SR U1 class
SR U1 class British Railways | |
---|---|
Class | SR: U1 |
Power class |
|
Nicknames | "Montys" |
Locale | Southern Region |
Withdrawn | 1962–1963 |
Disposition | All scrapped |
The SR U1 class were three-cylinder
The U1 prototype was a rebuild of the unique 3-cylinder
The class was to supersede the production of N1 class locomotives because of its good performance, which amounted to an order for 20 more U1 locomotives in 1931. Production was halted at 21 locomotives, the class gaining a good reputation amongst crews, and all were transferred to
Background
Work on the new design of locomotive was undertaken in 1928 following the construction of the first of Maunsell's U class locomotives. Maunsell wished to create a more powerful version with greater route availability than its predecessors. The Southern Railway had inherited routes with restricted loading gauge where the large, overhanging cylinders of a 2-cylinder locomotive could foul the walls of bridges and tunnels.[4] The new locomotive was intended to complement the U class by providing another locomotive capable of undertaking passenger duties on the Eastern section of the Southern Railway network between London and Ramsgate.[5] The new locomotive, like the U and N classes before it, was intended to replace obsolete 0-6-0 classes in an attempt to standardise and ease maintenance by sharing parts with other Maunsell designs.[6] Several K class 2-cylinder 2-6-4 locomotives had been successfully rebuilt as U class moguls, leaving the solitary 3-cylinder K1 class 2-6-4 number A890 River Frome for similar treatment.
Maunsell enlisted the help of the former GWR engineer Harold Holcroft, who had been recruited by the SECR as one of Maunsell's assistants. At Holcroft's suggestion, the rebuilt locomotive was to feature a 2-6-0 wheel arrangement, enabling it to operate over the lightly laid track-work on the Eastern section of the Southern Railway, whilst allowing an increased size of boiler to those featured on the 0-6-0s.[7] As the rebuild used similar parts to the N and K classes to aid mass production, the new locomotive also had many features previously found on the successful GWR 4300 class, following and improving upon Churchward's design principles for this locomotive type.[6] The redesigned locomotive was re-designated U1, and retained Holcroft's variant of the Gresley conjugated valve gear used on the K1 2-6-4.[8] To facilitate the rebuild, Maunsell used his past experience with the N1 class 3-cylinder locomotives as a template for the new design. The style of the new locomotive also demonstrated the Midland Railway influences of Maunsell's other assistant, the ex-Midland Railway engineer James Clayton.
Construction details
Holcroft valve gear
The valve gear assembly originally designed by Holcroft for use on the N1 class regulated the timing of the valve events that admitted steam into the cylinder, increasing efficiency whilst reducing mechanical wear and the effects of
Holcroft's process of driving the middle cylinder directly from the combination lever contrasted to the approach taken by
Locomotive A890
Work started on the conversion of the solitary 3-cylinder K1 class No. A890 to a 2-6-0 tender locomotive design at Ashford works in early 1928.
The similarity with GWR locomotive practice ended there, as a Midland Railway influence could be found in the placement of the locomotive fittings, with water top-feed into the boiler located inside a dome, although a modification was made to the cab area, which was a variation of those featured on the N class and the 0-6-0s of Henry Fowler.[13] The aesthetic aspects of the locomotive were contributed by another of Maunsell's assistants, James Clayton, who had moved to the SECR from the Midland Railway.[13] The new locomotives also varied with the increased amount of superheating surface area, and the outside valves were controlled by Walschaerts valve gear.[9]
The rebuilding process involved the removal of the side water tanks, the rear coal bunker and the trailing axles. In featuring similar components to the U class, the U1 was similar in profile, although a slab-front was incorporated above the front
Main batch, differences with No. A890 and modifications
No. A890 was the only U1 class member in operation as trials were undertaken to ascertain whether the design should be perpetuated instead of the N1 class for use on the more restricted routes of the Southern Railway.[14] The success of the prototype U1 over the N1 design led to a construction order for a further 20 locomotives to be built at Eastleigh in 1931. Despite the possible weight savings with the Holcroft valve gear, the complexity of maintaining the linkage with the inside cylinder meant that the new class members were fitted with three separate sets of Walschaerts valve gear for all cylinders.[9] As had happened with the N1 class prototype No. A822, No. A890 was modified to this revised specification in 1930 to reduce maintenance costs.[9] Prior to the modification of No. A890, the new locomotives were visibly different by the absence of the outside-to-inside valve linkage assembly and were given larger tenders with a water capacity of 4,000-imperial-gallon (18,184 L; 4,803.8 US gal), although the slab-front was retained.[15]
Further changes were made to the design, as No. A890 featured right-hand drive, impeding forward vision for viewing signals from the footplate. The main batch was produced with left-hand drive to resolve this problem.[14] The main batch could also be distinguished by their higher running plates along the sides of the boiler, compared to the lower version on the rebuild that required larger wheel splashers to cover the tops of the driving wheels.[16] The main batch had also dispensed with the N class/Midland Railway-style double spectacle plates (the small windows on the front face of the cab) that was retained on the prototype, replacing them with one each side of the boiler.[11] The production locomotives also had a flatter top to the dome covers than that seen on the rebuild.[16] The cabside cutaways for driver visibility were also cut into the roof of A890, an arrangement reminiscent of the 2-cylinder U class rebuilds of K class locomotives.[1]
The entire U1 class had
Operational details and preservation
The U1 class was a reliable and economical design like its U class predecessor, being similarly capable of speeds in excess of 70 mph (110 km/h), whilst displaying excellent traction and acceleration characteristics.
