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Old May 10th, 2008, 01:45 AM   #2521
Tubeman
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Originally Posted by Martin S View Post
On this subject of electrification, I recently went to the Covent Garden Transport Museum and was mystified by one of the exhibits. It was a glass floor with a representation of the four rails of the tube lines, which lit up if you stood on a rail that was electrified. All four rails apparently could electrocute people who were to come in contact with them.

That seemed strange to me. The outer rail I understand is the high voltage conductor, the centre rail the return conductor and the two running rails I would have thought would have been at the same potential as the train so that anyone coming in contact with the metalwork of the train could therefore become electrocuted. Perhaps the intention of the exhibit was to warn people against trespassing on the railway.

In a third rail system, such as is used in the London area and on Merseyrail, the conductor rail is at 750v and the running rails, which are the return conductors, are ostensibly at earth potential. However, as there is not a clear path to earth from the running rails, leakage can occur through metallic objects such as the cast-iron lining of a tunnel, or signalling equipment, which can promote corrosion or signalling problems. The idea of the fourth rail is that it will act as a return conductor by being at a potential significantly below local earth potential so that it is the natural path for the return current.

Have to say though that before I knew much about how these trains operated, the four rails on the London Underground always fascinated me. I used to wonder which rails the trains actually ran on or whether they had four sets of wheels that ran on each rail.
There are small 5-10V currents running through the 'Running' (i.e. lower and not resting on insulating pots) rails, associated with signalling circuits. Technically therefore all 4 rails are 'live' to a point, but the Running rails have nothing to do with Traction current return, this would frazzle the signalling circuits.

PS I'm back from Vietnam
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Old May 10th, 2008, 04:38 AM   #2522
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i am amazed how london is changed and is changing its really cool to see that happening.

St Pancras Station looks marvelous and it will be even more grander when the five star hotel opens and also the domestic HSR will open.

i like the thameslink St Pancras Station it looks like airport station even the annoucements look like an airport.

the East London line is going to be the East London Railway from a little stub to a more functional regional Rail line.

also the opening of Terminal 5 which is awesome oh man such exciting times for the UK also Endiberth is having a Tram network as well.

Tubeman how was your trip to Vietnam i have a fear of flying though.
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Old May 10th, 2008, 08:20 AM   #2523
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I think you mean Edinburgh

Vietnam was ace... If anything will cure you of a fear of flying it's Vietnam's roads... you're glad to get on a plane.
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Old May 10th, 2008, 02:41 PM   #2524
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Old 1967 stock on the Victoria line

Hi Tubeman

Any idea what will happen to the old 1967 stock on the Victoria line when it is replaced by 2009 stock?

James
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Old May 10th, 2008, 05:23 PM   #2525
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Quote:
Originally Posted by Acemcbuller View Post
Hi Tubeman

Any idea what will happen to the old 1967 stock on the Victoria line when it is replaced by 2009 stock?

James
Possibly moved to the Bakerloo to allow it to be extended to Watford Junction.
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Old May 10th, 2008, 07:08 PM   #2526
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Welcome back Tubeman, did you go to North or South Vietnam...?
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Old May 11th, 2008, 10:44 AM   #2527
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Originally Posted by sweek View Post
Possibly moved to the Bakerloo to allow it to be extended to Watford Junction.
Sadly this won't be happening: it is not deemed cost-beneficial to spend the money converting the '67 Stock for Manual operation for what might only be 8 years use on the Bakerloo. At best the '67 stocks will simply be cannibalised as a supply of parts for the '72 MkI Stock.
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Old May 11th, 2008, 10:57 AM   #2528
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Welcome back Tubeman, did you go to North or South Vietnam...?
Both

Started in the south and worked northwards

4 nights Ho Chi Minh (Saigon) including trips to the Mekong Delta and Chu Chi (Viet Cong tunnels)

Flew HCM > Da Lat

1 night Da Lat

Drove Da Lat > Nha Trang

2 nights Nha Trang

Flew Nha Trang > Da Nang

2 nights Hoi An

Drove Hoi An > Hue

1 night Hue

Flew Hue > Hanoi

3 nights Hanoi including trip to Ha Long Bay

Flew Hanoi > Da Nang

4 more nights Hoi An at a resort

It's a magnificent country, really varied. The starkest illustration was probably the drive from Da Lat to Nha Trang, Da Lat nestles on a tranquil lake 1,000m up surrounded by pine forests and 3 hours later we were on a stunning palm-fringed beach via some of the most spectacular mountain passes I've been through, with about a 10C difference in temperature. Saigon and Hanoi are great, buzzing cities with some beautiful architecture and parks and the ancient city of Hue is stunning as is the old town of Hoi An.

