SR Leader Class

Infobox Locomotive
powertype=Steam
name = SR/BR Leader Class Robertson, Kevin: "The Leader Project: Fiasco or Triumph?" (Oxford: Oxford Publishing Company, 2007) ISBN 0860936066]


caption = 36001 at Oxted, taken by British Railways
designer = Oliver Bulleid
builder = SR Brighton Works
builddate = 1946–1949 (only one completed)
totalproduction = 5
whytetype = 0-6-6-0
gauge = RailGauge|ussg
driversize = 5 ft 1 in (1.55 m)
length = 67 ft (20.26 m)
weight = 150 tons (152.5 tonnes)
fueltype = coal
fuelc

waterc

cylindercount = 6 (3 in each bogie)
cylindersize = 12.25 in × 15 in (311 mm × 381 mm)
firearea = 25.5 ft² (2.29 m²)
boilerpressure = 280 lbf/in² (1930 kPa)
tractiveeffort = 30,000 lbf (Approx.) (133.44 kN)
railroad=Southern Railway (Great Britain), Southern Region of British Railways
locale=Great Britain
railroadclass=Not known| The SR Leader Class was a class of experimental 0-6-6-0 articulated locomotive, produced to the design of the innovative engineer Oliver Bulleid. The design was an attempt to extend the life of steam traction on Britain's railways by eliminating many of the drawbacks associated with such operation.

The class incorporated many novel and untried features that were innovative, but would ultimately provide an excuse to discontinue the project. Only one was ever completed, though several others were in varying stages of completion. The solitary example was to trialled on the ex-Southern Railway network around Brighton. Due to indifferent reports on performance during the trials, all had been scrapped by 1951.

Background

The "Leader" design spawned from a review in 1944 of the Southern's steam locomotives. The resultant design by Bulleid was initially based upon his SR Class Q1. Day-Lewis, S.: "Bulleid, Last Giant of Steam" (1964)] As the design progressed, Bulleid saw that certain tasks associated with traditional steam locomotives could be omitted in a design that shared many characteristics with contemporary Southern electric locomotives. Bulleid, H. A. V.: "Bulleid of the Southern" (Hinckley: Ian Allan Publishing, 1977) ISBN 071100689X] One of the initial designs, of 0-4-4-0 wheel arrangement had a high axle loading of 20 tons. [ Southern E-Group (2005) [http://www.semgonline.com/steam/leader_01.html] , Retrieved 13 May 2007. For information on the dropped 0-4-4-0 wheel arrangement.] In consequence, Bulleid settled for an 0-6-6-0 design of bogied locomotive with duplicate controls for the driver in cabs at each end.

Design details

The design consisted of two 0-6-0 steam bogies utilising weight-saving sleeve valves and chain-driven valve gear to couple the driving axles, as used on Bulleid's Pacifics. The firebox was at the centre of the locomotive, fed by the fireman in a third cab.Harris, Michael: "Firing Bulleid's 'Leader'" ("Steam Days": 66, 1994) 115-18] This was linked to both driving cabs by a corridor along the side of the boiler. The boiler and tender were placed on a common frame (thus it is often referred to as an 0-6-6-0 tank engine), and were positioned off-centre to enable the provision of the connecting corridor.

The "Leader" project was a combination of Bulleid's desire to totally modernise the steam locomotive with principles based upon experience, with the electric locomotives that were operating on the Southern's Eastern Section. A design opportunity presented itself with the motive power department's call for a new locomotive design to replace the Southern Railway's ageing fleet of small tank M7 engines. Bulleid realised that changes were being mooted concerning the labour intensity of steam operation, and the new design was to push forward the boundaries of contemporary locomotive design in the little time available before nationalisation in 1948.

Several designs were presented by Bulleid, being variations of his previous Q1 design that could achieve double-ended running, eradicating the need to use a turntable to turn the locomotive round, though these were turned down by the operating department.Haresnape, Brian: "Bulleid Locomotives: A Pictorial History", Section 4] The final design brief that spawned the "Leader" called for a high-powered machine that required little in the way of maintenance, and could be driven from both ends. The design was designated "all-purpose" in that it could also be utilised on both passenger and freight trains, meaning that a high route availability was needed. In consequence, a twin-bogied chassis design was drawn up by Bulleid that also entailed the provision of a communication corridor for the driver to access both cabs from within the locomotive, resulting in an offset boiler that was to have severe consequences later on.

