British Rail Class 52

Historical context

When switching to diesel traction as part of the Modernisation Plan of the 1950s, BR designed, and commissioned designs for, a large number of locomotive types. At this time (and arguably right up until Sectorisation in 1982), BR's regions had a high degree of autonomy, which extended as far as classes of locomotives ordered and even the design criteria for those locomotives. Whilst almost all other diesel locomotives were diesel-electric, the Western Region employed a policy of using diesel-hydraulic traction, originally commissioning three classes of main line locomotives: a type 2 and two type 4s (later designations class 22, class 41 and class 42). With pressure to increase the speed of the transition from steam to diesel, volume orders for the class 22 and class 42 (along with a similar design class 43) followed in 1957, a mere two years after the original orders and well before any idea of performance or reliability could be gained. At the same time it was realised that all the existing orders (diesel-electric and diesel-hydraulic) were for types 1, 2 and 4; thus orders were placed for 101 Type 3 diesel-hydraulics (later Class 35). However the increasing demands for more powerful locomotives prompted a further order, in 1961, for 74 diesel-hydraulics of 2,700 hp (2,000 kW); so when the first locomotive was outshopped from Swindon Works in December 1961, less than a year after the order was placed, the Westerns were born.

The theoretical advantage of diesel-hydraulic was simple: it resulted in a lighter locomotive than equivalent diesel-electric transmission. This provided better power/weight ratio and decreased track wear. Unfortunately, it had two key disadvantages:

Experience showed that the Bristol-Siddeley-Maybach engines were superior to those made by NBL-MAN and although the use of twin engines in the same locomotive was new, the process did not produce any insurmountable problems. In the end the diesel-hydraulic experiment foundered on low fleet numbers, poor maintenance conditions and design issues; not on its German heritage or development of a novel configuration. BR's Swindon Works maintained all the diesel hydraulic locomotives and their early demise resulted in a much reduced workload and hastened its eventual closure in 1986.

The Western

With the Hymeks and Warships already in service but proving underpowered for top-link services, BR Western Region needed a high-powered locomotive for these trains – the Western therefore needed two diesel engines to achieve the required power output. In keeping with their policy, a new locomotive with a hydraulic transmission was envisaged. Experience had shown that the Maybach engines in the Hymeks were superior to the earlier Maybach and MAN engines used in the Warships, particularly in power output. Also Maybach were able to offer their 12 MD engines rated at 1,350 bhp (1,010 kW) allied to a Voith transmission; a Mekydro transmission designed to handle such power could not be fitted into the British loading gauge.

Prototypes sited the engines behind the driving cabs but drivers found this too noisy; moving the engines centrally meant making the locomotive heavier, removing some of the design's advantage. In production use, the dual-engine arrangement turned out to have some advantages: in particular, the Westerns were able to continue operating with a single engine running in situations where more conventional single-engine designs would require rescue by another locomotive. This valuable property was intentionally duplicated in the later High Speed Trains and was one reason for them having two power cars.

The most serious continual problem with the class was the design fault mismatch between the Maybach MD655 engines and the Voith L630rV three speed hydraulic transmissions. The top gear ratio in the transmission was too high for the torque characteristics of the engine: the result was that a single locomotive could struggle to reach its claimed 90 mph (140 km/h) top speed in the absence of down grades, more so when work-weary and due for overhaul. These factors, combined with the 'Devon banks' (a major part of their running grounds) deleterious effect on tired engines, all conspired against the Westerns continuing in top-line service. With fifty Class 50 locomotives becoming available, following completion of the West Coast Main Line electrification, and new High Speed Trains, the speed and comfort increases the Western Region sought could be achieved and the Westerns dispensed with. Towards the end of their careers the Westerns were all allocated to Laira (Plymouth).

