N&W AC Signaling in 1913

[NW Mailing List]

Reading the article, I'm curious about the nature of the "foreign 
current" problem. Is this in the track or in ground return?

Jeff Cornelius

-----Original Message-----
From: NW Mailing List <nw-mailing-list at nwhs.org>
To: NW Mailing List <nw-mailing-list at nwhs.org>
Sent: Tue, Mar 25, 2014 3:15 pm
Subject: N&W AC Signaling in 1913

I am attaching a PDF containing two articles from Signal Engineer 
magazine of 1913, by J.A. Beoddy, General Signal Inspector of the N&W. 
The articles detail the installation of AC track circuits in 1912 and 
1913, at Elkhorn Tunnel, between Bridge 7 and Suffolk, and between 
Nottoway and Burkeville.

Some historical background... The first electrified trolley system was 
built at Richmond in 1888, by Frank Julian Sprague (his Sprague 
Electric Company still survives.) By 1903, Jacob Baker Sprague had 
invented an AC track relay (the "vane" relay) and in 1904-05 vane 
relays and AC track circuits were installed on a California interurban 
operated by DC propulsion. Between 1906 to 1910, the AC track relay was 
developed for steam roads. (The AC vane relays in my collection all 
show a 1910 patent date on them.)

Prior to the invention of AC track circuits, power for railroad signal 
systems was made with "primary batteries," where a maintainer placed a 
piece of copper and a piece of zinc in a glass jar, and added sulphuric 
acid. This battery gave about 1.25 volts and lasted perhaps six months 
before it had to be dumped and "rebuilt" with copper, zinc and acid. If 
6 volts (or thereabouts) was required, four such cells had to be wired 
together in series. Remember, there were no storage batteries + trickle 
chargers in this time. Producing DC voltage for railroad signal 
applications was, therefore, an expensive and labor intensive 
operation. And remember, too, that this was three decades before "rural 
electrification." There was commercially produced electricity available 
in some cities, but in the smaller towns and countryside the railroads 
could not go to a utility and order a power drop at remote locations. 
It is for this reason that many larger railroads built their own power 
houses and installed transmission lines on their own pole line (ranging 
from 440 volts to 4400 volts.)

So this is the background of General Signal Inspector Beoddy's 
articles. The N&W was installing state-of-the art apparatus.

-- abram burnett


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