The mighty Class 74 (some questions!)

[Harlequinuk]

Greetings all!

I have a soft spot for the Class 74, im sure the reaction will be one of wide eye astonishment, but i do like the `Big Ed`. But some questions if i may!

What happened to the bogies/ traction motors/ generators etc once scrapped? Also the engines? 10 Paxman Ventura , would they be cut up as well or moved on to something else?

and ofc, a request for any photos or even video of them running would be very much appreciated.

 

[Big Jumby 74]

Can post a couple of photos, but they are of very poor quality. The locos were on their last legs when I was a junior in the industry, and were renown for their failings more than anything else.

 

[bishdunster]

They certaintly werent that reliable on the 13.30 Poole to Clapham vans in the 1970s, often being unable to make it up Parkstone bank (before the juice reached that far) , oddly enough the 73s were far better

 

[mike57]

May be an obvious question, and I never expereinced them 'live' but the Class 74 diesel engine is rated at 650hp, the Class 73 at 600hp, so what was the point...

I realise the 74 had more power on third rail, but the 73 was already successful, if they had been able to squeeze in something that would have given 1000hp+ on diesel then it would have been an improvement, but otherwise they just seem like a 'dead end' in terms of development.

 

[Harpo]

the Class 74 diesel engine is rated at 650hp, the Class 73 at 600hp, so what was the point...

My meagre understanding of EDs is that the diesel capability wasn’t about planned main line running but more about the last few hundred yards of operation into unelectrified yards and sidings.

 

[ac6000cw]

May be an obvious question, and I never expereinced them 'live' but the Class 74 diesel engine is rated at 650hp, the Class 73 at 600hp, so what was the point...

I realise the 74 had more power on third rail, but the 73 was already successful, if they had been able to squeeze in something that would have given 1000hp+ on diesel then it would have been an improvement, but otherwise they just seem like a 'dead end' in terms of development.

They were a 'dead end' in terms of development, being intended primarily for hauling Southampton boat trains which needed 'last mile' diesel capability to get inside and around the port. For that use, 650hp was enough. The 73's weren't powerful enough on 3rd-rail (and probably too useful elsewhere), and the 71's could be spared.

AFAIK the rolling stock program to go with the mid-1960s Southampton/Bournemouth electrification project was based around rebuilding/re-engineering/adapting existing stock where possible with minimal new-build, hence the cl. 71 rebuilds into 74s, the cl. 33 push-pull conversions, creating 4TC units (and 4REP trailer cars) out of existing Mk1 hauled stock etc. BR didn't have the money to do much else, and the class 33s and 71s weren't that old in the mid-60's, neither was the hauled stock - and of course to some extent the Southern Region inherited the Southern Railway philosophy of recycling old into new.

IIRC, the cl. 71s had a flywheel-based temporary energy storage system to get them over 3rd-rail gaps (like the earlier experimental CCx SR electric locos). For the cl. 74 conversions, that was removed and a diesel engine, generator/alternator, cooling system, fuel tank and extra electrical/electronics kit was squeezed into the space instead. Based on comments I've read over the years, it wasn't an easy thing to do and that contributed to their reliability problems. I particularly remember reading a comment from a senior BR engineer involved in the cl. 74 project, along the lines of 'never again' as far as doing that sort of major conversion.

Shades of the 769s conversions, really.

 

[Haywain]

May be an obvious question, and I never expereinced them 'live' but the Class 74 diesel engine is rated at 650hp, the Class 73 at 600hp, so what was the point...

I realise the 74 had more power on third rail, but the 73 was already successful, if they had been able to squeeze in something that would have given 1000hp+ on diesel then it would have been an improvement, but otherwise they just seem like a 'dead end' in terms of development.

They were a conversion from class 71s, and intended for Southampton and Weymouth boat trains. So the diesel capability was for the last stretches off the main line..

 

[D6130]

By strange coincidence, I was looking through one of my old notebooks yesterday from my time working on the Southern in the mid-'70s and this note caught my eye:

Friday 19/12/1975: 74 006 damaged by fire and explosion at Worting Junction.

