SR N1 Class

Infobox Locomotive
powertype=Steam
name = SR N1 class [Haresnape, "N1 class"]
designer = Richard Maunsell
builder = SECR/SR Ashford Works
builddate = 1922 (1), 1934 (5)
totalproduction = 6
whytetype = 2-6-0
gauge = RailGauge|ussg
leadingsize = 3 ft 1 in (0.94 m)
driversize = 5 ft 6 in (1.89 m)
length = 57 ft 10 in (17.4 m)
weight = 106 tons 13cwt (108.3 tonnes)
fueltype = Coal
fuelc

waterc

cylindercount = Three
cylindersize = 16 × 26 in (406 × 660 mm)
boilerpressure = 200 lbf/in² (1.38 MPa)
tractiveeffort = 27,695 lbf (123.19 kN)
railroad = South Eastern and Chatham Railway, Southern Railway, British Railways
railroadclass = SECR / SR: N1
BR: 4P5F
retiredate = 1962
disposition=All scrapped

The SR N1 Class were three cylinder 2-6-0 (mogul) steam locomotives designed by Richard Maunsell for "mixed traffic" duties on the South Eastern and Chatham Railway (SECR) and Southern Railway.Scott-Morgan, p. 18] They were a development of Maunsell's N class design with the first constructed at Ashford works for the SECR in 1922. Five more were constructed for the Southern Railway in 1930. The locomotives did not live up to the expectations made of them, showing little improvement over the N class.

The N1 class' smaller cylinders meant that they had a greater route availability than the N class, enabling them to be used on heavily restricted routes such as the Tonbridge–Hastings line. This resulted the batch of five locomotives, bringing total class strength to six. All saw service with British Railways, though were withdrawn in 1962. None were preserved.

Background

After the construction of his N class locomotives, Richard Maunsell proceeded to design a more powerful version with three cylinders. They were to utilise standard parts in common with the N class, though the new design was designated the N1 class. They were intended for mixed traffic duties on the SECR lines between London and Ramsgate, though only one was completed before the Grouping of railway companies in 1923.Scott-Morgan, p. 18]

Construction history and modifications

The class was introduced on the SECR in 1922, and was initially designed to use Gresley conjugated valve gear. The design was a development of Maunsell's N class locomotives that were already in service. Twelve N class locomotives were built at Ashford works, whilst a thirteenth, number A822, was completed in 1923 with a number of design modifications, and was classified "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, which had been used with mixed results on the Great Northern Railway."Railway Engineer" (44, 1923), pp. 140-143] This arrangement was later replaced with three sets of Walschaerts valve gear for the cylinders, due to the problems that the Gresley-type valve gear displayed when in service on his A1 class Pacifics. The inclusion of the third cylinder necessitated a slab–fronted section above the buffer beam to house the inside cylinder, and slightly smaller outside cylinders gave a different front–end profile to the otherwise similar N class.Holcroft, "Engineer" (181, 1946), pp. 68–70]

The original N1 design included an inside cylinder arrangement designed by Harry Holcroft, Maunsell's assistant, derived from Great Western Railway practice. Holcroft, ("Engineer": 181, 1946), pp. 145–147] This was because Holcroft had been transferred from the GWR and was heavily involved in the design of the N class. However, only one was built to this specification by the time the other five class members had been introduced in 1930.

The locomotives had good route availability, and saw much use on the restricted Tonbridge to Hastings line, for which the future "Schools" class V would be built. For this reason, the remaining five class members were constructed at Ashford using three sets of Walschaerts valve gear on all three cylinders and 4,000 gallon tenders. To promote standardization, A822 was also modified to this specification in 1930. 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 Maunsell's successor Oliver Bulleid. Bulleid also modified the class further by fitting U1 chimneys to the five engines constructed in 1930, improving the draughting of the locomotives.

Operational details

The first, number A822 was sent for comparison trials at Bricklayers' Arms shed against the two cylinder N class."Railway Engineer" (44, 1923), p. 143] The N1 offered no real improvement in performance, which led to the newly formed Southern Railway's decision not to build other class members. 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 Tonbridge to Hastings route.Banks, p. 66]

The N1 Class were good riding locomotives for the crews, a characteristic that made them useful for working summer Saturday passenger relief trains (extra trains incorporated into the Summer timetable to deal with the influx of holidaymakers) to the Kent coast in the days before electrification.Casserley, "Railway World" (27, 1966), pp. 436–437] Following electrification the class moved to Tonbridge shed where they operated on the Redhill and Brighton line. They were frequent visitors to other parts of the Central Section on the Southern Railway.Scott-Morgan, p. 18]

All six locomotives entered service with British Railways after nationalisation in 1948.Casserley, "Railway World" (27, 1966), pp. 436–440] However the British Railways Modernisation Plan detailing the future of Britain's railways, meant that all non-standard classes were to be withdrawn from service. This meant that the N1 class, having only six class members, were all withdrawn in November 1962. None have survived into preservation.

Livery and numbering

SECR and Southern

When grouping occurred in 1923, the liveries sported by the constituent companies were standardised. The N1 Class doyen, A822, was initially released in SECR Maunsell Green, which was carried until 1923 when this was changed to Maunsell's Olive Green livery with yellow numbering and "Southern" on the tender.Swift, p. 50] 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.Scott-Morgan, p. 18] 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.

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.Scott-Morgan, p. 18] This was succeeded by the British Railways Mixed Traffic lined Black livery with red and white lining, and the British Railways crest on the tender. Longworth, "Southern Region"] Numbering was under the British Railways standard system, and were allocated the series 31822 for the first class member built in 1922, and 31876–31880 for the final five.Ian Allan ABC 1958–59]

Footnotes

References

*Casserley, H.C. 'End of the Maunsell moguls—the Southern maids-of-all-work' ("Railway World": 27, 1966), pp. 436–440
*Haresnape, Brian: Maunsell Locomotives – a pictorial history (Ian Allan Ltd, 1977), ISBN 0711007438
*Holcroft, H.: 'Conjugated valve gears for locomotives : their history and development' ("Engineer": 181, 1946), pp. 68–70; 192–193
*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
*'New three-cylinder 2-6-0 type locomotives for the Southern Railway (South Eastern & Chatham Section)' ("Railway Engineer": 44, 1923), pp. 140–143
*Scott-Morgan, John: Maunsell Locomotives (Ian Allan Publishing: Hinckley, 2002), ISBN 0711028729
*Swift, Peter: Maunsell 4-6-0 King Arthur Class (Ian Allan Publishing: Hinckley, 2006) (Locomotives in Detail series volume 4) (Hinckley: Ian Allan Publishing, 2006), ISBN 0711030863

Further reading

*Ian Allan ABC of British Railways Locomotives, winter 1962–3 edition