except by special order. It should be borne in mind that an hour's run at full speed will cause as much deterioration to the boiler as a month's continuous steaming at a moderate speed. 25. Should the boat when running be suddenly stopped, it is the duty of the engineer to turn on the valve leading to the condenser at once, so as to admit of the stoker's continuing to keep the fire going, otherwise the fan would have to be stopped (to prevent an excess of steam), which, by causing a sudden fluctuation in the rate of combus- tion, is injurious to the boiler, as already explained. 26. It is of the most essential importance to prevent grease passing into the boiler; it forms a non-conducting deposit on the tube plate^ which consequently becomes overheated, resulting in leaky tubes,. which can never be afterwards prevented, except by thoroughly clean- ing the tube-plate, a most diflScult operation, sometimes entailing th& 42 NAVAL ENGINEERING IN GREAT BRITAIN. removal of the tubes. The engines will run perfectly well without any internal lubrication, and in most cases no means are provided for letting oil or tallow into the steam pipe, slide-jacket, or cylinders ; in these Instances the only way oil can get in is through the stuffing-box of the low-pressure piston-rod, which should be lubricated as little as possible ; the design of stuffing-box adopted by us is believed to render lubrica- tion to the low-pressure piston rod unnecessary. DIRECTIONS FOR WORKING THE INSPIRATOR FOR FEEDING BOILERS. ' This instrument is designed for feeding high-pressure boilers, and is perfectly reliable under all conditions, both in a sea-way and at rest. It is operated by the use of one handle, and requires no adjustment for varying pressures of steam. Open the suction-cock on the boat's bottom and the steam cock on the boiler. These two cocks should always be open when steam is up. Then, to start the inspirator, move the lever half its travel, and keep it in that position for a few seconds, until the water flows freely through the overflow. Then complete the movement of the lever and the over- :flow will cease, the water being forced into the boiler. If the lever is moved the whole travel at once the effect will be for the steam to pass direct through the instrument and out at the suction, which is a very ready means of keeping the steam pressure under control when the boat is at rest. Be sure that the suction is absolutely tight. COMPOUND ARMOR AND WHITWORTH SCALE PLATES. The idea of manufacturing compound armor, or armor faced with steel, recently adopted by the English and other governments, was first seriously entertained by Charles Oammell & Co., of Sheffield, England. As far back as 1867 several plates were made by them and were tested at Shoeburyness, in England, and at Tegel, in Prussia. These plates were made by the ordinary process of welding slabs of •steel to iron ; but the difficulties of manufacture were so great that the idea was abandoned. Although the reports of the testing of these plates were favorable to this extent that it was represented thatmuch greater resistance was ob- tained by facing iron with steel, it was on the other hand found that the steel separated from the iron after one or two shots, and the subject was laid aside for the time. Mr. Alexander "Wilson, of Sheffield, in 1876 and 1877, patented sev- eral methods of uniting the steel to the iron by the use of " molten steel," which completely overcame the difficulties formerly encountered in the attempt to weld together large masses of steel and iron. The method adopted by Charles Cammell & Co. of uniting plates of the two metals is described as follows : After the iron plate has been rolled to the required thickness a steel plate, a, of hard quality, usually IJ inches thick, is fastened by bolts in the manner shown in Plate 35, at such a distance from the iron plate that the steel (which includes both the steel plate already mentioned and the molten steel to be poured in as hereinafter described) will com- prise about one-third of the total thickness of the plate. The percentage of carbon in the steel varies from sixty to seventy-five hundredths of one per cent. Both plates thus secured are heated uniformly in a reverberatory fur- nace to a bright welding heat. This heat attained, they are removed a o o ©© ©^1©© ©© ©OOOiOOOO NAVAL ENGINEERING IN GREAT BRITAIN. 43 from the furnace and placed vertically in a pit upon a good foundation and the liquid or molten steel poured in between the heated plates. (See Plate 35.) Th^ excess of temperature of the molten steel over the welding heat of the iron fuses the iron to such an extent as to render the two metals inseparable, thus producing a compound plate with a hard steel face to break up the shot, and with a backing of wrought iron, which, by its greater ductility, prevents the destruction of the plate. Upon this system of Alexander Wilson's, Charles Cammell & Co. have since manufactured compound armor. The first manufactured were the plates for the turrets of H. M. S. Inflexible, and tests of these plates, ■which showed their superiority in resistance over iron armor, led the English Government to adopt this system for all subsequent armored vessels. Compound armor has been supplied for the turrets of H. M. S. Hot- spur, for the glacis, smoke-pipes, and hatchway protection of the for- midable torpedo ram Polyphemus, for the turrets of the Agamemnon and Ajax ; for the whole armor of the Conqueror, including ship-sides, turret, and glacis ; for the whole armor and turrets of the Colossus and Majestic ; for the whole armor of the Almirante Brown, lately built for the Argentine Government; for a vessel now building for the Bra- zilian Government ; and for a vessel now in course of construction at Stettin for the Chinese Government. The French Government has adopted it for the following vessels now building in French ports : the Indomptable, Eequin, Duguesclin, Admiral Duperrez, and the Admiral Baudin. The Italian Government have decided to apply it to the cita- dels, ship-sides, and deck-plates of the Italia and Lepanto, now^ building. It has also been suggested for coast defense batteries, instead of wrought iron on the plate, upon plate system. Following are a few particulars of some of the thickest compound armor plates supplied for foreign war ships : For the French ships Indomptable, Caiman, and Eequin greatest thickness of armor at water line, 19.6 inches (equal to 25,4 inches of wrought iron); Admiral Duperrez and Admiral Baudin, greatest thick- ness of armor at water line 20.6 inches (equal to 28 inches of iron). For Italian war ships Lepanto and Italia, greatest thickness of turret armor 18.8 inches (equal to 24.4 inches of iron). For British war ships Ajax and Agamemnon, greatest thickness of turret plates 16 inches (equal to 20.8 inches of iron). Inflexible turret plates, two thicknesses, the outside composite armor plates 9 inches thick and the inside iron plate 7 inches thickness (equal to 18.7 inches of iron); Conqueror, greatest thickness 14 inches (equal to 18.2 inches of iron). The superior resistance of compound armor plates to those of wrought iron has been variously estimated at from 25 to 30 per cent. To show the saving in weight gained by the substitution of steel- faced armor for wrought iron, without lessening the shot-resisting power, Mr. J. D. A. Samuda, in a paper read at the last meeting of the Insti- tution of Naval Architects, instances the Almirante Brown, built by his firm for the Argentine Eepublic, the first vessel afloat constructed entirely of steel and coated with steel-faced armor. Mr. Samuda says that the effect of using these materials has been to obtain a strength that in an iron vessel of the same capacity could be gained only by an increase of at least 510 tons in weight (as given be- low). An extra 350 tons weight would be required on account of the enlargement of the hull. 44 NAVAL ENGINEERING IN GEEAT BRITAIN. An iron-built and iron-armored vessel, built to carry this additional weight of 350 tons, in order to preserve the same speed, draught of water, and coal-carrying capacity as the Almirante Brown, would, ac- cording to Mr. Samuda, be proportioned in size, displacement, and power, as follows : Length ..feet.. 260 Breadth do... 55- Displacement tons.. 5,200 Coal to be carried do . . . 720 Horse-power 5,000 To be comi^ared with the Almirante Brown, with her steel hull and steel-faced armor, proportioned as follows : Length feet.. 240 Breadth do... 50 Displacement tons.. 4,200 Coal to be carried do . . . 650 Horse-power 4,500 From the above it will be seen that an iron-armored ship of the shot- resisting power and speed possessed by the Almirante Brown will re- quire 1,000 tons additional disjilacement, 500 additional horse-power^ and 70 tons additional coal capacity to enable her to travel the same ' number of miles without recoaling. The advantage of the compound system under oblique fire is enor- mously greater than that of iron armor. In Prussia, during the month of July, 1881, an 8-inch Wilson com- pound plate was fired at \^^th the 28-centimeter (11.02-inch) gun at an angle of 55°. The projectile glanced ofl", broken into fragments, having produced upon the plate a " scoop" 4 inches deep. Fired at an angle of 75°, the projectile went through the plate. In these trials, the striking velocity was 423 meters (16,653.5 foot- pounds) per second, and the weight of the projectile, 517 pounds. The effect produced by a shot striking an experimental compound plate of Messrs. Oammell & Co.'s manufacture is clearly represented by Plates 36 and 37. The dimensions of the plate were the same in both cases, as follows: 3 feet ten inches by 3 feet 6 inches by 9 inches. The thickness of the steel faces was 5 and 4^ inches respectively. A 7-inch service gun discharged the projectile in both instances — servicePalliser shot weighing 113 pounds; charge, 30 pounds of pebble powder ; range, 30 yards. The indentation in the plate, as shown in Plate 36, was 3.2 inches deep; the bulge at the back stood out two-tenths of an inch. The indentation in Plate 37 was 5.45 inches ; the bulge at the back 1.4 inches. In March, 1881, a Wilson's compound steel faced armor plate — dimen- sions 7 feet 3 inches, by 6 feet, by 11 inches thickness (steel 2f inches, iron, 8J inches), representing the ship-side armor of H. M. S. Conqueror, was tested on board of H. M. S. Nettle at Portsmouth. The gun used was a 9-inch muzzle-loader, weighing 12 tons ; projec- tile, of Palliser chilled iron, weighing 258 pounds; charge, 50 pounds pebble powder, range 10 yards ; velocity 1,340 feet per second. The plate was fired at three times and the results were considered highly satisfactory. The conditions of the test in this case were, that the plate should not be less than 8 by 6 feet in surface, not less than 9 inches in thickness, and should receive a 9-inch chilled cast-iron projectile fired from the House Ex. Doc. t PLATE 36. House E*. Doc. 48. PLATE 37. ?^ j.- ,3^V^'— - - -4 ^'- C.;^';.-2 .^- T NAVAL ENGINEERING IN GREAT BRITAIN. 45 Service 12-ton gun with 50 pounds of powder, at a range of 10 yards, without cracking through ; and should the plate be surrounded by a frame, it should not be penetrable by any of three such projectiles, there being a fair distance between the spots struck — say 2 feet. The great superiority of compound armor under oblique fire has led to the adoption of curved plating on deck, glacis, and barbette turrets of some of the most recent war ships. Plates 38 and 39 show sections of Oammell's compound deck and side armor for foreign war ships. Plates 40 and 41 are sketches showing in plan and section the arrangement of armor for the turrets of two of the largest foreign war ships. The English Admiralty conditions of tests for acceptance of their armor, are as follows : "The Admiralty has the right to select for test by aitillery any plate from the batch ; such plate shall then be machined to a rectangular form as nearly as possible to its finished size. The test plate shall be fixed by armor bolts to a suitable bulkhead ; and shall then receive three shots fired directly from a gun at a range of thirty feet, each pro- jectile falling upon the point of an equilateral triangle having sides of two feet each, described upon the middle of the plate. " Upon the supposition that a composite (steel-faced) armor plate may be about 20 per cent, thinner than a wrought iron plate of equal resist- ance, the caliber of the gun, the charge, &c., to be used in testing these plates shall be such as would cause perforation of a thicker iron plate. " The first shot shall not produce any through cracks in the plate, and no one of the three projectiles shall be capable of getting through the plate. "Such plate, having stood the test in a satisfactory manner, will be paid for by the government ; but should it not stand the test in a sat- isfactory manner, it will not be paid for nor the expenses of carriage , to the place of test ; and the entire lot represented by the test plate may be rejected. The contractor, however, shall have the right to require that a counter test shall be made on a second plate to be selected for this purpose under the same conditions ; and in case the result of the test on the second- plate shall confirm that of