GWR Class 800

[Railperf]

GWR's fears look like they were well funded. Great Western Railway warns of slower journeys on new trains

 

[47802]

GWR's fears look like they were well funded. Great Western Railway warns of slower journeys on new trains

And that article was written in Dec 16 when they were testing, and doesn't specify if they expected them to be slower because they might be restricted to the original 700hp setting, and seems more in reference about possibly not being able to speed up journey times

 

[D365]

I realise that the link is behind a paywall, however forum convention dictates you should provide an extract from the article, or at least make a note that this is a "premium" article.

 

[jimm]

GWR's fears look like they were well funded. Great Western Railway warns of slower journeys on new trains

How about giving people a bit more of the picture than a headline?

Trying to refer people to anything from the FT is tricky, as their subscription system usually means other people won't usually be able to see a story, though in terms of the case you are trying to make, that may be just as well.

All your huffing and puffing is about the current situation, when the IETs are being asked to do something they we're never meant to do - run on diesel for long distances at speeds above 100mph. After going looking for cached versions of the story, I found that the introduction of the story states plain as day - NB my emphasis in bold italics

"Rail journeys between London and the west of England and south Wales risk becoming slower when new trains are introduced in 2019, unless Network Rail keeps to its timetable to electrify services, the railway company that runs the services has warned.

IE what they really mean is that the planned speeded-up journey times will not be possible unless the 25kv wires available on almost all the 125mph sections of the GW area, on the route to Cardiff via Bristol Parkway and as far as Thingley junction on the Bath route (plus to Newbury for West Country services) in time for the major rewrite of the GWML timetable at the end of next year.

Further down the story it adds:

That makes it critical that electric wires are ready for use on high-speed, straight sections of the route — including the line between Didcot Parkway and Swindon and Swindon and Bristol Parkway — in good time for the planned start of faster services.

In essence it was someone at GWR getting their retaliation in early (very early in fact, in December 2016, just after the revised schedule for wiring was announced) just in case Network Rail failed to meet the new December 2018 target - which then coincided with the already-planned target for the GWML timetable rewrite announced in 2015 at the start of the direct award franchise.

Hopefully, people should be able to read the full article here

https://groups.google.com/forum/#!topic/uk.railway/sW-kWD2Oso8

Summary from what I have read and heard so far about them. Seats very firm and uncomfortable for a long journey - DFT specified and not surprising seeing as every new train seems to have rock hard seats now. Hardly any luggage space - DFT specified as they are commuter trains not intercity trains aimed at the commuter belts. On electric mode they are seriously quick, and very quiet. Diesel mode they are exactly as expected and seriously lack power unless you have them on max power where they can just keep up with a HST. Again this is what the DFT wanted and the civil servants wanted the laws of physics to be broken. Overall so far everything negative about them seems to be as a result of what the DFT specified and Hitachi have done the best they could with a terrible spec. Nice to see some people point blank refuse to have a single word said against them and attack anyone who has a single critical word. The one major criticism I have is simply the costs. These are massively expensive trains that just about keep up with what they are replacing and are seemingly not as comfortable. Millions and millions of pounds spent, surely in the 21st century this should have been better than this? I really hoped that I would be eating my own words and saying my cynicism was unfounded etc etc but I don't feel I have to. Well certainly on GW I don't. Remains to be seen what Virgin do with theirs on the East Coast.

So have you actually travelled on one yet? Thought not. Maybe spare us yet more of your cynicism until you have actually done so.

I take it that I am included in the category of 'some people' - yet I and others in the said category have consistently been extremely critical of the way the DfT decided to finance the IEP fleet - but you equally consistently refuse to acknowledge anything that any of us has said about the finance arrangements and keep spouting out your favourite line about how

some people point blank refuse to have a single word said against them

despite that not being the case. Or is just because we have consistently criticised your carping attacks on any and every aspect of these trains from the rails up?

As exemplified yet again here by the laughable assertion that there is hardly any luggage space. What for? Steamer trunks? Even those would fit in the bulk rooms...

And banging on about them being commuter trains - I must have missed all the space for people to stand in and the grab rails.

I don't know what you think Virgin are going to "do with theirs". Apart from some different coloured seat trim and a shop, the answer is not very much - because the DfT won't let them.

