Maunsell U1 class 2-6-0

The U1 class is the three cylinder derivative of the U class. The first member of the class results from the rebuilding at Ashford in 1928 of the sole three cylindered K1 "River" class 2-6-4T locomotive NºA890 River Frome. This rebuilding to 2-6-0 with tender format was carried out as part of the programme to rebuild the other two cylinder K class "River" tanks to the U class. Its original number was retained (but the name dropped), ot was matched with a 3500 gallon flat-sided tender and re-designated U1 class. The locomotive originally retained its Holcroft conjugated valve gear on its middle cylinder but this continued to be troublesome and was later converted to Walschaerts to conform with the remainder of the class.
U1 class An unidentified U1 photographed at Hooley during 1935.

photograph: Mike Morant collection

The conversion proved to be a success, particularly in regard to acceleration and smooth running, so a further twenty were built from scratch drawing on, as with other Maunsell classes, a range of standard parts. This batch was built at Eastleigh in 1931 and numbered A891-A900 (renumbered to 31891-31900 under British Railways) and 1901-1910 (31901-31910). They were fitted with three sets of Walschaerts valve gear from new and had 4000 gallon tenders with turned-in tops. The three cylinders were of 16in diameter 28in stroke compared to the 19in diameter cylinders on the U class. The resulting reduction in overall width of the engine gave the U1 class a wider route availability that the U class and they were cleared to run on the Hastings line. The driving wheels were 6 ft in diameter as befits a passenger engine. Tractive effort at 85 percent boiler pressure was 25,387 lb. The K1 conversion was identifiable (as with K class conversions) by the side cab cutaway extending into the roof and the front steps being behind the cylinders, although these were later removed and new footsteps fitted in front of the cylinders. The running plate was straight on the new-builds, stepped up at the front on the rebuilds, the new-builds always had their front footsteps ahead of the cylinders and their steam dome had a flatter top. As with the U class the rebuild had larger splashers above the driving wheels.
Nº31906 running through a pristine Norbury station with a fast service in the mid-1950s.

photograph by Mike Morant

31893 Nº31893 with a down Ramsgate train at Newington on 13th June 1959.

photograph: Mike Morant collection

The U1 class proved to be swift free runners capable of hauling heavy loads. The official speed limit of the class was 70mph and since they were mostly used on semi-fast passenger services they did not get much opportunity to push the limit, though it is recorded that given the chance much faster runs were made. A891-900 were allocated to Fratton from new for working the main Portsmouth line services where they coped well. When displaced by the arrival of the more powerful Schools (V) class they moved to the Eastern section to join the rest of the class. During the war they served well on the Hastings line troop trains, although the continually curving nature of the line led to excessive flange wear. For this reason the class was not a success west of Exeter where they were tried for a short while. The U1 class therefore became a principally Eastern and Central section locomotive. Despite intended to be a passenger engine they also worked freight turns thus somewhat blurring the line between them and the mixed traffic N/N1 classes. In later days a member of the class was tried on the Somerset and Dorset but it did not cope as well as larger types.

Minor modifications happened throughout their lives. As with other Maunsell Moguls smoke deflectors were added in the mid 1930s and due to the high running plate they were of reduced height. Also as with the other Moguls their smokebox snifting valves were removed. Some of the class received new cylinders in 1954, and although unlike other Maunsell classes major front end alterations were not made some did have BR standard blastpipes fitted. The entire class of 21 was withdrawn between 1962 and 1963 and unfortunately none is preserved.

Nº31905 pictured at Nine Elms shed on the 25th October 1961

photograph by Alan Robinson

31908 The high running plate and short depth smoke deflectors can be seen clearly in both this front end view of Nº31908 at Nine Elms on 25th October 1961 and the photograph of Nº31906 above.

photograph by Alan Robinson

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