Chapter XXV: Electric Cars, Boats, and Automobiles

=164. Electric Cars=, as well as boats, automobiles, etc., etc., are moved by the power that comes from electric motors, these receiving current from the dynamos placed at some "central station." We have already seen how the motor can do many kinds of work. By properly gearing it to the car wheels, motion can be given to them which will move the car.

Fig. 237 shows two dynamos which will be supposed to be at a power house and which send out a current to propel cars. From the figure it will be seen that the wires over the cars, called trolley-wires, are connected to the positive (+) terminals of the dynamos, and that the negative (-) terminals are connected to the tracks. In case a wire were allowed to join the trolley-wire and track, we should have a short circuit, and current would not only rush back to the dynamo without doing useful work, but it would probably injure the machines. When some of the current is allowed to pass through a car, motion is produced in the motors, as has been explained. As the number of cars increases, more current passes back to the dynamos, which must do more work to furnish such current.

_Trolley-poles_, fastened to the top of the cars and which end in grooved wheels, called _trolley-wheels_, are pressed by springs against the trolley-wires. The current passes down these through switches to _controllers_ at each end of the car, one set being used at a time.

=165. The Controllers=, as the name suggests, control the speed of the car by allowing more or less current to pass through the motors. The motors, resistance coils and controllers are so connected with each other that the amount of current used can be regulated.

When the motorman turns the handle of the controller to the first notch, the current passes through all of the resistance wires placed under the car, then through one motor after the other. The motors being joined in series by the proper connections at the controller, the greatest resistance is offered to the current and the car runs at the slowest speed at this first notch. As more resistance is cut out by turning the handle to other notches, the car increases its speed; but as the resistance wires become heated and the heat passes into the air, there is a loss of energy. It is not economical to run a car at such a speed that energy is wasted as heat. As soon as the resistance is all cut out, the current simply passes through the motors joined in series. This gives a fairly slow speed and one that is economical because all the current tends to produce motion.

By allowing the current to pass through the motors joined in parallel, that is, by allowing each to take a part of the current, the resistance is greatly reduced, and a higher speed attained. This is not instantly done, however, as too much strain would be put upon the motors. As soon as the next notch is reached, the motors are joined in parallel and the resistance also thrown in again. By turning the handle still more, resistance is gradually cut out, and the highest speed produced when the current passes only through the motors in parallel.

Fig. 238 represents a controller, by diagram, showing the relative positions of the controller cylinder, reversing and cut-out cylinders, arrangements for blowing out the short electric arcs formed, etc. A ratchet and pawl is provided, which indicates positively the running notches, at the same time permitting the cylinder to move with ease. Fig. 239 shows a top view of the controller.

=166. Overhead and Underground Systems.= When wires for furnishing current are placed over the tracks, as in Fig. 237, we have the overhead system. In cities the underground system is largely used. The location of the conducting wires beneath the surface of the street removes all danger to the public, and protects them from all interference, leaving the street free from poles and wires.

Fig. 240 shows a cross-section of an underground conduit. The rails, R R, are supported by cast-iron yokes, A, placed five feet apart, and thoroughly imbedded in concrete. The conduit has sewer connections every 100 feet. Conducting bars, C C, are placed on each side of the conduit, and these are divided into sections of about 500 feet. Insulators, D D, are placed every 15 feet. They are attached to, and directly under, the slot-rails, the stem passing through the conductor bar.

Figs. 240 and 241 show the plow E. The contact plates are carried on coiled springs to allow a free motion. Two guide-wheels, F F, are attached to the leg of the plow. The conducting wires are carried up through the leg of the plow.

=167. Appliances.= A large number of articles are needed in the construction of electric railroads. A few, only, can be shown that are used for the overhead system. Fig. 242 shows a pole insulator. Fig. 243 shows a feeder-wire insulator. Fig. 244 shows a line suspension. Fig. 245 shows a form of right-angle cross which allows the trolley-wheels of crossing lines to pass. Fig. 246 shows a switch. In winter a part of the current is allowed to pass through electric heaters placed under the seats of electric cars.

=168. Electric Boats= are run by the current from storage batteries which are usually placed under the seats. An electric motor large enough to run a small boat takes up very little room and is generally placed under the floor. This leaves the entire boat for the use of passengers. The motor is connected to the shaft that turns the screw. Fig. 247 shows one design.

=169. Electric Automobiles= represent the highest type of electrical and mechanical construction. The _running-gear_ is usually made of the best cold-drawn seamless steel tubing, to get the greatest strength from a given weight of material. The wheels are made in a variety of styles, but nearly all have ball bearings and pneumatic tires. In the lightest styles the wheels have wire spokes.

The _electric motors_, supported by the running-gear, are geared to the rear wheels. The motors are made as nearly dust-proof as possible.

_Storage batteries_ are put in a convenient place, depending upon the design of the carriage, and from these the motors receive the current. These can be charged from the ordinary 110-volt lighting circuits or from private dynamos. The proper plugs and attachments are usually furnished by the various makers for connecting the batteries with the street current, which is shut off when the batteries are full by an automatic switch.

_Controllers_ are used, as on electric cars, the lever for starting, stopping, etc., being usually placed on the left-hand side of the seat. The _steering_ is done by a lever that moves the front wheels. Strong brakes, and the ability to quickly reverse the motors, allow electric carriages to be stopped suddenly in case of accidents.

Electric automobiles are largely used in cities, or where the current can be easily had. The batteries must be re-charged after they have run the motors for a certain time which depends upon the speed and road, as well as upon the construction. Where carriages are to be run almost constantly, as is the case with those used for general passenger service in cities, duplicate batteries are necessary, so that one or two sets can be charged while another is in use. Fig. 248 shows one form of electric vehicle, the storage batteries being placed under and back of the seat.