The handsome ‘Hymeks’
They were arguably the most successful diesel-hydraulic on BR’s books, but the useful ‘Hymeks’ were withdrawn after just 14 years in service through no fault of their own. Now, 60 years after their introduction, Rail Express looks back at this handsome Type 3.
HISTORY, on the face of it, appears a little unkind to the ‘Hymeks’. They were not the longest serving diesel-hydraulic used by British Rail, nor were they as high profile as their larger ‘Warship’ and ‘Western’ cousins, and their main diesel-electric rival is still in service today, more than 45 years after the last ‘Hymek’ was withdrawn.
But these simple statements paint an inaccurate picture. The ‘Hymeks’ were handsome, versatile locomotives, well liked by crews and – despite being in service for just 14 years – were arguably BR’s most successful dieselhydraulic. In fact, 60 years on from their introduction, their legacy could have been so much better had a series of ‘what-ifs’ gone their way.
BR’s Western Region is well documented for its almost maverick
‘go it alone’ policy, which in the modernisation era saw it opt for dieselhydraulic technology rather than the diesel-electrics locos chosen by the other regions.
By the end of the 1950s, the WR was already using diesel-hydraulics in the Type 2 (1,001-1,400hp) and Type 4 (2,000-2,999hp) power ranges, and there was a growing need for a mixed traffic machine in the intermediate
THE AIM
Type 3 (1,500-1,999hp) range.
So it was that in 1959, the British Transport Commission (BTC) authorised £3.6 million for a fleet of 45 Type 3 diesel-hydraulic locomotives, and the order was won in June that year by Beyer Peacock (Hymek) Ltd of Gorton, east Manchester. It is interesting to note that each loco cost £80,000 – equivalent to about £1.4 million today, or just slightly less than the cost of a new Class 66.
The plan was to replace more than 300 Class 5 ‘Hall’ and ‘Grange’ steam locos, which led to the idea that a similar sized fleet of ‘Hymeks’ might be built.
As it turned out, only 101 were ever ordered. The BTC increased its initial order by 50 in June 1960, with a final six ordered in December 1961. They were to be numbered D7000-D7100.
Beyer Peacock (Hymek) was a joint venture put together to bid for a slice of BR’s modern traction needs. Beyer Peacock had a long tradition of building steam locomotives, but had no real experience of diesel engines or transmissions. So it teamed up with Bristol Siddeley (based in Ansty, near Coventry), which had a licence to build German Maybach engines, and
J. Stone (of Deptford), which could supply Maybach Mekydro hydraulic transmissions – and together they came up with the ‘Hymek’ design.
The loco was built around a Maybach MD870, a four-stroke, V-form, 16 cylinder engine – essentially an expanded version of that used in pairs in the larger Type 4 ‘Warship’ and ‘Western’ locos. The MD870 was capable of delivering 1,920hp but was de-rated to 1,740hp at 1,500rpm to improve reliability. It gave the locos a 100mph capability, although this was actually restricted to 90mph in service.
The engine was coupled to a Mekydro K184U hydraulic transmission, which, in turn, powered two Commonwealth-type bogies of two axles, hence a B-B wheel arrangement.
There were four gear stages set to change under full power at 26, 42.5 and 70 mph, and the transmission efficiency was claimed to be 80% over the full power range. The locos were fitted for multiple working but only with other members of the class, and this was denoted by a yellow triangle.
TECHNICAL DETAILS
One big advantage of diesel-hydraulic transmission, and so one reason why it was adopted by BR’s Western Region, is that it resulted in a much lighter locomotive than an equivalent dieselelectric with its heavy generator.
When fully laden with 900 gallons of fuel and 800 gallons of water, a ‘Hymek’ weighed in at 75.5 tons, some 30 tonnes lighter than English Electric’s Type 3 (Class 37). This gave the ‘Hymeks’ a much higher powerto-weight ratio than EE’s machine, which worked in its favour for hauling passenger trains but tended to work against it on certain key freight duties.
There were few technical differences between the different batches, the main two being the steam heat boilers and loco air brakes. The first batch of Nos. D7000-7044 were fitted with Stone-Vapor boilers for train heating and Knorr loco air brakes, while the rest had Spanner Mark IIIa boilers and Westinghouse loco air brakes. All were fitted with Northey exhausters for train vacuum brakes.
