The Class 50 Refurbishment Story

JPEGJuice | Wednesday, 8 May 2019 |

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The archetypal look of the Class 50, post refurbishment. 50040 Leviathan heads for the South West, at Wychbold, in June 1982.

Believe it or not, it’s now a whacking 40 years since the hushed and experimental beginnings of the Class 50 refurbishment programme. For fans of the type, the scheme’s raft of modifications brought a buzz of excitement, with a new sound, a new look, and a drastic reduction in Class 47 stand-ins on ‘Hoover’ diagrams.

Indeed, it's fair to assume that the greater proportion of today's extant Fifties owe their very survival, in part, to BREL Doncaster’s four-year run of mega-overhauls which gutted and rebuilt every last member of the class. But for British Rail, the programme was part of a much wider quest to stem the rapidly diminishing reliability of the diesel fleet…

The way the ‘Hoovers’ were turned out of works before the refurbishment programme began. Standard Rail blue with domino dot marker light panels. An attractive look, which most established enthusiasts would initially prefer to the forthcoming spectacle of large logo.


On 1st October 1979, BR’s Chief Mechanical & Electrical Engineer, Ken Taylor, outlined key future development plans for railway engineering. Of some concern was a period between 1983 and 1993, during which the remaining first generation diesels, built between 1958 and 1968, would hit their designated maximum lifespan of 25 years.

Progressive replacement of those diesels would involve the expected shift towards multiple unit operation in the passenger sector, and the launch of a “next generation” of freight motive power, beginning with the Class 58. Consideration was also given to extending the lifespan of some existing loco types, although at that point there was not much optimism re the amount of extra life that could be gained.

Additionally, the first generation diesels with significant lifespans remaining, would need to achieve better standards of reliability than their 1979 norms. So, separately, there was a programme which did not seek to extend the life of existing locomotives, but purely to improve their reliability in keeping with future expectations. This programme was already in full motion with the Class 47s, and there was similar work “scheduled”, it was revealed, for Classes 33, 45/1 and 50. At the start of October, the term used to describe this work was “heavy general overhaul”. The process would replace the regular general overhaul, and its scope would extend into the territory of renewal and revision rather than just maintenance.

It's true that the Fifties' reliability and availability had reached a particularly embarrassing low by the late 1970s, which BR very closely monitored and sought to meet with a solution. But the class was not uniquely selected for 'super-overhaul'. It was a much bigger programme than that.

Unrefurbished Class 50s as they were in their final throes. These shots were taken during 1981, when the programme was in full swing, and around a third of the class had already been modified. 50029 and 50021 (top) have the domino style headcode markers, whereas 50044 and 50027 have two variants of plated headcode panel.

In response to a question by Modern Railways a few weeks later, BREL Managing Director Ian Gardiner argued that the 'super-overhaul' process could essentially be described as remanufacture…

"If [by remanufacturing] you mean the work done by General Motors and other American companies to renew/update diesel locomotives then I must point out that this is virtually what we are doing to Class 47s as they come into Crewe for heavy general repairs. Likewise Doncaster is refurbishing the Class 50s and Derby the 45s."

So when, exactly, did the Class 50 refurbishment programme start in earnest?


The condition in which 50006 Neptune was returned to traffic after refurbishment in mid November 1979. The external appearance was barely any different from that of the standard unrefurbished example of the time. The loco was notably headlight-ready rather than headlight-fitted – a small disc-shaped plate covered the mount on the cab front.

50006 – the first of the class released to traffic in refurbished condition – was a guinea pig. By summer 1979, 50006 had been lounging around at Doncaster works for nearly two years, and minus an engine for a notably long period. Railway enthusiasts at the time attributed the engineless status to the lack of a usable engine to go into the loco. It was the summer after the Winter of Discontent – a chaotic period of strikes and industrial action, which had caused havoc with maintenance supplies and spares. In the absence of any other info, it was easy to attribute the absence of an engine to that.

