Cowan

[nw-mailing-list at nwhs.org]

Has anyone given any thought to Cowan Tower, installed (I have heard) in 1914?

Some thoughts from my end... Mebbe you'se chaps can elucidate with 
information you have...

1.)  Prior to the installation of Cowan and it's remotely controlled 
interlocking at the east end of the Low Grade Tunnel ("Bluff,")  Pepper manually 
blocked trains through the tunnel with Belspring.  When Cowan and Bluff were 
installed, that shortened up the single track manual block operation by something 
like three miles.  Quite a saving on a busy piece of single track.

2.)  Cowan probably was given a cabinet-model EP (electro-pneumatic) machine. 
  Union Switch & Signal's Model 14 EP interlocking machine (which some called 
a "crank lever machine")  was in its final stage of development by that time, 
and the original EP machine no doubt lasted up until Cowan tower was closed 
in 1948 or so.

3.)  But how about the control of Bluff, a mile to the east?  Obviously there 
were two westbound semaphore home signals there which needed to be controlled 
(and maybe even an eastbound signal.)  And obviously there was a switch.  

I'd surmise that the switch was an "air switch" (probably A-1 switch movement 
with a Style C pneumatic valve operating it... rather typical equipment for 
that time.)  But how did the switch get its compressed air?  Probably from a 
220 volt AC electric compressor located right at Bluff and run off the 4,000 
volt AC power line that the N&W had installed on its pole line not many years 
before.  There is still plenty of this equipment in service, even today.

But how about the track circuits through the tunnel?  Remember, we are 
talking about an age before the invention of the copper oxide rectifier (to trickle 
charge batteries)... the rectifier wasn't invented until around 1932.  And 
batteries for DC track circuits were primary batteries (not storage batteries) 
and had to be "made" locally by the signal maintainer from acid and zinc and 
copper, and didn't last very long.  Sooooo... I'll bet they used AC track 
circuits with vane relays between Cowan and Bluff.  Kinda state-of-the-art stuff in 
1914.  (I think the AC vane relay was developed for railroad work between 1906 
and 1910.)

And a mile-long AC track circuit was probably very difficult to "hold up" 
under soggy tunnel conditions, so there was probably at least one cut section, 
maybe more, located somewhere in the tunnel.

4.)  The pole line (for communications circuits, i.e. telegraph and 
telephone) went up-and-over-the-hill, in my time, and probably was in the same place 
ever since the "Low Grade" line was put in somewhere around 1898.  When Cowan 
was put in and began controlling the switch and signals at Bluff, obviously the 
wires for same were hung on the over-the-hill pole line.  I'll have to ponder 
about how many individual wires it would have taken to control two signals and 
one switch, and get indications back to the tower...

5.)  Wonder if Cowan represented the first installation of electro-pneumatic 
interlocking on the N&W, and if Bluff was the first instance of a "remotely 
controlled" interlocking?  (Don't give me no grief, Mister Bundy, about Cowan 
and Bluff being just "opposite ends" of the same interlocking ! )

6.)  And, you know, Cowan was constructed about the time lower quadrant (LQ) 
semaphores were being replaced with upper quadrant (UQ) semaphores.  Wonder 
how the installation of Cowan/Bluff factored into that transition? 

He who hath answers, let him speak up !

-- abram burnett,
               only a dabbler
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://six.pairlist.net/mailman/private/nw-mailing-list/attachments/20041111/f8d88c6e/attachment-0001.html