Creation of class 230 DEMUs from ex-LU D78s by Vivarail

[GrimsbyPacer]

If you asked the majority of District Line users, they would have no idea that the D78 stock dates back to then 70s. They don't look like old trains, with their very comprehensive and contemporary refresh. The public would probably think they are far newer than say the 1992 stock

I know little about London Underground stock. Are any other trains due to be replaced soon and could they be refurbished in the same way? I ask as the D-Trains Vivarail make won't be able to replace half the Pacer fleet. Also it looks like some forum members outside of the Northern franchise would like them on their lines.

 

[Mikey C]

I know little about London Underground stock. Are any other trains due to be replaced soon and could they be refurbished in the same way? I ask as the D-Trains Vivarail make won't be able to replace half the Pacer fleet. Also it looks like some forum members outside of the Northern franchise would like them on their lines.

No.

The stock that is due to be replaced next is Tube stock i.e. the small trains that would look really odd on the National Network (apart from the IOW of course!)

The D78s are a unique case as London Underground are replacing all their 'full size' sub-surface stock with a common fleet of new S7 and S8 trains. The A and C stock that have already been replaced were time expired, but the D78s aren't and are only being replaced to create a common stock across the network

 

[GrimsbyPacer]

I wouldn't mind Tube trains if it eased overcrowding. It is already used by many so why can't they be run like these D-Trains? Yes they will look silly but there's still enough headroom. And it will be cheaper than new trains and avoid fare rises.

I used Northern and Central lines in London before and I think they're the small tube trains you refer to. They are way more spacious than the Glasgow Subway.

 

[Murph]

I wouldn't mind Tube trains if it eased overcrowding. It is already used by many so why can't they be run like these D-Trains? Yes they will look silly but there's still enough headroom. And it will be cheaper than new trains and avoid fare rises.

I used Northern and Central lines in London before and I think they're the small tube trains you refer to. They are way more spacious than the Glasgow Subway.

It would very likely be impossible to fit under-floor engines to them, as the floors are much lower on tube stock. Additionally, it would probably be very difficult to get safety approval for them, as their sole bars are substantially lower than standard height buffers. In a collision between tube stock and a full size train, there would be a significantly higher than normal risk of the full size train riding over the top of the tube train, through the passenger accommodation. Basically, they are completely unsuitable for use on the national network, in contrast to the D78s being basically very close to normal trains and still having plenty of life in them.

Lastly, the tube stock floor would be significantly below normal platform height, and the chances are that they will be quite close to completely knackered by the time they are withdrawn.

D78s are very much an unusual and unique special case. It's possible that some tube stock might find its way to the Isle of Wight (to replace the 1938 tube stock used there), but that's about it, the remainder have an appointment with a metals merchant which is unlikely to be broken.

 

[edwin_m]

It would very likely be impossible to fit under-floor engines to them, as the floors are much lower on tube stock.

You could always put the engines in pods on the roof. JOKE!

 

[67018]

The other important distinction is that D78 stock is already cleared to run on National Rail due to the shared track with the District Line. Central or Northern Line trains would have to be safety cleared from scratch, an additional cost, even if they could be made acceptably safe without a lot of work (unlikely).

Presumably Bakerloo tube stock is also NR-cleared for the same reason, but they won't be free for another 10 years at least, by which time they will be 50 years old!

 

[jopsuk]

But the stock will be getting an all-new crash structure on/in the drivers cab anyway, as part of the upgrade. it'll also get all required safety systems (ATP, AWS, TPWS) appropriate to where it is intended to operate

 

[Buttsy]

I used Northern and Central lines in London before and I think they're the small tube trains you refer to. They are way more spacious than the Glasgow Subway.

Possibly because LU is on 4' 8 1/2" gauge and Glasgow Subway on 4" gauge, so the latter has a smaller loading gauge overall.

 

[GrimsbyPacer]

It would very likely be impossible to fit under-floor engines to them, as the floors are much lower on tube stock. Additionally, it would probably be very difficult to get safety approval for them, as their sole bars are substantially lower than standard height buffers. In a collision between tube stock and a full size train, there would be a significantly higher than normal risk of the full size train riding over the top of the tube train, through the passenger accommodation. Basically, they are completely unsuitable for use on the national network, in contrast to the D78s being basically very close to normal trains and still having plenty of life in them.

