Idea: Third rail/Diesel hybrid for Southern.

[biggus]

So I keep reading that NR is serious about converting the Southern region's third rail to AC OLE.

The expense would be staggering, and with a network that is suboptimal in so many other ways (missing links, lack of passing places, flat junctions etc), it seems like a strange thing to be prioritising.

Nonetheless, NR points out that third rail does not provide sufficient power for the tains to accelerate or run as fast as they could, so third rail acts as a capacity and performance constraint. Furthermore some shockingly high percentage of electricity input is lost as heat. (I believe these resistive losses increase on a curve as loads increase.)

Is coping with spikes in demand the problem? To be clear, my objective is not to reduce overall power consumption, just peak load. So part of the question is, would reducing peak load per train make sufficient difference to peak load on the distribution system (which serves multiple trains) to avoid the need for conversion to an AC power supply?

If so, would it not be easier, cheaper, and better to equip the trains with some form of online energy storage, either in the form of diesel generators or even batteries that could provide the trains with a power boost for the relatively short periods when they accelerate hard or run at high speed? When coasting or idling, they would recharge, much as hybrid cars are supposed to do.

If using just batteries (no diesel generators) total electricity usage would increase to cope with the extra weight and the losses within the batteries.

The case for running the trains with diesel generators becomes easier conceptually if you consider it a case of a diesel train that gets a bit of a boost from third rail power.. The engines etc would make the trains heavier than electrics but surely the economics and the energy use would work out better than pure diesel. Diesel hybrid trains could be introduced progressively, without disruption, as need dictates.

I can see that hybrid trains with regenerative braking could potentially cause safety problems if they energise the third rail when it is supposed to be switched off for engineering works. Regenerative brakes on conventional electrics could potentially cause the same problem, in the less likely event that they coast onto a section where the power is off, so perhaps a safe solution has been developed for regenerative braking that would also enable hybrid trains to run?

The other nice thing about hybrids is that they would be able to limp home without third rail power, and enter and leave non-electrified sidings etc.

This link below addresses some of the issues, but considers energy saving rather than load smoothing.
http://www.railforums.co.uk/showthread.php?t=34994

 

[The Colonel]

No need to re-invent the wheel. We've had them and they were called Class 73's or Electro-Diesels. Under the MDTR they've been done away with though.

 

[biggus]

No need to re-invent the wheel. We've had them and they were called Class 73's or Electro-Diesels. Under the MDTR they've been done away with though.

Thanks! Interesting wikipedia article on these.

I believe the other thing which is virtually verboten on the MDTR is large axle loads. I must resist the temptation to research this now, but I assume the axle loads from a 73 are quite a bit bigger than those of a multiple...

So maybe there's a nice job for someone to design a hybrid multiple that spreads all that horrid weight over lots and lots of axles.

 

[jopsuk]

Mdtr?

 

[The Ham]

The problem is that they would probably be a little more expensive than a diesel only train, which would result in the same complaints that you have about the proposed IEP's where some people suggest that it is better not to have them.

Personally I think that they could be useful and could overcome a number of problems (including removing the need for electrifying gaps in the network for some routes).

With regards to cost; the proposal is to provide overhead cables when the third rail is due for being replaced at the end of its working life, it also appears to be being done along side gauge clearance works for freight both of which remove the two big costs associated with switching from 3rd rail.

I would expect that the lines which get done first are the more rural longer distance lines (for example the South West Trains routes south and west of Woking), which would also reduce the impact on the cost as well as maximising the benefits.

I'm not sure about all the lines, but often the limiting factor on the number of services is not the junctions that the services pass through but rather the termini stations where the services have to reverse back out the way they have just come.

One way of overcoming this is by building Crossrail 2 as a regional railway which could well mean that many of the inner services on Southern and South West Trains then run through London in new tunnels (I would assume with overhead cables) and link up with services on Greater Anglia. This would also overcome some of the other problems with capacity as well, but at the very least would provide relief to London Waterloo, London Victoria, Clapham Junction and London Liverpool Street. It would also overcome some of problems with providing overhead cables on the inner London sections of these routes.

 

[tbtc]

So I keep reading that NR is serious about converting the Southern region's third rail to AC OLE.