A hearty Tubeman thumbs-up

If you go, set aside 2 weeks for touring if you want to see the country anywhere close to properly. There are some fantastic resorts for R&R too, we stayed at the Nam Hai, Hoi An:






Each villa has its own pool out front overlooking the beach
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Old May 11th, 2008, 04:20 PM   #2529
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I was about to ask what it was like visting a communist country, then I realised that was North Korea

It looks like you had a great time, though!
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Old May 11th, 2008, 04:38 PM   #2530
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Quote:
Originally Posted by iampuking View Post
I was about to ask what it was like visting a communist country, then I realised that was North Korea

It looks like you had a great time, though!
Vietnam is a communist country. Nominally at least. Also there is no north Vietnam/South Vietnam any more, there's just Vietnam.
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Old May 13th, 2008, 12:53 AM   #2531
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Just a question or two about the Bakerloo line.

I know there is plan to extend it once again to watford.

1. Why did they decide to alter the terminus to Harrow and Wealdstone? was it just a money thing??

2. Are the plans firmed up to renew the link to watford, do they plan on it being sometime soon??

My finally question is one regarding the proposed Camberwell Extension, this has been on the drawing board now for almost 80 years and yet nothing much has been done about it, people talk about it yet as far as I'm aware this isn't even on TfL 2025 agenda.

Do you feel it is a viable extension or just one of those things that is always taked about but never actioned - a little like CrossRail used to be?

Glad to hear you enjoyed Vietnam - its a beautiful part of the world. Loved it when i went a few years ago and would love to go back and see more.
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Old May 13th, 2008, 03:01 PM   #2532
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Quote:
Originally Posted by iampuking View Post
Great, now that i've got your essay writing in tune could you explain to all of us why AirTrack is not allowed to have three rail electrification despite the fact that it'll be using 21st century technology (probably with concrete tunnels), and full size loading guage? No malice intended.
Someone said earlier (somewhere) that overhead ac systems ground to earth, through the rails, which are earthed, but on 750v DC southern system the rails are connected back to the substation to earth? Possibly a rectification design issue? IF that is the case, and I have absolutely nothing but a vague idea that it is, then it wouldn't be possible to have the same earth for both systems. that would also mean that at existing changeover sections like Farringdon they are isolated from the normal circuits, and earth in a specific way, indeed the 3rd rail could be rectified from the overhead ac power source and not have the earth conflict.
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Old May 14th, 2008, 12:47 AM   #2533
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Originally Posted by zfreeman View Post
Just a question or two about the Bakerloo line.

I know there is plan to extend it once again to watford.

1. Why did they decide to alter the terminus to Harrow and Wealdstone? was it just a money thing??

2. Are the plans firmed up to renew the link to watford, do they plan on it being sometime soon??

My finally question is one regarding the proposed Camberwell Extension, this has been on the drawing board now for almost 80 years and yet nothing much has been done about it, people talk about it yet as far as I'm aware this isn't even on TfL 2025 agenda.

Do you feel it is a viable extension or just one of those things that is always taked about but never actioned - a little like CrossRail used to be?

Glad to hear you enjoyed Vietnam - its a beautiful part of the world. Loved it when i went a few years ago and would love to go back and see more.
The Bakerloo was cut back from Watford Jcn to Stonebridge Park in 1982 really due to lack of patronage, and the only reason Stonebridge Park and not Queen's Park was that the main Bakerloo Depot is there so some trains ran beyond Queen's Park out of necessity.

A raft of service cut-backs across LT were introduced as an economy in 1982, and this meant that the depot at Croxley Green (shared by BR and the Bakerloo Line, uniquely) was able to close and therefore there was no point maintaining any service beyond Stonebridge park.

The cut-back prompted sufficient complaints from passengers to prompt re-extension beyond Stonebridge park in 1984, but Harrow & Wealdstone was deemed the most cost-beneficial terminus as stations north are lightly used serving low-density 1930's suburbs, and no-one realistically would use the Bakerloo to get into London from Watford when fast BR trains are available.

