SR Leader class
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| File:SR Leader 05.jpg Photograph of 36001 taken during a test run at Oxted in November 1949 | |||||||||||||||||||||||||||
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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 operational drawbacks associated with such locomotives. The design was started in 1946 to replace the ageing fleet of M7 class locomotives still in operation on the Southern Railway (SR). The development of the design continued after the nationalisation of the railways in 1948 under the auspices of British Railways (BR).
The Leader project became part of Bulleid's desire to modernise the steam locomotive along the principles based upon experience with the Southern Railway's fleet of electric stock.[2] In finalising the design, Bulleid saw that changes regarding the labour intensity of steam operation were being mooted, and in response the new locomotive was to push forward the boundaries of steam power in the little time available before nationalisation in 1948.
The design incorporated many novel and untried features such as the use of thermic siphons, bogies and cabs at either end of the locomotive, although these innovations were some of the reasons why the project was discontinued in the early 1950s. Only one locomotive was completed for trial purposes, though four more were in varying states of completion. The operational locomotive was trialled on the former Southern Railway network around Brighton. Because of problems with the various innovations, indifferent reports on performance and political pressure surrounding spiraling development costs, all locomotives were scrapped by 1951.
Background
The basis of the Leader design originated from a 1944 review of the Southern Railway's steam locomotive fleet, resulting in a Southern Railway design brief which called for a high-powered locomotive requiring little maintenance.[2] The brief also stipulated that the locomotive would be used on both passenger and freight trains, requiring high route availability. An initial design proposal by Bulleid was based upon his SR Class Q1 locomotive, which had proved easy to maintain in service.[3] As the proposal progressed, Bulleid saw that certain tasks associated with traditional steam locomotives could be omitted by sharing several characteristics with the contemporary Southern electric locomotives.[2] However, one of the subsequent designs of a 0-4-4-0 wheel arrangement had an unacceptably high axle loading of 20 tons (20.4 tonnes), which increased the risk of damaging the Southern Railway's track.[4] By developing the proposal further, Bulleid settled for a 0-6-6-0 design of bogied locomotive that spread the weight more evenly over the rails and reduced the axle-loading.[5]
Design details
A series of initial designs were presented to the Southern Railway management by Bulleid that incorporated double-ended running, enabling the locomotive driver to have maximum visibility in either direction without a boiler or tender obscuring his view. This eradicated the need to use a turntable for turning the locomotive around, although the initial designs were turned down by the operating department due to problems with welding technique.[6] The design that was accepted by the management included two 0-6-0 steam bogies with weight-saving sleeve valves and chains to couple the driving axles, as used on Bulleid's Pacifics. A communication corridor was included for the driver to access both cabs from within the locomotive, though this meant offsetting the boiler, causing problems later on.[7] The firebox was located near the centre of the locomotive and fed by the fireman in a third cab.[8] This cab was linked to both driving cabs by the communication corridor alongside the off-centre boiler and tender, and the entire ensemble was placed on a common frame (thus it is often referred to as an 0-6-6-0 tank engine).[9]
The construction of the Leader prototype took place at Brighton railway works, and began in 1946.[6] An initial order of five locomotives was placed straight from the drawing board in 1946 with a further 31 locomotives in 1947, though this was merely a gesture on the part of the Southern Railway with nationalisation approaching.[10] The latter order was cancelled after nationalisation to allow trials to be carried out on the prototype.[10]
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.[11] The valve gear used the unusual sleeve valve arrangement that was also tested on the ex-LB&SCR H1 class Hartland Point in parallel to the construction of the first Leader locomotive.[11] The Leader was the first steam locomotive design to use 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.[12]
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.[6] This included oscillating gear that gave a 25-degree axial movement to the sleeves, allowing even lubrication of the moving parts.[13] However, this resulted in an over-complicated mechanism that was difficult to maintain, perpetuating the seizures it was meant to eradicate. This feature was removed from both bogies of the prototype as the trials progressed.[14] Another innovative feature of the steam bogie design was the ability to interchange them when faults occurred, an easy operation for maintenance staff when compared to the complexities of overhauling a regular steam locomotive's motion.[4]
The three cylinders of each bogie were cast in mono-block format, each surrounded by two annular inlet steam chests and a single large outlet steam chest.[13] These had the added function of keeping the cylinder heated by hot steam to maintain the temperature and pressure of steam entering the cylinders. However, these castings were difficult to machine accurately.[13] The steam-sealing arrangements needed for this system were also complex, with each of the six cylinders and valve sleeves requiring 24 sealing rings.[12]
