British Railways 4-6-2 Locomotives in Great_Britain

Class Details by Steve Llanso of Sweat House Media

Class Britannia - Class 7 (Locobase 2128)

Designed by JF Harrison to be the standard mixed traffic engine of British Railways, this engine borrowed much from the LMS. Sturdy-looking and moderately powerful, these locomotives sported a relatively large grate in the Belpaire firebox, boiler with a straight first course and coned second course, inclined cylinders whose rake was imposed by loading gauge restrictions, and elephant-ear smoke lifters. Note that the tube diameter finally equalled that of US practice at the time, but that the tube/flue ratio resembled that of US engines 25 years earlier. (Later US engines had smaller, but more numerous flues.) Also, these engines had roller bearings on all axles. At peak output, these engines produced 2,100 IHP.

Although not as powerful as some of the LMS designs, Glover (1967) contends that the two-cylinder Brittanias "may be regarded as the highest combination of capacity and simplicity yet realized in this country.") They were "rugged, extremely simple ...with everything outside and get-atable ...hard-working and free-running engines," says Nock (RWC VI, pl 57). Holllingsworth (1982) summarizes their balance sheet: "They met their designers' goal of a locomotive that was easy to maintain, and also showed that they were the master of any express passenger task in Britain at the time."

See the very interesting exchange between Peter Kearon ( []) and Bob Fitzhugh ([]) about the slipping tendencies of the Brittanias. Kearon says they were very tricky, especially with the original patented multi-valve regulator. Fitzhugh's friendly rebuttal says the key was in watching the cylinder steam chest's pressure gauge. Richard HN Hardy (see Locobase 2314 for a discussion of this photographer and his extensive collection of LNER images; see [], accessed 8 May 2006) said that they needed to be driven "with a wide open regulator and short cut-off."

Class Class 6/Clan class (Locobase 2379)

See also [] (May 2023 url []), a group dedicated to building a new Clan; and [],

Designed by RA Riddles as a smaller companion to the Class 7, this locomotive was lighter on the track and ventured farther. Bryan Attwell, developer of a computerized steam locomotive simulator, notes that these "much derided" Clan class engines were "sure-footed."

The Hengist group offers an extended review of the design by Mr K.R.M. Cameron, Running and Maintenance Officer on the BR's Scottish Region that supports a positive opinion.:";'Few repairs have been necessary where the boilers of the class 6 engines are concerned, and no real difficulties have been experienced'. He confidently states that,'the firebox arrangement with its short wide firegrate is most efficient, and an ample supply of steam is assured for a minimum of fuel consumed', which is just about all that could be hoped for from any boiler. He also observes that to the crews, who were so used to long narrow boxes,'the performance obtained from the new type of boiler comes as a revelation'. The only problem he noted was,'the tendency with most Fireman until they become accustomed to the excellent steam producing qualities of the boiler, is to over-fire the engine,' all these observations must have pleased E. S. Cox who lead the design team."

The Hengist team notes that trials yielded a coal consumption average of 31.8 lb/mile (8.96 kg/km)and quote Cameron's view of the prospects for this locomotive over the long run: "'The figures obtaiined for evaporation ratio are ... fairly high and there is no question that its free steaming capabilities are the outstanding feature of the new engines and over a long period, as Firemen become thoroughly accustomed to the working of the engines, considerable economics in fuel consumption will be realised.' "

Hengist adds ES Cox (with a wry smile, perhaps) observed that the results of trials that "such runs encountered by our timing enthusiast would be rated pedestrian to a degree, and if regularly repeated would earn the class an indifferent reputation. On the other hand the same running, consistently repeated, would be the Motive Power Officers ideal of how a railway should be properly run.' He sums up by saying, 'The Clans earned full marks from their owning region; the same performances would probably contain hardly anything worth tabulating to interest the readers of the Railway Magazines.'"

Hengist team's "footnote" caps the discussion: "The Clans, not revolutionary but none the less a new design, went straight off the drawing board and into traffic, even missed their slot on the Rugby test plant. The engines spent their lives operating daily over routes which encompassed Shap, Beattock, Ais Gill and the tortuous line to Stranraer. Improvements were made as and when the locos were due for shopping in the light of alterations to the class 5 and class 7 machines."

