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IN THE ENGINE ROOM. TESTING STEEL FOR MARINE ENGINE CONSTRUCTION. At the French government engine works at Indret the steel used is classified under three heads, namely, (1) semi-hard (32 to 35 tons tensile strength with 20 per cent elongation) in the forms of hammered blooms and hexagonal bars; (2) castings to pattern; (3) soft (25 to 29 tons tensile with 23 per cent elongation), and extra soft (21.6 to 25.4 tons tensile with 25 per ceut elongation), alsoin bloomsand bars. The tensile tests are made with the Thomasset testing machine, in which the stress is continuously indicated by a mercury column, while the changes in the test-piece are recorded graphically by a registering apparatus designed by Richard Brothers, the latter addition being especially useful in fixing the elas- tic limit—a factor which, for constructive purposes, is of greater value than the ultimate strength. The toughness, or resistance to fracture by impact, is in the harder qualities tested by the falling-weight method, on what is known as the Ruelle machine, where the test-piece—200 millimeters long and 30 millimeters square—laid upon knife-edges 160 millimeters apart and projecting 50 millimeters from the anvil, is subjected to the blow of a falling weight of 18 kilos., with a rounded end striking midway between the points of support. The minimum weight of the anvil is 350 kilos., the height of a fall and other conditions varying with the class of material. For blooms the whole number, and for bars one-half of the test-pieces must not break before the fifteenth blow, when the fall is 2.75 metres; while for unforged castings with test-pieces of the same size the initial fall is 1 metre, which is increased progressively by increments of 5 centimetres to a maximum of 1.5 metre, the half limit of resistance being applied as in the case of bars. Soft steel is tested for toughness by the forge test of doubling under the hammer when water-hardened. The author considers these tests, especially the last, to be es- sentially unsatisfactory, as so much depends upon the degree of heat employed. Ifthe metal is too cold the hardening effect of the water is nil; while if the proper heat (about 9,000) is used, the structure is so much changed that the test may be satisfied even by steel originally of bad quality. It is therefore proposed to modify the falling-weight test, that it may serve both for breaking and bending uses. In this method the test- piece—20 millimetres square—is clamped in a holder with an overhanging length of 100 millimetres, which receives the blow of the tup on its outer end. The bar is nicked on all four sides in the plane of the outer face of the holder, and when so weakened it can be broken by a single blow of the weight falling from a height varying with the quality of the metal, and which is called the height of rupture. If, however, the section is not weakened by grooving, the overhanging part is merely bent by the blow, and the angle of deflection produced is taken as a measure of the rigidity of the metal. This angle may be from 140° to 160°. The author considers that steel in the ‘‘natural” state is sensibly brittle, whatever may be the amount of car- bon contained, and that a soft or extra soft metal giving 25 per cent elongation is not sensibly safer against breaking than the stronger but less ductile kinds of 30 tons to 38 tons tensile strength, and that the latter should be preferred for moving parts, subject to wear from friction, such as piston rods, guide blocks, slide- valve faces, etc., as many accidents to engines on ser- vice have arisen from the use of piston rods made of steel of too soft aquality. In all cases the metal must be subjected to the process of double-tempering, i. e., a a first tempering from a bright cherry red, to effect the transformation of the grain, followed by a second from a dull red, which is more properly annealing, for bring- ing down the hardness to the required degree, and re- moving strains producing brittleness. The effect of this process in modifying the fragility and elastic limit in forged steels of the two classes is shown in the follow- ing results, obtained by tempering the test-pieces in water at about 170° F.: Sort. SemMi-HARp. Natural.|/Tempered.} Natural.|Tem. Elastic limit, tons............... 12.0 20 160 26.7 Height of rupture, metres ...... 0.2 2.0 02 1.8 143 168. -}) 161 158 Angie of bend degree THE MarRINE RECORD. In a second series of experiments the bloom was fre- duced under the hammer to two-thirds of the original section, with the result of rendering it more homeoge- neous, which without altering the ultimate strength and elastic limit has a very marked influence on the elongation, and more particularly upon the contraction, which not only becomes larger, but also more regular, being for semi-hard steel when Forged, Natural. Non-tempered—elongation 24—25 per cent, instead of 183—16 per cent Tempered—elongation 17—18 per cent, instead of 7—11 per cent Non-tempered—contraction 70—80 per cent, instead of 14—24 per cent Tempered—contraction 141—163 per cent, instead of 22—70 per cent The method of double-tempering is now applied at Indret to all forgings for engine work, and with the ex- ception of the larger engine framings, to most of the castings. A further advantage in its use for these is that there is greater certaidty in detecting unsound cast- ings. The tempering plant is capable of handling objects not exceeding 6 metres in length. Screw-shafts | are received forged and tempered at the makers’ works (Creusot and Saint Chamond) subject to the following conditions: The shafts of steel, either tempered and annealed or double-tempered, must satisfy the following tests: Two sets each of five test pieces to be taken from slabs cut out of a waste piece of the full size of the shaft and par- allel to its length, those for tensile and elastic limits being 100 millimetres long by 13.8 millimetres square, and those for impact 20 millimetres square and not less than 180 millimetres long. These are to be cut to shape cold, and if any of them are unsound others may be cut from the same slabs; but should these be defective the article may be rejected. ‘Three out of five pieces are to be tested for elastic limits, and incidentally for tensile strength and elongation; but these latter tests are not material. Should the elastic limit of any one be below 28 kilos. per millimetre, or that of the mean of the three below 30 kilos., the other two shall be tested, when after rejecting the lowest of the five, the average of the four must not be below 30 kilos. or any one below 28 kilos. For the impact test the bars are to be scored on all four sides, at a distance of 100 millimetres from one end, by acutter of the form of an equilateral triangle of 1 millimetre in the side, made very exactly to gage. When clamped in the holder by a length not less than 80 millimetres, the piece must not break undera single blow of a weight of 18 kilos. falling 3 metres. Should any one of the three pieces fail, the test is to be ex- tended to the remaining two. Any article not satisfying the tests specified above, may, after retempering or annealing, be subjected to a second trial. : These conditions, which are perfectly satisfactory to the manufacturers, are especially valuableas giving a precise idea of the practical value of the material and have also led to aconsiderable reduction in the number of test pieces required in carrying on the current work of the establishment at Indret.