Model Board Symbology Questions

[NW Mailing List]

> At one time, there was a derail on the “new” main, just east of the passenger platforms. These don’t show on the model board. Could that because they were interlocked with signal 20L, so didn’t require a lever (and designation)? A photo of the derail is here:
> https://www.nwhs.org/archivesdb/detail.php?ID=144464

Doubtful that a derail would operate automatically in connection with operating a signal lever. I’ve never heard of such a thing (not that I was ever an operator (other than getting thrown in the seat one place for a few hours as part of my management training - of course, under the supervision of the on-duty Operator) - on the other hand, I am currently qualified as a dispatcher at the Illinois Railway Museum so I do get to sit in the tower there and play with the levers).

From what I’ve seen, derails seem to be more about stopping standing equipment that gets loose. So to have derails on the Old Main where equipment probably was left standing makes sense. To have them on a high-speed main risks making things worse. So probably removed at some point as unneeded or an extra point of failure.

> Thanks for pointing that out - I had assumed the crossover was controlled by Circleville for the reasons you later stated (Old Main access). Looking at the full photo of the model board again, I realized that there are no odd-numbered devices, other than those two derails. So now I’m confused (and realize how much I don’t know). I’m attaching another version of the same model board, which includes the east end (where there quite a few more switches) - maybe I missing something.

Those east end switches all appear to be hand-throw switches as well. The switch just west of the 22L/R signals may be a spring switch. With all the scratches on the model board, it’s hard to tell but I think that’s a spring switch symbol (the dollar sign ($)) just above it. 

The last post I mentioned that normally R signals were for movement to the right on the model board with L signals to the left. 22L/R is an exception. Both are for movement to the left but assuming it is a spring switch, it makes sense. The signals are mutually exclusive (only one can be cleared at any time) but because it’s a spring switch rather than a power switch, both routes are valid at the same time (if it was a power switch, both signals could be 22L with the switch position determining which signal cleared).

Interestingly at the Illinois Railway Museum, we have a similar setup at the east end of our station with three tracks converging over spring switches. But there, all three home signals are controlled by a single lever and there are two switch levers that we use to tell the interlocking how it should assume the switches are lined even when they aren’t. The assumed position only affects trailing moves (determining which of the three home signals to clear); for facing point moves, it uses the actual alignment to determine whether it should display Clear for main line moves or Restricting for moves into the station). But if those spring switches are ever converted to power switches, the circuitry is already there. As it is now, it’s easy to clear the wrong signal and then need to run time so most dispatchers prefer to leave it in automatic (due to us only having a dispatcher in the tower on busy days, all the interlockings can be placed in automatic).


> Regarding the 6R hold out signal, that makes sense to me. There were six street crossings in the approx 1 mile between 6R and the tower; seven counting the road that the diamond was in the middle of. Now I’m curious what the purpose of 8R was. Perhaps a legacy of a different operating reality.

6R is not interlocked with anything - it’s just a tower controlled signal that will always clear unless that red block beyond it is occupied. But 8R is the EB Main home signal that is interlocked with the other signals governing the diamond. Clearing 8R locks out 4R and 12L for moves on the PRR; 6R locks out nothing. 

Looking at it more, another oddity is it appears the tower controls the advance signal on the PRR at the bottom of the photo with the 2R lever even though the hollow track line implies no automatic block signal protection. Even without block signals, I would have expected the advance signal to operate automatically off what 4R was displaying.

With no switches other than the two derails, the interlocking is fairly simple. Obviously, clearing one signal locks out the opposite direction signal. Beyond that, it should be fairly simple:
Clearing 4R or 12L (PRR home signals) locks out 8R, 10R, 16R, 16L (looks like a single lever was used for both directions of the Old Main), 18L, and 20L as well as derails 7 and 9
Derails 7 and 9 in derailing position lock out 16L and 16R; in non-derailing position lock out 4R and 12L
Clearing 8R, 10R, 16R, 16L, 18L, or 20L lock out 4R and 12L

Note, back to the question of why both 6R and 8R, clearing a PRR move (4R or 12L) would not lock out 6R so switching could still be done at the west end (looking at a current day overhead picture of Circleville, I assume 6R was probably by the creek bridge geographic north of High St.; if the small yard that is currently there existed back when the model board photo is from (no reason for the model board to show the yard), then you definitely would not want 6R to be acting as the home signal for the diamond (now gone but I assume was at S Court St.). You want the diamond circuits to be as short as possible and 6R is way too far away for that.

