An electric car, operating in a tube, which cannot collide with another car, which is run by electricity and yet contains no motor, and which may be derailed and practically wrecked without injury to the propelling member is in almost daily operation at an experimental plant in Paterson, New Jersey ca. 1913.
The car does not differ materially in the arrangement of trucks and wheels from many others that have been invented for the carrying of mail and package freight. Its main claim to distinction and originality lies in the fact that it is pulled along over its narrow gage track by magnetic force. There is no tractive effort whatever on the wheels, the car is carried along as by an invisible cable, the ball-bearing wheels eliminating a great amount of friction.
In the ordinary electric car, the electric current is changed into mechanical energy thru a motor geared to the wheels. This motor consists of a rotating armature and a set of stationary field coils, the armature being rotated by induced magnetism. The experimental car in New Jersey goes the ordinary car “one better” on the score of efficiency, and applied the same magnetic force that rotates the armature of the ordinary street car to pull the new car over a narrow gage track at a speed of from twenty-five to thirty-five miles an house.
Between the rails of this experimental road is fastened the stationary element of an induction motor. It is as if the fields of several hundred motors were prest flat and bolted end to end and fastened to the roadbed. On the bottom of the car and clearing the stationary element between the rails by only a fraction of an inch is a movable motor member corresponding to the armature of an induction motor. Power is supplied to this movable primary member by two live rails in constant contact with two trolleys on the car. The alternating current is thus applied to the movable member of the car. This induces a magnetic field and the car is propelled at a uniform rate of speed whether up grade or on a level.
In recent tests on the 1000-foot experimental tube at Paterson the car maintained the same speed whether empty, loaded with 1000 pounds, or carrying a trailer up a 20 per cent grade.
The system is of practical value, says the inventor, in carrying mail and express between railroad stations and express and post offices. It is intended as an improvement on the narrow limits of pneumatic tube service. Its advantages over many other types of cars are that the same amount of electric power will send a car farther and faster when applied as a pulling force than when the same power is applied thru motors and gearing, and that the smallness and lightness of the movable motor member gives the car increased carrying capacity. Furthermore, the cars are controlled from the powerhouse, a reversal of the current in the primary motor member at the control board serving to change the pull urging the car forward to a push which quickly brings it to rest.