 

[Railperf]

This important point has not been extracted by anyone yet..

"However, GWR managers believe the new trains, which are being bought in two variants, one designed to serve the far west of England, the other for shorter distance routes, may struggle to reach their maximum 125mph speed when they run on diesel. “The DfT and Hitachi are currently testing the journey times of the new trains in diesel mode,” GWR said........Hitachi said the new trains would be capable of 125mph in diesel mode. But it confirmed testing was under way to gauge journey times. “This testing accounts for a variety of factors, including acceleration rates, as maximum speed is not the only determinant of journey times,” it said.

 

[samuelmorris]

That's an interesting point since as far as I'm aware on level ground they are topping out in practice around 118, as I recall?

 

[47802]

This important point has not been extracted by anyone yet..

"However, GWR managers believe the new trains, which are being bought in two variants, one designed to serve the far west of England, the other for shorter distance routes, may struggle to reach their maximum 125mph speed when they run on diesel. “The DfT and Hitachi are currently testing the journey times of the new trains in diesel mode,” GWR said........Hitachi said the new trains would be capable of 125mph in diesel mode. But it confirmed testing was under way to gauge journey times. “This testing accounts for a variety of factors, including acceleration rates, as maximum speed is not the only determinant of journey times,” it said.

It doesn't really matter if they struggle to quite get to 125mph or not providing they can keep up with the current timings. Where once the wires are up where will 125mph be required? While even for the 802's the B&H line is 110mph so its not really an issue is it. Its only an issue if they chosen for a route where sustained 125mph running on diesel is required long term but there is no route currently where that applies and hence it wasn't in the spec, and perhaps we haven't seen what the trains are fully capable of on Diesel yet as they have been set to cope with current HST timings and nothing more.

Why is so difficult for some people to grasp that the trains are currently doing something they were not specified to do but in actual fact are managing to do it quite well

 

[Railperf]

IE what they really mean is that the planned speeded-up journey times will not be possible unless the 25kv wires available on almost all the 125mph sections of the GW area, on the route to Cardiff via Bristol Parkway and as far as Thingley junction on the Bath route (plus to Newbury for West Country services) in time for the major rewrite of the GWML timetable at the end of next year.

Sorry, i think it is clear that they mean the journeys would be slower than present rather than they will be slower than the time reductions promised next year.

 

[jimm]

This important point has not been extracted by anyone yet..

"However, GWR managers believe the new trains, which are being bought in two variants, one designed to serve the far west of England, the other for shorter distance routes, may struggle to reach their maximum 125mph speed when they run on diesel. “The DfT and Hitachi are currently testing the journey times of the new trains in diesel mode,” GWR said........Hitachi said the new trains would be capable of 125mph in diesel mode. But it confirmed testing was under way to gauge journey times. “This testing accounts for a variety of factors, including acceleration rates, as maximum speed is not the only determinant of journey times,” it said.

This is getting silly - you have been told umpteen times that these trains were never intended to work in regular operation on diesel at speeds much above 100mph yet you keep going on about it happening now as though their inability to match a purpose-built 125mph express diesel train is some fatal flaw - although this will end in little over a year and the speeded-up journey times are built on the provision of 25kv overhead power on the 125mph sections of the route - or in the case of Cardiff services beyond the end of the 125mph area and on through the Severn Tunnel into South Wales.

If you want to keep consistently ignoring the context of all this - and of that article from the FT which others can now read, no thanks to you - that's up to you, but don't be surprised when you are taken to task for it.

Clarence Yard may be able to confirm but I suspect that the 800s probably would be capable of 125mph on diesel on a consistent basis if the traction management system was set up in a particular way - a series of tests on various settings were carried out earlier this year - but the way the trains are currently set up for operational use is one agreed between the various parties involved to achieve an acceptable compromise between various requirements, notably being close enough to HST timings without running up the maintenance and fuel bills to ridiculous levels and shortening the working lives of the engines.

Sorry, i think it is clear that they mean the journeys would be slower than present rather than they will be slower than the time reductions promised next year.

Is it so hard to grasp the following and all the references to the point in time when the speeded-up journeys are due to start?

That makes it critical that electric wires are ready for use on high-speed, straight sections of the route — including the line between Didcot Parkway and Swindon and Swindon and Bristol Parkway — in good time for the planned start of faster services.