the first, the whole lot shall be definitely rejected. " If, on the other hand, the result of the test on the second plate shall be deemed satisfactory by the Admiralty, the lot may be accepted. " But in case of doubt, the Admiralty may proceed to a third test under the aforesaid conditions, upon the result of which the whole lot shall be accepted or rejected. " It is a condition that at most only one of such test plates shall be pajd for in the event of the plates represented by it being accepted." This style of armor is fastened to the ship or turret from the inside, and not, as iu the case of, iron armor, by through bolts with conical heads. Plate 42 shows the method (patented by George Wilson of Charles Cammell & Co.), and now adopted for ship-side armor iu foreign war ships. The bolts and nuts are of a special steel made by Messrs. Cam- mell & Co. Plate 43 shows the safety fastening adopted for turrets and such parts of the vessel as will be frequented by the men behind the armor while fighting the ship. The object of the fastening is to keep the bolts from being driven in among the men. It is secured within a mild steel casting (A) by the screwed plug (B) after the bolt has been tightly screwed up to the armor. The experiments hitherto made with steel as a metal to resist the pene- 46 NAVAL ENGINEERING IN GREAT BRITAIN. tration of shot have not been sucli as would induce its adoption as the sole material for this purpose, although this is a subject that is receiv- ing some attention from many of the foremost scientific men who are in- terested in engineering science. It is more than probable, however, that when the time comes to con- sider the great weight of the armor which will be sufficient to resist the superior penetrative power of the present improved Whitworth and other steel guns, that an armor will be constructed composed of a very- mild, ductile steel backing, with a hard steel face, fused together in the manner already adopted by Cammell & Co., with a steel of a hardness intermediate between that of the backing and the face ; and it would seem that the day is not far distant when the present composite armor will be entirely supplanted by steel armor similar to that here described, as soon as the varying chemical composition of steel of different degrees of penetrability becomes better known. Castings of steel are already produced that are free from blow-holes and ductile to a surprising de- gree. Could the system of casting steel-armor plating be effected, the pres- ent costly and massive rolling and bending machinery could be dispensed with at a great difference of first cost between the two systems. As illustrative of the increasing necessity for superior armor with greater resisting power and a minimum of weight, I give the following comparison between one of the old type and one of the new type of guns, the latter being of the steel tube pattern covered with wrought-iron rings as manufactured by Sir William Armstrong for the British Navy. Comparison tetween ih-ton guns. Old type. New type. Caliber in iDches Lengtli of bore in calibers Cbarge in pounds Weight of projectile in pounds Muzzle Telocity, feet per second Total energy, i'oot-tona Thickness of plate it can perforate in inches. 11 10 u 26 85 19» .'i.^'i 400 ^^f, 1,950 415 10,650 14 1» WHITWORTH ARMOE PLATING. The system invented by Sir Joseph Whitworth, of Manchester, En- gland, consists in covering ship-sides, turtle-back deck, and conning tower of torpedo rams with scale armor. The torpedo ram Polyphemus is covered with the Whitworth armor^ composed of a series of tiles, each about 10 inches square and 1 inch thick, made of Whitworth's fluid compressed steel, that is both hard and ductile and of great tenacity. The tensile strength of the hard steel plates is 80 tons per square inch ; while that of the under plate to which the tiles are bolted is about 40 tons per square inch. The scale-plates are secured by hardened steel-bolts, one screw being in the middle of each plate, and one at each corner, to hold the four ad- jacent plates, the whole surface being flush, as shown by the sketchy Plate 44. The end sought by means of this style of plating is to break up the shot and to restrict any starring of the metal to the limits of the scales struck. Plate 45 shows Whitworth's patent armor, after having been struck House Ex. Doc. Effect of Palliser Chilled Cast Iron Shot. — — on WHITWORTH'S PATENT ARMOUR. PLATE 45. NAVAL ENGINEERING IN GEEAT BRITAIN. 4T by a Palliser chilled cast-iron shot weighing 224 pounds. The shot broke into a great number of pieces. The target in this case was 72^ inches square, 9 inches thick ; diam- eter of bore of gun, 9 inches ; powder charge, 50 pounds ; range, 20 yards ; maximum penetration, 2 inches ; mean penetration, 1.13 inches. It would seem that war ships already armored with iron armor, might have their shot-resisting power greatly increased with slight additional weight by attaching plates like these Whitworth scale-plates to a good iron backing. STEEL. The peculiar merits of mild steel are becoming so well known to na- val architects and engineers that its superiority to iron is no longer a matter of doubt. Steel is already rapidly displacing iron for ship-building, boiler-con- struction, and general engineering purposes ; and it is the opinion of scientific men that, when the properties of different grades of steel be- come better known (which can be effected only by subjecting each prod- uct to mechanical test, and by keeping an exact record of the compo- sition and observed merits of each kind of steel produced), the trust- worthiness of this metal, and the almost absolute certainty of the an- ticipated results of each grade, as produced by the leading mai. -^rs, when employed for the purposes above mentioned, will soon render it the usual material for the construction of guns and the armor plating: of ships of war. During the latter part of last year, Mr. William John, general man- ager of the Barrow Ship-building Works, and'until recently assistant to the chief surveyor of Lloyd's Registry, informed me that mild steel was the material of at least one-quarter of the total tonnage at that time building in the United Kingdom. Mild steel plates of the most perfect homogeneity are now produced by both the Bessemer and the open-hearth system. The surprising ductility of mild steel, combined with its great tensile strength and practically absolute uniformity, extending over a large quantity of the metal, are the prime reasons that render it so reliable. Lloyd's conditions of test will serve to show the strength practically attained in mild steel. These conditions require that the tensile strength must not fall below 27 tons, nor exceed 31 tons, per square inch of section : and the per- centage of extension on 8 inches must not fall below 20 per cent. To show the evenness of mild steel in point of ductility and tensile strength which is required to meet the above conditions, I give the fol- lowing experiments made with the angle-bars and plates of several ships tested by Mr. William Denny, of Dumbarton, Scotland. 48 NAVAL ENGINEERING IN GREAT BRITAIN. Table XII. 00 Angles or plates. a o fHOO g« »a ^3 = mc 1 a « - 1 is a 9 = 3 ; M M i _ Tom. -224 I AnRloa, &c ^ 28.2 1 Plates - 29.0 2S.3 21.9 28.6 , 23.6 225 28.80 29.65 22.70 Plates 22.53 29. 225 22.615 ^26 30. 208 29.27 2L67 21.58 29.739 21.625 233 29.41 2e.46 23.38 22.16 28. 935 32.77 29. 125 22. 653 Alreadj' the workmen of the ship-building yard and boiler-plate shop prefer working steel rather than iron plates, mainly on account of the greater ductility and malleability of steel and its smaller percentage of waste. In addition to the good qualities of this metal already set forth, the construction and engineering department of the British Admiralty report that mild steel is cheaper than the best wrought iron, such as has been required for the construction of hulls and boilers. In point of ductility the iron usually employed in plates for ship-build- ing and boiler construction bears no comparison with mild steel, the ten- sile strength of which is always at least 30 per cent, greater than that of the best wrought iron produced in Great Britain, as appears from the following Tables XIII and XIV: Table XIII. — Series of experimenla conducted hy Mr. Kirlcaldy. Description. Iron ship plates Iron boiler plates, ordinary quality TorltsliirewToughtiron plates. ^Steel plates of Steel Company of Scotland Inch. i, i, i, 1 Lengthwise. Tmw. 22.01 21.15 21,3 29.3 §2 Per cent. 5.4 13.07 20.6 49.1 a 2 « M a Per cent. 5.7 9.6 16.7 Croaawise. S «.a a " ® a « §1 aS . o «■£ a n ° Sow Tons. Per cent. 18.48 20.3 4.41 14.7 Si Per cent. 3.2 U 2 25.5 NAVAL ENGINEERING IN GREAT BRITAIN. 49 Table XIV. — Series of expetitnetits made by Messrs. C. Cammell ^ Co., Sheffield, on their best iron platis, svoh as they supply to the Admiralty. [Extracted from Messrs. Parlcer Sc Jolin's report to Lloyd's committee.) Thickness of plate. Description. Edge of hole. Breaking strain in tons per square inch. Percentage of loss from strength of plain plate. Kemarka. Inch. ,74 24.88 22.53 22. 56 18.19 18.93 21.17 22.57 18.8 18.8 9.2 3 Mostly crystalline. .74. do .74 do Do. .74 . 1.1 1.17, 1. 1 1. 32 J 1.13 1.13 Slightly crystalline. Do. .74 ....do .74 Punched and reamed . . Drilled Do. .74 . Do Strength of plate taken to be the mean of three plain specimens, 23.32 tons. As the contraction of area at the moment of fracture is a guide in ascertaining the ductility of metal, the great difference between iron .and steel in this respect will be seen by reference to the foregoing tables. In the steel the mean contraction was 49.1 per cent, against 20.6 per cent, for Yorkshire wrought iron plates, and 5.4 per cent, for ordinary ship plates. Steel is equally strong both crosswise and lengthwise, in- stead of having, like iron, the greatest strength in the direction of its ifiber, as will be seen from the following exppriments made by Mr. Kir- kaldy for Mr. T. W. Trail, surveyor-in-chief of the Board of Trade of England, and by Mr. Trail embodied in an able report on steel to the assistant secretary of the marine department: Table XV. Thickness of plate. Mean ultimate stress per square inch. Mean elastic stress per square inch. Mean ratio of elastic to ultima^. Lengthwise. Crossviae. Lengthwise. Crosswise. Lengthwise. Crosswise. J inch Tons. 31.4 28.6 29.1 28.0 Tons. 31 28.9 29.5 28 Tons. 19 15.8 15.8 14.9 Tons. 19.1 15.7 15.6 14.8 Fer cent. 61 54 53 53 Per cent. ^inoh 55 53 52 Mean 29.2 29.3 16.3 16.3 55 55 As to the superiority of steel to iron, Mr. William Parker, principal surveyor to Lloyd's Registry, who is, perhaps, from his position, as well •qualified as any man living to gire anppinion upon this question, stated •quite recently that out of a total of four thousand steel plates only ten or fifteen have been condemned, and these not because of inferior metal, but solely on account of improper or negligent manipulation, while he has found it by no means uncommon to be obliged to reject ten or twelve iron plates out of the number required for one boiler. H. Ex. 48 4 50 NAVAL ENGINEERING IN GREAT BRITAIN. Mr. F. W. Webb, of the Bolton Iron and Steel Works, also stated at the April, 1881, meeting of the Institution of Mechanical Engineers- that at the present time he had over sixteen hundred locomotive boilers of steel working at 140 to 145 jjounds steam pressure per square inch^ and he had had no trouble whatever with them. He also said that he- has made more than one hundred thousand practical tests upon steel plates, and had never been obliged to reject more than two plates for failing in actual work, and those two failures had been due entirely ta mismanagement on the part of the men. I could refer to a number of other users of the metal of equal authority.. Mild steel is now used altogether in the construction of English war ships. Notable among those so constructed are the Leander, Phaeton» and Arethusa, now building at Messrs. E. Napier & Sons, and the Co- lossus, now building at Chatham dock-yard. The hulls of the fast-armored cruisers Warspite, Imperieuse, and CoUingwood, just laid down, are to be made of mild steel. The swift cruisers recently built from the designs of Mr. George Eendel, of Sir William Armstrong & Co., for' the Chinese and Chilian Governments, were built of steel. The hulls of the French war ships, just laid down, I learn, are to be constructed of steel,- and all of the torpedo boats built by Yarrow & Co., Thorneycroft & Co., and Hanna, Donald, Wilson & Co. are of the same material. In the merchant marine, mild steel meets with equal success. The approximate figures, as given by surveyors' returns, Lloyd's Reg- istry, to June 30, 1881, showed 120,000 tons gross of steel ships to be building in the kingdom. These figures, compared with 4,500 tons- classed at Lloyd's in 1878, give some idea of the rapid strides that haye been made in steel shipbuilding during the last four years. Among the latest large ships built entirely of steel is the steamship Servia of the Cunard line, the steamship Parisian of the Allan line, and the Rome of the Peninsular and Oriental line. In fact all the lately built steamers of the last-named line, as well as of the British India line, are of steel. The Vanduara, the fastest yacht in English waters, de- signed by the distinguished yacht-builder, G. L. Watson, of Glasgow, is- constructed mostly of steel. Mr. William Denny, of the firm of Denny Bros., of Scotland, has stated that he has effected an average saving of 13 J percent, in weight by using steel instead of iron. ' One of the best examples of the saving in cost effected by using steel ships instead of iron which I have yet seen was presented by this gen- tleman in a paper on the economical advantages of steel ship-building, at a meeting of the Iron and Steel Institute during the past year. The items given below, which set forth the invoiced weight of iron in a spar-decked steamer of about 4,000 tons gross, with the cost at cur- rent price of iron and the same particulars for a vessel of steel, are taken from Mr. Denny's valuable paper. NA\ AL ENGINEERING /IN GREAT BRITAIN. Cost of iron required in a spar-decked steamer of 4,000 tons gross. 