BR Standard Class 6

Infobox Locomotive
powertype=Steam
name = BR Standard Class 6Clarke, David: "Riddles Class 6/7 Standard Pacifics", pp.80–87]

---

caption = 72006 "Clan MacKenzie" at Carlisle Kingmoor in 1965, prior to withdrawal.
designer = Robert Riddles
builder = Designed at BR Derby, constructed at BR Crewe Works
builddate = 1951–1952
totalproduction = 10
whytetype = 4-6-2 ("Pacific")
gauge = RailGauge|ussg
leadingsize = 3 ft 4 in (1.03 m)
driversize = 6 ft 2 in (1.89 m)
trailingsize = 3 ft 6 in (1.09 m)
length = 67 ft 8 in (22.5 m)
weight = 86 tons 19 cwt (88.35 tonnes)
locotenderweight= 136 tons, 2 cwt (138 tonnes)
fueltype = coal
fuelc

waterc

cylindercount = 2
cylindersize = 19 in × 28 in (48 cm × 71 cm)
boilerpressure = 225 lbf/in² (1551.32 kPa)
tractiveeffort = 27,520 lbf (137.894kN)
railroad= London Midland Region of British Railways,
Scottish Region of British Railways
locale=Great Britain
railroadclass=6P/5F|

The Standard class 6, otherwise known as the "Clan" Class, was a class of 4-6-2 "Pacific" steam locomotive designed by Robert Riddles for use by British Railways. Ten locomotives were constructed between 1951 and 1952, with a further 15 planned for construction. However, due to acute steel shortages in Britain, the order was continually postponed until it was finally cancelled on the publication of the 1955 for the re-equipment of British Railways.

The "Clan" Class was based upon the "Britannia" Class design, incorporating a smaller boiler and various weight-saving measures to increase the route availability of a "Pacific"-type locomotive for its intended area of operations, the west of Scotland. None survived into the preservation era. The "Clan" Class received a mixed reception from crews, with those regularly operating the locomotives giving favourable reports as regards performance. However, trials in other areas of the British Railways network returned negative feedback, a common complaint being that difficulty in steaming the locomotive made it hard to adhere to timetables.

The "Clan" Class locomotives took their names from a previous class that was being withdrawn from service at the time, indicating further their intended area of operations. The class was ultimately deemed a failure by British Railways, and the last was withdrawn in 1966. None survived into preservation, although a project to build the next locomotive in line, number 72010 "Hengist", is progressing on the East Somerset Railway.

Background

Under the initial scheme for the creation of a series of British Railways standard locomotives, larger passenger and mixed traffic types were intended to be of the 4-6-2 "Pacific" wheel arrangement, the main advantage of which was that it could be fitted with a wide firebox capable of burning a range of coal types and quality.Clarke, David: "Riddles Class 6/7 Standard Pacifics", p. 85] These "Pacifics" were originally intended to be produced in four power groups: 8, 7, 6, and 5, according to the system of power ratings inherited from the L.M.S. constituent company. Power groups 7, 6 & 5 were to be for mixed traffic (MT) service. The whole standardisation programme was launched with the building of the 7MT Britannia design in 1951; in the event, the 5MT proposal was dropped in favour of an updated version of the highly successful Stanier mixed traffic 4-6-0.Haresnape, Brian: "Loco profile no. 12: BR Britannias", p. 270] It was further appreciated that a "Pacific" of 6MT power could be built with a high enough route availability to fulfil all remaining requirements; this had been amply demonstrated by Oliver Bulleid, Chief Mechanical Engineer of the Southern Railway, who had developed a lighter version of his large 3-cylinder "Merchant Navy" Class in 1945. H.A.V. Bulleid, Oliver Bulleid's son, advocated that the resultant "Light Pacifics" had "almost 90%" route availability on the Southern railway network. [Bulleid, H. A. V.: "Bulleid of the Southern", p. 68] The advantages of such almost locomotive for use on some of the heavily restricted main lines in Scotland, such as the Dumfries to Stranraer line, had been further demonstrated by the remarkable performance of "Light Pacific" number 34004 "Yeovil" on the old Highland Railway to Inverness during the British Railways Locomotive Exchange Trials of 1948. During these trials, the locomotive showed that a "Light Pacific" had the potential to revolutionise the timetable over this difficult trunk route. As the general policy of the Railway Executive was to eliminate as far as possible the perceived complication of multi-cylinder locomotives, an equivalent 2-cylinder "Pacific" was produced by mounting a smaller and lighter boiler on the standard 7MT chassis.Haresnape, Brian: "Loco profile no. 12: BR Britannias", p. 271]

