Fastest Accelerating MUs in the UK

[notadriver]

That's not a myth, I was told that on 'telly' whilst on the first scheduled 395 run by Vince Lucas of Southeastern, the train did 200km/h tops all the way from Ashford to London, I asked why they didn't at least do 225km/h for the cameras (which they said they were doing) he explained that they would only do this when late. I think things have changed as I don't recall running at much less than 225km/h since.

Yes times have been tightened up.

 

[Railperf]

Yes times have been tightened up.

Still - the evening 'fast' non stop runs from Stratford to Ashford is allowed 2 mins more than what can be achieved with a flat out 140mph run..so a 125mph max speed could potentially achieve that schedule.

 

[Samzino]

0-60 is the 345 but that's mainly due to gearing being at 100mph and that's around 36 seconds if I remember right as the previous holder was the 395 at 38seconds which remarkably is geared for 140mph yet able to pull away that fast being as well heavier. The 395 should be the fastest however 60-120mph the Eversholt graph from 60mph to 120mph is about 110 seconds (If you subtract the 148s(its not dead on 150s) - 38s). Unless there is another train that beats the 395 in both 0-60 and 60-120mph or above all round i'd say the 395 is the quickest train. I've seen the 755 is apparently faster than the 345 but I've not seen any data on that unless anyone has a recording done or some. The most I can find is that Stadler does say the 755 does 1.1m/s^2(4car) and 1.3m/s^2(3car) of acceleration between starting and 40mph which means to 40 is 16.26s on the 4 car and 13.75s on the 3 car units which is pretty quick however which might indeed mean it covers 60mph faster than the 345 but still impressive the 395 is anywhere near those two.

 

[hexagon789]

That's not a myth, I was told that on 'telly' whilst on the first scheduled 395 run by Vince Lucas of Southeastern, the train did 200km/h tops all the way from Ashford to London, I asked why they didn't at least do 225km/h for the cameras (which they said they were doing) he explained that they would only do this when late. I think things have changed as I don't recall running at much less than 225km/h since.

I meant the current (or recent anyway) situation where the 395s do normally operate at 225km/h.

0-60 is the 345 but that's mainly due to gearing being at 100mph and that's around 36 seconds if I remember right as the previous holder was the 395 at 38seconds which remarkably is geared for 140mph yet able to pull away that fast being as well heavier. The 395 should be the fastest however 60-120mph the Eversholt graph from 60mph to 120mph is about 110 seconds (If you subtract the 148s(its not dead on 150s) - 38s). Unless there is another train that beats the 395 in both 0-60 and 60-120mph or above all round i'd say the 395 is the quickest train. I've seen the 755 is apparently faster than the 345 but I've not seen any data on that unless anyone has a recording done or some. The most I can find is that Stadler does say the 755 does 1.1m/s^2(4car) and 1.3m/s^2(3car) of acceleration between starting and 40mph which means to 40 is 16.26s on the 4 car and 13.75s on the 3 car units which is pretty quick however which might indeed mean it covers 60mph faster than the 345 but still impressive the 395 is anywhere near those two.

View attachment 86910View attachment 86911

It's difficult to get more than rough figures off their graphs tbh

 

[Llama]

Do we know if the traction package on the CAF 331 is the same as on the 397?
That would explain their high speed capability (I know they are in a different bodyshell/configuration).
The electrics for both are from TSA (Traktionssysteme Austria), which also powers some Stadler EMUs (and Metrolink's trams!).

I've no idea to be honest, they do seem to make the same noises at similar speeds (phase change at ~12mph and 'burble' at ~37mph). The highest 331 speed attained that I have reliable account of (by a respected individual not known for exaggeration in the line of promotion above driver grade) was an unofficial 117mph on an ECS test/training run in 2019. Knowing the location that speed was achieved its pretty likely the unit in question (a 3-car) wasn't stretched to its limits.

Northern gave no technical info whatsoever on the 331 training course in order to dumb down the training to speed it up - conversely on the 319 and 323 full courses drivers are expected to know every working voltage of all major parts. We aren't even privy to whether the 331s have a Buchholz relay on the main transformer (if there is one, and I suspect there must be somewhere, it's well hidden).