51 Plates, angles, and bnlbs Slip iron Bound and bead iron Porgin gs EiTetB Less 9 per cent, scrap Tons. Cost per ton. 2,098 52 31 41 111 £6.0 5.5 6.5 25.6 10.0 3.5 3,123 Total cost. £12, 568 286 202 1,060 1,110 15, 236 735 14, 501 Cost per ton of invoiced weight, ^^^'°" = £6.25. N. B. — Owing to the ]^lates in this steamer being 16 feet long, 610 tons of them exceed the limits allowed by iron-makers in size and weight ; and, on this, an extra payment of £650 would be Teqnired,- The trae cost of the iron wonld, therefore, be £15,151, instead of £14,601. The limits allowed by the steel-makers wonld entail no extras on this vessel. Cost of iron and steel m the same vessel ouilt of steel. Tons. Cost per ton. - Total cost. Iron plates and angles '. . . Slip iron Kpnnd and bead iron BiTets Steel plates, angles, and bulbs Forgings Bivets Less 9 per cent, scrap 244 49 31 16 £6.0 5.5 6.5 11.0 £1, 464 270 202 176 9.25 26.6 13.0 2,112 14, 513. 1,050 1,040 2,030 183 18,715. 640 1,847 18, 075 Cost per ton of invoiced weight, -^^I? = £8.9. ^ ^ 2,030 Mr. Denny says it will be seen that the difference between the amount of invoiced iron in the iron steamer and the amount of invoiced steel and iron in the? steel steamer is equal to 303 tons, or, nearly as possible,. 13 per cent, of the weight of iron. To arrive at the dead weight ca- pacity, 9 per ,cent. is deducted. This leaves the weight of the iron actually worked into the steamer at 2,123 tons, and the weight of the iron and steel worked into the steel steamer at 1,847 tons, giving a dif- ference of 276 tons, which would be the increase in dead weight capacity, equal to nearly 7 per cent, on the gross register of the steamer. The difference in cost between the two steamers is £3,574. Dividing this amount by the increase of dead-weight capacity (276 tons) gives the extra dead weight, costing £13 per ton. In the case of this steam- er, which he considers to be a high-class, fast-speed passenger steamer, with the combination of good carrying power, he assumes that such a steamer would make three and one-half round voyages from London to Calcutta and return in the course of the year ; that is, seven single voyages ; and if upon each of these voyages it is estimated that the freight earned per ton of dead-weight capacity is 20s., then each ton of increase earns £7 per year, or in two years £14. From this 7 per cent, per annum, or 36s., is deducted, leaving £12 4s. as the net earnings per 52 NAVAL ENGINEEBING IN GREAT BRITAIN. ton ill two years; thus showing that the cost of the extra dead-weight capacity would be cleared off in that time. On account of its above-mentioned qualities, ductility, and tensile strength, steel meets with great favor among British builders as th« suitable material for boiler construction in ships for the merchant ma- rine and foreign navies. Two of the highest-powered transatlantic passenger steamers — the Servia, of the Ounard line, and the Alaska, of the Guion line — have all theiir boilers constructed of steel. In the British Navy steel has been adopted in the boilers of the torpedo-ram Polyphemus and for the shell- plates and furnaces of the boilers of the fast cruisers now building, the Leander and class. It will also be used for the boilers of the Warspite, Collingwood, Majestic, and other vessels just laid down for the English Navy. Eugiueer-in-Chief Wright, of the Navy, informed me that in alli)rob- ability all the boilers for war ships for the time to come would be made wholly of steel. The boilers of the Chinese and Chilian cruisers, constructed by E. & W. Hawthorne, of Newcastle-on-Tyne, were made throughout of Sie- mens-Martin steel plates and riveted with steel rivets. All the tor- pedo-boat boilers by the different builders are also made of steel. The greatest care is now given by makers to the manufacture, as the different grades of steel not only possess widely different degrees of strength (which varies according to the percentage of carbon used), but have widely different mechanical properties, which require various methods of treatment in working; and for this reason makers attach much importance to a thorough knowledge of the work to which the pieces manufactured are to be subjected. The following list, supplied to me by the Steel Company of Scotland, shows approximately how the breaking strain of steel depends upon the percentage of carbon which it contains : Percentage of carbon. ! Tensile strength. I 1 .10 to. 12 ■ 22 to 23 tons. -]2to.U ; 23 toSlJtons. .14 to. 16 ! 24i to26 tons. .16to.l8 26 to28 tons. .18 to. 20 I 28 to 29* tons. ,20 to. 22 Ij 29i to 31i tons. •22 to. 24 eHto34 tons. The following list gives the percentage of carbon used in steel man- ufactured by the same firm for various purposes : Per cent, of carbon. Tin plates and iron rods 1 to .14 Fire-box plates 15 to .17 Ordinary boiler plates 16 to .19 Ship plates.. 18 to .ao Eails 25 to .45 Forgings 25 to .35 Castings 20 to .40 At the same works every plate, angle, and bar is subjected to a tem- per bending test before being sent from the works. In addition, every charge is tried for tensile strength and ductility, and in the case of boiler plates to be passed u pon by the Board of Trade or Lloyd's Sur- veyors every plate undergoes a trial of tensile strength. NAVAL ENGINEERING IN GREAT BRITAIN. 53 Each plate or bar, as it is cut, is numbered, and the same number stamped on the cuttings which are taken from it for testing purposes. In a book, opposite this plate number, there is registered the charge, size, and thickness of plate, &c., purpose intended for, order, number, and date of shearing and rolling, so that the plate number also forms a com- plete reference number ; and by means of it a complete history of the plate can be given after any length of time, including an account of its behavior under various tests. To prevent as far as possible the failure of steel plates, from deficient information as to th« proper method of treating this material, the Steel Company of Scotland has published, and directs the attention of the users of the steel to, the following rules : " 1. Welding. — In welding mild, steel plates it is not necessary to heat them to the same high temperature as in the case of iroh. Instead of a welding heat, a bright yellow heal is sufiflcient; and if flux is re- quired, it need only be three parts clean sand to one part common salt, moistened, and thrown on the parts in the fire. We recommend that the weld be of the V form in preference to the lap, and that it be treated in the usual way, that is, light-hammered on the V part. After the weld is made, and while the heat is good, the parts near and on either side of the weld should also be lightly hammered. In making the weld, the fuel used should be free from sulphur ; otherwise red shortness may re- sult. " 2. Flanging. — In flanging care should be taken in the local heating that the parts are not overheated, and that no hammering or work is put upon then while at a black heat ; further, it would be well if work could be continuous until each flange is completed, or, if the plate has to be laid aside before it is finished, it should be protected from chills, if it be not convenient to keep it warm. "3. Annealing. — After completing either welding or flanging, the whole piece should be heated to a cherry red heat and slowly cooled, " 4. Orders. — In ordering steel plates care should be taken to state the purpose for which they are to be used, especially in cases where they are required to weld and flange." To show the great care that is taken at these works, we may instance one of their tests. A man is stationed by the shearing machine whose sole duty is to take a portion of a shearing from each plate, heat it to a cherry red, cool it suddenly in water, and then Jbend it, observing closely the effect on the piece of steel. The plate is rejected if the test is not satisfactory. This test affords a ready means of detecting a brit- tle plate, which, from haiving been well annealed, might have passed the cold bending test without discovery. The following results of experiments, made by Mr. P. F. Maccullum, of Glasgow, Scotland, to ascertain the effect of cooling mild steel speci- mens from a red heat in water at 82 degrees Fahrenheit, enables a com- parison to be made between hardened and unhardened plates. The table is from a paper read by him at the last meeting of the Institution of Eitgineers and Ship-builders of Scotland. 54 NAVAL ENGINEERING IN" GREAT BRITAIN. Tabus XTI. ^ u 1 Dimensions in inches. Area, sqoare inches. Breaking sixain in tons. Elongation ott 10 inches. ActnaL Fra-BiiiiSTe inch. bichea. Feromt. TTnhardened A B C D 1.52 by. 384 1.52 by. 48 1.505 by. 445 : L 635 by . 5 .583 .729 .669 .817 16. M 20.13 20.14 22.88 27.5 27.5 30.1 28 2.56 2.30 2.32 2.44 25.6 23 23.2 244 Means -- 2i.2i 24.05 Hsodened A \ D L51 By. 378 L 518 by .475 1.64 by. 46 1.635 by. 5 .570 .721 .754 .817 2L73 29.49 30.15 29.77 sai 40.9 40.6 36.0 1.42 1.03 1.10 1.92 14.2 10.3 U 19.2 5^3 9 13.68 Further experiments by the same gentleman, given in Table XVII, show how the tensile strength and ductility of mild steel plates are affected by annealing. The experiments were made with eight speci- mens cat fi»m J-inch steel plate. T.VBLE xvn. Annealed. Dimensions in inches. Area, square inches. Breaking strain in . tons. Elongation. ^•o. 1 Xo.2. So. 3 Xo. 4 ' 1. 690 by . 234 1. 650 by . 240 1. 660 by . 241 1. 656 by . 242 i Actual. ! ^*f *?,?*" Inches. 'Percent inch. ITnannealed. . . >-o.2 L663by 237 .394 ■ 10.60 Xo.4 L 675 by 240 .402 I 10.60 Xo.6 1.680 by 241 .404 10. f2 So. 8 1. 680 by 241 .404 10.71 Means I .395 , .396 .400 .400 9.39 9 48 9.79 9.70 2a9 26.3 26.7 26.5 26.60 , 23.7 23.9 34.4 24.2 1.90 L77 . 1.94 ! 8.19 ' 23.7 22.1 24.1 27.3 Means . 24.05 , lime. 8k. 10 24. 32 4 47 29 3 10 oi. 5 4 2a8 5 30.2 5 30 Table XVm. — EesulU of experiments on two mild steel plates. [ Three specimens were cut from each plate and ceaited— annealed, anannealtd, and hardened. Carbon of plate A^0.14 per cent. ; carbon of plate B^0.15 per cent.] ! 1 I I Breakiogstrain| Elongation on ~r in tons. ' 8 inches. DimenEionsl inches. Annexed. . A ITnannesded ; A Hardened.. A Annealed. , B ITnannealed ; B Hardened ' B L 62 by . 67 1. 615 by . 666 L 622 by . 667 I. 635 by. 617 L21 by. 61 L61 by. 62 1.085 1.075 L081 L008 .738 26.03 2a 47 34.99 25.54 20.24 35. SO _i o a 1 23.9 ' 2.25 2&1 26.4 2.08 16.0 32.3 . L6S 20.6 25.3 i 2.34 28.2 27.4 ' 2.16 zr.o 35.8 ■ L42 17.7 NAVAL EXGINEERING IN GREAT BRITAIN. 55 Followiug are the instructions recently issued by the surveyor-in-chief of the English Board of Trade, Mr. T. W. Trail, relative to mild steel tests for marine boilers, &c. : " The test strips must be carefully prepared and measured, and they should be cut from the plate by a planing or shaping machine. " The bending strips should not be less than 2 inches broad and 10 inches long, and they should be bent until they break; or until the sides are parallel at a distance from each other of not less than three times the thickness of the plate. " The tensile stress of the plates not exposed to flame should be about 28 tons, and should not exceed 30 tons per square inch of section, and 28 tons should be the stress used in the calculation for cylindrical shells, if the plates comply with all the conditions as stated herein. "The tensile strength of furnace and combustion-box plates should range from 26 to 28 tons per square inch. "All plates that are punched or flanged or locally heated must be ■carefully annealed after being so treated. " The rivet-holes in the furnaces and longitudinal seams of cylindri- cal shells should be drilled ; but if it is wished to punch them, and afterwards bore or anneal the plate in a proper furnace, the particulars of punching, boring, and annealing should be specially considered be- fore being done, but all punched holes should be made after bending. " Solid steel stay-bolts may be allowed a stress of 7,000 pounds per square inch of section. " If the plates exposed to flame comply with the foregoing condi- tions, the constants in the Board of Trade rules for iron boilers may be increased as follows : The furnace constants, about 10 per cent. ; the constants for flat surfaces where they are supported by stays screwed into the plate and riveted, about 10 per cent.; the constants for flat surfaces when they are supported by stays screwed into the plate and nutted, 25 per cent. " The rivet section, if of iron, in the longitudinal seams of cylindrical shells where lapped and at least double-riveted, should not be less than one and five-eighths times the net plate section ; but if steel rivets are used, their sections should be at least twenty-eight twenty-thirds of the net section of the plates, if the tensile stress of the rivets is not less than 28 tons and not more than 30 tons per square inch. " Local heating of the plates should be avoided as much as possible. " Welded steel stays or plates should not be approved of unless the results of a sufi&cient number of experiments show that the weldingcan be done satisfactorily. " If steel is proposed to be used in superheaters, the particulars should be specially considered, but in all cases it would be better to discourage its use for this purpose. " In other respects, boilers should at least comply with the rules for iron boilers in the instructions issued by the Board of Trade. 