Maximum speed of HST with one dead power car

[mp01]

Hmmm, title says it all really. So, assuming some kind of normal passenger loading in a 2+8 formation, what's the approx top speed of an HST with one dead power car?

Years ago as a young enthusiast, I heard that if an HST was running on only one power car, it was better that it was the back one. Is this true? And if so, does that relate to acceleration or top speed? my understanding of physics can't understand how it would make the slightest difference.

 

[The Planner]

FGW have several ECS moves timed as using one power car only as an economy measure.

 

[richw]

slightly off at a tangent, I was on a recent service where a FGW HST failed, and it missed stopping at a couple of stations Bodmin Parkway being one of them due to the incline after stopping meaning 1 engine cant get the power to pull away up the hill

 

[mp01]

Interesting. Does (or could?) FGW also run some of its slower late night trains, or anything into Wales west of Bristol Parkway with only one power car? I'm pretty sure we didn't lose any time the other day between Parkway and Newport on one engine.

 

[driver9000]

slightly off at a tangent, I was on a recent service where a FGW HST failed, and it missed stopping at a couple of stations Bodmin Parkway being one of them due to the incline after stopping meaning 1 engine cant get the power to pull away up the hill

There are instructions for single engined HSTs on the lines towards Inverness which says the train must be given a clear run over certain summits because if they were to stop they won't be able to restart.

 

[The Planner]

No, only ECS moves are timed as one engine and not all of those are. You won't lose a hideous amount of time as the only significant hill is the other half of the tunnel, I expect there is engineering recovery on the approach to Newport that would have hid any time loss.

 

[Turbostar]

I know for a fact with FGW's HST sets, depending on where it is, it won't be permitted to operate on one power car, & assistance would be required with a loco up front. Classic example is to & from Plymouth, because of Hemerdon Bank. Think a similar situation exists in Cornwall as well.

 

[Hairy Bear]

HST on one power car only reach 100mph. Utter rubbish.We regually reach 110mph on one power car even on the MML.It just takes longer getting there. With only one healthy power car, we can only loose about 12mins ,london to Sheffield.

 

[NSEFAN]

In the summer of 2006, when Virgin XC were hiring a Midland Mainline HST to work a SO Manchester Piccadilly - Newquay service. One of the power cars had failed, and the train was about 2 hours late at Plymouth! It was announced shortly after departure from Plymouth that we would not run to Newquay due to the train not being able to make the gradients, and instead it ran straight through Par and terminated at St Austell. The passengers were transfered onto coaches.

 

[richw]

NSEFAN i assume this will be due to better road links from st austell over Par,

 

[heart-of-wessex]

I know for a fact with FGW's HST sets, depending on where it is, it won't be permitted to operate on one power car, & assistance would be required with a loco up front. Classic example is to & from Plymouth, because of Hemerdon Bank. Think a similar situation exists in Cornwall as well.

Are you thinking of Totnes? I know they skip out Totnes when on one PC towards Plymouth and will gain a run up to the bank via the Through road.

 

[Old Timer]

Hmmm, title says it all really. So, assuming some kind of normal passenger loading in a 2+8 formation, what's the approx top speed of an HST with one dead power car?

Years ago as a young enthusiast, I heard that if an HST was running on only one power car, it was better that it was the back one. Is this true? And if so, does that relate to acceleration or top speed? my understanding of physics can't understand how it would make the slightest difference.

There is no restriction on speed its simply that two power cars are required to reach 125 mph for regular service running.

With regards to the rear power car question, I suspect there is confusion in that the rear power car engine used to idle faster (probably still does) because that was the one supplying the power for the on board services.

With regards to running on one power car, HSTs on one power car are not allowed to run up the Lickey but run via Kidderminster and Stourbridge instead.

 

[The Planner]

HST on one power car only reach 100mph. Utter rubbish.We regually reach 110mph on one power car even on the MML.It just takes longer getting there.

I was puzzled at that one too, glad you clarified it as the one engine moves we time are up to 125mph !!

 

[junglejames]

I was puzzled at that one too, glad you clarified it as the one engine moves we time are up to 125mph !!

Backing The Planner up, I have heard, from someone that drives HSTs, that on one power car a HST will still manage 125. The only difference is it will take longer to reach 125, and also you need to keep the engine at full power more than usual to keep at 125. If on 2 power cars you rarely need to keep the engine at full whack once at 125.

 

[richw]

I know for a fact with FGW's HST sets, depending on where it is, it won't be permitted to operate on one power car, & assistance would be required with a loco up front. Classic example is to & from Plymouth, because of Hemerdon Bank. Think a similar situation exists in Cornwall as well.

I was on a service within the last few months that ran from penzance to Plymouth on one power car without any assistance. It was terminated at Plymouth where we were transferred to another train.

 

[E&W Lucas]

There is no restriction on speed its simply that two power cars are required to reach 125 mph for regular service running.

With regards to the rear power car question, I suspect there is confusion in that the rear power car engine used to idle faster (probably still does) because that was the one supplying the power for the on board services.

Correct in that there is no restriction. Also about the ETS normally being supplied from the rear loco.

Quite capable of reaching 125 on one loco. Downhill... Eventually!!

 

[DaveNewcastle]

Much of the answer to this depends on the gradients.

A full-length HST running UP from Inverness developed intermittent problems from one PC on the climb to Slochd Summit. There was then a further slight delay due to a fault at the loop into Carrbridge of, say, 5 mins.
Despite then having to face the climb up to Drumochter (the highest point on the UK mailines for the benefit of anyone here who was unlikely not to be aware!) on one PC, and then down to Perth, Stirling and Falkirk, it managed to regain most of its lost time until reaching the densely timetabled approaches into Edinburgh, arriving about 12 down IIRC.