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, and proved to be the least problematic area of the entire design.[11] The boiler pressure was set at (280 psi (1.93 MPa)), and each was fitted with four thermic siphons from beneath the firebox to pre-heat water entering the boiler, which were used to great effect on Bulleid's Merchant Navy, West Country and Battle of Britain Classes.[15]
The Leader had a "dry lining" firebox, where it was not surrounded on top and sides by a 'jacket' of water as in normal practice.[16] It was constructed of welded steel, and used firebricks instead of water for insulation, which was novel but troublesome solution to dry-lining the firebox.[6] These had the effect of reducing the grate area from 47 square feet (4.4 m2) to 25.5 square feet (2.37 m2), and concentrated the fire in a small area.[16] The firehole door was offset to the left of the boiler backhead, and was to provide difficulty for the fireman to add coal to the fire.[17] The firebox was not initially equipped with a firebrick arch, although one was retro-fitted during the summer of 1950.[18] The arch was problematic as it promoted the tendency for flames to enter the cab at high outputs, a situation made worse by the narrowing of the firebox area.[18]
The smokebox design had an inherent problem in maintaining a constant vacuum. This was a result of another Bulleid labour-saving innovation, a sliding hatch controlled from the front cab that enabled ash to be cleaned out through a chute onto the track when on the move.[19] The problem lay with ash manifesting itself around the edges of the slide, allowing air to leak into the smokebox, therefore reducing the overall efficiency of the locomotive.[16] The fierce blast from the exhaust also meant that ash and embers were ejected into the atmosphere, creating a potential lineside fire hazard.[20]
The boiler, firebox, smokebox and tender were encased in steel sheeting that resembled a modern diesel locomotive, and was a major departure from traditional steam locomotive design.[21] Ease of maintenance was the reason for this feature, as it allowed the engine to be cleaned using a carriage-washing plant.[21]The tender was designed to carry 4 tons (4.06 tonnes) of coal and 4000 imperial gallons (18,160 litres) of water, and was covered by a tarpaulin to prevent water ingress into the fireman's cab.[1] Entry into the locomotive was by way of ladders leading up to sliding doors, although due to the bogie design, the climb into the fireman's cab necessitated clambering over the oilbath casing.[16]
Construction history and trials
The prototype Leader emerged from Brighton railway works as locomotive number 36001 in June 1949, and was immediately put into service trials in the south-east of England. The official trial records kept at Brighton works reported varying degrees of success and failure on the runs undertaken.[22] However, the results of the trials as reported to British Railways headquarters at Marylebone were 'conspicuous by the absence of praise' for the strengths of the Leader, namely the boiler, braking system and total adhesion provided by the two bogies.[23] Several theories have been put forward regarding this state of affairs, the most plausible being that the more conservative members of the railway workforce at Brighton felt that the design was too revolutionary, and were keen to maintain the status quo.[24]
The other four members of the initial order made by the Southern Railway, numbers 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 and were ready for fitting.[6]
Operational details
Following trials lasting over a year, 36001 was shown to have a number of 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. The brake release was too slow in service for use on tight schedules despite the brake application being noted as the best used on a Bulleid design.[25]
Throughout 36001's trials the firebrick lining provided a constant problem by continually collapsing into the fire.[8] The firebricks were then replaced with cast iron substitutes that melted in the intense heat of the firebox, and were in turn replaced with the thicker 9 inches (23 cm) firebricks. [6] Some of the firemen allotted to the Leader complained about cramped conditions in the centre cab of the locomotive, a situation made worse by flames entering the cab from the firebox at high outputs.[20] It was an enclosed space that was constantly hot, and the single fireman's entrance door on the side of the locomotive was left open during travel to promote ventilation.[8] The door into the fireman's cab also attracted criticism, blocking emergency egress if the locomotive overturned onto that side.[16]
Due to the offset boiler and tender, the locomotive's centre of gravity was shifted to one side. Experiments had to be undertaken to balance the locomotive by filling the linking corridor with large quantities of scrap metal. This was latterly replaced with the fabrication of a raised floor covering ballast material. These necessary modifications meant that the engine exceeded the total weight limit of 150 tons, severely limiting the design's route availability during testing.[26] Another problem related to this was the fact that despite being a tall locomotive at 12 feet 11 inches (3.94 m), the cab ceilings were relatively low. The cab at the smokebox end of the locomotive suffered a similar issue to the fireman's cab, in that it was prone to heat. This resulted in the locomotive being used in 'reverse', ie. tender-first, to circumvent this problem.[27] This was because the rear cab of the Leader was next to the water tank and coal chute, and therefore away from the hot gases that circulated inside the smokebox, heating up the front cab.
