How could MML line speeds be improved? (e.g. by using tilt)

[Bald Rick]

Moderator note: Split from https://www.railforums.co.uk/threads/mml-electrification-updates.110445/


Ultimately the MML is beset with curves, and the only way to get more speed on them now is tilt.

I still have a secret hope that the Pendolinos have a few years on the MML when HS2 replaces them.

 

[Roast Veg]

Ultimately the MML is beset with curves, and the only way to get more speed on them now is tilt. I still have a secret hope that the Pendolinos have a few years on the MML when HS2 replaces them.

How many minutes saved are we talking? Obviously we don't have EPS limits for anything other than back-of-the-envelope guesswork.

 

[AM9]

I don’t know, but I suspect aerodynamics.

== Doublepost prevention - post automatically merged: 22 Sep 2021 ==



St Albans was lifted 5 or 10mph (I forget which) a few years ago.

Ultimately the MML is beset with curves, and the only way to get more speed on them now is tilt. I still have a secret hope that the Pendolinos have a few years on the MML when HS2 replaces them.

Nice thought, but would SAC platform 3 stand any chance of making a safety case for over 100mph running given the impossibility of moving the yellow line back further?

 

[Bald Rick]

How many minutes saved are we talking? Obviously we don't have EPS limits for anything other than back-of-the-envelope guesswork.

Complete guess, but something like 2-4 south of Leicester.

== Doublepost prevention - post automatically merged: 23 Sep 2021 ==

Nice thought, but would SAC platform 3 stand any chance of making a safety case for over 100mph running given the impossibility of moving the yellow line back further?

Good point.

 

[Flying Phil]

Talking of tilting Pendolinos, the record to Leicester from St Pancras is still held by the APT-E ( the original gas turbine powered set) at just under 1 hour I believe. Of course the track was even more curvy back then....

 

[Peter Sarf]

I cling to the hope that a lower tech solution to the curves is preferable - to straighten the line. Don't need train carriages getting narrower pleasse.

 

[Hairy Bear]

Talking of tilting Pendolinos, the record to Leicester from St Pancras is still held by the APT-E ( the original gas turbine powered set) at just under 1 hour I believe. Of course the track was even more curvy back then....

Real drivers don't need that gas turbine rubbish.........

Realtime report

 

[Glenn1969]

And there's me thinking that I am just a tad cynical. However, I fear Killingworth's analysis may be absolutely spot on, given the integrity demonstrated by out elected representatives to date!

My thought as well . I'm 52 and don't see HS2 reaching Yorkshire in my lifetime

 

[edwin_m]

I cling to the hope that a lower tech solution to the curves is preferable - to straighten the line. Don't need train carriages getting narrower pleasse.

That's been done at Market Harborough, which was a particularly short and severe restriction. But I think a lot of the problem elsewhere is general curvature over longer distances, which would require realignment over miles to fix.

It isn't going to happen. But then again nor are tilting trains.

 

[Bald Rick]

I cling to the hope that a lower tech solution to the curves is preferable - to straighten the line. Don't need train carriages getting narrower pleasse.

firstly, the existing carriages (Meridians) already have a tilt profile.

secondly, straightening some of the curves is impractical. St Albans for example, then all the way from Harpenden to Luton north.

But then again nor are tilting trains.

Sadly I agree.

 

[grumpyoldman01]

How many minutes saved are we talking? Obviously we don't have EPS limits for anything other than back-of-the-envelope guesswork.

Don't know if there's a copy in the NRM or the National Archives, but at the time that InterCity was struggling to get the APT-S trains through BRs' appraisal process a study was undertaken to determine actually what the time savings from tilt would be on specific routes; the base for the comparison was the tilting APT-S train, and this was compared against the same train but with tilt removed. Obviously, the latter had a better power-to-weight ratio which gave it superior acceleration, and this resulted in the non-tilting train having a marginal quicker journey time on the ECML between Kings Cross and Waverley.

