Doug Kerr
Well-known member
This is a shot of the heads of a bidirectional train order semaphore signal outside the former railroad station in Columbus, N. M., a charming little town just three miles from the US-Mexico border.
Douglas A. Kerr: Train order semaphore signal, Columbus, N.M.
The railroad itself is long gone, its right of way in those parts having been repurposed into U.S. Route 9. The former station is now the headquarters and museum of the local historical society.
The train order system was once an important form of train control. In it, the movement of trains was governed by detailed written orders given to the train crew at stations or intermediate signal "huts". There were two kinds of orders. One had to have a copy signed by the train engineer and conductor for proof that it had in fact been delivered. The was not required for the other kind, which could just be "handed to" the engineer.
It was soon realized that time could be saved if, for the latter kind of order, the train didn't have to stop for the engineer to receive it, but rather the order could be given to the engineer "on the fly". This was done by tying the rolled-up order to a bamboo hoop, which was held up in a wood fork (later, a permanent metal frame) where the engineer could put his arm through the hoop to "snag" it.
In any case, as the train approached, for example, a station, a semaphore signal was used to advise the engineer of what he needed to do. Using the kind of signal seen in the picture above, If there was no train order of either kind (and in fact no passenger wishing to get on the train), the semaphore arm was downward (perhaps 60-70³ below the horizontal) ("Proceed"). If the train needed to stop to receive the first kind of train order (or to receive a passenger), the semaphore arm was horizontal ("Stop"). If there was a train order of the second kind for the train, so the train did not need to stop but should perhasp slow down and the engineer get ready to "snag" the train order hoop, the semaphore arm would be upward (perhaps 60-70³ above the horizontal) ("Train Order").
So the state of the signal could be seen after dark, an oil lamp would shine through one of three colored lenses (formally called "roundels", pronounced "ron-DELS"). Although a different scheme was used at first, before long the convention became, for the arm down ("Proceed"), green; for the arm horizontal ("Stop"), red; and for the arm up ("Train Order"), yellow.
But, after train order operation became obsolete, the signal we see was repurposed for direct signaling, and the upward position became obsolete. And so the yellow roundels were replaced with metal plates (the ones we see look white).
(The green roundels look blue in this picture, in part owing to the high color temperature of the background sky - I did no color balance here.)
Each of the two signals (one facing in each direction, for trains traveling in both directions) was moved into one of its (original) three positions by a vertical pipe, which connected via a bell crank at the base of the signal mast to a horizontal pipe leading into the station, where it was moved by a lever operating in a quadrant which allowed it to be retained in one of the three positions. (One of those original positions of the control lever - "Train Order" - is now blocked off by a metal plate.)
An ingenious mechanism assured "fail-safe" operation in the case of the breakage or disconnection of this linkage. If the semaphore arm was originally down ("Proceed"), the counterweight we see fell, raising raised the semaphore arm). When the arm reached horizontal ("Stop") the counterweight hit a stop so it would not raise the arm above horizontal.
But the counterweight arm drove the semaphore arm through the engagement of a lug on each arm such that, in normal operation, despite the fact that the semaphore arm could not go beyond the horizontal position of the semaphore arm, the semaphore arm could continue upward to the "Train Order" position.
But if the arm were in the upward posiition when the operating linkage broke or became disconnected, the weight of the arm itself would drive it down. But when it reached horizontal ("Stop"), the lugs between the semaphore arm and the counterweight arm contacted and the weight of the counterweight prevented the semaphore arm from continuing its travel. Thus it ended up in the safe "Stop" position.
Simple but very clever.
Yes, my research into this type of signal gave incomplete information, and I had to finish the job by "reading between the lines" and "reverse engineering", in part from the above photo.
Best regards,
Doug
Douglas A. Kerr: Train order semaphore signal, Columbus, N.M.
The railroad itself is long gone, its right of way in those parts having been repurposed into U.S. Route 9. The former station is now the headquarters and museum of the local historical society.
The train order system was once an important form of train control. In it, the movement of trains was governed by detailed written orders given to the train crew at stations or intermediate signal "huts". There were two kinds of orders. One had to have a copy signed by the train engineer and conductor for proof that it had in fact been delivered. The was not required for the other kind, which could just be "handed to" the engineer.
It was soon realized that time could be saved if, for the latter kind of order, the train didn't have to stop for the engineer to receive it, but rather the order could be given to the engineer "on the fly". This was done by tying the rolled-up order to a bamboo hoop, which was held up in a wood fork (later, a permanent metal frame) where the engineer could put his arm through the hoop to "snag" it.
In any case, as the train approached, for example, a station, a semaphore signal was used to advise the engineer of what he needed to do. Using the kind of signal seen in the picture above, If there was no train order of either kind (and in fact no passenger wishing to get on the train), the semaphore arm was downward (perhaps 60-70³ below the horizontal) ("Proceed"). If the train needed to stop to receive the first kind of train order (or to receive a passenger), the semaphore arm was horizontal ("Stop"). If there was a train order of the second kind for the train, so the train did not need to stop but should perhasp slow down and the engineer get ready to "snag" the train order hoop, the semaphore arm would be upward (perhaps 60-70³ above the horizontal) ("Train Order").
So the state of the signal could be seen after dark, an oil lamp would shine through one of three colored lenses (formally called "roundels", pronounced "ron-DELS"). Although a different scheme was used at first, before long the convention became, for the arm down ("Proceed"), green; for the arm horizontal ("Stop"), red; and for the arm up ("Train Order"), yellow.
But, after train order operation became obsolete, the signal we see was repurposed for direct signaling, and the upward position became obsolete. And so the yellow roundels were replaced with metal plates (the ones we see look white).
(The green roundels look blue in this picture, in part owing to the high color temperature of the background sky - I did no color balance here.)
Each of the two signals (one facing in each direction, for trains traveling in both directions) was moved into one of its (original) three positions by a vertical pipe, which connected via a bell crank at the base of the signal mast to a horizontal pipe leading into the station, where it was moved by a lever operating in a quadrant which allowed it to be retained in one of the three positions. (One of those original positions of the control lever - "Train Order" - is now blocked off by a metal plate.)
An ingenious mechanism assured "fail-safe" operation in the case of the breakage or disconnection of this linkage. If the semaphore arm was originally down ("Proceed"), the counterweight we see fell, raising raised the semaphore arm). When the arm reached horizontal ("Stop") the counterweight hit a stop so it would not raise the arm above horizontal.
But the counterweight arm drove the semaphore arm through the engagement of a lug on each arm such that, in normal operation, despite the fact that the semaphore arm could not go beyond the horizontal position of the semaphore arm, the semaphore arm could continue upward to the "Train Order" position.
But if the arm were in the upward posiition when the operating linkage broke or became disconnected, the weight of the arm itself would drive it down. But when it reached horizontal ("Stop"), the lugs between the semaphore arm and the counterweight arm contacted and the weight of the counterweight prevented the semaphore arm from continuing its travel. Thus it ended up in the safe "Stop" position.
Simple but very clever.
Yes, my research into this type of signal gave incomplete information, and I had to finish the job by "reading between the lines" and "reverse engineering", in part from the above photo.
Best regards,
Doug
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