Despite these problems, the locomotive displayed outstanding steaming characteristics, and total traction from the two power bogies when on trial runs.[28] When fired properly, the locomotive was capable of keeping up with the schedules, even running ahead on occasions. However, operational difficulties when stopping for water tended to lose any time advantages gained, and affected the performance figures when published.[29] Despite hauling test trains over the Central section of the former Southern Railway, the Leader prototype was never used on a revenue-earning service because of the risk of failure of the valve gear, and the adverse publicity this would cause for British Railways.[30]
End of the project
The whole concept was quietly dropped in 1951 after Bulleid departed British Railways to become Chief Mechanical Engineer of Córas Iompair Éireann (where he produced a peat-burning locomotive to a similar concept), and all five were scrapped.[3] The culmination of the project was a £178,865 5s 0d bill for the taxpayer, though when the press reported the story as late as 1953, £500,000 was claimed to have been wasted on the project.[31] R. G. Jarvis, who was placed in charge of the project after Bulleid's departure, insisted that the locomotive required an entire re-design to solve the problems of the original concept. Despite the many problems, the design concept was a bold attempt at pushing back the boundaries of contemporary steam locomotive design, and if successful, would have prolonged the life of steam on Britain's Railways.[3] 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 sold at an auction, though it was never fitted in service.[32]
Livery and numbering
Southern Railway
When the project was under the auspices of the Southern Railway, 36001 would have been numbered CC101.[1] 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 Southern Railway 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.[33] Since the design has six driving axles, the numbering would have been CC101–CC105 with the initial batch, the final number being the locomotive identifier.
British Railways
Operational livery was ex-works photographic grey with red and white lining. The British Railways 'Cycling Lion' crest was also used, though after the works photograph this was painted over for no explanation.[6] Numbering was the British Railways standard system, in the 36001 series.[6] If the class had gone into full production, the locomotives would have been painted in British Railways Mixed Traffic/Freight Black livery with red and white lining. 36001 was initially painted in this livery, but this preceded the official works photograph and was subsequently repainted in photographic grey livery.[34]
References
Notes
- ^ a b c Bulleid, p. 143
- ^ a b c Bulleid, p. 135
- ^ a b c Day-Lewis, The Leader locomotive
- ^ a b Bulleid, p. 129
- ^ Bulleid, p. 136
- ^ a b c d e f g h Haresnape, Section 4
- ^ Robertson, p. 116
- ^ a b c Harris, Steam Days (1994), p. 115
- ^ Robertson, p. 42
- ^ a b Robertson, p. 46
- ^ a b c Tuplin: Railway World (1965), p. 413
- ^ a b Robertson, p. 47
- ^ a b c Tuplin: Railway World (1965), p. 414
- ^ Robertson, p. 77
- ^ Robertson, p. 25
- ^ a b c d e Harris, Steam Days (1994), p. 116
- ^ Bulleid, p. 145
- ^ a b Harris, Steam Days (1994), p. 117
- ^ Tuplin: Railway World (1965), p. 415
- ^ a b Robertson, p. 95
- ^ a b Bulleid, p. 125
- ^ Cox, p. 18
- ^ Cox, p. 19
- ^ Robertson, p. 151
- ^ Bulleid, p. 151
- ^ Cox, p. 16
- ^ Robertson, p. 87
- ^ Robertson, p. 158
- ^ Robertson, p. 156
- ^ Robertson, p. 150
- ^ Sunday Dispatch, 18 January 1953
- ^ Great Central Railwayana Auctions (2007) Auction Catalogue: Great Central Railwayana, 6 October 2007, Retrieved February 17, 2009. Sold for £1050, see Lot 24.
- ^ Burridge, p. 60
- ^ Robertson, p. 37
Bibliography
- Bulleid, H. A. V.: Bulleid of the Southern (Hinckley: Ian Allan Publishing, 1977) ISBN 071100689X
- Burridge, Frank: Nameplates of the Big Four (Oxford Publishing Company: Oxford, 1975) ISBN 0902888439
- Cox, E. S.: Locomotive Panorama (London: Ian Allan, 1965–66), Vol. 2
- Day-Lewis, S.: Bulleid, Last Giant of Steam (London: George Allen & Unwin, 1964)
- Haresnape, Brian: Bulleid Locomotives: A Pictorial History
- Harris, Michael: "Firing Bulleid's 'Leader'" (Steam Days: 66, 1994)
- Robertson, Kevin: The Leader Project: Fiasco or Triumph? (Oxford: Oxford Publishing Company, 2007) ISBN 0860936066
- Sunday Dispatch, 18 January 1953
- Tuplin, W.A.: "The ill-fated 'Leader'" (Railway World: 26, 1965)
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)