 

[samuelmorris]

Is not the most relevant comparison the performance figures to reach, say, 80mph and back to zero for shorter station intervals?
If the acceleration is of concern above 50, this would surely be where the long term issue may lie.

 

[Sean Emmett]

'Hardly any luggage space'.

There's isn't as much space at the coach ends for larger luggage items compared with HST.

But the overhead luggage racks are a decent size and represent a welcome reversal from trend (class 175 the worst!) to make them too small to be useful.

Is this a conscious reversal of policy i.e. better pax keep more of the baggage with them for security reasons and reduce dwell times, compared with risk of luggage flying all over the place in a collision? If the racks had covers as in an aircraft then latter risk eliminated.

I'll say again, I like the train.
- Noise from diesels not intrusive
- don't mind the supposedly hard seats
- welcome the greater legroom
- like the airy atmosphere
- seats generally lining up with windows
- slightly lower seat backs mean a much better all round view
- more tables, which some prefer while others don't. Like the choice
- seat reservation system willbe good when it works.
- door operation will be ok when platform extensions are complete (why is this taking so long?)
- prefer trolley to buffet for PAD - BRI
- Not too excited by seat coverings but they can be changed, can't they.
- when on electric no time is being lost carting around those diesels as acceleration is artificially limited by DfT spec.
- all bi modes mean diversions via Glos and Berks Hants possible, much better than a bus on the M4.

But after all those positives, sorry, its underpowered on diesel. On GWML yes that won't matter if and when we get electrification through to Bristol.

On other routes will be interesting so see how they cope esp if the Highland Chieftain has its engines limited to 750hp.

 

[Railperf]

This is getting silly - you have been told umpteen times that these trains were never intended to work in regular operation on diesel at speeds much above 100mph yet you keep going on about it happening now as though their inability to match a purpose-built 125mph express diesel train is some fatal flaw - although this will end in little over a year and the speeded-up journey times are built on the provision of 25kv overhead power on the 125mph sections of the route - or in the case of Cardiff services beyond the end of the 125mph area and on through the Severn Tunnel into South Wales.

If you want to keep consistently ignoring the context of all this - and of that article from the FT which others can now read, no thanks to you - that's up to you, but don't be surprised when you are taken to task for it.

Clarence Yard may be able to confirm but I suspect that the 800s probably would be capable of 125mph on diesel on a consistent basis if the traction management system was set up in a particular way - a series of tests on various settings were carried out earlier this year - but the way the trains are currently set up for operational use is one agreed between the various parties involved to achieve an acceptable compromise between various requirements, notably being close enough to HST timings without running up the maintenance and fuel bills to ridiculous levels and shortening the working lives of the engines.



Is it so hard to grasp the following and all the references to the point in time when the speeded-up journeys are due to start?

I totally agree these trains are now being used in a way that they were not intended to. That has never been the issue. It is clearly the delays in electrification are causing GWR to have to use them in diesel mode over sections of route that they should have been running in electric. And yes - although Hitachi have said these trains are capable of 125mph - and in practice we have seen reports of 121/122mph, the lack of power available at the wheels to accelerate from 50mph upwards (in diesel mode) means that these trains are struggling to meet some of the timings. Thankfully the current timetable is not taxing even for an HST - and often we see these run at 110-115mph and easily maintaining the gross timings.
I totally agree that as soon as the wiring is energised as far as Bristol and Cardiff, the situation will be different and we hope to start seeing the journey time improvements promised.
The issue i am pointing out here is not limited to sections of 125mph track. We have seen that an IET does have an initial acceleration advantage over an HST - to around 50mph. But IET is going to lose time on every section of track where speed has to be reduced from maximum linespeed to 50mph and back again - whether that be TSR's, restrictive signal aspects, etc. And on every adverse gradient where line speed is over 50mph, the IET is going to take longer and lose time over an HST to reach its maximum speed.
There are huge swathes of route between London and Devon where less than 125mph is needed but much more than 50mph, and it will be interesting to see how IET's meet that challenge. Also the route to the hilly Cotswolds has its challenges and will not be wired with 25Kv either. Based on the performance we are seeing, it is clear to say that there is concern as to whether the IET in its current specification - was the best choice of train for those routes. MY gut feeling is that the installed diesel power to weight ratio should have been specified closer to Voyager/ Adelante levels.

