The Birmingham age-herald., 1908-07-13
MYSTERIOUS FORCE
 THAT DRIVES CARS
Few People U1 der stand Com
 pIicated Mechanism
A SIMPLE EXPLANATION
Detail Description i1 Plain Language of How the Electric Current From the Power House
 PropeIs Cars.

Few Of all the millions of people who ride annually on the electric cars un- derstand the mysterious force which drives them so rapidlyIup and down the tracks. With slight turn of the con- troller handle the mdorman stops the big car on the cornei in obedience to your signal, and no sooner are you aboard than the car sides rapidly for ward and speeds alont the track to be as quickly stopped anl started further ! down the street.
 To the superstitioui foreigners the electric cars are very mystifying, and be it known, it is very puzzling to any one, not an electrical engineer, to tell just how the electric c3rs are propelled. It was only twenty yeas ago last Feb ruary that Frank Spraaue ran the first electric car the world ever saw at Rich mond, Va, and since that time they have been improved until they the perfect convenience so common and well patronized today. For twenty years the electric cars have been running and al- though millions and millions of people have ridden on them time and again but very lew nave ever ldAru lut liOuDlc tO , ascertain how, or why, they move.
 In simple language tlis is the expla- nation: Electric cars depend upon electricity for energy. This electriity is generared in a power-house eith,r by developed water-power or by stelm engines Be- cause of the simplicity of construction alternating current generators are gener- ally used: but alternating current is sell fr, rlrIx hto fact makes it necessary to change the alternating current which surges back and forth over the linei, to direct cur rent, which flows always one way. This change is effected with Dtary converters The converter looks lille a generator, but in reality 1t only changes the nature of the current with a very trif1ing loss in efficiency. This dired current elec- tricity is fed to the trdey wire at a pressure of about $50 volts. The trolley wire is familiar to all as heavy copper wire suspended over the racks from in- sulated guy wires. In a few instances, especially in New York, London, Chica- go and other large cities the wire car rying the current Is laid under ground and the trolley contact Is under the car or for heavy work the "third-rall' is used and the current collected from a rail by a sliding shoe.
 Purpose of Current.
 In every case where electricity is used for power purposes the current has to be "grounded for teturn pr q return wire used so as to complete the circuit w.th the power-hnuse. In the case CT electric railways the rails are either welded or bonded together with strips of copper and used for this return cir cult.
 When a car is TO be sln on railway line the trolley E released until the Il tie brass wheel presses against ths trolley wire. The wide fla 1SeS of this wheel keep it from running off and a heavy spring keeps 1t right against the wire. The electricity, which is to drive the motors located under the car, passes through the brass wheel and dowl the metal trolley rod to insulated cables con- cealed in the roof of the car. These ca bles lead to circuit breaker" in the roof of the vestibule, The duty of tie "circuit breaker is to "break or smut off the current when the load gets too heavy for the motors, because an over loaded motor would destroy itself by burning out in an effort to carry more than it's capacity. The circuit breaker which is a very simple contrivance, takes inc place of the old-time "fuse,' so prone to "blow out at the most inoppor- tune moments From the circuit breaker the current Is carried to the controller, w.ich is an upright, oval ron box in each end of the car. It may pc stated here that the equipment IS the same on either end of the car so 1t can be run either way without turning around.
 The Controller
 The controller is worked by two ad- unstable handles, the smaller Of whlch IS used only to reverse the motors. With the larger handle the contact points inside the device are opened and closed to 1n- crease or decrease the speed and pulling mower of the motors. Corresponding to the movements of the handle the current passes from the contact points to s9 ries of resistance grids located under the car. These cast-iron grids resist the cur rent or hold 1t back. When the controller handle Is moved up a notch one of these grids Is cut out and the resistance is re- tint ed, increasing the electricity which EGGS to the motors. As the harote 's moved frrn point to point the resistance Is lowered until tho full power of the line Is being foS to the motors and the car IS running top speed.
 Direct e,l.ent motors ale used because of the great starting torque which can be secured A street gar has to st,o anu start luiex'y and under full load. A di- rect current motor will quickly pick up its full load, whereas the alternating cur rent motor is not so ready to rapidly as- sume It's load. The motors on an ordi- nary car are from 25 to 100 horsepower and on the largest cars four motors are used The current passes through these motors to the car wheels and returns to the power-house by way of the bonded rails.
 The electric motors are geared to the but slightly from any other form of direct current motors. In the past few years the General Electric comrany has been experimenting very successfully with al- ternating current motors for driving cars, and the electric line of the Toledo and Chicago Interurban Railway company was one of the first in the country to be equipped with the new apparatus. By an ingenious arrangement to divide the fields of the alternating current motors the cars can be started just as easily as with d- rect current motors. This is of considera- ble importance because of the saving in motor construction, as the same motors can be used for direct or alternating current.
 Besides the electricity which drives the car, enough current is taken from the trolley to light and heat the int io. Car equipments are of very simple lesign and strongly constructed. The large intorur- ban and local cars are also equipped with air brakes. In some instances the l air is stored in large tank which has to be replenished from a central station, but l