Do HSTs still run at 125mph?

[brad465]

Is there not a section of 125mph between Edinburgh and Dunbar?

There is, but it may also be the shortest 125mph stretch in the country, so wouldn't be surprised if most trains, let alone HSTs, don't get to 125mph there.

Ignoring Train Sim for a moment....

GWRs HSTs are, in 4car formation, restricted to 100mph due to braking force. As a result, its almost impossible to arrive at Highbridge on time, as they use the old 2+8timings so expect you to hit 110, but you can't.

GWR HSTs are restricted to 100 anyway, so that won't make a difference there.

Only XC run regular scheduled HST passenger trains at 125mph.

Fair enough, do we know what the minimum length for 125 operation is? If GWR decided to extend them to 5 carriages one day (like Scotrail have considered), and this was enough then that would overcome this, but at the same time I imagine the slower they run at, the more reliable they are, which matters a lot for 45 year old stock.

 

[tiptoptaff]

There is, but it may also be the shortest 125mph stretch in the country, so wouldn't be surprised if most trains, let alone HSTs, don't get to 125mph there.



Fair enough, do we know what the minimum length for 125 operation is? If GWR decided to extend them to 5 carriages one day (like Scotrail have considered), and this was enough then that would overcome this, but at the same time I imagine the slower they run at, the more reliable they are, which matters a lot for 45 year old stock.

I don't have the reduction table in front of me but I believe it's 2+7

2+5 and 2+6 are I think 110

I'm sure my controller colleagues would be able to correct me where appropriate

Surely the much better acceleration of the 2+4 sets would cancel out the lost top speed over such a relatively short distance?

So you'd think, but it's a guaranteed loss of a minute or 2

 

[Darandio]

I don't have the reduction table in front of me but I believe it's 2+7

2+5 and 2+6 are I think 110

Then how were Grand Central blasting around at 125mph for over a decade?

I'm sure @43096 has posted previously that this whole brake force thing as a complete myth.

 

[hexagon789]

Is there not a section of 125mph between Edinburgh and Dunbar?

Yes, but it's not really

Surely the much better acceleration of the 2+4 sets would cancel out the lost top speed over such a relatively short distance?


It's hard to see Crosscountry not being tempted to replace them with the 222s when they become available.

While I would agree that would seem logical I'm not yet convinced that is what will happen. We will see
long enough for an HST to achieve 125, indeed even a 91+Mk4 will struggle to achieve 125 before having to brake to 110 or 100 depending on direction and which 125 section it is. I think the longest is only about 3 miles which is not a lot of distance to accelerate to 125 from 100 or 110 and then brake to the lower limit again.

Then how were Grand Central blasting around at 125mph for over a decade?

I'm sure @43096 has posted previously that this whole brake force thing as a complete myth.

After the original two-stage braking was isolated in conjunction with modifications to the disc braked mountings and the brake pads, there was indeed no need to restrict even theoretically a single power car. However, FGW modified its power cars to have reduced braking force as with a light and short application the power cars were doing most of the braking and were using up brake pads very quickly.

By reducing the maximum brakeforce it meant the proportion of braking effort was more equal between power cars and trailers during a short light application with the trailers retaining the higher brakeforce levels.

This is almost a revision to the original two-stsge set-up where the power cars brakeforce was reduced at over 90mph.

The effect is that GWR and ScotRail sets can only run at 125 with 5 trailers I understand, 4 is 100, 3 is 90, 2 or less is 75.

 

[JonathanH]

It's hard to see Crosscountry not being tempted to replace them with the 221s when they become available.

Corrected for you. Forget about seats, they can couple a 220 on for the busy bits.

On the 125mph point, why are the timings in RTT for GWR set as 110mph. Is this simply because those exist and 100mph timings don't. Why time for anything faster than a 158 at 90mph on the GWR workings in any case, given there would then be common timings on 158 and HST services in line with them sharing much of the relevant work?

 

[craigybagel]

So you'd think, but it's a guaranteed loss of a minute or 2

Interesting and surprising. Learn something new every day!

Corrected for you. Forget about seats, they can couple a 220 on for the busy bits.

It didn't need correcting, I meant the EMR 222s which (should) be available relatively soon. Granted though the Avanti 221s will also be available further down the line.

 

[43096]

Then how were Grand Central blasting around at 125mph for over a decade?

I'm sure @43096 has posted previously that this whole brake force thing as a complete myth.

And EMR ran a trial of a 2+4 set at 125mph.

