The Electric Railway - 3

The Electric Railway - 3

 On May 13th of the year named this interesting road went into operation as the result of

hard and hurried work of preparation during the spring months. The first track was about

a third of a mile in length, starting from the shops, following a country road, passing

around a hill at the rear and curving home, in the general form of the letter "U." The rails

were very light. Charles T. Hughes, who went with Edison in 1879, and was in charge of

much of the work, states that they were "second" street-car rails, insulated with tar canvas

paper and things of that sort-- "asphalt." They were spiked down on ordinary sleepers laid

upon the natural grade, and the gauge was about three feet six inches. At one point the

grade dropped some sixty feet in a distance of three hundred, and the curves were of

recklessly short radius. The dynamos supplying current to the road were originally two of

the standard size "Z" machines then being made at the laboratory, popularly known

throughout the Edison ranks as "Longwaisted Mary Anns," and the circuits from these

were carried out to the rails by underground conductors. They were not large--about

twelve horse-power each--generating seventy-five amperes of current at one hundred and

ten volts, so that not quite twenty-five horse-power of electrical energy was available for

propulsion.

The locomotive built while the roadbed was getting ready was a four-wheeled iron truck,

an ordinary flat dump-car about six feet long and four feet wide, upon which was

mounted a "Z" dynamo used as a motor, so that it had a capacity of about twelve

horsepower. This machine was laid on its side, with the armature end coming out at the

front of the locomotive, and the motive power was applied to the driving-axle by a

cumbersome series of friction pulleys. Each wheel of the locomotive had a metal rim and

a centre web of wood or papier-mache, and the current picked up by one set of wheels

was carried through contact brushes and a brass hub to the motor; the circuit back to the

track, or other rail, being closed through the other wheels in a similar manner. The motor

had its field-magnet circuit in permanent connection as a shunt across the rails, protected

by a crude bare copper-wire safety-catch. A switch in the armature circuit enabled the

motorman to reverse the direction of travel by reversing the current flow through the

armature coils.

Things went fairly well for a time on that memorable Thursday afternoon, when all the

laboratory force made high holiday and scrambled for foothold on the locomotive for a

trip; but the friction gearing was not equal to the sudden strain put upon it during one run

and went to pieces. Some years later, also, Daft again tried friction gear in his historical

experiments on the Manhattan Elevated road, but the results were attended with no

greater success. The next resort of Edison was to belts, the armature shafting belted to a

countershaft on the locomotive frame, and the countershaft belted to a pulley on the caraxle.

The lever which threw the former friction gear into adjustment was made to operate

an idler pulley for tightening the axle-belt. When the motor was started, the armature was

brought up to full revolution and then the belt was tightened on the car- axle, compelling

motion of the locomotive. But the belts were liable to slip a great deal in the process, and

the chafing of the belts charred them badly. If that did not happen, and if the belt was

made taut suddenly, the armature burned out--which it did with disconcerting frequency.

The next step was to use a number of resistance-boxes in series with the armature, so that

the locomotive could start with those in circuit, and then the motorman could bring it up

to speed gradually by cutting one box out after the other. To stop the locomotive, the

armature circuit was opened by the main switch, stopping the flow of current, and then

brakes were applied by long levers. Matters generally and the motors in particular went

much better, even if the locomotive was so freely festooned with resistance-boxes all of

perceptible weight and occupying much of the limited space. These details show forcibly

and typically the painful steps of advance that every inventor in this new field had to

make in the effort to reach not alone commercial practicability, but mechanical

feasibility. It was all empirical enough; but that was the only way open even to the

highest talent.

Smugglers landing laces and silks have been known to wind them around their bodies, as

being less ostentatious than carrying them in a trunk. Edison thought his resistance-boxes

an equally superfluous display, and therefore ingeniously wound some copper resistance

wire around one of the legs of the motor field magnet, where it was out of the way,

served as a useful extra field coil in starting up the motor, and dismissed most of the

boxes back to the laboratory;