The only thing stopping the Watford re-extension is rolling stock: the Bakerloo hasn't enough. I have already discussed before that the idea of converting retired Victoria Line 1967 stock has been dismissed as too costly. Maybe the Piccadilly 1973 stock could be cascaded to the Bakerloo, but this is deemed life-expired and might have tunnel clearance issues being 6 longer cars rather than 7 shorter cars. The logic is to withdraw entirely the slow Watford-Euston BR service, and have a stub of the NLL serving the two stations left out (South Hampstead and Kilburn High Rd), terminating at Queen's Park.

This segregates the Bakerloo Line and BR services, increasing reliability and giving a better service north of Queen's park.

There is a southern extension on the drawing board with a delivery date of 2025 mooted. I doubt it will ever materialise, certainly not by then. It would serve Camberwell, Peckham, Nunhead, Brockley and Lewisham before taking over the Hayes BR branch via Ladywell, Catford etc.
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Old May 17th, 2008, 10:49 AM   #2534
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Quote:
Originally Posted by elfabyanos View Post
Someone said earlier (somewhere) that overhead ac systems ground to earth, through the rails, which are earthed, but on 750v DC southern system the rails are connected back to the substation to earth? Possibly a rectification design issue? IF that is the case, and I have absolutely nothing but a vague idea that it is, then it wouldn't be possible to have the same earth for both systems. that would also mean that at existing changeover sections like Farringdon they are isolated from the normal circuits, and earth in a specific way, indeed the 3rd rail could be rectified from the overhead ac power source and not have the earth conflict.
It's still baffling as much of the North London Line was dual 25Kv AC / 750V DC electrified for many years so I am confused how the current return would happen.

I know that on 'normal' 25Kv AC OLE track there are earth bonds from the running rail into the ground every so often (painted bright red, so you know not to touch them), but I don't know how it works if the 3rd Rail DC and OLE AC returns are both being fed back to the same runing rail.

3rd Rail systems definitely do return to the substation via a running rail, as on the East Putney - Wimbledon section of the District Line the Middle 4th 'Negative' rail is just a dummy bonded to the runnning rail to allow LU 4th rail trains to run over 3rd rail electirified track (fed from Raynes Park NR substation).
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Old May 19th, 2008, 08:20 PM   #2535
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I'm not 100% sure of this but the traction return on a 25kV OLE network is via the return conductor which is a cable normally slung along the backs of the masts and with an electrical potential of around 3000v. This is sometimes insulated where it would be within touching distance.

Current return is via the red bonds that run to the return conductor from the running rail. At intervals, there are booster transformers which maintain the voltage in the return conductor. As the voltage in the conductor is well above (or below) earth potential, stray currents are prevented.
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Old May 25th, 2008, 03:09 AM   #2536
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Door Closing Noises

Hi, My first post here and I apologize if what I ask has been answered before, I haven't had time to run though the many pages of this thread. If there are answers, please direct me to them.

First, on my two total trips to London, I really liked the "chirping" noises that went with the doors closing, on all different lines, though I liked the D78 Stock and the 1995/1996 TS ones the best. I was wondering, where did these originate and how did they come into use. Is there somewhere that I can find all the beeping chimes? Oh, and I also liked some of the "door opening" chimes that work too.

Secondly, would the interchage between Jubilee and Piccadilly Lines at Green Park be a Hassle on a Monday at around 2 or 3 in the afternoon for tourists toting some luggage heading for Heathrow? Would it be better to take the Met line up away from Central London and then change for a Piccadilly line heading back down to Heathrow after an interchange at Acton Town? (Originating at Finchley Road)

Also, any tips for a Heathrow Terminals 1-2-3 to North Acton trip on a weekday with luggage around 12? I was thinking of taking the Piccadilly to Acton Town, a District to Ealing Bdy and then the Central back to North Acton.

