MML Electrification: progress updates

[zwk500]

At normal times, there is no traction on the slows that can use electrification. So in a sane world, they would electrify the fasts and then move on to another area where electrification will deliver immediate benefits. But given the political imperative to demonstrate lower costs per single track kilometre, I expect they will do all four tracks before anywhere else.

The cost of having to come back and do the slows later would cause plenty of problems - look at King's Norton to Barnt Green for the inverse. Also there's plenty of reasons services might need to be crossed to the slows on the day and it'd be madness not to wire them while you're there.

 

[Nottingham59]

Also there's plenty of reasons services might need to be crossed to the slows on the day and it'd be madness not to wire them while you're there.

yes, but unlike Barnt Green, all the electric traction planned for the MML is bimode. These won't need OHLE to use the slows.

 

[zwk500]

yes, but unlike Barnt Green, all the electric traction planned for the MML is bimode. These won't need OHLE to use the slows.

They won't but the cost saving on installation will be small and the later installation costs will be huge. If a Minister was making the decision then it may be fast lines only but the sensible decision would be to do all 4.

 

[Nottingham59]

They won't but the cost saving on installation will be small and the later installation costs will be huge. If a Minister was making the decision then it may be fast lines only but the sensible decision would be to do all 4.

I'm sure they will do all four. The "minister" has effectively made that decision by choosing cost per stk as the only metric that matters.

 

[takno]

The cost of having to come back and do the slows later would cause plenty of problems - look at King's Norton to Barnt Green for the inverse. Also there's plenty of reasons services might need to be crossed to the slows on the day and it'd be madness not to wire them while you're there.

It's a bit different electrifying one pair of lines, particularly in an age where twin-track cantilevers are in fasion, as opposed to electrifying the outer lines on a set of 4 as at King's Norton. Operationally you are much less likely to make moves from paired fasts to paired slows and vice versa in normal running, so the value is lower, and because you have to throw up a post on either side of the formation anyway the cost of doing just the outer lines is much closer to the cost of doing all four lines.

Also worth noting that King's Norton to Barnt Green was also done with a small amount (about a million quid IIRC) of passive provision to electrify the mains, but given the period when it was done the passive provision was probably headspans, which is unlikely to be making anybody's life easier today.

 

[Brissle Girl]

I'm not an engineer, but I would have thought that a simple portal structure would be slightly more cost effective than TTC, and would also in my view be aesthetically preferable.

 

[zwk500]

I'm not an engineer, but I would have thought that a simple portal structure would be slightly more cost effective than TTC, and would also in my view be aesthetically preferable.

A portal will likely require more piling work to install, and the key difference for the MML will be that portals require an all-line block to install the main span beam, while TTCs can be done while taking 2 separate 2-track possessions, allowing traffic to continue on the other pair. TTCs are preferred on two-track routes because they nearly halve the number of piles required (important for neighbours) and therefore massively reduce the amount of possessions required (important for anybody using the network).
I expect that the final design will call for a mix of TTCs, STCs and Portal structures, because there will be different considerations at specific points.

 

[Brissle Girl]

I’m not sure why they would need more piling work, and there’s no benefit to the overall number of piles on a 4 track route - it’s two for both options.

 

[zwk500]

I’m not sure why they would need more piling work, and there’s no benefit to the overall number of piles on a 4 track route - it’s two for both options.

Gantries may require diagonal bracing - although any such locations where that is needed would likely be gantries anyway so the amount of piling for a 4-track is probably not a major distinction. However TTCs would allow you to be more flexible with where you put the piles either side. As I've mentioned, the big difference on a 4 track line will be the amount and type of engineering access required to install them.

 

[LTJ87]

Network Rail are carrying out Ground Investigation work near Nottingham Station over five nights in early April as part of early preparatory works.

 

[AM9]

Gantries may require diagonal bracing - although any such locations where that is needed would likely be gantries anyway so the amount of piling for a 4-track is probably not a major distinction. However TTCs would allow you to be more flexible with where you put the piles either side. As I've mentioned, the big difference on a 4 track line will be the amount and type of engineering access required to install them.