The big 'JBs' (Southern Region classification....the 71s were 'JAs') also worked some early morning newspaper/passenger trains from Waterloo....a particular favourite of mine being the 03 40 (Sundays only) to Petersfield which - with only one coach and three vans after Guildford - resulted in some spectacularly fast climbs of Haslemere bank. After running round at Petersfield (there were two crossovers in those days) the train returned empty to Guildford at 06 00, formed the 07 00 Guildford to Woking passenger service and then ran empty to Clapham Yard.

In July 1977 I travelled on the Southern Region-organised "Anniversaries Railtour"....commemorating the fortieth anniversary of the Portsmouth Direct electrification and the tenth anniversary of the Bournemouth electrification. Formed of a 12 car all first class consist of Southampton boat train FOs and FKs - plus a BCK for the guard - we travelled from Waterloo to Bournemouth non-stop via Havant and Netley behind a pair of 33s. After a couple of hours 'refreshment' stop in Bournemouth we were treated to a blistering non-stop run back to Waterloo behind 74 007 taking an hour and twenty minutes.

Later that year the 74s were withdrawn after only ten years' service and 007 was one of those broken-up by Pounds shipbreakers of Tipner, Portsmouth, after a brief period in store at Fratton Yard.

 

[ac6000cw]

They were a conversion from class 71s, and intended for Southampton and Weymouth boat trains. So the diesel capability was for the last stretches off the main line..

...although they couldn't realistically haul the Weymouth boat trains beyond Bournemouth/Branksome (as Branksome - Weymouth wasn't electrified until 1988, and all the 74s had been withdrawn by then).

 

[30907]

...although they couldn't realistically haul the Weymouth boat trains beyond Bournemouth/Branksome (as Branksome - Weymouth wasn't electrified until 1988, and all the 74s had been withdrawn by then).

No, but they were rostered as far as Bournemouth where time was allowed for the loco changes.
Did they also turn up on ordinary Bournemouth workings (with or without the 3TC sets)?

 

[contrex]

I particularly remember reading a comment from a senior BR engineer involved in the cl. 74 project, along the lines of 'never again' as far as doing that sort of major conversion.

I seem to remember reading that a contributing factor in the lack of reliability was the electronic systems, in particular the lack of robustness of the printed circuit boards, the way they were mounted, and the connections thereto. I gather that the rail environment is particularly hard on electronics. On a side note, don't the Class 91s suffer from shortages of 1980s components, e.g. 8080 processors?

 

[ac6000cw]

I seem to remember reading that a contributing factor in the lack of reliability was the electronic systems, in particular the lack of robustness of the printed circuit boards, the way they were mounted, and the connections thereto.

Yes, I remember those sort of comments too.

As someone who's been designing electronics since the 1970s to the present day (from hobbyist to professional), yes, in the early/mid 1960s I think the rail industry was still working out how to keep electronics reliable on moving vehicles. The shock forces and vibration can cause e.g. cracking of solder joints and cracking where wires enter the body of a component (in those days most electronic components mounted on printed circuit boards had wires which were soldered into the board). Also temperature cycling causes expansion and contraction of the PCBs and the components, plus low temperatures can cause water condensation problems.

 

[Haywain]

On a side note, don't the Class 91s suffer from shortages of 1980s components,

Well, 1980s technology is inevitably going to be more difficult to obtain now than it was it the time that is was state of the art. I would imagine that applies equally now to much of the technology of the 2000s.

 

[ac6000cw]

On a side note, don't the Class 91s suffer from shortages of 1980s components, e.g. 8080 processors?

Given when it was designed, I would have expected it to be using something more modern than the Intel 8080 (dating from 1976), even if it was only the slightly later, but faster and simpler to use, 8085. But more modern and powerful MPUs were around by the early 1980s, like the 16/32-bit Motorola 68000 (the first MPU I ever designed into anything, in the mid 80s, running at the heady heights (!) of 4MHz clock rate and whose architecture I still have a soft-spot for - it was very easy to program in assembly language).

 

[mike57]

Well, 1980s technology is inevitably going to be more difficult to obtain now than it was it the time that is was state of the art. I would imagine that applies equally now to much of the technology of the 2000s.