 

[Railperf]

Is not the most relevant comparison the performance figures to reach, say, 80mph and back to zero for shorter station intervals?
If the acceleration is of concern above 50, this would surely be where the long term issue may lie.

Yes - exactly. IET has a greater advantage from station stops to 50mph over an HST, but less so from signal stops. HST's tend to be driven out of the station in notch 3 and opened up to notch 5 once clear of the station platform to minimise noise levels. But from a signal stop, HST's are typically 15 to20 seconds faster to 50mph because drivers increase power to notch 5 more quickly.

 

[doa46231]

I'm worried about 'jimm'!
He seems to be under the impression that the new trains are animate objects and that if they hear criticism of themselves they'll go into a sulk and refuse to run.

He accuses people of being somewhat overheated in their approach to these trains, and yet can barely contain his anger at any suggestion they might not be what everyone approves of.

The trains cant be blamed for any inadequacies. The fault lies with Network Rail and the DfT.
Hitachi are making the best of a bum deal.
What some of us are expressing, much to the annoyance of some on here, is disappointment that we are getting trains that might just be able to keeep to a timetable introduced 40 years ago!
That certain aspects of passenger comfort leave somethings to be desired, that taxpayers money is being spent, for whatever reason, on trains that are too heavy, too slow, too expensive to buy, run and maintain, and that will be with us for the next 30 years!

We have a perfect right to express these views, and furthermore that the people really respnsible for this fiasco are still in post.
I maintain, that anybody, and I mean anybody would have looked at the design of that catenary, and said, no way!
Nowhere in the world has such monstrous structures to hold up a bit of wire.
I realize all sorts of reasons will be advanced by 'experts' that I'm talking rubbish, but I'm one of these poor souls addicted to the metafilter website where one can enjoy cab rides in trains all over the world.
I have yet to see anything like the parade of ship docking cranes that disfigures the GWR main line.
I thought the folk in the Thames Valley were being NIMBY's when they complained about it but having seen it I can sympathise with their objections.
It also allowes Grayling to talk about 'ugly masts' spoiling the view in the National Parks!

Even NR seem to have got the message, sice according to Modern Railways Mag, new designs are being advanced.

 

[Railperf]

I have yet to see anything like the parade of ship docking cranes that disfigures the GWR main line.

Love it - best bit of humour on this thread so far hahaha - you gotta laugh - even tho ever so slightly off topic

 

[Railperf]

For trains running for extended periods off the wires - I.E to Cornwall, Cotswolds, Aberdeen, Inverness etc, the specification should have been enough installed power in diesel mode (power to weight ratio) to match a Class 180 or 220/1/2. In this case you only needed enough installed electrical power to run at 110mph from Paddington to Reading. Some might be spitting feathers at this point, but even a class 50 with 8 Mk1's in tow could do Paddington to Reading in 26 minutes, only 1 minute more than the current schedule lol ** Correction - just noted that a Class 47 with 7 coaches managed a 25 min 8 second run -with suspicions of slightly higher than allowed maximum speed for the loco. **

 

[swt_passenger]

I totally agree these trains are now being used in a way that they were not intended to. That has never been the issue. It is clearly the delays in electrification are causing GWR to have to use them in diesel mode over sections of route that they should have been running in electric...

Please also note, in addition to jimm's points above, that this thread has been running for some years and is nearly up to 6000 posts. Apart from your very useful graphical analysis, you are preaching to the converted - perhaps if you took a breath and realised that everything has been discussed multiple times already, instead of writing as though you are the first to ever notice the issues?

 

[coppercapped]

GWR's fears look like they were well funded. Great Western Railway warns of slower journeys on new trains

As others have pointed out, this article was published a year ago and concerns the delay in the electrification work on the Western.

The critical sentences read:

Rail journeys between London and the west of England and south Wales risk becoming slower when new trains are introduced in 2019, unless Network Rail keeps to its timetable to electrify services, the railway company that runs the services has warned. Great Western Railway said electrification of the line was critical because the new trains, which can run on electric or diesel power, might be slower than existing ones when they run on diesel...
...Hitachi said the new trains would be capable of 125mph in diesel mode. But it confirmed testing was under way to gauge journey times.