'iThe steel makers or boiler makers should test one or more strips cut from each plate for tensile stress and elongation, and stamp both results on a part of the plate where they can be easily seen when the boiler is constructed. " The tensile strength and elongation should be>iioted by the inspec- tion officer. " The officer responsible for the boilers need not witness the above tests, but he should select one in four of these plates either at the steel works or the boiler-maker's works and witness the testing of at least one strip from each selected plate. 66 NAVAL ENGINEERING IN GREAT BRITAIN. " If for the i)lates from which he selects the above proportions a greater stress is wished than is allowed for iron, tests for tensile stress and elongation should b* made ; and those for which no reduction of thickness is asked may be tested for resistance to bending if preferred. " The results of all the tests witnessed by the inspecting officer should be stamped on each plate. , " The bending tests for plates not exposed to flame should be made with strips in their normal condition ; but the strips cut from furnaces, combustion boxes, &c., should be heated to a cherry red, then plunged into wat^r of about 80° Fahr., and kept there until of the same tem- temperature as the water, and then bent. "The breadth of test strips for tensile stress should be about 2 inches, and the elongation taken in the length of 10 inches should be about 25 per cent, and not less than 20 per cent." BRITISH ADMIRALTY TESTS FOR BOILER STEEL. ' " Strips cut lengthwise or crosswise to have ;in ultimate tensile strength of not less than 2C tons, and not exceeding 30 tons per square inch of section, with an elongation of 20 per cent, in a length of 8 inches. " The angle, T, and bar steel to stand such forge tests, both hot and cold, as may be sufficient, in the opinion of the overseer, to prove soundness of material and fitness for the service intended. " Strips cut lengthwise or crosswise IJ inches wide, heated uniformly to a low cherry red and cooled in waterof 82° Fahr., must stand bend- ing double in a press to a curve of which the inner radius is one and » half times the thickness of the steel tested. " The strips are all to be cut in a planing machine, and to have the sharp edges taken off. " The ductility of every plate, angle, &c., is to be ascertained by the application of one or both of these tests— to the shearings, or by bend- ing them cold by the hammer. All steel to be free from lamination and injurious surface defects. " The pieces of plate, angle, &c., cut out for testing are to be of par- allel width from end to end, or for at least S inches of length. The steel plates, angles, &c., may be drilled or punched, but if punched, they must be either annealed afterwards, or the holes punched about one- eighth of an inch less in diameter than the rivets, and enlarged to the proper size by reaming." At certain temperatures steel loses its ductility and becomes brittle. This fact was announced by Mr. Daniel Adamsoii at the meeting of the Iron and Steel Institute at Paris in 1878. Eecently Mr. J. F. Barnaby, Admiralty inspecting officer at the works of Charles Cammell & Co., confirmed Mr. Adamson's statement of this fact by a series of interesting experiments, made for the British Admi- ralty, with sixty eight specimens of Siemens-Martin and Bessemer mild steel from the following steel-makers : Messrs. Cammell & Co. ; J. Brown & Co. ; Bolton Steel and Iron Company; The Steel Company of Scotland; Parkhead Steel Works, Glasgow; Landore Steel Company. The results showed that, at certain tempemtures (about 550° Fahr., according to Mr. F. W. Bick, of the Steel Company of Scotland), vary- ing between a light straw and a light blue color, it is extremely unsafe to work mild steel for any purpose, as evciv specimen broke on beinff bent. (See Plates 46, 47, and 48.) In view of these results the Admiralty have considered that, when partial annealing is practiced, there may be a danger of certain portions ^ ;^ m a o o 00 '^ ^::< NAVAL ENGINEERING IN GREAT BRITAIN. 51 of plates or bars having their strength and other good qualities deterio- rated, and that, probably, annealing should be dispensed with or made- to affect the whole of a plate or bar simultaneously. Owing to this change in the quality of mild steel, Mr. Trail, of the- Board of Trade, does not sanction its use for the construction of super- heaters. The results of experiments to ascertain the effect of a black heat upon the strength and ductility of mild steel specimens are given by Mr.. MaccuUum, of Glasgow, as set down in the following table : Table XIX. Dimensions in inches. 1.63 by. 49 1.63 by. 46 1. 57 by . 684 1.63 by. 68 1.69 by. 47 E& HI .80 .75 1.07 1.10 .79 Breaking strain in tons. Elongation. Actual. Per square inch. Inches. Percent.- • Teated cold : A 23.66 21.43 29.94 30.4 22.81 29.4 28.5 27.9 I 27.4 28.7 2.17 1.48 2.08 1.84 1.90 27.1 B 18.5. C . 26 D 23 E 23.7 MeKDS 28.38 23.6f p£dJtl ^/e-rr-bi>ite^. J'^iX y//^f ///////// (featCcrtj "mJud Ce^^t^Sj a£bi/fleAM 'tlatid. . &i.am. f^JrvH. Ta^ rtit^ ajbbi^-44Mi4,'itdAeL. V ' 1 (f .^^ -^ \ V J; 1 1 11 jr \ ^^^^"=5?-=^-___l u. NAVAL ENGINEERING IN GREAT BRITAIN. 59 Table XXII. — Elongation of holes at ultimate stress. Specimena. 8 «>.g a O §.4 .a "Prinnhflfl Per emit. 9.5 36.5 22 Si Per cent. 12 43 28.5 44 Per cent. 10.6 35.3 22.6 32 Per cent. 3 26 25 Drilled 44 Some interesting experiments were recently made by Mr. Kirkaldy for Mr. T. W. Trail, for the purpose of ascertaining the effects of bulging stress upon mild steel as compared with iron similarly treated, the ob- ject being to ascertain the behavior of the steel when subjected to the strain it would receive under the circumstances of a vessel taking the ground and resting upon a stone or point of rock. The plates experimented with were four in number, each 10^ inches in diameter afid ^'g^ of an inch thick. Two were of the Steel Com- pany of Scotland's make, and two of wrought iron. They were forced into a ring 7f inches in diameter by means of a steam hammer and punch as shown by Plate 51. The steel disks were dished to a depth of 3J inches without injury, while the iron disks broke badly when dished 2 inches and 2^ inches respectively. Further experiments showed the superior behavior of mild steel over iron plates when subjected to explosive force, by exploding five cart- ridges of dynamite, weighing in all 13 ounces, upon a steel plate three- eighths of an inch thick. The plate was bulged at the center to a depth of about 11 inches without signs of cracking. (See Plate 52.) Among the uses to which steel is being applied is the manufacture of flexible wire hawsers. The British Admiralty have adopted steel hawsers in two of their war-ships, as also have the Germans in one of their corvettes. Thus far, I am informed, the steel ropes have given satisfaiition in the British Navy. The economy of space, strength, and lightness of steel hawsers, in comparison with iron cable, are the prin- cipal reasons assigned for their adoption. Steel bids fair to supplant the heavier iron in cables and rudder chains and the hempen hawsers now in use in the largest ships. Especially when used for towing dis- abled ships iu a heavy sea, steel hawsers would seem to be invaluable. Steel castings are now made which combine soundness with lightness^ strength, and durability in thp most varied forms and dimensions. 1 have seen steel castings of large anchois, propellers, hydraulic cylin- ders, and riveters, gearing of the largest size, steam pistons 78 inches in diameter, and various other species of steam and hydraulic machinery and other machinery, free from blow-holes, with smooth surfaces, and in every way equal to cast-iron castings, besides having the advantage of possessing fully five times the tensile strength of cast iron. The saving in weight of steel over cast iron in pistons 42 inches in diameter has been fouud to be 25 percent., while the saving in a piston of 78 inches diameter amounts to 35 per cent. Steel castings can be produced of any degree of hardness or tough- ness, the deternination of which will depend very much on the char- acter of the work to be performed. Generally, the tensile strength varies from 29 to 35 tons per square inch. The extension, according to the experience of Mr. F. W. Dick, inspecting engineer to the Steel Oompany of Scotland, varies from 36 to 12 per cent, in lengths of 10 60 NAVAL ENGINEEEING IN GEEAT BRITAIN. inches, and from about 17 to 6 per cent, in lengths of 8 inches parallel, while the elastic limit is found to range from one-half to five-eighths of the breaking strain. Steel castings can be -wrought under the hammer, and welded with facility to either steel or wrought iron. Mr. Dick read a paper at the last year's meeting of the Institntion of Engineers and Ship-builders of Glasgow, in which he stated that the difficulty encountered in early attempts to make steel castings of Bessemer or Siemens-Martin metal was the formation of blow-holes^ and that, in the Terrenoire process, this fault is entirely remedied by the use of a silicide of iron and manganese. He said: "The presence of a trace of silicon is found to have the singular effect of preventing that violent evolution of gas from fluid steel at the moment of solidifi- cation"; which evolution otherwise causes the objectionable unsound- ness. He further mentions that in the fluid steel there is carbonic oxide in dissolution which, during solidification, tends to escape, but combines with the silicon, and silica is produced, and afterwards a silicate of iron, which would remain interspersed in the steel were it ndt that the pres- ence of the manganese causes the formation of a very fusible silicate of iron and manganese which passes off into the slag. Steel castings, while cooling, have been found in some cases to un- dergo such a molecular change as to render them wholly unreliable. To restore them to a condition of uniformity, it is necessary that they be carefully annealed. At the works of Henry Bessemer & Co., of Shef- field, several days are taken to anneal heavy castings. As steel must be poured very hot, the molds are lined with gannister, mixed, some- times, with a little burnt clay, and a small addition of old crucible pots, ground. Gannister, with which molds are lined, is a silicious rock found in the Sheffield district, and is considered the best fire-resisting material known. It is taken out of the groiand in large pieces, and broken, and ground to powder by machinery. The powder is then made into a stiff" paste or mortar to form the mold linings, which are practi- cally non-expansive and have a very hard, close texture. Another steel of very superior quality is that known as Whitworth's " fluid-compressed, steel." Its distinguishing characteristics lie in its nnparalleled soundness, and uniformity, and great ductility. It has a tensile strength of 40 to 80 tons per square inch of section depending upon the per cent, of carbon. The method of compression consists in subjecting either solid or cylindrical castings, while in a molten state, to a water pressure of from 6 to 8 tons per square inch. It is consid- ered preferable to cast this steel in the form of tubes so as to afford a greater freedom for the gases to escape from the inside surface as well as from the outside. For shafting, guns, and cylinder linings, solid in- gots are first forged, and afterwards bored out. They are then placed on a mandrel and forged and drawn by hydraulic pressure until they assume the form desired. The advantage claimed for this method is that the stroke of the press is that of a continuous pressure, and is effective right through the mass of the metal, instead of expending itself, like a blow from a steam hammer, within a short distance from the surface. This method admits of the manufacture of hollow steel shafting, by which a saving of 60 per cent, is effected, and a tensile strength as high as 40 tons per square inch, and a ductility of from 30 -to 35 per cent, is gained. The following list comprises a few of Her Majesty's ships Vhich have been supplied with hollow propeller shafts : NAVAL ENGINEEEING IN GREAT BRITAIN. 61 Name of ship. Bsio^bante Inflexible. Iria Mercnry.- Snryalas . "3 1 A '&bb s ■a •1 ■R M _,** fB ^ «« .a o i 1 H ^ H Ft. in. Tons. 75 lli 5 19 283 9 14 es} 139 7 29 139 7 29 76 111 5 19i ■a 3 as o Ton». 