SR Leader class – PDH Multiplexer Manufacturer – Fiber Optic Multiplexer Manufacturer
Article by jekky
(2946, ‘Background The basis of the Leader 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 to replace the ageing fleet of M7 class tank engines The brief also stipulated that the locomotive would be used on both passenger and freight trains requiring high route availability Bulleid proposed an initial design based on his SR Q1 class locomotive which had proved easy to maintain in service As the proposal progressed Bulleid saw that certain tasks required with conventional steam locomotives could be eliminated by adopting some of the features of the contemporary Southern electric locomotives However one of the subsequent designs of a 0 4 4 0 wheel arrangement had an unacceptably high axle loading of 20 160 tons 20 4 160 tonnes which increased the risk of damaging the Southern Railway s track By developing the proposal further Bulleid settled for a 0 6 6 0 design of bogied locomotive which spread the weight more evenly over the rails and reduced the axle loading Design Works diagram of the Leader A series of initial ideas were presented to the Southern Railway management by Bulleid that incorporated double ended running giving the locomotive driver maximum visibility in either direction without a boiler or tender obscuring his view The need for a turntable to turn the locomotive around was therefore eliminated although the initial designs were rejected by the operating department because of problems with welding technique The accepted design 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 The boiler was offset to provide space for a communication corridor allowing the driver to access both cabs without leaving the locomotive an arrangement which led to later problems The firebox near the centre of the locomotive was fed by the fireman from a third cab linked to both driving cabs by the communication corridor The entire ensemble was placed on a common frame and thus often referred to as an 0 6 6 0 tank engine The Leader prototype was constructed at Brighton railway works and work began in 1946 An initial order of five locomotives was placed straight from the drawing board in 1946 and a further 31 were ordered in 1947 although with nationalisation looming this was merely a gesture The latter order was cancelled after Southern Railway was taken into public ownership to allow trials to be carried out on the prototype 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 locomotives The valve gear used the unusual sleeve valve arrangement that was also tested on the ex LB amp SCR H1 class Hartland Point in parallel with the construction of the first Leader locomotive The Leader was the first steam locomotive to use a form of sleeve valve since Cecil Paget s locomotive of 1908 and the concurrent testing of the principle on Hartland Point hints at the rushed nature of the locomotive s conception The locomotive sat on the unusual Bulleid Firth Brown wheels which were lighter yet stronger than the spoked equivalent The use of sleeve valves and oil baths to lubricate the moving parts of the engine units was inspired by contemporary internal combustion engine practice This included oscillating gear that gave a 25 degree axial movement to the sleeves allowing even lubrication of the moving parts 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 Another innovative feature of the steam bogie assembly 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 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 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 The steam sealing arrangements needed for this system were also complex with each of the six cylinders and valve sleeves requiring 24 sealing rings Boiler firebox smokebox and casing design The Leader boiler and firebox showing the offset firehole door position dotted Also visible are two of the four thermic siphons 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 The boiler pressure was set at 280 160 psi 1 93 160 MPa and each was fitted with four thermic siphons from beneath the firebox to pre heat water entering the boiler used to great effect on Bulleid s Merchant Navy West Country and Battle of Britain classes The Leader had a dry lining firebox it was not surrounded on top and sides by a jacket of water as in normal practice It was constructed of welded steel and used firebricks instead of water for insulation which was a novel but troublesome solution to dry lining the firebox These had the effect of reducing the grate area from 47 160 square feet 4 4 160 m2 to 25 5 160 square feet 2 37 160 m2 and concentrated the fire in a small area 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 The firebox was not initially equipped with a firebrick arch although one was retro fitted during the summer of 1950 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 The smokebox 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 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 The fierce blast from the exhaust also meant that ash and embers were ejected into the atmosphere creating a potential lineside fire hazard For ease of maintenance the boiler firebox smokebox and tender were encased in steel sheeting that resembled a modern diesel locomotive a major departure from traditional steam locomotive design allowing the engine to be cleaned using a carriage washing plant The tender was designed to carry 4 tons 4 06 tonnes of coal and 4 000 160 imperial 160 gallons 18 000 160 l 4 800 160 US gal of water and was covered by a tarpaulin to prevent water ingress into the fireman s cab 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 Construction Construction of the first five Leader locomotives began at the Southern Railway s Brighton railway works in July 1947 British Railways inherited the Leader project upon nationalisation in 1948 which was far enough advanced to continue constructing the prototype as Bulleid was still Chief Mechanical Engineer of the newly formed Southern Region of British Railways Although work on the other four locomotives stalled the prototype Leader emerged from Brighton as locomotive No 36001 in June 1949 The other four members of the initial order made by the Southern Railway Nos 360025 were at varying stages of construction by the end of the development period No 36002 was almost complete No 36003 was without its outer casing and Nos 360045 were little more than sets of frames although most of their major components had been constructed at Eastleigh and Brighton and were stored ready for fitting With no prospect of further money being allocated by the Railway Executive for their completion the unfinished locomotives were put into store at various depots around the former Southern Railway network pending a decision on their future Operational details No 36001 was immediately put into service trials using empty passenger carriage stock 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 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 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 and the Railway Executive felt that the Leader was too revolutionary and were keen to maintain the status quo Performance of No 36001 The Leader being lifted onto its power bogies at Brighton May 1949 The casing allowed the locomotive to be put through a carriage washing plant Following trials that lasted over a year No 36001 was shown to have several flaws including heavy coal and water consumption mechanical unreliability untenable working conditions for both fireman and driver loss of steam through the cylinder rings and uneven weight distribution on the bogies After renewing the cylinder assembly 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 Leader was tested against the
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