The construction of the "Leader" prototype took place at Brighton railway works, beginning in 1947.An initial order of five locomotives was placed straight from the drawing board in 1946, with a further order of 31 locomotives in 1947, though this was merely a last gesture on the part of the Southern with nationalisation on the cards. The latter order was cancelled post-nationalisation to allow experimentation to be carried out.

Bogie and cylinder design

Each of the two bogies had three cylinders, with the driving wheels connected by chains enclosed in an oil-bath, based upon Bulleid's chain-driven valve gear on his Pacific designs.Tuplin, W.A.: "The ill-fated 'Leader'" ("Railway World": 26 1965), 413-15] The valve gear used the unusual sleeve valve arrangement that was being tested on the ex- LBSCR Atlantic "Hartland Point" as the "Leader" was under construction.Tuplin, W.A.: "The ill-fated 'Leader'" ("Railway World": 26 1965), 413-15] The "Leader" was the first steam locomotive design to attempt the use of a form of sleeve valve since Cecil Walter Paget's locomotive of 1908, though the concurrent testing of the design on "Hartland Point" hints at the rushed nature of the locomotive's conception.

The use of sleeve valves and oil baths to lubricate the moving parts of the engine units were inspired by contemporary internal combustion engine practice. The decision to include oscillating gear that added a 25-degree axial movement to the sleeves to avoid seizure by allowing even lubrication of the moving parts was also based upon motoring practice. However, this resulted in an over-complicated mechanism that was difficult to maintain, causing the seizures that it was meant to eradicate. This feature was removed from both bogies as the trials progressed. Another innovative feature of the bogie design was Bulleid's insistence on making them interchangeable, allowing new bogies to replace those due for overhaul..

The cylinders were cast in mono-block format, each one surrounded by two annular inlet steam chests and a single large outlet steam chest. These had the added function of keeping the cylinder heated by hot steam, to maintain the temperature, and therefore the pressure, of steam entering the cylinders. However, the castings proved difficult to machine accurately. The sealing arrangements in this system were highly complex, with each cylinder and valve sleeve set having 24 sealing rings, 144 rings in total.

Boiler, firebox and smokebox design

The boiler was the culmination of lessons learned with the Pacifics, and was a prolific steam-raiser. All "Leader" boilers were constructed at Eastleigh, proving to be the least problematic area of the entire project. The boiler pressure was rated at 280 psi and was fitted with four thermic siphons from beneath the firebox to pre-heat the water entering the boiler, which had previously been used to great effect in Bulleid's Merchant Navy, West Country and Battle of Britain Classes.

The "Leader" had a "dry lining" firebox, where it was not surrounded on top and sides by a water "jacket.".It was constructed of welded steel, and used firebricks instead of water for insulation, which proved novel but troublesome. These had the effect of reducing the grate area from 47 to 25.5 square feet, concentrating the fire in a small area.The firehole door was offset to the left, providing further difficulties for the fireman.

The firebox was not initially equipped with a firebrick arch, although one was retro-fitted during the summer of 1950.The arch provided problems as it promoted the tendency for flames to enter the cab at high outputs.
Thermic syphons were also utilised, having been successfully incorporated into the earlier Pacific designs.

The lack of a constant vacuum in the smokebox was a result of another Bulleid labour-saving innovation, a sliding hatch controlled from the front cab enabling ash to be cleaned out through a chute when on the move. The problem lay in the fact that air constantly entered the smokebox once ash manifested itself around the edges of the slide, reducing the overall efficiency of the locomotive.The fierce blast from the exhaust also meant that ash and embers were ejected into the atmosphere, leading to potential fire hazards.

The body was encased in steel sheeting, resembling a modern diesel locomotive, representing a major departure from traditional steam locomotive design. Ease of maintenance was in mind with this feature, to allow the engine to be cleaned using a carriage-washing plant.

Construction history and trials

The prototype, 36001, emerged from Brighton railway works in June 1949, and was immediately put into service trials in the South East of England. The official trial records kept at Brighton reported varying degrees of success as well as failure on the runs undertaken.Cox, E. S.: Locomotive Panorama (London: Ian Allan, 1965–66), Vol. 2, p. 18] The results of these trials as reported to BR headquarters at Marylebone were 'conspicuous by the absence of praise' for the strengths of the "Leader," namely the boiler, braking system and total adhesion. Cox, E. S.: Locomotive Panorama (London: Ian Allan, 1965–66), Vol. 2, p. 19] Several theories have been put forward regarding this state of affairs, the most plausible being that the conservative elements of the railway workforce at Brighton felt that the design was too revolutionary, and were keen to maintain the status quo.

