SR N1 Class
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The SR N1 Class were three cylinder 2-6-0 (mogul) steam locomotives designed by Richard Maunsell for mixed-traffic duties on the Southern Railway. None have survived into the preservation era.
| Power type | Steam |
|---|---|
| Designer | Richard Maunsell |
| Builder | SECR/SR Ashford Works |
| Build date | 1922 (1), 1934 (5) |
| Total production | 6 |
| Configuration | 2-6-0 |
| Gauge | 4 ft 8½ in (1,435 mm) |
| Leading wheel size | 3 ft 1 in (0.94 m) |
| Driver size | 5 ft 6 in (1.89 m) |
| Length | 57 ft 10 in (17.4 m) |
| Locomotive weight | 106 tons 13cwt (108.3 tonnes) |
| Fuel type | Coal |
| Fuel capacity | 5 tons (5.1 tonnes) |
| Water capacity | (A822) 3,500 imp. gal (15,890 litres) (A876-A880) 4000 imp. gal (18,160 litres) |
| Boiler pressure | 200 lbf/in² (1.38 MPa) |
| Cylinders | Three |
| Cylinder size | 16 × 26 in (406 × 660 mm) |
| Tractive effort | 27,695 lbf (123.19 kN) |
| Career | South Eastern and Chatham Railway, Southern Railway, British Railways |
| Class | SECR / SR: N1 BR: 4P5F |
| Retired | 1962 |
| Disposition | All scrapped |
Contents |
[edit] Background
Upon the construction of his N class locomotives, Richard Maunsell undertook the design of a more powerful version with three cylinders, and these locomotives were to become the N1 Class. They were intended for mixed-traffic duties, though only six were completed.
[edit] Construction history
The class was introduced in 1922, and was initially designed to use Gresley conjugated valve gear. The design spawned from Maunsell's N class locomotives that were already in service. Twelve had been built at Ashford, and the thirteenth, number A822, was outshopped in 1923 with a number of modifications, hence the classification 'N1'.
These modifications mainly concerned the cylinder arrangement: the two cylinders of the N class were replaced with three. The three cylinders were initially designed to be powered by sets of Gresley conjugated valve gear. This arrangement was later replaced with three sets of Walschaerts valve gear due to the problems that the Gresley-type valve gear displayed when in service on his A1 Pacifics.
There were two outside cylinders with Walschaerts valve gear and an inside cylinder with Holcroft valve gear, Harry Holcroft having been transferred from the Great Western Railway and heavily involved in the design of the N Class. This therefore resulted in the new design's basic appearance being similar, though a front profile showed a slab-fronted section above the buffer beam to house the inside cylinder, and slightly smaller outside cylinders. However, only one was built to this specification by 1930.
The locomotives had good route availability, and were of great use on the restricted Tonbridge to Hastings line, for which the future Schools Class V would be built. Because of this, Maunsell decided to build five more in 1930, but this time using Walschaerts valve gear on all three cylinders and to promote standardization, modifed A822. Smoke deflectors were subsequently fitted to improve visibility from the footplate, a refinement that had also been undertaken on the N class locomotives.
Maunsell had applied snifting valves to the class but these were removed by Oliver Bulleid. Bulleid also modified the class further by fitting U1 chimneys to the five engines constructed in 1930.
[edit] Livery and numbering
[edit] SECR and Southern
When grouping occurred in 1923, the liveries sported by the constituent companies were standardised. The N1 Class doyen, A822, was initially outshopped in Urie LSWR Green, and ran in this guise throughout the 1920s, with yellow numbering and 'Southern' on the tender. From 1930, when the class expanded, all were outshopped in Maunsell lined SR Olive Green after 1931, once again with yellow markings. During the Second World War, the class was outshopped in wartime black livery with Oliver Bulleid's "Sunshine Yellow" lettering.
The class was initially numbered in the Southern's post-grouping parlance from A822 (the class doyen of 1922) to the second batch of five, which were allocated the numbers A876–A880. This was subsequently changed to 1822, and 1876–1880 respectively during the 1930s.
[edit] Post-1948 (nationalisation)
The class was absorbed by British Railways in 1948, and like their N Class cousins, were allocated the BR Power classification 4P5F. Livery was initially the same as that of the Southern Railway, though with 'British Railways' on the tender, and an 'S' prefix to the Southern number. This was succeeded by the BR Mixed Traffic lined Black livery with red and white lining, and the BR crest on the tender. [2] Numbering was under the BR standard system, and were allocated the series 31822 for the first class member built in 1923, and 31876–31880 for the final five.[3]
[edit] Operational details
The first, number A822 was sent for trials at Bricklayers Arms shed where the new locomotive's performance could be compared with the two cylinder N class. It was soon found to have no real improvement in performance, which meant that no other class members were built until 1930. However, the main benefit the N1 had over the N Class was the fact that the smaller outside cylinders increased its route availability. This meant that the class could operate over the severely restricted Tonbride to Hastings route.
The N1 Class were good riding locomotives, a characteristic that made them useful for working summer Saturday passenger relief trains to the Kent coast in the days before electrification. Following electrification the class moved to Tonbridge shed where they operated to Redhill and Brighton line. They were frequent visitors to other parts of the Central Section.
With the onset of the BR Modernisation Plan, the class, being of non-standard type due to having only six class members, were all withdrawn in November 1962.[2] None have survived into preservation.
[edit] References
- ^ Haresnape, Brian: Maunsell Locomotives - a pictorial history (Ian Allan Ltd, 1977), ISBN 0711007438
- ^ a b Longworth, Hugh: British Railway Steam Locomotives: 1948–1968 (Oxford Publishing Company: Oxford, 2005) ISBN 0860935930
- ^ Ian Allan ABC of British Railways Locomotives, winter 1958–59 edition
[edit] Further Reading
- Ian Allan ABC of British Railways Locomotives, winter 1962–3 edition
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