Design details

The arrangement consisted of a modified Standard Class 7 boiler, with smaller cylinders and other modifications to save weight and hence increase route availability. The wider firebox, designed for use with cheaper imported coal, was also utilised to spread its weight evenly over the axles, whilst the standard smokebox completed the boiler, which at 225 lbf/in² was rated at a lower working pressure than that of the "Britannias". A single chimney was incorporated into the design, although this was to create problems later on, due to its small diameter, which reduced the choke area that allowed the fierce exhaust blast to escape, reducing the overall efficiency of the locomotive. Similarities with the "Britannias" rested with the frames, tenders and running gear, allowing easy standardisation of parts common with other classes. The design was fitted with a standard set of two Walschaerts valve gear systems, and all members of the class were equipped with 4,200 gallon BR 1 tenders.

Construction history

Designed at the drawing offices of Derby Works, the new class was constructed at British Railways' Crewe Works between 1951 and 1952.Cox, E. S.: "British Railways Standard Locomotives", p. 61] The initial order was for 25 locomotives, but such was the immediacy of demand regarding a smaller version of the "Britannias" that a batch of 10 was rushed through construction before teething problems had been ironed out at the British Railways testing station at Rugby.Clarke, David: "Riddles Class 6/7 Standard Pacifics", p. 80] No more were constructed due to the steel shortages of the 1950s, and onset of the British Railways Modernisation Plan from 1954.

Initial modifications

After initial running-in, E.S.Cox was quoted as discerning a distinct "woolliness" in their steaming, and although they missed their appointment at the Rugby Testing Station due to late completion, some modifications were carried out, most notably to the diameter of the blastpipe, resulting in better steaming and increased power.Cox, E. S.: "British Railways Standard Locomotives", p. 64] Initially, the return cranks on the main driving wheels, were of LNER block-type as seen on Arthur Peppercorn's A1s and A2s, but this was changed to the simpler LMS four-stud fitting. With time, enough information had been gathered through operational feedback from crews to have allowed modifications to be applied to the other 15 on order, creating a better locomotive.

Naming the locomotives

The choice of locomotive names came from engineer and future railway historian Ernest Stewart Cox's desire to replicate the near extinct Ex-Highland Railway 4-6-0 "Clan" Class, therefore representing Scotland in the new organisation.Cox, E. S.: "British Railways Standard Locomotives", p. 62] The first of the class. No. 72000 "Clan Buchanan" was treated to a special ceremony at Glasgow Central Station on 15 January 1952 whereby the Lord Provost unveiled its nameplates.

Operational details

The "Clan Class" had a mixed reception when first introduced to British Railways locomotive crews due to the fact that there were only 10 locomotives in a class that was mostly confined to the North West of the railway network. This was due to the fact the low number of class members prevented effective training of locomotive crews throughout the nationalised network, and a degree of partisanship amongst crews towards newer locomotives further ensured this.Atkins, Philip: 'The enigma of the BR 'Clans' ' ("Steam World"), pp. 6–7] The entire class was also based predominantly at two depots throughout their working lives, these being Glasgow Polmadie and Carlisle Kingmoor, compounding their restricted circulation. However, factors such as these meant that they spent most of their short careers out of the limelight that the "Britannias" had, resulting in a relatively camera shy class of locomotive. Crews that used them on regular duties displayed their liking for the locomotives, and as such, could produce good work.Atkins, Philip: 'The enigma of the BR 'Clans' ' ("Steam World"), p. 10] However, the predominant number of crews who were unfamiliar with the "Clans" found them difficult to handle, leading to an undeservedly bad reputation.

