North British 4-4-0 Locomotives in Great_Britain


Class Details by Steve Llanso of Sweat House Media

Class "Scott" / D30/2 (Locobase 7529)

Data from "Ne Main Line Locomotives 'Scott' Class", Page's Engineering Weekly, Volume 26 (12 February 1915), p. 136. See also Richard Marsden's LNER Encyclopedia -- [], last accessed 6 June 2006. Also see Steamindex's summary of North British locomotive designs -- [] . The first two "Superheated Scotts"completed in 1912 are shown in Locobase 20082

The production engines had 24-element Robinsons and were delivered in three batches over a six-year period. Their piston valve measured 10" (254 mm) in diameter.

Once the NBR was taken into the London & North Eastern in 1923, the new railroad saw little need to modify beyond fitting the


Class 420 (Locobase 5205)

Information from engine diagram reproduced on [] (visited November 2002). See also [] article on North British locomotives (viewed 2 October 2004). See also "NBR 224 and 420 Classes" in Wikipedia at [], last accessed 17 August 2022.

These Thomas Wheatley bogie engines came out of NBR's shops two years after the pair described in Locobase 2988. The dimensions are essentially the same, but these are a touch heavier on the drivers. Their domes were moved forward to a position between the lead driving axle and the rear bogie axle and their bogie wheels measured 40" in diameter.

The "1192" must have come from a later renumbering.

Steamindex's summary comments that these locomotives "did their best work on the Waverley route until shortly after the opening of the route to Midland trains" and then pulled fast trains out of Edinburgh and Glasgow. After describing the struggles these engines trying to climbing ruling grades as Falahill and Whitrope, Wikipedia quotes Dugald Drummond, who succeeded Wheatley, as commenting NBR express engines were "like skinny chickens, all legs and wings." His later 476 class (Locobase 5206) displaced the 420s, which then hauled local trains.


Class 476 - 1902 rebuild (Locobase 7521)

Dugald Drummond express 8-wheeler (Locobase 5206) was of such quality that the railroad rebuilt the locomotives in 1902 & 1904 to incorporate a larger boilers. Information from from Richard Marsden's LNER Encyclopedia -- [], last accessed 6 June 2006.

The London and North Eastern subdivided the rebuilt Drummonds into two classes in 1923 according to the cab design: D27s were the 1902s with round cabs and wooden doors, the other half - D28 - had cabs with single side windows and inward-folding doors.

Relegated to lighter express trains, the class also served on special trains all through the NBR. Withdrawals began even before grouping in 1921 and only 7 were transferred to the LNER. All of the remaining engines were disposed of by September 1926.


Class 729 (Locobase 10092)

Data from G A Sekon, "Illustrated Interviews - Mr. John Conacher," Railway Magazine (April 1898), pp. 289-306. See also The Locomotive & Railway Carriage & Wagon Review, Vol III (June 1898).

This mid-sized express-passenger engine was described in the RM as designed by Matthew Holmes to "try conclusions with the 'Enlarged Dunalistairs'." (The latter were the famous Caledonian series.

NB: Tube length is calculated by subtracting the reported direct heating surface from the reported evaporative heating surface, then using the count and diameter of the tubes to derive the length required to achieve the tube heating surface.


Class D121 (Locobase 2988)

Data from "NBR 224 and 420 Classes" in Wikipedia at [], last accessed 17 August 2022; and Ahrons (1927), pp. 195. See also F W Brewer, "The Genesis and Early Development of the British 4-4-0 Tender Engine", Locomotive Magazine, Volume XXIX [29] (15 May 1923), several installments, but especially p 142; and, for the Nisbet tandem compound system, Malcom Peirson, "Compounds" in Richard Marsden's LNER Encyclopedia at [], last accessed 17 August 2022.

First inside-cylinder, inside-frame 4-4-0s in Britain were produced for the NBR to Thomas Wheatley's design. After one of these engines (224) pulled the train that plunged into the Tay River off Thomas Bouch's ill-fated bridge on 28 December 1879, it was known as "The Diver".

