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  • Andy Vincent

Southern Railway 'Moguls' swap boilers

Photo: Nick Lloyd

Since the end of the 2020 operating season, a small but dedicated team of staff from our Locomotive Carriage and Wagon department have been working within government guidelines to progress the overhaul of Southern Railway U Class Mogul 31806.

The locomotive was steadily disassembled during January and made ready to receive the freshly overhauled boiler that was originally intended to go in Southern Railway N Class 31874, the decision to swap boilers having been taken to enable 31806 to return to service during 2021.

Once ready, the locomotive was towed slowly to Norden and at the end of January the old boiler was lifted from the frames. The opportunity was then taken to carry out inspections and minor repairs to the frames in areas that are inaccessible with a boiler in place.

31874’s boiler was lowered into the frames of 31806 in early February once all these works had been completed and the “U Boat” has now been returned to Swanage where staff are now working reassemble the locomotive.

Once all pipe work has been reinstalled the boiler will be subject to hydraulic and steam testing before final reassembly of the locomotive is completed to enable 31806 to return to service.

The boiler originally fitted to 31806 will now be inspected and a schedule of works drawn up to show what is needed to overhaul it for use in N Class 31874.

The N class locomotives were designed in 1914 for the South East and Chatham Railway (SECR) by Richard Maunsell. Eighty locomotives were built between 1917 and 1934 with one - 31874 - surviving long enough to be preserved. The original design was heavily influenced by the 4300 class designed for the Great Western Railway by George Churchward.

The U class locomotives were a further evolution of the 4300 and N classes and designed by Richard Maunell after his appointment to the Southern Railway following grouping of the railway companies. Fifty locomotives were built between 1928 and 1931 with four (including one rebuilt version - 31806) being preserved.

The Swanage Railway always welcomes new volunteers so, for a chat, contact Swanage Railway volunteer co-ordinator Mike Whitwam on 01929 475212 or email him at


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