A bit of fun.....HST v 87/90 performances

[GS250]

Always been interested in relative performance envelopes of locomotives.

So, with the same driver at the controls, the same conditions, loco's not allowed to exceed maximum design speeds. Load is the same. Which would get there first?

1) Paddington to Reading non step.
2) Euston to Glasgow non EPS limits. Calling at Crewe, Preston and Carlisle.

Its all hypothetical but would be interested in who the winner would be. Just to amend these are two separate 'races' with each loco involved in both.

 

[hexagon789]

Always been interested in relative performance envelopes of locomotives.

So, with the same driver at the controls, the same conditions, loco's not allowed to exceed maximum design speeds. Load is the same. Which would get there first?

1) Paddington to Reading non step.
2) Euston to Glasgow non EPS limits. Calling at Crewe, Preston and Carlisle.

Its all hypothetical but would be interested in who the winner would be.

Are we talking 2+8 HST vs 87/90 on 8 Mk3+DVT?

 

[mmh]

Always been interested in relative performance envelopes of locomotives.

So, with the same driver at the controls, the same conditions, loco's not allowed to exceed maximum design speeds. Load is the same. Which would get there first?

1) Paddington to Reading non step.
2) Euston to Glasgow non EPS limits. Calling at Crewe, Preston and Carlisle.

Its all hypothetical but would be interested in who the winner would be.

Eh? The Paddington to Reading train would win even if it was going at 20mph.

 

[GS250]

Eh? The Paddington to Reading train would win even if it was going at 20mph.

Yes...have amended original post. Does sound a bit dense when rereading it!

Yes, let's got for an 'in service' consist of AC loco + 8mk3 + DVT. HST is 2x power cars + 8 mk3s.

 

[hexagon789]

On the WCML - Class 87 because it accelerates the fastest. Followed by the 90.

On the GWML it's harder to say - the 87/90 has superior acceleration going for it with its much greater power but the HST can do 125 and has slightly keener brakes, so can start to claw back the 87s/90s initial advantage but the question is how much distance does an HST need to "overtake" a 110mph 87/90 when it's running 15mph faster but accelerates more slowly?

 

[GS250]

On the WCML - Class 87 because it accelerates the fastest. Followed by the 90.

On the GWML it's harder to say - the 87/90 has superior acceleration going for it with its much greater power but the HST can do 125 and has slightly keener brakes, so can start to claw back the 87s/90s initial advantage but the question is how much distance does an HST need to "overtake" a 110mph 87/90 when it's running 15mph faster but accelerates more slowly?

I guess the only thing in the HSTs favour on the WCML would be if the railhead conditions were foul on the Northern steeper graded sections?

Probably a better comparison would be 90 v HST Kings X to Peterborough. That's actually been a working as opposed to my hypothetical scenario.

 

[hexagon789]

I guess the only thing in the HSTs favour on the WCML would be if the railhead conditions were foul on the Northern steeper graded sections?

Possibly, the 87 has an anti-slip brake which the driver can use to control low-speed slip which the HST doesn't but the HST has a slightly better WSP system - it just reduces the generator field current without dropping engine revs so it can recover power quicker; the 87 backs off the tap changer and applies the anti-slip brake and is quite sluggish to stop backing off and release the brake application. The HST would probably favour better under identical conditions.

Probably a better comparison would be 90 v HST Kings X to Peterborough. That's actually been a working as opposed to my hypothetical scenario.

Difficult because I can compare a 90 vs 91 and an HST vs 91 but I don't think I've tried to find out how a 90 vs HST compares.

Certainly the 90 is a bit keener than a 91 to get going but at higher speeds the 91s superior continuous rating gives it an edge. An HST meanwhile will outdo a 91 to about 60mph, at 80 they are roughly equals but at 80+ the 91 begins to surpass the HST and certainly at 100+ the 91 really gets into its stride - advantage of electric power and the ability to maintain a higher output through the speed range. The 91 will be at 125mph about 3 mins quicker than an HST (comparing a 91+9 Mk4+DVT vs 2+9 HST).

You're welcome to deduce hypothetical HST vs Cl. 90 performance from that!

 

[Snow1964]

The HST acceleration is quite genteel compared to a class 87. It’s because the electric loco can put down more like 6000-7000 HP in short bursts (it can draw the electricity and limit is more on how hot prepared to let the motors and transformer etc get). Unlike later locos with fancy current limiting electronics it is fairly old school.

The HST can never use all its diesel power for acceleration, as some is needed for ’hotel power’ (air conditioning of carriages), so only get about two thirds the power of the 87 at wheel-rail interface.

On Paddington-Reading, the HST only has about 35 miles where it is going to exceed 110mph, not sure if that is enough to offset the faster acceleration of the electric loco. But the Op didn’t specify if it was to run on fast or relief line, and if it is latter I suspect the 87 would win by at least 5 minutes.