Competition and comfort

Whilst the design was largely successful the working life of the class was relatively short. It was a non-standard design adding greatly to its maintenance costs while the national British Rail policy was also moving away from diesel-hydraulics. When the Westerns were introduced in 1962 the Western Region had 226 diesel-hydraulics and 10 diesel-electrics (excluding shunters); by 1966 the numbers were 345 and 269 respectively. As a result, the early 1970s saw the decision taken to retire all the diesel-hydraulic types. Class 46 and Class 47 took over passenger and heavy freight while Class 25 covered the lighter duties. Following completion of the electrification of the West Coast Mainline throughout from London to Glasgow, the Class 50s were allocated to the Western Region, the introduction of High Speed Trains 3 years later was the final nail in the coffin for the Class 52 Westerns.

In 1968–69 the Westerns received train air brake equipment in addition to their vacuum exhausters, thus significantly extending their working lives, unlike the similar but lower-powered, Warship class, although four of the class (D1017-D1020) did not receive dual brakes with these locomotives being among the first withdrawals. The vacuum brake equipment was retained and to fit the additional equipment, it was necessary to remove one of the fuel tanks. However, as with the Warships, it proved impossible to equip them with electric train heating (ETH, or head-end power in US terminology). The Western Region faced particularly stiff competition for its prime inter-city services in the mid to late 1970s from the M4 motorway and it was generally felt within BR that a significant speed and comfort increase on the prime Paddington-Bristol route were necessary. The lack of ETH meant the Westerns could not power the newly introduced air-conditioned BR Mark 2d/e/f coaches – a shortcoming that classes 47 and 50, equipped with ETH (the latter from new), did not share.

Performance

The highest recorded speed with a Western that O. S. Nock was aware of was 102 mph when D1068 hauled 9 coaches (305 tons gross) down 1 in 1320 (i.e. virtually level) at Southall. The train averaged exactly 100 mph for 12.8 miles between Slough and Ealing whilst hauling a service from Reading to Paddington. An unverified eyewitness account by a BR secondman (Drivers assistant) stated that 110 mph had been achieved when his driver drove a Western between Reading and Westbury. He experienced the loco shaking from side to side as 110 mph was indicated on the speedometer.

However, when it came to drawbar horsepower the Westerns in some respects were less capable than the equivalent diesel electric locos. Nock states "whilst the Westerns took their rightful place as fast and powerful locomotives it became evident that they were showing the same deficiency in actual power put forth at the drawbar as the [diesel hydraulic] Warships had done. The highest output that came to my notice was a sustained 85 mph hauling 560 tons descending 1 in 1320, which equates to 1500 edhp (equivalent drawbar horsepower)". This is 56% of power at the flywheel, whereas for a diesel electric one would normally expect a figure of 75 to 80%. A similar result was obtained when Clough & Beckett compared the performance of type 4 diesel locomotives (Classes 45/46/47/50/52) hauling trains up the ascent to Whiteball summit. They deliberately chose data to show each class in their best light and included a Western run which produced 1775 edhp but they still concluded that "without doubt the Westerns get the wooden spoon certainly not what one would expect from units of 2700 bhp". The best performer was the Class 50, a 2700 hp diesel electric locomotive, on one run this achieved 2115 edhp.

Despite this apparent limitation, the BR Western Region load-limit book gave the same 550ton loading figure for both the Class 52 and Class 47 diesels over the South Devon banks between Newton Abbot and Plymouth. The reason for this is that, while the diesel-electric classes could produce high maximum tractive effort for limited periods, diesel hydraulics could produce significantly higher continuous tractive effort.

Names and numbers

The Class 52s were never renumbered into their TOPS number series (52 xxx) and they became the last class of locomotives on BR not to carry a TOPS number. This is primarily due to them being adorned with Great Western style cast number plates, as opposed to the adhesive number transfers used on most other types. While the first Western was under construction, proposals for livery and names were prepared by the BR design panel. The D1000 series locomotives were to be named after famous West of England place names; the illustration from the portfolio shows D1000 bearing the name Cheddar Gorge. This trend was not followed in production, however and the Westerns were named with general heraldic and regimental terms prefixed with the word "Western" as per the following table:

Of the 74 locos built only 7 have survived to preservation.