The expense would be staggering, and with a network that is suboptimal in so many other ways (missing links, lack of passing places, flat junctions etc), it seems like a strange thing to be prioritising

Supposedly it's only lines where the infrastructure is coming up for renewal/ replacement, and it's more effective to covert to DC than to retain AC.

I don't know the maths, I just swallow what they put in press releases...

 

[Smudger105e]

Axle loading must be kept generally below 25 tonnes. So a B-B or Bo-Bo loco must be under 100 tonnes and a C-C or Co-Co loco under 150 tonnes. Only approximate figures, but you get the idea...

 

[D365]

Supposedly it's only lines where the infrastructure is coming up for renewal/ replacement, and it's more effective to convert to DC than to retain AC.

I don't know the maths, I just swallow what they put in press releases...

Think you got that the wrong way round?

I don't understand what Crossrail 2 has to do with this, as mainline-spec trains would probably be the same as Thameslink/Crossrail - 25kV AC with or with the possibility to install 750v DC. I wonder which and how many branches will pop up and how it would intergrate with Crossrail 3, which I do not believe is needed. We can assume fairly safely that no more brand-new tube lines will be built.

I don't think any remaining A or D Stock will find regular mainline use. I hope that enough will be preserved of everything.

 

[The Colonel]

Mdtr?

A term from WNXX
Modern Dynamic Thrusting Railway.

A phrase coined in general dismay at the companies running the railway now often using puerile/futile ideas in attempt to run a joined up railway.

 

[biggus]

I think a big downside of my own suggestion (and that of the IEP I suppose) is that you have to bear the costs of building and/or maintaining two sets of power supply equipment ... i.e. the electrical infrastructure and the more complicated trains with their onboard diesel generators... at the same time.

.... the numbers. I wonder if anyone has done the numbers.

If parts of the 3rd rail network go to 25kV more or less ad-hoc, then you have the expense of running dual voltage trains for a generation until the whole network has converted, or you give up a great deal of flexibility as to how you route/divert your stock for the same period of time.

 

[DXMachina]

If parts of the 3rd rail network go to 25kV more or less ad-hoc, then you have the expense of running dual voltage trains for a generation until the whole network has converted, or you give up a great deal of flexibility as to how you route/divert your stock for the same period of time.

Given that a significant proportion of 3rd rail EMUs are dual-voltage already and 90% (100% of recent builds) are designed and built to be dual-voltage-compatible with the addition of parts, this huge expense you mention does not exist

 

[tbtc]

Think you got that the wrong way round?

Sorry

 

[185]

Sorry

Confused me there too.

 

[starrymarkb]

I think a big downside of my own suggestion (and that of the IEP I suppose) is that you have to bear the costs of building and/or maintaining two sets of power supply equipment ... i.e. the electrical infrastructure and the more complicated trains with their onboard diesel generators... at the same time.

.... the numbers. I wonder if anyone has done the numbers.

If parts of the 3rd rail network go to 25kV more or less ad-hoc, then you have the expense of running dual voltage trains for a generation until the whole network has converted, or you give up a great deal of flexibility as to how you route/divert your stock for the same period of time.

Pretty much all 3rd rail stock since the class 365 is dual voltage capable. 450/444s need Transformers and Pantographs fitting (they are pre wired), plus they may need suspension tweaks - 375/377s already have the mounts and wiring (and DC only Electrostars have a concrete block in the transformer mount so that all Electrostars can use the same suspension set up)

 

[d5509]

If DC to AC conversion were to be driven by energy saving, the focus would be on lines consuming most power, which has got to be the terminals and approaches: lots of tracks, lots of trains, plenty of stop-start.

West-of-Woking might give loads of "miles converted" points but not such a high "KWH saved" gong, as wiring-up London Bridge and Victoria to East Croydon (etc). Dual system EMUs could operate through on to the 3rd rail beyond which would be converted "in due course" and I guess some rural lines might take a while get converted to AC.

The Southern Railway CL70 and BR CL71 locos (and CL74?) had a booster/flywheel system, as a flywheel is an energy storage device, does that mean they were hybrid-locos?

