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Post by norbitonflyer on Dec 30, 2010 23:08:54 GMT
A suggestion appeared in today's "Rail" magazine that live rails should be converted to side or bottom contact to make them more snow proof. (It was particularly concerned with National Rail, but the same idea might also apply to the Underground). It was said in the article that the change could be introduced gradually, but I don't see how - surely no bottom-contact collection gear could be used anywhere where existing top-contact rail is present, or vice versa.
Whilst it might just be possible to change over a self-contained Underground line in a lengthy shutdown - as has been done before when the Central, Northern City, and W&C were converted to LT standard, this would surely not be practical for a complex network like the SSL or the Southern Region.
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Post by phillw48 on Dec 31, 2010 0:19:56 GMT
The most logical would be a conversion to overhead wire. This would be impracticable on the tube lines and in some other places such as the ELL's Thames Tunnel.
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Post by Deleted on Dec 31, 2010 0:37:36 GMT
In the New York area there is both top contact (Subway and ex PRR/LIRR lines) and bottom contact (ex NYC) third rail; and I believe at least some stock (locomotives, &c) is equipped to use both - whether this is by alternative, retractable shoes, or common, side mounted 'blade' ones I don't know. I would consider these last certainly a theoretical possibility: but would be dependant on it being possible to put a bottom contact third rail more or less where the current one is - and that I think is the difficult bit. So it may be that the projected change is possible, just that you can't start from where we are.
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Post by Deleted on Dec 31, 2010 9:04:24 GMT
I think this idea is a non-started as all the conductor rails would have to be replaced for this to work. With all the cost this would involve overhead catenary would be a better option. A dual system would be most cost effective with 3/4 rail retained in the tunnels with overhead catenary on surface sections. The MBTA Blue Line in Boston is configured like this en.wikipedia.org/wiki/Blue_Line_%28MBTA%29 and it works well. Xerces Fobe |
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Post by Deleted on Jan 1, 2011 17:58:54 GMT
In the NYC area, I think the only stock that operated on both top-contact and bottom contact lines were the FL9 dual-mode diesels. They had retractable shoes, but I don't know if they could switch between top-contact and bottom-contact on the fly. Currently there isn't any stock capable of using both. There have, however, been proposals for the M-8 MUs to have this capability to run trains from New Haven to NY Penn, but apparently the equipment to do sowould be heavy and complex, so it was not installed in the trains to begin with. In any case, bottom contact would only work for the third rail, not the fourth rail, and switching LUL from four-rail to three-rail would be such a massive undertaking that it can't possibly be worth it.
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Post by Deleted on Jan 1, 2011 18:17:49 GMT
Switching from 4 rail to 3 rail isn't really workable in the tunnels, you'd still need some sort of middle rail, even just for a return path, and signalling would need to be completely redone everywhere.
It's not at all worth doing.
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Post by Deleted on Jan 1, 2011 18:36:31 GMT
I've read that, bought Rail yesterday... Interesting, just how much will all that cost? what about items that get wedged between the juice rail and running rail, bits of ballast say, or cans, animals that stray onto the track?
I'm sure Manchester - Bury pre Metrolink has problems, but that was at 1,200v DC, was it not?
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Post by Deleted on Jan 1, 2011 19:30:19 GMT
In the NYC area, I think the only stock that operated on both top-contact and bottom contact lines were the FL9 dual-mode diesels. They had retractable shoes, but I don't know if they could switch between top-contact and bottom-contact on the fly. I have forwarded this question to an expert on this topic that I know....results shortly. |
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Post by Dmitri on Jan 1, 2011 19:52:42 GMT
xUSSR metros use 3-rail setup with great success. However, conversion cost would be enormous, so I'm afraid it is a non-starter.
