N&W CPLs, the last generation

NW Mailing List nw-mailing-list at nwhs.org
Tue Dec 31 12:41:36 EST 2019


We won’t hold it against you. N&W did replacements with some PL3s Dean just east of Prichard and Oakvale  two location that I can remember  

Larry Evans


From: NW-Mailing-List [mailto:nw-mailing-list-bounces at nwhs.org] On Behalf Of NW Mailing List
Sent: Tuesday, December 31, 2019 7:42 AM
To: N&W Mailing List <nw-mailing-list at nwhs.org>
Subject: Re: N&W CPLs, the last generation


Gentlemen, I must confess to a gross slippage-of-the-mental-cogs on my part... 


It was the PL-3s which the N&W did not use. 


The PL-2's were developed sometime around 1940, and its optical system provided for a horizontal **spread** of the forward-focused light about 30 percent greater than that of the original PL-1 optical system. 


Thus, the PL-2 was obviously designed for railroads which had a significant amount of curvature.  It was the perfect PL signal optical system for the N&W. 


The PL-3, on the other hand, seems to have been designed for concentration of the beam of light emitted and, thus, for range of readability.  It was apparently only bought by the PRR and the Long Island RR. 


The tragedy is that the correspondence and literature on why these different optical systems were developed seems to have been completely lost.  The best one can do is talk with some of the retired signal engineers from US&S, none of whom go back to the day when all this signal technology was being developed. 


My apologies,  Had I sat on my post for a day or two, the error would have leapt off the page at me. 


I accept my error, and regret it. 


Yours penetentially, 


-- abram burnett 


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