2B| ■ 97 43 43 29i Cylinder linings of fluid-pressed steel are now being supplied to all the latest ships of the British Navy. Notable among those so fitted are the following : ^ame of ahlp. Amethyst . Eover Inflexible. Euryalns - . Iria Do Blercnry.. Do Do Audacious Diameter of lining. Inches. 55i 72 70 73 75 36 75 46 21 77 Length of lining. Inches. 44 57i 52i 57i 44 38i 44 355 2b| 461 All the air-vessels for the propulsion of the Whitehead torpedo sup- plied for the English Government are made of this metal. They are tested to a proof pressure of 1,500 pounds per square inch, a pressure which ordinary steel will not endure. Following are the dimensions of these air-vessels : Length, 5 feet 6 inches ; thickness, varying from .25 to .33 inch; weight, 1 cwt., 3 quarters, 11 pounds. Mr. Hotchkiss, patentee of the famous revolving cannon, refuses to use any other than the Whitworth's fluid-compressed steel ; and con firms its great superiority by the statement that as yet he has not had occasion to reject a single barrel. Guns are now supplied with hoops of this metal, weighing as heavy a« 20 tons, and of any required length, the use of which admits of the introduction of fewer parts with a consequent reduction of weight. A great many of the large gun tubes for the British Admiralty are made of this metal, and have given the highest satisfaction. Cylinders of this metal do not fly to pieces when they burst, but simply open out or tear like paper. All the guns for the Brazilian ironclad now building by Samuda & Co., of London, will be composed entirely of Whitworth's fluid-compressed steel. Shells that have produced wonderful results are now made of this metal in accordance with Whitworth's patent process. The gun-makers of England are very much in favor of steel for guns, and all look upon it as the metal of the future for gun construction, from the fact of its great endurance and ability to withstand sudden and vio- lent strains. In support of this it will be in place to refer to some in- teresting experiments made several years ago by Sir Joseph Whitworth to test the strength of metal cylinders by the explosion of gunpowder, which proved conplusively the superiority of his fluid-compressed steel in point of ductility, while it preserves a high tensile strength. 62 NAVAL ENGINEERING IN GREAT BRITAIN. Plate 53 is a longitudinal section of a flnid-eompressed steel cylinder, external diameter 7.83 inches, internal diameter 3.56 inches, showing the arrangement before undergoing the test by gunpowder. Fig. 2 is from a, photograph of the cylinder after having been tested with forty- eight discharged of gunpowder, 24 ounces in each, the only escape for the gases being through a vent one-tenth of an inch in diameter. This specimen is still available for further experiments. Plate 54 is a cast-iron cylinder with a coiled wrought-iron tube inside to represent the proportions adopted in the conversion of the old 8-inch smooth-bore guns into rifled 64 pounders before undergoing the test by gunpowder. The external diameter of the cast-iron cylinder and the internal diameter of the wrought-iron tube are the same as in Plate 53, the thickness of the wrought-iron tube being sixty-nine hundredths of ah inch. Fig. 2, Plate 54, shows the result of firing four charges of 5, 6, 8, and 10 ounces respectively. The cylinder burst into one hundred and eighty-one fragments, of which one hundred and seventy-four « ere cast iron and seven wrought iron. Plate 55 is a cast-iron cylinder of the same diameter as that in Plate 53 before the test by gunpowder. Fig. 2 shows the cylinder after one discharge of 3 ounces of gunpowder. The cylinder burst into thirty fragments. The following particulars I have taken from the remarks of Mr. G. Clanet, of the London Ordnance Works, on Mr. Longridge's paper read before the Institution of Civil Engineers of London in 1879. Table XXIII gives the results of the elastic and ultimate stress of steel when tempered in oil, as compared with wrought iron used at Woolwich, which results Mr. Glanet obtained by direct experiment : Table XXIII. — Stress per sqxiare inch. Wrought, iron used at Woolwich , Oil-tempered steel tubes Oil-tempered ^jackets reheated and cooled iu oil Oil-tempered jackets reheated and cooled in atmosphere Soft steel for exterior rings Elastic. Ultimate. 11 it 25 6» 21 40 18 35 16 32 Table XXIY, from the same paper, gives for comparison the dynamic strain anxl weight of solid guns of cast iron, wrought iron, and steel, guns of Woolwich pattern, and built-up steel guns of Yavasseur construc- tion. The dynamic strain Mr. Glanet estimates to be two-thirds of the static strain. In this table the great difference in weight between the steel guns and guns of cast iron and wrought iron will be noted : Table SXIV. Kiudof gnna, 10-inch caBt-iron gun 10-iuch r olid wrought-iron gun ; 10-inch steel gun , . , lOriDch Woolwich make, mark I 10-inch Woolwich make, mark II 10-inch built-up steel gun, Vavasseur construction 12:iDch 3S-tpn gun, Woolwich construction 12-inch btiilt-up steel gun, YaTasseur construction Inches, 45 45 46 45 45 41 S7.6 45 Tons. 18 18 18 18 18 16.3 38 27 Strength of gun per sqnare inch in bore. ■a o 3 Tons. 5.44 9.97 14.50 23.84 28.62 39.74 30.82 36.13 Tons. 3.6 6.6 9.6 16 19.1 26.6 20.5 , 24.1 O t. ill — 1.3 — 6.B -19. » — ae —16.7 y-u^ z. fu^ House Ex. Doc. 48. Photograph of the cylinder after having been tested with forty-eight discharges of gunpowder, 24 oz. each. PLATE 53. a o o 00 House Ex. Doc. Photograph of the cylinder and tube after four discharges, viz., one each wiih 5, 6, 8 and 10 oz. of gunpowder respectively. PLATE 54. House Ex. Doc. 48. Photograph of the cylinder taken after one discharge of 3 oz. of gunpowder. PLATE 55. ^^^^^ >><^B^'^^^^M^$^^^>^>.'^^^ ^1 ^i ^ "§ NAVAL ENGINEEEING IN GREAT BRITAIN. 6$ Siemens- Martin Steel. — At the Hallside works of the Steel Company of Scotland, so ably managed by Mr. James Eiley, steel is made exclu- sively by the Siemens-Martin process. The works comprise two main buildings arranged as melting shops and mills, with the usual engine* and smith shops for repairs, and a large foundry. In each melting shop there are eight 6-ton and twelve 12-ton Siemens open-hearth melting furnaces. The foundry is furnisHed with two 6-ton furnaces. In con- nection with these furnaces there is a complete set of gas-producers, with all their pipes, stacks, and connections. The casting pits are at the back of the furnaces, one to each, and in them open-topped molds are arranged in series. The steel is tapped from the furnaces into a ladle mounted on a car- riage, which is drawn over the different molds in succession. The ladle's- load of metal is run from the bottom, which is provided with afire clay ring and stopper for controlling the flow. (See Sketch, Fig. 1, Plater 56.) By this means the amount passed is regulated, no slag or dirt is permitted to pass, all risks which would attend the decantation of the metal from the ladle are avoided, and the flow of the molten steel i» completely under the control of one man. Siemens gas-producers (see sketch. Fig. 2, Plate 56) each consist of a hopper-shaped chamber with a small grate at the bottom. They are separate from the furnace and are made sufficient in number and capa- city to supply several furnaces. The coal is fed in from the top through (a), forming a layer usually about 3 feet thick. Complete combustion takes place at the bottom, and carbonic acid gas (C O2) is formed. As this gas passes upward through the kindling coal the coal takes from the gas one atom of its oxygen, thus changing the carbonic acid to carbonic oxide (C O), which, along with hydrocarbons, passes to the reverberatory furnace to undergo complete combustion. To reach the furnace, the gases go through wrought iron tubes at a- temperature of about 400°. This high temperature is preserved in or- der to prevent any inward draughts of air through crevices,, which would cause the combustion of the gas, and thus diminish its heating^ power in the furnace. Plate 57 is a sketch showing the principal ,parts of a Siemens melt-, ing furnace, or open-hearth furnace, as it is sometimes called. The metal lies on a broad shallow bath or hearth composed of a highly re- fractory sand which is fused into a solid mass at a very high heat. The roof of the furnace is shaped like that of a common reverberatory fur- nace. Beneath the hearth are four arched chambers in which fire bricks are loosely stacked so as to allow a free passage of air or gas be- tween the bricks. Two chambers permit the passage of air, and the other two of gas from the gas-producers. . In entering the furnace, the gas passes through one chamber of hot bricks and the air through the adjoining one. At one end of the fur- nace they mingle, having by this time attained a high temperature^ Combustion immediately takes place ; the flame, as it sweeps along to the other end of the furnace, is directed downwards, and the result- ant gases pass out of the furnace at that end, to make their final exit to the chimney through the other two regenerative chambers, the bricks stacked in which become highly heated thereby. In the course of half an hour or so, when the first set of chambers- have become cooled and the second heated, the action is reversed by means of two valves, one at the end of the regenerators, near the flre^ and the other at the cool end next the chimney. This recovery and "64 NAVAL ENGINEERING IN GREAT BRITAIN. storing up of what would otherwise be waste heat effects a great sav- ing of fuel, and renders easy the attainment of a high temperature. To trace the practical working of this process: About 9 tons of hem- «,tite pig iron are charged into the furnace. In about three hours this mass of metal forms a liquid bath, into which is thrown about 2J tons of the hematite ore, rich in quality, tlje analysis of which I give below. The oxygen of the ore combines with the carbon of the pig and escapes as carbonic oxide, causing a violent ebullition, which serves the pur- pose of thoroughly mixing up the melted metal and bringing it into •contact with the ore. When the metal ceases to boil the process is practically at an end. Spiegeleisen and ferxomanganese are added in ■certain quantities, and the metal is then run into the molds. The fer- romanganese is sometimes added while the metal is running into the ladle, the practice at the Hallside works, Scotland. Analysis of Somoroatra iron ore from Spain, as used hy the Steel Company of Scotland. Per cent. Peroxide of iron 7^. 86 Oxide of manganese - 1. 36 Alumina 1. 35 Lime .' - 4.71 Magnesia 2. 00 ■Silica 5. 35 Carbonic acid -.. 6. 38 Phosphoric acid .05 ■Sulphuric acid .04 Combined water ; 3. 19 Moisture 3. 05 100.24 The metallic iron in the above analysis is about 51 per cent. From Mr. Hackney's able paper, read before a meeting of the Insti- tution of Civil Engineers of England in 1875 on the manufacture of steel, I give the following analyses of spiegeleisen and ferromanganese 418 used at two of the leading steel works of the world : Analysis of spiegeleisen smelted from Spanish ores and used by the Landore Steel Company of England. E. KiLET, anatyat. Per cent. Oarbon 4.538 ■Silicon 0.041 Manganese 11.798 -Sulphur 0.010 Phosphorus ^ .. 0.084 ■Copper 0.015 Iron 83.777 100.247 Ftrromanganese from Terrenoire. A. Willis, analyst. Per oent. 'Carbon 6.000 •Silicon trace. Manganese 46. 600 Phosphorus 0.175 3[ron 471225 100. 000 ^U^X^cuMMi -^uUnM^-. ^^ " I ^^^^^^^'^>^^^'^kvv^^^'K\^'^^^ ■ ^^^v^^^^ ofHtltUjtci, ^rtqlan'ci. H. EX. DOC. 48 NAVAL ENGINEKR1N6 IN GREAT BRITAIN. 