Six years later, the Diver underwent a transformation, emerging from the shops fitted with tandem compound cylinders of F H Nisbet's patent 16,967 applied for 27 December 1884. (Wikipedia describes Nisbet as a cousin of Matthew Holmes.) All four cylinders lay between the frames. Admitted by modified Joy valve gear, high-pressure steam entered the 13" (330 mm) diameter cylinders at the front of each casting, that cylinder's exhaust then travelling to the 20" (509 mm) cylinder fitted behind. Both cylinders travelled over a common 24" stroke. See Malcolm Peirson's detailed description in the LNER article noted above.

It wasn't a complete failure, but the advantages proved insufficient and the 224 regained its two-cylinder simple-expansion layout in 1887.

Steamindex's summary of North British locomotive design ([], viewed 2 Oct 2004) says that they had unusually small, solid bogie wheels measuring 33" in diameter. They were based in Fife.


Class D32/2 superheated (Locobase 7528)

Data from Richard Marsden's LNER Encyclopedia -- [], last accessed 7 June 2006. Also see Steamindex's summary of North British locomotive designs -- [] . Superheating the K class (Locobase 7527) in the constricted boilers used for most British locomotives meant dramatic shifts in the counts of tubes in favor of a relatively low degree of superheat. Such was the case with the D32/1, which in fact adopted the boiler used by the Superheated Scotts (Locobase 7529). Also, a comparison of engine weights and axle loadings suggests most of the increase in weight seems to fallen on one driving axle.


Class J "Scott" / D29 (Locobase 7526)

Data from Richard Marsden's LNER Encyclopedia -- [], last accessed 6 June 2006. Also see Steamindex's summary of North British locomotive designs -- [] . See also "New Locomotives for the North British Railway", The Model Engineer and Amateur Electrician, Volume 21 (9 December 1909), p. 565. North British Locomotive Company's six engines were works numbers were 18856-18861 in 1909. NBR's own Cowlairs works added ten more in September 19

Following on from the Class K (LNER D32 - Locobase 7527) locomotives, these Reid-designed Eight-wheeled express passenger engines continued the basic 4-4-0 layout used on the NBR. They pulled a larger tender than the Ks and had a slightly smaller boiler.

Scotts were Scottish to the core. Not only were they built in Glasgow to serve a Scottish railway, they bore names seen in the novels of the well-known Scottish author Sir Walter Scott. In order, the NBLC were dubbed Rob Roy, Dandie Dinmont, Red Gauntlet, Sir Walter Scott, Jeanie Deans, and The Fair Maid. Cowlairs engines were named Meg Merrilies, Madge Wildfire, Bailie Nicol Jarvie, Helen Macgregor, Ivanhoe, Lady of Avenel, Dirk Hatteraick, Guy Mannering, Vich Ian Vohr, and Ravenswood.

The last two were completed with superheated boilers; see Locobase 7529.


Class J/Scott//D30/1 (Locobase 15998)

Data from "New Main Line Engines 'Scott' Class", Page's Engieering Weekly, Volume 26, p. 554 (12 February 1915), p. 136; and "North British Railway 4-4-0 Superheated Main Line Engine, No. 411-Dominie Sampson", Railway Magazine, Volume , No 1 (January 1918), frontispiece and "Pertinent Paragraphs", p. 59.

The "paragraphs" discussing the colour plate in the frontispiece (when in England ...) note that the class as superheated had 10" (254 mm) piston valves. All of the engines were named for characters in Sir Walter Scott novels. Based on Locobase 7532


Class K "Glen" /D34 (Locobase 7530)

Data from "New Passenger Engine, North British Railway", Locomotive Magazine, Volume XIX [19] (15 November 1913), pp. 248-249. See also Richard Marsden's LNER Encyclopedia -- [], last accessed 7 June 2006. Also see Steamindex's summary of North British locomotive designs -- [] . Steamindex says that the Superheated Scotts proved the potential of superheating sufficiently to inspire production of a superheated Intermediate. This relatively large 4-4-0 had relatively large 10" (254 mm) piston valves admitting steam to the cylinders and good ratios among the steam-generating components.

