The National Switch & Signal Company, of Easton, Pa. Has just completed, at Hammond, Ind., one of the largest interlocking plants in the United States. It was installed by the Chicago, Hammond & Western under the direction of the Signal Engineer, Mr. J. B. Cox, and is one of the most complicated interlockings thus far built. The general diagram, Fig. 1, shows the location of the tracks, switches and signals. These tracks are owned by the Chicago & Western Indiana; Chicago, Hammond & Western; Chicago & Calumet Terminal; Chicago & Erie; Chicago, Indianapolis & Louisville; Michigan Central; New York, Chicago & St. Louis; Pittsburgh, Ft. Wayne & Chicago (State Line & I. C.), and the Wabash roads. These with their tenant companies, the Chicago, Lake Shore & Eastern, and the Elgin, Joliet & Eastern, made a considerable variety of interests to be accommodated and satisfied in the design of the plant.
When the plan was first submitted to the signal company it was contemplated to put in only a portion of it at the present time; a full plan, however, was offered by the National Company, and it was expected that the installation would be carried out in such a manner as to make it possible to put in the additional work contemplated without much change in the arrangement of the connections. A complete plan was made by the signal company showing the location of every connection, crank and leadout, before any work was commenced on the ground, and this plan is partially illustrated by Fig. 2. But before the work was fairly under way several of the railroads found that their business required the introduction of some additional switches and so the plant was changed from time to time, complicating the work of the signal company and introducing elements which would tend to lead to errors in the locking unless every step was carefully scrutinized.
The machine was built at Easton on a foundation made of two channel beams, surfaced so as to present an accurate plane, and the locking was equally distributed on the front and the back of the machine. The machine is made to accommodate 224 levers, the total number now in service being 136, there being 20 levers in the machine not now in use.
In spite of all the various changes and the complex nature of the work, the machine was tested after the locking was in place and no errors were developed. This machine was exhibited to the members of the Railway Signal Club when they had their annual meeting in New York in September, at which time the members visited the works. The economy of space possible with vertical locking is forcibly illustrated in this machine. It requires no more width of cabin than if it had but one lever.
The signal cabin is substantially and elegantly finished. The foundation is of concrete, the walls are pressed brick and the roof of slate, the entire structure being fireproof. The machine is supported by a steel plate girder. In order to give stability to the cabin and to support the floor, the floor joists have been run through the machine at intervals of 12 ft. This arrangement leaves spaces in the machine, as indicated in the photograph, Fig. 3 [not included on this web site--MDB], so that the signalman can walk through the machine at convenient points instead of having to go around the ends when be may wish to go to the front of the cabin. The dimensions of the cabin are 16 ft. x 100 ft. 8 in.
In designing a machine for a plant of this magnitude it is important to consider what train movements have to be made most frequently, so as to save steps for the signalmen. In this case, instead of following out the old practice of putting all the switch and locking levers in the center of the machine and the signal levers at the extreme ends, the machine has been divided into three parts and is practically three interlocking machines, with levers on a common center in one frame; and the practicability and economy of this plan has been clearly evidenced and illustrated since the opening of the plant, as it requires but two operators to manipulate the levers.
There are in the plant as now operated 62 signals, 68 switches, 70 facing point locks, one movable paint frog and 39 crossing bars. The greatest distance at which a switch is operated is 1,242 ft.; the greatest distance at which a signal is operated is 2,492 ft. The levers have been in operation but a few days, but all of them move easily, the work having been put in carefully and double, anti-friction pipe carriers used. No selectors or switch-and-lock movements have been used in this plant.