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Post by metrailway on Jan 1, 2011 20:18:45 GMT
The most logical would be a conversion to overhead wire. I agree and so does the DfT as all new 3rd rail EMUs are built so a pantograph can be fitted easily if/when overhead conversion happens |
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Post by norbitonflyer on Jan 1, 2011 23:12:00 GMT
I agree and so does the DfT as all new 3rd rail EMUs are built so a pantograph can be fitted easily if/when overhead conversion happens That's not why they are so fitted - it's to make them suitable for conversion if the current lessor has no further use for them and they find a new home in ac territory - or for new services such as Southern's services via the WLL. I believe many ac units could also be converted to dc, but it is less obvious on those. (LM recently loaned some 350s for Southern's West London service for a while to cover a shortage in stock on Thameslink - I can'r recall whether these already had shoegear) |
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Post by andypurk on Jan 1, 2011 23:37:19 GMT
I agree and so does the DfT as all new 3rd rail EMUs are built so a pantograph can be fitted easily if/when overhead conversion happens That's not why they are so fitted - it's to make them suitable for conversion if the current lessor has no further use for them and they find a new home in ac territory - or for new services such as Southern's services via the WLL. I believe many ac units could also be converted to dc, but it is less obvious on those. (LM recently loaned some 350s for Southern's West London service for a while to cover a shortage in stock on Thameslink - I can'r recall whether these already had shoegear) The class 350/1 units were originally ordered as additional class 450s (3rd rail only) for South West Trains. The order was modified, well before delivery, into 30 dual voltage units for Silverlink / Central trains. They have spent most of their life as AC only units, with the shoe gear removed but stored. This shoe gear was refitted to around half of units, for the period in 2009 when they were on loan to Southern. The loan was due to late delivery of the class 377/5 units, meaning that Thameslink services had to borrow the dual voltage class 377/2 units from Southern. The later class 350/2 units were never fitted with shoegear. |
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Post by Deleted on Jan 2, 2011 16:42:34 GMT
Probably way too much info on FL-9s, but here is what my knowledgeable friend had to say.
Short answer: most probably not on the on-the fly-switching. Basically there was no overlap between the two electric systems to have a need.
Long answer: "I cannot answer for certain. But I would offer the following info in support of my GUESS that the answer is no.
The FL-9s were bought by the New Haven which ran them from their own lines into Grand Central Terminal where the third rail was underrunning only (bottom contact). Under the NH, trains going to Penn Sta always continued through on the PRR to DC and thus tended to be electrically powered from New Haven south. The FL-9s did not AFAIK operate for the New Haven into Penn Station as the NH lines leading there were A/C catenary only. The Long Island RR operated into Penn Station using 3rd rail of the overrunning type (top contact).
It is possible that under Penn Central the ex-NH FL-9s were fitted to run into Penn Station using the LIRR tracks but if they did they'd only use the top contact as -to the best of my knowledge- Penn Sta had no bottom contact 3rd rail and outside the tunnel the diesel would be used anyhow. So basically, in the past, whether the FL-9s ran into GCT (on bottom contact) or Penn Station via LIRR (top contact), in both cases they would encounter only one 3rd rail type, so switching between contact types wouldn't be necessary and as such would probably not have been provided for (as it probably would have beeen an extra-cost feature).
Now perhaps that changed when the 'West Side connection' allowed Amtrak trains (a few of which were powered by FL-9s) to run from the ex-NYC Hudson lines (top contact 3rd rail) into Penn Sta. (bottom contact 3rd rail) rather than GCT. But I doubt it as, once again, the engine could run on diesel until after it left the ex-NYC GCT approach tracks and thus shift to 3rd rail power only when it descended into the tunnel leading to Penn Sta.
So my best guess is that, as (AFAIK) there was never an instance where there was a NEED for an FL-9 to switch between top and bottom conttact 3rd rail 'on-the-fly', there was never a reason to build the capability to do so into the equipment. [based on the presumption that such capability would cost more and increase weight, complexity, and who knows what else]."
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Post by phillw48 on Jan 2, 2011 17:23:09 GMT
I recall seeing a photograph of one of the tunnels beneath the Hudson with a third rail suspended centrally from the roof. Could this be what was referred to as an under running third rail?
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Post by Deleted on Jan 2, 2011 18:29:22 GMT
I recall seeing a photograph of one of the tunnels beneath the Hudson with a third rail suspended centrally from the roof. Could this be what was referred to as an under running third rail? No - 'under running' third rail (bottom contact) is in more or less the standard position, but is inverted. There are a number of instances though where an overhead rail is or was used, rather than a wire, to meet specific requirements. What I think I was thinking about in relation to New York and dual top/bottom contact was the Amtrak Genesis locomotives, used on the 'West Side Connection' from ex NYC into Penn Station - but on investigating further there is certainly no connection between the two systems, and it appears that they only use third rail in the Penn Station area (top contact), working through the bottom contact area on diesel. |
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