Nostalgia & History > Facing Point Lock Switches

I've posted this photo before but I have a question mainly about the two facing point switches labeled "FPL" east and west of the diamond on the tower board. Ok, so no matter which way the east and westbound Wabash trains are lined up, lever number 17 is used to lock both sets of points in place? I note that the switch on the PRR does not have a FPL or at least is not marked as such. I am wondering how common of a practice this was in interlockings. I haven't seen switches labeled like this on other tower model boards. In fact, in my ignorance I thought that all switches and derails in an Armstrong plant like this had an extra lever to lock them in place. If this Wabash line had more switches controlled by the tower operator in the plant, would they all be FPL's? Why isn't there an extra lever to lock the mainline derails in place? Also, I suppose it is a given if either or both of the switches would not lock in place, then a clear signal could not displayed?

The mainline derails marked "SLM" are apparently some kind of derail different than split derails. What are they? Sliding motion???

Edit: I posted a larger photo in hopes that it will be relatively easier to read.


Thanks in advance.



Edited 4 time(s). Last edit at 12/06/09 20:04 by wabash2800.

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wabash2800 Wrote:
-------------------------------------------------------
> I've posted this photo before but I have a
> question mainly about the two facing point
> switches labeled "FPL" east and west of the
> diamond on the tower board. Ok, so no matter which
> way the east and westbound Wabash trains are lined
> up, lever number 17 is used to lock both sets of
> points in place? I note that the switch on the PRR
> does not have a FPL or at least is not marked as
> such. I am wondering how common of a practice
> this was in interlockings. I haven't seen switches
> labled on other tower model boards. In fact, in my
> ignorance I though that all switches and derails
> had an extra lever to lock them in place. If this
> Wabash line had more switches controlled by the
> tower operator in the plant would they all be
> FPL's? Why isn't there an extra lever to lock the
> derails in place? Also, I suppose it is a given if
> either or both of the switches would not lock in
> place then a clear signal could not displayed?
>
> The derails marked "SLM" are apparently some kind
> of derail different than split derails. What are
> they? Sliding motion???
>
>
> Thanks in advance.

It looks like the FPL's and derails on the Wabash side are connected together to save lever space on the machine. This wasn't uncommon for armstrong plants. I remember that 'NS' Tower (PRR/B&O-NKP in Lima, OH) had this kind of arrangement. The mainline switch for the NKP and one portion of the crossover shared the same FPL lever on the machine.

As far as FPL use, generally they were located on most switches that were lever thrown inside the interlocking plant.


Cass Telles
"Slow-Approach-Slow" - 'Go by way of the B&O'
Railroads of NW Ohio
http://www.trainweb.org/rrnwoh

Thanks Cass, I note that the derails on the sidings are connected to the siding switch levers but the main derails are not connected to anything else.



Edited 2 time(s). Last edit at 12/06/09 19:31 by wabash2800.

Here is a crop from my Tiff image that may show the items referred to better.

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As SlwApprSlw noted, both locks on a crossover may have been controlled by a single locking lever.

As to why some switches may not have locks, there was a style of lever in which a single lever and rod controlled both the switch and the lock. When the lever was pulled, it unlocked the switch moved the points and relocked it in one movement.

LarryDoyle Wrote:
-------------------------------------------------------
> As SlwApprSlw noted, both locks on a crossover may
> have been controlled by a single locking lever.
>
> As to why some switches may not have locks, there
> was a style of lever in which a single lever and
> rod controlled both the switch and the lock. When
> the lever was pulled, it unlocked the switch moved
> the points and relocked it in one movement.

Right. A single lever could not operate a switch and a bolt lock (FPL). Both require a full throw of the lever. However, there was also a switch and lock movement that was designed to be operated by one lever; sometimes shown as S&L or SL instead of SLM. The lever would be gray and black instead of black (switch) or gray (lock). This is entirely dependent upon the hardware on the switch and has nothing to do with the lever except for the way the locking is cut.

A Hayes derail needs no lock lever. The FPL is only for the purpose of ensuring that the point is tight against the stock rail. The switch lever is locked in the locking bed by the signal lever out of the machine, as is a Hayes derail lever.

Some crossovers were arranged with a lever for each switch and a third to lock both. Some were arranged with a lever for both switches and a lock for both. The same with derails. Some had a separate lever for the switch and derail and a lock for the switch. Some had a lever for the switch, the derail, and the lock. Two appliances on a lever was not fun, although 2 locks was much easier than two switches or a switch and a derail. I had a few routes I hated to line, but fortunately, I worked with signal maintainers who kept the plants in top shape.

A good dispatcher knew all of the towers (even the ones worked by foreign lines) on the district and what routes were a mankiller. Really terrible to pull routes were avoided if possible - unless the operator was being a real jerk in which case there could be that unavoidable need to run a train through a mankiller route.

