During the last few years the new cars have been made considerably larger and hence the propulsion equipment has become proportion ately more powerful than that formerly pro vided. The latest motors are specified to per form any service, on cars weighing 75 tons loaded, that is now being performed by the motors on the original 58-ton cars and it is required also that they shall operate satisfac tonly on trains tnade up indiscriminately of the old and new types of cars. These motors are provided with tapped field commutating poles and self-ventilation. They operate nor mally at 600 volts direct current but are capable of successful operation at voltage up to 750. Space restrictions have had a marked mfluence on the design, owing to the use of clasp brakes and the desire to utilize standard electncal con struction and to this end the gear face has beets reduced to four and one-half inches in place of the five-inch face that would ordinarily have been used. Acceleration is accomplished either automatically or by hand, the former being under control of the current-limit relay on eac.h car and there are 10 notches for forward rtm ning and six for .reverse, these including the running positions made available by the field control as well as the customary intermediate running points.
In some of the single-phase locomotives of recent construction spur gears and coupling rods have been adopted for transmitting the power from the motor to the driving axles. Each truck is provided with two motors geared to a common intermediate shaft which is connected to the driving wheels by means of the coupling rods. The latter are arranged one on each side of the locomotive with an angular displacement of 90 degrees. The pinions on the motor shaft are fitted with springs to give circumferential flexibility. This arrangement is adopted to equalize the tooth pressures on the two pinions and to compensate for the sudden alterations of tongue chiefly due to the coupling rod drive with its changing reciprocating forces. Two strongly constructed centre pins supported from the trucics take the weight of the locomotive body and the electrical equipment. The control switches with their operating apparatus are mounted together with the transformer so that the whole forms a complete unit which can be installed or removed bodily through an opening in the roof. The rivo motors of each pair are connected in series, while the two pairs are in parallel with one another.
Electric locomotives are now generally con sidered in two groups, regardless of system of current supply, namely, the powerful machines which are used in heavy electrifications on the main lines of important steam roads and the lighter locomotives which find their field of application in less conspicuous duty in the elec trified zones of steam roads and in handling freight cars on interurban lines. The former
locomotives are of special designs, each rail road syStem having its own requirements. The design of the lighter machines tends more to standardization. Standard interurban freight locomotives Are usually- of the steeple type which is preferable to the box type in ap pearance and i4 free from cornpressor noise.
Design features introduced to ensure reliability and low maintenance cost include particularly (1) Form-wound armature coils, with special insulation in the ends of the slots; (2) Strap wound field coils securely fastened and held against vibration; (3) Substantial brush-holder design and construction; (4) Mica insulated, undercut commutations; (5) Bearings of ample size with oil-gauging pockets, lubricated by oil drawn up and filtered through waste; (6) Two-point gear case suspension. The unit switch control has proved itself capable of handling the heavy currents encountered and also to withstand the bumps to which the loco motives are subjected, particularly in switching work, low-speed, drag-freight service or main line service. In this control the various main circuit connections are made by unit switches, actuated by compressed air taken from the air brake system; the admission of air to the switch cylinders being controlled by magnet valves, which valves are operated by current from a control circuit through a train line from the master controller. Current from this control circuit is tapped from points on the control resister which is connected between trolley and ground, or may be supplied by a storage battery.
In late years the solution of the electric railway problems has become more difficult. The automobile has become a most serious com petitor; at this time more than 6,000,000 pleasure cars are licensed. The automobile has not only decreased riding upon the trolley cars during business hours, but it has deprived the railway of practically all of its pleasure riding. The entire economic basis of the industry has been undermined and if the business is to survive it must be a radically different business in the future than it is at the present time It must, in the first place, secure prompt and adequate relief by a sufficient increase in revenues to enable it to function as a public utility; for a rejuvenation of credit is essential to carrying through the radical readjustment in operating methods which will be necessary. In many of the smaller cities, the companies must turn to one-man cars, permitting more frequent service with reduced operating cost. In the larger cities the companies and the public must face the necessity of abandoning the theory of a flat five-cent fare covering the entire city area and of charging the passenger according to the dis tance which he rides. See AMERICAN STREET