The Great Western Railway had, since its inception been the loner amongst the rai1ways of this country. Beginning with its adoption of Brunel’s broad gauge in the early nineteenth century, this tradition of individuality was carried on beyond the nationalisation of the railways in 1948 to the introduction on the Western Region ten years later of he first main-line diesel hydraulic locomotives. Ostensibly the idea was to assess the relative merits and demerits of the hydraulic transmission as compared with the electric variety. The diesel types with hydraulic transmission were restricted entirely to the Western Region; perhaps the ghost of Brunel and his advocates had something to do with this! Nevertheless, with the implementation of the National Traction Plan in 1967, the D600 class “Warships” days were numbered. But they deserve their place in the story of diesel traction on Britain’s railways, marking as they do, a milestone in the history of motive power development in this country.
Five locomotives of this type were ordered from the North British Locomotive Company in November 1955, eventually to become Western Region “Warships” numbers D600 to D604. These locomotives were built under the pilot scheme of the British Transport Commission’s Modernisation and Re-equipment programme for the rai1ways. It was proposed under this scheme to introduce specific types of diesel locomotives in four broad power groups, and to subject them to a period of intensive trials in order to evaluate the advantages and disadvantages of each type.
This was, however, not to be, and shortly after the programme was launched a re-appraisal was carried out, following which, bulk orders were placed with contractors, in many cases hardly even before the first of the prototypes were outshopped. Some of these proved their worth, but not until after much re-work of major components, including for the many engines fitted to the Brush-Sulzer Type 4 locomotives was undertaken.
Back to the Pilot Scheme orders, the North British Company delivered the first locomotive of the D600 class in 1958. These “Warship” class locomotives were powered by Anglo-German engines – two N.B.L./M.A.N. L12V 18/21S to be precise – each with a continuous output rating of 1000hp, at an engine speed of 1445 rpm. This placed the design in the category of locomotives with high-speed engines – another area for comparison and trials under the Pilot scheme – with many others sporting medium speed engines.
They were carried in a full width body over two three-axle bogies, and the central axle of each bogie was ‘free, with the engines driving the axles through a Voith/North British L306R hydraulic transmission. This was denoted as the A1A-A1A wheel arrangement, which could to a degree be seen as a disadvantage when it came to getting sufficient power to the wheels to start and haul a train.
When I first penned this article, I wrote:
“Contrary to popular opinion, diesel locomotives are not merely tin boxes on wheels, belching forth voluminous clouds of noxious fumes; these locomotives even had mainframes!”
The mainframe part of that comment was clearly true, but with the benefit of hindsight, the “clouds of noxious fumes” was a bit much. But this was at a time when you could see the pollution of steam trains, but we were yet to become more aware of the hidden dangers of the diesel exhaust.
The underframe was built up from mild steel plate and sections, covered with steel plate forming a continuous floor. The double plate frame bogies were fabricated from 7/16 in. thick plates, with cross-stretchers and headstocks riveted to the side members. Double swing link bolsters provided support for the weight of the whole of the locomotive and its contents. These were in turn fitted with four bearing pads on each bogie, with the final drive gear train, and wheels and axles fitted with “Timken” roller bearing axleboxes with a wheelbase of 15ft equally divided. The driven wheels were 3ft.7ins. in diameter, whilst the centre pair were 3ft. 3 ½ ins.
At least one item that stands out in the list of particulars given is the weight of the locomotive.
At over 117 tons, these were really heavy machines, especially when compared with designs that appeared less than a decade later, and typically delivered around 2800 h p, for less than 100 tons of locomotive. This power-weight challenge faced by the first “Warships” stands out even more when compared with the D800 series of Locomotives, which for the same power weighed a mere 78 tons. Nearly 40 tons less! The D600’ s were certainly very solidly bui1t!
Theory has it (or possibly had it, theories may have changed!) that the less of its own weight a locomotive has to haul, the greater the weight of the train that can be hauled, for the same engine power. With a power/weight ratio of 17.1 hp/ton this certainly compares unfavourably with the D800 series, which for the same power had a power/weight ratio of slightly more than 25.6 hp/ton. A further comparison with the most recent freight locomotives in use on Britain’s rail network – the Class 70 – shows that they have a power to weight ratio of over 29hp/ton.
The pressure charged NBL/MAN 12 cylinder ‘vee’ engines were flexibly mounted on fabricated steel section underframes, which was intended to mitigate stress placed on the engine from shock loading under accelerating and braking conditions. The engine crankcase and cylinder blocks were built up from steel plate, the former incorporating cast steel bulkheads carrying the main bearing housings, the crankshafts being hardened and ground alloy steel forgings.