D1029 was originally named Western Legionaire [sic], but renamed Western Legionnaire in 1969, the nameplate being cut to allow the additional letter to be inserted.

Although designated Class 52 under the TOPS scheme, no Western ever carried its "52 0xx" TOPS number. As withdrawal was already planned when the TOPS numbering scheme was introduced and because of the cast number plates, it was not considered cost effective to renumber the locomotives. Some class members did run with the "D" of their number painted over – TOPS classification removed the need for locomotives to indicate their energy type in the running number (D = Diesel, E = Electric), rather grouping locomotives into relevant class number ranges based on power output and energy type combined (this convention has become somewhat blurred in recent years), 01 to 69 being diesel, 70 to 97 electric, and 98 all steam types.

When the display of destination headcodes/reporting numbers on the front of trains was dropped in 1976, the instruction was given for them all to be set to "0000". On many Westerns, the headcode was set to display the loco's number in contravention of this directive and most surviving members of the class ran like this until they were scrapped. If used for routeing, such reporting numbers would be interpreted as a passenger express terminating on the Southern Region.

Early liveries

When the initial batch of Westerns was being built in 1961-2, British Rail was considering a new unified corporate colour scheme but had not yet made a final decision on what it would be. As a result, some of the early locomotives were painted in experimental liveries: D1000 was rolled out of Swindon Works in November 1961 painted in Desert Sand. Initially the numbers, borne on the left hand cab when viewed from the side, were painted in white but soon individual numbers and letters, looking like they were cast but apparently made of wood, were fitted. This was in turn replaced by the final design of cast nameplate and numberplate; metal with a black background. This livery was later altered by the addition of a small yellow warning panel and black roof. After this, D1001 was delivered in all over maroon livery with yellow buffer beams and D1002-D1004 in all over green and small yellow warning panel. The remaining deliveries were all in maroon, with small yellow warning panels after D1010 and D1043 of the Crewe built locomotives. Exceptions to this were the initial Crewe-built batch D1035-D1038 which were in green with red backgrounds to the nameplates and D1015, outshopped in the experimental "golden ochre" livery with small yellow warning panels. On one end of D1015, the yellow panel was embellished by the addition of a yellow band which extended sideways from each of the top corners and round and onto the cabside for a short distance, resembling a T shape.

Corporate scheme

After the adoption of Rail Blue with full yellow ends in 1966 (D1048 was the first of the class painted in this livery in 1966), for some unexplained reason a small batch of locos (D1017, D1030, D1036, D1037, D1043, D1047 and D1057) received this variant married to small yellow warning panels, D1030 even carried red buffer beams for a short while. All other repaints were with full yellow ends which extended from the body line above the buffer beam up to the base of the window frames, along the sill of the cab-side windows onto the vertical end reveal. The valance above the cab windows on the front was also painted yellow, leaving the window frames in their base aluminium. The drive to repaint the locomotives in Rail Blue was outstripped by the safety directive dictating full yellow ends for all powered vehicles and some locomotives ran for a time with their original maroon bodies and full yellow ends.

The last loco to be repainted into Rail Blue was D1046, outshopped from Swindon in May 1971. Some early photographs of the blue livery give it a more metallic shade which is even more evident on the locos with small yellow panels. This however is possibly a photographic anomaly with colour film or due to printing techniques.

It is commonly accepted amongst Western enthusiasts in recent years that none of the class or any other British Rail locomotive of the period were ever painted with a metallic paint. However, several publications refer to initial painting in blue as being "chromatic blue" and published images do show a metallic sheen and lighter shade of blue than the standard Rail Blue.

Incidents

Preservation

Seven locomotives have survived into preservation at heritage railways around the UK and one engine D1015 presently operates on the mainline.