Five of the first 10 had 24-element Schmidt superheaters whose area was given as 355 sq ft (32.98 sq m). Flue heating surface area worked out to be 366.4 sq ft ( 34.04 sq m). Total combined heating surface area came to 1,641 sq ft (152.45 sq m). The other five received 22-element Robinson superheaters. That configuration appears in the specs, which use the Diagram 78 boiler fitted in beginning in 1922.

Because Reid liked names on his locomotives, these engines received "Glen" names.

Ten were delivered in 1913, five in 1917, five in 1919, and twelve in 1920.

"They proved to be excellent engines for the West Highland line," says steamindex's overview, "although they worked successfully all over the system." Even on their core service, however, their trains frequently trailed behind a double-headed set of Ks as their tonnage rating over the worst parts was limited to 190 tons. Yet though larger six-coupleds had more capacity, says Marsden, "D34 Glens were better at handling the severely graded and awkward curves. The D34s proved to be reliable locomotives despite this punishment."

All but three remained in service well into the British Railways era, most retiring in 1959-1960.


Class K "Intermediates"/ D32 (Locobase 7527)

Data from Richard Marsden's LNER Encyclopedia -- [], last accessed 7 June 2006. Also see Steamindex's summary of North British locomotive designs -- [] . Steamindex's summary says:"This design was intended for the light, fast fish trains from Aberdeen and proved in practice to be an excellent mixed traffic engine. It worked trains of all types except the heaviest goods and passenger traffic." Like other NBR 4-4-0s, these were fitted with 8 3/4" (222 mm) piston valves.

Many in this class were refitted with a superheated boiler beginning in 1923; see Locobase 7528.


Class K / D26 (Locobase 7520)

Data from Richard Marsden's LNER Encyclopedia -- [], last accessed 6 June 2006. Also see Steamindex's summary of North British locomotive designs -- [] . A T Taylor, Modern British Locomotives (London: E & FN Spon, Ltd, 1907), p. 8.

Marsden says this was the last and best of Matthew Holmes's 4-4-0 designs. Steamindex says they were produced in response to rapidly increasing train weights on the Aberdeen and Waverley routes that were more than a match for the recently introduced 633s (M class; Locobase 2237). Steamindex notes that C Hamilton Ellis had described the class as identical to McIntosh's Dunalastair III on the Caledonian (Locobase 3751); indeed, the two designs had matching power dimensions and nearly the same heating surface details.

The K class's steel boilers were a first for the NBR as was the initial working pressure of 200 psi. Piston valves measuring 8 3/4" in diameter fed the cylinders. Marsden details their first assignments: "The first six D26s were initially allocated to Aberdeen to haul the express passenger services to Edinburgh. The last six were allocated to St. Margaret's. Two of these worked the line towards Aberdeen, and the remaining four worked the line to Carlisle. After a short interval, two of these latter engines were moved to Carlisle."

Inevitably, the class was bumped from mainline service by still larger locomotives and turned to working Perth and Glasgow. By 1915, the class was no longer assigned a regular turn. Reconstruction of the class with new boilers was cancelled because of the impending grouping within the LNER in 1923. Although given an LNER class ID as D26, they were soon retired because of poor condition of the frames.


Class L / D36 - superheated (Locobase 7532)

Data from Richard Marsden's LNER Encyclopedia -- [], last accessed 7 June 2006. Also see Steamindex's summary of North British locomotive designs -- [] . The approach to superheating in this locomotive seems to have preserved more of the saturated heating surface than most such conversions and achieved a moderate amount of superheat as well. Marsden notes that this proved to be an expensive overhaul and no others of the 1894 class from which it was drawn (Locobase 7531) were so modified.


Class M (Abbotsford) / D27 & D28 (Locobase 5206)

Dugald Drummond express 8-wheeler. Information from Bryan Attewell ([] locomotive simulator and supplied by Jim McDonnell. Additional information from Richard Marsden's LNER Encyclopedia -- [], last accessed 6 June 2006.

Information from the Steam Index summary of North British Railway locomotive designs ([], 11 July 2004.) notes that Drummond delivered the first four - Carlisle, Edinburgh, Meirose, and Abbotsford -- in 1877. He sought more power than the 420 class 2-4-0s described in Locobase 5205.