Taking a simple mechanical point of view, the single point mounting of TTCs must be more substantial than each end of a four track gantry providing it is on a normal section with no more than a 10ft between the two pairs of lines. Much of the MML has a mere 6ft way between all tracks. A gantry has a pile support that needs to maintain vertical alignment in one axis only, i.e. the longitudinal axis wrt the track, the cross track stresses being largely cancelled out by simple corner bracing on the horizontal beam. A TTC structure needs substantial stiffness to support an offset load which increases it's weight considerably. This leaves the pile needing to maintain vertical alignment in both the longitudinal and cross track axes as well as resisting twisting.
It may be slightly more convenient needing less engineering access during installation and very occasionally during maintenance, but we are talking modern OLE here fit for purpose rather than headspans which give the worst of both worlds which cause total route blockages whenever there is a dewirement.

 

[edwin_m]

Taking a simple mechanical point of view, the single point mounting of TTCs must be more substantial than each end of a four track gantry providing it is on a normal section with no more than a 10ft between the two pairs of lines. Much of the MML has a mere 6ft way between all tracks. A gantry has a pile support that needs to maintain vertical alignment in one axis only, i.e. the longitudinal axis wrt the track, the cross track stresses being largely cancelled out by simple corner bracing on the horizontal beam. A TTC structure needs substantial stiffness to support an offset load which increases it's weight considerably. This leaves the pile needing to maintain vertical alignment in both the longitudinal and cross track axes as well as resisting twisting.
It may be slightly more convenient needing less engineering access during installation and very occasionally during maintenance, but we are talking modern OLE here fit for purpose rather than headspans which give the worst of both worlds which cause total route blockages whenever there is a dewirement.

The cost of making the pile larger/deeper to withstand these stresses would be a tiny part of the total cost associated with that pile, once design and the logistics of installing it are considered.

 

[Richard123]

The cost of making the pile larger/deeper to withstand these stresses would be a tiny part of the total cost associated with that pile, once design and the logistics of installing it are considered.

Portals require shorter piles (quicker to install and fewer rejections), less steel, and are less likely to suffer movement during life.

Conversely, they require all line block during boom installation, and probably most significant, require the up and down teams to put their piles in the right place and direction (give or take a little), much less accuracy is required for TTCs that don't need to meet in the middle.

 

[al_557]

I recall Leicester is being left out for the time being, as a gap, whilst they come up with a solution with the low bridge at the south end of the station. There’s the station buildings and busy main road above and a sewer below, so limited options.

The next stages I believe are Leicester north. Although where will the starting point be? Around Syston or north of Leicester station/Humberstone Road sidings?

They will probably have to lower the track to get around the Leicester station issue.
I can't see the bridge getting rebuilt as it would cost millions

 

[Nottingham59]

They will probably have to lower the track to get around the Leicester station issue.
I can't see the bridge getting rebuilt as it would cost millions

You can't just lower the tracks, though. They would need to lower the platforms of the station itself, which are immediately adjacent to the bridge. It's not like Cardiff, where there is 500m between the Intersection Bridge and the station platforms.

And if the wires are at the closest possible to the top of the train, I don't know how they plan to resolve the issue of 25kV then being too close to the platform.

 

[QSK19]

They will probably have to lower the track to get around the Leicester station issue.
I can't see the bridge getting rebuilt as it would cost millions

I seem to remember that lowering the track is practically impossible too; so the solution would have to be discontinuous electrification (the train coasting under the bridge before pan up again) or some sort of arc-resistant paint allowing the wires to get super close.

 

[takno]

I seem to remember that lowering the track is practically impossible too; so the solution would have to be discontinuous electrification (the train coasting under the bridge before pan up again) or some sort of arc-resistant paint allowing the wires to get super close.

I've taken this image from the relevant Don Coffey video (

). Paint doesn't work because the wires need to be significantly higher than the top of the train when you get to the platforms, which start directly after the bridge. You could raise the bridge a bit, although it would involve some fairly steep approaches and a huge amount of work, and the station buildings on the bridge would have to go. Honestly I'd say the better option is probably to lower the tracks and rebuild all the platforms. On the face of it that's potentially a smaller job than Derby, but definitely not cheap.

If we're looking at a world where at least short distance battery power is acceptable on passenger trains, it might make most sense to not wire the existing platforms at all, and just lower the lines on the east side, so that you can have an electrified through-route for freight.

 

[mr_jrt]

Do I remember rightly that you can't lower the tracks as there's a sewer directly underneath?

 

[midland1]

I seem to remember that lowering the track is practically impossible too; so the solution would have to be discontinuous electrification (the train coasting under the bridge before pan up again) or some sort of arc-resistant paint allowing the wires to get super close.

I was told that when they rebuilt the station about 1980 they slopped the platforms away from the track so if they ever put wires up they would lower the track and level off the platforms to match the track level, I do not know if it is right though. I thought that when there was a lot of low bridges and speeds were low they could lower the voltage like they did at Stockport in 1960.

