LSWR M7 class

Infobox Locomotive
powertype=Steam
name = LSWR/SR M7 Herring, Peter: "Classic British Steam Locomotives" (Abbeydale Press: London, 2000) Section "O2/M7 Classes" Pages 60-61 ISBN 1861470576]

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caption = National Railway Museum's M7 as preserved in LSWR livery.
designer = Dugald Drummond
builder = LSWR Nine Elms Works (95)
LSWR Eastleigh Works (10)
builddate = 1897–1911
totalproduction = 105
whytetype = 0-4-4
gauge = RailGauge|ussg
driversize = convert|67|in|m|3|abbr=on
trailingsize = convert|43|in|m|3|abbr=on
length = convert|34|ft|8|in|m|2|abbr=on
weight = convert|60.20|LT|t|1
fueltype = Coal
fuelc
convert|3.25|LT|t|1
waterc
convert|1300|impgal|l|abbr=on|lk=on
cylindercount = Two, inside
cylindersize = 18.5 × 26 in (470 × 660 mm)
boilerpressure = convert|175|psi|MPa|2|abbr=on|lk=on
tractiveeffort = convert|19750|lbf|kN|2|abbr=on|lk=on
railroad=London and South Western Railway, Southern Railway (Great Britain), Southern Region of British Railways
locale=Great Britain
railroadclass=LSWR: M7
SR: M7
BR: M7; power class: 2P
disposition=Two preserved, remainder scrapped
preservedunits=Nos. 245 and 53

The LSWR M7 Class is a class of 0-4-4 passenger tank locomotive constructed in the late nineteenth and early twentieth centuries. The class was designed by Dugald Drummond for use on the intensive London network of the London and South Western Railway (LSWR), and performed well in such tasks. Because of their utility the class went through several modifications over five production batches, and for this reason there were detail variations such as frame length.

Demoted to rural branchline services in Devon and Dorset, the class was fitted with push-pull operation gear that enabled efficient use on such duties without the need to change to the other end of its train at the end of a journey. Members of the class lasted in service until 1964, and two examples have survived into preservation: number 245 in the National Railway Museum, and 53 (as BR 30053) on the Swanage Railway.

Background

Drummond built these locomotives to answer the need for a larger and more powerful version of William Adams' 0-4-4 T1 class of 1888. The LSWR required a locomotive with such attributes because the suburban services were intensifying around London at a rate which began to preclude the use of the older classes of locomotive. From previous experience on the North British Railway in Scotland the new class was a development of Drummond's NBR 157 class of 1877, itself an enlargement of the LB&SCR D1 class. Rutherford, Michael: "The Drummond Age" Part Four. (Railway Reflections No.109: Backtrack, 2005, 19), 102–110]

Construction history

The M7 tank locomotive was the first design by Dugald Drummond upon replacing William Adams as Locomotive Superintendent of the LSWR in 1895. The Adams T1 design of 1888 with 5ft 7in wheels had been developed as an answer to the LSWR's requirement for a compact and sure-footed suburban passenger locomotive to be utilised on the intensive commuter timetables around London.Casserley, H.C.: "London and South Western Locomotives" (London: Ian Allan, 1971 ISBN 7110 0151 0 — incorporating F. Burtt: LSWR Locomotives - a survey 1873-1922, published 1949) p.p. 55-57] Drummond's M7 was an enlargement on this with a sloping grate of increased area giving greater power. The first 25 were constructed at Nine Elms works between March and November 1897. It was the heaviest 0-4-4 type ever to run in Britain.

The M7 class had a long production run with five major sets of design variants. Between 1897 and 1899 the locomotives were constructed with a short overhang at the front, and sandboxes combined with the front splashers. Injectors and a lever-type reverser were also added, and a conical, as opposed to flat, smokebox door was implemented on numbers 252–256. Bradley, D. L.: "An illustrated history of LSWR Locomotives: the Drummond Classes" (Didcot: Wild Swan Publications, 1986) ISBN 0906867428 ] In 1900 the design was modified to incorporate the sandboxes inside the smokebox; these were later relocated below the running plate.

From 1903 a longer overhang at the front end was introduced and steam reversing gear fitted. The 1904/05 construction batch moved the sandboxes back to the front splasher and new items were feed water heating, single ram pumps and balanced crank axles. For the remainder of construction from the outshopping of the 105th locomotive in 1911, duplex pumps were fitted. However, none of the class featured superheated boilers except for number 126, which was experimentally fitted with one in 1921.

After 1912 class members were equipped with push-pull train capabilities with the provision of a primitive cable and pulley device. This was a modification that was designed to save time on country branch lines where the locomotive would usually have to run around its train in order to make a return journey. As a result it was possible for the driver to drive his train from a cab located at the front of a designated push-pull coach, leaving the fireman to tend the fire and operate the injectors on the locomotive footplate.