As of May 2023, completion of 72010 Hengist--the 21st century addition to the Clan class-- still lay several years ahead. See progress reports at [], last accessed 21 May 2023.

Class Class 8 - Duke of Gloucester (Locobase 3106)

This was a one-of-a-kind last gasp at designing a steam passenger locomotive and it came up short, largely because there was little interest in solving the problems that a new design inevitably brings. Richard Drew (at []) notes thre big differences from British Rail's Brittanias: "3 cylinders, Caprotti valve gear and a much larger grate area."

Although it was reputed to be a powerful engine (although strictly in terms of tractive effort it seems only average), Drew quotes a driver from the Crewe North contingent as calling it the "Miner's Friend" for its high coal consumption. It also reportedly steamed poorly. 71000 ran only a few years before being hulked in 1962. It was saved from the scrap heap and restored beginning in 1974 and resumed steam operations as the Duke of Gloucester in 1986.

Locobase finds the revelations in the Duke of Gloucester site -- [] & [] , accessed 21 May 2006-- fascinating - they amount to an indictment of quality control and a vindication of the original design. In rebuilding the firebox's ashpan, the restorers found that the original had been produced with air spaces measuring a total of 72 sq in too small when compared with the construction drawings. So the locomotive was starved for air to begin with.

Then when the restoration group measured front-end appliances they found: "Quite clearly, the double chimney and blastpipe assembly fitted to No 71000 was unusually small." Indeed, the blastpipe and chimney each were smaller than any other contemporary two-cylinder Pacifics in British use. The result was a throttling of the locomotive's exhaust to a ridiculous degree. Not only did this mean a high back pressure, but it also rendered futile any attempt properly to set the poppet valve events.

Given that restoring the Duke to its original configuration would perpetuate the weaknesses that made the engine such a dog, its new owners elected to fix the problems, add a Kylchap double-exhaust, and attend to several other shortcomings. The overall effect was to achieve a triumph, summarized by its owners:

"Duke of Gloucester" ran again on main lines for seven years and continued to "rewrite history" - establishing a reputation for high speed running and feats of heavy haulage, with steam to spare and power in reserve. From the beginning it became a favourite on the famous Settle and Carlisle line, setting new standards of performance. 1995 saw it cover routes previously barred to steam traction for almost three decades including those from London Euston and Kings Cross. In October of that year, "Duke of Gloucester" climbed the notorious Shap bank on the West Coast main line and topped the summit at the highest speed ever attained with a heavy load. Weather conditions on the day were so atrocious the the engine could not fully opened out, for fear of wheelslip!"

Class Merchant Navy-Mod (Locobase 1433)

Data from [], last accessed 24 July 2012. See also Southern E-Group's account of the update at [], accessed 7 July 2006; Graham Glover, British Locomotive Design 1825-1960 (London: George Allen & Unwin Ltd, 1967). (Thanks to Alexander Blessing for his 27 April 2020 email pointing out an error in the description of the valve gear.)

Because the original Bulleid design (see 1432) had weaknesses that proved too maintenance-hungry for practical service, British Railways's R G Jarvish, of the BR's Chief Mechanical and Electrical Engineer's Department at Brighton was set the task of designing a modified upgrade. The shops rebuilt these engines in the mid-1950s. As Glover (1967) notes, the boiler remained essentially untouched, although superheat area was reduced by 25%.

The chain-driven valve gear, together with its leaky oil-bath casing, was replaced in the 1950s (February 1956-October 1959) by three set of Walschaerts gear. Boiler pressure, which had been higher than any other British locomotive design typically ran, was reduced to a more usual 250 psi. Finally, the air-smoothed casing was removed.