But the truth was that 50006 had been serving as a testbed for various modifications, which would culminate in “refurbishment”. And in fact, even before Ken Taylor’s address of 1st October, the modification process on Number Six was very well advanced. Although the loco did not return to traffic until mid November ’79, by the start of October it could essentially be considered a refurbished Fifty. However, no other specific Class 50 at Doncaster Works had yet been identified as a second candidate.

In process – Class 50s with headlight holes newly cut in their cab fronts were a sight familiar to Doncaster Works visitors during the 1979-1983 period.

In a works ‘gen report’ dated 3rd August 1979, the Class 50s at Doncaster were attributed the following statuses…

50003: Collision damage. Major repairs required.
50006: Still minus engine.
50007: Complete and returning to traffic. [Loco powered 1V93 the following day].
50017: Stripped for a general overhaul.
50019: Just arrived [late July]. Awaiting general overhaul.
50024: Complete.
50027: General overhaul in progress.
50049: Overhaul in progress.
50050: General overhaul in progress.

So 50017 and 50019, which would respectively become the second and third ‘Hoovers’ to be refurbished, were, in August ’79, still scheduled to receive general overhauls. The work was reclassified as “refurbishment” in October, after Ken Taylor’s address, and at a point when the guinea pig – 50006 – could be deemed an actual template, rather than just an experiment.

In summary then, the Class 50 refurbishment programme started in earnest in October 1979, but work on the guinea pig – the testbed loco – began long before that.

Given that refurbishment typically took a good few months per loco in the thick of the programme, Neptune’s mid November release would take the start of the process back to at least early summer ’79. However, since there was no template for the modification process, the likelihood is that things would have moved more slowly, and the guinea pig would have taken considerably longer. I’d guess (especially based on seeing the loco at Doncaster in June ’79) that the work began at least as early as the spring, and the planning may have gone back as far as 1978.

50033 (nearest) and 50041 undergoing refurbishment at Doncaster Works. Note that 50033’s sandbox recesses (lower bodyside) are already filled – before the headcode panel has been plated. With the guinea pig, filling of the sandbox points was not done until later in the process, and 50006’s recesses were filled separately – not all in one go. There was a definite sense of experimentation with 50006.

It should be noted that even after the release of 50006, unrefurbished ‘Hoovers’ continued to emerge from The Plant. 50027 and 50050 both received regular general overhauls as originally planned, and subsequently followed Neptune out of the works.

And initially, Class 50s going to Doncaster for intermediate overhauls were still returned to traffic ex-works, but in unrefurbished condition. There was, then, a period during which the 1V93 Edinburgh – Plymouth service, famously used for returning ex-works ‘Hoovers’ from Yorkshire down to their own region, was seeing alternate appearances of both refurbished and unrefurbished Class 50s.

Interestingly, there was no ‘hybrid’ status in between unrefurbished and refurbished. The loco was either fully refurbished by The Plant, or left bog standard. For example, when 50014 Warspite left Doncaster ex-works but unrefurbished in April 1980, it was not even fitted with headlights or headlight mounts, although headlights were by that time a definite future safety requirement, and refurbs 50019 and 50001 had just been fitted with headlights by the same works.

On the left, 50047 models the classic Rail blue with headlight look. The cab-front headlight was an at-a-glance means of identifying a refurbished 50 before the large logo repaints began. 50030, on the right, is unrefurbished. Apart from the headlight on 50047 – lacking from 50030, also notice the sandbox access points along 50030’s lower bodyside – absent from 50047. Both locos have the standardised headcode box plate and marker lights, which I’ll discuss in due course. 50030’s roof recess is on the other side of the loco.


The broad goal of refurbishment was to heavily simplify what had come to be seen as an unnecessarily complicated locomotive and make it easier to maintain, whilst updating to contemporary spec, and addressing common causes of failure.

This famously involved the removal of superfluous capabilities such as slow speed management and rheostatic braking, and simplification of the electrics. The air filtration system had increasingly found itself at the root of failures (not to mention unhygienic and unsightly bodyside oil-spewings), so it was completely re-imagined. You can see in the picture above, how an unrefurbished 50044 has spewed oil from the air-management grille. Very common on unrefurbished ‘Hoovers’. After the simplification and ‘cures’, modern spec requirements were met with updates such as the powerbeam headlight.