Attached is a photo of a plate as attached to the main transformer on a 331 which has some schematic info on - please note I don't have the key to the numbered labels shown on it (nor the technical nous to decipher it all!)

 

[hexagon789]

I've no idea to be honest, they do seem to make the same noises at similar speeds (phase change at ~12mph and 'burble' at ~37mph). The highest 331 speed attained that I have reliable account of (by a respected individual not known for exaggeration in the line of promotion above driver grade) was an unofficial 117mph on an ECS test/training run in 2019. Knowing the location that speed was achieved its pretty likely the unit in question (a 3-car) wasn't stretched to its limits.

Northern gave no technical info whatsoever on the 331 training course in order to dumb down the training to speed it up - conversely on the 319 and 323 full courses drivers are expected to know every working voltage of all major parts. We aren't even privy to whether the 331s have a Buchholz relay on the main transformer (if there is one, and I suspect there must be somewhere, it's well hidden).

Attached is a photo of a plate as attached to the main transformer on a 331 which has some schematic info on - please note I don't have the key to the numbered labels shown on it (nor the technical nous to decipher it all!)

Does the "traction" bit refer to the motors? As in they operate at 1000V?

 

[Domh245]

Does the "traction" bit refer to the motors? As in they operate at 1000V?

I'm reading that as the voltage that the 4 secondary windings are at, which presumably then go to the traction electronics before then going to the motors. The motors themselves, assuming that the ones on that page are those used in the 331s as well, have an associated voltage of 1334v (quite what that voltage is, I don't know - presumably the peak design voltage?) although more interestingly a power of 220kW compared to the 450kVA (roughly) that each secondary winding provides - either there's a horrific power factor, the transformer is massively overspecced, or there's two motors driven per secondary winding

 

[37057]

Does the "traction" bit refer to the motors? As in they operate at 1000V?

I'd say it's the four secondary windings that operate at 1000v as the data plate is for the transformer only. Motor voltage will be controlled by their inverters.

 

[hexagon789]

I'm reading that as the voltage that the 4 secondary windings are at, which presumably then go to the traction electronics before then going to the motors. The motors themselves, assuming that the ones on that page are those used in the 331s as well, have an associated voltage of 1334v (quite what that voltage is, I don't know - presumably the peak design voltage?) although more interestingly a power of 220kW compared to the 450kVA (roughly) that each secondary winding provides - either there's a horrific power factor, the transformer is massively overspecced, or there's two motors driven per secondary winding

Thanks, I like to take an interest in this sort of technical information ever since I obtained a copy of a book which goes into some detail on the various parts and specifications of the Class 81-87 electric locomotives. It sort of sparked an interest in train technical minutiae

If the motors are 220kW (presumably continuous?), no wonder the 331s can shift - a three-car set would have the equivalent of about 780hp per coach to play with.

I'd say it's the four secondary windings that operate at 1000v as the data plate is for the transformer only. Motor voltage will be controlled by their inverters.

Cheers, I'm still trying to get to grips with the more recent technical developments, my book pretty much stops at 1970s thyristor technology!

 

[Snow1964]

Things have definitely moved on as you say, and the more powerful MK1 (and 2) based units were hamstrung in terms of acceleration by their higher gearing. The 309’s are a perfect example.

The 4-REPs were the exception to this but were an anomaly really and didn’t run in service without at least a 4-TC in tow
(there may have been the odd exception which would have been fun!). I always think of them as the Southern’s equivalent of a Deltic!

In terms of older units, has anybody mentioned the 487s? Only 380hp per motor coach but they ran singly or in pairs with no trailers, were light and geared for 35mph. They must have shifted from a standing start!

I used to live in New Milton, and on one occasion in early 1980s did get a 4-REP on its own on a semi-fast. I think the driver was keen as well, it was memorable, having to brake for places like Sway curve that normally would still be accelerating through (the brakes were noisy and weak by modern standards on a 4-REP). I think I read somewhere they were supposed to be limited to 60mph when on own, but clearly they weren’t.

Think there was some sort of disruption that day, as I can’t ever remember another 4-REP on its own running a service.

