BR Modifications and Rebuilding
For their near two-decade existence under BR auspices, alterations to the Bulleid Pacifics were severe. Change began in 1952, when the distinct high flanges of the tenders started to be cut down on both MN and WC/BoB engines, to enable the pipe of a water column to be swung over freely, without obstacle. Despite this, the tenders retained their distinct curved profile, which sat in harmony with behind carriage stock. Two years later, boiler pressure of both MN engines and ‘’Lightweights’’ was de-rated from 280 PSI to 250 PSI – hitherto, the Bulleid Pacifics, matched only by the GWR’s ‘’County’’ engines, had the highest boiler pressure rating of any steam locomotive class in the country. Pressure reduction made the engines cheaper to maintain, permitting a more common grade of steel to be used in the firebox. The boilers of these engines were well designed, and from the outset Bulleid had incorporated thermic siphons in the firebox. These were essentially steel tubes through which water was pumped, providing locomotives with a greater overall heating surface area. The general idea behind thermic siphons was that of conserving fuel, whilst still raising steam production – of course, the Bulleid Pacifics were by no means light on coal consumption!
Bulleid’s innovative features – particularly the chain-driven valve gear and oil bath – were high maintenance items which made his Pacifics expensive engines to operate, in addition to giving them, at times, poor availability. Consequently, in 1954, the Chief Technical Assistant of the Locomotive Department, Brighton, was given the task of devising a scheme which would remedy these faults. The individual was Ronald G. Jarvis, formerly a Derby man and no stranger to the products of Bulleid. When the latter departed for Ireland in 1949, Jarvis was put in charge of the ‘’Leader’’ project, the scheme aimed at producing a modern steam engine which, externally, was on a par with those double-ended diesel locomotives later produced by BR. Five prototypes were made, but only one of these was fully completed to working order, and the whole ‘’Leader’’ scheme was quietly discontinued in 1951.
Jarvis’ plans outlined an extensive rebuild of every Merchant Navy and Light Pacific, doing away with the Bulleid chain-driven valve gear, steam reverser, and the air-smoothed casing. The steam reverser was linked to the valve gear and regulated the timing of the valves, thus controlling the admission of steam into the cylinders. It was capable of sending steam in above or below the pistons, which determined whether the locomotive moved backwards or forwards. No. 34005 ‘’Barnstaple’’ became the first Light Pacific to enter Eastleigh works for rebuilding, in 1957. The rebuilding scheme had much emphasis on bringing the appearance of Bulleid engines in line with those BR Standard Pacifics which were then beginning to emerge. Conventional boiler cladding was fitted, which in turn provided room for stepboards above the wheels, and BR-style smoke deflectors were installed. The chain-driven valve gear and oil bath gave way to a more conventional Walschaerts’ system, the inside cylinder was replaced with a new design, and the steam reverser was abolished in favour of a screw reverser. There was, however, discontent from across the Irish Sea, for it was later reported that Bulleid would rather have seen his engines scrapped, than rebuilt. On the plus side, the scheme would give his Pacifics another twenty-five years of service life with BR, on a par with the relatively newer BR Standard classes. At the time, it was predicted that steam traction would last up until the 1990s, and construction of BR steam designs continued unabated.
The efforts to rebuild the Bulleid Pacifics were to be stifled. In December 1954, the British Transport Commission published a ‘’Modernisation Plan’’, outlining the complete eradication of steam traction throughout BR in a much smaller timeframe than originally anticipated, by means of a series of dieselisation and electrification schemes. To set the ball rolling on SR metals was the ‘’Kent Coast Electrification Scheme’’, approved in February 1956 and resulting in the complete abolition of steam traction on the South Eastern Division. Preparatory work along the ‘’Chatham’’ main line began in the following year, concurrent with the start of the Light Pacific rebuilding scheme. Large numbers of Bulleid’s Pacifics were allocated to the South Eastern Divison at this time, notably at Stewarts Lane, Bricklayers Arms, Ramsgate, and Dover. At the start of 1959, shortly before the completion of ‘’Phase I’’ of the electrification scheme, thirty-six Light Pacifics were allocated to former Eastern Section sheds, in addition to a trio of MN Class engines – No. 35001 ‘’Channel Packet’’, No. 35015 ''Rotterdam Lloyd'', and No. 35028 ‘’Clan Line’’. The full accelerated electric timetable commenced on the aforementioned ‘’Chatham’’ route on 15th June 1959, but steam still remained in evidence on the ex-SER main line via Orpington, Tonbridge, and Ashford until this too witnessed a full electric schedule from 18th June 1962. Rebuilding of Bulleid Pacifics had since ceased in May of the previous year, with No. 34101 ‘’Hartland’’ emerging from Eastleigh works as the sixtieth – and final – modified engine. All thirty MN engines had been similarly treated, but sadly, steam was in terminal decline.
