ETH Fitted Class 31 Performance

[70014IronDuke]

True. The notion that the ETH power was magicked out of fresh air and didn't effect the power available for traction is absolute b****cks. You don't have to be a driver to know that, a basic understanding of physics is all that's required. I used to know several Bath Road drivers and they told me that they would turn the EH off when going up inclines like Filton bank or up out of the tunnel.

Surely this was normal practice even with 47/4s? There was (is?) a button on the the power controller which knocks the ETH out for approx 30 seconds to enable full output from the engine for traction purposes.

There are/were relays in the motor-alternator sets on MK2 air-con vehicles which then delay by a variety of seconds the start up of the system on the carriage in order to avoid a sudden full-load surge on the ETH alternator.

 

[43096]

So what made the Class 31 so utterly awful and why keep building them for over a decade?

They didn't keep building them for over a decade.

 

[70014IronDuke]

.....

As for 31's in passenger service, I did manage to ride one of the Chester to Blackpool rush-hour trains, with 4 non-aircon Mk 2's, topped & tailed 31's, both providing traction. I didn't time the trains but it felt dreadfully slow.....

Imagine how the original class 30's performed on the Gt. Eastern, or the 31's on the G.N. locals out of Kings X..

31s had a poor power/weight ratio even by the standards of first generation diesels, but a 'load' of four Mk2s for two locomotives should have been no problem whatsoever, and most certainly should not have been 'dreadfully slow'. (Well, ok, if you compare to an HST it would be slow, but that's obviously unfair.)

31s when first delivered, and up to about 1963-4 (I'd guess) worked many Class 1 trains on the GE, including the Kings Lynn trains and CAmbridge Buffet Expresses. I'd guess the loads were typically 9 Mk 1s - so around 300 tons trailing load.

When Type 4 power was in short supply, IIRC they were also diagrammed for the Master Cutler into KX in about 1962-63. This was usually a Tinsely D58xx locomotive.

I presume the train could not maintain Cl 47 timings. (This later became a Tinsely Cl 37 turn, and sometimes D0260 Lion or D0280 Falcon) .

 

[Dai Corner]

31s had a poor power/weight ratio even by the standards of first generation diesels, but a 'load' of four Mk2s for two locomotives should have been no problem whatsoever, and most certainly should not have been 'dreadfully slow'. (Well, ok, if you compare to an HST it would be slow, but that's obviously unfair.)

31s when first delivered, and up to about 1963-4 (I'd guess) worked many Class 1 trains on the GE, including the Kings Lynn trains and CAmbridge Buffet Expresses. I'd guess the loads were typically 9 Mk 1s - so around 300 tons trailing load.

When Type 4 power was in short supply, IIRC they were also diagrammed for the Master Cutler into KX in about 1962-63. This was usually a Tinsely D58xx locomotive.

I presume the train could not maintain Cl 47 timings. (This later became a Tinsely Cl 37 turn, and sometimes D0260 Lion or D0280 Falcon) .

How did they compare with the steam locos they replaced?

 

[Ash Bridge]

31s had a poor power/weight ratio even by the standards of first generation diesels, but a 'load' of four Mk2s for two locomotives should have been no problem whatsoever, and most certainly should not have been 'dreadfully slow'. (Well, ok, if you compare to an HST it would be slow, but that's obviously unfair

I have to agree, I think the slowness on the service the OP mentions would have been more down to the nature of the infrastructure rather than the traction, especially on the Mid Cheshire Line section, when I travelled between Stockport and Manchester on the 31 hauled Sheffield services I seem to recall they weren't such slouches, likewise between Preston and Carnforth on the WCML whilst working to Barrow.

 

[ac6000cw]

I used to ride the 31-hauled Birmingham-Norwich trains fairly regularly (as far as Peterborough). They were OK, performance-wise, compared to the Mk1 DMUs they replaced (and the passenger accommodation/ride was a definite improvement).

As far as I remember, the switch to loco-haulage came about because the Easter Region thought the route had growth potential, but needed better equipment (and faster end-to-end journey times, which they got by cutting out some of the intermediate stops). No money for a new generation of DMUs, so they made the best they could out of what was available to them (Type-4 power was too valuable to use on secondary services).

 

[70014IronDuke]

How did they compare with the steam locos they replaced?

I don't "know" - and it would depend on what exactly they replaced - but at a guess, I'd say they would roughly match a B1 in service on a Class 1 passenger train.
I'd guess they would struggle to match a B17 or Britannia on the fastest-timed and heavier (?) Norwich - Liverpool St GE trains, but I think these were mainly taken by the early Class 40s and then 37s as they were delivered.

