Unusual "catenary"

[velotrain]

In my investigation of the NYC elevated lines of the early 20th century I came across this 1909 image of the Brooklyn bridge looking west towards Manhattan.  The upper level is shared by subway and streetcars, while the lower is allocated to more streetcars and horses.

 

While not being able to see what is used below, I was taken by the apparently over-engineered catenary used on the second level.  I could be mistaken, but it looks as though the cable is installed inside a trough.  I'm wondering if that is due to an attempt to reduce/eliminate traffic backups caused by trolley poles jumping off the cable on the older line below?  Perhaps having a guaranteed consistent height helps with that, or some other operational concern?  Other interpretations are welcome, and I'm also curious about the extra-robust support system for the catenary.

 

https://s-media-cache-ak0.pinimg.com/736x/a7/e9/fd/a7e9fdfc726001124c3e9982502bcde9.jpg

 

 

At first I was a bit suspicious of the background, skeptical that the Manhattan skyline would be that built up as early as 1909.  However, the changes in the bridge itself, and the increase in the traffic density for all modes, suggest the hectic pace of development in the city, as indicated by this view from a scant six years earlier.

 

http://42mzqz26jebqf6rd034t5pef-wpengine.netdna-ssl.com/wp-content/uploads/2012/08/bk_bridge_expansion_03.jpg

[Kiha66]

Could be an electrified overhead rail used as cantenary, I believe the New York Central around this time used a similar system on their third rail networks for bridging the more complicated track-work arrangements where large gaps in the third rail would be.  Some of the very early NYC electrics have tiny pantagraphs for this purpose. 

[velotrain]

I know it's being used as catenary as I can see the trolley poles riding in it.

 

I'm just asking why it looks like this?

 

If you look at the subway tracks here, they are indeed using third rail.

[Wonderbolt]

Maybe the design is more rubust in wind and storms at such a high level?

Edited June 20, 2017 by Wonderbolt

[Kiha66]

Perhaps it is normal wire, and the trough is to keep the pole on the wire so that it doesn't slip and short to the metal bridge truss work.  I'd guess all the supporting lattice work is due to the weak steel used in the late 1800's, and the relatively tight curves in the wire.  The Brooklyn trolleys couldn't use third rail as they did a lot of street running as I understand.

http://www.subchat.com/readflat.asp?Id=1189083

[kvp]

Actually this supporting frame is still used for trolleybus operation under bridges in Hungary. The wooden (or lately plastic) upside down U shaped cover is used as both a trolley wire guide and isolation, so the wire could almost touch the supporting beam and is separated only by this cover and suspended on very short, almost just trolley shoe high isolators. The whole thing is then screwed onto the bottom of the supporting structure.

 

(This suspension method also allows the use of an overhead 3rd rail, which is just a strip of metal fixed onto the bottom of the cover. This has the added benefit of zero horizonal and vertical play, but is only used for longer runs in tunnels.)

 

The cable under a wooden cover method on google streetview from the closest underpass from my workplace:

 

https://www.google.hu/maps/@47.5179106,19.0732573,3a,75y,319.96h,94.78t/data=!3m6!1e1!3m4!1s74neKkSKAVoFXO_Tmm_Clw!2e0!7i13312!8i6656?hl=en

[velotrain]

 

(This suspension method also allows the use of an overhead 3rd rail, which is just a strip of metal fixed onto the bottom of the cover. This has the added benefit of zero horizonal and vertical play, but is only used for longer runs in tunnels.)

 

If it's functioning as a trolley wire, there's no need for a third rail?

[kvp]

If it's functioning as a trolley wire, there's no need for a third rail?

Yes, overhead third rail is actually a type of power rail. Its thin strip variant is usable with trolley shoes and the classic thick upside down mounted rail variant has been used in tunnels for centuries (actually at least since 1896). The early pantograph for this system consisted of a copper/graphite covered wooden collector beam, lifted vertically by two spring loaded arms on its two ends. Modern variants are actually just small pantographs with upside down 3rd rail shoes like on the NYC S-motors or normal mini pantographs that could also be used with overhead wires once out of the tunnel.

 

NYC S-motor with the small top shoes: https://en.wikipedia.org/wiki/File:AlcoGEClassS1.JPG

Some pictures here: http://hampage.hu/trams/fav6/

Especially this one with the 19th century heritage car and the overhead 3rd rail: http://hampage.hu/trams/fav4/09200076.jpg

[Suica]

Could be similar to the system used at Berlin Hauptbahnhof today. An overhead rail containing a copper strip.

 

http://www.bahnbilder.de/bilder/76541.jpg

http://www.bahnbilder.de/bilder/58577.jpg

 

If I remember correctly this system comes from Switzerland and was initially used in avalanche-prone regions.

Similarly, this could be a reason why it was picked for the Brooklyn Bridge? Strong winds, rain, etc?

These days it's used in tunnels as it requires less space.

[kvp]

Could be similar to the system used at Berlin Hauptbahnhof today. An overhead rail containing a copper strip.

 

http://www.bahnbilder.de/bilder/76541.jpg

http://www.bahnbilder.de/bilder/58577.jpg

 

If I remember correctly this system comes from Switzerland and was initially used in avalanche-prone regions.

Similarly, this could be a reason why it was picked for the Brooklyn Bridge? Strong winds, rain, etc?

These days it's used in tunnels as it requires less space.

The reasons are clearence in tunnels and under overpasses and the other is rigidity, which means the wires could move around under the pressure of the collectors (pantographs or poles), so they could get dangerously close to metal structural elements. The upside down U enclosed wire solution and the thin tall strip variant is good for trolley poles so they could hug it, while the upside down flat rail and its modern copper insert variant is good for pantographs that could move side to side under it.

 

Afaik the original inventor of the system was the Siemens company, which also supplied the traction equipment for the Budapest underground and the early tram network that was using subsurface (conduit) 3rd and 4th rails. After the invention of the bow collector in the late 1880s (also from Siemens) the trams were finally switched to overhead wires and the underground got this hybrid overhead 3rd rail in the tunnel, wires on the surface system it is using to this day.