A General Discussion' Illustrating the Apparatus
And Methods Now Used for This Purpose
Page Two
| They also have an advantage on electric lines where the rails are used for the return of the propulsion current. The electric crossing bell was first put out as a large gong, either a single gong or as a double gong with the clapper vibrat-ing between them. Later a locomotive type bell was designed. Everyone is familiar with the time-honored crossing watchman and his small watch house beside the track at the busy street crossings in the cities and towns. The crossing watchman is one of the means employed by the railroads to pension, after a manner, some of their employs, and many a veteran of the different branches of the service is now holding down the position of watchman in his home town. This is a very effective way of protecting a crossing, but on account of the salary of the man is rather expensive and cannot he afforded except at a comparatively few crossings. The expense is doubled if a day and night service is maintained; therefore, in many cases, only a day service is in force, it being conceded that a day service is the most important. But many crossings are just as dangerous at night, particularly those used frequently by automobiles. |
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| As the crossing bell cannot be heard above the noise made by the engine in an automobile, it has lost considerable of its use-fulness as a means of protection. Thus there has risen a demand for something better than the bell and not as expensive as the watchman. As a result we have the development of a visible means of warning. In order to make it effective it must have action at the time of danger, and this action should be visible both day and night. There has been designed several devices that serve this purpose. One has a large disk on the end of a pendulum that swings in such a manner as to warn anyone on the highway. It uses the track circuit and interlocking relay the same as the crossing bell. The local operating circuit is connected to solenoids which operate a rocking shaft, and the make and break of the circuit is timed so as to add the proper impulse |
Flash-Light Type and Bell (left), and Spring Type Bell
(right).
| to the regular beat of the pendulum. The pendulum is connected to the racking shaft and the disk on the end of the pendulum is colored red to attract attention. A red light is also placed in the center of the disk so as to give warning at night. The pendulum can also be operated by a motor and a train of gears. Another device has a row of red electric lamps placed in a case and connected to a set of contacts. By means of a motor these contacts are successively closed and opened so as to illuminate and extinguish each light in succession. This flashing gives the appearance of a bright swinging red light. Bells can also be used in connection with any of the above devices so as to give an audible warning, as well as a visible warning, both day and night. Some railroads have on hand a number of discarded disk signals and in some cases these are being used at highway crossings for the purpose of giving a visible warning both day and night. There remains one other means of highway protection to be considered and that is the crossing gate. The crossing gate requires the service of a gateman to operate it, and it is, therefore, more expensive on account of the combined operation and mainenance than either a flagman or the automatic flagging device. |
Automatic Gates
| But the gates overcome several difficulties. The gateman is usually in an elevated tower, from which position he commands a view of the track in each direction, and also he can protect the traffic in both directions on the highway. This is especially valuable when there are two or more tracks, as a second train may be approaching a crossing before a train that is passing has yet cleared the crossing. The gate will tend to prevent people on the highway from rushing on the track in the face of the approaching train. The gates extending, as they do, from one side of the highway to the other offer a very distinctive barrier to any approaching pedestrian or vehicle. At night a light is hung on each gate. The gateman is also provided with a gong or bell with which he can warn anyone near the cross-ing that a train is coming and he is about to lower the gates. Although the gates are sometimes connected direct by means of rods or wires to levers in the gate tower, the most common type is the pneumatic gate. Each gate post contains a set of cylinders, one for lowering the gate and one for raising the gate. These cylinders are connected by pipes to a bypass valve in the gate tower so that compressed air can be supplied to either cylinder as desired. Compressed air is supplied either by a pump in the hands of the gateman or at a very busy crossing by an air compressor operated generally by a small motor. A later type of gate is that operated direct by electricity. A small motor about one-half horsepower is placed in each gate and the circuit connected to a switch in the tower. A double-throw switch is used so as to reverse the current and thus provide for either lowering or raising the gates. In addition to the gates controlled by a gateman in the tower there is now in use at some crossings, where neither the railroad nor the highway has a heavy traffic, a style of automatic gate. This gate, instead of being a solid wooden barrier, as is the other style of gate, is a very flexible protecting device. It consists of a piece of pipe that is lowered to a horizontal position at a point sufficiently high to let the average vehicle pass beneath, but a number of ropes or chains are suspended from the pipe to attract attention to anyone attempting to cross the tracks while the gate is in the warning position. If the gate should fail to raise after the train, the vehicle can pass by brushing aside the ropes or chains. From the foregoing it will be seen that every crossing of a highway with a railroad at grade requires some protection. The protection afforded the public on the highway depends upon the amount of traffic on the highway, the speed of the passing railroad trains and the local conditions surrounding the crossing. |
The Signal Engineer, July, 1914.
Thanks to Per Oloffson for contributing this article.
1/12/01