 

[Barrett M95]

Interesting that they struggle so much on one power car, but when you think about it, they are "only" 2250hp per end, which isn't so much when you have an up gradient and a 200km/h limit.

I remember 373/2's running with GNER that could keep to timetable on a single power car (and did on many occasions when one pantograph had ADD issues). I even remember accelerating UP Stoke bank on one power car to the point where we had to use rheo to back it off.

Although I suspect this is a case of the 373 being overpowered for this particular job rather than an HST being underpowered in that respect.

 

[LE Greys]

Yes, one end only is still a Type 4, but tractive effort is down to 17,980 lbf. That's almost exactly the same as a GWR City-class, so not very much, and combined with high gearing. Getting nine MkIIIs and a dead power car up to speed with that is going to be a hard effort, and I've heard of occasions when one power car fails, then the other one expires because it's been pushed too hard to keep time. I'm sure they could hit full speed - eventually. Thing is, how long can they sustain it? Maybe holding at 100 is to avoid over-stressing the engine.

 

[mumrar]

I believe Eurostars have a total max output of 16000 HP, so 8000 is more than competent for any traditional lines.

 

[Yew]

maybe its just that assuming 100mph max speed is a nice anolog for the redoced acceleration time? (and possible loss of speeds over hills)

 

[harz99]

Yes, one end only is still a Type 4, but tractive effort is down to 17,980 lbf. That's almost exactly the same as a GWR City-class, so not very much, and combined with high gearing. Getting nine MkIIIs and a dead power car up to speed with that is going to be a hard effort, and I've heard of occasions when one power car fails, then the other one expires because it's been pushed too hard to keep time. I'm sure they could hit full speed - eventually. Thing is, how long can they sustain it? Maybe holding at 100 is to avoid over-stressing the engine.

From memory in ICEC days the norm was one HST power car = 100mph running. Presumably for the reasons above - a fully loaded HST (as they often were) is a much different load to an ECS, and probably for a more sustained period as well.

Still, at least they didn't normally sit down in those circumstances!

 

[Turbostar]

On paper, any one power car set 'should' be hauled between Exeter and Plymouth, in reality if the train is going west and does not stop at Totnes AND under good rail conditions it will be allowed to run forward.

Might I add as well, this procedure usually occurs if no immediate availability of 2 power cars from Laira, you need 2 power cars in that 1 is the replacement for the failed one, & the other is to run back to back with the other, they very rarely run on their own en route to a power car change. If they're changing in Plymouth, if no spare power car is available to run with the replacement, the depot shunter will usually run with the replacement, & bring back the duff one back to Laira.

 

[hello]

regards to the lickey, they can go up it on one pc but must have clear run from oddingly

 

[truckman060473]

regards to the lickey, they can go up it on one pc but must have clear run from oddingly

could you explain how one power car could manage the Lickey which is 1:37 gradient when my friend was told before by a FGW driver that a Carmarthen to Swansea HST service would not manage Cockett bank on one engine and that is approx 1:50 gradient?

 

[Rugd1022]

could you explain how one power car could manage the Lickey which is 1:37 gradient when my friend was told before by a FGW driver that a Carmarthen to Swansea HST service would not manage Cockett bank on one engine and that is approx 1:50 gradient?

If I can jump in here.... it might be because the Lickey is virtually dead straght from top to bottom, apart from a very slight curve at each end. If it had continuous curves like the South Devon / Cornish Mainline etc there would be more resistance to impede progress uphill. I work class 6 freights up and down the Lickey and am usually down to about 20mph with a thousand tons in tow, I've never driven a HST up the bank but imagine that with a good run up a single power car should be ok. Having said that, I've been up it in the cabs of several Voyagers when I learnt the road, and one or two of them struggled a bit!

 

[truckman060473]

A train passing through Gowerton station non stop (HST does not stop here) I would guess the train would be able to hit the foot of Cocket bank at maybe 50-60mph. Not sure. There is a slight left curve approaching the bank.

 

[Pinza55007]

I was on a day's HST bashing a few years back, when the GNER HST I was on failed at Cheltenham with a electrical fault.It was arranged for it to work via Kidderminster to get to Birmingham.As soon as we had the OK for this, the power car started working properly again! The Guard was a fellow enthusiast and admitted to me privately (I was the only one in first) wanting to have an HST via this route.Had he admitted this to the rest of the train they would probably (metaphorically) have torn him limb from limb as there were many on board worried about missed connections at New Street.We got routed via Droitwich and New Street arriving about an hour late, and everywhere we went people and rail staff were hurriedly getting their cameras out to photograph out train.

The only time I was ever on an HST running on one power car was on the Midland Main Line in 1994, when the rear power car was the only one running.The run was made the more memorable when I was leaning out of the window at Kettering, when lightning struck the ground in a field 100 metres away from the train.I reckon the performance was roughly on a par with a 47 and seven mark 2's from what I could remember (we got 110mph down Sharnbrook- rather faster than a 47 although this was not entirely unknown in pre-OTMS BR days)

 

[hello]

theres nothing to explain apart from thats just how it is, has been for years. picks up a slip of paper at cnm which guarantees you a clear run from oddingly

 

[ainsworth74]

I was on a day's HST bashing a few years back, when the GNER HST I was on failed at Cheltenham with a electrical fault.It was arranged for it to work via Kidderminster to get to Birmingham.

When did GNER serve Birmingham or do you mean a GNER HST loaned to another TOC?