Whilst rebuilding had brought obvious maintenance cost savings, it also yielded some adverse side effects. Balance weights had been added to the wheels, which gave rise to the ‘’hammer blow’’ effect on the track. Furthermore, rebuilt Light Pacifics were over four tons heavier than their unrebuilt counterparts, which barred them from those SR lines west of Exeter. This restriction was later lifted, permitting them to operate between Exeter and Plymouth via Okehampton, but clearance was never given for the route north of Coleford Junction, to Barnstaple, Ilfracombe, and Padstow. Sadly, these lines themselves were on the brink of severe decline, as a result of regional border changes. In September 1962, those ex-LSWR lines west of Salisbury came under Western Region control, the latter allegedly receiving this territory, and that of the Somerset & Dorset line, to compensate for the loss of its Wolverhampton/Birkenhead route to the Midland Region. As a result, thirty-seven Exmouth Junction-allocated Bulleid Light Pacifics became under the jurisdiction of the WR, and no time was wasted in degrading the route in favour of the Paddington line via Castle Cary. Through steam-hauled services from Waterloo to Exeter and Plymouth ceased on 4th September 1964, and Bulleid Pacifics were replaced on these services by WR Diesel Hydraulics – steam completely vanished from the Exeter area in the following year.
The Waterloo to Bournemouth/Weymouth route remained as the last stronghold of steam power on the entire SR network. Electrification of the Kent Coast lines and dieselisation of Waterloo to Exeter (and beyond) services had ensured no shortage of steam locomotives for this core line. With the Bournemouth electrification programme formally receiving the green light in September 1964, mass locomotive withdrawals began in earnest. The first Light Pacifics to succumb were Nos. 34035, 34043, 34055, and 34074, all unrebuilt engines, which had already been withdrawn in April 1963, as a result of the WR takeover of the lines west of Salisbury. No. 34028 ‘’Eddystone’’ was taken out of service in May of the following year, becoming the first rebuilt engine to be withdrawn. Overhauls ceased, maintenance became minimal, and any spare parts required to keep remaining locomotives serviceable were salvaged from withdrawn engines. The last Pacific to be overhauled was rebuilt No. 34089 ‘’602 Squadron’’, which emerged from Eastleigh Works on 3rd October 1966, less than a year before the end of steam at Waterloo. Steam-hauled services between Waterloo and Salisbury, and Waterloo and Southampton/Bournemouth/Weymouth, ceased on Sunday 9th July 1967. Light Pacific ‘’Dartmoor’’ was reportedly the last engine to run under its own power between Waterloo and Nine Elms, after bringing in a boat train from Southampton Docks.
Postscript: Cab Widths
This topic is a science in itself, with a number of variations over the engines’ existence. From the outset, front vision from cabs was reportedly poor and early on in both MN Class and Light Pacific production, it was found that smoke had a tendency to drift down the side of the engines, obscuring the view of the driver. This sparked the need to install longer smoke deflectors on new builds still emerging from Eastleigh and Brighton Works. Early production Light Pacific examples were fitted with ‘’narrow cabs’’, which ensured engines could fit within tight loading gauges – particularly that of the Hastings via Tunbridge Wells Central route. However, from April 1948 onwards, starting with No. 34071, new engines emerging from the works were fitted with wider cabs, to improve visibility. As a result, locomotive widths increased from 8-foot 8-inches to 9-foot 3-inches.