SR Leader class
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| File:SR Leader 05.jpg Class doyen 36001 taken by British Railways at Oxted. | |||||||||||||||||||||||||||
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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 represents an attempt to extend the life of steam traction on Britain's railways by eliminating many of the drawbacks associated with such operation.
In consequence, 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 subjected to trial 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 Railway's operational fleet of steam locomotives. The resultant design made by Bulleid was initially based upon his SR Class Q1.[2] 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.[3] One of the initial designs, of 0-4-4-0 wheel arrangement had a high axle loading of 20 tons.[4] In consequence, Bulleid settled for an 0-6-6-0 design of bogied locomotive with duplicate controls for the driver in cabs at either end. The "Leader" Class was born.[3]
Construction history
The resultant locomotive design consisted of two 0-6-0 steam bogies utilising weight-saving sleeve valves and chain-driven valve gear to couple the driving axles, a practice used on Bulleid's pacifics..[3] The firebox was located at the centre of the locomotive, fed by the fireman in a third cab.[5] This in turn 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.[1]
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 already plying their trade on the Southern Railway's Eastern Section.[3] 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.[1] Bulleid had astutely 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. Bulleid evidently wished to showcase the continued potential of steam traction as a viable option in an age where air travel was increasingly common.
Several designs were presented by Bulleid, being variations of his previous Q1 design that could achieve double-ended running in equal measure, though these were turned down by the operating department.[6] 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, eradicating the need to use a turntable to turn the locomotive around.[3] The design was also designated as "all-purpose," in that it could also be utilised in passenger/freight work, 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.[1]
The construction of the "Leader" prototype took place at Brighton railway works, beginning in 1947.[6] 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.[1] The latter order was cancelled post-Nationalisation to allow experimentation to be carried out.[1]
Bogie 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.[7] The valve gear also used the unusual sleeve valve arrangement that was being tested on the ex- LBSCR Atlantic Hartland Point as the "Leader" was under construction.[7] 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.[1]
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] 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. [7] However, this resulted in an over-complicated mechanism that was difficult to maintain, actually causing the seizures that they were meant to eradicate. This feature was eventually removed from both bogies as the trials progressed.[1] Another innovative feature of the bogie design was Bulleid's insistence on making them interchangeable, allowing new bogies to replace those due for overhaul.[3] However, the fact that only a handful were built meant that such measures proved ineffective.
Cylinder design
The cylinders were cast in mono-block format, each one surrounded by two annular inlet steam chests and a single large outlet steam chest.[7] These had the added function of keeping the cylinder heated by hot steam, to reduce the rapid cooling of steam in the cylinders that can cause priming. However, the castings proved difficult to machine accurately.[7] The sealing arrangements in this system were highly complex, with each cylinder and valve sleeve set possessing 24 sealing rings; 144 rings for the entire engine.[1]
Boiler, firebox and smokebox design
The boiler was the culmination of lessons learned with the pacifics, and was a prolific steam-raiser, and all "Leader" boilers were constructed at Eastleigh, proving to be the least problematic area of the entire project.[7] 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 SR Merchant Navy Class and SR West Country Class/Battle of Britain Class.[1]
The "Leader" equipped with a "dry lining" firebox, where it was not surrounded on top and sides by a water "jacket.".[5] It was constructed of welded steel, and used firebricks instead of water for insulation, which proved novel but troublesome.[6] These had the effect of reducing the grate area from 47 to 25.5 square feet, concentrating the fire in a small area..[5] The firehole door was also offset to the left, providing further difficulties for the fireman.[3]
The firebox was also not initially equipped with a firebrick arch, although one was retro-fitted during the summer of 1950.[5] The arch provided problems as it promoted the tendency for flames to enter the cab at high outputs.[5] Thermic syphons were also utilised, having been successfully incorporated into the earlier pacific designs.[6]
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.[7] 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.[5] The fierce blast from the exhaust also meant that ash and embers were ejected into the atmosphere, leading to questions surrounding the potential fire hazards.[1]
The overall body was encased with steel sheeting, resembling a modern diesel locomotive, representing a major departure from traditional steam locomotive design.[3] Ease of maintenance was in mind with this feature, due to the fact that its purpose was to allow the engine to be cleaned using a carriage washing plant.
Livery and numbering
The Southern
Originally, when the project was still under the auspices of the Southern Railway, 36001 would have been numbered "CC101."[3] 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.[8] However, since the locomotive design has six driving axles, the nomencalture 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.[6] Numbering was the BR standard system, being allocated the 36001 series.[6]
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, however this had preceded the official works photograph, and was subsequently repainted in photographic grey livery.[1]
The trials
The prototype, 36001, was outshopped from Brighton railway works in June 1949, and was immediately put under 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.[9] However, 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. [9] Several theories have been made 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.[1]
As a result of this, the other members of the class, numbers 36002-5 were at varying stages of construction by the end of the development period. Number 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.[6]
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, tempered by 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 a relatively poor feature of the design, with its release being too slow for tight schedules, although brake application has been noted as the best used on a Bulleid design.[2]
Throughout the trials of No. 36001, the firebrick lining provided a constant problem through collapse into the fire.[5] 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. [6] 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 aforementioned problem of flames from the firebox entering the cab at high outputs.[1] 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.[5] The utilisation of a single door for the fireman also promoted criticism in the event of the locomotive turning over and blocking emergency egress.[5]
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.[9]
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 subsequently, all five were scrapped. [2] This resulted in a project that utilised £178,865/5s 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.[10] R. G. Jarvis, who was placed in charge of the design upon Bulleid's departure emphasised the fact that the locomotive 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.
References
- ^ a b c d e f g h i j k l m n Robertson, Kevin: The Leader Project: Fiasco or Triumph? (Oxford: Oxford Publishing Company, 2007) ISBN 0860936066 Page 134 For information on problems regarding firebox. Cite error: The named reference "Robertson" was defined multiple times with different content (see the help page).
- ^ a b c Day-Lewis, S.: Bulleid, Last Giant of Steam (1964)
- ^ a b c d e f g h i Bulleid, H. A. V.: Bulleid of the Southern (Hinckley: Ian Allan Publishing, 1977) ISBN 071100689X Cite error: The named reference "Bulleid" was defined multiple times with different content (see the help page).
- ^ Southern E-Group (2005)[1], Retrieved May. 13, 2007. For information on the dropped 0-4-4-0 wheel arrangement.
- ^ a b c d e f g h i Harris, Michael: "Firing Bulleid's 'Leader'" (Steam Days: 66, 1994) 115-18 Cite error: The named reference "Harris" was defined multiple times with different content (see the help page).
- ^ a b c d e f g h i Haresnape, Brian: Bulleid Locomotives: A Pictorial History (Hinckley: Ian Allan Publishing, 1979) ISBN 0711015392 Cite error: The named reference "Haresnape" was defined multiple times with different content (see the help page).
- ^ a b c d e f g Tuplin, W.A.: "The ill-fated 'Leader'" (Railway World: 26 1965), 413-15
- ^ Burridge, Frank: Nameplates of the Big Four (Oxford Publishing Company: Oxford, 1975) ISBN 0902888439
- ^ a b c Cox, E. S.: Locomotive Panorama (London: Ian Allan, 1965/6), Vol. 2
- ^ Sunday Dispatch, January 18 1953
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)