Edison, His Life and Inventions [177]
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 car- axle. 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;
a few being retained under the seat for chance emergencies. Like the boxes, this coil was in series with the armature, and subject to plugging in and out at will by the motorman. Thus equipped, the locomotive was found quite satisfactory, and long did yeoman service. It was given three cars to pull, one an open awning-car with two park benches placed back to back; one a flat freight-car, and one box-car dubbed the "Pullman," with which Edison illustrated a system of electric braking. Although work had been begun so early in the year, and the road had been operating since May, it was not until July that Edison executed any application for patents on his
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 car- axle. 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;
a few being retained under the seat for chance emergencies. Like the boxes, this coil was in series with the armature, and subject to plugging in and out at will by the motorman. Thus equipped, the locomotive was found quite satisfactory, and long did yeoman service. It was given three cars to pull, one an open awning-car with two park benches placed back to back; one a flat freight-car, and one box-car dubbed the "Pullman," with which Edison illustrated a system of electric braking. Although work had been begun so early in the year, and the road had been operating since May, it was not until July that Edison executed any application for patents on his