The poor steaming characteristics of the class had been the result of rushed production, which was another factor that led to the bad reputation of the "Clan" Class.Farr, Keith: ' 'Clans' Highland and Lowland', pp. 722–723] Furthermore, they suffered from complaints regarding a lack of pulling power, although this can be attributed to indifferent handling and firing techniques, which certainly did not help the situation. However, had the Modernisation Plan been delayed, and the correct amount of investment made for undertaking the relevant modifications, such as streamlining of the steam passages and increased diameter blastpipe in a double-chimney layout, the "Clans" would have been free-steaming workhorses worthy of complementing the 'Britannias'.Farr, Keith: ' 'Clans' Highland and Lowland', p. 718] Without modification, they were still capable machines when handled properly, as various feats testifying this included regular ascents of Shap and Beattock with 14 carriages without the assistance of a banking locomotive.Atkins, Philip: 'The enigma of the BR 'Clans' ' ("Steam World"), pp. 9–10] Other arduous duties that the class frequently undertook were the regular turns on the Settle to Carlisle route, which has some of the steepest gradients and harshest working conditions of any British mainline. The Midland region was always short of top-link motive power and the "Clan" Class proved to be a very welcome addition to the fleet.

The engines also performed on Glasgow–Crewe, Manchester and Liverpool services, Edinburgh–Leeds services, Carlisle–Bradford services, and finally the Stranraer Boat Train workings.Barnes, Robin: 'Salute to the Scottish standard - Part 2', pp. 286–287] As more crews got used to them, the class could be found far from home territory at destinations as diverse as Aberdeen, Inverness, Port Talbot, Newcastle upon Tyne, Bristol, and even London. "Clan" number 72001 to this day remains the only Pacific locomotive to have worked over the West Highland Line, the result of a successful trial held in early 1956 to ascertain whether a Pacific type could traverse this steeply graded switchback line.Farr, Keith: ' 'Clans' Highland and Lowland', pp. 714–723] Having passed that test, a tribute to the versatility of the class, "Clan Cameron" was allowed to work special trains for the Clan Cameron gathering that took place in June of that year.Farr, Keith: ' 'Clans' Highland and Lowland', pp. 719–720]

In August 1958, number 72009 was tested on the Eastern Region, being based at Stratford MPD, though a preference for the "Britannias" meant that this sojourn was short-lived, lasting only a month. The locomotive was utilised on services from London Liverpool Street to Norwich, Clacton, and Harwich.'Experimental use of the "Clan" Class on the Liverpool Street-Clacton service', p. 218] At first they were mistakenly allocated Class 7 duties, in which the "Clans", although capable, were not able to keep to their allotted timings. This was part of the trials for the West Highland Line services mentioned earlier, but the locomotive was rejected for such duties on the grounds that they were "no better than a good B1". The result of these trials was that as both Standard Class 7 and 8 locomotives were moved north in 1961 after dieselisation started in earnest, the "Clans" were downgraded to secondary work. Maintenance was initially undertaken at Crewe Works, but responsibility was transferred to Cowlairs Works in the spring of 1958.Barnes, Robin: 'Salute to the Scottish Standard - Part 1', pp. 235–241] More varied work was allocated to them as their reliability improved, including working portions of the "Thames-Clyde Express" and the "Queen of Scots Pullman". They also deputised for the many failed diesel locomotives that plagued the network at the time, and were extensively used on freight workings.

Most Scottish and Midland region crews that used them regularly took to the class, and found that if used properly, running times were kept with ease. These crews rated them the most surefooted of any "Pacifics" available on the Midland Region, though other crews who tested them claimed that the "Clans" were prone to slipping, though this was the case with most "Pacific" designs.Barnes, Robin: 'Salute to the Scottish Standard - Part 2', pp. 288–290] Despite the various successes of the "Clans", the class was generally regarded as a failure, even with overall performance being just short of Riddles' aims.Barnes, Robin: 'Salute to the Scottish Standard - Part 1', pp.236–237] However, the premise of all British Railways Standard designs was for a hard working, easily maintained, economical, highly available, and all-purpose locomotive. In these respects, the "Clans" were highly successful.Barnes, Robin: 'Salute to the Scottish Standard - Part 2', p. 290]

Proposed second batch and withdrawal

Prior to the publishing of the Modernisation Plan advocating the change-over to diesel traction, there was a proposal to construct a second batch of the "Clan" Class, which was accepted as Crewe Works Order Lot 242. This authorised the construction of a further batch of fifteen "Clans" that included modifications to the original design. Originally scheduled for 1952 with frames constructed for 72010 "Hengist", acute steel shortages meant that the order was continually rescheduled until the publication of the British Railways Modernisation Plan finally halted the project. The initial name allocations for the new batch would seem to suggest several operating the Kent coast trains, hauling the Golden Arrow and other expresses, so that some of this batch would have been allocated to the Southern Region.'"CLANS" for the Southern' (Trains Illustrated), p. 406]