Many Thanks
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Old May 25th, 2008, 10:42 AM   #2537
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Originally Posted by MoritzCH View Post
Secondly, would the interchage between Jubilee and Piccadilly Lines at Green Park be a Hassle on a Monday at around 2 or 3 in the afternoon for tourists toting some luggage heading for Heathrow? Would it be better to take the Met line up away from Central London and then change for a Piccadilly line heading back down to Heathrow after an interchange at Acton Town? (Originating at Finchley Road)
You're not likely to encounter abnormally large crowds at Green Park there are lifts to get between those two lines, but note it's still a long level walk between them. I don't think going via Rayner's Lane is necessary.
Quote:
Also, any tips for a Heathrow Terminals 1-2-3 to North Acton trip on a weekday with luggage around 12? I was thinking of taking the Piccadilly to Acton Town, a District to Ealing Bdy and then the Central back to North Acton.
Heathrow Connect direct to Ealing Broadway might be the best option since it's a much more direct journey with level interchange at EB. You have to buy a separate ticket (about £5 per person single) since tube tickets, Oyster and Travelcards aren't valid. The trains are only every 30 minutes.

Your plan means going over the footbridge at Acton Town. They are installing lifts right now, but they won't be working until towards the end of the year.
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Old May 25th, 2008, 11:01 AM   #2538
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Quote:
Originally Posted by Martin S View Post
I'm not 100% sure of this but the traction return on a 25kV OLE network is via the return conductor which is a cable normally slung along the backs of the masts and with an electrical potential of around 3000v. This is sometimes insulated where it would be within touching distance.
No, in AC overhead systems the current return is via the track. Because it's AC, you don't need to worry about stray currents in the same way, since it doesn't have the same corroding effect as DC.

I think the wire on the back of the posts is the third wire of the three phase supply (power companies usually supply high voltage AC as three phase), and they swap over which is used as the overhead line to balance out the use of the phases.
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Old May 25th, 2008, 11:10 AM   #2539
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Quote:
Originally Posted by MoritzCH View Post
Hi, My first post here and I apologize if what I ask has been answered before, I haven't had time to run though the many pages of this thread. If there are answers, please direct me to them.

First, on my two total trips to London, I really liked the "chirping" noises that went with the doors closing, on all different lines, though I liked the D78 Stock and the 1995/1996 TS ones the best. I was wondering, where did these originate and how did they come into use. Is there somewhere that I can find all the beeping chimes? Oh, and I also liked some of the "door opening" chimes that work too.

Secondly, would the interchage between Jubilee and Piccadilly Lines at Green Park be a Hassle on a Monday at around 2 or 3 in the afternoon for tourists toting some luggage heading for Heathrow? Would it be better to take the Met line up away from Central London and then change for a Piccadilly line heading back down to Heathrow after an interchange at Acton Town? (Originating at Finchley Road)

Also, any tips for a Heathrow Terminals 1-2-3 to North Acton trip on a weekday with luggage around 12? I was thinking of taking the Piccadilly to Acton Town, a District to Ealing Bdy and then the Central back to North Acton.

Many Thanks
Welcome to ssc

Stick with U Thant's advice!

Regarding door chimes, they are motivated by catering for VIP's (as in Visually Impaired People), this is also why the doors are all red contrasting against the mostly white car bodies. They were first introduced with the first refurbishments (C Stock 1990-1994), the first stock to have them from delivery was the Central Line 1992 Stock (1993 onwards). The last stock to have them were the District D Stock, which were only fully refurbished last year.

In addition to door close chimes, the 1995, 1996 (Northern / Jubilee) and D Stock refurb also have door open alerts.

I don't know if they can be accessed online, but there are sites with general Tube noise clips so they're probably out there somewhere.
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Old May 25th, 2008, 03:16 PM   #2540
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No, in AC overhead systems the current return is via the track. Because it's AC, you don't need to worry about stray currents in the same way, since it doesn't have the same corroding effect as DC.

I think the wire on the back of the posts is the third wire of the three phase supply (power companies usually supply high voltage AC as three phase), and they swap over which is used as the overhead line to balance out the use of the phases.

Whilst I admit that my knowledge of electrical power systems is pretty sketchy, I don't think that is correct. Certainly the cable slung at the back of the masts is always referred to as the return conductor. For it to be an alternative power cable, it would have to be at a potential of 25kV and the return conductor is certainly not at that potential (as evidenced by the short insulator pots that it is suspended on).

Whilst the corrosive effect of D.C. may not be present, stray AC currents can interfere with signalling systems, which is one reason why expensive immunisation is required as a precursor to electrification.
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