Lastly, the tube stock floor would be significantly below normal platform height, and the chances are that they will be quite close to completely knackered by the time they are withdrawn.

D78s are very much an unusual and unique special case. It's possible that some tube stock might find its way to the Isle of Wight (to replace the 1938 tube stock used there), but that's about it, the remainder have an appointment with a metals merchant which is unlikely to be broken.

You can't use safety as a reason not to use them to replace Pacers.
In one of the Winsford rail crashes a Pacer's entire frame came off!

I do understand it would be harder to modify them though.

 

[Bletchleyite]

In one of the Winsford rail crashes a Pacer's entire frame came off!

You do know they were sort-of designed to do that, right? They are not the same as Mk1 stock, they have a strong[1] monocoque body on top of the underframe, the latter being there not for reinforcement but for convenience of construction. Though it was decided retrospectively that it wasn't the best approach and after that they were all modified with reinforcements to the body-underframe joins, you can see the bolts in the stepwells.

The Class 153 has a very similar body without an external underframe.

[1] A heavy belt from a Class 87 was going to smash the end in whatever it was - 156s and the likes have been smashed in in the same way, and remember that in Southall the Turbo's end vehicle was demolished to the point of just being shards of metal, with it looking rather more like a lightly damaged 2-car unit than a 3-car one in which there was basically nothing left of the third car and its occupants.

Neil

 

[jopsuk]

Possibly because LU is on 4' 8 1/2" gauge and Glasgow Subway on 4" gauge, so the latter has a smaller loading gauge overall.

loading gauge and track gauge don't scale quite like that. There's many metre (or metre-ish) gauge railways around the world with larger loading gauge than the UK mainline network, whilst Ireland basically has the same loading gauge as the UK yet runs a broad track gauge. That the Glasgow subway has a smaller loading gauge than London Underground tubes is possibly WHY they went with a smaller track gauge- but they almost certainly didn't go with a smaller loading gauge BECAUSE they were using a narrower track.

 

[Murph]

You can't use safety as a reason not to use them to replace Pacers.
In one of the Winsford rail crashes a Pacer's entire frame came off!

I do understand it would be harder to modify them though.

You can use safety as a reason when they would likely perform worse than a Pacer in a crash end on against normal stock… A collision between normal stock and tube stock would have the buffers and frame of the normal stock hitting body panels without any major structure behind them. A very likely result would be complete obliteration of the body of the tube stock as the normal stock continued over the top of the much lower frame of the tube stock, if there was any speed involved. Frankly, you'd be much better refurbing the Pacers properly (including improving crash performance), than trying to make tube stock safe for national main line use.

It's all moot anyway, there's not going to be any tube stock coming free with any life left in it, and nothing being replaced before 2025. The D78s are the last and only surplus from LUL with any realistic chance of operating on the national network, until the S stock gets replaced in 25-50 years time.

 

[edwin_m]

Possibly because LU is on 4' 8 1/2" gauge and Glasgow Subway on 4" gauge, so the latter has a smaller loading gauge overall.

Does everybody have to stand very still to stop it tipping over?

 

[Xenophon PCDGS]

The Harrogate Chamber of Trade and Commerce have expressed interest in elderly London Underground stock in past days. Have they made any recent comment about some of these units being used on the Leeds-Harrogate-York line?

 

[edwin_m]

The other important distinction is that D78 stock is already cleared to run on National Rail due to the shared track with the District Line. Central or Northern Line trains would have to be safety cleared from scratch, an additional cost, even if they could be made acceptably safe without a lot of work (unlikely).

Presumably Bakerloo tube stock is also NR-cleared for the same reason, but they won't be free for another 10 years at least, by which time they will be 50 years old!

The DC lines are normally only used by stock fitted with tripcocks, which will stop a train within the overlap if it passes a red signal. So as SPADs are one of the main causes of collisions, a collision between a Bakerloo and main line stock much less likely than a collision anywhere else on the network. If the Bakerloo stock was to be considered for running anywhere else then this or some other measure would be needed to reduce the risk.

I'm not sure what situation applies with tripcocks on the routes D78 shares with NR, but it's possible some extra mitigation is needed for collision risks if they run on other routes. That might explain the extra structure at the cab ends.