The ‘Doncaster Dart’ (Plymouth – Doncaster) railtour of July 1981 was booked for a single Class 50, with the unrefurbished 50025 selected as train engine. However, large logo 50040, just returned to the WR after refurbishment, had failed its post-BREL inspection, and was thus sent back to Doncaster for correction via the tour, providing a cool double-header for passengers. Both locos were working (although in tandem, not multiple), and upon reaching Doncaster, 50040 ignominiously sidled off back into The Plant under its own power. 50025 hauled the return leg on its own, as originally booked. Incidentally, 50040 was on the front out of Plymouth, but since the train went via Toton it required a run-round at Sheffield, so 50025 was leading by the time of the photo stop at Mexborough.


50013 Agincourt was the last of the six Fifties returned to traffic post-refurb in standard Rail blue livery. Unlike the first two released from The Plant, it was returned with high power headlights already fitted.

When 50006 first returned to traffic, the visual differences between it, and its unrefurbished sisters, were subtle. Although the plating over of headcode boxes is often associated with refurbishment, that update had been applied to unrefurbished 50s starting as early as 1976, and continued to be applied to unrefurbished 50s during the programme. So the headcode plating is best considered a separate update, which was incorporated into the refurb process if not already added. For reference, there were multiple styles of plated headcode box before refurbishment, with different types of marker lights, and different plate designs. This was subsequently standardised to just one design. If the loco had already received a non-standard version of the headcode box mod, Doncaster Works would revise it to standardised form during refurbishment.

Early refurbished 50s were delivered in standard Rail blue, and the obvious visual identifiers were as follows…

  • A small, disc-shaped plate added centrally on each cab front as a cover for the headlight mount. This appeared only on 50006 and 50017 – the first two refurbs – and the discs were in both cases subsequently exchanged for the actual headlights at Laira.
  • Replacement of one bodyside window (on each side of the loco) with an open grille, as part of the new air-filtration system.
  • Sealing off of the deep roof recess which had formerly been part of the old air-filtration system.
  • Disappearance of the small sandbox access recesses in the lower bodyside.

50019, 50001, 50047 and 50013 were also delivered in standard Rail blue, but were headlight-fitted from the start.

The next example to be refurbished was 50023, which was complete and ready for running tests in the first third of August 1980. It was repainted prior to ECML testing, but it wore a hybrid livery of standard Rail blue, with wrap-around yellow cabsides, as illustrated above left. Before its return to regular traffic, however, 50023 was taken back into the works for a livery update, gaining the classic large logo appearance, as illustrated above right. This delayed the loco’s back-to-traffic date until early September. It worked the 1V93 in large logo livery on the third of the month.


So what was going on with that hybrid livery? What even was it? Rail blue with yellow wrapped round the cabsides? Or large logo without the light grey roof, black window frames and supersized stick-ons?

One clue lies in the fact that 50023 was not only the first Class 50 to be authorised for a large logo repaint, but also the first loco on British Rail to be outshopped in large logo as part of standard livery practice. Previous large logo repaints had been one-offs, but 50023 brought in a new era of selected classes wearing large logo as a default. The 50s were the first standard large logo class, followed about a month later by the 56s.

So this was not a planned special or a bit of unofficial “artistic licence”. It was a BR policy change.

Detective-minded enthusiasts would surely conclude, on this basis, that Howe’s first repaint was already in progress when the instruction came through for large logo livery on Class 50s. BREL had begun painting 50023 in standard Rail blue, and with the blue sections complete, were suddenly advised that subsequent Class 50s should be returned in large logo livery. So why not just revise the livery there and then?