It may well be than the Class 800 and 802 trains do not have the mid- and upper-range performance of an HST, but given the Great Western's route structure - that of a heavily used trunk between Paddington and Reading followed by a series of branches thinning out to a range of small and medium-sized towns and cities not all of which outside the peak periods require a full length train from Paddington - how else would the problem be solved?

This is a debate which keeps recurring because some can't agree that the solution selected is good enough.

It is clearly impossible to electrify the whole Great Western network at once because of limitations in the supply of design and installation skills, finance, access to the route for the work, schedules for signalling immunisation and so on. With the best will in the world the route has to be electrified bit by bit - which then means a solution has to be found for running through trains off the electrified sections to the un-electrified sections. In principle there are three possibilities:

1. bi-modes
2. locomotive changes at the boundaries
3. adding a diesel locomotive to an emu.

The first has the well known limitation that a bi-mode is a slightly overweight EMU as well as being, in the current form, an underpowered DMU.

Point (2) requires headshunts, spurs or sidings to hold the diesel and electric locomotives at the changeover points so there are additional costs in trackwork and signalling and possibly compromises in track alignment. A delay will be built into the timetable for the changeover process even if Dellner/Scharfenberg couplers are used. Depending on the traffic pattern the locomotives and crews may have to be inefficiently rostered. Powerful locomotives have axleloads of around 20 tonnes which means that the maximum economic train speed will be around 200km/hour. If and when the electrification is extended then the infrastructure at these changeover places will become redundant.

The third possibility simplifies the changeover process compared to (2) but then means the train weight on the unelectrified sections is greater than it need be because of the mass of the transformers, control gear and traction motors. In other words it is the same situation as (1).

In any event many observers lay too much store in the weight of the train. Trains have very low rolling resistance compared to rubber-tyred vehicles and mass does not generally affect the top speed attainable on level track for a given train type - certainly 7, 8 and 9 coach long HSTs can all reach 125mile/h. Mass certainly does affect the acceleration as Isaac Newton observed and it also affects track wear, but not linearly. This is not to say that the total mass can be disregarded as obviously it affects the track foundation and bridge loading - but the extra couple of tonnes per axle between a Class 800 compared to an 801, some 12 or 14%, will not increase the track wear by the same ratio.

So, how could the power-to-weight ratio of the trains running in diesel mode be increased given the other business, operating and engineering constraints? MTU's underfloor 1600 engine maxes out at 940bhp at the moment and more than 1000bhp while meeting the Euro emission requirements seems unlikely from any other manufacturer. So either an above floor engine is needed, which cuts into passenger accommodation for a given train length, or extra coaches are fitted with the diesels. In which case where are the pantographs and transformers needed for electric operation to be fitted?

All engineering is compromise. One just has to hope that the most appropriate, or at least the least damaging one, has been chosen.

 

[Noddy]

One query I have is how the ‘re-tuning’/‘re-gearing’ has impacted the overall acceleration of the GWR sets. Bear with me as I’m not a train engineer, and I realise that I’m comparing apples and oranges BUT if I re-gear my car from 100 to 125 it will result in a significant reduction in acceleration even if I re-tune the engine to say produce an extra 25% HP. Surely this is also true of these trains even if they power an alternator/generator rather than mechanical transmission?

For example: will the acceleration curve of the Virgin sets (which will not be going above 100mph) be faster? Especially if they are governed to 0.7m/s at the low end?

 

[Railperf]

One query I have is how the ‘re-tuning’/‘re-gearing’ has impacted the overall acceleration of the GWR sets. Bear with me as I’m not a train engineer, and I realise that I’m comparing apples and oranges BUT if I re-gear my car from 100 to 125 it will result in a significant reduction in acceleration even if I re-tune the engine to say produce an extra 25% HP. Surely this is also true of these trains even if they power an alternator/generator rather than mechanical transmission?

For example: will the acceleration curve of the Virgin sets (which will not be going above 100mph) be faster? Especially if they are governed to 0.7m/s at the low end?