 

[GrimsbyPacer]

Does everybody have to stand very still to stop it tipping over?

It can't tip over. The entire subway is underground with no room for it to tip over. The track is only 8inches smaller. So it's larger than Cape and Metre gauges.

Edit, as people are moaning at me for using the correct gauge rather than 4 inches that someone else wrote by error I've been told to review this. Am I to pretend that it will fall over???

 

[Peter Sarf]

You could always put the engines in pods on the roof. JOKE!

That could be marketed as an improvement that would be appealing to many - NO UNDERFLOORENGINES .

 

[Bantamzen]

As a bit of a layman can I ask a couple of questions?

Firstly don't diesel engines come with a greater weight overhead? And secondly wouldn't this mean that any coverted D-stock would have worse acceleration than it currently has with electric motors? If so, would any converted stock really be an improvement considering that they won't offer much in the way of capacity increases, if indeed any, plus they will have a lower top speeds as well as similar acceleration?

I have to say that the prospect of slower stock, albeit with shiny new plastic seats and a bit of a body job, really doesn't smack of improvements. Actually it's starting to sound like a Pacer MKII project. Of course it's cheaper, well until of course someone realises they are not possibly going to be a long term, or even medium term solution. Not exactly good value for money, it's actually a bit of a Del Boy solution isn't it? Lavvvy Jubbley...

 

[Domh245]

It can't tip over. The entire subway is underground with no room for it to tip over. The track is only 8inches smaller. So it's larger than Cape and Metre gauges.

as edwin_m highlighted

on 4" gauge

as in 4 inch gauge, and if you had a 4" gauge, you probably would have to stand still to prevent it toppling, even in a tunnel!

 

[MarkyT]

I'm not sure what situation applies with tripcocks on the routes D78 shares with NR, but it's possible some extra mitigation is needed for collision risks if they run on other routes. That might explain the extra structure at the cab ends.

Between Gunnersbury and Richmond, only mechanical train-stops are fitted at each signal. All trains have or had trip-cocks: District D78, new 'S' stock, old Silverlink 313s and new Overground 378s.

Between East Putney and Wimbledon, the District line is shared with SWT rolling stock not fitted with trip-cocks. Each stop signal is thus fitted with both a standard mechanical train-stop and a TPWS TSS but no OSS. AWS is also provided at standard distance on approach. The fairly fragile TPWS antennas, situated in gaps along the central conductor rail like the AWS inductors, are protected by more substantial ramps fitted above them against damage, presumably from contact shoes.

Prior to TPWS District trains to Wimbledon were not protected against out of control SWT movements although the main line drivers were at least kept alert by AWS.

 

[edwin_m]

As a bit of a layman can I ask a couple of questions?

Firstly don't diesel engines come with a greater weight overhead? And secondly wouldn't this mean that any coverted D-stock would have worse acceleration than it currently has with electric motors? If so, would any converted stock really be an improvement considering that they won't offer much in the way of capacity increases, if indeed any, plus they will have a lower top speeds as well as similar acceleration?

I have to say that the prospect of slower stock, albeit with shiny new plastic seats and a bit of a body job, really doesn't smack of improvements. Actually it's starting to sound like a Pacer MKII project. Of course it's cheaper, well until of course someone realises they are not possibly going to be a long term, or even medium term solution. Not exactly good value for money, it's actually a bit of a Del Boy solution isn't it? Lavvvy Jubbley...

The diesel engines will add some weight, as will the extra structure mentioned for the cab ends, although replacing the electromechanical control gear with solid state may offset some of this. It may also be that the diesels can supply slightly less power to the electric motors than the third rail can on the Underground. Either of these could mean a bit less acceleration than the D78s have now, particularly at higher speeds. 3- and 4-car sets will also have less acceleration than 2-car as it appears the non-driving cars in the middle will also be unmotored. On the other hand Viva are claiming acceleration will be better than a Pacer or Sprinter.

The bigger concern in my view is the top speed of only 60mph. This makes them unsuitable for the many routes where Sprinters or Pacers use their 75mph maximum speed, particularly on main lines where they need to keep ahead of other trains. I'm sure the Viva people realise this and would have made them faster if this was economically possible, but Underground running gear is pretty basic and the wheels are also smaller than other main line stock, so I guess that would have been too much work and cost.

