Sakhalia NetPHP PagesGraphics DivisionBaykal.esAcceptance of cookiesAcceptance of cookies

Railroad switching

There was a time when railroad switches were directly operated in place by operators, but it was often difficult for them to coordinate effectively their maneuvers. This problem was later solved by means of signal boxes fitted with remote switching and operated by a single person; to actuate the track switches, even at a distance of three kilometers, it would be enough to manage a number of levers; if the railroad switch does not move, the lever can give a warning to the operator by opposing a certain resistance; in such case it would be indispensable to manually control the railroad switch in place to avoid a disaster. The arrival of more modern switching centers allowed a single person to control a large number of individual track switches by means of small levers and electric panels showing the current status of the railway network, while automatic interlocking systems allow to prevent human errors in the maneuvers.

Old railroad switch
First signal boxes for railroad switching.

Otherwise, if what is required is to transfer a vehicle from a track to another track which runs parallel, it is sometimes used a rotatory platform fitted with two track sections disposed as a cross. It is not unusual that two trains meet each other while marching in opposite directions in a single-track line; in such case the train which arrives first must wait in the station, where it will be effectuated the crossing when the second train arrives. It can also happen that two trains meet each other while moving along the same track in the same direction; then the train which first reaches the station must grant precedence to the other train.

As stated, it is very important the automatization of signals; thanks to this system it is the very train which actuates a signal, setting it to stop other trains if necessary. Signaling block systems have the purpose of ensuring the safe circulation of trains. The first of these systems was built by British telegraph engineer Fothergill Cooke and installed in 1848 in the line Norwich-Yarmouth of the Great Eastern Railway. These systems are based in the subdivision of a line into many sections by means of signals, so in a particular section between two signals it is allowed only one train to stay at the same time. If the line has two tracks, each of these have independent sections; in a single track, it is necessary to dispose things in such a way that two trains marching in opposite directions meet each other in a section provided with a crossing track.

Let us see an example of how an operation is made between two nearby signaling block posts, placed in two positions named A and B. The operator in A, who is awaiting a train, requests to the operator in B to unblock the signal if the line is free, to allow transit for the incoming train; then it could be unblocked the signal and the train could pass. As soon as the train has passed, the operator in A immediately blocks the signal, but even if he does not, the signal will be automatically blocked by the train itself by means of an electric switch placed in the rails. The operator in A has also to inform the operator in B about the train passing, so he can block his own signal, not allowing any other train to transit until the first train has actuated the electric switch which automatically unblocks the signal, freeing so the line. This switch would be placed after the signal at a distance equivalent to at least the length of a long train, to ensure that when it is actuated the track section is really free.

It is easy to imagine the relation existent between the signaling block and the invention of the telegraph. In fact railway signaling uses a simplified version of such communication system, transmitting just a small range of signals such as "busy line" or "free line"; for reading these warnings electromagnetic circuits are used which represent the different signals in panels installed in the signal boxes, which are small masonry buildings where operators work in their maneuver benches, from which they control the railroad signals and switches. Modern railway signals and switches are all or almost all electric or electronic; they are fundamental for the safe circulation of trains and their automatization is intended for avoiding the human error, which often has fatal consequences.

Railroads in the cities

Already in the 17th century some inventive men had the idea of establishing services for public transport inside the cities or between these and the suburban areas, but given the preference for the utilization of private vehicles or stagecoaches, these ideas remained unrealized. In the beginning of the history of the railway, the railroads were used only in the mines and only later they started to be used by passenger cars towed by horses. The public transport properly said appeared in New York in 1832, with the introduction of the first tramcar, towed by horses as well. This line connected the downtown with the suburbs of Harlem. These cars were provided with tug shafts in both ends to allow to reverse the march without requiring the installation of rotatory platforms in the terminals of the line.

Almost 20 years passed before new lines were inaugurated in the city, but meanwhile the cars had increased their capacity by adopting a second story known as "imperial", accessible through stairs on both ends of the car. In England, however, the first tramcars did not appear until circa 1860 and this happened thanks to an American entrepreneur who had to suffer a strong and understandable opposition from the professional coachmen. Also in France, circa 1853, it was inaugurated the first tramcar which connected the Place de la Concorde in Paris and Saint Cloud. Slowly but successively, in all the main cities of Europe and America the railroads started to appear, and in 1870 almost all of them had at least a tramcar towed by horses.

Rotatory stagecoach, 1878
Henry Casebolt built in 1878 this railroad stagecoach for the public transportation service in San Francisco. This design with a rotatory body allowed to reverse the direction without having to turn around the wheel truck.
Public transport cars, 19th century
A small wagon fitted with skids, built by Stephenson specially for the temperatures of -40 Celsius degrees reached in Manitoba, and a Chinese car from 1880.

Continue reading...