The hydraulic transmission installed by Voith/NBL included three separate torque converters, each of which was designed to cover three separate speed ranges, with each one arranged to take over at the appropriate road speed automatically. The final drive to the outer axles on each bogie was completed through a pair of Hardy Spicer cardan shafts.
Braking equipment was provided by Westinghouse air brakes for the locomotive, with four brake cylinders (10ins x 8ins) on each bogie operating clasp brakes to each wheel. A separate air brake handle was provided, which operated the locomotive brakes only, whilst a proportional valve ensured that application of the train vacuum brake gave a proportionate application of the locomotive’s air brake.
Also noted in the list of particulars is a water tank having a capacity for 1000 gallons of water. The reason for this was that since the locomotive were introduced at a time when only steam heating of locomotive hauled stock was available, all diesel Locomotives designed under the modernisation plan were provided with steam heating boilers. In this case they were “Spanner” boilers, operating at a pressure of 80lbs/sq.in. This latter item contributed a great deal to early diesel types weight, and occupied a not inconsiderable amount of space.
Another feature that added greatly to the weight, particularly in this case, was the use of heavy steel fabricated construction techniques. The British Transport Commission’s insistence on using thicker plate than necessary was the principal reason for using these techniques, resulting in a sturdy but unnecessarily heavy structure. This was also the first product from the North British Loco. Co. for the home market, other than shunting types previously built. As such, no doubt there was some experimentation in the design of such a totally new locomotive type to the British railway scene.
External design was left to the manufacturer, and as a result the locomotive types produced under the ‘Pilot Scheme’ all differed in appearance, and unlike the range of ‘Standard’ steam locomotives there was no ‘family likeness’. The D600 series ‘Warships’ were perhaps one of the more attractive designs. The stressed skin framework of the bodysides was punctuated with a honeycomb of grilles, covering the various vents and air intake points.
In addition to the doors providing entry to the driving cabs at either end, windowed access doors were provided adjacent to the engine compartments, and sections of the roof were made detachable for installation and removal of equipment. The cabs themselves were provided with two large flat windscreens, each having independently operated wipers.
It should be noted here that the majority of diesel types introduced at that time had three windscreens. In fact, apart from the ‘Deltics’, the twin windscreen arrangement was for a long time restricted entirely to the Western Region’s diesel-hydraulics. Another feature peculiar to the ‘Pilot Scheme’ types, was the provision in each nose end of a flexible bellows connection, for use when through passage was required between locomotives when worked in multiple.
Two fans mounted in the roof were arranged to draw cooling air through the twin bank ‘Serck’ radiators mounted just to the rear of each cab. A third grille, positioned mid-way along the roof, served as an engine room vent. The only other apertures were the exhaust outlets, and the output from the ‘Napier’ pressure charger.
Since the train classification headcode panels were not introduced until I962, these “Warships” were provided with train classification discs, and head/tail lamp brackets, as per the then standard steam traction practice. Twin air-operated warning horns were provided in each nose end. Standard side buffers and screw coupling draw-gear were also fitted at each end. Other nose connections were provided for vacuum brake and steam heating pipes, and jumper sockets for control connections when worked in multiple.
Numbering and livery
This series of locomotives, as already mentioned, was ordered from the North British Locomotive Co. at the time of introduction of the re-equipment programme, on I6th November I955. Delivery was due to take place fifteen months after the order was placed, which should have been completed by late I957. As often happened, delays in delivery caused their introduction to be put back to 1958.
A list of numbers, names and building dates is given below:
Livery styles for British Railways diesel locomotive Livery prior to I956 followed basically that scheme applied to the former LMSR diesel-electric units 10000/10001 – black with aluminium lining and raised numerals. Bogie sideframes and sundry details were also picked out in aluminium. Commensurate perhaps with the new era about to begin, all new diesel locomotives were turned out in the new ‘standard’ green livery. This was applied to the nose, body side panels, and that section of the roof extending over each cab and the entrance doors. The roof was medium grey between cantrails. The bogie and underframe details were black, with buffer stocks and the beam itself in the vicinity of the coupling hook picked out in red. Handrails and the aluminium beadings to the cab windows, windscreens and warning horn mountings were bright polished. Nameplates and the new style B.R. crests were carried on the lower and upper bodysides respectively, and on the same centreline between the engine room access doors on either side. The nameplates themselves were similar to ex GWR locomotive nameplates; cast in brass with raised lettering on a red background.