The pulley system was eventually deemed unsafe due to instances of sagging and delayed reaction. As a result it was replaced on 36 engines by a safer compressed air system between 1930 and 1937. This system had seen previous successful use on the LBSCR. Because the air compressor required extra space for installation, these conversions were confined to the long-framed members of the class.

Operational details

When first introduced to LSWR metals, several of the class were allocated to work express passenger services between Exeter and Plymouth. However they were withdrawn from this duty after a high speed derailment at Tavistock. As a result the class was to become synonymous with local main line and branch workings, as well as London suburban services, until this role was overtaken by electrification or more modern steam motive power after Nationalisation.

Apart from numbers 126, which was withdrawn in 1937 after being experimentally fitted with the superheated boiler and enlarged cylinders in 1921, and 672, which in 1948 fell down the lift shaft which provided roling stock access to the Waterloo and City Line at Waterloo, all M7s entered into British Railways service after 1948. In LSWR and Southern days they had been successful suburban passenger engines, though with the increased availability of newer, standard designs, they were diagrammed to take on a new role as reliable branch line engines, especially in South West England.

As a result a further four conversions to push-pull capability appeared between 1960 and 1962. Longworth, Hugh: "British Railway Steam Locomotives: 1948-1968" (Oxford Publishing Company: Oxford, 2005) ISBN 0860935930] This was the result of short-framed M7s having long frames substituted during overhaul in order to create room for the air compressor. By the end of 1963 the majority that remained were based at Bournemouth to work the Swanage branch. They were eventually replaced by more modern motive power in May 1964, and all remaining members of the class were withdrawn as part of the Modernisation Plan.

Preservation

Two examples of this quintessential class of steam locomotive have survived into preservation. They are:
*No. 245 (built 1897) is at the National Railway Museum in York Surviving records indicate that number 245 was constructed in 1897 at the cost of £1,846, and lasted in service until 1962.
*No. 30053 (built 1905) is based at the Swanage Railway; this locomotive was sold to Steamtown near Scranton, Pennsylvania in the United States of America in 1967, but was repatriated in 1987.

Livery and numbering

LSWR and Southern Railway

Under the LSWR the class saw various liveries over its pre-grouping career. Most associated with the class during this period was the LSWR passenger sage green livery with purple-brown edging, creating panels of green. This was further lined in white and black with 'LSWR' in gilt on the water tank sides, and the locomotive number on the coal bunker sides.

When transferred to Southern Railway ownership after 1923 the locomotives were outshopped in Richard Maunsell's darker version of the LSWR livery, with numbering having an 'E' prefix to denote Eastleigh rather than Nine Elms, due to the predominant number of the class constructed there. Swift, Peter: "Maunsell 4-6-0 King Arthur Class" (Locomotives in Detail series volume 4) (Hinckley: Ian Allan Publishing, 2006), ISBN 0711030863 ] This was to prevent confusion with other locomotives of the same number inherited by the Southern from its constituent railways. The gilt lettering was changed to yellow with 'Southern' on the water tank sides with black and white lining.Haresnape, B. & Rowledge, P.: "Drummond Locomotives: A Pictorial History" (Hinckley: Ian Allan Publishing,1982) ISBN 0711012067]

With the appointment of Oliver Bulleid as Chief Mechanical Engineer of the Southern, livery policy was changed once again to malachite green for passenger locomotives, with 'Sunshine Yellow' lettering on the tank sides. This was lined with yellow and black with solid black edging. The numbers also lost their 'E' prefix. During the war years the locomotives were outshopped in wartime black after overhaul, and some of the class retained this livery to Nationalisation. Numbering depended on which batch the locomotive belonged to, and therefore each batch was allocated a series.

Post-1948 (nationalisation)

The M7 Class was given the BR Power Classification of 2P upon Nationalisation. Longworth, Hugh: "British Railway Steam Locomotives: 1948–1968" (Oxford Publishing Company: Oxford, 2005) ISBN 0860935930] Livery remained Southern lined malachite, though two which were painted soon after (numbers 30038/30244) were lettered for British Railways in 'sunshine yellow' Gill Sans style along the sides of their tanks. This was eventually replaced with BR lined mixed traffic black livery. Numbering was initially that of the Southern, though for a period an 'S' prefix was added to the number. This was replaced with the BR standard numbering system, with all locomotives being allocated, by batch, numbers within the 30xxx series.

References

Further reading

*Ian Allan ABC of British Railways Locomotives, winter 1955–56 edition

External links

* [http://www.semgonline.com/steam/m7class_01.html SEMG gallery]