 

[hexagon789]

The HST acceleration is quite genteel compared to a class 87. It’s because the electric loco can put down more like 6000-7000 HP in short bursts (it can draw the electricity and limit is more on how hot prepared to let the motors and transformer etc get). Unlike later locos with fancy current limiting electronics it is fairly old school.

The HST can never use all its diesel power for acceleration, as some is needed for ’hotel power’ (air conditioning of carriages), so only get about two thirds the power of the 87 at wheel-rail interface.

On Paddington-Reading, the HST only has about 35 miles where it is going to exceed 110mph, not sure if that is enough to offset the faster acceleration of the electric loco. But the Op didn’t specify if it was to run on fast or relief line, and if it is latter I suspect the 87 would win by at least 5 minutes.

An HST power car can put put 1,868hp from the traction motors but that's simply their collective rating, as you say you have to take off hotel load and 1,770 is the usually taken continuous output anyway.

The 87 can produce 7,680hp for brief periods, 5,074hp for one-hour and 5,000 continously - by any measure the superior. It doesn't suffer reduced traction output for ETS load and it has a significant weight advantage - 83 tonnes vs 140 for two HST power cars.

 

[Helvellyn]

Not fully accurate, but what were the timings in the early 1990s for the InterCity West Coast HSTs between Euston and Crewe for North Wales services? These were still 2+8 sets. For North of Crewe you would have to look at timings for the InterCity CrossCountry services between Crewe and Glasgow that were HST operated, albeit these were 2+7 sets.

 

[notadriver]

I think railhead conditions have to be near perfect for an 87 to get its power down. An HST would be more consistent with power delivery.

 

[GS250]

Would not having to worry about neutral sections assist the HST I wonder?

 

[hexagon789]

Would not having to worry about neutral sections assist the HST I wonder?

Over an 87, by a small amount I would think. Over a 90 it's probably negligible if anything.

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I think railhead conditions have to be near perfect for an 87 to get its power down. An HST would be more consistent with power delivery.

Though an 87 at least has 39 power notches to choose from, an HST has only 5, so the fineness of control would be a lot less and getting a balance might be easier with the 87.

 

[DarloRich]

What happens if you swap out one HST power car for a class 91?

 

[LNW-GW Joint]

Not fully accurate, but what were the timings in the early 1990s for the InterCity West Coast HSTs between Euston and Crewe for North Wales services? These were still 2+8 sets. For North of Crewe you would have to look at timings for the InterCity CrossCountry services between Crewe and Glasgow that were HST operated, albeit these were 2+7 sets.

I think the Holyhead HSTs were on the same schedule as loco-hauled, as they could be operated by 87/90 and Mk3 to Crewe (and often were at weekends).

 

[jfollows]

Not fully accurate, but what were the timings in the early 1990s for the InterCity West Coast HSTs between Euston and Crewe for North Wales services? These were still 2+8 sets. For North of Crewe you would have to look at timings for the InterCity CrossCountry services between Crewe and Glasgow that were HST operated, albeit these were 2+7 sets.

1D66 HST 17:03 Euston-Holyhead was 57 minutes start-stop to Rugby, including a weave for using the Down Departure Line at Euston (now renamed, but the line underneath from the low-numbered platform side which was then relatively slow compared to today). 48 minutes to pass Weedon include 1 minute of pathing time. 1G39 17:35 E385 Euston-Wolverhampton was 49 minutes to pass Weedon with 2 minutes of pathing time. 1G38 17:15 E385 Euston-Wolverhampton was 49.5 minutes with 2.5 minutes of pathing time. All used the Down Departure Line. May to September 1992 working timetable. So the timings look similar, from this brief analysis.

PS 1G39 and 1G38 were 100mph timings.

EDIT In the up direction some unscientific reading of the working timetable gives HST and 110mph electric in the same sectional timings Rugby (pass) to Watford (stop) to Euston, and both of them are 1 minute faster than 100mph electric timings over the same section.

 

[hexagon789]

What happens if you swap out one HST power car for a class 91?

With what providing the traction? The 43? The 91? Both? Neither?

 

[DarloRich]

With what providing the traction? The 43? The 91? Both? Neither?

both. always both

 

[hexagon789]

both. always both

Of course, how silly of me to think any differently!

I mean, those combos are supposed to have been insanely quick off the mark - we'd be talking over 8,400hp short-term...

 

[DarloRich]

I mean, those combos are supposed to have been insanely quick off the mark

they were! ( not that I have much info to go on - 1 return journey as a youngster c.1989)

 

[hooverboy]

The HST acceleration is quite genteel compared to a class 87. It’s because the electric loco can put down more like 6000-7000 HP in short bursts (it can draw the electricity and limit is more on how hot prepared to let the motors and transformer etc get). Unlike later locos with fancy current limiting electronics it is fairly old school.