I think a 4-REP had 800hp/coach on 1 hour rating, probably 900+hp/coach for few minutes acceleration bursts (and there was no electronic limiters, just drivers ampmeter as a max power guide)

 

[Railperf]

Unless there is another train that beats the 395 in both 0-60 and 60-120mph or above all round i'd say the 395 is the quickest train. I've seen the 755 is apparently faster than the 345 but I've not seen any data on that unless anyone has a recording done or some. The most I can find is that Stadler does say the 755 does 1.1m/s^2(4car) and 1.3m/s^2(3car) of acceleration between starting and 40mph which means to 40 is 16.26s on the 4 car and 13.75s on the 3 car units which is pretty quick however which might indeed mean it covers 60mph faster than the 345 but still impressive the 395 is anywhere near those two.

I have recorded Class 755's and by far they are the quickest trains from rest to 100mph - and the average passenger can experience that.
The 395's are not faster to 100mph, and if they are the fastest UK MU to 125mph then the average passenger will not experience that because there is nowhere that a 395 can enjoy an unrestricted start from 0-125 or 140mph. From all the stations there are speed restrictions over switches and crossings plus neutral sections and severe gradients in places.
The 395 has the fastest service speed (140mph). I'm fortunate enough to have experienced the press and stakeholder runs that Ran St Pancras to Ashford in under 28 minutes non-stop with speeds touching 143mph in places. And I was privileged to be aboard a Stratford to Ashford service train that achieved an average start-to-stop speed of just under 120mph!

 

[hexagon789]

I think I read somewhere they were supposed to be limited to 60mph when on own, but clearly they weren’t.

Light locos were (and still are) 75mph, and as 4REPs are fully braked for their weight like other EMUs and DMUs plus have EP control which is much faster actuating than just air or indeed vacuum I don't see why they'd be poorly braked.

They should behave just like any other tread braked EMU of the time.

I think a 4-REP had 800hp/coach on 1 hour rating, probably 900+hp/coach for few minutes acceleration bursts (and there was no electronic limiters, just drivers ampmeter as a max power guide)

The figures I have are - 675V, 385A, 320hp continuous.

Presumably the oft-quoted 3,200hp per unit is the one-hour rating and thus 400hp one-hour per motor

 

[gingertom]

0-60 is the 345 but that's mainly due to gearing being at 100mph and that's around 36 seconds if I remember right as the previous holder was the 395 at 38seconds which remarkably is geared for 140mph yet able to pull away that fast being as well heavier. The 395 should be the fastest however 60-120mph the Eversholt graph from 60mph to 120mph is about 110 seconds (If you subtract the 148s(its not dead on 150s) - 38s). Unless there is another train that beats the 395 in both 0-60 and 60-120mph or above all round i'd say the 395 is the quickest train. I've seen the 755 is apparently faster than the 345 but I've not seen any data on that unless anyone has a recording done or some. The most I can find is that Stadler does say the 755 does 1.1m/s^2(4car) and 1.3m/s^2(3car) of acceleration between starting and 40mph which means to 40 is 16.26s on the 4 car and 13.75s on the 3 car units which is pretty quick however which might indeed mean it covers 60mph faster than the 345 but still impressive the 395 is anywhere near those two.

View attachment 86910View attachment 86911

would be interesting to see how this compares with an 801.

 

[Railperf]

would be interesting to see how this compares with an 801.

0-60mph in 44s, 0-100mph in 112s, 0-124mph in 187s

 

[Llama]

Thanks for the replies to the picture I posted for the 331 TX.

Each motor coach has a 'double traction converter' which supplies both bogies on that coach. I'm assuming within each traction converter case there are duplicate sets of rectifiers/inverters etc for two of the four 1000vAC inputs to supply both bogies on that vehicle. There's no provision for isolating individual traction motors or even individual pairs on each bogie - the driver can only inhibit all traction motors per coach, or restrict their output manually to 75/50/25% using the computer.

It can be seen that there are just the four 1000v secondary outputs from the main transformer too - there's no tertiary for auxiliaries as you might find on other units such as 323s, so where does the power for auxiliaries on 331s come from?