From memory, on the WCML the benefit from tilt was only really present through England's Northern Fells and over Beattock, but the route were it gave the greatest benefit of all was the MML; sorry I can't remember how many minutes tilt saved between St Pancras and Sheffield, but I remember that it did stand out from all of the other routes appraised as it gave a significant journey time reduction rather than a slight one - certainly more than the 2-4 minutes south of Leicester suggested in an earlier post .

I'm not sure how relevant an exercise undertaken over 30 years ago is to the MML as it is now, but it must have taken account of gradients, curvature, and speed restrictions which would remain such as over the Newark crossing; I say that because I recall it being explained that the superior power-to-weight ratio of the non-tilting APT-S meant that the climb north from King's Cross through the Northern Heights gave it a journey time benefit through London's suburbs, and I guess the same would apply up Stoke Bank from a Peterborough stop (although I can't recall that being mentioned), The exercise also only looked at potential journey times, and didn't take account of capacity or signalling constraints present when it was carried out

Pendolinos might not have the potential to produce significant journey time benefits over 222s or 810s, but tilting trains with identical rates of acceleration to them might be an option worth considering on the MML; but would the overhead need tweaking to accommodate such trains, and would the power supply need strengthening as well?

 

[mr_jrt]

Easy solution for the MML - remove the fast intercity trains to a new straighter route bypassing St Albans, leaving the existing tracks for local and suburban services. Could run up from London to East Midlands Parkway and then up to Newcastle via Sheffield and Leeds. Maybe call it high speed too?

...I'll get my coat.

 

[John Webb]

Easy solution for the MML - remove the fast intercity trains to a new straighter route bypassing St Albans, leaving the existing tracks for local and suburban services. Could run up from London to East Midlands Parkway and then up to Newcastle via Sheffield and Leeds. Maybe call it high speed too?

...I'll get my coat.

Blame the St Albans City Fathers of the 1860s for the St Albans curves; it was they who persuaded the MR to deviate from a straight line to get the station closer to the city centre.....

 

[edwin_m]

but tilting trains with identical rates of acceleration to them might be an option worth considering on the MML; but would the overhead need tweaking to accommodate such trains, and would the power supply need strengthening as well?

On the issue of the overhead, tilting trains have an "un-tilting" mechanism on the pantograph so it stays in the same place it would be on a non-tilting train. On the roof of a Pendolino it slides back and forth on a lateral runner which forms an arc, presumably centred on the centre of rotation of the tilt mechanism. So no tweaking needed, only the detailed and costly approval process needed whenever anything runs anywhere new.

A tilting train might in theory actually use less power (on average), as it passes through speed restrictions at higher speed so won't need to accelerate so much afterwards. It does of course brake less so regenerate less power, but that won't compensate. However, running at higher speed increases resistance losses, and the tilt mechanism itself uses some power.

 

[Bald Rick]

sorry I can't remember how many minutes tilt saved between St Pancras and Sheffield, but I remember that it did stand out from all of the other routes appraised as it gave a significant journey time reduction rather than a slight one - certainly more than the 2-4 minutes south of Leicester suggested in an earlier post .

Theres been a lot of work done to the linespeed profile on the MML in the intervening 40+ years, so the benefit of tilt will be somewhat less now than it was then.

 

[swt_passenger]

On the issue of the overhead, tilting trains have an "un-tilting" mechanism on the pantograph so it stays in the same place it would be on a non-tilting train. On the roof of a Pendolino it slides back and forth on a lateral runner which forms an arc, presumably centred on the centre of rotation of the tilt mechanism. So no tweaking needed, only the detailed and costly approval process needed whenever anything runs anywhere new.

To add to your written explanation, there’s a good photo in this thread from 2016:

Pantograph & Tilt interaction

Forgive my ignorance on this subject, but I was pondering the interaction between the contact wire on OHLE, pantographs and the use of tilting and non-tilting trains on the same lines. I assume that the contact wire stays at the same height relative to the position of the rails (with the...

www.railforums.co.uk

 

[grumpyoldman01]

On the issue of the overhead, tilting trains have an "un-tilting" mechanism on the pantograph so it stays in the same place it would be on a non-tilting train. On the roof of a Pendolino it slides back and forth on a lateral runner which forms an arc, presumably centred on the centre of rotation of the tilt mechanism. So no tweaking needed, only the detailed and costly approval process needed whenever anything runs anywhere new.