An interesting side effect of the march of technology:

A 100 year steam locomotive can be kept running,and new parts fabricated locally should they be needed as long as you have access to a skilled machinist and the right tools

A 50 yo engine which is incorpoating 1st gen integrated circuits, CPUs etc is going to be far more of a challenge,because local manufacture on a one off basis is not a viable option. So looking ahead one could visualise a situation where fully functional units from this time period could become much rarer than older steam powered and early diesel stuff

 

[43096]

The big 'JBs' (Southern Region classification....the 71s were 'JAs')

That’s not correct.
Class 71 were HA
Class 74 were HB
Class 73/0 were JA
Class 73/1 were JB

 

[contrex]

Given when it was designed, I would have expected it to be using something more modern than the Intel 8080 (dating from 1976), even if it was only the slightly later, but faster and simpler to use, 8085. But more modern and powerful MPUs were around by the early 1980s, like the 16/32-bit Motorola 68000 (the first MPU I ever designed into anything, in the mid 80s, running at the heady heights (!) of 4MHz clock rate and whose architecture I still have a soft-spot for - it was very easy to program in assembly language).

You are quite right. I ought to have checked... from a leaflet titled "GEC Transportation Projects Class 91 25kV BoBo locomotives for British Rail"...

The Class 91 locomotive and the Class 90 locomotives (also being equipped by GEC) have similar microprocessor control modules with obvious advantages for spares and test equipment.

The armature and field converters are under the direct digital control of a microprocessor based control system using a single Intel 8086 16 bit micro-processor. The programme itself is stored in EPROM (erasable programmable read only memory), and the data in RAM (random access memory). This provides flexible and adaptable control (being software based) whilst using standardised hardware and software. The package provides high accuracy with minimum drift and high immunity to interference. The self diagnostic (ie fault logging) facility will be particularly helpful in maintenance.

It also says 'The locomotives and their equipments have been designed for a 35 year life when averaging some 420,000 km each year.' I presume this is from 1988.

GEC Class 91 Locomotives

== Doublepost prevention - post automatically merged: Thursday at 15:59 ==

Well, 1980s technology is inevitably going to be more difficult to obtain now than it was it the time that is was state of the art. I would imagine that applies equally now to much of the technology of the 2000s.

The 8086 cpu (as I now know) used in the microprocessor control systems of the Class 91 was not exactly 'state of the art' in 1988, having been released 10 years before. So coming up to its 50th birthday.

 

[Julia]

An interesting side effect of the march of technology:

A 100 year steam locomotive can be kept running,and new parts fabricated locally should they be needed as long as you have access to a skilled machinist and the right tools

A 50 yo engine which is incorpoating 1st gen integrated circuits, CPUs etc is going to be far more of a challenge,because local manufacture on a one off basis is not a viable option. So looking ahead one could visualise a situation where fully functional units from this time period could become much rarer than older steam powered and early diesel stuff

Not just rail having this problem: https://www.theguardian.com/media/2011/oct/09/bbc-radio4-long-wave-goodbye

"BBC Radio 4 long wave, which transmits on the 198 kilohertz frequency, relies on ageing transmitter equipment that uses a pair of ... valves – no longer manufactured – to function. The valves, at Droitwich in Worcestershire, are so rare that engineers say there are fewer than 10 in the world, and the BBC has been forced to buy up the entire global supply. Each lasts anywhere between one and 10 years, and when one of the last two blows the service will go quiet"

 

[norbitonflyer]

May be an obvious question, and I never expereinced them 'live' but the Class 74 diesel engine is rated at 650hp, the Class 73 at 600hp, so what was the point...

Ther point was that the 73s had proved very useful, so making a few more electro-diesels was a good idea. And there wasn't enough work for the 71s, so that looked like a cheap and cheerful way of doing it.

Unfortunately they didn't use EE 4SRKT engines in the conversions, although the Paxman engine was not an entirely off the wall choice, they were already being used in the Class 14s (another white elephant class for BR, but there was nothing wrong with their engines, and many class 14s saw long service in induistrial use)

 

[Harpo]

A 100 year steam locomotive can be kept running,and new parts fabricated locally should they be needed as long as you have access to a skilled machinist and the right tools

Off topic, but it’s a major difference between steam preservation’s ability to build everything it needs, versus diesel preservation only existing by burning its way through a diminishing stockpile of consumables.

 

[norbitonflyer]

IIRC, the cl. 71s had a flywheel-based temporary energy storage system to get them over 3rd-rail gaps (like the earlier experimental CCx SR electric locos). For the cl. 74 conversions, that was removed and a diesel engine, generator/alternator, cooling system, fuel tank and extra electrical/electronics kit was squeezed into the space instead.