Have you encountered the forced drop locks yet? Forced drop locks are the locking interface between the electric world of signals and track circuits and the mechanical locking world. They are typically a box mounted on the side or back of the lever below the latch (generally on a Type A machine - vertical locking below the floor) or on a pedestal above the locking bed behind the lever (on S&F machines - horizontal locking behind the levers). They are held by route locking and time locking to prevent the route from being changed. They are released by a half squeeze on the latch, stop, release slightly, then finish squeezing the latch, or by a push button on the floor in the runway in front of the lever. If the FDL is not being held by route or time locking, it will release, the latch can be pulled fully, and the lever can be moved. If it is, the latch will not move. These don't show on the model board. They are typically on a FPL lever and that lever is cut in the locking bed as the master lever for a route - first in the machine, last out. The master lever locks the rest of the route in the locking bed.

After the route is lined and the signal is pulled off, the signal lever locks the route in the machine. If the signals are electric, restoring the signal starts time locking (which may require a clockwork release). During that time, the route is locked by the time locking locking the FDLs. If a train enters the plant and puts the signal to stop, route locking continues to electrically lock the route as long as any of the track circuits on the route are down. In a very large plant, there may be sectional release. Effectively, the plant is divided into sub-plants that release as soon as a train is clear of them, before the entire plant is clear. This allows the operator to start pulling iron for the next route behind the train moving through. It is also the reason for the rule prohibiting a change of direction within interlocking limits without operator permission.

TAW

Answer to the mainline derail mystery:

After reading through a book about interlockings (Locking by Frederick C. Lavarack, circa 1907), I have your answer to the letters "SLM". It stands for "switch and lock movement". TAW basically outlined the operation of the derail, but I'm going to add a little bit more to it.

If you look on the track diagram, you may noticed a heavy line near the derail, off to on side of the track diagram. This line represents a detection bar. As long as there was no conflicts with the lever alignment (aka conflicting routes or lockout from the lock bed), the derail would be able to be reversed. The detection bar would lock the derail from being thrown if there was a train standing on it. Other than the lock bed preventing the lever from being thrown, the detection bar did the final locking of the derail.

Here's something that leads to another question. How long was this type of derail operational? Detection bars were problematic to maintain due to weather and overall maintenance. Also, derails add to the cost of maintenance. My speculation would be that the derails and detection bars were removed due to maintenance issues. If they were removed, the levers would still have to be thrown. This is due to the need of a change in the lock bed and the costs associated with it. It would be cheaper for operators to throw 'phantom levers' even though nothing is connected to it.


Cass Telles
"Slow-Approach-Slow" - 'Go by way of the B&O'
Railroads of NW Ohio
http://www.trainweb.org/rrnwoh

I seem to recall a pushbutton or two on the floor at Wolcottville. I have also seen the kind of levers with a box in photos you refer to Tom.

TAW Wrote:
-------------------------------------------------------
> >
> Have you encountered the forced drop locks yet?
> Forced drop locks are the locking interface
> between the electric world of signals and track
> circuits and the mechanical locking world. They
> are typically a box mounted on the side or back of
> the lever below the latch (generally on a Type A
> machine - vertical locking below the floor) or on
> a pedestal above the locking bed behind the lever
> (on S&F machines - horizontal locking behind the
> levers). They are held by route locking and time
> locking to prevent the route from being changed.
> They are released by a half squeeze on the latch,
> stop, release slightly, then finish squeezing the
> latch, or by a push button on the floor in the
> runway in front of the lever.

SlwApprSlw Wrote:
-------------------------------------------------------
> Answer to the mainline derail mystery:
>
> After reading through a book about interlockings
> (Locking by Frederick C. Lavarack, circa 1907), I
> have your answer to the letters "SLM". It stands
> for "switch and lock movement". TAW basically
> outlined the operation of the derail, but I'm
> going to add a little bit more to it.


I've tried to download that book from UofM but it reads a file error...If that is where you got it, maybe you can send me the PDF via email?

>
> > Here's something that leads to another question.
> How long was this type of derail operational?
> Detection bars were problematic to maintain due to
> weather and overall maintenance. Also, derails add
> to the cost of maintenance. My speculation would
> be that the derails and detection bars were
> removed due to maintenance issues.

As far as I recall Cass, the derails were in operation to the end at Wolcottvile. If you look at employee timetables some interlockings did not have derails even in the classic steam era. I always wonder if they had been removed or never installed... I would surmise it is a little of both. However, I was always led to believe that much later some railroads removed them not only becuase they considered them a maintenance item but a Catch 22 as most of the few times a train would run the signal, it would not result in a collision in the plant but would cause damage to the plant, perhaps injury to the crews and damage to the train without a collision--not to mention blocking up a crossing of more than one railroad! In the 40's a New York Central freight ran signal at the plant in the fog that crossed the Vandalia (PRR) and the B&O at Auburn Junction, Indiana. as the plant was lined for a on coming B&O freight. Anyway, the NYC Pacific took the derail and rolled over on the embankment and killed one crew member (cut in half under the tender). The ICC suggested a working approach signal for the plant in the investigation.