The Southern E-Group's site has a convenient summary of all the major modifications:

Valve gear replaced by three independent sets of Walschaert gear

A saddle fitted forward of the inside cylinder to eliminate frame fractures

A new circular smokebox with a cast-iron multiple-jet chimney, but retaining the existing oval smokebox door

Replacement of the steam reversing gear, something that was not possible prior to rebuilding

New superheater feeder and outside steam pipes to the outside cylinders

Replaced piston heads and rods (but the cylinder volume and 11" (279 mm) piston valves remained the same)

Oil bath eliminated

Elimination of air-smoothed casing to be replaced by conventional boiler casing and large smoke deflectors very much along the lines of contemporary BR standard classes, though the original cabs were retained albeit with lower part of the curved side sheeting cut away

Two new mechanical lubricators for cylinders and axleboxes

Regulator replaced

New ashpan

Replaced cylinder cocks

New sandboxes

Modified tenders (a quantity of which were available before the locomotives were rebuilt so this type of tender also ran for a short while with the class in its original form).

The E-Group adds: "One negative aspect was the need to fit balance weights to the BFB wheels, thus destroying the zero hammer blow of the originals." (BFB stood for Bulleid Firth Brown cast drivers, which were similar to Boxpok.)

It's possible that the redesign changed the look of the underlying boiler design (see Glover's comment in Locobase 1432), because the result is a handsome, powerful looking engine with conventional lines. In particular, the boiler steamed freely and the testing committee found no carbon monoxide in the smokebox except under deliberately contrived situations. And, says OS Nock (RWC VI, pl 47), "In their modified form, the Bulleid Pacifics did much hard and reliable work." One of them set the speed record for steam in the Southern region at 104 mph.

As the Southern E-Group notes, the rebuilt MNs didn't run for long even though the plan had been to operate the class until 1987. The first two to retire -- 35002 & 35015 -- were withdrawn in February 1964. The last five went in July 1967.

Class Peppercorn A1 (Locobase 1067)

Designed by Arthur Peppercorn, whose tenure on the predecessor LNER covered only the last 18 months and whose term in the BR was cut short by his early death in 1951.

This 49-engine class followed the 15-engine A2s, which were Peppercorn's substitute for a continued run of Thompson's Pacific design. Only fifteen of the 15 (60525-39) had the Kylchap stack; all of them rode on 74" drivers.

The A1s all had a distinctive Kylchap double-chimney for better draft. They were reportedly fast and economical engines, partly because they used Timken roller bearings on all axles and were fitted with relatively capacious 10" (254 mm) diameter piston valves. Note that these engines, along with the LNER A4s, were among the few British engines with CHS/superheater ratios of less than 4:1.

Data from [] (visited November 2002), the site of a group building the 50th A1. (60163 Tornado). According to the a1steam group, "Water is the most significant limitation with most locomotives hauling loaded trains at express speeds being limited to about 100 miles (160 km) between filling the tender. For the A1 class an average of 40-45 gallons (113-137 litres) per mile is to be expected. "

In the Particulars page, there's a slight anomaly in heating surface dimensions. The total heating surface is usually given as 3,141.37 sq ft. But, as the specs show, the totals actually add up to 3,159 sq ft (a disturbing 18 sq ft difference!....whatever.)

Class West Country-Mod (Locobase 1435)

See the Bulleid Society's history of the rebuild at [], last accessed 22 May 2020 and See also Southern Railway E-Group's account "Bulleid WC/BB 'West Country' and

'Battle of Britain' class 4-6-2" at [], last accessed 23 May 2020. at [] . A further note from"1940s express steam locomotive 'Eddystone' returns after a three-year ú350,000 overhaul" on the Swanage Railway Trust's website at [], last accessed 24 July 2021 . (Thanks to Alexander Blessing for his 27 April 2020 email pointing out an error in the description of the valve gear.)

60 of the novel West Country/Battle of Britain engines (Locobase 1434) were the subject of a program in which they were rebuilt to a design by British Railways's R G Jarvish, of the BR's Chief Mechanical and Electrical Engineer's Department at Brighton. Following on the heels of the Merchant Navy mods (Locobase 1433), the West Countrys were rebuilt in the later 1950s beginning with 34005 in June 1957 and ending with 34104 and 34108. (the 60 rebuilds in road number order were: 34001, 34003-34005, 34008- 34010, 34012- 34014, 34016- 34018, 34021-34022, 34024-34029, 34031-34032, 34034, 34036-34037, 34039-34040, 34042, 34044, 34045- 34048, 34050, 34052-34053, 34056, 34058-34060, 34062, 34071, 34077, 34082, 34085, 34087-34090, 34093, 34095-34098, 34100, 34101, 34104, 34108-34109).