They have been described as combining "the Drummond qualities of rugged simplicity and beauty of design." The steamindex summary notes too that "They could climb and they could run. They ran the 98 miles from Edinburgh to Carlisle in 2 hours and 10 minutes with trains of 117 tons, burning only 28 lb of coal per mile [7.89 kg/km]."

The other eight were delivered a year later with Neilson's supplying Aberdeen, Montrose, Galashiels, and Hawick and Cowlairs shops the St Boswells, Dalhousie, Newcastleton, and Netherby.

Beginning in 1902, the Abbotsfords were rebuilt with bigger boilers.


Class M / D31 (Locobase 2237)

Data from Charles John Bowen Cooke, British Locomotives-Their History, Construction, and Modern Development (London:áWhittaker,á1900), p. 312..

Latter class of a Matthew Holmes design originally derived from Dugald Drummond. The first twelve were delivered with boilers set at 140 psi, the second batch had the 150 psi shown in the specs. The 592s' 84" drivers were replaced by 78" drivers in the design. Steamindex.com's summary of North British locomotives ([]) gives the original allocation of this class as follows:

"Nos 633-5 and 642 were allocated to Perth when new; 262-3, 312, 401 and 211-2 went to Aberdeen, 213-16 to St Margarets and 217-8 to Carlisle."

Taken into the LNER as Class D31.


Class N "West Highland Bogies" / D35 (Locobase 7531)

Data from Richard Marsden's LNER Encyclopedia -- [], last accessed 7 June 2006; and "Four-Coupled Bogie Engine, NBR", Moore's Monthly Magazine, Volume 1, No 4 (April 1896), p 39.. Also see Steamindex's summary of North British locomotive designs -- [] . These low-drivered, inside-cylinder passenger engines were designed for traffic on the newly opened West Highland line from Craigendoran to Fort William. The 99 1/2 miles (160 km) miles presented a 2% ruling grade, but many inclines were "little easier, " added the MMR's report, "the severity of the gradients being enhanced by the numerous curves which abound throughout the whole distance." It topped out at 1,347 ft (411 m) above sea level.

Steamindex noted that the RCTS history of locomotives asserted that these fell short of other Holmes' 4-4-0s, suffering "... from a lack of adhesion and ...alleged to be capable of slipping on Portobello sands. Presumably the demands of the Civil Engineer had led to this excessively low adhesion factor." (A calculated factor of adhesion pegged at 4.28 doesn't suggest that ratio was the source.)

The class was out of service by 1924, except for 695, which was rebuilt with a superheater in 1919. See Locobase 7532.


Class N / D25 (Locobase 2238)

M. Holmes design based on that of Dugald Drummond. Steamindex.com's summary of North British locomotive design ([], 2 Oct 2004) says these were the first express engines procured by the NBR in 10 years. Holmes's contributions were a flat grate (as opposed to the sloping Drummond design), a rounded cab and tender. Most visually dramatic must have been the substitution of 84" drivers for the 78" wheels of the earlier locomotives.

Six were delivered in 1886 and six in 1888. Later classed by the LNER as D25.

See [] (visited November 2002).


Class P / D50 (Locobase 6408)

Data from John F Winton & WJ Millar, The Engineer's Encyclopedia, Volume II (Philadelphia: Gebbie & Company, 1892), pp.705-710.

Richard Marsden comments that Dugald Drummond adopted Wheatley's bogie design for several of his own locomotives. .

Named Craigendoran, Rosenheath, and Helensburgh, this trio was built to replace some 0-4-2Ts of Drummond that pulled local services along the Clyde coast between Glasgow and Helensburgh Subjected to reboilering in 1905, they only survived Grouping by 3 years, being withdrawn in 1926.


Class R (Locobase 10250)

Data from "The Carmyllie Light Railway.," Locomotive Magazine, Vol VII (December 1902), p. 204-205 and from [], last accessed 24 April 2009. The Study Group gives the following road numbers for this class: 19, 33, 52, 60, 67, 72-79, 98-99, 101, 103-105, 109-111, 147, 174, 225, 268, 294, 299, 316, 483.