The external styling was done by Ted Wilkes, of design consultants Wilkes & Ashmore. Wilkes worked on several BR designs, not least the prototype Falcon and the later Brush Type 4 (Class 47), which both share a family likeness with the ‘Hymeks’.
The result was one of the most handsome locos ever built for BR,
especially in their early livery of two-tone green with white window surrounds.
A finishing touch was the use of cast aluminium numbers underneath the cab windows. These were fixed to the loco and probably contributed to the fact that no ‘Hymek’ ever carried a TOPS number. In fact, the most that ever happened was the ‘D’ being painted out at the end of steam in 1968. As if to underline their Western Region heritage, some locos even carried GWR-style ‘red spot’ route availability markings – something more usually associated with steam rather than diesel locos.
INTRODUCTION TO SERVICE
The first loco to be delivered was class doyen No. D7000, which was exhibited at London Marylebone on May 10-14, 1961, as part of The Institution of Locomotive Engineers’ golden jubilee celebrations. This was some eight weeks earlier than planned, although the final loco No. D7100 would be handed over behind schedule in early 1964 – albeit due to various design modifications demanded by the BTC as a result of early teething troubles.
No. D7000 was then officially handed over to BR in a ceremony at Paddington on May 16, after which it was sent to Swindon for further tests and trials, and finally accepted into stock on May 31, 1961.
As the locos came off the production line at Gorton, they were given a shakedown test run over the demanding Midland route through the Peak District from Manchester to Derby. With a rake of up to 10 coaches in tow, this would test the locos over their entire power range and so highlight any manufacturing defects that might be present.
They would then be sent to Swindon for further tests before acceptance into traffic. These would often involve a run over the twisting Golden Valley line to Gloucester, which on the way back included a stiff climb to Sapperton Tunnel, north of Kemble.
The fleet entered service in BR Brunswick green with a lighter green stripe at solebar level and white window surrounds, while No. D7020 onwards had a small yellow warning panel. ‘Hymeks’ only ever carried two basic liveries – BR green and later BR blue, with the main variations being either half or full yellow ends, and white or yellow window surrounds.
Some members of the class never received blue livery, going to the scrapyard still in green, while a small number were painted in the chromatic blue variation.
However, no ‘Hymek’ ever carried a TOPS number under BR’s 1973 renumbering scheme, in which they became Class 35s, and none were ever named.
MIXED TRAFFIC
Bristol Bath Road was the first to receive an allocation, followed by Cardiff Canton. These two and Old Oak Common in London were to be the main three depots throughout their BR life, but Plymouth Laira, Newton Abbot and Swansea Landore would also have a few at times. Later there was a small allocation at Worcester for banking duties up the Lickey incline (see box). Major repair work was usually undertaken at Swindon Works.
It is interesting to note that in the early 1960s, most dedicated diesel depots were still being built and so the locos had to be serviced in the less than ideal conditions of old steam sheds. Cardiff Canton, for example, received its first allocation of ‘Hymeks’ in March 1962, but was only opened for refuelling from October 1963 and not fully opened until the following year.
In common with BR’s other Type 3 locos, the ‘Hymeks’ proved to be a real all-rounder. They were used on a mixture of passenger, freight and parcels duties all over the WR, and also parts of the Southern Region too.
Crew training began in the summer of 1961 on the Bristol to Portsmouth route as far as Salisbury. By November that year, Cardiff crews were being trained up on runs between there and Bristol. In early 1962, the locos were beginning to spread their wings, appearing on turns to Shrewsbury via Hereford – and even as far as Leicester Central on York-bound inter-regional trains.
Nos. D7008 and D7009 arrived in London for crew training in February 1962, soon after which the type took over some London to South
Wales express passenger turns. The ‘Hymeks’ were originally intended as a replacement for Class 5 steam locos, but were in fact able to match schedules designed for Class 7 ‘Castle’ or even Class 8 ‘King’ steam locos.
For example, ‘Hymeks’ could singlehandedly keep time hauling up to 13 coaches and 450 tons through the Severn Tunnel on prestigious workings from Paddington, such as ‘The Red Dragon’ to Cardiff and ‘The Pembroke Coast Express’ to Swansea.
By June 1962, there were enough locos at Cardiff to cover all Class 1 services to London. And, although they were theoretically limited to a top speed of 90mph, some have been timed at up to 100mph.
SECONDARY LINE USE
Where they did perhaps fall down was in handling heavy unfitted freight trains, which were better suited to heavier locos that had more axles for braking. This was the case with coal trains in South Wales, and so it was that in 1963 a number of EE’s heavier, Co-Co Type 3s were allocated to Cardiff Canton.