I'm not sure if the timetables up to 1960 really had any 'crack' timings ("The Fenman" perhaps?). Class 31s also took over scores of secondary services which were not DMU turns. ISTR being hauled by a Cl 31 on some sort of Cambridge - Kings Lynn (or possibly Norwich, I bailed out at Ely) local with about 3 coaches in 1961. This would have been a B1 or possibly B12 turn a year or two earlier, I'd guess.

Maybe a GE historical expert in here will be come along to shed light on this transition and the 'power' of the 31s.

 

[edwin_m]

From Wikipedia...

Class 31 power: 1470bhp
Class 31 weight: 108t to 115t

Class 33 power: 1550hp
Class 33 weight: 74t to 78t

Class 37 power: 1750bhp
Class 37 weight: 102t to 107t

So the Class 31 has less than the power of a much lighter class 33, for the weight of a significantly more powerful class 37. The use of six-wheel bogies (versus four-wheel for the 33) is going to lengthen the bodyshell and make everything generally heavier, but having the middle axle of each bogie unpowered also worsens starting tractive effort. You might then expect it to have a lower axle load which would be useful on lightly built lines - but assuming the weight is evenly distributed the axle loads are very similar for the three classes.

So I do have to wonder why these locos were built in such quantity...

 

[Cowley]

From Wikipedia...

Class 31 power: 1470bhp
Class 31 weight: 108t to 115t

Class 33 power: 1550hp
Class 33 weight: 74t to 78t

Class 37 power: 1750bhp
Class 37 weight: 102t to 107t

So the Class 31 has less than the power of a much lighter class 33, for the weight of a significantly more powerful class 37. The use of six-wheel bogies (versus four-wheel for the 33) is going to lengthen the bodyshell and make everything generally heavier, but having the middle axle of each bogie unpowered also worsens starting tractive effort. You might then expect it to have a lower axle load which would be useful on lightly built lines - but assuming the weight is evenly distributed the axle loads are very similar for the three classes.

So I do have to wonder why these locos were built in such quantity...

Also bearing in mind that when built they only had a 1250/1365 Mirrlees engine fitted.

 

[ac6000cw]

I'd guess they would struggle to match a B17 or Britannia on the fastest-timed and heavier (?) Norwich - Liverpool St GE trains, but I think these were mainly taken by the early Class 40s and then 37s as they were delivered.

From what I've read, a class 40 was about equivalent to a Britannia in real-world performance.

I think the early dieselisation wasn't about improving performance as such, it was more about cleaning up the railway's image (at a time of clean-air acts and rising private car sales) and getting rid of the dirty steam servicing jobs that increasingly people didn't want to do at the sort of wages the railway could afford. I think it took the arrival of the Deltics, Westerns and 47's for dieselisation to really start having an impact on journey times.

 

[randyrippley]

So I do have to wonder why these locos were built in such quantity...

I think that's simple: Brush had a dedicated diesel assembly shed, and a type 2 design, and capacity, so they got the orders. At that stage the BR workshops hadn't transitioned to diesel building, EE had their hands full assembling class 20 and class 40, and no-one took North British seriously: they had a bad product and small capacity (and were trying to build diesels using steam techniques).
Brush got the order by default

And don't forget they initially had plans to uprate the class 30s - three (?) ran successfully for some years as type 3, one as type 4, which makes me think the claim that the traction gear couldn't handle the full power of the transplanted EE diesels is wrong

 

[ac6000cw]

From Wikipedia...

Class 31 power: 1470bhp
Class 31 weight: 108t to 115t

Class 33 power: 1550hp
Class 33 weight: 74t to 78t

Class 37 power: 1750bhp
Class 37 weight: 102t to 107t

So the Class 31 has less than the power of a much lighter class 33, for the weight of a significantly more powerful class 37. The use of six-wheel bogies (versus four-wheel for the 33) is going to lengthen the bodyshell and make everything generally heavier, but having the middle axle of each bogie unpowered also worsens starting tractive effort. You might then expect it to have a lower axle load which would be useful on lightly built lines - but assuming the weight is evenly distributed the axle loads are very similar for the three classes.

So I do have to wonder why these locos were built in such quantity...

Keep in mind that the 30/31 was quite an early design (first one delivered in 1957, about the same time as the first class 20). Maybe the Mirlees engine was cheaper (but longer) than the equivalent Sulzer, and they needed the extra length to accommodate the steam heating boiler. 6 traction motors also cost more than 4, and the non-motored axles have lower unsprung mass.

I agree that the class 33 was a better overall design, but it was ETH only (which probably helped make possible the fitting of the longer 8-cylinder engine in a loco the same length as the 6-cylinder class 26/27).

