British Rail Class 55
The British Rail Class 55, also known as a Deltic, or English Electric Type 5, is a class of diesel locomotive built in 1961 and 1962 by English Electric for British Railways. Twenty-two locomotives were built, designed for the high-speed express passenger services on the East Coast Main Line between Edinburgh and. They gained the name "Deltic" from the prototype locomotive, DP1 Deltic, which in turn was named after its Napier Deltic power units.
At the time of their introduction into service in 1961, the Class 55s were the most powerful single-unit diesel locomotives in the world, with a power output of. They had an official service speed of, and introduced the first regular 100 mph diesel passenger service to Britain. They were capable of higher speeds than this, and often exceeded their official maximum in service, especially in their later years, with speeds of up to, being recorded on level gradients, and up to whilst descending Stoke Bank.
Despite their successes, the Deltics had a relatively short commercial service life of 20 years. From 1978, they were displaced by the next generation of high speed diesels, the "InterCity 125" High Speed Trains. Deltics were subsequently relegated mostly to secondary services on the Kings Cross to York, Edinburgh and Hull routes, although they continued to operate some top-link trains, such as the Hull Executive, until 1981. As a small, non-standard fleet, with high running costs, no viable alternative use could be found for the Deltics, and all were withdrawn from service between January 1980 and December 1981. Six of the locomotives were saved for preservation.
Background
In 1955, the English Electric company produced a prototype diesel locomotive at the Dick, Kerr & Co works in Preston, officially named the DP1 but commonly known as Deltic. This prototype experimentally used two Napier Deltic engines which had been developed for marine applications. These unconventional engines were configured in a triangle with an opposed piston design. They ran at high speed more than twice that of conventionally configured engines, which made them very powerful relative to their size and weight, compared to the conventional diesel engines of the era. The locomotive used two of these engines, both rated at, which gave the locomotive a combined power output of for a weight of 106 tons.The other notable features of the locomotive were its large size by British standards and striking styling, which was inspired by the bulldog nosed American diesels of the era.
At the same time, the management of the British Railways Eastern Region were looking for a replacement for their pre-war fleet of Class A4 steam locomotives for use on top-link expresses on the East Coast Main Line. There was a contemporary proposal to electrify the ECML; however, this had a proposed completion date of 1970. Gerry Fiennes, the traffic manager of the ECML, believed that his expresses should be able to achieve an end-to-end average speed of in order to remain competitive with other forms of transport, he felt that they could not wait more than a decade for service improvements by electrification when the expanding road network was taking away passengers, and opted instead for high speed-diesel traction as an interim solution.
The management of the Eastern Region were however unimpressed by the performance of the best conventional diesels of the time, the English Electric Type 4, which for a weight of 133 tons, produced, which meant that their performance was no better than the steam locomotives they were supposed to replace. However, as the Deltic prototype had the necessary power and speed to achieve Gerry Fiennes's desired performance improvements, he persuaded British Railways to purchase a fleet of locomotives based on it.
Production
In March 1958, an order was placed with English Electric for a production fleet of 22 locomotives, replacing more than twice that number of steam locomotives including 35 A4 Pacifics; as steam locomotives require substantial time to clean, fuel, and fire, such a reduction in the number of units could be undertaken without a corresponding reduction in working availability. The full order was worth £3,410,000, working out at £155,000, per locomotive. Due to the complexity of the engine design, which needed specialist maintenance, the locomotives were purchased under a five year service contract, with English Electric agreeing to maintain them, including their engines and generators, for a fixed price; this was British Rail's first such contract. Additional Deltic engines were produced to enable engines to be exchanged regularly for overhaul while keeping the locomotives in service. English Electric trained the British Rail staff at the Doncaster Works in the techniques of maintaining the engines, and after the contract ended, they took over this responsibility.The production locomotives were built at the Vulcan Foundry at Newton-le-Willows; they were mechanically little changed from the prototype, but differed in appearance with a toned down styling, sporting a more sober colour scheme, and lacking the prototype's large headlight. The production Deltics were also 7 tons lighter than the prototype, weighing in at 99 tons, despite being nearly longer. They were originally planned to be delivered within a year from March 1960, but this deadline was not met, and they were delayed by a year, with the first Deltic entering revenue service in the summer of 1961, with a full service being introduced the following year.
