Now to address the "third rail in the street" question. Actually there was a third and fourth rail, not just a third.
London, Wasshignton DC, and Manhattan, NY, all had basically the same design of "conduit." The structure was based on what had already been designed for cable operation, a slot in the street about 40mm (1-5/8inch) wide with metal guiding rails on each side level with the pavement above a continuous trench or slot about 400mm (1 ft. 4in.) wide and about 1.2 meters (four feet) deep. About one third of the way down in this continuous trench were two rails, one on each side wall, supported from the wall on insulators. Extending down from the streetcar/tram. was a wood board called a plough. It was about 400mm long, along the length of the streetcar, and about 38mm, 1-1/2 inch wide. It had thin steel rubbing surfaces at the point where it passed through the slot in the street to minimize wear rubbing against the guidance rails. At the top forward and aft were what were something like a pair of small rollerscate wheels that allowed it to move side to side on forward and aft angles across the width of the car, at the center of the car body in London, and extending all the way to each side of the car, but located under the truck (bogie) bolster allowing movement almost to each side of the bolster in New York, but much more limited in movement in Washington, DC. On each side of the board or plough, at the height of the third and fouth rails projecting from the side walls of the conduit or trench, were the actual pickup shoes, sprung horzontally from the plough and contacting the third and fourth rails horzontally, not vertically. One rail was for positive dc power, the other for the ground return, much like the four rail system used in part of the Underground.
Most tram lines in London used both overhead wire and conduit. A the transition points, the conduit on both up and down tracks swerved from the center of the respective tracks, crossed under the inside running rails, with the slot interrupting the running rails, and merged into one common slot in the middle between the two tracks. An outbound car would coast through this area, the plow would coast off the side of the car, and stack up against other plows in the middle, with a last in first out ordering of plows. The Ploughman or Plowman would meet each inbound car and guide the first plow available to fit in the carrier at the side of the car, and the motion of the indbound car and the layout of the slot would insure the plow returned to the center and begin contact with the third and fourth rails. The plowman often was responsible for insuring the bow collector was raised to contact the overhead wire on the up car, but I believe the newer cars could do this electrically by control of the motorman/operator/tram driver.
Nearly all Washington DC and a few Bronx lines and one Queens line (and possibliy one Brooklyn line, but only for a very short time) that entered Manhattan also used both conduit and overhead wire. These were serviced by "Plowpits" (I visited the one on the Cabin John line in Washington and may have visited the one at Lenox Avenue and 145th Street in Manhattan.) These were rooms under the street, with enough height so man could work standing, and both conduits, inbound track and outbound entered this room, where the plow, hanging loosely from the car truck (bogie) carrier, would be removed from an outbound car and stacked, and plows fitted to the truck carrier on inbound cars.
London's conduit cars needed lots of side to side movement of the ploughs, both because of the system used at change to and from overhead wire, and also because of the location in the center of the car, where movement to one side was required on curves. The Manhattan car lines required considerable movement because there were a few locations where two competing systems shared the same track but used different conduits, with each of the two conduits to the side of the track centerline. In some cases in Manhattan competing systems did use the same conduit, and this was always the case in Washington where side to side movement just was needed to accomodate irregularities.
There was plenty of room below the third and fourth rails for snow and ice to accumulate and then run off as water into sewer drains when weather was warmer. The conduit lines operated about as reliably as the overhead wire lines, and a very severe ice storm could put either out of commission by ice buildup on the contact surfaces.