65 The richest specimens contain as much as 80 per cent, of manganese. Bessemer steel is made directly from the crude pig iron, the essential part of the process consisting in cleaning the iron from its various im- purities by subjecting it, while in a liquid state, to the action of small streams of air. Plate 58 is a drawing of a 3-ton converter in use in Messrs. Bessemer & Oo.'s steel works, Sheffield, England. The converters vary in size and are capable of taking from 3 to 15 tons. The outer casing is com- posed of strong boiler plate riveted together and lined about one foot thick with powdered gannister, and is made to revolve on trunnions by hydraulic power. In the bottom of the converter are a number of tuyeres which are perforated with small holes about three-eighths of an inch in diameter. Process. — While the pig-iron is melting in ordinary round blast fur- naces or cupolas, the converter is being heated to a red glow by a fire inside. The converter, which can be rotated by means of gearing through an angle of 180°, is capsized and the fire allowed to fall out. While in a horizontal position, the cupola is tapped and the liquid iron •allowed to run from it down an open channel lined with fire-resisting material. The blast from the blowing engine which passes through the hollow trunnions into the tuyere box is turned on before any metal is run into the converter. This is continued without intermission until it falls again, in order to prevent the metal from percolating into the air- chamber. The pressure of the blast requires to be strong and is usually about 20 pounds per square inch. As soon as the blast is turned into the molten iron, a sudden roar takes place, and impuritjps and sparks from their combustion are thrown out into the open air. The blowing goes on until the red glare passes away. This operation of removing the carbon, silicon, and other .impurities occupies from fifteen to twenty minutes, the time so occupied depending very much upon the force of the blas't and the quantity of metal. The converter is then lowered to receive a charge of spiegeleisen or ferroman- ganese. A rapid combination takes place, and the molten iron becomes Bessemer steel. This accomplished, the molten steel is poured into a ladle fixed to one end of the top of a hydraulic lift. The steel in this ladle is then violently agitated by a mechanical agi- tator, the invention of Mr. W. D. Allen, of the works. (See Plate 59.) For this machine Mr. Allen claims the production of a more complete and reliable diffusion of the spiegeleisen and the liberation of occluded gases, thus producing sound castings free from honeycombing. The agitator has the form of a screw propeller blade, and, with the rod (b), is protected by a covering of gannister. The ladle is swung around and from it the steel is poured into a series of ingot molds arranged in the curve of the pit. As the metal solidifies in a few minutes, the ingots may be conveyed, while red-hot, to the rolling-mill or hammer shop, where they are fashioned to various shapes for the purposes for which they are intended. COBEOSION. The British Admiralty exhibited at the Glasgow Naval Engineering Exhibition a series of specimens prepared and used in connection with the investigations conducted by the Boiler Committee, for the purpose H. Ex. 48 5 66 NAVAL ENGINEEEING IN GREAT BRITAIN. of inquiring into the causes of the deterioration of the boilers of the British I^avy, and of discussing measures to increase their durability. The specimens exhibited were taken from different boilers, and from those parts that are most subject to corrosion, and showed quite clearly the different kinds of corrosion and coniiuent honeycombing, so fre- quently seen on the internal surfaces of marine steam boilers when made of iron. Having looked over the early report of the committee soon after it was published, in connection with some experiments of my own on this subject, I found the specimens quite interesting. From the late report of the committee, so ably presided over by Engineer-in-Chief Wright, it would seem that the principal cause of the deterioration of marine steam boilers is the injurious action of air and carbonic acid which is present in the water pumped in to keep the density of the water in the boilers within the prescribed limits, and to supply deficiencies arising from leakage, &c. The committee, in view of the injury resulting from the action of moist air upon iron, recommend that the boilers be emptied as seldom as possible, and call special attention to the importance of keeping them tight. Higher densities than are usual in boilers the committee have found to be beneficial, as tending to cleanliness and preservation ; and their recommendations, which have been adopted by the Admiralty, are that no blowing of water out of the boilers Sihould take place until the density reaches two and one-half thirty-seconds, nor should the density exceed three thirty-seconds in boilers of engines which are fitted with jet condensers, nor four thirty-seconds where surface condensers are fitted. In view of the gases and salts held in solution in salt water they par- ticularly call attention to the common practice, when the engines are stopped, of ])umping cold sea-water into the boilers to reduce the den- sity and prevent the steam from blowing off at the safety-valves, as be- ing detrimental in respect of both cleanliness and preservation. The following interesting series of experiments, which occupied a pe- riod of twelve months, were prosecuted by the committee referred to for the purpose of showing the preserving effect of water carried at high densities. This they accomplished by suspending round pieces of polished iron of equal size in glass bottles, each containing water at at- mospheric temperature, the pieces of iron being connected with each other by a brass rod. Kind of water. Ten thirty-Beoond density s «' Six thirty-second density i 6 1 Three thirty-second density _" } 22' 7 IVesh water . 13.2 SiBtilled from fresh water ! . 1 ! 1 . . . . . ! ! i ^ ! I 16 Distilled ixom saltwater '.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'" \ 12' 105.1 114. 5 238.4 247.8 304.1 225.2 The increased economy resulting from a higher density of water in marine boilers, as indicated by the ordinary hydrometer, coupled with proper lubricants for the internal surfaces of the cylinders has not, it NAVAL ENGINEEEING IN GREAT BRITAIN. 67 would seem, received tbe attention it should have received from writers on the economy of the compound engine in considering the reduced cost of coal per indicated horse-power which has taken place in the compound engine within the last ten years. This econom/ is apparent when we consider that water is carried in the boilers of a density as high, in many cases, as flvethirty-seconds ; and, in fact, in the mer- chant marine, where vessels steam continuously, it is not difQcult to show cases in which no change of the water in the boiler is made for more than a week, other than to supply deficiencies from slight, un- avoidable leaks. As to the corrosion of steel when used for boiler or ship construction, I have no information to communicate to show that steel is in any way more susceptible to corrosive action than iron. On the contrary, the leading engineers with whom I have had the pleasure of conversing, among ihem the o£fi(;ers of the Board of Trade and Lloyd's Eegistry, seem unanimous in the belief that mild steel, such as is ijroduced by well-known maker^ cannot but possess greater immunity fropi corrosion than iron, from the fact of its superior homogeneity and freedom from siliceous matter which, when contained in iron, leaves an opening for chemical agencies to penetrate. This fact alone should be a strong rec- ommendation of steel for general construction purposes. From my own observations, I am of the firm belief that this metal is no more subject in any way lo corrosive action than iron. In iron cor- rosion is undermining and deceptive, which fact may explain many strange and apparently unaccountable cases which have come to the notice of engineers. This, however, is not the case with steel, as, in that metal, corrosion takes place on the surface and is always visible. But until practical experience is obtained from careful and intelligent management, with a careful record of the particulars attending each ship or boiler, which will require some few years yet, no positive information can be given as to the real merits of steel over iron in respect to corro- sion. A great many authorities could be quoted in evidence that steel is no more susceptible to corrosion than iron, among them notably Mr. Parker, who, at a recent meeting of the Iron and Steel Institute, stated that at present there are some eleven hundred steel marine boilers run- ningj the majority of which come periodically under the inspection of the engineer surveyors of Lloyd's Eegistry, and the results of their in- spection go to show that steel boilers behave, with respect to corrosion, about as well as iron boilers.' Two important series of experiments conducted by the Boiler Com- mittee with mild steel and iron insulated and suspended in a boiler at the Sheerness dock -yard, showed, after having been suspended in the steam space or in fresh water, that they had suffered to an almost equal extent ; but in salt water, the corrosion appeared to be rather less in the steel than in the iron. It was also found that the corrosion of the specimens of iron plate in contact with steel plate or steel rod in salt water is much greater than that of the steel, indicating a decided galvanic action between the two metals. In fresh water this action is not apparent between iron plate and steel plate. Reference to the above-described experiments is made for the reason that some builders prefer to use iron rivets for riveting steel plates. The practice, however, of the foremost Clyde builders is to use steel rivets and not iron. To escape galvanic action between the partially detached mill scale or black oxide and the plate, aU steel plates used in the construction of 68 NAVAL ENGINEEEING IN GREAT BRITAIN. ships and boilers for the English ITavy and merchant marine have the oxide removed by pickling or by the ordinary process of hammering and chipping. The pickling process is employed by the English Admiralty and has to be resorted to on account of their ships being built under sheds at the government dock-yards. At the works of Messrs. E. Napier & Sons, in Glasgow, two large wooden troughs, about 20 feet long, 5 feet wide, and 5 feet deep, are im- bedded in the ground side by side and a crane is fixed in such a posi- tion that it wiiriift the plates from where they are stacked into either trough. The troughs are fitted with iron racks at one end, placed ver- tically, so that the plates may stand on edge in the racks without touch- ing each other. The first trough is filled with a solution of muriatic acid. After the plates have been in this for four or fl\e hours, they are lifted out and the whole of the scale comes oS easily by simply brush- ing with ordinary brooms, leaving the plates clean and bright with a beautiful silvery appearance. To remove any acid that might remain, the plates are then dipped into the second trough which contains pure watei-. Alter this they are stacked on edge to dry. As to the protection against corrosion afibrded bj' zinc placed on the inside of boilers, good results were observed when it was placed below the water line, and its adoption has been recommended. Concerning the beneficial results obtained from zinc so placed, I have extracted the following from the Boiler (Jonimittee's report : " The use of zinc in the manner now adopted. for the Koyal Navy has been attended with most beneficial results. With the slabs fitted in good metallic contact, and suitably distributed, the protection afforded by it is most marked. In the troop-ships and some of the tugs in which the result of tbe application of zinc has been carefully watched, no ap- preciable corrosion below the water line can be seen, and the interior surface of the iron may be said to be quite free from any indication of iron scale. "Casts taken of portions of the bottoms of the boilers in the surface- condensing tug Malta show the rivets and plates after four years (the boilers were first fitted when new) to be still quite perfect. In the tug Orinder, in which one boiler was fitted with zinc and the other not, casts of portions of the bottoms of the two boilers where the protection by lime scale is not so good, and where they are. subject to the wash of the water, show the rivets and plates to be perfect in the boiler with zinc, but the rivet heads to be considerably corroded away and the plates pitted in that without zinc. " The protection aiforded by zinc is efficacious against corrosion be- low the water line, whether arising from the. water itself, from galvanic action, or from the air admitted with the feed. " Zinc is thus a most effective means of preserving boilers ; and it is desirable to use it until, by improved methods of treatment, or other protective measures, the corrosion of the iron can be so far prevented that its cost need not be incurred. " The committee recommend its general adoption ; and they consider it of so much importance that they have described below in consider- able detail the quantities required, the mode of fitting the slabs in the boilers, and the more important peculiarities of its behavior." Summarizing, the committee give the following as the results of their inquiry, together with the quantity of zinc recommended for the boilers fed from surface and jet condensers : CO o a O X Mxahai^ ^^ m Tr^ ^■■■ffl ^ /2'; >1 B ^ -^s3 ■^ ■^-l |o o.o oooocooj oM), S-n^tiM v dJf.wvu. H.EX DOC 48 NAVAL ENGINEERING IN GREAT BRITAIN. 69 " (a) The size'of slab 12" x 6" x 1", now adopted in the Eoyall^avy, has been found suitable and convenient. " (6) The arrangement of slabs in one class of new boilers for Her Majesty s ships is shown by Plate 60. " (o) Rolled zinc is more suitable and probably more economical than cast zinc. " [d) The protection afforded by zinc is more prolonged in hot water than in cold water. " {e) The form of fitting shown by Plate 61 for attaching the slabs to the stays has been found convenient and satisfactory. " (/) Zinc affords no direct, if any, protection in the steam space." If fed from surface condensers. (a) In new boilers, or boilers wbicb have not been in use lately. (b) In boilers which have been f in use for sometime, but have I not lately bad zinc iitted. See ] (d). [ (c) In boilers which have been f in constant use for some time, J and have had the zinc renewed ] an necessary. See id). [ id) Boilers in which the firee are alight, as a rule, less than one- third of the time during which the water is in, should be fitted with the same quantity of zinc as new boilers. 7 square inches per I. H. P., or 1 slab for 20 1.H.P. ,or 1 slab for 50 square feet of tube surface. 