Discussion relating to the past and present operations of the NYC Subway, PATH, and Staten Island Railway (SIRT).

Moderator: GirlOnTheTrain

  by train2
Within the US on the heavy rail system (ie. US Class 1's regionals, etc.) the use of armstrong (rods and pipelines) interlocking towers are about to be a thing of the past. Sometime during the last 10-15 years when I was riding transit systems such as MTA and Chicago's CTA I have vague memories of some armstrong interlockings. I did not take photos and notes so I can't remember locations or even the exact transit system.

So I am going to post this message here and other boards that deal with CTA (as CTA is likely the other tranist system I am thinking of) to see if any armstrong interlockings still exist? If they do not how recently did they exist? And if some are still in place how in danger are they of being replaced?

If you are aware of any other transit systems that have these interlockings please offer that info as well.
  by gasaxe
There were some at one time, but they all disappeared.

Because the TA is actually a conglomeration of different, existing, transit systems and railroads that were built over the span of MANY years and not a monolithic system built in one shot, there were many armstrongs left over from when steam locos ran on rails that are now used by subway trains.
  by pc motorman
Only had manual machines with pull levers ( last I knew of was Roosevelt Ave. on the E/F)
or or manual twist (side to side levers) in Jamaica YArd.
All gone now in favor of push button. electric.
Local towers are being eliminated in favor of central control points. (master towers)
Latest BS in electronic control being installed at 59 st Manhatten. They can control signals and switches with a computor.
  by DaveBarraza
There are about 30 mechanical POWER interlockings left on the system, although the number is dwindling. The last "Armstrong" was Canarsie which was taken out of service due to a mysterious fire in the 60's or 70's.

Off the top of my head:
The Concourse line contract replaced 161st, 167th, Tremont, Fordham, Bedford Park, and Perry Ave.
Canal Chambers and Hudson will be replaced on the 8th avenue line this year.
East 180, 4th Ave/Culver, 5th/53rd, Lex/53rd are all in service but will be replaced in the next few years.

This leaves 239th yard LL, 207th Yard A, 207th Yard B, 42nd/8th North, 30th/8th, Hoyt, Lafayette, Utica, East NY, 34th/6th, West 4th, York, Jay, Church, Kings Highway/Culver, Concourse Yard, Roosevelt, 71st/Continental, Jamaica Yard, Union Turnpike, Parsons Hillside, Nassau, Bedford/Nostrand, and Court as the operating mechanical POWER interlockings. Hmm - does that add up to 30?
  by DaveBarraza
Purely mechanical interlockings use the effort of the towerman to move points and clear signals. The have long floor mounted levers to achieve a mechanical advantage for the operator. Some electrical apparatus was installed on purely mechanical plants which survived into the era of track circuits.

Power mechanical interlockings use electricity or air pressure to actuate the switches and signals, and thus have smaller levers which usually throw about 5". Power interlockings were usually supplemented by relay networks to some extent to interface with the field elements, but the relays' electrical checks relied upon the mechanical locking to perform its own vital role. I worked on some GRS Model 2 interlockers which were installed around 1915 and for a 16 lever machine there were 9 relays in the room, and each signal in the field had 1 or 2 relays depending on the number of aspects.

Both types have mechanical interlocking to ensure that the levers are moved in a predetermined order, which differentiates them from all-relay interlockings in which the control machine is considered non-vital.