You are correct. The Manahttan elevateds used the closer in and higher third rail that allowed gravety shoes carried close to the truck frame like Chicago uses today. The BMT elevateds were the same. This meant that often there were two third rails, one a each side of the track, on the Bronx and Queens and Brooklyn elevated structures used by both el and subway trains. But this was only for current carrying capacity, because all the classic (pre-WWII) BMT and IRT subway cars had shoes that could pivot quite high and and inner rubbing surface that would slide along the elevated third rail. This type of pickup shoe has not been used for years. The IRT and BMT had tiny differences that did not prevent IRT cars from running quite well on BMT lines. Not visa versa because of clearance problems, the BMT subway cars being larger and especially wider. The City-owned Independent or IND system used the BMT standards in all respects, but did not use the pivoting third rail shoes, and the elevated third rail was removed on all Brooklyn and Queens lines before IND type equipment began operating. (the IND and BMT have been combined into the "B Division" and many current routes embody lines that were part of both systems. This was first about 1949 with the extension of the "D" over the Culver Line to Coney Island, and then in 1967 in a big way with the Chrystie Street Connection in Manhattan with the rerouting of many routes to best serve the public using combinations.) The Pennsylvania Railroads New YOrk Terminal electrification and the Long Island Railroad used BMT subway standards exactly. Or really the other way around! New Ylrk City subway cars are tested for high speed regularly on LIRR tracks. And all this in New York is nominally 600 or 650V DC. 750V is used on newer systems. And PATH also uses the BMT-LIRR standard third rail and voltage.
Having been to England and seen the Southern electrification, the subway overrunning third rail in the USA is not much different, except the cover boards are almost always used iwith "C-brackets" on the side away from the running rail. (I recall the Southern as being without cover boards!) These boards were wood, are now plastic. The elevated third rails did not have protection, except that there was usualy a wooden wood board away from running rail up to the running siruface of the third rail to prevent accidently moving one's foot horizontally to the third rail.
just to add my 2 cents worth, i believe NYC's Third Ave. El (and thus probably the Sixth and Ninth Ave. lines too) used a vertical shoe like Chicago's. I recall the guard board (wood) stood up vertically alongside the third rail. Big Duke/Arturo
I remember, in winters in the '50s, seeing New York Central flangers run on the Harlem Division. They had blowers to clean out beneath the under-running third rails. Stand back!!! In later years, the wooden three-piece coverings gave way to the current plastic caps, as seen on Metro-North today.
Question: most of the New York City trolleys ran on a center third-rail, under the track. How did they keep those clean, of ice and snow? Was the pick-up shoe down- or up-bearing? How did they extract the shoe, if one broke off? Could they, on occasion, energize the center slot steel guideway, if something went awry? Me, I'd rather see trolley poles, like we had in Westchester County. A few of the ornate wrought-iron (?) support poles, with appropriate filial, still exist, all over the county, supporting other 'thingies'. They were rather unique.
Bill
pajrr ...NYC used under running because it is less prone to icing up in winter time, since the pick up surface is the bottom of the rail, protected from ice and snow.
...NYC used under running because it is less prone to icing up in winter time, since the pick up surface is the bottom of the rail, protected from ice and snow.
That was one important reason. Another was that it was considered safer because the top of the 3rd rail was covered. If you fell against that wooden cover, you were a lot less likely to light up the neighborhood than if you fell against an exposed 3rd rail.
ChuckAllen, TX
jeremygharrison A query from England - what is the position of the third rail (in terms of distance from the running rail, and height above it) on the New York and Chicago Rapid Transit (Subway/El) systems? Are they the same? Do other systems use the same standard, or does each have its own?
A query from England - what is the position of the third rail (in terms of distance from the running rail, and height above it) on the New York and Chicago Rapid Transit (Subway/El) systems?
Are they the same? Do other systems use the same standard, or does each have its own?
No, the Chicago and New York dimensions are different. However, all other overrunning systems have dimensions similar to those of New York. There may be slight variations but they're all pretty close. The big difference is that Chicago is unique in not having a cover board, and their third rail shoe drops straight down onto the top of the third rail. All other overrunning systems have a cover board and the shoe cantilevers out and is spring loaded.
By the way, there is one other underrunning line - the SEPTA Market-Frankford line uses underrunning third rail. Interestingly, the Broad Street line is overrunning! (The City built it to BMT standards.)
Dave Phelps
I don't know about the distance from the running rails, but in terms of the pick ups themselves, there are 2 types----Over running and Under running. With over running the rail sits like a regular rail and the 3rd rail shoe sits on top. On an under running rail, the 3rd rail hangs upside down, supported from the top and the 3rd rail shoe runs along the bottom of the rail. The PRR (in Penn Station), the Long Island RR , and NY City Subway system use over running 3rd rail. The old New York Central Lines use the under running system. I think that NYC used under running because it is less prone to icing up in winter time, since the pick up surface is the bottom of the rail, protected from ice and snow.
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