 

[IanBanks-Jones]

Only the class 70 had a flywheel, and that was purely to prevent 'gapping', as obviously they would have a greater chance of stopping in a place with no juice rail under the shoes. I'm pretty sure this was abandoned in the 71's and definitely not provided (or necessary) with the 74's, as they could just pull themselves onto the power again. I don't know how far they could actually go on the 'wheel, but they certainly wouldn't have been able to operate away from the power

 

[John55]

Only the class 70 had a flywheel, and that was purely to prevent 'gapping', as obviously they would have a greater chance of stopping in a place with no juice rail under the shoes. I'm pretty sure this was abandoned in the 71's and definitely not provided (or necessary) with the 74's, as they could just pull themselves onto the power again. I don't know how far they could actually go on the 'wheel, but they certainly wouldn't have been able to operate away from the power

To add a little extra. The flywheel was omitted after the first few locos but the functionality stayed the same. The booster (or Buck and Boost) set is essentially a big motor and a big generator mounted on a common shaft so are very heavy bits of equipment with or without the flywheel. The extra weight of the flywheel was found to be unnecessary after the first locos had been in use for some time.

The buck and boost with flywheel effect was not just to prevent gapping on the line and immobilising the train. When originally designed the electric locos were expected to be used on unbraked and loose coupled freight trains. A series of trials was conducted hauling unbraked and loose coupled wagons with an EMU power car and it was found there was a serious risk of injury to the guard and splitting of the train due to coupling failure when transient gapping occurred on these unbraked trains due to "surging" within the train.

The solution devised by English Electric was the buck and boost control system which could maintain tractive effort through the gaps.

 

[NSEFAN]

The third rail installations which currently exist aren't going to be replaced until they are due for an upgrade. It would be a silly waste of money ripping out fairly new equipment such as that on the East London Line. I believe that the Basingstoke-Southampton section is due for replacement soon, and it would make sense to convert this to AC if the electric spine proposals are going to be taken seriously.

Third rail has other problems. It's a much bigger hazard to workers and stray passengers, shoegear generally have more friction than a pantograph and winter inevitably brings more reliability problems compared to AC.

I don't think it's a good idea to have hybrid trains. You end up carrying a lot of extra weight around for little gain, except penny pinching in the electrification. This is exactly what is happening with the IEP. Some smart alec at the DfT has decided that we can all save a ton of cash by only partly electrifying the GWML, whilst quietly forgetting the increased track access costs of the hybrids due to carrying around a (mainly) unused diesel engine and fuel. :roll:

It is important to remember that class 73s had very small diesel engines, so they weren't ideal for heavy running off the juice. You will find that GBRF's engineering trains will often be hauled in pairs because one diesel won't cut it.

 

[jopsuk]

I think the low power of the 73s is something the project to re-engine a couple is trying to partly solve

 

[biggus]

I don't think it's a good idea to have hybrid trains. You end up carrying a lot of extra weight around for little gain, except penny pinching in the electrification. This is exactly what is happening with the IEP.

In view of the prevalence of dual-voltage units (which I had not appreciated) I agree.

On the other hand, I would not want "my" hybrid DEMU tarred with quite the same brush as the IEP in terms of vehicle weight and cost. Since the hybrid would never be expected to run under purely diesel power except in limp mode, it would have pretty small generators compared with those required to propel a train at full speed away from the wires.

My ignorance about the prevalence of dual-voltage traction is a little embarrassing, I should probably refrain from making excuses...

With so much dual-voltage stock around, couldn't NR conceivably save a lot of infrastructure money by having trains switch power source repeatedly along a route? So, for example, tunnels and areas with lots of overbridges could remain third rail and then the trains could pick up the overhead again when they hit open country?

Would managing the pantograph be the problem? I suppose it springs up to full extension if the OLE disappears?

Cheers

Biggus.

 

[The Ham]

I don't understand what Crossrail 2 has to do with this, as mainline-spec trains would probably be the same as Thameslink/Crossrail - 25kV AC with or with the possibility to install 750v DC. I wonder which and how many branches will pop up and how it would intergrate with Crossrail 3, which I do not believe is needed. We can assume fairly safely that no more brand-new tube lines will be built.

The point being, that there is on many 3rd rail lines no capacity for more services heading into the London Termini, as such something needs to be done to fix that problem before more trains can run.

Also, if the line from Wimbledon to Waterloo would have a whole load of services removed and put into tunnels running on 25kV AC it makes the case to convert the 3rd rail beyond the tunnels to 25kV AC a little better and makes the job of converting the lines into Waterloo a little easier (as there would be less traffic)

 

[RAGNARØKR]

You could have quad-mode trains with diesel and 750V, 1,500V (to run on the Tyne and Wear Metro), and 25kV. Or replace the conductor rail with silver - it is a better conductor.