Well, another clue is that the numbers applied on the ‘hybrid’ livery were of standard size. BREL knew when adding the numbers that the loco was going to be finished in large logo, so for economy’s sake, why not apply the large numbers straight away? The likely answer is that they didn’t have the large transfers to apply at that point. Thus, let’s hypothesise, they decided to send the loco out for tests in standard Rail blue while they were waiting for the transfers. It was nothing new for Fifties coming off overhaul at Doncaster to work their ECML tests before any repainting took place, so “test then repaint” would have been a highly predictable decision in the event of any “cosmetics delay”.

But if the yellow ends were still to be painted at that point, the diesel would not have been sent out half painted, and it would also not have made sense to paint the yellow ends in the old style and then extend them later. Again, for the sake of economy, the yellow sections should be completed in one go. Hence, standard blue, but with wrap-around yellow cabs, and an intention to update to full large logo after testing, when the numbers and logos were available to apply.

That’s my theory and I’m sticking to it.

After all that excitement, 50003 and 50004 were outshopped in the same version of large logo as the updated look on 50023. These first three large logo ‘Hoovers’ differed from the next batch of repaints in that the black of their window frames extended right up to the grey roof at the centre of the cab front. You can see the original incarnation above on 50004.

Subsequent repaints, beginning with 50038, had a clear yellow band between the black and the grey roof beneath the headcode panel, like 50020, above. The earlier version of large logo with no yellow band did, however, re-emerge in September 1981, and through the remaining course of the programme there was no settled choice between the two variants.

Since no Class 50 was ever painted in large logo livery before refurbishment, the livery could be considered part of the refurbishment programme – even though the first six (okay, arguably seven) examples initially wore standard Rail blue.


The glaring change to the Class 50s’ sound at the point of refurbishment, was the absence of the highly distinctive drone which had been a product of the original air-circulation system. Prior to refurb, the drone kicked in a few seconds after power-up from dead, quickly rising to pitch and then remaining static at that pitch whilst the loco idled. The pitch rose and the drone got louder when the ETH was turned on. During a particularly rousing station departure you could hear the drone “pushing” alongside the pounding engine.

Refurbished Class 50s in their early to mid 1980s heyday. Clockwise, 50047, 50021, 50044 and 50022.

The drone was a sound you absolutely couldn’t fail to notice. Strong, ever-present, and slightly discordant. Two contributory notes, six semitones apart. The “Satanic interval”, as it’s sometimes described in music. That was your archetypal unrefurbished Class 50 drone. It was likened to the sound of an old vacuum cleaner, hence the ‘Hoover’ nickame.

Refurbishment dispensed with the equipment which had produced that sound, so technically, refurbished 50s were not ‘Hoovers’. The nickname, however, persisted regardless. Without the drone, idling was quiet. So quiet, in fact, that you could hear the faint whilstling of the idling engine, which the drone had always drowned out before.

Once every example was modified, never again could you stand under the canopy at Paddington and hear the almighty racket of the drone reverberating around the structure as a ‘Hoover’ arrived from the West. Neither could you walk up to the frontage of St Davids and know there was a 50 in the station just from the unmistakable roar of its air system. It was definitely something you missed.

Some enthusiasts believed the Fifties’ thump became more focused after refurbishment – although that may just have been a perception in the absence of the drone. To me, they certainly sounded better ‘tuned’ straight out of works. But for a proper A/B test I’d have needed to hear an unrefurbished 50 in action without the drone, and that never happened.


Refurbishment unquestionably improved the Class 50s’ availability in the early 1980s. Even without official statistics, an enthusiast could see the improvement reflected in the number of booked diagrams working to schedule.

In the spring of ’79, when availability had been truly woeful, many scheduled Class 50 turns so commonly produced 47s that you wondered if the booked traction had been changed. On some services, over 5 weekdays, it was not at all uncommon to see 3 Class 47s and just 2 Class 50s. Maybe even 4:1. But by the close of 1983, with every 50 refurbished, the picture was very different. The risk of a 50 being replaced by alternative power was very noticeably lower.