I understand that the gearing is the same on all sets. (pleased to be corrected if I am wrong). The engine outputs are governed by engine management software. The acceleration curve would have to be managed by some additional software that controls power the traction motors at a selected power controller position. Diesel engine management is not new. Most turbo diesel cars can be remapped to provide an additional 30% or more power and torque through a simple software remap. Lorries and trains are no different. Hence why HST's are derated to 2'250 horsepower even though their MTU engines can provide more power. But that is probably more to do with the fact that the rest of the HST traction system is not man enough to cope with the extra power. I.E traction motors etc.
I am led to believe that not long ago, Virgin West Coast derated some or all their Voyager engines from 750hp to 700hp - probably through the management system - to reduce fuel consumption and engine wear without sacrificing too much performance.

 

[D1009]

For example: will the acceleration curve of the Virgin sets (which will not be going above 100mph) be faster? Especially if they are governed to 0.7m/s at the low end?

Can someone enlighten me as to what m/s is in this context? If it's metres per second, surely that is a measure of speed rather than acceleration.

 

[Railperf]

Please also note, in addition to jimm's points above, that this thread has been running for some years and is nearly up to 6000 posts. Apart from your very useful graphical analysis, you are preaching to the converted - perhaps if you took a breath and realised that everything has been discussed multiple times already, instead of writing as though you are the first to ever notice the issues?

I'm not preaching to anyone. You are right, the thread is almost 6000 posts, but nowhere did anyone post any concrete performance figures to back their concerns about IET performance compared to the HST's. Now that these trains are running in public service and we can record their performance, we have meaningful data to support those concerns. Regardless of any of our views, IET is here, and so it will be down to GWR, Hitachi and the DfT to make it work and provide a punctual service.

 

[Railperf]

Can someone enlighten me as to what m/s is in this context? If it's metres per second, surely that is a measure of speed rather than acceleration.

Acceleration should be metres per second per second m/s/s

 

[jayah]

This is getting silly - you have been told umpteen times that these trains were never intended to work in regular operation on diesel at speeds much above 100mph yet you keep going on about it happening now as though their inability to match a purpose-built 125mph express diesel train is some fatal flaw - although this will end in little over a year and the speeded-up journey times are built on the provision of 25kv overhead power on the 125mph sections of the route - or in the case of Cardiff services beyond the end of the 125mph area and on through the Severn Tunnel into South Wales.

They were designed for Edinburgh to Inverness. If they can't match the HST on the level, the won't match it on the gradients either.

 

[aar0]

This important point has not been extracted by anyone yet..

Quite hard to, I don't subscribe to the FT...

 

[jayah]

As others have pointed out, this article was published a year ago and concerns the delay in the electrification work on the Western.

The critical sentences read:


It may well be than the Class 800 and 802 trains do not have the mid- and upper-range performance of an HST, but given the Great Western's route structure - that of a heavily used trunk between Paddington and Reading followed by a series of branches thinning out to a range of small and medium-sized towns and cities not all of which outside the peak periods require a full length train from Paddington - how else would the problem be solved?

They could always take the East Coast approach and simply miss out Harrogate, Lincoln, Scarborough, Middleborough etc... and similar irrelevant places only to have a bunch of Open Access upstarts prove they were wrong.

Talk about a sledgehammer to crack a nut. All that was needed was a Voyager type train with AC power for wherever it went that was wired. We nearly had it too on XC before DfT changed their minds.

 

[D365]

Talk about a sledgehammer to crack a nut. All that was needed was a Voyager type train with AC power for wherever it went that was wired. We nearly had it too on XC before DfT changed their minds.

Isn’t the whole point of the Class 800s that they are a step up from the Voyagers, at least in terms of passenger experience. I don’t know how many 125mph routes the Voyagers operate on where no electrification is present, but I can’t think it would be many.

 

[coppercapped]

They could always take the East Coast approach and simply miss out Harrogate, Lincoln, Scarborough, Middleborough etc... and similar irrelevant places only to have a bunch of Open Access upstarts prove they were wrong.

Talk about a sledgehammer to crack a nut. All that was needed was a Voyager type train with AC power for wherever it went that was wired. We nearly had it too on XC before DfT changed their minds.

This is getting silly - a Voyager which could also draw power from the overhead would have a lower power-to-weight ratio when on diesel than the current trains.