There was a thread on it at the time: https://www.railforums.co.uk/threads/mml-2-4-hst-trial.197985/

 

[Domh245]

It didn't need correcting, I meant the EMR 222s which (should) be available relatively soon. Granted though the Avanti 221s will also be available further down the line.

Both fleets will become available at about the same time, if anything the 221s will have a slight advantage. The replacement Hitachi fleets for Avanti are due delivery in "2022", EMR are due in service "2023" - assuming XC can only have one or the other, it would make sense to go for the 221s though I wouldn't be surprised if both fleets wind up at XC in fullness of time

 

[Wyrleybart]

Both fleets will become available at about the same time, if anything the 221s will have a slight advantage. The replacement Hitachi fleets for Avanti are due delivery in "2022", EMR are due in service "2023" - assuming XC can only have one or the other, it would make sense to go for the 221s though I wouldn't be surprised if both fleets wind up at XC in fullness of time

Ex Avanti 221s would be more logical because they are compatible with the existing XC fleet, except that XC 221s have TASS removed and drivers decompetised. Replace the Avanti 221 tilt gear with rigid bars and they would be fine. Don't forget that in the last few years two ex XC non driving cars have been inserted into AWC 221s whilst 221144 had it's tilt removed when it became an XC unit.

AIUI both Avanti 221s and EMR 222s are being replaced by Hitachi units which are in build at the moment.

 

[craigybagel]

In any case, there is clearly no shortage of 125mph capable DMUs available in the next few years to finally see off the XC HSTs.

 

[30907]

The layout isn't even necessarily the most important factor. What's underneath the track, the types of fixtures, and the general maintenance regime are all pretty important. Depending on the signalling you have also going faster does not necessarily even save time.

Was there not originally the issue that 125 required a secondman (sic) whereas 110 could run without? The GW WofE route initially operated at 110 East of Reading for that reason, and there would have been little or no point in fettling the track and signalling for 125 in Somerset.

 

[hexagon789]

Was there not originally the issue that 125 required a secondman (sic) whereas 110 could run without? The GW WofE route initially operated at 110 East of Reading for that reason, and there would have been little or no point in fettling the track and signalling for 125 in Somerset.

Originally anything over 100 required a second driver, this was later negotiated to 110 by BR. 125 with single manning only came about with privatisation.

 

[zwk500]

On the 125mph point, why are the timings in RTT for GWR set as 110mph. Is this simply because those exist and 100mph timings don't.

I'd hazard a guess at this being the reason.

Why time for anything faster than a 158 at 90mph on the GWR workings in any case, given there would then be common timings on 158 and HST services in line with them sharing much of the relevant work?

Timing for an MU may cause TRUST/TOPS allocation issues with the HSTs being considered Loco + Set. Not sure about that, somebody else will be able to clarify. They also might have sufficiently different acceleration profiles in critical areas to make it better to keep the timed differently.

 

[Townsend Hook]

The NMT currently has brakes isolated on a couple of axles so runs at 10mph below line speed, so effectively limited to 115mph.

 

[73128]

Surely the much better acceleration of the 2+4 sets would cancel out the lost top speed over such a relatively short distance?


It's hard to see Crosscountry not being tempted to replace them with the 222s when they become available.

More likely to be the compatible Avanti class 221s which should be available fairly soon. Class 222 would probably require some driver and crew training - and can they couple in service?

 

[JonathanH]

Class 222 would probably require some driver and crew training - and can they couple in service?

The HSTs can't couple in service. It really isn't the biggest issue.

However, it is very hard to see a net increase of more than 15 units (eg 20 221s less 5 HST sets) being provided for which is the more pertinent point.

Either way, make the most of HSTs running at 125mph while we can because the path to their withdrawal on the remaining services where this happens is clear.

 

[DarloRich]

The NMT currently has brakes isolated on a couple of axles so runs at 10mph below line speed, so effectively limited to 115mph.

Good point - should have mentioned that in my post.

 

[MattRat]

It's hard to see Crosscountry not being tempted to replace them with the 222s when they become available.

Even though they need the capacity boost of running both trains.....

 

[Royston Vasey]

The HSTs can't couple in service. It really isn't the biggest issue.

However, it is very hard to see a net increase of more than 15 units (eg 20 221s less 5 HST sets) being provided for which is the more pertinent point.

Either way, make the most of HSTs running at 125mph while we can because the path to their withdrawal on the remaining services where this happens is clear.

Pragmatically, 20 x 221 sets might also, theoretically and with some reengineering and refurbishment, supply up to 60 middle trailers for lengthening without needing dual staffing.