The HST can never use all its diesel power for acceleration, as some is needed for ’hotel power’ (air conditioning of carriages), so only get about two thirds the power of the 87 at wheel-rail interface.

On Paddington-Reading, the HST only has about 35 miles where it is going to exceed 110mph, not sure if that is enough to offset the faster acceleration of the electric loco. But the Op didn’t specify if it was to run on fast or relief line, and if it is latter I suspect the 87 would win by at least 5 minutes.

HST power cars produce 4500BHP combined. the 87/90 will be 1000HP+More than that, albeit over half the traction points.
If it was a wet,slippy autumn day I'd probably give the HST the edge, over the exact same bit of track.
Otherwise the electrics will win.

 

[xotGD]

So the HST would get there quicker if it was being dragged by a 90.

 

[hexagon789]

they were! ( not that I have much info to go on - 1 return journey as a youngster c.1989)

I've only read anecdotal evidence myself but the basic data certainly tends towards a view of sparkling performance:

Allowing for the HST PC providing ETS (~330hp full load) around 8,020hp short-term and 7,630hp continuous so it's "about" 15.2hp per tonne which is "about" 25% more than a 9-coach+DVT 225 set and "about" 75% greater than a 2+8 HST set "roughly" speaking of course. Assuming my back-of-envelope maths is all "roughly" correct

 

[GS250]

Over an 87, by a small amount I would think. Over a 90 it's probably negligible if anything.

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Though an 87 at least has 39 power notches to choose from, an HST has only 5, so the fineness of control would be a lot less and getting a balance might be easier with the 87.

What happens if you swap out one HST power car for a class 91?

As happened in the late 1980s. IET like acceleration!!

I would have thought though, that the HST would have a fair advantage going over the likes of Shap in poor conditions. 16 powered wheels when compared to 8. Has to count for something.

I think it's easy to forget though, just how fast at accelerating those 87s were. I'm sure they could have ran at 125 with the appropriate gearing etc.

 

[hexagon789]

I would have thought though, that the HST would have a fair advantage going over the likes of Shap in poor conditions. 16 powered wheels when compared to 8. Has to count for something.

Getting that power down is another matter, as I said above the HST haskess fineness of control - there are some large step changes in power between some of the notches, but an 87 has more control. Plus getting away the driver can use the anti-slip brake to notch up while arresting any tendency to wheelspin until underway if necessary.

== Doublepost prevention - post automatically merged: 21 Feb 2022 ==

I think it's easy to forget though, just how fast at accelerating those 87s were. I'm sure they could have ran at 125 with the appropriate gearing etc.

I understand some did "unofficially"...

 

[Swanley 59]

Back in the late eighties, I was regularly travelling between Edinburgh and Newcastle at weekends, and occasionally between Edinburgh and Bolton. The fastest run I experienced between Carlisle and Edinburgh was on a diverted East Coast HST on a Sunday afternoon, which rolled into Waverley only an hour behind its non-diverted scheduled arrival time.

At the time, the thing that stood out for me was just how lively was the ride up and down Beattock compared to the electric trains. Subjectively, the HST felt like it was going faster.

 

[CW2]

both. always both

When the 91s were first introduced the MK4 sets weren't ready, so they substituted for an HST powercar (class 43). The intention was for the 91 to do all the work and the remaining 43 just to provide ETS. After a few small fires, it was learned that leaving the Paxman engines on low power for extended periods caused a build-up of soot in the exhausts, hence the fires. This was solved by restoring the 43 to traction mode. Thus the hellfire 91+43 combo was born.

 

[hexagon789]

When the 91s were first introduced the MK4 sets weren't ready, so they substituted for an HST powercar (class 43). The intention was for the 91 to do all the work and the remaining 43 just to provide ETS. After a few small fires, it was learned that leaving the Paxman engines on low power for extended periods caused a build-up of soot in the exhausts, hence the fires. This was solved by restoring the 43 to traction mode. Thus the hellfire 91+43 combo was born.

Also ran with the 89 a few times I understand, it accelerated quicker than the 91 - presumably due to the lower gearing and higher short-term output. Thus such a combination might be the ultimate "hellfire" arrangement

 

[Helvellyn]

Also ran with the 89 a few times I understand, it accelerated quicker than the 91 - presumably due to the lower gearing and higher short-term output. Thus such a combination might be the ultimate "hellfire" arrangement

The extra pair of powered axles offered by the Class 89 would possibly have helped!

 

[hexagon789]

The extra pair of powered axles offered by the Class 89 would possibly have helped!

I've actually obtained a copy of some articles on HST performance written by John Heaton (of Railway Performance Society & Railway Magazine Practice & Performance column fame).

One section is on the surrogate DVT performance - apparently a 0-120mph time of just 170 seconds was recorded on one occasion! Now that IS quick.