I thought I'd read that the bodies were lengthened to fit it all in - some changes were needed anyway to remove the pantograph and its well. However, i can't find a figure for the length of a 71 (Wikipedia gives a 74 as 50ft 5.5in)
I'm not sure from these pictures, but I think the spacing between the middle two axles is shorter in the 71 than in the 74

 

[ac6000cw]

I thought I'd read that the bodies were lengthened to fit it all in - some changes were needed anyway to remove the pantograph and its well. However, i can't find a figure for the length of a 71 (Wikipedia gives a 74 as 50ft 5.5in)
I'm not sure from these pictures, but I think the spacing between the middle two axles is shorter in the 71 than in the 74

This website - http://www.clag.org.uk/wheelbase.html - lists the same wheelbase for both classes (copied below). I suspect lengthening them would likely have been too costly to contemplate (especially if they were monocoque construction). Also after trying to do a a decent estimation from the photos, I think the distance between the inner ends of the bogies is the same (within estimation errors!)

 

[D6130]

That’s not correct.
Class 71 were HA
Class 74 were HB
Class 73/0 were JA
Class 73/1 were JB

Yes, sorry.... you're quite correct. The class letters were, of course, allocated in order of construction - apart from the 74s (HB) which were a modification of the 71s (HA). Senior brain fog!

 

[contrex]

I thought I'd read that the bodies were lengthened to fit it all in

Strengthened, certainly. Wikipedia describes the bodywork mods...

The bodies of Class 71 locomotives were not designed to be structural components capable of carrying any weight, following the principle of earlier designs in that the underframe was the main structural member of the locomotive while the body served primarily as weatherproofing. In August 1966, after initial strip-down and examination of E5016, engineers were forced to re-assess the build when it became apparent that the planned equipment changes could not be accommodated. Although at one point it was mooted that the body would have to be divided and lengthened, the problem was eventually resolved by rebuilding the bodies with a Warren truss framework and outriggers to support the curved body skin. Translucent roof panels were fitted to increase daytime illumination in the engine room. Modifications were also made to the locations of the cooler groups, water tanks, and exhaust silencer.

 

[eldomtom2]

An interesting side effect of the march of technology:

A 100 year steam locomotive can be kept running,and new parts fabricated locally should they be needed as long as you have access to a skilled machinist and the right tools

A 50 yo engine which is incorpoating 1st gen integrated circuits, CPUs etc is going to be far more of a challenge,because local manufacture on a one off basis is not a viable option. So looking ahead one could visualise a situation where fully functional units from this time period could become much rarer than older steam powered and early diesel stuff

I suppose the big question is to what extent you could replace them with something more modern. The Intel 8086 mentioned as used in the Class 91 is a well-documented and easily emulated chip.

 

[norbitonflyer]

Strengthened, certainly. Wikipedia describes the bodywork mods...

Ah - I was probably misremembering that lengthening had been proposed at one stage.

 

[Harlequinuk]

As i understood, there was a potential plan for retro fitting Class 86 electronics to make the 74`s more reliable? And what happened to the engines / bogies/ traction motors?

 

[Cowley]

Ah - I was probably misremembering that lengthening had been proposed at one stage.

Yes, definitely strengthened if not lengthened. Quite a lot of body mods (grilles etc) though, and I think some fairly major modifications to the bogies as well.

 

[jonty14]

May be an obvious question, and I never expereinced them 'live' but the Class 74 diesel engine is rated at 650hp, the Class 73 at 600hp, so what was the point... I realise the 74 had more power on third rail, but the 73 was already successful, if they had been able to squeeze in something that would have given 1000hp+ on diesel then it would have been an improvement, but otherwise they just seem like a 'dead end' in terms of development.

 

[Haywain]

May be an obvious question, and I never expereinced them 'live' but the Class 74 diesel engine is rated at 650hp, the Class 73 at 600hp, so what was the point... I realise the 74 had more power on third rail, but the 73 was already successful, if they had been able to squeeze in something that would have given 1000hp+ on diesel then it would have been an improvement, but otherwise they just seem like a 'dead end' in terms of development.

It wasn't intended to go anywhere in terms of development. It was a cheap way of building additional ED locomotives using surplus class 71s.