 

[Wyrleybart]

Also worth noting that King's Norton to Barnt Green was also done with a small amount (about a million quid IIRC) of passive provision to electrify the mains, but given the period when it was done the passive provision was probably headspans, which is unlikely to be making anybody's life easier today.

I am assuming you and zwk500 are meaning Redditch rather than Barnt Green

 

[gingertom]

I wonder if this new (to the UK) plastic sleeper system, as recently used in Moncrieff tunnel near Perth, could be used here? It requires less ballast, so is a track lowering to some extent, perhaps sufficient if used in conjunction with polymer insulating paint and surge arrestors?

 

[Ploughman]

Would Slab Track be an option? That would tighten up on the clearances.

Also, is reduced height rail still available?

 

[takno]

I am assuming you and zwk500 are meaning Redditch rather than Barnt Green

The electrification continued to Redditch, but the section with fast lines which weren't electrified ends between Longbridge and Barnt Green.

 

[edwin_m]

The electrification continued to Redditch, but the section with fast lines which weren't electrified ends between Longbridge and Barnt Green.

Most of the way from Kings Norton to Longbridge just the outer two tracks are electrified, then most of the way to Barnt Green it's just the inner two!

 

[Meerkat]

Paint doesn't work because the wires need to be significantly higher than the top of the train when you get to the platforms, which start directly after the bridge. You could raise the bridge a bit, although it would involve some fairly steep approaches and a huge amount of work, and the station buildings on the bridge would have to go. Honestly I'd say the better option is probably to lower the tracks and rebuild all the platforms.

Apparently there is a sewer meaning lowering is not possible, though fancy track systems might gain a little bit.
How sloped can the wires be (speed not that important as all passenger trains are stopping)? Rough google maps measuring suggests you could get away with losing the southern 30m of the platforms.

 

[swt_passenger]

Apparently there is a sewer meaning lowering is not possible, though fancy track systems might gain a little bit.
How sloped can the wires be (speed not that important as all passenger trains are stopping)? Rough google maps measuring suggests you could get away with losing the southern 30m of the platforms.

There was a sewer right across the Kings Cross throat that “prevented track lowering” for years. But they eventually lowered it by converting it from a round cross-section to a wide flat culvert. It was done during the fairly recent track alterations for the tunnel reopening. I wouldn’t think it’s a low cost solution, but it shows what can be done.

 

[InTheEastMids]

There was a sewer right across the Kings Cross throat that “prevented track lowering” for years. But they eventually lowered it by converting it from a round cross-section to a wide flat culvert. It was done during the fairly recent track alterations for the tunnel reopening. I wouldn’t think it’s a low cost solution, but it shows what can be done.

The Leicester London Road Bridge has come up previously on this thread before, e.g. way back in 2019, see #3271 below:

Is the really big problem with further MML electrification (whenever it gets approved) the height available at Leicester ?

To which, one of the very knowledgeable commentators on this forum said this in #3272

That is a problem. However AIUI it can be solved in the same was as at Cardiff.

As I'm not in the rail industry, let alone close to the project, I have no clue whether further issues have been brought to light in the last 4-and-a-bit years

 

[Mr. SW]

Interesting about the sewer. I knew about the Kings Cross effort, but this made me think about some other places where there are awkward infrastructure problems.

The Longford River passes directly under Feltham Station in West London at such a shallow depth, a concrete slab has had to be cast over it and the rails attached directly to it as can be seen in this image.

File:411581 Feltham station.jpg - Wikimedia Commons

commons.wikimedia.org

You can see the smooth slab under the front of the train.

Another place is on the Keighley and Worth Valley Railway, where the Bridgehouse Beck runs under the line just south of Haworth Station under bridge 27 as seen here...

Bridge 27 Renewal - Keighley & Worth Valley Railway

The Bridge 27 renewal project is quickly coming over the horizon as the next big civil engineering project for the railway. The planning and design are well underway, with September 2024 being the current target date for the main bridge renewal with a three-week closure planned. However, changes...

kwvr.co.uk

As you can see, there is next to no clearance.

I'm sure that a solution will be found.

 

[Trainben]

Does anyone know how close we are to the wires being energised? All looks complete driving along the A6 but not sure about the other sections.

 

[GRALISTAIR]

Does anyone know how close we are to the wires being energised? All looks complete driving along the A6 but not sure about the other sections.

I assume you mean Kettering to Wigston south?