The first locomotives to be withdrawn from service were the Polmadie locos 72000-72004 en masse in December 1962, where after being moved first to Glasgow Parkhead and stored, they were eventually moved to Darlington for scrapping in 1964. Of the Kingmoor allocation, the first, number 72005, was withdrawn in April 1965, whilst the final loco was 72008 on 21 May 1966 from Carlisle Kingmoor shed. When No 72008 "Clan MacLeod" was finally scrapped in August 1966, it rendered the class extinct. Though this locomotive served British Railways for only fourteen years and three months, it was the longest serving "Clan".Clarke, David: "Riddles Class 6/7 Standard Pacifics", p.84]

Livery and numbering

The livery of the "Clans" was a continuation of the standard British Railways Brunswick green applied to express passenger locomotives after nationalisation. This was lined in orange and black, whilst the class was granted the power classification 6P.Clarke, David: "Riddles Class 6/7 Standard Pacifics", pp. 82–83] Following on from the "Britannias", the "Clans" were numbered under the British Railways standard numbering system in the 72xxx series.Clarke, David: "Riddles Class 6/7 Standard Pacifics", p. 82] All of the locomotives were numbered between 72000 and 72009, and featured brass nameplates with a black background, located on the smoke deflectors, though towards the end of their working lives, some nameplates were painted with a red background.Clarke, David: "Riddles Class 6/7 Standard Pacifics", p. 84]

Preservation

None have survived, though a start has been made on constructing a new locomotive that would have been the first of the uncompleted batch of 15, number 72010 "Hengist." This is currently taking place at the East Somerset Railway, resulting in the locomotive potentially being the 1000th locomotive to be built to a British Railways standard design.Thomas, Cliff: 'The Lazarus locomotives: BR Standard Class 6' ("The Railway Magazine": 2007, 1)]

Footnotes

References

* 'A New Light Pacific' ("Trains Illustrated": 1952, 5)
* Atkins, Philip. 'The enigma of the BR 'Clans' ' ("Steam World": 1992, 65)
* Barnes, Robin: 'Salute to the Scottish Standard - Part 1' ("Backtrack": 1996, 10.5)
* Barnes, Robin: 'Salute to the Scottish standard - Part 2' ("Backtrack": 1996, 10.6)
* '"CLANS" for the Southern' ("Trains Illustrated": 1954, 7)
* Clarke, David: "Riddles Class 6/7 Standard Pacifics (Locomotives in Detail volume 5)" (Ian Allan: Hinckley, 2006) ISBN 0711031770
* Cox, E. S.: "British Railways Standard Locomotives" (London: Ian Allan, 1966)
* 'Experimental use of the Clan class on the Liverpool Street-Clacton service' ("Locomotive, Railway Carriage and Wagon Review": 1958, 64)
* Farr, Keith: ' 'Clans' Highland and Lowland' ("Backtrack": 2001, 15)
* Haresnape, Brian: "Loco profile no. 12: BR Britannias" (Windsor: Profile Publications)
* Rogers, Colonel H. C. B.: "Transition from Steam" (London: Ian Allan) ISBN 0711010145
* Thomas, Cliff: 'The Lazarus locomotives: BR Standard Class 6' ("The Railway Magazine": 2007, 1)

Further reading

* Gilbert, Dr. P. T. (Ed.): "A Detailed History Of BR Standard Steam Locomotives Volume 1: Background to Standardisation and Pacific Classes" (Railway Correspondence & Travel Society (RCTS): 1994) ISBN 0901115819

ee also

* List of BR 'Clan' Class locomotives

External links

* [http://72010-hengist.org/index.html] Official Website
* [http://www.railuk.co.uk/steam/getsteamclass.php?item=CLAN Railuk database]
* http://www.tower-models.com/towermodels/ogauge/djh/k308/
* [http://www.swanagerailway.co.uk/news41.htm 1000th BR Standard steam locomotive to be built at Swanage]