The Thimison-Houston "Single-reduetion Gear" is shown in Fig. 15. It is very nearly iron-clad, having two pole pieces of ample surface and carrying two field coils, which part ially surround the armature core. The magnetic circuit is completed on the front end of the motor through the face plate, and at the bank through the frame on which are cast the axle boxes and arms that serve as a support for the armature-shaft bearings. The armature is of the Gramme ring type. and the bobbins arc wound close together around the entire rim. One great advantage of this con struction is the fact that any coil can be easily re wound without disturbing its fellows, while with the drum armature, in the type of motor formerly used by the company, the winding all had to be removed down to the injured coil. The motor when mounted on a truck with 30-inch wheels is de signed to clear the tops of the rails 4 in. The spur on the armature shaft is of steel, 4i in. face, and has 14 teeth. The split gear on the car axle is of cast-iron, with the same width of face, and has 67 teeth. The speed of the armature shaft rela tive to that of the car axle is nearly 4.8 to 1; when the ear is running 10 miles per hour the armature makes 538 revo lutions per minute, or the speed of the armature is 53•8 turns per minute when the oar speed is 1 mile per hour. The gears are sur rounded by an iron box, so that they may he run in oil.
The Westinghouse Sin gle-red-aetion Car _Motor, Fig 16, has the square form of frame, but the change in the shape of the magnetic circuit, which is circular, makes it possible to utilize four poles with great ad vantage. They are also rather narrow, and conse quently are capable of being magnetized by compara tively short and small wind ings. The gear ratio is 3-3 to 1. The ironclad form • - of the motor enables it to be completely shut in by applying side plates, so that in actual practice it is inclosed so tightly as to be quite free from the numerous difficulties so often experienced from dirt finding its way into the working parts of a machine. The normal speed of the armature at a car speed of about 10 miles per hour is 380 revolutions per minute.
Gearless single-redaction motor was followed by another type in which the ar mature is mounted directly upon the oar axle, thus doing away with all gearing whatsoever. The general appearance of the Westinghouse gearless motor is shown in Fig. 17. It is a 4-pole machine, completely iron-clad, and with the same hinged arrange ment of fields as in the other types of Westing house motor. The arma ture is built directly on the car axle, without any attempt at flexible con nection ; it is of the drum type, 16 in. in diameter, and instead of having a smooth surface, is grooved to receive the wires, thus holding them rigidly in place. The total depth of the field magnets over all is brit '20 in., giving 5 in. clearance between the bottom of the motor and the tread of the 30 in. wheel.
In the Short gearless motor the same style of armature is employed as in the ordinary Short motor—that is, a fiat Gramme ring of many sec tions, with a magnetic circuit arranged like that of the Brush dynamo. The motor and its connec tions are shown in section in Fig. 18. The arma ture itself is not mounted.as in the Westinghouse motor, directly upon the axle, but on a hollow shaft concentric with it, with plenty of inside clearance. The armature proper consists of a laminated iron core of the usual Short type, wound in a large number of independent seg ments. The commutator is mounted on the same hollow shaft as the armature, and close to it. The motor is really a 4-pole machine. The
field coils are bolted to a circular frame at each side of the motor, in the center of which are the bearings that carry the hollow armature shaft.
The spring connections for easy starting are shown in the cut, A double arm, running out from the frame work to the cross girders of the truck makes provision for supporting the entire motor. A 36-in. wheel is gen erally employed, giving a clearance of 5 in. over the track. At a speed of 10 miles per hour, the armature drives a 36-in. car wheel 94 revolu tions per minute ; the equivalent speed of a single redaction motor would be about 400.
Probably the first gearless motor for street cars was the Eickemeyer Field, the peculi arity of which is the use of a motor not connected to the axle, but operating through the medium of a eon necting-rod. driven direct from a crank on the armature shaft. The motor is iron-clad and singularly compact.
The method adopted is illustrated in Fig. 19. which shows the Field locomotive that ran for some time on the New York elevated railways.
The type of locomotive employed on the City and South London Railway, London, under ground, is shown in Fig. 20. Each locomotive is capable of develop ing 100 effective horse-power, and of running up to 25 miles per hour. The armatures of the locomotives are constructed so that the shaft of the armature is the axle of the locomotive ; in this way all inter mediate gear a11(1 all reciprocating parts are entirely avoided. A motor is fitted on each axle, as shown in the cut, the axles not being coupled, but working inde pendently. The current is con veyed front the collecting shoes, through an ammeter, to a regulat ing switch, then to a reversing switch, thence to the motors, tn1d back through the framework of the locomotive to the rails, so completing the electrical circuit, Underground ('onduelors.—Mr. S. D. Field has invented an electric street-railway sys tem, designed to avoid the use of overhead wires. Fig. 21 shows the general method of con struction, The wheels shown are :It) in. in diam eter, and the conduits themselves are only 8 in. high. They are built tip in lengths from two sections bolted together at the bottom, and let into the wooden cross-ties, leaving a slot at the top, It will be noted that the wheels have different treads on each side of the flange, the inner being of smaller diameter than the outer tread. On a straight track the outer, larger tread of each wheel bears on the track. But when rounding curves, the wheel bears on the sinti-ller tread on the inner rail, so that it has a slower motion than the outer wheel, and thus the friction usually encountered is avoided. The angle-rails. which are bolted to the tops of the conduits, are raised only one-fourth of an inch above the level of the pavement, and, being rounded, present no obstruction to ordinary traffic. The conductors are supported in the conduit by insulating hangers. An underground system based on this principle has been in operation in Budapest, Ilungary, since 1890. A number of attempts have been made to avoid the use of the slot in streets, and several systems hare been devised by means of a cable buried beneath the surface is connected to the car circuit by switches placed at intervals and operated by mechanism, such as attracting magnets on the car. _Among these systems are those devised by Pollak & Binswaliger. McElroy. Lineff, and others. They have not, however, come into general use.