Like the Merchant Navy rebuilds, the boiler was essentially untouched, although superheat was reduced and the pressure dropped to a more supportable 250 psi. Three sets of Walschaerts valve gear replaced the troublesome Bulleid patent chain drive. Both outside cylinders retained their outside-admission valves, but the inside cylinder got its steam from an inside-admission valve.

Hollingsworth (SPL, 1982) offers the warmest valedictory on the result: "[I]n this form ...they were unambiguously amongst the very best locomotives ever to run in Britain." Certainly, the SRT's report underscores that appraisal: Herston engineering works manager Graham Froud summarized the view: ": "The staff and volunteers at Swanage are delighted to welcome this established steam locomotive which is a firm favourite with our locomotive crews ...As one of the last classes of locomotives designed before the end of steam trains, 'Eddystone' has many features considered innovative at the time.

"From the enginemen's perspective, the large and comfortable cab - coupled with a free-steaming boiler and a proven capability for high speed running - made the Bulleid Pacifics firm favourites with footplate crews,"

Yet the Bulleid Society offers a more ambivalent, yet still positive verdict: "The evidence is conflicting as to whether, from a performance view, they were improved by rebuilding, but they were now the most modern express steam locomotives on British Railways and performed well until the end of Southern steam in July 1967."

One (34059, ex-21C159) was extensively restored and a new tender frame built to suppply it. Named Sir Archibald Sinclair, the Bluebell Railway put the engine back in service on 24 April 2009. "Eddystone", BR 34028 returned to service on the Swanage in April after a 3-year overhaul. (Locobase's physical proximity to Baldwin's famous 1906-built Eddystone

works meant the SRT's news item jumped off the page at him.)

