Trackside cables

[ess]

Alongside tube tracks there are many cables in racks, usually neat but also ugly. You don’t see this in BR tracks. Do tube trains need more cabling or is it just hidden?

 

[Ralph Ayres]

Main line cables tend to be in trackside troughs, neater but arguably more vulnerable to damage and less accessible for running new cables or replacing old ones.

 

[John Webb]

All cables associated with tube lines obviously have to be carried within the tunnel. These include signalling, communication and power supply - both traction and lighting etc. By putting them at the side of the tunnel they are easily available for installation and maintenance/replacement.
On surface lines, because the cables are at ground level, they are not so obvious to passengers, unlike the old telegraph posts and wires once familiar alongside railway lines.

 

[swt_passenger]

All cables associated with tube lines obviously have to be carried within the tunnel. These include signalling, communication and power supply - both traction and lighting etc. By putting them at the side of the tunnel they are easily available for installation and maintenance/replacement.
On surface lines, because the cables are at ground level, they are not so obvious to passengers, unlike the old telegraph posts and wires once familiar alongside railway lines.

I think the question was possibly also about the wider ‘tube’ network, outside the tunnels, where LU still tend to use their typical higher level brackets. I think they also have many areas with a continuous air supply with pipes carried on the same support system. I suppose it’s likely they continued what started underground for standardisation, but it’s also possible some of their formations are a lot narrower.

 

[Ken H]

How much cabling is needed nowadays. A fibre optic can carry tons of data so can connect up most kit. OK point machines use a lot of juice, but LED signalling must use very little. so any power cables could be smaller

 

[bionic]

Do the trainstops need air pressure?

 

[Ken H]

Do the trainstops need air pressure?

used to be pneumatic. dont know if they have gone electric. How many lines have them still? must be redundant with ATO. Vic line never had them

 

[bionic]

Bakerloo, Piccadilly, District, Met and Circle still have them.

used to be pneumatic. dont know if they have gone electric. How many lines have them still? must be redundant with ATO. Vic line never had them

 

[John Webb]

How much cabling is needed nowadays. A fibre optic can carry tons of data so can connect up most kit. OK point machines use a lot of juice, but LED signalling must use very little. so any power cables could be smaller

True, but I suspect the cost of deliberately changing over to Fibre Optics and lighter cables would far outweigh any savings; best wait until a cable has to be replaced? And with all the supports there and available I don't suppose they need to look at alternatives.

 

[Ken H]

True, but I suspect the cost of deliberately changing over to Fibre Optics and lighter cables would far outweigh any savings; best wait until a cable has to be replaced? And with all the supports there and available I don't suppose they need to look at alternatives.

I would have thought cable theft of valuable copper would drive replacement

 

[Ploughman]

Laying out F/O cable on the cheap will not do anything for its durability.
By which I mean laying out the cable on the ground or draped across vegetation rather than being put in a duct or buried.

 

[John Webb]

I would have thought cable theft of valuable copper would drive replacement

I am aware of theft of copper cables from surface lines, but haven't heard anything about thefts from tube tunnels! But on rereading the OP's original post were they talking about tunnels or open-air sections?

 

[edwin_m]

Are any of these traction cables? Southern has fairly thick lineside cables at 33kV or 11kV to feed the substations. I think Woodhead also had "hooks" similar to LU and I found one in the undergrowth south of Altrincham where the line to Bowdon used to be. So I wonder if it's something to do with DC traction needing fat cables for feeding.

 

[furnessvale]

Alongside tube tracks there are many cables in racks, usually neat but also ugly. You don’t see this in BR tracks. Do tube trains need more cabling or is it just hidden?

BR used to be covered in heavy cables hanging on metal brackets on short concrete posts. Can't say I have noticed any recently, it seems to have all gone with modernisation.

I distinctly remember we had a very portly relaying ganger who used to sit on the cables, taking snuff while supervising his men. The cables used to pull tight for a couple of bays each side of where he sat!