(Re. A1A-A1A versus Bo-Bo or Co-Co - in the 1950s EMD produced freight locos as single-engined Bo-Bo 'F-units' and passenger locos as more powerful, heavier, twin-engined A1A-A1A 'E-units' - those didn't need the extra low-speed tractive effort of 6 powered axles, so they saved the cost of two motors).

 

[The Lad]

At full ETH output about 350hp is going to that so what is left over is about class 24 power, about 900hp at the rail to shift it's own 3 coaches worth of weight before putting the train on.

 

[randyrippley]

from wikipedia:

The Class 31/4s, numbered from 31400 to 31469, were conversions of 31/1s to which ETH was fitted. They had an ETH index of 66, equivalent to 330 kW, which was sufficient to power trains of up to eleven Mk 3 carriages, in order to allow them to power long trains, whose service run would be worked by a larger locomotive, between depot and terminus, although in actual passenger service loads rarely exceeded four or five carriages. 330 kW accounted for about a third of the total electrical power output. The early conversions tapped off the main generator such that none of the ETH power was available for traction even if the ETH was not being used. The traction power output of some of the 31/4 subclass was therefore limited to a maximum of two-thirds of that of the non-ETH variants, this did not help the performance of an already somewhat underpowered locomotive, and late running of these 31/4-hauled services sometimes happened. Later conversions allowed unused ETH power to be used for traction

https://en.wikipedia.org/wiki/British_Rail_Class_31#Class_31.2F4

I've no idea how true that is

 

[KevinTurvey]

I've just dug out an old 1987 timetable (table 97) The Liverpool - Sheffield trains on this route were all 31/4s and Liverpool Lime St - Manchester Piccadilly was timetabled for 51 minutes and 49 minutes for the other way.
By contrast, today's 158 / 185's are timetabled for between 47 and 54 minutes (typically) although many do have an extra two stops now.

 

[RichmondCommu]

I've just dug out an old 1987 timetable (table 97) The Liverpool - Sheffield trains on this route were all 31/4s and Liverpool Lime St - Manchester Piccadilly was timetabled for 51 minutes and 49 minutes for the other way.
By contrast, today's 158 / 185's are timetabled for between 47 and 54 minutes (typically) although many do have an extra two stops now.

Interesting stuff. Do you having the timings for Sheffield to Manchester?

 

[1179_Clee2]

I had a single 31/4 on 12 MK 1 coaches in the late 1980's.
Inter City Charter unit ran steam specials from Crewe to Holyhead but used the coaching stock to form incoming workings from other area's.
Train started at Harrogate 1st 47/8 expired at Leeds 2nd 47/8 had dragging vacuum brakes on the train and was replaced at Stalybridge. Single 31/4 took the train via Stockport to Crewe, but don't think it was using ETH.
11 TSO's and 1 BSK all blue and grey Mk 1's.

 

[randyrippley]

Re. A1A-A1A versus Bo-Bo or Co-Co - in the 1950s EMD produced freight locos as single-engined Bo-Bo 'F-units' and passenger locos as more powerful, heavier, twin-engined A1A-A1A 'E-units' - those didn't need the extra low-speed tractive effort of 6 powered axles, so they saved the cost of two motors.

And it probably no coincidence that the class 30/31 bogie is an adapted USA design - its a Commonwealth Steel Co design

 

[D5645]

I don't "know" - and it would depend on what exactly they replaced - but at a guess, I'd say they would roughly match a B1 in service on a Class 1 passenger train.

The Brush 2's were ordered by British Railways Eastern Region to replace their fleet of B1 steam loco's.

263 diesels to replace 410 steam loco's.

It's worth remembering that the bulk of the fleet were delivered as 1365hp machines which was considered sufficient for the medium mixed traffic role at the time. For heavier duties it was always intended to use a pair of Brush 2's, hence the provision of connecting doors in the cabs.

 

[D5645]

Interesting stuff. Do you having the timings for Sheffield to Manchester?

Lots of timing information from the 1984-1988 period of class 31 operation here :-

www.table29.co.uk

A great website created by a well known 31 follower.

 

[Clarence Yard]

The Brush 2's were ordered by British Railways Eastern Region to replace their fleet of B1 steam loco's. 263 diesels to replace 410 steam loco's.

Not quite. Only the ER B1 got replaced by Brush 2's - not all 409 (the unfortunate 61057 having perished in 1950) of the ScR, NER and ER fleets. A variety of ER classes met their end because of the advent of the Brush 2.

In the KX division the Brush 2 could be found on a variety of work. Suburban work with either 2 quad arts or 6 "blockenders", lifting heavy ECS out of the cross, semi fast P'boro "Parly" trains (8 mk1), trip freights, moving heavy engineering trains on their own, as well as subbing for Brush 4's on such workings as the Cleethorpes.