All locomotives were inherited by British Railways in 1948, and from 1955, several members of the class received new chimneys of the British Railways
Livery and numbering
Southern
The entire class was painted in Maunsell's lined Southern Railway Olive Green with yellow markings and "Southern" on the tender.
British Railways
The class was absorbed by
References
Notes
- ^ a b c d e Haresnape 1977, "U1 class".
- ^ Scott-Morgan 2002, p. 50.
- ^ a b Casserley 1966, pp. 436–440.
- ^ a b c Banks, pp. 66-67[full citation needed]
- ^ a b c d e f Reynolds 1943, pp. 155–158, 199-202 and 279-282.
- ^ a b Middlemass 1990, pp. 148–154.
- ^ Casserley 1966, p. 436.
- ^ Scott-Morgan 2002, p. 52.
- ^ a b c d e f Clarke 2008a, pp. 38–41.
- ^ a b c Holcroft 1946, pp. 145–147.
- ^ a b c Herring, Section "U Class", pp. 120–121[full citation needed]
- ^ Railway Engineer (44, 1923), pp. 140-143.[full citation needed]
- ^ a b c d Clarke 2008a, p. 40.
- ^ a b c d e Clarke 2008b, p. 56.
- ^ Holcroft 1946, pp. 146.
- ^ a b c d e Clarke 2008b, p. 55.
- ^ "Maunsell U1 class 2-6-0". Southern Railway E-mail Group. Retrieved 1 October 2020.
- ^ "Maunsell U1 class 2-6-0". Southern E-Group. 2004. Retrieved 19 June 2007. For information on BR modifications.
- ^ Swift 2006, p. 50.
- ^ a b Longworth 2005, U class.
- ^ Longworth 2005, Southern Region.
- ^ Ian Allan ABC 1958–59
Bibliography
- Casserley, H.C. (1966). "End of the Maunsell moguls—the Southern maids-of-all-work". Railway World. No. 27. pp. 436–440.
- Clarke, Jeremy (2008). "The locomotives of R.E.L. Maunsell, Part 3: The 'Mogul' family – SECR". Steam World. No. 248. pp. 38–41.
- Clarke, Jeremy (2008). "The locomotives of R.E.L. Maunsell, Part 4: The 'Mogul' family – SR". Steam World. No. 249. pp. 53–56.
- Haresnape, Brian (1977). Maunsell Locomotives – a pictorial history. Ian Allan Ltd. ISBN 0-7110-0743-8.
- Holcroft, H. (1946). "Conjugated valve gears for locomotives: their history and development". Engineer (181): 68–70, 192–193.
- Longworth, Hugh (2005). British Railway Steam Locomotives: 1948–1968. Oxford: Oxford Publishing Company. ISBN 0-86093-593-0.
- Ian Allan 'ABC of British Railways Locomotives (Winter 1958–59 ed.).
- Middlemass, Tom (1990). "The "Woolworths" — Woolwich Arsenal's tentative entry into main line locomotive building". Backtrack (4): 148–54.
- Reynolds, W.J. (1943). "The Maunsell moguls, S.R." (PDF). The Railway Magazine. Vol. 89, no. 545, 546, 547. pp. 155–8, 199–202, 279–82.
- Scott-Morgan, John (2002). Maunsell Locomotives. Hinckley: Ian Allan Publishing. ISBN 0-7110-2872-9.
- Swift, Peter (2006). Maunsell 4-6-0 King Arthur Class. Locomotives in Detail. Vol. 4. Hinckley: Ian Allan Publishing. ISBN 0-7110-3086-3.
Further reading
- Ian Allan ABC of British Railways Locomotives (Winter 1962/3 ed.).
External links
- Class U-1 Details at Rail UK