The Merchant Navy pacifics: innovation ahead of their time
article by: Ian Crowder

35005 Canadian Pacific at the Mid Hants Railway

Merchant Navy 21C4 (later 35004) Cunard White Star at Waterloo with a special boat train for the maiden ordinary passenger carrying voyage of the liner "Queen Elizabeth", 16 October 1946.
Updated April 2010
The visit of SR Merchant Navy class pacific no. 35005 Canadian
Pacific for the September 2005 steam gala weekend offered a
tantalising glimpse of what is to be on the Honeybourne Line when
sister locomotive, no. 35006 Peninsular & Oriental SN Co enters
service after its long and thorough overhaul at Toddington. As of
April 2010, No. 35006 is looking increasingly complete as the weeks
progress, following return of the fully steam-tested boiler
from Chatham to Toddington and re-assembly of the locomotive
progressing well. It should be back in service in
2011.
35005 Canadian Pacific is owned by the Mid Hants 'Watercress'
Line (where it is pictured, courtesy of Tony Wood the Mid Hants'
webmaster). We're grateful to Colin Chambers at Alresford station
for helping us with the arrangements for the engine to pay this
visit.
This was the first visit by a working member of the class to the
GWR. It made a star appearance just for the GWR's Gala over the
weekend of 10th and 11th September 2005, but returned for a more
extended visit the following year. Indeed, the old Stratford to
Cheltenham route was well out of bounds for these class 8
locomotives - it is believed (unless someone can comment otherwise)
that no. 35028 'Clan Line' is the only Merchant Navy to have run
over the route, when heading south in a locomotive movement shortly
before the line was closed.
'Space age' technology for the Southern
It's hard to imagine how people might have reacted when
they saw the first member of the class emerge from Eastleigh works
in 1941. 'Sensation' is probably an understatement - the
locomotives were anything but conventional in appearance and
engineering innovation. The Southern Railway's Chief Mechanical
Engineer, O V S Bulleid, came from London & North Eastern
Railway and although influenced by LNER practice, was probably far
ahead of his time.
Three batches of 10 were completed, the last being delivered by
British Railways following nationalisation.
The 30 Merchant Navy's were a three-cylinder design with a
boiler featuring a wide firebox - but that's about as far as LNER
comparisons go. Behind the unconventional 'air-smoothed' casing
(possibly influenced by Gresley's semi -streamlined P2 class
2-8-2's) and American 'Boxpok' style wheels were a host of
ideas never tried before. Not least of these was chain driven valve
gear between the frames, the valve gear and middle motion totally
enclosed in an oil bath, intended to eliminate the need for staff
to get between the frames to 'oil up'. A steam reverser operated
the valve gear and the whole assembly completely eliminated the
hammer-blow associated with conventional locomotives. Another major
innovation included an all-steel boiler equipped with thermic
siphons within the firebox to promote better water circulation, and
working at an unprecedented 280lb/sq.in. Rocking grate and hopper
ashpan made for quick and clean disposal while the cab layout was
ergonomically designed to simplify operation, this including
steam-operated firehole doors worked by a treadle. An electric
generator powered lighting for cab, gauges, inspection lights and
head and tail train code lights.
The decision was taken to name the class after shipping
companies serving Southampton Docks - an inspired choice that
highlighted the SR's connections with the continent and
international travel - even if it meant some extremely long names
(such at 35006: Peninsular & Oriental Steam Navigation Co to
give it its full name!).
Change for the better?
Although the Merchant Navy class (and the similar but smaller
West country and Battle of Britain classes) proved fast, free
running and powerful they were beset with a host of irksome
maintenance problems. For example, the oil bath proved impossible
to keep oil tight; the chains were prone to stretching and the
steam reverser approximate. The air -smoothed casing, while easy to
keep clean (the engines were designed to go through carriage
washers) proved a nightmare for access when things went wrong. They
spent much more time in the works than they should. However, the
boiler was a triumph - it was free steaming and, if a little heavy
on coal, would deliver whatever the driver demanded of it -
provided the fireman could keep up! The class routinely ran at
speeds well in excess of 80mph, 100mph not being uncommon.
In 1955, the British Railways Board gave authority for the first
15 members of the class to be rebuilt to more conventional design
and the first, no. 35018, emerged later that year. The influence of
Riddles (designer of the British Railways standard designs,
including the 9F class 2-10-0) was clear and an obvious comparison
was made with the BR 'Britannia' pacifics.
Gone was the air-smoothed casing and chain driven valve gear,
replaced with three separate sets of Walschearts gear. Gone too,
was the troublesome steam reverser. A new smokebox was fitted (but
retaining the distinctive oval Bullied smokebox door); and an
additional smokebox saddle fitted to strengthen the frames. A new
superheater feeder and outside steam pipes were provided along with
new pistons, piston rods and cylinder drain cocks. New mechanical
lubricators were fitted, along with a new regulator and ashpan
design. Finally, weights had to be fitted to the wheels to
counteract the hammer-blow produced by the motion.
Success of the rebuild was such that all members of the class
were rebuilt by 1959 and similar work immediately started on the
110 light pacifics. Although the rebuilt locomotives were expected
to remain in service until 1987, the modernisation plan put paid to
that - and like Riddles' Standard classes, had lamentably short
lives. Nevertheless, the Merchant Navy's put in commendable and
reliable performance with little, if any, loss in performance.
Indeed, there are several authenticated examples of the rebuilt
locomotive exceeding the magic 'ton' - no. 35003 'Royal Mail'
topping 106mph with a Weymouth-Waterloo service between Basingstoke
and Woking, just two weeks before the end of SR steam.
The SR was the last main line in the UK to operate express
services with steam: the Waterloo - Southampton - Bournemouth -
Weymouth expresses remaining almost exclusively Bulleid-pacific
hauled right to the end. Appropriately, it fell to the last member
of the class, 35030 'Elder-Dempster Lines' to haul the very last
steam-hauled train to Waterloo: the 14.11 Weymouth-Waterloo on 9
July 1967. The next day, modern traction took over and there was
not a breath of steam left to be seen. A sad day indeed and
seemingly, the last rites of a remarkable class of locomotive had
been performed.
Fortunately, 11 members of the class (just over a third of the
total!) survived the cutter's torch and 35028 and 35005 have, for
example, over recent years put in sterling performances on tour
duty. Other members of the class are close to completion after long
and expensive restorations ,so we may enjoy seeing these fine
locomotives in action for many years to come - and not least of
them our own resident 35006.
Click here for progress reports and information on 35006