6 square inches per I. H. P., or 1 slab per 25 1. H. P. , or 1 slab per 60 square feet of tube sur- face. 5 square inches per I. H. P., or 1 slab per 30 I. H. P., or 1 slab ^6r70 square feet of tube sur- face. If fed from jet condensers. 7 square inches per I. H. P., or 1 slab per '.iO I. H. P. , or 1 slab per 50 square feet of tube sur- face. 5 square inches per X H. P., or 1 slab per 30 I. H. P., or 1 slab per 70 square feet of tube sur- face. 3 square inches per L H. P., or 1 slab per 50 I. H. P., or 1 slab per 120 square feet of tube surface. ^ As to the method of attaching the zinc to the boilers the committee state as follows : "As a rule the mode of fitting shown in Fig. 70 is applicable to all parts of the boiler, especially those which are not accessible, such as amongst the combustion chamber stays. " The bar of iron may be of any length, or, if necessary, made up of lengths bolted together, and in that way the slab may be suspended in quite out-of-the way places, whilst the connection with the stay is kept within easy reach. " It is immaterial whether the stay with which the connection is made be above or below water so long as the contact and grip there and at the other connections are satisfactory. "All that is necessary in placing the slabs is to make sure that there is good contact and a firm grip at the slab, at the stay, and at all inter- mediate points of connection. '* It is also immaterial, so far-as the action of the zinc is concerned, whether the connection of the strap with the boiler be made by clasping the stay, as shown (Plate 61), or by bolting the end of the strap to the shell ; provided, always, the surfaces in contact be bright. " The points of attachment must be decided on grounds of conve- nience. '' It will sometimes happen that this arrangement of strap will be lessi convenient than if the zinc were simply bolted on a stud screwed into the shell in the manner recommended by a member of tbe committee, (See third report of Admiralty Committee- on Boilers, 1877, p. 349.) Where that is the case the zinc may be attached by means of a stud screwed into the j)late, or by bolting the zinc directly to the plate. (See a a' Plate 60.) If a stud be used, the plain pare of the stud (say 3 or 4 70 NAVAL ENGINEERING IN GREAT BRITAIN. inches long) between the zinc and the plate should be square, to afford facilities for securing it in place. " The zinc should be attached to the end of the stud by a screwed nut, so that it may be renewed without removing the stud." The eflQciency of zinc is sometimes affected by impurities, such as lead or iron ; and for this reason the Boiler Committee recommend rolled zinc, on account of its freedom from impurities and its closer grain. Further experiments showed that the benefit of zinc arose from its forming a harder and more adherent lime scale, and that the red lead used in making the joints of the underwater doors tends to become de- teriorated when zinc is fitted. At the Naval Exhibition Prof James Young, F. E. S., LL. D., showed specimens of iron wire which had been immersed in sea-water in which there was lime present. The specimens, after four years' immersion, showed no signs of corrosion. This experiment demonstrates that iron is not attacked by sea- water if lime be present, so as to make the water alkaline. Other alkalies, as potash or soda, Professor Young found to have the same effect, but lime is the cheapest. It was first applied by Professor Young in a composite yacht, the bilge-water of which used to be very red with iron rust; but after the application of the lime it soon became colorless, and remains so to this day. The British Admiralty use lime in the bilge-water of aU their iron- built ships. A method for the prevention of fouling, as well as for the preserva- tion of iron and steel hulls, patented by Mr. J. Jepson and Mr. C. F. Heuwood, of London, which was called to my attention both in England and Scotland, seems to possess merits which will be of great value to ship-owners, as well as to navies possessing war ships with iron and steel hulls. The method consists in attaching zinc sheets mechanically, by an alloy, to the plating of the ship at spots nine to twelve inches apart, which plates are to be brightened by a dynamo machine made for the purpose. Experiments already made by eminent chemists have satisfied the patentees of the chemical action of the zinc upon the iron. The hull of the yacht Bessie, belonging to Mr. John Clarke, of Paisley, Scotland, was covered to 6 inches above the water line with zinc sheath- ing more than eight mouths ago, and from a letter I recently received from her designer, Mr. G. L. Watson, of Glasgow, I understand the zinc is doing excellently, and is still quite clean. Satisfied with the re- sults already obtained from this method, Mr. Denny, the eminent Scotch builder, is applying it to a large mail steamer building by his firm. ADMIRALTY EXPERIMENTAL WORKS. Through the courtesy of Mr. X. Baruaby, director of naval construc- tion, I visited the Experimental Works at Torquay, England. These works are under the immediate charge of Mr. E. B. Fronde, son of the late William B. Fronde, who rendered so much valuable in- formation to the science of naval architecture and engineering by deter- mining, by means of model exi)eriments, the tine resistance that a ves- sel moving through the water has to overcome at various speeds. The models referred to are made of bard jiarafline. Tliey are hollow, and vary in length from about 8 to 25 feet, and have a thickness of IJ inches. The larger sized models, like that of the City of Eome, on ac- count of the limited length of the molding-box, are juade in halves and joined together. The mold is formed of plastic clay contained in a rect- NAVAL ENGINEEEING IN GREAT BRITAIN. 71 angular box, aud is worked into shape with transverse templets a lit- tle larger than the intended exterior of the model. A corresponding set of transverse templets, joined together by thin laths, are made to represent the interior of the model. This skeleton is then covered with thin cotton cloth and washed with a double wash of softened clay and an intervening wash of plaster of Paris, so as to render it paraffine-tight. The parafftne is melted in a long rectangular box by a series of steam- pipes and heated to a temperature high enough to cause it to run freely into the space between the mold and the core. The core is loaded with weights to keep the model down. Cold water is run into the core to cool the parafiine as well as to assist in keeping the core in place. The time usually occupied in preparing the mold is one day, and on the next day it is cool enough for shaping. The models in their rough state are taken to a shaping machine of ingenious mechanism, the' de- sign of the late Mr. Froude. They are modeled on this machine to suit the lines of the ship by a pair of revolving cutters, revolving at a very high rate of speed on a vertical spindle. The principle of this ma- chine is not unlike that of the best of our wood-shaping machines. The model, which is securely fastened to the planer-bed by lugs on the gunwale, passes through between the cutters, and by following closely a line on a small scale templet, which travels proportionately with the speed of the model, the desired water-line is traced upon the model. After one water-line has been thus cut from end to end, the model is raised through the necessary vertical distance by turning the elevating screws of the table, in order that the above described operation may be gone through with again to make the next water-line. The model is then finished by hand and burnished over with a blunt tool to fill up the minute pores. The whole system admits of doing the work so perfectly that Mr. Froude has stated that when models are loaded to their calculated displacement they are found to come out cor- rect within less than one five-hundredth. The experiments are performed in a tank about 300 feet long, 30 feet wide, and 10 feet deep. Suspended about two feet above the water is a railway about 3 feet wide. On this railway is a truck driven bj' an engine having a governor of the most delicate construction, the pro- duction of the combined skill of Mr. Froude and Sir William Thomp- son. The variation of a revolution in the engine is noted by a mercu- rial column actuated by a pressure of water trom a very small centrifu- gal pump driven by the main engine. The model, floating underneath, is- attached to the dynamometer truck by the most delicate knee-jointed rods. Several runs are usually made to obtain a curve of resistance. The particulars of these runs are recorded on a traveling cylindrical appa- ratus covered with a sheet of paper acted on by pen points, which, ac- cording to the motion of the model, record by a series of dotted lines a history of each journey. In order to test the action of the screw propeller, there are provided means of attaching behind the dynamometer truck another truck, which has a screw-shaft protruding forward and in front of the truck, carry- ing a screw which can be speeded by a belt driven from the wheels of the truck. The screw can be placed close to the model, and may occupy the same relative place as if it were propelling the model. By a series of diagrams, taken in the same manner as for determining the resistance of models, the proi^ulsive force of the screw is deter- .mined. 72 NAVAL ENGINEERIISG IN GREAT BRITAIN. This most excellent system of model experiments, which provides a means of ascertaining the resistance of hulls of the most varied propor- tions of length to breadth, displacement, and propelling power, has been applied to the designs of all the latest war ships of the British Navy, notably so in the case of the Polyphemus, Iris, Leander, and Mer- cury. When the lines of foreign war ships of unusual design, and of certain fast ships of the merchant marine, can be obtained, models are made and tested in the manner described, and the records kept for the information of the Admiralty. Mr. Froude suggests, for the latest and most approved admiralty de- signs, changes which he deems necessary to meet essential requirements regarding speed, form of hull, &c, before the form of least resistance is discovered. The resistance of the hull of the Eussian imperial yacht Livadia, and the power necessary to drive it at a speed of 14 knots were determined by model experiments by Dr. Tiderman. Her builder, Mr. Pearce, sub- sequently made a series of experiments with a steel model on Loch Lo- mond to satisfy himself on these points. His model is now lying at the yard of John Elder & Co. Mr. Purvis, who was associated with the late Mr. Froude, stated be- fore the Glasgow Engineering Exhibition in his very clever lecture upon the resistance of ships, that when the speed-producing components shall have been more thoroughly investigated ships will be built of greater relative breadth. Several private builders on the Clyde are at present considering the advisability of establishing experimental tanks. Mr. William Denny, of Dumbarton, Scotland, I have heard, will be the flrst to inaugurate such an enterprise. If there were such experimental works at the Naval School they would not only be conveniently near the Navy Department, but would work incalculable benefit to the students of enffineering and seaman- ship, and would also give ofiflcers of the Navy an opportunity of having readily determined the merits of any new designs which they might possess without putting the government to the expense of building a full-sized ship, when perhaps a change in the form of the hull which such experiments might suggest would effect both a considerable reduc- tion in the resistance of the hull and of the power required. MERCHANT STEAMEES FOR WAR PURPOSES. Since the trials made by Mr. Barnaby, director of naval construction of the English Navy, to test the resistance offered by a mass of coal with thin iron plates interposed as a protection to the vital parts of unarmored vessels, the English Admiralty have given the subject seri- ous thought. The trials referred to, it will be remembered, were carried out some three years ago by fitting up one of their war ships so that she con- tained from 8 to 10 feet of coal in breadth, within which were intro- duced several three-eighth-inch iron boiler plates. She was then fired at with a 7-inch gun. The shot failed to penetrate the coal and the iron plates to any great depth. Shells also were fired with different charges, ■ but failed to set the coal on tire. In view of the satisfactory results obtained from coal when placed along the sides of the ship as a protection to the machinery, the British Admiralty pay special attention to this fact, not only in their latest designs of unarmored cruisers, but more especially in all mer- NAVAL ENGINEERING IN GREAT BRITAIN. 