The auxiliary converters, one per motor coach, are fed from the traction converters. As I say we were given virtually no technical knowledge on the 331 training, and it always puzzled me how there was still a whine from the traction motors when say going through an overhead neutral section (OHNS) where there would obviously be no supply from the main transformer. The traction motors act as alternators (forgive my terminology, I'm not an electrical engineer) and therefore maintain a continuous feed to the auxiliary converters to keep HVAC, battery charging and all other auxiliaries supplied seamlessly. The drawback of this is that it causes drag so the 331s don't coast at all well with the vacuum circuit breaker (VCB) open such as when going through an OHNS. At the moment there's a 20mph temporary speed restriction at Slade Lane Jn immediately before the OHNS on the up Styal line, so drivers are hitting the OHNS at 20mph instead of the usual 45mph, and the 331 units are often nearly coming to a stand because of the huge delay (30+ seconds) before traction power is available once 'on the juice' again after passing the OHNS. 323s and 319s coast freely and traction power is available almost instantaneously as soon as they've passed an OHNS by comparison.

 

[Railperf]

The drawback of this is that it causes drag so the 331s don't coast at all well with the vacuum circuit breaker (VCB) open such as when going through an OHNS. At the moment there's a 20mph temporary speed restriction at Slade Lane Jn immediately before the OHNS on the up Styal line, so drivers are hitting the OHNS at 20mph instead of the usual 45mph, and the 331 units are often nearly coming to a stand because of the huge delay (30+ seconds) before traction power is available once 'on the juice' again after passing the OHNS. 323s and 319s coast freely and traction power is available almost instantaneously as soon as they've passed an OHNS by comparison.

Has anyone 'stalled' yet due to speed dropping so low? I guess if that happens the TSR speed might need to be adjusted slightly higher.

 

[Llama]

Yes 331s coming to a stand has happened, you'd think the effect of the drag would be reduced the slower you go but that's not what happens, I assume as a characteristic of asynchronous motors. It doesn't help that the automatic holding brake applies aggressively at 1mph, and that drivers were never trained that the 'pan up' button is also the VCB reset button which is useful to know if you got stopped on the 'run-out' of a neutral section. For tho readers who aren't aware, overhead neutral sections are usually around 155ft long and have live, dead, earthed, dead and live sections (different phase/supply at both live sections hence the need for them being separated, with an earthed section between them). The main circuit breaker (VCB) next to the pantograph is opened automatically at the start, and closed automatically at the exit, by track equipment similar to AWS magnets.

Incidentally 331s are capable of coasting perfectly with the VCB open, but only when they are in a condition where the motors aren't used to run the aux converters - such as the dynamic brake being isolated, DRA set on the move, or 'running brake test' button pressed.

The traction system gets confused if any of the above conditions are corrected on the move while the VCB is open - this is felt by an alarming juddering (first time I felt it I thought we'd derailed it was that bad) from the traction motors. Clearly there's a software issue, we were told it was corrected a long time ago but it can still be recreated.

 

[Samzino]

I have recorded Class 755's and by far they are the quickest trains from rest to 100mph - and the average passenger can experience that.
The 395's are not faster to 100mph, and if they are the fastest UK MU to 125mph then the average passenger will not experience that because there is nowhere that a 395 can enjoy an unrestricted start from 0-125 or 140mph. From all the stations there are speed restrictions over switches and crossings plus neutral sections and severe gradients in places.
The 395 has the fastest service speed (140mph). I'm fortunate enough to have experienced the press and stakeholder runs that Ran St Pancras to Ashford in under 28 minutes non-stop with speeds touching 143mph in places. And I was privileged to be aboard a Stratford to Ashford service train that achieved an average start-to-stop speed of just under 120mph!

Yup the 755 definitely at rest to 100mph beats the 395 as i believe you have said somewhere due to gearing and from anyway their site 0-40mph in something like 14 seconds on the 3 car electric mode is impressive. 395 actually feels like it can pull more m/s^2 as you say if given a decent run like the 755's do but even under restriction for it to be only 8-10 seconds off two very quick 100mph geared trains is impressive and would wonder how much it pulls if geared to 100mph(not realistic but for test purposes)

 

[notadriver]

Yup the 755 definitely at rest to 100mph beats the 395 as i believe you have said somewhere due to gearing and from anyway their site 0-40mph in something like 14 seconds on the 3 car electric mode is impressive. 395 actually feels like it can pull more m/s^2 as you say if given a decent run like the 755's do but even under restriction for it to be only 8-10 seconds off two very quick 100mph geared trains is impressive and would wonder how much it pulls if geared to 100mph(not realistic but for test purposes)

Indeed the 395s are very good. I think their secret is a ‘boost’ from 50 mph to around 80 mph which leaves all the usual 125 mph geared stock standing.

