COMPARATIVE VIEW OF HIGH-POWER TORPEDO-BOAT-DESTROYER ENGINES AND RECIPROCATING ENGINES OF SAME CAPACITY. HE modern auto-boat is an excellent example of a light craft equipped with the lightest type of engines, with the greatest relative output for highspeed service. The racing automobile boat consists essentially of a light yet strong hull built on racing lines, equipped with high-power engines which practically occupy the whole of the boat except the necessary space for the op erator. The torpedo-boat is another craft of similar construction, consisting of a steel shell, with tremendously high-power, high-speed engines, and with boilers of large capacity, yet of light weight, the whole occupying most of the space in the torpedo-boat, only sufficient room being provided for the small crew, the torpedoes, and the launching equipment for the same. The accompanying illustration shows the comparative size of these powerful, yet miniature engines for torpedo-boatdestroyer service, as compared with large multi-cylinder engines of the same capacity for an ocean liner, as erected at the Krupp shops at Kiel, Germany. These engines have each a capacity of 3,000 horse-power, those of the torpedoboat destroyers being at the right in the foreground. These small but powerful engines have a stroke of 19.68 inches, and are operated at a steam pressure of 17 atmospheres. It is interesting to note that the larger engines of the same capacity, 3,000 horse-power, built for a large freight and passenger steamer of the HamburgAmerican Line, have a piston stroke of 53.93 inches, the steam pressure being 15 atmospheres. For the high-speed torpedo-boat-destroyer service, the greatest engine power for the least space occupied, and the lowest weight possible for horse-power, THE NOBLE NATURE are absolutely necessary, the same conditions being required as for the racing types of automobile boats. In order to have a light engine of high power for torpedo-boat-destroyer work, these engines were built for a speed of 350 revolutions per minute, while those of the large steamer operate at a speed of only 80 revolutions per minute, which has a great effect upon the comparative size of the engine equipment. The large steamer will have a displacement of 13,700 tons, while the torpedo-boats above described have a displacement of only 420 tons. The engines shown in the background in the accompanying illustration for the ocean steamer, are 22.8 feet high, and occupy a floor space of 13.3 feet by 30.5 feet; while the space occupied by the torpedo-boat engines is only a fraction of the above, being 8.6 feet by 5.2 feet by 13 feet. The weight of the former engines is 231 tons, and they require 42 railway cars of 5 tons' capacity each to transport the same, while the torpedoboat engines weigh only 18 tons, only four such cars being required to carry them to the place of installation. The relative dimensions of these small marine engines for the torpedo-boat destroyers, and those for the ocean liner, can best be understood when it is stated that the former weigh only 11.9 pounds per horsepower developed, while the latter have a weight of 154.3 pounds per horse-power of capacity. The shafts of the torpedoboat engines are 6.93 inches in diameter, while the shafts of the larger engines are 14.8 inches in diameter. The details of construction of these high-power engines for torpedo-boat service and freight and passenger service, are of particular interest to the builder of motor-boats, as showing nearly the limit of steam engine construction as to light weight, high power, and small space required by the former, while possibly giving some clew to the methods which may be employed in reducing the weight of motors in auto-boat construction. At the present time, the gas engine has made it possible to attain very high speeds with very small and light boats, on account of the entire absence of the steam boilers and the compact construction possible with internal-combustion motors. It would seem as though the limit had been reached, even in this line of high-speed construction; although the steam turbine. shows possibilities of reducing the engine space for ocean liners and steamdriven torpedo-boats, while the gas turbine may ultimately show similar possibilities for the high-speed auto-boat, Are you worried by any question in Engineering or the Mechanic Arts? Put the question into writing and mail it to the Consulting Department, TECHNICAL WORLD MAGAZINE We have made arrangements to have all such questions answered by a staff of consulting engineers and other experts whose services have been specially enlisted for that purpose. If the question asked is of general interest, the answer will be published in the magazine. If of only personal interest, the answer will be sent by mail, provided a stamped and addressed envelope is enclosed with the question. Requests for information as to where desired articles can be purchased, will also be cheerfully answered. Making a Wrench Can you suggest a handy wrench for use on carriage or buggy?-A. H. R. What is known as the "S" wrench is a standard shape which is probably the best for all-around purposes. If you cannot buy one in your local hardware store, a blacksmith can easily turn one out. It is made as follows: Round the ends of a piece of buggy spring or steel tire of suitable length. About one inch from each end bend the piece of steel and fold over, as the drawing indicates. Punch a hole in each end, and cut out to each end, as shown by the dotted lines. These openings serve as the slots with which to grip the nuts. They may now be made the size re (ল HANDY S-SHAPED WRENCH. Take equal parts of white rosin and shellac, and melt them together. When this has been done, add a quantity of carbolic acid (in crystals) equal to the quantity of rosin or shellac used. The cement thus made has great adhesive power. Constructing Stairways Is there a way of laying boards in stairbuilding to minimize the wear?-H. H. The boards for steps are usually laid transversely-i. e., at right angles with the direction of travel up and down the stairway. The result is, the wear WAY TO LAY STAIRS. comes across the grain. The boards for steps should be placed as shown in the drawing. The grain will thus run in the direction of the traffic, and the length of service of the material employed will be greatly prolonged. Only narrow boards, threaded into each other, as indicated, should be used. Oak or maple makes the best material for the purpose. Process of Pack Hardening Will you describe the process of pack hardening?-F. M. P. is covered with fire-clay, to prevent the gases from escaping, and the box is closed and heat applied. This method is most valuable in hardening milling-machine cutters, gauges, and taps where it is essential that the diameter and pitch remain unaltered. For the sake of economy, a number of pieces should be packed together. The pieces are wired with iron binding wire of sufficient strength to sustain the weight when the wire is red hot. One end of the wire is allowed to project over the edge of the box and is covered with clay. Test wires are inserted through holes in the cover of the box, as in annealing. The time the material is allowed in the fire is determined by the diameter of the tools in the box and by the nature of the work. For tools 1⁄2 inch in diameter, burning should continue from 1 to 11⁄2 hours after the wires are red hot; for pieces 2 to 3 inches in diameter, 21⁄2 to 4 hours. On removing from the box, the tool should be immersed in raw linseed oil, and worked about in this liquid until the glow is gone. If the piece of steel thus being hardened is more than an inch in diameter, it should be reheated on removing from the bath, to a temperature of 212°, to prevent its cracking. Making a Shaving Horse I should like to make a shaving horse. Could you give me a brief description of how to do so, with some simple drawing?-T. H. W. Take some good two-inch plank of convenient length; and construct a bench some 18 inches high, supported by stout legs set at a slight angle, as indicated in the diagram. In constructing the bench, allowance should be made for the slant The article to be hardened is packed ing platform b, which will overlap the in an iron box with carbonaceous material. This carbonaceous material is charred leather, ground very fine, being reduced to pieces each half as large as a pea, and mixed with an equal volume of wood charcoal. The iron box, which should be large enough to allow ample room for the piece to be hardened, is covered on the bottom an inch deep with this packing material. Next the metal is laid on this, and the box nearly filled with more packing material, which is tamped down. Lastly, the space remaining end of the bench. The clamp a should be made of tough hardwood that will not split. The shank or support ƒ is an ex SHAVING HORSE. |