 

[alxndr]

BR used to be covered in heavy cables hanging on metal brackets on short concrete posts. Can't say I have noticed any recently, it seems to have all gone with modernisation.

I’ve seen this type of set up in a few places over the last couple of years, certainly parts of the the GEML and GCML have it, although there’s surely other places too. It’s something that stands out not having any on our patch, and I can’t help but think it would make tracing cables a lot easier (although of course the trade off is that it’s also more tempting for theft). I also think it looks neater than the average chaotic troughing route with lids all over the shop and cables bulging out the sides.

 

[Tim M]

The way London Underground and Network Rail signalling works significantly differ. On NR location cases (steel apparatus cases) are used to house power supplies, relays, Trackside Functional Modules for Solid State Interlocking areas, track circuit equipment etc. Where relay interlocking’s are used a number of cables with up to 48 cores connect with the location cases. With SSI small copper data link cables are used. The biggest cable will carry the 650V power supply.

Such a method is impractical on the Underground, particularly in tunnel areas so each trackside object, signal, point mechanism, track circuit has its own cable. LU also used to have separate cables to each object rather than combining several functions in a common cable. Using the belt and braces style that is such a feature of LU the older cables are often armoured or lead covered making them somewhat chunkier than on the main line. Some lines retain air mains for train stops and point operation, even when air operation is abandoned the air mains may be retained as an electrical earth system.

LU are moving on with cables closer to NR specifications, this started with the Central Line about 1990 when Westinghouse did the complete packages rather than just supply components with LU doing the design etc. What will not change however will be cables from station equipment rooms to objects, a location case in a tube tunnel is still impractical. BTW most mass transit railways around the world use LU practice for the same reason.

 

[bramling]

Alongside tube tracks there are many cables in racks, usually neat but also ugly. You don’t see this in BR tracks. Do tube trains need more cabling or is it just hidden?

On every LU line there will be power cables (the high tension supply to the substations) and in most areas a compressed air main - neither of these will be found on unelectrified main lines. Some Southern Region electrified lines used to route their power cables on a cable run just like on LU but this practice went out of fashion very many years ago in favour of troughing. This then leaves signalling and communications cables - again it’s simply LU practice to route them above ground. Maybe LU is less vulnerable to vandalism with their lines generally always having being well fenced?

 

[ess]

Yes I meant the outside the tunnels sections. These racks are several feet high and always well populated with many cables. What was the compressed air for?

 

[Tim M]

This then leaves signalling and communications cables - again it’s simply LU practice to route them above ground. Maybe LU is less vulnerable to vandalism with their lines generally always having being well fenced?

On Tube lines the only place available for cables and other services is on hangers about half way up the side of the bore, I suspect this is also true of the sub-surface lines where the chess is used for drainage. LU also route cross track cables on bridges rather than under track crossings. Why use cable hangers rather than cable troughs, I have no idea of the history but it probably goes back to Victorian times.

 

[Tim M]

Yes I meant the outside the tunnels sections. These racks are several feet high and always well populated with many cables. What was the compressed air for?

Compressed air on LU is used by the signalling systems for several purposes. Until the early 1990’s most if not all points were air operated (I once found the original 1912 drawings at Westinghouse, the design has not changed much). The mechanism is placed between the rails, i.e. in the 4 foot, the only option in Tube tunnels. They are also much faster to operated, about 1 second vs. 4 seconds for an electrical machine. Even here LU are moving away from air operation, the Westinghouse Surelock machine being low profile and mounted in the 4 foot, they can be stripped down in situ and rebuilt in 10 minutes.

Train stops are also air operated, although there are designs available for electrical operation. Shunting signals are also sometimes air operated.

Finally the Westinghouse Style V interlocking machines are also air operated. The levers are attached to vertical shafts and are normally moved by air as instructed by the programme machines, or of course these days are computer controlled. I think the last Style V machine was built as late as the 1980’s. All this changed with the Central Line Resignalling in the 1990’s, and it cannot be many years before mechanical Interlocking will be no more.