The scheme of numbering diesel locomotives introduced at this time, including the use of the prefix ‘D’, was developed in order to avoid any confusion which might have arisen using six figure unit numbers. Also it was considered desirable to allocate a block of numbers to individual classes or types, and the problems were thus overcome by use of the ‘D’ prefix. The unit numbers for the D600 series were Gill San transfers applied to the cabsides, under each of the four droplights. Directly under each number, were the North British works plates, and the WR route restriction colour discs, which in this case were single red. They were of course already scrapped when British Rail introduced the TOPS renumbering, which had been first been considered by BR in 1968, following work done in the USA by IBM and the Southern Pacific Railroad. The system was purchased by BR – including the source code – together with an IBM System 360 mainframe computer, and its implementation was supported by Southern Pacific personnel.
The oddest aspect for the North British Warships was perhaps that they were allocated the new classification – Class 41 – but which was never carried.
In later years, ½ and full height yellow warning panels were applied, which did nothing for their appearance, and the same might be said of the ubiquitous ‘Rail Blue’ livery, and the double arrow symbol seen on D600 whilst awaiting the breakers torch at Barry. Headcode boxes had also been fitted in their mid to late years, since in 1960, the train class, route and reporting number were combined into a single four character display. So, the old style discs were dispensed with and all new locos built after that were fitted with a roller-blind display that could display the full reporting number. Of course this meant for some – such as the North British “Warships” a pair of two character boxes were fitted to either side of the loco front.
These locomotives were the first 2000hp main line types to be placed in service on the Western Region, and were intended for express Passenger and other top link duties. A demonstration run on Monday I7th February I958 was made by No.D600, hauling a nine coach train from Paddington to Bristol and back. It is interesting to note, in connection with this run, that in order to demonstrate the locomotive’s ability, on the return journey from Bristol, soon after leaving, one of the engines was shut down, and the remainder of the trip completed on a single engine.
The first regular top link passenger work for the class commenced in June I958, with the ‘Cornish Riviera’ express. Also during this month, a series of comparative tests was made, with the second of the class D60I, and various classes of 4-6-0 steam locomotives. The trials took place between Newton Abbot and Plymouth. It was thought that summer Saturday services in particular would need piloting over this route, and since there would not be enough diesel locomotives available double heading trials were carried out with steam locomotives in order to determine optimum loads and timings over this route. Unfortunately for the North British “Warships”, the D8XX series Swindon “Warships” was appearing in ever increasing numbers.
This fact, coupled with somewhat varied standards of engine performance, notwithstanding a lack of confidence by maintenance staff in their reliability, gradually forced this class out of the principal duties. The overall performance of the first two, D600-1 was rather better than D602-4. This difference has been attributed largely to the fact that the engines for the first two were actually built in Germany, whereas North British made those for D602-4 under licence. No doubt, there is more than an element of truth in that statement, but perhaps it could also explain the reason for the long gap between the delivery of D600/1, and D602-4.
All five were based for the most part, at Plymouth Laira depot, and in their latter years restricted entirely to Cornwall. In 1967 their demise was foreshadowed by the implementation of the National Traction Plan. With this scheme, it was proposed to ‘phase out’ classes of locomotive coming under one of the following three headings:
- Elimination of types that had given trouble
- Those having excessive maintenance cost
- Those classes of low numerical strength
Once again, unfortunately these “Warships” came under all three headings. In 1967 they were transferred to South Wales for a short time, working mineral trains, in place of English Electric type 3’s. This proved to be their final duty, since they were returned to Laira in December 1967 for withdrawal. In July 1968, after being stored for seven months, D600/1 were sold to Woodhams, of Barry and D602-4 to Cashmeres at Newport for scrap.
Sadly, despite its pioneering status, not one of this class of diesel-hydraulic locomotives was rescued for preservation – although the nameplate of D601 “Ark Royal” survives in the NRM at York. But, hydraulic transmission was not a complete failure for BR, since the second “Warship” class locomotives, the Class 42, were very successful, and in turn, they were followed by a final design, the Class 52 “Western” series. But by the time these appeared, the decision to use diesels engines with electric transmission had been made, and these too were to suffer a similar fate to the diesel-hydraulic pioneers.
Useful Links & References
- “Diesel-Hydraulic Locomotives of the Western Region”; Brian Reed, pub; David & Charles 1974; ISBN 0715367692
- “Diesels Western Style”; Keith Montague; Pub; Oxford Pub. Co. 1974; ISBN 0902888390
- “Giants of Steam – Story of the North British Locomotive Co.”; Rodger Bradley; Pub; Oxford Pub. Co., 1995; ISBN; 0860935051
- British Rail Class 41 (Wikipedia)