—Institute C. HK. Foreign Abstracts. PROSTRATION AMONG NAVAL ENGINEERS. The alarming news received at Washington Aug. 13, by the Navy Department, telling of the physical collapse of Chief Engineer George K. ‘Tower and Passed Assist- ant Engineer Audrew McAllister, both of the battleship Indiana, gave rise in the minds of naval officers on duty here to the question whether in the care of our warships the danger line had not been crossed in the attempt of the overworked naval engineers to carry on the exacting duties required of them. The North Atlantic squadron has now had only eight days of grand maneuvers, aud during that short period the efficiency of the most pow- erful battleship of the fleet has been temporarily im- paired, two of the four naval engineers attached to the vessel having been condemned by medical survey and sent to the naval hospital for treatment. ‘‘Itis not sur- prising,’’ said a prominent official, “‘that this repeated tale of*the prostration of naval engineers is heard from our warships. Inthe British service there are one-half as many engineers as deck officers, while in. the Amer- ican navy there are only one-fourth as many engineers as there are officers of theline. The physical history of the Corps of Engineers,’ he continued, ‘‘during the past two years is a sad one, and it einphasizes the fact that not only must the number of engineers be increased, but their condition should be improved in order to ren- der the ships efficient tor the day of battle. The en- gineers are now working under an organization which was founded upon the necessities of wooden ships, but which is not adapted to vessels of steel.’’ COMPRESSED AIR DRY-DOCK. We illustrate this week a dry-dock, the invention August Geiger, éngineer, of Portland, Oregon, operated | by compressedair. The dry-dock is of the floating type, but unlike ordinary floating dry-docks, it has no bottom ‘so that the water can flow in and out with perfect free dom. This dry-dock has no pumping machinery; inits place an air compressor is used. The compressor is lo-— cated upon anelevated platform, running parallel with — the long sides of the dock, and is connected by pipes to the different water-tight compartments into which the © In order to lower the dock, valves — near the compressor are opened, air rushes out, and water flows in from underneath, causing the dock to sink. When the dock is to be raised, the compressor is started up, air is forced into the compartments, the — water is driven out and the dock rises to the surface. ~ dry-dock is divided. Suppose a vessel of 25 feet draft (about the greatest draft steamers have) was to be docked. It would be neces- sary to sink the dock about 28 feet, and in order to raise it air pressure of about 14 pounds to the square inch would be required. The higher the dock is raised, the less pressure is needed. Assuming a dock of 300 feet long, 80 feet wide, and 7 feet depth, we have a large box of 300 x 80 x 7 feet — 168,000 cubic feet. ‘This amount of compressed air is necessary when the dock is out of the water, but as the water displaced has only 7 feet depth, = 84 inches, the pressure required is only 84 inches di- vided by 28 = 3 pounds per square inch. As the lifting capacity of a dook is equal to the weight of displaced water, it would be in this case, if ina river, 168,000 cubic feet by 62 pounds, — 10,416,000 pounds, —5,208 tons, less — the weight of the dock itself. One great advantage of such a dock would be the bot- tomless construction, which in a dry-dock of 300 x 80 feet means a saving of 24,000 sq. ft. of water-tight floor- ing and calking, which isquite an item; and with this system a cheaper dock can be built than with the old- style pumping machinery. Another point in favor of this style of dry-dock is, that the lifting power acts under the upper side of the big box, which makes it steadier and less liable to topple over than with the or- dinary dry-dock, where the lifting power acts under the under side of the big box. Mr. Geiger thinks that com- pressed air could be more quickly furnished to raise the docks than it would be possible to pump water out by the old system. ‘The pipe connection would be smaller, and in general less machinery would be required. ae eee TELEGRAPHING TO VESSELS AT ANCHOR. The American consul at Copenhagen reports to the State Department that a young boatswain in the Danish navy has invented a telegraphic apparatus for commu- nication with a ship at a certain anchorage without the use of a direct line. An electric battery, with one pole in contact with mother earth and a telegraphic key and interrupter at the other, constitutes the Bland ap- paratus, from which cable is laid to and around the an- chorage in a coil from 1,000 to 1,200 feet diameter. A seneloid connected telephone aboard the ship completes the apparatus. The plan has worked successfully, and the young inventor is now at work to get rid of the telegraph key and make the communication wholly tele- phonic. Among the advantages of the new method is that sigfials in this manner will not, as in case of flags, be visible to an enemy, and that ships moving near the shore can communicate with various stations while passing over locations arranged for the purpose. eo a. We are just in receipt of first copies of a new Hydro- : graphic Office chart of the St. Mary’s River, covering the distance between Shifting Point, at the head of — Little Mud Lake, and the Turning Buoy, in Mud Lake proper, with a part of the Winter Point Range. The price of this chart is only 25c, although made from thi latest surveys. For sale at MARINE RECORD offices, Fourth Floor, Western Reserve Building. SG oh Ke SARIN RNY OORT es TREY F