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Mr. Charles F. Scott. This connection is shown in Fig. 16. In this diagram, T, and T2 are two transformers, the primaries of which have the same number of turns and are connected to the two phases of the two-phase circuit. The secondary of T, has only .866 times the turns of the secondary of T2. By connecting one end of the secondary of Tt to the middle of the secondary of T2, as shown, three-phase currents of equal pressures on each phase are obtained from these secondaries.
The best known example of this is the system at Niagara Falls, N. Y., where 25-cycle two-phase currents, generated at 2,200 volts, are transformed to three-phase currents at 22.000 volts, at which pressure the energy is transmitted to Tonawanda and to Buffalo, the latter
Function of the Storage Battery
While these important developments in cross-country transmission were under way, the engineers of the urban stations also had new problems to solve. The convenience and other desirable features of the use of electric light and power were now being widely appreciated, especially when the cost of the lamps was reduced, and electric motors also were being used more liberally, in sizes from one-fourth horse-power to 300 H. P. and larger. This meant a big increase in the load on the station, as well as in the size of the district to be served. How to meet this increase economically, required an intelligent study of the problems of current distribution. As already noted, the distance over which it is economical to transmit current at a low volt
to the regular load, can be sent over these feeders, and if this current can be stored in some way in a location within but near to the economical limit, so that it can be used at the period of heavy load, this storage substation will in turn become a point of distribution from which current can be sent out as far again as the economical limit. Here is where the storage battery filled the want. In 1894 we find storage-battery substations installed in Boston and New York, and soon thereafter companies in other cities adopted them. In Boston a number of battery substations were installed in the nearer outlying districts, all of them being connected with one another and with the steam station. The batteries are charged during the hours of light load by means of boosters, which form part of the substation equipment. Their usefulness, however, is not by any means limited to outlying districts. As an auxiliary to a generating station, it is considered good practice from the standpoint of economy to install a storage battery if the peak of the load does not exceed two and one-half hours. As a safeguard against interruption of service, and as a help in maintaining a uniform pressure on the system, they have been found almost invaluable.
(To be Concluded)
Mechanical Appliances in Modern
Modern Devices that are Working a Revolution in the Shipbuilding Industry
By WALDON FAWCETT
IN THE COURSE of his testimony at the recent Congressional hearing relative to the condition of American shipping and shipbuilding, Mr. Cramp, probably the best known shipbuilder in the United States, made the statement that in this industry the advantage conferred by the superiority of the American workman is a thing of the
past. His explanation of this surprising statement was, that in this age speed and economy in shipbuilding are secured largely by the employment of the wonderful time-saving and labor-saving machinery introduced during the past few years, and that these products of Yankee ingenuity are being installed in foreign shipyards just as rapidly as the manufacturers can turn them out. Since these highly perfected automatic machines can be operated by any workman of average intelligence—by the poorly paid labor of Europe quite as well as by the highpriced American artisan—-it is claimed that vessel construction all over the world will ere long be on one basis.
Steam and Electric Cranes
Of all the classes of mechanical appliances which are serving as factors in inducing the new status of steel shipbuilding, unquestionably the most important
the shipyard, is placed a high trestle upon a track, on top of which is mounted one of the cranes. The horizontal boom of the crane is high enough above the shipways to pass over the highest point of the ships being built, while the arms of the cantilever project over the full width of the ship on each side of the trestle. The cantilever of the crane is equipped with a trolley and hoist block, whereby the load can be hoisted from the ground and traversed from one end of the cantilever to the other. Thus, inasmuch as the crane travels up and down the trestle, the en
is that made up of the various kinds of cranes. Chief among these are the steam and electrically operated balanced cantilever cranes—one of the American inventions which has of late been most extensively adopted in the shipyards of the Old World. These giant burdenbearers, unquestionably the most perfect machines yet devised for handling material about ships in course of construction, embody new features in crane construction which allow the long spans and high speeds for.which they are designed and equipped.
All the cranes of this type in use either in the United States or abroad are the invention of Mr. Alexander Brown, the well-known engineer, and all have the same plan of operation. Between each pair of shipways or building berths in
tire length and width of the two ships are covered, and materials may be handled and delivered to any part of the ships under construction. The trolley will attain any speed desired on the tramway, while the crane is capable of traveling along the track at a speed of 750 feet per minute. ,
One pair of engines, or an electric motor controlled by a single operator; drives all functions of one of these large cranes. The engines or motor and the machinery are located in the pier, and there is no dead weight carried either on the bridge or on the trolley. This allows the lightest form of bridge construction and very quick movement of trolley, and, especially, allows the trolley to be started, run at full speed, or stopped instantly. The cantilever cranes are equipped with
Great Floating Derrick "atlas," At The Champ Shu'vard, Philadelphia, Pa.
at. all times automatically keeps a similar position on the opposite arm.
Probably the best exemplification of the possibilities of these adjuncts of twentieth century shipbuilding is afforded at the Cramp plant at Philadelphia, where there are several of these cranes, all driven by electricity. F.ach crane is mounted on a steel trestle of special design and construction, about 600 feet long, and of sufficient height to bring the under side of the crane-girder 105 feet above the ground. One of these cranes, which may be considered as representative of its class, is 102 feet long from end to end of girders, with 190 feet effective travel of trolley. It will lift 30.000 pounds at 60 feet either side of the center, and 9.000 pounds at either end of bridge. A single electric motor operates all functions of the crane at the following speeds:
Hoisting a full load of 30,000 pounds—125 feet per minute.
Trolley across cantilever—400 to 800 feet per minute.
Entire crane along trestle, on track of 20foot gauge—400 to 700 feet per minute, depending on load and wind-pressure. The minimum of 400 feet is with full load and against a wind pressure of ,30 miles per hour.
Recently this crane placed in position on shipboard, a battleship sternpost weighing eighteen tons, and, with the assistance of but a few men, conveyed it from the cars at the opposite end of the yard, an operation never accomplished under the old plan in less than two or three days nor without a large force of workmen engaged.
Ranking with the cantilever cranes for marvelous achievement are the monster derricks to be found at several American shipyards. The best example is afforded by the "Atlas" at the Cramp yard—the largest and most powerful floating derrick in the world. The pontoon of the structure is 73 feet in length, 62 feet in width, and 13 feet deep. When carrying the maximum load of 125 tons at the boom end, and with water ballast aft sufficient to bring her to an even keel, the "Atlas" has a freeboard of 16 inches and a displacement of 1,563 tons. The cone has a diameter of 40 feet at the base; the length of boom from the axis is 58'/. feet; and the boom swings 36 feet clear of the pontoon. The height from deck to masthead is 116 feet; and from deck to boom, 65 feet. The maximum hoisting height is 50 feet. The pontoon is of iron, while the boom, mast,