Although the locomotive shown was built for the NBR 20 years earlier, its data showed up in this article because the NBR and Caledonian provided motive power for the CLR in alternate years. Somewhat unusually, this class of branch-line tanks had solid bogie wheels (rather than spoked), which gave them an even more solid look.

These were reboilered by Reid in 1908 and it was in that form that they were taken up by the LNER upon Grouping in 1923; see Locobase 3769.

See also [] for drawings of many


Class R - reboilered / D51 (Locobase 3769)

Dugald Drummond designed these side tank engines for light work on secondary lines. They were, says Glover (1967), of "conventional design, with inside cylinders, frames, and side tanks.." Some of them eventually came into the LNER as the D51 class -- 43 years or so after they first entered service.

Data from Bryan Attewell ([] Steam locomotive simulator (April 2000 edition), from Glover, and from Richard Marsden, [] . Data reflects the class after they were reboilered by Reid.


Class The Dougal Cratur // D30/1 (Locobase 20082)

Data from "Superheater Express Locomotive, North British Railways," Locomotive Magazine, Volume XVIII (14 December 1912), p. 251.

These were the first two "Superheated Scotts", and were enlarged versions of the popular Sir Walter Scott class. The Dougal Cratur and Hal o' the Wynd had piston valves and the Schmidt superheater. LM noted that they would run over the Waverley route between Edinburgh and Carlisle and were named for characters in Scott's Waverley novels. "The large high-pitched boiler gives these engines a bold and handsome appearance, and their ample dimensions should enable to give good work in service."

When the superheated design proved superior, the NBR ordered 25 more to a considerably modified design; see Locobase 7529.

Principal Dimensions by Steve Llanso of Middle Run Media

Class"Scott" / D30/2420476 - 1902 rebuild729D121
Locobase ID7529 5205 7521 10092 2988
RailroadNorth BritishNorth BritishNorth BritishNorth BritishNorth British
CountryGreat BritainGreat BritainGreat BritainGreat BritainGreat Britain
Whyte4-4-04-4-04-4-04-4-04-4-0
Number in Class3541262
Road Numbers409-428, 497-501/9409-9428, 9497-9501420-423 / 1192476-479, 486-493729224, 264
GaugeStdStdStdStdStd
Number Built35462
BuilderseveralCowlairsCowlairsCowlairsCowlairs
Year19141873190218961871
Valve GearStephensonStephensonStephensonStephensonStephenson
Locomotive Length and Weight
Driver Wheelbase (ft / m) 9.50 / 2.90 7.59 / 2.319 / 2.74 7.59 / 2.31
Engine Wheelbase (ft / m)23.58 / 7.1920.29 / 6.1822.08 / 6.7330.68 / 9.35
Ratio of driving wheelbase to overall engine wheelbase 0.40 0.37 0.41
Overall Wheelbase (engine & tender) (ft / m)45.07 / 13.7430.68 / 9.35
Axle Loading (Maximum Weight per Axle) (lbs / kg)43,456 / 19,71128,560 / 12,95538,080 / 17,273
Weight on Drivers (lbs / kg)84,784 / 38,45752,416 / 23,77651,968 / 23,572
Engine Weight (lbs / kg)129,472 / 58,72882,992 / 37,645104,384 / 47,348105,280 / 47,75482,992 / 37,645
Tender Loaded Weight (lbs / kg)104,496 / 47,39945,584 / 20,67771,68085,120 / 38,610
Total Engine and Tender Weight (lbs / kg)233,968 / 106,127128,576 / 58,322176,064 / 47,348190,400 / 86,364
Tender Water Capacity (gals / ML)4200 / 15.91
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)
Minimum weight of rail (calculated) (lb/yd / kg/m)71 / 35.5044 / 2243 / 21.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)78 / 198180 / 203278 / 198178 / 198178 / 1981
Boiler Pressure (psi / kPa)165 / 11.40140 / 9.70175 / 12.10175 / 12.10150 / 10.30
High Pressure Cylinders (dia x stroke) (in / mm)20" x 26" / 508x66017" x 24" / 432x61018.25" x 26" / 464x66018.25" x 26" / 464x66017" x 24" / 432x610
Tractive Effort (lbs / kg)18,700 / 8482.1910,317 / 4679.7216,514 / 7490.6316,514 / 7490.6311,338 / 5142.84
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.53 5.08 4.58
Heating Ability
Tubes (number - dia) (in / mm)136 - 1.875" / 48202 - 1.75" / 44254 - 1.75" / 44254 - 1.75" / 44206 - 1.75" / 44
Flues (number - dia) (in / mm)24 - 5" / 127
Flue/Tube length (ft / m)11.67 / 3.5610.67 / 3.25
Firebox Area (sq ft / m2)139.70 / 12.9890.53 / 8.41126 / 11.71126 / 11.7187
Grate Area (sq ft / m2)21.13 / 1.9616.60 / 1.5420 / 1.8620 / 1.8617 / 1.58
Evaporative Heating Surface (sq ft / m2)1286 / 119.471039 / 96.561350 / 125.461350 / 125.461059 / 98.42
Superheating Surface (sq ft / m2)355 / 32.98
Combined Heating Surface (sq ft / m2)1641 / 152.451039 / 96.561350 / 125.461350 / 125.461059 / 98.42
Evaporative Heating Surface/Cylinder Volume136.03164.79171.50171.50167.96
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation34862324350035002550
Same as above plus superheater percentage42532324350035002550
Same as above but substitute firebox area for grate area28,12212,67422,05022,05013,050
Power L111,7524416572257224621
Power MT611.17371.47392.07