The other members of the class, 36002–5, were at varying stages of construction by the end of the development period. 36002 was almost complete, 36003 was without its outer casing, and 36004–5 were little more than sets of frames, although most of their major components had been constructed at Eastleigh and Brighton.

Operational details

Following trials lasting over a year, 36001 was shown to have a number of inherent flaws, including heavy coal and water consumption, mechanical unreliability, untenable working conditions for both fireman and driver, and uneven weight distribution on the bogies. It was tested around Brighton and Eastleigh using an LNER Dynamometer car, where good running was experienced at high costs in fuel and effort on the part of the fireman. Braking was also relatively poor, with its release being too slow for tight schedules, although brake application has been noted as the best used on a Bulleid design.

Throughout 36001's trials the firebrick lining provided a constant problem through collapse into the fire.These firebricks were replaced with cast iron substitutes that melted in the intense heat of the firebox, which were in turn replaced with the thicker 9” firebricks. Frequent complaints were made by the fireman of the cramped conditions within his cab at the centre of the locomotive, a situation made worse by the problem of flames from the firebox entering the cab at high outputs. It was a highly enclosed space that was constantly hot, and photographic evidence shows that the single entrance door on the side of the locomotive was left open during travel to promote ventilation.The single door for the fireman also promoted criticism in the event of the locomotive turning over and blocking emergency egress. Due to the offset nature of the boiler, experiments were undertaken to balance the locomotive by filling the linking corridor with a large quantity of scrap metal. This was latterly replaced by the fabrication of a raised floor covering ballast material. These necessary modifications meant that the engine exceeded the weight limit of 150 tons, severely limiting the design's route availability during testing.Cox, E. S.: Locomotive Panorama (London: Ian Allan, 1965–66), Vol. 2, p. 16]

End of the project

The whole concept was quietly dropped in 1951 after Bulleid had departed British Railways to become Chief Mechanical Engineer of Córas Iompair Éireann (where he produced a similar peat-burning locomotive), and all five were scrapped. This resulted in a project that utilised £178,865 5s 0d of the taxpayer's money, though when the press reported the story as late as 1953, £500,000 was claimed to have been wasted on the project. ["Sunday Dispatch", 18 January 1953] R. G. Jarvis, who was placed in charge of the project upon Bulleid's departure, emphasised that the locomotive would have required an entire re-design to solve the problems of the original concept. No members of the "Leader" class survived the 1950s, and only the numberplate of 36001 is located in the National Railway Museum. In 2008, a locomotive builder's plate intended for the locomotive was auctioned, though it was never fitted in service.

Livery and numbering

outhern Railway

When the project was under the auspices of the Southern Railway, 36001 would have been numbered "CC101." Bulleid advocated a continental style of locomotive nomenclature, based upon his experiences at the French branch of Westinghouse Electric before the First World War, and those of his tenure in the rail operating department during that conflict. The SR number followed an adaptation of the UIC classification system where "C" refers to the number of driving axles – in this case three on each bogie.Burridge, Frank: "Nameplates of the Big Four" (Oxford Publishing Company: Oxford, 1975) ISBN 0902888439] Since the design has six driving axles, the numbering would have been "CC101–CC105" on the initial batch, the number being the identifier.

Post-1948 (nationalisation)

Operational livery was ex-works photographic grey with red and white lining. The 'Cycling Lion' crest was also utilised, though after the works photograph this was painted over with no adequate explanation. Numbering was the BR standard system, being allocated the 36001 series.

Had the class gone into full production, the locomotives would have been painted in BR Mixed Traffic/Freight Black livery with red and white lining. 36001 was initially painted as such with photographic evidence to support this, but this preceded the official works photograph, and was subsequently repainted in photographic grey livery.

Footnotes

Further reading

*Ian Allan ABC of British Railways Locomotives, 1950 edition
*Carter, Ernest F.: "Unusual Locomotives" (Frederick Muller Ltd., 1960)
*Nock, O.S.: "Southern Steam" (Newton Abbot: David and Charles, 1972)
*Robertson, Kevin: "Leader and Southern Experimental Steam" (Stroud: Alan Sutton Publishing, 1990)
*Tufnell, Robert: Prototype Locomotives (Newton Abbot: David and Charles, 1985)

External links

* [http://www.semgonline.com/steam/leader_01.html “Leader” class locomotive]