Bombardier made two design proposals. One proposal removed the diesel engine, fuel tank, radiators and exhaust system from one coach and replaced all of this with a transformer and the power electronics and added a pantograph. So on diesel power a 4 coach train would have three diesel engines and a five coach train would have four.

The other proposal saw an additional coach being built which would hold the pantograph, transformer and power electronics. So on diesel power a five coach train would have four engines and a six coach train would have had five.

People would have complained about this as well...!

 

[HarleyDavidson]

As others have pointed out, this article was published a year ago and concerns the delay in the electrification work on the Western.

The critical sentences read:


It may well be than the Class 800 and 802 trains do not have the mid- and upper-range performance of an HST, but given the Great Western's route structure - that of a heavily used trunk between Paddington and Reading followed by a series of branches thinning out to a range of small and medium-sized towns and cities not all of which outside the peak periods require a full length train from Paddington - how else would the problem be solved?

This is a debate which keeps recurring because some can't agree that the solution selected is good enough.

It is clearly impossible to electrify the whole Great Western network at once because of limitations in the supply of design and installation skills, finance, access to the route for the work, schedules for signalling immunisation and so on. With the best will in the world the route has to be electrified bit by bit - which then means a solution has to be found for running through trains off the electrified sections to the un-electrified sections. In principle there are three possibilities:

1. bi-modes
2. locomotive changes at the boundaries
3. adding a diesel locomotive to an emu.

The first has the well known limitation that a bi-mode is a slightly overweight EMU as well as being, in the current form, an underpowered DMU.

Point (2) requires headshunts, spurs or sidings to hold the diesel and electric locomotives at the changeover points so there are additional costs in trackwork and signalling and possibly compromises in track alignment. A delay will be built into the timetable for the changeover process even if Dellner/Scharfenberg couplers are used. Depending on the traffic pattern the locomotives and crews may have to be inefficiently rostered. Powerful locomotives have axleloads of around 20 tonnes which means that the maximum economic train speed will be around 200km/hour. If and when the electrification is extended then the infrastructure at these changeover places will become redundant.

The third possibility simplifies the changeover process compared to (2) but then means the train weight on the unelectrified sections is greater than it need be because of the mass of the transformers, control gear and traction motors. In other words it is the same situation as (1).

In any event many observers lay too much store in the weight of the train. Trains have very low rolling resistance compared to rubber-tyred vehicles and mass does not generally affect the top speed attainable on level track for a given train type - certainly 7, 8 and 9 coach long HSTs can all reach 125mile/h. Mass certainly does affect the acceleration as Isaac Newton observed and it also affects track wear, but not linearly. This is not to say that the total mass can be disregarded as obviously it affects the track foundation and bridge loading - but the extra couple of tonnes per axle between a Class 800 compared to an 801, some 12 or 14%, will not increase the track wear by the same ratio.

So, how could the power-to-weight ratio of the trains running in diesel mode be increased given the other business, operating and engineering constraints? MTU's underfloor 1600 engine maxes out at 940bhp at the moment and more than 1000bhp while meeting the Euro emission requirements seems unlikely from any other manufacturer. So either an above floor engine is needed, which cuts into passenger accommodation for a given train length, or extra coaches are fitted with the diesels. In which case where are the pantographs and transformers needed for electric operation to be fitted?

All engineering is compromise. One just has to hope that the most appropriate, or at least the least damaging one, has been chosen.

Even I've learnt something from that one posting!

I was under the impression that the 940 bhp was almost it's maximum threshold, in your view how much more power would be needed to achieve 125 mph when operating under diesel power?

 

[jayah]

This is getting silly - a Voyager which could also draw power from the overhead would have a lower power-to-weight ratio when on diesel than the current trains.

Bombardier made two design proposals. One proposal removed the diesel engine, fuel tank, radiators and exhaust system from one coach and replaced all of this with a transformer and the power electronics and added a pantograph. So on diesel power a 4 coach train would have three diesel engines and a five coach train would have four.

The other proposal saw an additional coach being built which would hold the pantograph, transformer and power electronics. So on diesel power a five coach train would have four engines and a six coach train would have had five.

People would have complained about this as well...!

The current Voyager is 750hp and the IET is over 900hp in the coaches with engines.

Plenty of headroom and also plenty of space in the end cars. Also worth remembering the 5 car Voyagers used to go around with 1 engine set to idle to save fuel.