Principal Dimensions by Steve Llanso of Middle Run Media

ClassD32/2 superheatedJ "Scott" / D29J/Scott//D30/1K "Glen" /D34K "Intermediates"/ D32
Locobase ID7528 7526 15998 7530 7527
RailroadNorth BritishNorth BritishNorth BritishNorth BritishNorth British
CountryGreat BritainGreat BritainGreat BritainGreat BritainGreat Britain
Whyte4-4-04-4-04-4-04-4-04-4-0
Number in Class16203212
Road Numbers895-900, 243-245, 338-340, 359-362409-428882-893
GaugeStdStdStdStdStd
Number Built16203212
BuilderLNERseveralCowlairsCowlairsCowlairs
Year19231909191819131906
Valve GearStephensonStephensonStephensonStephensonStephenson
Locomotive Length and Weight
Driver Wheelbase (ft / m) 9.50 / 2.90 9.50 / 2.90
Engine Wheelbase (ft / m)23.58 / 7.1923.58 / 7.1923.58 / 7.1923.58 / 7.19
Ratio of driving wheelbase to overall engine wheelbase 0.40 0.40
Overall Wheelbase (engine & tender) (ft / m)46.70 / 14.23
Axle Loading (Maximum Weight per Axle) (lbs / kg)44,576 / 20,21941,216 / 18,69539,088 / 17,73042,784 / 19,40742,336 / 19,203
Weight on Drivers (lbs / kg)81,536 / 36,98484,784 / 38,457
Engine Weight (lbs / kg)120,288 / 54,562122,752 / 55,679129,472 / 58,728128,128 / 58,118118,720 / 53,851
Tender Loaded Weight (lbs / kg)103,040 / 46,738104,496 / 47,399104,496 / 47,399
Total Engine and Tender Weight (lbs / kg)225,792 / 102,417233,968 / 106,127223,216 / 101,250
Tender Water Capacity (gals / ML)5082 / 19.255080 / 19.24
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) 7.70 / 7 7.70 / 7
Minimum weight of rail (calculated) (lb/yd / kg/m)68 / 3471 / 35.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)72 / 182978 / 198178 / 198172 / 182972 / 1829
Boiler Pressure (psi / kPa)180 / 12.40190 / 13.10170 / 11.70180 / 11.40190 / 13.10
High Pressure Cylinders (dia x stroke) (in / mm)19" x 26" / 483x66019" x 26" / 483x66020" x 26" / 508x66020" x 26" / 508x66019" x 26" / 483x660
Tractive Effort (lbs / kg)19,945 / 9046.9119,434 / 8815.1219,267 / 8739.3722,100 / 10024.4021,053 / 9549.49
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.20 4.40
Heating Ability
Tubes (number - dia) (in / mm)124 - 1.75" / 44258 - 1.875" / 48136 - 1.875" / 48124 - 1.75" / 44285 - 1.875" / 48
Flues (number - dia) (in / mm)22 - 5" / 12724 - 5" / 12722 - 5" / 127
Flue/Tube length (ft / m)11.67 / 3.5610.25 / 3.1211.83 / 3.6111.58 / 3.53
Firebox Area (sq ft / m2)139.70 / 12.98139.78 / 12.99139.70 / 12.98139.70 / 12.98140 / 13.01
Grate Area (sq ft / m2)21.13 / 1.9621.13 / 1.9621.13 / 1.9621.13 / 1.9622.50 / 2.09
Evaporative Heating Surface (sq ft / m2)1153 / 107.161618 / 150.321285 / 119.381153 / 107.121760 / 163.51
Superheating Surface (sq ft / m2)193 / 17.94355 / 32.98193 / 17.93
Combined Heating Surface (sq ft / m2)1346 / 125.101618 / 150.321640 / 152.361346 / 125.051760 / 163.51
Evaporative Heating Surface/Cylinder Volume135.14189.64135.92121.96206.28
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation38034015359238034275
Same as above plus superheater percentage43364015438243364275
Same as above but substitute firebox area for grate area28,66626,55828,97428,66626,600
Power L19085670712,10681996574
Power MT362.70629.58