 

[Railperf]

Indeed the 395s are very good. I think their secret is a ‘boost’ from 50 mph to around 80 mph which leaves all the usual 125 mph geared stock standing.

But haven't the 395's been slightly derated?

Yup the 755 definitely at rest to 100mph beats the 395 as i believe you have said somewhere due to gearing and from anyway their site 0-40mph in something like 14 seconds on the 3 car electric mode is impressive. 395 actually feels like it can pull more m/s^2 as you say if given a decent run like the 755's do but even under restriction for it to be only 8-10 seconds off two very quick 100mph geared trains is impressive and would wonder how much it pulls if geared to 100mph(not realistic but for test purposes)

Not sure the 755's are geared for only 100mph. I believe the bogies are based on a standard design capable of 124mph (200kph). Usually the 200kph Flirts have an additional powered bogie to deliver the additional power required to accelerate to that speed. The 755/3's are software limited to the 100mph maximum speed. I cannot see why manufacturers would retool a standard product line when the max speed can be adjusted in software.

 

[supervc-10]

Surely the the gearing is easily switched, not requiring much changes to the bogie design?

 

[Railperf]

you make it sound like the manufacturers just walk to a shelf and pick up a few gears and swap them over lol. Changing the gearset on a bicycle is not cheap and it can be time consuming. The gearset on a train traction system is mega expensive and rarely changed. Granted - some locos have been fitted with lower gearing to improve low speed haulage performance - but these modifications can cost millions. Not going to happen on a whim. All these years we have heard people proposing to regear HST's for use on 100mph services - but the reality is it never happened. Cost and time to do it! And they accelerate pretty well with the shorter loads! So no major benefit by regearing!

 

[supervc-10]

I'm not thinking total change of a gearset that's in use- what I mean is, the Stadler trains have been developed for 100mph running here in the UK, and will have been developed from the ground up for those requirements, would it not make sense to fit the 'correct' ratios? Changing the size of the gears won't cost much when it's designed from the start. After all, there are a number of trains that have been re-geared partway through their lives.

In the same way, changing the gearbox on an already built bicycle costs money. Building a bicycle and deciding on a different set of gears doesn't cost- you were going to buy gears anyway, you've just made a different decision on which ones to chose.

 

[ashkeba]

I'm not thinking total change of a gearset that's in use- what I mean is, the Stadler trains have been developed for 100mph running here in the UK, and will have been developed from the ground up for those requirements, [...]

The FLIRT was developed for Swiss Federal Railway initially.

 

[supervc-10]

The platform, yeah. The 745 and 755 though, were developed for Greater Anglia.
The 36 train fleet of 458s was converted from 100mph gearing to 75mph, and the 334s up in Glasgow are 90mph.

 

[43096]

The platform, yeah. The 745 and 755 though, were developed for Greater Anglia.
The 36 train fleet of 458s was converted from 100mph gearing to 75mph, and the 334s up in Glasgow are 90mph.

The 460s actually had 125mph gearing, which was changed to 75mph when they were integrated with the 458 fleet.

 

[supervc-10]

125? On 3rd rail?

 

[43096]

125? On 3rd rail?

That is what gearing they had. It doesn't mean they were cleared for that speed.

 

[AM9]

That is what gearing they had. It doesn't mean they were cleared for that speed.

But it was a ridiculous waste of energy.

 

[delticdave]

But it was a ridiculous waste of energy.

Maybe not so, the motors will only use sufficient energy to maintain the speed that the driver requires.
However if the gearing is unusually high then it may not be as efficient as a motor geared for the local line speeds.

You could same about a car, I own a VW Golf that is limited (by VW) to a maximum speed of 155 mph, but returns reasonable fuel consumption at UK legal speeds. If I wanted better economy then a similar car with a smaller / less powerful engine would be a sensible option. FWIW, 0-60 mph can be attained in 5 seconds, 0-100 takes 12 seconds. (Figures from an Autocar road test, not personal experience....)