The locomotives were assigned to three locomotive depots: Finsbury Park in London, Gateshead near Newcastle, and Haymarket in Edinburgh. Very soon, all were named; the Gateshead and Edinburgh Haymarket locomotives after regiments of the British Army from the North-East of England and from Scotland, respectively, while Finsbury Park followed the London and North Eastern Railway tradition of naming locomotives after winning racehorses.
At the same time, English Electric built a further ten locomotives which were later classified as the, which had single Napier Deltic engines; these gained the nickname "Baby Deltics" as they were in effect scaled down versions of the Deltics. These locomotives however, were far less successful in service than their larger cousins, and were all withdrawn by 1971.
British Rail service
The introduction of the Deltics was a step change in locomotive performance on the East Coast Main Line. Once the entire fleet was delivered into service in 1962, the timetable was accelerated, with the journey time from London to Edinburgh cut by one hour, from seven hours to six; this was enabled by the Deltics' ability to accelerate rapidly and maintain high speed with a heavy train over long distances. This matched the timing of the pre-war A4-hauled Coronation service, but was achieved without priority over other traffic unlike the earlier LNER train; it was also now the timing of normal standard fare expresses throughout the day, and not just a once-a-day premium fare express.From 1966 the infrastructure on the ECML was progressively upgraded to allow higher speeds in order to take better advantage of the Deltics' capabilities; this included upgrading the track, and other improvements such as the easing of sharp curves and improving the alignments through various stations. By 1973, these upgrades had allowed another half-hour to be cut from the London–Edinburgh journey time, with the Deltic-hauled Flying Scotsman, timetabled to reach Edinburgh in 5 ½ hours, with one stop at, achieving an average speed of over the entire journey.
On one of O. S. Nock's first Deltic runs he stated "once the tail of the train was over the 60 mph restriction the throttle was opened to the full, and the surge forward could be felt in the cab. Never previously had I felt a positive thrust in my back when in the second man's seat!" Nock went on to estimate that at 80 mph the locomotive was producing about 2,750 drawbar horsepower.
As early as 1963, Deltics were recorded exceeding 100 mph, Nock recording 100 mph for 16 miles south of Thirsk with a maximum of ; he went on to say that such speeds in 1963 were "terrific".
The ultimate Deltic performance came on 2 February 1978 with a run on the 07:25 from Newcastle to King's Cross. In some respects, the run was set up but the speeds were record-breaking. The locomotive was 55 008 The Green Howards; it was hauling 10 coaches, and on the leg from York to London it achieved a timing of 137 min 15 sec. This included various signal stops and other enforced speed reductions; the net time is estimated at 115 min 45sec, an average of start to stop. The train achieved on the flat between Darlington and York, at Offord and whilst descending Stoke Bank.
From 1978, the ECML was upgraded to allow 125 mph running, in order to accommodate the InterCity 125s, and although the Deltics were still officially limited to 100 mph, in practice they frequently exceeded this in service.
The fastest regular scheduled Deltic service was the Hull Executive between London and, which was inaugurated in May 1978. The down working of this service achieved an average speed of from King's Cross to its first stop at, making it the fastest regular locomotive-hauled train in Britain at the time. Maintaining this schedule required sustained periods of running above 100 mph. The published logs of some of these runs show that Deltics cruised at up to. The Hull Executive was one of the last top-link workings by a Deltic, until 1981, when this service was taken over by HST's.
The Railway Performance Society estimate that on modern infrastructure a realistic Deltic-hauled schedule from King's Cross to Edinburgh would be around 4 hours 57 minutes. This would be for a train of 11 coaches and include a stop at Newcastle, the latter city being reached in a scheduled 3 hours 6 minutes.
The Deltics had arrived from the manufacturer painted in two-tone green, the dark BR green on top, with a narrower strip of a lighter, lime green along the bottom. This helped to disguise the bulk of the locomotive body. The cab window surrounds were picked out in cream-white. Although delivered without it, they all soon sported the bright yellow warning panel at each end common to all British diesel and electric locomotives, to make them more conspicuous. By 1966 the InterCity branding was introduced, and the Deltics began to be painted in corporate Rail Blue with yellow ends, the change generally coinciding with a works repair and the fitting of air brake equipment, the locomotives originally having only vacuum braking. In the early 1970s they were fitted with Electric Train Heating equipment to power Mark 2 air-conditioned coaches, while a couple of years later, with the introduction of BR's TOPS computer system, they were renumbered 55 001 to 55 022.