[N&W] Re: Signals

[nw-mailing-list at nwhs.org]

>1.  What was the manufacturer(s)/make(s)/model(s) for the semaphore 
>signals that predated the position light signals on the N&W?
>
>2.  What was the manufacturer(s)/make(s)/model(s) for the position light 
>signals on the N&W?
>
>3.  Can anyone point me to good references on placement of signals either 
>in general or N&W specific?
---

Jim Cochrane, et al:

 From observation, the N&W installed Union Switch & Signal Model PL-2 ("PL" 
for "position light") for home and automatic block signals.

The PL-2's are distinguishable by the short 10" hood ("visor") and the lamp 
access side plates held on by single set-screw. US&S later (and last) 
version of the PL signal was the PL-3, which is distinguishable by longer 
14" hoods and two bolts holding on the lamp access side plates.  The optics 
were also improved marginally in the PL-3, but the color and design of the 
"angel tit" conical coverglass was not changed.  The PL-3's were being sold 
by the mid-1930s.

Now, as for the dwarf signals, there are also two styles.  Based on a check 
of US&S catalogues which I just made, US&S did not distinguish the two 
types of dwarfs by numbers, but simply called them "old style" and "new 
style."  The difference in the old and new styles is how one accesses the 
lamps.  The old style had side plates on the left and right sides, and 
re-lamping one of them really chews up the knuckles.  On the new style, the 
entire back of the signal is removed to gain access to the lamps.  The new 
style PL dwarf was available around 1930.

Another variation in the dwarf signals is the quadrant of the arc.  On the 
old style signals, the quadrant was in the 12 o'clock-3 o'clock 
quadrant.  On the new style dwarfs, the quadrant is in the 9 o'clock-12 
o'clock quadrant.  The reason for this change occurred on the Pennsylvania 
RR, the biggest user of PL signals.  With the old style PL dwarfs, there 
was inadequate clearance between the cylinders of the newer, larger engines 
and the top of the dwarf signals, and the newer engines would sometimes 
clip them off.  Therefore, the quadrant of the arc was changed from the 
12-3 o'clock quadrant to the 9-12 o'clock quadrant.

If you need photocopies or scans of the US&S catalogue drawings, or 
close-up photographs, contact me off-list.

Hopefully someone will some day do a good research paper on the N&W's 
development and application of the PL signal.  What is amazing is that 
"parent" PRR had a really good system of aspect logic worked out for the PL 
signals, but N&W chose to use US&S's signal hardware but develop its own 
signal "logic."  Two examples:  (1) Those beautiful 3-arm (yes, three ! ) 
PL signals that we see in photographs of the 1940s-early 1950s on the 
Radford and Pocohontas Divisions.
(2) The fact that N&W used, on its dwarfs, rows of lights in both the "/" 
and the "\" directions to indicate "Restricting."   N&W could have saved 
itself a lot of money if it had adopted what the PRR had already perfected, 
instead of fiddling around.  In  my humble opinion, N&W's signal people 
were country boys who thought they didn't need the sophistication employed 
on a 4-track, fast railroad.

The N&W began installing colored roundels (green or red, as required) in 
both high and dwarf signals about 1960-61.   Before that, all lenses on 
high signals were "noviol" (meaning "no violet") yellow, and all lenses on 
PL dwarfs were clear, backed up with a sandblasted flat glass diffuser disc.

In 1981 or 1982, the PRR Tech & Historical Society published an excellent 
article in its journal, The Keystone, on the history of the development of 
the PL signal.  I might be able to find a photocopy for you.

As for signal placement, that's easy.  (Take it from one who was involved 
in this stuff professionally for years, albeit on another railroad.)  Home 
signals are placed at the entrances to interlockings, and automatics are 
placed based on (1) braking distance to the next signal while running at 
maximum authorized speed, and (2) good "preview" for the engineman.

And finally... Don't ever let any jack-leg tell you that signals have 
"heads."  They
don't !   One properly speaks of "arms" on a signal, e.g. "top arm," 
"bottom arm," "middle arm."  Those technical nomenclatures apply to 
semaphore signals, PL signals and CL (color light) signals equally.

Interesting that you should post this question this evening... I just came 
in from re-lamping an N&W signal that's in the back yard !

-- Abram Burnett
   New Cumberland, PA
   (signal and telegraph dabbler)

Jim,

I should have added something on usage of the various types of signals. 
I'll try to make this simple, and assume you are talking 1950s of later 
(i.e., when the two arm home signals had come into use, rather than three arm.)

I'll start with two definitions.

A "Home Signal" is always controlled by a lever operated by the operator or 
train dispatcher. It may be either a high signal or a dwarf signal, 
depending on how much sight distance is needed (i.e. based on the speed at 
which trains will be approaching.)

An "Automatic Block Signal" is not controlled by a lever, but "does its 
thing" based exclusively on the conditions of block occupancy ahead.

Automatic Block Signals are always high signals, because they govern trains 
approaching at track speed and thus greater sight distance is needed, and 
may mounted either on a ground mast or on a signal bridge. Generally, they 
give indications of "Clear" (the track is clear for two blocks,) "Approach" 
(track is clear for one block only, so approach the next signal prepared to 
stop,) or "Stop and Proceed" (block is occupied.)

Here's a rule of thumb: For Home Signals, the most restrictive indication 
is Stop. For Automatic Block Signals, the most restrictive indication is 
Stop and Proceed.

So, which signals have two arms, and which have only one arm? To make it 
simple, most high Home Signals on the N&W were two arm signals. Most 
Automatic Block Signals were one arm. The one place you would/will find 
Automatic Block Signals having two arms is when they are the "distant 
signal" to an interlocking and have to give an indication requiring 
"approach the next signal at medium speed" or "approach the next signal at 
slow speed."

Dwarf signals have always been used where moves will be approaching at 
"slow speed" (defined as 15mph,) which means that they don't need great 
sight distances to be able to comply with a stop indication. Dwarfs were 
generally used in Rule 251 territory (one direction automatic block 
signaling on a track) for trains running against the current of traffic. By 
rule, trains running against the current of traffic were required to 
approach all home signals prepared to stop, so a dwarf would suffice. N&W 
also had an interesting practice of peppering dwarf signals within big, 
complex interlockings (like Randolph Street, Roanoke,) and at such places a 
train might need to get two or three or four favorable signals to "get 
through" an interlocking, from one end to another. The reason for placing 
multiple dwarfs at places like that is, in technical lingo, "trailing 
release circuits" ... That is, the train only has to clear part of an 
interlocking, not the whole thing, before switches release and can be lined 
for another movement. Dwarf signals are almost unviersally "home signals."

If you have any specific questions, I'd be happy to take a whack at them.

-- Abram Burnett
E-mail: Pius10th at aol.com