N&W AC Signaling in 1913

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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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http://nwhs.org/mailinglist/2014/20140325.NW_AC_Track_Circuits_Signal_Engineer.pdf
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