Page:The New International Encyclopædia 1st ed. v. 06.djvu/887

* ELECTBIC RAILWAYS. 773 ELECTRIC RAILWAYS. divided into roadlH-d and track construction, and overliead c-onslruction. Only a few salient fea- tures of eacli can lie touclicd upon here. Street- railway tracks when once laid cannot be re- paired without takinj; uj) the pavement: and as this i.s an expensive operation, yreat care is taken in first putting down the tracks. Late practice for city work is to use standard oak ties 0X8 inches by 8 feet long, spaced about IS for every 30 feet of track. A trench is usually e.vcavated for each tie to a depth of from four inches to six inches below the bottom of the tie. The bottom of this trench is filled with broken stone and the tie laid upon this tilling. The rails are then laid and spiked to the ties, a girder rail nine inches •deep being commonly employed. These rails are usually either 30 or 00 feet long, and are con- nected structurally either by splice l)lates or cast joints, or by electric welding, and. electric- ally, where splice joints are used, by means of various forms of rail-bonds. Splice joints for electric railways resemble those of steam rail- ways, and consist of two splice plates for each joint, which are plac^ed on o])posite sides of the two abutting rails and clamped together by bolts passing through both splices and rails. The method of making cast welded joints is as fol- lows: The rails at the joint are cleaned and brightened by a sand-blast ( q.v. ) . and a cast- iron mold is placed around the rail-ends, making a tight fit. Into the mold the molten metal is poured. The metal in contact with the mold begins to cool and forms a crust, while the in- terior remains in a molten state. This crust con- tinues to cool and at the same time contracts, forcing the molten metal toward the centre of the joint. The top or bearing surface is after- wards filed off perfectly smooth, so that it is difficult to detect a joint by riding over it. Elec- tric welding of rail-joints is described in the article on Welding. The rails being laid and the jointing and bonding finished, the space be- tween the ties is ballasted and the pavement laid, restoring the street to its original condi- tion. For suburban and interurban roads, a track built of from 00-pound to 70-poiind Trails spiked directly to the ties is used, the ro<id sur- face being restored after all is completed. Overhead constniction for trolley roads com- prises the electric conductor and the structures for carrying the conductor. The supporting structure for the conductor is of two forms, ■usuall.v called span-wire and bracket-arm. In the first the trolley-wire is hung from a span- wire stretched between poles on opposite sides of the track; in the second, a single row of poles is used with a bracket-arm extending out over the track to carry the conductor. Often double-bracket poles placed between the tracks carry the two conductors for double-track roads. Both wood and iron poles are used. In America the development of overhead construction has been in the direction of securing lightness, strength, and elfectiveness at low cost, and ornamentation has not been sought. In Great Britain and Continental Europe, however, fanc.v brackets, scrolls, and ornamental castings have been used very generally, and this is the essen- tial difference between the practice on the two sides of the ocean. Car and c'cntral station con- struction are described in succeeding paragraphs. CoN'DnT Electric Railway.s. Conduit elec- tric railways are those having some form of conduit or trough below the level of the rails, cither between them or at the side of the track. I sually there is a short or continuous opening to the street, through which the 'plow' projects from the bottom or side of the car. Beside the conduit, supported upon suitable insulators, pins, CROSS-SECTIO.V OF CONDllT OF ELECTRIC IHIUV.W. SIIOWIN-Q THE METHOD OF SUPI'OKTING THE COSOCCTOR KAILS. or brackets, are generally the conductors, against which suitable rollers or rubbing blocks, forming part of the plow, are pressed. In this way cur- rent can be taken from one conductor up through the slot on a wire imbedded in the plow, through the motor, and again back to the other conductor. Various other kinds of conduit systems have been devised, but the one described is the only one which has reached any commercial success. The conduit electric railways of New York and Washington have the conduit between the rails; the only side-conduit railway of im- portance is that at Budapest, Hungary. As con- CaOSS-SECTIOX, SHOWISG FORM OF YOKE AND TRACK CON- STRCCTIOS. structed in America, a trench about 2 feet deep at the centre and 6 feet wide is dug along the line of the road, and hea-y cast-iron yokes, weighing from 400 to 500 pounds, are placed crosswise of this trench about everv 4 feet. To these yokes are bolted the tracks and the rails forming the edges of the slot. Between these yokes and around them is placed concrete, with a trough in the centre to form the conduit. Between and at the sides of the tracks at in- tervals of about 15 feet small covered openings are made into the conduit, and at these points heavy cast-iron and porcelain insulators are bolted to the slot-rails. These have pins pro- jecting down into the conduit, to which steel T-rails are bolted. The car-plows extend through the slot and have rubbing-blocks which press against the conductor rails. Current is sup- plied to these conductors by feeders or cables which run in underground conduits alongside the track from the power station, and are at tached at intervals to the conductor rails. Drainage is securc'd by frequent outlets from the conduits to sewers, and manholes at inter- vals give access to the conduit for repairs. Conduit railways are far more expensive to construct than overhead-trolley lines, chiefly because of the elaborate track and conduit con- struction required, and because of the necessity of removing underground pipes which interfere