50001 Dreadnought was one of the early batch of refurbs outshopped in Rail blue during 1980. So whilst this may look like the loco as newly refurbished, it's actually a 1984 shot, taken after 50001's next general overhaul, when it finally debuted in large logo livery. All of the Fifties originally refurbished in Rail blue had the large logo livery update during their next general overhaul at Doncaster. Every class member wore large logo livery, but due to the repainting of 50007 in GWR green during February 1984 (before all of the standard blue refurbs had received their livery updates), there was never a time when all fifty Fifties were concurrently sporting this iconic look.

The large logo livery was, initially at least, actually disliked by a number of the established ‘Hoover’ devotees. In 1980 it was considered by some a ‘novelty look’ – not befitting of a serious enthusiast’s locomotive. And some fans of other traction types seized upon the ‘jokey’, oversized nature of large logo to belittle the 50s and their fanbase. That made established Fifty fans even less keen on large logo.

‘Hooverism’ was something that had begun long before large logo. Some understandably disgruntled fans of the 'Westerns' had in part blamed the 'Hoovers' (which directly replaced the 'Westerns' on many services) for the loss of their favourite loco type. Some appeared to regard any applause for the Class 50s as deliberate disrespect and antagonism. A lot of ‘Peak’ fans didn’t much like 50s either – especially on the WR. And even among Class 37 and 40 fans there was sometimes a notion that the 50 was the choice of the “ned”. Large logo definitely exacerbated that perception for a while.

Ironically, though, refurbishment had brought the 50 closer to the sonic ballpark of those older EE designs. And with the 40s on their way out, it seemed logical for 'Whistler' fans to start supporting the old 1Co-Co1’s closest relative. Indeed, early standard blue Class 50 refurbs did gain some popularity with Class 40 fans I knew personally. To some of us, the ‘Hoover’ drone had been a positive feature, but others evidently disliked it, and much preferred the locos without it.

But where the large logo 50s really scored points was with newcomers to the scene. Especially nice and clean, with the whitish-grey roof, large logo livery really caught the eye. In 1981, only the 50s and 56s had been cleared for large logo application as standard. That look gave the 50s a special presence on the passenger network. Made them stand out to new trainspotters. The livery became part of the fleet’s identity, and it celebritised the class to a new generation of enthusiasts. Overall, refurbishment increased the appeal and fanbase of the 'Hoovers'. No question.

Especially given that they finished meaningful service in the early 1990s - long before loco 'recycling' began, an extraordinary number of the Fifties have survived. At Kidderminster in 2002, preserved duo 50049 and 50035 show off both of the classic aesthetics for refurbished examples as returned to traffic. Large logo 50035 is historically accurate, but 50049 was never blue-with-a-headlight in service - it was refurbished straight into large logo.


As a final reference, here’s the order of refurbishment for the Class 50s…


50006 (11/79), 50017 (2/80), 50019 (4/80), 50001 (4/80), 50047 (5/80), 50013 (5/80).


50023 (8/80) – tests only. Returned to regular traffic in large logo.


50023 (9/80), 50003 (9/80), 50004 (10/80), 50038 (11/80), 50032 (11/80), 50022 (12/80), 50015 (2/81), 50020 (3/81), 50035 (3/81), 50012 (5/81), 50010 (5/81), 50036 (6/81), 50040 (7/81), 50045 (8/81), 50039 (9/81).


50033 (9/81) – tests only. Returned to regular traffic in large logo.


50033 (10/81), 50041 (10/81), 50031 (11/81), 50008 (12/81), 50016 (1/82), 50009 (2/82), 50021 (4/82), 50037 (4/82), 50044 (4/82), 50029 (6/82), 50042 (5/82), 50025 (8/82), 50005 (8/82), 50048 (9/82), 50028 (10/82), 50034 (10/82), 50024 (11/82), 50026 (12/82), 50018 (12/82), 50007* (2/83), 50046 (3/83), 50011 (4/83), 50043 (5/83), 50049 (5/83), 50050 (7/83), 50027 (7/83), 50030 (9/83), 50002 (10/83), 50014 (12/83).

* 50007 only wore large logo for a year, before receiving a GWR green repaint.