Edited 4 time(s). Last edit at 12/07/09 16:44 by wabash2800.

wabash2800 Wrote:
-------------------------------------------------------
> SlwApprSlw Wrote:
> --------------------------------------------------
> -----
> > Answer to the mainline derail mystery:
> >
> > After reading through a book about
> interlockings
> > (Locking by Frederick C. Lavarack, circa 1907),
> I
> > have your answer to the letters "SLM". It
> stands
> > for "switch and lock movement". TAW basically
> > outlined the operation of the derail, but I'm
> > going to add a little bit more to it.
>
>
> I've tried to download that book from UofM but it
> reads a file error...If that is where you got it,
> maybe you can send me the PDF via email?

I would send you the PDF file via email, but I have the actual book, not the file. I think that kind of file format not computer friendly. lol :)


Cass Telles
"Slow-Approach-Slow" - 'Go by way of the B&O'
Railroads of NW Ohio
http://www.trainweb.org/rrnwoh

SlwApprSlw Wrote:
-------------------------------------------------------


> If you look on the track diagram, you may noticed
> a heavy line near the derail, off to on side of
> the track diagram. This line represents a
> detection bar. As long as there was no conflicts
> with the lever alignment (aka conflicting routes
> or lockout from the lock bed), the derail would be
> able to be reversed. The detection bar would lock
> the derail from being thrown if there was a train
> standing on it. Other than the lock bed preventing
> the lever from being thrown, the detection bar did
> the final locking of the derail.
>
> Here's something that leads to another question.
> How long was this type of derail operational?
> Detection bars were problematic to maintain due to
> weather and overall maintenance. Also, derails add
> to the cost of maintenance. My speculation would
> be that the derails and detection bars were
> removed due to maintenance issues. If they were
> removed, the levers would still have to be thrown.
> This is due to the need of a change in the lock
> bed and the costs associated with it. It would be
> cheaper for operators to throw 'phantom levers'
> even though nothing is connected to it.

Detector bars and derails are two separate things. They also protected switches. Detector bars were adjacent to the rail head and slightly above when the route was not locked. If there was a piece of equipment (train, car, engine) anywhere along the bar, the bar could not be raised to unlock the route. It didn't take a separate lever, it was part of the function of the switch lever. This function was replaced by track circuits. In the US, detector bars were generally replaced by track circuits by the 1920s.

TAW

Sounds like I need to get a copy of that book too. <G> It can't on the best seller list.

SlwApprSlw Wrote:
-------------------------------------------------------
>
> I would send you the PDF file via email, but I
> have the actual book, not the file. I think that
> kind of file format not computer friendly. lol :)

wabash2800 Wrote:
-------------------------------------------------------
> I've posted this photo before but I have a
> question mainly about the two facing point
> switches labeled "FPL" east and west of the
> diamond on the tower board. Ok, so no matter which
> way the east and westbound Wabash trains are lined
> up, lever number 17 is used to lock both sets of
> points in place?

I see that I never answered the original question. It's a kind of unusual arrangement, but I can see a couple of possible reasons. On the WAB on both sides of the diamond, the switch and derail are on one lever. A switch, derail (especially if it was a split point) and lock movement could be pretty hard to pull and pretty hard to keep in adjustment. A separate lock lever for each would mean an extra lever and locking. It could have meant another locking bar.

I don't think economy was the reason, though. There has to be a way for the Pennsy route to lock the WAB route & v. With a signal out of the machine, that's not a problem. Time locking is the problem. If the signal is put back in the machine on one or the other, time locking holds the route to prevent a train that is so close that it can't stop from having a conflicting route lined in front of it. The other railroad must also be locked until time locking releases. The way this is set up, 17 is not only the FPL for the two switches, it also serves as the route lever for the crossing. I would expect to find a forced drop lock on 17. In the locking, 17 in the machine prevents lining either WAB signal. If 17 is out of the machine, either WAB signal prevents restoring 17 and 17 prevents moving either switch. 17 in the machine is locked by either PRR signal out of the machine. If either PRR signal is pulled off, 17 is locked in the machine, locking the WAB signals in the machine.

This is where the forced drop lock comes in. Let's line up a Wabash. 17 is out of the machine. That prevents moving switches on WAB or lining signals on PRR. The WAB signal out of the machine locks 17. Now restore the WAB signal. The plant "goes into time"; the time locking prevents moving switches or lining up a conflicting route. It does that by electrically preventing the release of the FDL on 17. The operator can push the button on the floor or double squeeze the latch and it won't release. The effect is exactly the same as if the WAB signal were still out of the machine. For a PRR signal, it works the same way, except the PRR signal (and time locking) locks 17 in the machine instead of out.

Some really complex plants where this would not be easy to implement, and others that had only a crossing, used a crossing lever for this purpose. It worked the same way as 17 in this plant except it only selected the crossing route and had no switch lock function. such a lever would generally be brown (or sometimes yellow).

TAW