Position Light Signals

[NW Mailing List]

Thanks for a brief history! 

Of course we all know that F. P. Patenell, signal engineer,
 On the Baltimore and Ohio, VASTLY improved the position light design when he create the Color Position Light signal system that was used by the B&O. :-) 

All joking aside.
 
I know for me, in the railroad history end of things, signaling is one of the most interesting and little discussed facets of the hobby. Railroads were as identifiable by their signals as they were by their locomotives...

Great stuff sir!

Eric







> On Jun 11, 2018, at 14:54, NW Mailing List <nw-mailing-list at nwhs.org> wrote:
> 
> I am delighted to see the interest in N&W Position Light Signals !
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> 
> 
> To help out with some background on the development of the PL, I have put up on Google Drive a number of articles, written in the early 1920s, giving the developmental history of the PL, which began in late 1914.  Several of the articles were penned by Alexander Holley Rudd, the inventor of the PL signal (he held the patent.)   Also, there are some very crucial articles by Dr. William Churchill, Corning Glass' premiere optical engineer who was involved in all kinds of signal issues of that day and assisted Holley Rudd with some of his problems.  You can download all the articles from this link:
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> https://drive.google.com/open?id=1PgtjCL7I7bNKFxAd7zvt_oJ-PPNfyWT1
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> 
> Also, perhaps a little tutorial on the three different versions of the PL may help someone.  I have attached a photograph showing the PL-1 (at the bottom,)  the PL-2 (middle) and PL-3 (top.)
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> The PL-1 came out in the early 1920s, probably first marketed around 1923.  The PL-2 followed about a decade later.  The PL-3 was out in the 1940s.  Although these three versions can be distinguished by their external appearance, the REAL DIFFERENCE  is the INTERNAL OPTICAL SYSTEMS.  Each version employes an entirely different optical system of lenses, prisms and reflectors, as will be readily apparent if you disassemble the lamp housings.  (The conical cover glasses made of NOVIOL glass remained the same through all three versions.)
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> The N&W originally installed the PL-1 version, and some of the PL-1's were still standing at Randolph Street the last time I was there, eight years ago.
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> Some time later, US&S came out with the PL-2 which had a much improved optical system and a greater "spread" of the beam of light, which was probably ideal for N&W's often curvy track.  In my time on the N&W (1960s-1970s,) almost all the signals were PL-2s.  Curiously, it appears that the N&W was the only railroad which bought the PL-2's.  And PL-2 replacement lamp housings were used when the original PL-1 housings rusted out or were damaged, so over the course of time the old PL-1's were not very numerous.
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> In the course of time, US&S came out with one final iteration, the PL-3, which had a still better optical system.  The evidence seems to indicate that the N&W used PL-3's only at a few very late interlocking rebuilds, e.g. Singer, and also when signaling the Virginian.
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> Firm dates for the introduction and discontinuation of the manufacture of these three product lines are hard to come by, and in many cases one has to make an educated guess based on dates at the bottom of the US&S parts catalog sheets.
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> The curious thing is that the N&W apparently did not purchase the PL-3's until the PL-2's were no longer available, and the Pennsylvania Railroad apparently never bought the PL-2's.   The best explanation may be that the PL-2's greater "spread" of light suited the N&W's track alignments, and the PL-3's more concentrated beam and greater range-of-signal-readability better suited the PRR's track alignments and speeds.
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> One final comment.  PL signals had serious corrosion issues.  The lamp housings were made of cast iron.  The side door weather seals were made of woven flax impregnated with a shellac-based compound.  Over time, the seals hardened and broke and water leaked into the housings, causing the inevitable rust.  The adjusting clips behind the backgrounds also rusted badly, and their inner surfaces could not be painted during routine maintenance without disassembling the signal.  Also, the large wire junction box (the "spider") behind the background was cast iron and rusted badly, especially where the six (or eight) diagonal pipes were threaded in.  In short, as designed the PL signal was something of a sponge for water, which led to structural failures due to corrosion.  About the only thing on a PL signal which would not rust out was the four bronze horizontal/vertical adjusting bolts inserted in the back of every lamp housing casting.
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> Did the N&W Magazine carry an article about the Position Light signals when they were first introduced?  If so, that would contain some valuable information for us railroad history types.
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> 
> -- abram burnett
> 
> ===========================================
>                   Sent to You from my Telegraph Key
> Successor to the MAGNETIC TELEGRAPH LINE of 1844
> ===========================================
> 
> <PL-3_PL-2_PL-1_Restored_4X6_2012_04_23-FB.jpg>
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