Once going they could move mountains but stopping them with a heavy load could get interesting. One interesting thing about them is that, after gaining their EE engines, they hated being worked hard on a hot day with No 1 end leading. At FP we had several mod'ed in the 1970's with high speed rad fans to combat this and they were the ones that we tried to use on the class 1 substitution work.

They are not as quick off the mark as a Sulzer 2. When we ran out of locos in 1979 for several weeks we borrowed, when we could, a cl.25 to do a Parly working. The cl.25 got winded when they had to sustain speed with 8 mk 1 coaches, despite their better acceleration. The Brush 2 had the better slogging ability. But neither a Brush or Sulzer could match the acceleration of a Baby Deltic. I look forward to getting re-acquainted with that in future years!

When I moved to the WR in the late 1980's they didn't have too many good words to say about the class, dating back to the days when they tried to replace the Hymeks with them. No speed, no guts, was the common cry.

But when we at KX had to resort to using the early /4 locos on ETH turns to the likes of Cleethorpes they managed o.k. Not spectacular at keeping to time but they coped with the load and the punters got heat and light. No doubt the power draw from the ETH wasn't always at a constant high so power for decent traction was still there.

 

[D6975]

And don't forget they initially had plans to uprate the class 30s - three (?) ran successfully for some years as type 3, one as type 4, which makes me think the claim that the traction gear couldn't handle the full power of the transplanted EE diesels is wrong

No the claim is absolutely correct. The experimental uprated ones had rewound traction motors to deal with the extra power.

 

[The Crab]

In the mid 80s I frequently used trains from the South Coast which reversed at Brum to get me back to Sheffield. Although these usually produced a 45 or 47 it was not unusual to get a 31. I think the load was 6 and a 31 would time the train to Chesterfield but they always lost time on the 1 in 100 climb to Bradway tunnel 7 so were always a couple of minutes down at Sheffield. I never saw a 31 on a southbound equivalent.

 

[ac6000cw]

And it probably no coincidence that the class 30/31 bogie is an adapted USA design - its a Commonwealth Steel Co design

I'd never thought about that before, but yes, it definitely has the look of a typical American 'drop equalizer' bogie, as used most US diesel loco builders at some point (except EMD who normally used their own designs - the E-units used a three axle version of the classic 'Blomberg' swing-hanger design).

 

[36270k]

The class 31 bogie does resemble the bogie on the Alco PA
They may have been designed by the same group ( General Steel Castings )

 

[ac6000cw]

The class 31 bogie does resemble the bogie on the Alco PA
They may have been designed by the same group ( General Steel Castings )

According to this page, the PA bogies ('trucks' in US parlance) were GSC products - http://www.contrib.andrew.cmu.edu/~shadow/prr-diesels/sideframes/a1a.html

 

[Cowley]

A quick question for anyone who knows these things.
When the 31s were re-engined with the English Electric power units would Brush have had a choice in the matter or was it a case of them having to do what they were told by a very unhappy BR?
It's always struck me as surprising that they used over two hundred power units from one of their main competitors when they'd used Sulzer for the class 47 (albeit with problems).

I wondered if there was ever a thought of fitting the 8 cylinder Sulzer unit as fitted to the class 33 instead, which has always seemed like a good reliable engine with a similar power rating?

I'm not thinking about when the 30s/31s were built as maybe the 8 cylinder Sulzer wasn't available by then, more about when they had to replace the Mirrlees units a few years later.

 

[Clarence Yard]

It was a BR decision to re-engine with the EE power unit and the conversion work was done at Doncaster.

 

[edwin_m]

A quick question for anyone who knows these things.
When the 31s were re-engined with the English Electric power units would Brush have had a choice in the matter or was it a case of them having to do what they were told by a very unhappy BR?
It's always struck me as surprising that they used over two hundred power units from one of their main competitors when they'd used Sulzer for the class 47 (albeit with problems).

I wondered if there was ever a thought of fitting the 8 cylinder Sulzer unit as fitted to the class 33 instead, which has always seemed like a good reliable engine with a similar power rating?

I'm not thinking about when the 30s/31s were built as maybe the 8 cylinder Sulzer wasn't available by then, more about when they had to replace the Mirrlees units a few years later.

I got the impression the 31s were pretty reliable (after re-engineing) but I may be wrong. Of the EE products the 20s, 37s and 40s were solid and reliable, if underpowered and over-weight in the case of the 40, and although the 50 was less so that is alleged to be down to BR messing with the specification. I exclude the Deltic as something of a one-off with a totally different engine, subject to special attention and never intended to have a long life.

 

[Cowley]

It was a BR decision to re-engine with the EE power unit and the conversion work was done at Doncaster.

Thanks Clarance Yard. I assume Brush had to pay for the new engines? If so that must have been a big hit for the company.