-- 
Larry Stone
lstone19 at stonejongleux.com





> On Dec 29, 2019, at 8:00 PM, NW Mailing List via NW-Mailing-List <nw-mailing-list at nwhs.org> wrote:
> 
> Thanks for the detailed explanations from Larry Stone and Eric of Ashville. Each of you (and Fred) explained it in slightly different ways, which in aggregate made each other’s points clear. I have a couple of follow up questions.
> 
> Larry Stone wrote:
> The triangles 9 and 17 were probably derails controlled by the tower. Typically odd numbered levers were used for track devices (switches, derails, and movable point frogs on diamonds) with even numbered levers used for signals,
> 
> At one time, there was a derail on the “new” main, just east of the passenger platforms. These don’t show on the model board. Could that because they were interlocked with signal 20L, so didn’t require a lever (and designation)? A photo of the derail is here:
> https://www.nwhs.org/archivesdb/detail.php?ID=144464
> 
> Larry continues:
> 6R is a bit of an odd duck as it appears to be a controlled signal that governs moves over hand-operated switches (no lever number shown for the crossover or switch on to the Old Main).
> and
> Typically odd numbered levers were used for track devices (switches, derails, and movable point frogs on diamonds) with even numbered levers used for signals,
> 
> Thanks for pointing that out - I had assumed the crossover was controlled by Circleville for the reasons you later stated (Old Main access). Looking at the full photo of the model board again, I realized that there are no odd-numbered devices, other than those two derails. So now I’m confused (and realize how much I don’t know). I’m attaching another version of the same model board, which includes the east end (where there quite a few more switches) - maybe I missing something.
> 
> Regarding the 6R hold out signal, that makes sense to me. There were six street crossings in the approx 1 mile between 6R and the tower; seven counting the road that the diamond was in the middle of. Now I’m curious what the purpose of 8R was. Perhaps a legacy of a different operating reality.
> 
> <PastedGraphic-2.png>
> 
> Matt Goodman
> Columbus, Ohio, US 
> 
> On Dec 29, 2019, at 9:49 AM, NW Mailing List <nw-mailing-list at nwhs.org> wrote:
> 
> I can answer the R / L question. Nothing to do with the side of the track the signal is on. 6 is the lever controlling the signal and R indicates the direction to turn the lever to clear that signal. It was normal to have two signals which could not be cleared at the same time (typically opposing moves on the same track) to be controlled by a single lever. Turn the lever to the right to clear the R signal and to the left to clear the L signal. Note that on the model board that all R signals govern moves going right on the model board and all L signals control moves going left. It appears that one level for both directions was not done at this tower although I cannot see why. For instance, EB on the EB main is lever 8R while WB on the same track is 18L - both could have been handled by a single lever since you can’t clear both signals at once.
> 
> It was even common to have multiple signals controlled by the same lever where the position of a switch determined which of multiple signals would clear. For instance, a simple end of double track could be controlled by a single signal lever and a single switch lever. If you had two tracks going eastbound (which we’ll say was to the right on the model board) merging into one, all you needed was lever 1 to control the switch and lever 2 to control the signals. Both eastbound signals would be designated 2R and when you selected 2R, which of the two cleared depended on the which way the track switch was set. Westbound, 2L cleared that signal but what it displayed (Clear vs. Diverging Clear) depended on the switch (keep in mind that all the operator controlled for a signal was to have it display Stop or have it display the aspect appropriate to track conditions - when an operator cleared a signal, it then operated like an automatic signal to determine what specific aspect to display).
> 
> The triangles 9 and 17 were probably derails controlled by the tower. Typically odd numbered levers were used for track devices (switches, derails, and movable point frogs on diamonds) with even numbered levers used for signals,
> 
> The four digits signals are automatic that are on the model board for information only. Any signal with an R or L was controlled by the tower. 6R is a bit of an odd duck as it appears to be a controlled signal that governs moves over hand-operated switches (no lever number shown for the crossover or switch on to the Old Main). In addition, there appears to be no controlled signals over those switches westbound. So 6R is what I would call a “hold out” signal. The operator would use it to hold an eastbound train west of 6R when he was unable to clear 8R (the next signal) for a move across the diamond. By doing this, he could protect westbound moves off the Old Main going across to the Westbound Main or at least keep the switch and crossover clear until he could get the eastbound through (also possible is that there were road crossings between 6R and 8R and by holding a train at 6R, you kept them clear as well).
> 
> Red and yellow blocks is just to make each block distinctive on the board. No meaning beyond that.
> 
> -- 
> Larry Stone
> lstone19 at stonejongleux.com
> 
> 
> 
> 
> 
>> On Dec 28, 2019, at 4:31 PM, NW Mailing List via NW-Mailing-List <nw-mailing-list at nwhs.org> wrote:
>> 
>> Hi All.
>> 
>> I have a photo of Circleville Tower’s model board and have some questions about the symbology/nomenclature used. See the attached photo for references.
>> 
>> 	• Signal 6794 - The symbol for this signal has what appears to be a lower arm. Signal 6778 does not have this. What is it?
>> 	• Signal 6R is similar in appearance to 6778, except that 6R has a “hollow” quadrant. What does this difference indicate? Is it a home signal compared to an ABS signal perhaps (6R seems to be within the scope of the tower, based on dad’s recollections).
>> 	• Signal 6794/6778 are numbered based on milepost; what does 6R, 10L and similar mean? That they are within the interlocking plant?
>> 	• What do Triangles 9 and 17 on the Old Main indicate (for reference, the old SV main was used to switch local industries, and is still in place today)
>> 	• Similarly, does the R / L simply indicate which side of the track the signal is on? If so, why is this needed vs. just having unique numbers?
>> 	• Is there any significance to the red/yellow alternating block colors beyond making it easier to see where each starts and stops?
>> 
>> <IMG_1218.jpeg>
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