I would say that if these are reliable and used on suitable routes they would be much more attractive than the newer but rather worn-out trains running on those routes today. The idea is only to keep the D78s in service for a decade or so, by which time either electrification will have displaced a lot of DMUs, or it will have been agreed that this isn't going to happen and some new DMUs need to be ordered.

 

[apk55]

The diesel engines will add some weight, as will the extra structure mentioned for the cab ends, although replacing the electromechanical control gear with solid state may offset some of this. It may also be that the diesels can supply slightly less power to the electric motors than the third rail can on the Underground. Either of these could mean a bit less acceleration than the D78s have now, particularly at higher speeds. 3- and 4-car sets will also have less acceleration than 2-car as it appears the non-driving cars in the middle will also be unmotored. On the other hand Viva are claiming acceleration will be better than a Pacer or Sprinter.

I would expect the starting tractive effort to be the same as when it was an electric train but would start to fall off with increasing speed at a lower speed than before (following a constant power curve), although at high speed TE would probably be not much less.
The torque converter system used on Pacers does not give much tractive effort at starting dispite the engine roar (and is very inefficient in this mode). It is only when converter lock up is achieved around 40mph that it becomes efficient.
Therefore I would expect these units to be much quicker from a standing start.

 

[MarkyT]

I would expect the starting tractive effort to be the same as when it was an electric train but would start to fall off with increasing speed at a lower speed than before (following a constant power curve), although at high speed TE would probably be not much less.
The torque converter system used on Pacers does not give much tractive effort at starting dispite the engine roar (and is very inefficient in this mode). It is only when converter lock up is achieved around 40mph that it becomes efficient.
Therefore I would expect these units to be much quicker from a standing start.

Interesting. Would I be correct in presuming a similarly more efficient diesel-electric transmission in voyagers contributes as much to their impressive high starting acceleration as sheer engine output (noting also their comparative lard-arsed weight stats)?. If D-Trains were used in place of pacers down here in South Devon for metro type operations, I would hope their rheostatic braking resistors and controls would be made less susceptible to salt water spray along the Dawlish sea wall than Voyagers though!

 

[Xenophon PCDGS]

Are there no diesel-only services in the southern half of the country where these units could be utilised?

 

[GrimsbyPacer]

Are there no diesel-only services in the southern half of the country where these units could be utilised?

Someone on here mentioned Berkshire branches.
And if they are seen as Pacer replacements in the North than areas of Devon and Glamorgan which use them are also suitable.
Cornish branches did have Pacers shortly but were replaced because of the tight curves, this won't be an issue with D-Trains.

 

[NotATrainspott]

How many branch lines are there with a maximum speed above 60mph? Even if they didn't need the extra capacity of a two/three/four car D-Train, allowing their current 75mph stock to be used where 75mph capability is a necessity would be a good idea.

 

[61653 HTAFC]

If the prototype unit is a success, many of the Cornish branches would be ideal places for them. Unlike many of the services suggested in the North, the Looe and Newquay branches in particular have little or no mainline running where the 60mph speed would be an issue.

This would then free up some sprinters for the likes of Leeds to Huddersfield stoppers.

 

[Hophead]

Someone on here mentioned Berkshire branches.

Except the branches are due to be wired (although I'm not sure if anybody's found the funds or planned the project yet)

 

[edwin_m]

There are some opportunities on the GW network but their existing fleet is likely to be on lease until the end of the franchise. So unless they can find someone to sub-lease the existing units to, they would still be paying for them whether they use them or not.

 

[LNW-GW Joint]

Are there no diesel-only services in the southern half of the country where these units could be utilised?

Assuming you meant "not the north", some suggestions:
Cardiff Valleys, if the wires do not go up quick enough.
West Wales/Central Wales
Greenford branch
Marshlink
Devon/Cornwall short branches
Matlock-Derby-Crewe
Wrexham-Bidston, Llandudno-Blaenau Ffestiniog
some East Anglia locals
Bedford-Bletchley
Aylesbury-Princes Risborough
Glasgow-East Kilbride (until wired)

In the north outside urban areas:
Cumbrian coast
Settle-Carlisle (limited to 60mph)
Middlesbrough-Whitby
Newcastle-Carlisle

Any of these free up "big" DMUs for cascade to "main" routes.
Somehow, I don't think the D78 allocation will be "democratic".