Principal Dimensions by Steve Llanso of Sweat House Media

ClassBritannia - Class 7Class 6/Clan classClass 8 - Duke of GloucesterMerchant Navy-ModPeppercorn A1
Locobase ID2128 2379 3106 1433 1067
RailroadBritish RailwaysBritish RailwaysBritish RailwaysBritish RailwaysBritish Railways
CountryGreat BritainGreat BritainGreat BritainGreat BritainGreat Britain
Number in Class551013049
Road Numbers70000-7005472000-7200971,00035001-3503060114-60162
Number Built5510149
Valve GearWalschaertWalschaertWalschaertWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)14 / 4.2714 / 4.2714 / 4.2715 / 4.5715
Engine Wheelbase (ft / m)35.75 / 10.9036.75 / 11.2036.75 / 11.2036.25
Ratio of driving wheelbase to overall engine wheelbase 0.39 0.38 0.41 0.41
Overall Wheelbase (engine & tender) (ft / m)58.25 / 17.7535.75 / 10.9059.25 / 18.0661.50 / 18.7562.44 / 21.64
Axle Loading (Maximum Weight per Axle) (lbs / kg)45,360 / 20,57542,560 / 19,30549,28049,168 / 22,30250,064 / 22,709
Weight on Drivers (lbs / kg)137,760 / 62,487127,680 / 57,915147,840 / 67,059145,376 / 65,942149,072 / 67,618
Engine Weight (lbs / kg)210,560 / 95,509210,578 / 95,517226,800219,296 / 99,471235,648 / 106,888
Tender Loaded Weight (lbs / kg)110,096 / 49,939120,288119,392 / 54,155136,416 / 61,877
Total Engine and Tender Weight (lbs / kg)320,656 / 145,448347,088338,688 / 153,626372,064 / 168,765
Tender Water Capacity (gals / ML)6000 / 22.734250 / 16.105194 / 16.387200 / 27.275000 / 18.94
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) 7.80 / 711 / 9 5.60 / 59 / 8
Minimum weight of rail (calculated) (lb/yd / kg/m)77 / 38.5071 / 35.5082 / 4181 / 40.5083 / 41.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)74 / 188074 / 188074 / 188074 / 188080 / 2032
Boiler Pressure (psi / kPa)250 / 17.20225 / 15.50250 / 17.20250 / 17.20250 / 17.20
High Pressure Cylinders (dia x stroke) (in / mm)20" x 28" / 508x71119.5" x 28" / 495x71118" x 28" / 457x711 (3)18" x 24" / 457x610 (3)19" x 26" / 483x660 (3)
Tractive Effort (lbs / kg)32,162 / 14588.4627,517 / 12481.5239,077 / 17725.0533,495 / 15193.0937,397 / 16963.01
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.28 4.64 3.78 4.34 3.99
Heating Ability
Tubes (number - dia) (in / mm)136 - 2.125" / 54118 - 2.125" / 54136 - 2.125" / 54124 - 2.25" / 57121 - 2.25" / 57
Flues (number - dia) (in / mm)40 - 5.5" / 14035 - 5.5" / 14040 - 5.5" / 14040 - 5.25" / 13343 - 5.25" / 133
Flue/Tube length (ft / m)17 / 5.1817 / 5.1817 / 5.1817 / 5.1816.97 / 5.17
Firebox Area (sq ft / m2)210 / 19.52195 / 18.12226 / 21275 / 25.56245.30 / 22.80
Grate Area (sq ft / m2)42 / 3.9036 / 3.3448.60 / 4.5248.50 / 4.5150 / 4.65
Evaporative Heating Surface (sq ft / m2)2474 / 229.932073 / 192.592490 / 231.412451 / 227.792461 / 228.72
Superheating Surface (sq ft / m2)718 / 66.73592 / 55691 / 64.22612 / 56.88698 / 64.87
Combined Heating Surface (sq ft / m2)3192 / 296.662665 / 247.593181 / 295.633063 / 284.673159 / 293.59
Evaporative Heating Surface/Cylinder Volume243.00214.19201.29231.16192.29
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation10,500810012,15012,12512,500
Same as above plus superheater percentage12,810988214,82314,55015,250
Same as above but substitute firebox area for grate area64,05053,52868,93082,50074,817
Power L130,24324,01624,52527,14325,966
Power MT1451.971244.041097.171234.871152.03

Principal Dimensions by Steve Llanso of Sweat House Media

ClassWest Country-Mod
Locobase ID1435
RailroadBritish Railways
CountryGreat Britain
Number in Class60
Road Numbers
Number Built
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)15 / 4.57
Engine Wheelbase (ft / m)35.50 / 10.82
Ratio of driving wheelbase to overall engine wheelbase 0.42
Overall Wheelbase (engine & tender) (ft / m)
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)116,600 / 52,889
Engine Weight (lbs / kg)180,100 / 81,692
Tender Loaded Weight (lbs / kg)95,424 / 43,284
Total Engine and Tender Weight (lbs / kg)275,524 / 124,976
Tender Water Capacity (gals / ML)6300 / 23.86
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) 5.50 / 5
Minimum weight of rail (calculated) (lb/yd / kg/m)65 / 32.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)74 / 1880
Boiler Pressure (psi / kPa)250 / 17.20
High Pressure Cylinders (dia x stroke) (in / mm)18" x 24" / 457x610 (3)
Tractive Effort (lbs / kg)33,495 / 15193.09
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.48
Heating Ability
Tubes (number - dia) (in / mm)124 - 2.25" / 57
Flues (number - dia) (in / mm)40 - 5.25" / 133
Flue/Tube length (ft / m)17 / 5.18
Firebox Area (sq ft / m2)253 / 23.50
Grate Area (sq ft / m2)48.50 / 4.51
Evaporative Heating Surface (sq ft / m2)2451 / 227.71
Superheating Surface (sq ft / m2)612 / 56.86
Combined Heating Surface (sq ft / m2)3063 / 284.57
Evaporative Heating Surface/Cylinder Volume231.16
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation12,125
Same as above plus superheater percentage14,550
Same as above but substitute firebox area for grate area75,900
Power L126,824
Power MT1521.53

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Wes Barris