Nostalgia & History > Signal Base On the NWP in Novato--But for What?

This is between Roblar Dr. and Hamilton Parkway, behind the Safeway/Old Nave Lanes property. The question is what was it for? Did the signalling system for the steam helper district extend all the way to Ignacio? How does a steam helper district work? Can the steam helper push or pull from either end of the train or does it have to be on the headend? 

There was also a signal base south of the Main Gate Rd. about 1/2 mile near the curve into the St. Vincent's area. 

This was all during the SMART construction. Obviously these are gone now I'm sure. . 

Wasn't the third rail zone signalled because of all of the passenger traffic?

My guess would be a power distribution signal case as there are no holes for cabling to be routed up/down through for the track circuits (like the old style semaphore/searchlight cases).



Edited 1 time(s). Last edit at 08/02/15 23:38 by Southern3205.

NWP employee timetable #16 of 1/1/1940 shows ABS between Sausalito and Ignacio. They didn't always run conduits up through the concrete foundations.

The Ignacio Depot and siding was less than a mile north of this location and the signal would would protect that area for sure. There was a head on wreck about a mile south of this location about the turn of the century or so. Can't remember the date, but it was one of the NWP's worst accident. ( I'll see if I can dig up info) Attached is a photo from my 2008 walk that shows a the same base close to the Marin Civic Center.
https://server15763.contentdm.oclc.org/cdm4/results.php?CISOOP1=any&CISOFIELD1=CISOSEARCHALL&CISOROOT=/p15763coll2&CISOBOX1=Petaluma:&CISOSORT=descri%7Cr&CISOSTART=1,181



Edited 1 time(s). Last edit at 08/03/15 12:06 by dmaffei.

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It was simple ABS, by itself, from San Rafael to Ignacio. I was told it was put in because of the war and Hamilton Field. Don't know if it was controlled by a dispatcher or just like ABS-Train Order, elsewhere

 The Interurban signal system was different because of the 3rd rail return . That took a special impedance bonds & Double-Element Vane Relays that would let the heavy current pass but separate the low signal voltage. Some AC and some DC. It had to be designed down to a "T"

A regular DC track circuit is simple to put in and maintain. Battery on one end, Pos & Neg run thru the rails that would hold up a relay at the other end., & insulated joints There are a 2 resistors thrown into the mix, a factor of leakage thru the ties and ballast. A train or car makes a short circuit, relay falls.

As far as cable, you can see where a space was chiseled out on the one corner, cable set and then cemented over. They didn't use conduit back then. The cables, boot legs, etc were just buried below the ballast.

The first foundation I remember was at the switch at the east switch at San Rafael. There was a larger one farther east before the tunnel.


Nudge



Edited 1 time(s). Last edit at 08/03/15 16:48 by spnudge.

A few aplifications and clarifications:

>It was simple ABS, by itself, from San Rafael to Ignacio. I was told it was put in because of the war and Hamilton Field. Don't know if it was controlled by a dispatcher or just like ABS-Train Order, elsewhere

By definition ABS isn't contolled by a dispatcher; that's what the A is for, "Automatic".

 >The Interurban signal system was different because of the 3rd rail return . That took a special impedance bonds & Double-Element Vane Relays that would let the heavy current pass but separate the low signal voltage. Some AC and some DC. It had to be designed down to a "T"

The only differences between the signals north of San Rafael and those used on the electrified district to the south was that interurban ones were unidirectional ABS-DT (unidrectional ABS), which just happened to use AC relays. The NWP signal installation was the first to use AC track circuits (1903), according to Harre Demoro, which were single rail using single element vane relays (next came the NYC subway/el -1904).

Single rail track circuits consume a lot of electrical power for what they do, so they may have been upgraded to double rail with impedance bonds and the two-element track relays you mention (there are still a lot of single-rail track circuits in the NYC subways, mostly on complicated swichwork). Even if this was done, I seriously doubt the AC line relays were changed.

>A regular DC track circuit is simple to put in and maintain. Battery on one end, Pos & Neg run thru the rails that would hold up a relay at the other end., & insulated joints

The same is true for AC track circuits; substitue "track transformer" for "track battery".

>There are a 2 resistors thrown into the mix, a factor of leakage thru the ties and ballast. A train or car makes a short circuit, relay falls.

The resistor at the feed end of a track circuit limits the current which flows the the track circuit to a safe value when it's occupied by a train, thus preventing the battery from melting or the transformer from frying. These usually have to be adjusted seasonally according to the moisture content of the ballast and ties. In addition, there are resistors connected to the windings in AC track relays for bringng the power factor closer to unity in order to cut down on wasted energy.