Masterclass
Looking at railways in detail
Nick Brodrick recounts the history of Robert Riddles’ versatile Standard ‘2MT’ 2 ‐ 6‐0.
I fit ain’t broke, don’t fix it…Take the British Railways Standard ‘2MT’ 2 ‐ 6‐0 at face value and you’d be forgiven for imagining that the likeness with its LMS forebear design meant that it was a straight lift from H.G. Ivatt’s 1946 blueprints.
Rather, the chief mechanical engineer’s gauge-friendly locomotive had been a disappointment for a modern, post ‐war design. Performance trials with No. 46413 in the early days of British Railways showed performances were only equal to a GWR ‘Dean Goods’ 0 ‐ 6‐0 – not much of an achievement for a design half a century newer and with mod-cons, like superheaters.
Tweaks made at Swindon to the blastpipe, and fitting a taller, narrower chimney did the trick. Suddenly, No. 46413 was able to take a 15-coach (455 ton) test train to more than 60mph – far exceeding its original design envelope. The LMS ‘Mogul’ design was subsequently enhanced further with slightly increased diameter cylinder bores when a new batch was authorised for construction in 1951.
IDENTICAL, BUT…
It was this ‘Version 2’ of Ivatt’s design that ultimately formed the basis of ‘Version 3’ – the Standard ‘2MT’, built at Darlington Works between 1951 and 1956 as part of the newly nationalised railway’s
‘Standard’ family. These new locomotives were very closely related to their ‘Big Four’ predecessors. Identical features included 5ft diameter driving wheels; 16½ in by 24in cylinders; 17.5sq/ft grate area; 200lbs sq/in boiler pressure; and 18,515lbs tractive effort (at 85% boiler pressure). Of little consequence to their route availability was the fact that the Darlington stud of engines were 2ton 3cwt heavier than their forebears. Walschaerts valve gear and Belpaire fireboxes provided commonality to both the LMS design and other Standards.
There were also, inevitably, minor detail differences that distinguished the ‘78XXXs’, such as a continental-style running plate ‘apron’ at the front end and angled top half of the cab sides that allowed even better route availability. The LMS design top-feed into the boiler was naturally replaced by the Riddles clack valves on the shoulders of the boiler barrel; and the regulator reach rod hung on the left ‐hand side of the boiler, rather than through it.
The overall design was user-friendly, especially for the fireman and disposal gangs, who were thankful for the