73 chant steamers constructed in accordance with the Admiralty require- inents. The leading features of the requirements are that ships shall have a speed of not less than 12 knots per hour, and be properly divided by water-tight bulkheads, and have double bottoms ; the water-tight sub- divisions must be such that the vessel may float in safety when any sin- gle compartment is bilged. To meet the above conditions in ships so constructed, the water-tight and fire-proof doors of improved pattern have been increased in num- ber, and, when practicable, are so arranged as to be operated from the deck above at short notice ; also, thq number of water-tight compart- ments are greater than is usual in merchant ships, the divisions are carried up to the upper deck, and in some the arrangements are such that they can be still further divided, which quality will be of service in the event of the' vessel being fired into and damaged below the water line. The decks of some of the high-speed ships are composed of heavy iron or steel, and built sufiiciently strong to carry heavy guns, and the bows also are strengthened for ramming, which arrangements render the vessels very valuable for offensive and defensive operations. It has been already mentioned that the English Admiralty have con- sidered the advantages of the forced blast system in connection with its adaptation to the swiftest modern merchant steamers in case of war^ with a view to raising their speed a knot or two above their present maximum, and thus to be capable of outdistancing the swiftest un- armored or armored cruisers of an enemy. It is fair to suppose that among the many objects kept in view by the English Government in the ready fitting out of merchant steamers for war purposes are included the protection afforded to the machinery - by coal or other substances ; the greatest number of guns that can be carried with Safety ; the introduction of wider coal-bunkers, shell-proof gratings, and bow torpedo tubes for discharging the Whitehead tor- pedo ; also the fitness and adaptabilty of ships on their list for special purposes, such as carrying stores aud troops from distant ports; as dispatch vessels for the commander of the fleet ; while the larger and swifter ships would be employed to act on the offensive as well as to protect themselves on the ocean, in carrying on regular trade. And, in connection with this important question, it is safe to say that England possesses today in her merchant marine alone a navy which, were she called upon to defend herself, would astonish the world, from the large number of high- speed ocean steamers at her command that could be converted at the shortest notice into powerful unarmored cruis- ers. One of the latest ships so constructed is the Stirling Castle, built by John Elder & Co. for the China trade. She is 436 feet long, 50 feet beam, 33 feet deep, indicated horse-power 8,508. The engines are Messrs. Elder & Oo.'s three-cylinder type, and similar to those of the steamship Alaska of the Guion line. She maintained an average speed of 18.1 knots for six hours consecutively, on her first trial, which proves her the fastest ocean steamer afloat. The following results were ob- tained while running the measured mile : M. Sec. Kflots. Firatrun 3 13 = 18.652 Second run .• 3 20 = 18.000 Third run 3 12 = 18.75a Fourth run 3 18 = 18.181 Fifth run 3 13 = 18.652 Sixth run 3 18 = 18,181 74 NAVAL ENGINEERING IN GREAT BRITAIN. Admiralty mean average 18.418 knots per hour, Mr. James Dunn stated in a paper read at this year's meeting of the Institution of Faval Architects that there are sixty-five steamers of con- siderable coal carrying power that possess an ocean speed of 13 knots and upward, and that thirty-five of these have a speed of 14 to 17 knots and upward. The Peninsular and Oriental line alone has some forty- eight steamers whose speed is over 12 knots ; and, though I am not pre- pared to say that all these ships were built in accordance with the re- quirements of the English Admiralty, there is no doubt that the govern- ment are cognizant of the degree of fitness of every vessel built in the kingdom for any duty that may be required of it in time of necessity. It would seem that our own government might find subjects for se- rious consideration in the questions here hinted at, as well as a model for imitation in the studied manner in which it is certain that the Eng- lish Admiralty are working up a system by their careful attention to the -details of construction, arrangements, and adaptability of every merchant steamer built. The extent to which England depends upon the rapid and effective conversion of her fleetest merchant ships into war steamers is perceived when we consider that she has but two high gpeed armored cruisers, of very limited coal capacity, and three others n course of construction. EUSSIAN IMPERIAL YACHT LIVADIA. At the Glasgow Naval Exhibition, Messrs. John Elder & Oo. exhib- ited a full model of the yacht Livadia, which was highly praised for the skill and workmanship displayed in the fulfillment of every minute detail. The yacht, although frequently mentioned in the columns of the London Engineer and Engineering. I have referred to here by giv- ing the sketches in Plates 62 to 66, reduced from the oflcial drawings, together with a few particulars furnished by Mr. Pearce, the head oi the firm : Extreme length, 266 feet. Length between perpendiculars, 246 feet. Extreme breadth, 153 feet. Mean draught, 7 feet. Area of immersed midship section, 1,046 square feet. Displacement in tons, 4,400. Mean indicated horse-power on trial, 12,354. Mean speed in knots, 15.77. Type of engine, inyerted cylinder. Number of cylinders, 9. Diameter of cylinders, three, 60 inches ; six, 78 inches. Diameter of air-pump, 2 feet 4 inches. Diameter of feed pump, 7 iuches. Area of condensing surface, 19,210 square feet. Number of crank pins, 9. Diameter of crank pins, 17 inches. Length of crauk pins, 17 inches. Diameter of tunnel-shaft. Hi inches. Number of propellers, 3. Material of propellers, manganese bronze. Diameter of main journals, 16 inches. Length of main journals, 19 inches. Number of blades on one propeller, 4. Diameter of propellers : First, 16 feet ; second, 16.5 feet. Pitch of propellers: First, 19 feet; second, 20.5 feet. Number of boilers: Eight, double ended; two, single ended. Diameter of boilers, 14 feet. Leugth of boilers: Of eight, 15 feet ; of two, 8.5 feet. Total area of grate surface in square feet, 1,287. H. EX. DOC. 48. LbQ ?^LS H.EX.D0C.48. : .lE^,' .'lift^^^toi< r ^ / v3 GO o a a X UJ NAVAL ENGINEERING IN GREAT BRITAIN. 75 Total area of heating surface in square feet, 32,470. Number of smoke-pipes , Three, oval. Diameter of smoke-pipes, 14 feet li inches by 7 feet li inches. Height of smoke-pipe above grate bars, 66 feet 9 inches. The turbot-like portion of the vessel is built of steel and has a double bottom, as will be seen by reference to Plate 67. The double bottom is divided into forty water-tight compartments and extends throughout the flat portion of the ship. The two vertical bulkheads (a) and (6) (see sketch of the midship section, Plate 63), running right around the hull proper, further subdivide the space be- tween the hull and the outer skin into forty other compartments. It was several of these compartments that were damaged on the passage from Brest to Ferrol. (See Plate 64.) The yacht's engines, which were designed by Mr. A. D. Bryce, di- rector of engineering for Messrs. John Elder & Co., from an examina- tion of the working drawings, appeared, as to the manner of erecting them in the ship, to be somewhat different from anything I had ever seen. Steel was used largely in their construction ; and the foundation, which is of steel, forms part of the double bottom. The tunnel-shaft bearings, in order to give suflacieut immersion to the screw propeller, were worked into the double bottom. The method of placing the screws so low down is another important feature in the design by which the efficiency of the propellers was so well secured, without a precedent to guide the designer as to their pro- portions or positions. The Livadia, although designed for the Ozar of Eussia, was intended by her designer to demonstrate the capabilities and qualities of a very broad and shallow ship to carry very heavy guns on a steady guh-plat- fortn with a minimuin of armored surface in proportion to the displace- ment. An important feature is developed in the difficulty of piercing an ar- mored turbot-shaped hull like that of the Livadia, which rises from the water at an angle of about 18°. Sir Edward Eeed, in a letter to the London Times, compared the Li- vadia with two of Her Majesty's iron-clads of approximately equal power and displacement, as will be seen from the following table : Name of vessel. Ik .2o| 1 FeDelope .. To-ni. 4,394 4,420 4,700 4,720 4,703 4,770 4,000 4,500 KnoU. 12 7 Livadia. , 13 12 I/ivadia - . 12.5 In consideration of the trifling difference between the Orion and Li- vadia in the power required to_ attain the same speed, 12.5 knots, it would seem that, to have at command for use when deemed of service the advantages to be derived from a much higher rate of speed, even at unusually great cost, which, in a war ship of the Livadia design, is very high in proportion to the displacement, would be a matter of the first importance in war times. On the matter of war-ship economy. Sir Edward Eeed has forcibly re- marked : " Economy consists in accomplishing your object by the easi- est and cheapest method; the neglect of your object and the attainment of Ytj NAVAL ENGINEEEING IN GREAT BRITAIN. something you do not require is extravagance, however disguised. The disregard of this principle has, in war-ship construction, cost the nations of Europe many a million." It is suggested that, for the protection of harbors like those of Sau Francisco, New York, and Boston, armor clad vessels possessing the leading features of the Livadia could be constructed which would meet every requirement to secure safety against destruction by an enemy armed with the latest artillery of the heaviest construction.' The speed of 12^ knots, mentioned as having been obtained on an ex- penditure of 4,500 horse-power would appear to be all that would be re- quired for that kind of service. To meet this requirement, the weight and space occupied by the boil- ers and engiues could be largely reduced by the introduction of the forced blast system, by which also the indicated horse-power could be increased oae-'third with no greater increase than one-third in the coal consumjition. By this forced blast system there would be a great saving of weight and space from the small locomotive boilers which could be used, besides the advantage of having the boilers placed low down ; and. when com- pared with the Livadia, there would be the saving in weight and space due to the difference between the machinery and boilers necessary to develop 12,000 horse-power (which, iu the Livadia with natural draught is necessary to obtain a sjjeed of 15.4 knots) and the machinery and boilers sufficient to develop the 4,500 horse-power of the supposed type under consideration. This saving of weight would admit the covering of the vital parts of the ship with heavy compound side-armor and a deflecting steel-armored deck, something after Passed Assistant Engi- neer Clark's system. The vital parts could be further protected by fill- ing the side compartments with coal, which has been already mentioned as having great shot- resisting power. It would seem that a ship so constructed could carry the heaviest steel guns of the largest caliber, and also a number of high speed tor- pedo-boats inside, which could be launched at short notice. Two or three guns of the Hotchkiss or i^Tordenfelt pattern could be so arranged inside of the ship as to be raised sufficiently for discharg- ing by apparatus on the principle of the shot-lift of Sir William Arm- strong & Co., which, aided by the curvature of the deck, would give great opportunity for training and depressing the gun for firing into torpedo-boats attacking alongside. In view of the evident advantages set forth, Sir Edward Eeed and his partner, Mr. F. P. Elgar, are about to enter into more exhaustive calculations as to the extent to which vessels of the Livadia design can be made available for war purposes. Table XXV.— ^reroye contumption of ooalper indicated horse-poiver per hour, by iteamshipt with ccmpound engines in l(yng sea royages, by F. C. Marshall. 2.21 2.46 3. IJC5 2.77 1,250 29 2.8 1,230 28 3.917 4,900 3.9 93 3.85 820 16.76 4.45 730 15.1 4.03 771 16 3.89 1,900 40 4.0 1,850 40 5.0 270 7 4.06 900 6,300 24 2.026 3.09 137 1.83 1.839 1.84 2.36 1.85 1.647 1.85 2.26 1.87 2.35 1.89 2.05 1.90 1.702 1.90 1.S73 1.90 2.34 1.90 2.58 1.93 1.70 1.94 2.36 t2.0 1.44 t2. 125 1.316 t2. 25 1.23 t2.25 1.24 1.828 2. 178 1.77 2.2 1.90 2.02 1.92 2.32 1.93 2.4 1.96 1.986 2.01 1.95 2.25 2.22 2.026 2.096 2.035 I 1.52 Class A. — Compound eDginifl wiHi ODehigli and onn low-pressure verticnl oylinder, workins two rranks at right angles. Cliiss B.— Coniponrid euKiiicswilh nni' liicli :iiid one low-iiressnvo vertical cylinder, workinp one criink, cylinders in line (tandem). Class C. -Compound eiigiius with two liicli and two low-pressure veitical cvlinders, wo? kin a two cranks at right angles, cjlindcrs In line (tandem). Class I). — Conijiound engines with one hi;;h and twolow-presaure vertical cylinders, working three cranks at 120°. * Always working with Early out-ott"; eniiiiies never pressed ; Welsh coaL f These fotir ships are very limited in boiler power. H. Ex. 48 To face page 76. \, I'llil h'UMl ( I HI 1 I'l'v 'III •, , 1 1 111! II 111 I II) \f''"'m " ', , ',:VK-r-\-W:X\:«V' ^i, 1 MWr '■<< "ii>'>