A tilting train might in theory actually use less power (on average), as it passes through speed restrictions at higher speed so won't need to accelerate so much afterwards. It does of course brake less so regenerate less power, but that won't compensate. However, running at higher speed increases resistance losses, and the tilt mechanism itself uses some power.

Thanks for the information

I knew that tilting train pantographs have an "un-tilting" mechanism, but as so much work was done on the WCML I didn't know if any changes were necessary in case they failed, and if the overhead on routes in north west England likely to be used for diversions (such as through Chorley) had been designed accordingly

Regarding power supply, in the days of BR before track and train were separated, power supply was closely matched to demand - parts of the Bournemouth-Weymouth electrification were designed around a single 442 being there at any one time; Kettering - Market Harborough is being designed after it became known that 810s are EMR's train of choice, and I just don't know how the design of the power supply is specified and if it is matched in any way to the planned train service over that line, and if it is then assumed that each could be formed of 2x5-car sets.

 

[AM9]

Easy solution for the MML - remove the fast intercity trains to a new straighter route bypassing St Albans, leaving the existing tracks for local and suburban services. Could run up from London to East Midlands Parkway and then up to Newcastle via Sheffield and Leeds. Maybe call it high speed too?

...I'll get my coat.

Said in jest of course, but consider the suggestion as a crayon exercise: a bypass including grade separation on the fasts at Napsbury and Sandridge. Total length of works around 6 miles with over 4 miles of tunnel for two fast tracks. That wouldn't be cheap, - maybe @BaldRick could take a stab at a cost for it.
But looking at the positives, - by providing a looping facility for St Albans fast stoppers, it would be possible for more services to stop there, maybe including a few of the EMUs that will provide the intermediates north of Bedford. It may even be worth turning a few fasts there in the peaks or during possessions. Then there's the fantastic journey timesaving of 7.2 seconds per mile when running at 125mph rather than 100mph now.

 

[grumpyoldman01]

Theres been a lot of work done to the linespeed profile on the MML in the intervening 40+ years, so the benefit of tilt will be somewhat less now than it was then.

From memory, it wasn't based around actual linespeeds in place at the time, but the theoretical maximum using "rules" in place back then; so if a straight section had a maximum of 90mph at that time but is 125mph now for HSTs, it would have been 125mph for both the APT-S and the non-tilting equivalent (the exercise was based around a maximum line speed of 125mph).

Where alignment has been eased - like at Wigston - obviously the original curvature was used; but I don't think what used to be referred to as "special curving rules" had been introduced at the time the exercise was undertaken, and so I guess this will have some effect upon the potential time savings from tilt

 

[Senex]

Blame the St Albans City Fathers of the 1860s for the St Albans curves; it was they who persuaded the MR to deviate from a straight line to get the station closer to the city centre.....

Indeed. Just like their Wellingborough predecessors of the 1840s who were responsible for the curve there. (The curvature through Kettering was unfortunately down to the engineers' joining togtether of two different routes.)

== Doublepost prevention - post automatically merged: 23 Sep 2021 ==

Don't know if there's a copy in the NRM or the National Archives, but at the time that InterCity was struggling to get the APT-S trains through BRs' appraisal process a study was undertaken to determine actually what the time savings from tilt would be on specific routes; the base for the comparison was the tilting APT-S train, and this was compared against the same train but with tilt removed. Obviously, the latter had a better power-to-weight ratio which gave it superior acceleration, and this resulted in the non-tilting train having a marginal quicker journey time on the ECML between Kings Cross and Waverley.

The report I saw for the MML shewed a 9 + 1 APT (3 MW power-car) taking 54.66 minutes St Pancras to Leicester assuming a line-speeed of 125 mph and the full re-alignment at Market Harborough (not the scaled-back version we've now got) but no other significant changes. Some other interesting tit-bits there , such as 22 minutes Loughborough pass to Chesterfield pass via the EV.