 

[D365]

With so much dual-voltage stock around, couldn't NR conceivably save a lot of infrastructure money by having trains switch power source repeatedly along a route? So, for example, tunnels and areas with lots of overbridges could remain third rail and then the trains could pick up the overhead again when they hit open country?

Would managing the pantograph be the problem? I suppose it springs up to full extension if the OLE disappears?

No, you want to stick with one or the other. If you had little sections of third-rail dotted around, small 750v DC substations would be needed, plus trains would have to slow to 20mph or so to change pickup, as is done by trains on the WLL near North Pole Depot. Neutral sections under bridges would be better, perhaps

Pantographs are controlled by a hydraulic system; I'm not an expert but they don't go up over neutrual sections or during changeovers such as that I detalied on WLL.

The point being, that there is on many 3rd rail lines no capacity for more services heading into the London Termini, as such something needs to be done to fix that problem before more trains can run.

Also, if the line from Wimbledon to Waterloo would have a whole load of services removed and put into tunnels running on 25kV AC it makes the case to convert the 3rd rail beyond the tunnels to 25kV AC a little better and makes the job of converting the lines into Waterloo a little easier (as there would be less traffic)

At those speeds, OHLE wouldn't be much of an improvement in terms of efficiency and capacity. Although, you make a good point about Crossrail 2 being useful to release capacity; up to 32 12 car trains could be diverted per hour, going by Crossrail 1 specification. If connected to suburban South-West and Lea Valley lines, it may be possible to replace 455s, any reProxy-Connection: keep-alive Cache-Control: max-age=0 ining 315s and a fair number of 317s. Capacity would be released in both termini.

You could have quad-mode trains with diesel and 750V, 1,500V (to run on the Tyne and Wear Metro), and 25kV. Or replace the conductor rail with silver - it is a better conductor.

I thought you didn't like more-than-one-mode trains? That would probably cause more trouble integrating it into designs than it's worth, and the weight... Do I need to say more?

 

[RAGNARØKR]

I thought you didn't like more-than-one-mode trains? That would probably cause more trouble integrating it into designs than it's worth, and the weight... Do I need to say more?

Sorry I forgot to mention they could run on LPG and coal as well.

 

[starrymarkb]

Sorry I forgot to mention they could run on LPG and coal as well.

So basically a fleet of these...

 

[D365]

Damn, I can't seem to avoid that there picture!

@RAGNARØKR: Sarcastic or not, you're contradicting yourself...

 

[hairyhandedfool]

....Would managing the pantograph be the problem? I suppose it springs up to full extension if the OLE disappears?....

The pantographs are raised and lowered using air pressure, if the wire 'disappears' the pantograph rises and, at a set height, a valve opens releasing the air and dropping the pantograph. If this happens the pantograph cannot be raised again until it has had fitter's attention.

....Neutral sections under bridges would be better, perhaps

Pantographs are controlled by a hydraulic system; I'm not an expert but they don't go up over neutrual sections or during changeovers such as that I detalied on WLL.....

Although Neutral sections are gaps in the overhead wires, they are relatively small and the pantograph should not move up or down. A neutral section under a bridge could cause more issues than a regular contact wire.

If you mean the wire should stop for the duration of the bridge, then this would require coasting on no power, thus lowering the pan and slowing the train. That could be a serious issue where you have to consider signal positions, TPWS equipment, what trains are likely to use the line and the length of the break in the wire.

 

[D365]

Sorry, my initial post wasn't the best-researched. You make fair points there.

 

[Wolfie]

You could have quad-mode trains with diesel and 750V, 1,500V (to run on the Tyne and Wear Metro), and 25kV. Or replace the conductor rail with silver - it is a better conductor.

my bold

Hum, given the spate of metal thefts there have been, that's a good idea - NOT!

 

[Monty]

my bold

Hum, given the spate of metal thefts there have been, that's a good idea - NOT!

I was thinking that too, the sheer cost of installing silver conductor rails aside. You would have power outages on a regular basis from oiks who have managed to sabotage a substation or TP hut to get at the con rail.