This freed up ‘Hymeks’ to be cascaded to Paddington to Worcester/ Hereford services, a route they would be regular performers on right to the end. Other regular passenger duties were on the Cardiff and Bristol to Portsmouth Harbour and Weymouth routes, plus through trains from Paddington to Minehead.
A further cascade occurred in 1964 when ‘Westerns’ took over the South Wales expresses. This released more ‘Hymeks’ for use on secondary routes, such as Reading to Redhill, as well as inter-regional trains south of Oxford to Bournemouth. On rare occasions, they would also substitute for ‘Warships’ on the Exeter-Waterloo route.
By the end of the 1960s, ‘Hymeks’ were increasingly found on freight and parcels duties all over the
Western region.
Although the locos settled down to be reliable and versatile, they were not without teething problems. At the end of 1961, with just a few in traffic, they were found to have been designed with insufficient engine cooling that led to overheating. Then in 1963, a problem was highlighted with transmission failures that needed frequent gearbox replacement.
A trial was devised to find the cause of the problem, with oddnumbered locos up to D7075 being derated to 1,350hp and even-numbered locos up to D7078 having their first gear locked out. The eventual cause was tracked down to the transmission control equipment, which was failing to change gears at the correct engine speeds, resulting in overspeeding, high stress and excessive heat.
Modifications saw the fleet back to full strength by the end of 1963, after which they gave relatively reliable service comparable with other loco types. They averaged around 60,000 miles per year, lower than the 65,000 clocked up by a ‘Western’ or the 95,000 by a ‘Warship’, but a figure that reflects the mixed traffic nature of their work.
RUNDOWN BEGINS
The beginning of the end came as early as 1967, when BR was faced with a surplus of locomotives following a decline in traffic caused by road competition, as well as the much reduced post-Beeching network.
The BR board decided to withdraw all locos that were deemed nonstandard or expensive to maintain.
Unfortunately the definition of ‘non-standard’ did not just mean a small fleet size, but included all dieselhydraulic types too, as the board had decided to concentrate on dieselelectrics. Moreover, in 1969, BR found it was more expensive to maintain diesel-hydraulic types at the same level of availability as diesel-electrics, and so the writing was now well and truly on the wall.
The first ‘Hymeks’ to be withdrawn were Nos. 7006 and 7081 in September 1971, just over 10 years since No. D7000 had been introduced, and the entire fleet was planned for withdrawal by the end of 1973. To mark this event, BR ran the ‘Hymek Swansong’ railtour on September 22, 1973, which took blue-liveried Nos. 7001 and 7028 on a circular tour from Paddington to Hereford, out via Severn Tunnel Junction and back via Worcester and Oxford.
This farewell, however, proved to be some 18 months premature. A shortage of motive power – ironically caused by problems with the diesel-electric Brush Type 2s (Class 31s) replacing the ‘Hymeks’ – allowed a small number of Class 35s to soldier on.
Between September 1971 and the end of 1972, 80 members of the class were withdrawn, leaving 21 in service at the start of 1973. Remarkably, 10 of those made it into 1974, no doubt helped by the vast number of spares available from the other 91 withdrawn locos. Only Nos. 7001, 7016, 7026 and 7093 were withdrawn that year, leaving Nos. 7011, 7017, 7018, 7022, 7028 and 7029 to carry on into 1975.
The latter two were withdrawn in January and the remaining four in March. Note that nearly all of the final 10 were older examples from the first batch ordered.
THE LEGACY
Most ‘Hymeks’, 86 in all, were scrapped at Swindon Works. But 11 others ended their days at scrapyards round the country – most notably No. 7089 (see Departmental box) that was scrapped at TJ Thomson in Stockton. Thankfully, the remaining four made it safely into preservation (see box).
Despite their relatively short working life, things could have been so different for the ‘Hymeks’ if it were not for circumstances outside of their control. If more freight wagons had been fitted with train brakes, for example, then Class 37s might not have been drafted in to work South Wales coal trains and the ‘Hymek’ fleet could have been much larger as a result. If the Beeching cuts had not led to a surplus of locomotives, there would have been no need for a blanket cull of certain types. And if the BR board had not decided to standardise on diesel-electric technology without exception, then the versatile and reliable ‘Hymek’ might have lasted as long as the diesel-electric Class 37.