 

[ABB125]

The report I saw for the MML shewed a 9 + 1 APT (3 MW power-car) taking 54.66 minutes St Pancras to Leicester assuming a line-speeed of 125 mph and the full re-alignment at Market Harborough (not the scaled-back version we've now got) but no other significant changes. Some other interesting tit-bits there , such as 22 minutes Loughborough pass to Chesterfield pass via the EV.

What was the original plan for Market Harborough?

 

[brad465]

While line speeds won't necessarily improve with this, if the new 810s have improved acceleration on 222s would this cut journey times a bit (albeit I presume 222s already have good acceleration for DMUs)?

 

[Flying Phil]

What was the original plan for Market Harborough?

There is a speed restricted curve to the North of the station, which was to be eased, using land to the West of the track formation. This was cancelled to reduce the project cost I believe....

 

[43066]

Real drivers don't need that gas turbine rubbish.........

Realtime report

Nice. I find you need to be a bit late, and for Three Bridges to play ball, for those.

 

[edwin_m]

There is a speed restricted curve to the North of the station, which was to be eased, using land to the West of the track formation. This was cancelled to reduce the project cost I believe....

I don't think there was ever any plan to deal with the fairly sharp curve south of the station, and unless that could be straightened out too, the benefit of reverting to the original Midland alignment further north (instead of the later deviation to accommodate the Joint line) was only a handful of seconds.

 

[Bald Rick]

Regarding power supply, in the days of BR before track and train were separated, power supply was closely matched to demand

It still is.

Total length of works around 6 miles with over 4 miles of tunnel for two fast tracks. That wouldn't be cheap, - maybe @BaldRick could take a stab at a cost for it.

Well, I think you’re a little pessimistic on length, it would be about 4-5 miles of new railway with 3 miles in tunnel. Some of the new railway would be in flood plain (Napsbury) or land allocated for housing (Sandridge). But you’d be looking at the best part of a billion.

Where alignment has been eased - like at Wigston - obviously the original curvature was used; but I don't think what used to be referred to as "special curving rules" had been introduced at the time the exercise was undertaken, and so I guess this will have some effect upon the potential time savings from tilt

Indeed so.

 

[HSTEd]

Well if we assume HS2 at least reaches East Midlands Parkway - at that point we have an MML that has no trains beyond Nottingham in all likelihood.

With the longer distance trains largely removed, wouldn't it be easier just to simplify the timetable down to one to three stopping patterns, one per pair of tracks at any given place?

Then the platform at St Albans no longer matters because you either stop all trains there and they won't be going over 100mph on the fast line or you simply won't stop anything there and you can gate off the platform.

 

[londonmidland]

While line speeds won't necessarily improve with this, if the new 810s have improved acceleration on 222s would this cut journey times a bit (albeit I presume 222s already have good acceleration for DMUs)?

On diesel I believe a 22X would out perform a Class 80X/810 as they have very good acceleration although don't quote me on that. On electric I believe a 810 would have improved acceleration, however.

 

[Bald Rick]

Well if we assume HS2 at least reaches East Midlands Parkway - at that point we have an MML that has no trains beyond Nottingham in all likelihood.

There will still be MML trains going beyond ‘Nottingham’ (and Derby).

== Doublepost prevention - post automatically merged: 23 Sep 2021 ==

On diesel I believe a 22X would out perform a Class 80X/810 as they have very good acceleration although don't quote me on that. On electric I believe a 810 would have improved acceleration, however.

The 810s are specified to match the 222s on diesel.

 

[HSTEd]

There will still be MML trains going beyond ‘Nottingham’ (and Derby).

My rationale was that since via HS2 will likely beat the MML on travel time, the best thing to do from an operating cost perspective would be to stop all trains on both routes at East Midlands Parkway, provide interchanges there (cross platform if we can manage it) then send the MML trains to Nottingham as it is the closest load centre (Derby being the much smaller urban area and the one with the continuing route North). All service to Derby and North would then be via HS2.

Maybe I'm being a little too brutal with my rationalisation axe.