[N&W] Re: Signals
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nw-mailing-list at nwhs.org
Mon May 31 14:43:26 EDT 2004
>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
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