Principal Dimensions by Steve Llanso of Middle Run Media

ClassK / D26L / D36 - superheatedM (Abbotsford) / D27 & D28M / D31N "West Highland Bogies" / D35
Locobase ID7520 7532 5206 2237 7531
RailroadNorth BritishNorth BritishNorth BritishNorth BritishNorth British
CountryGreat BritainGreat BritainGreat BritainGreat BritainGreat Britain
Whyte4-4-04-4-04-4-04-4-04-4-0
Number in Class121122424
Road Numbers317-322, 325-332765476-479, 486-493633-643, 36-7
GaugeStdStdStdStdStd
Number Built12122424
BuilderCowlairsCowlairsNeilson & CoCowlairsCowlairs
Year19031919187718901894
Valve GearStephensonStephensonStephensonStephensonStephenson
Locomotive Length and Weight
Driver Wheelbase (ft / m) 9.50 / 2.909 / 2.749 / 2.749 / 2.74 8.17 / 2.49
Engine Wheelbase (ft / m)23.58 / 7.1922.17 / 6.7622.08 / 6.7322.10 / 6.7421.25 / 6.48
Ratio of driving wheelbase to overall engine wheelbase 0.40 0.41 0.41 0.41 0.38
Overall Wheelbase (engine & tender) (ft / m)46.71 / 14.2443.52
Axle Loading (Maximum Weight per Axle) (lbs / kg)40,992 / 18,59439,088 / 17,73034,944 / 15,85032,480 / 14,733
Weight on Drivers (lbs / kg)89,600 / 40,64266,080 / 29,97368,880 / 31,24363,392 / 28,754
Engine Weight (lbs / kg)166,480 / 75,514110,992 / 50,345103,936 / 47,145102,816 / 46,637121,184 / 54,968
Tender Loaded Weight (lbs / kg)89,600 / 40,64275,15271,680 / 32,51471,680 / 32,51471,680 / 32,514
Total Engine and Tender Weight (lbs / kg)256,080 / 116,156186,144 / 50,345175,616 / 79,659174,496 / 79,151192,864 / 87,482
Tender Water Capacity (gals / ML)4230 / 16.023000 / 11.363000 / 11.363000 / 11.36
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) 7.70 / 7 5.50 / 56 / 5.50
Minimum weight of rail (calculated) (lb/yd / kg/m)75 / 37.5055 / 27.5057 / 28.5053 / 26.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)78 / 198167 / 170278 / 198178 / 198167 / 1702
Boiler Pressure (psi / kPa)200 / 13.80165 / 11.40150 / 10.30150 / 10.30150 / 10.30
High Pressure Cylinders (dia x stroke) (in / mm)19" x 26" / 483x66019" x 26" / 483x66018" x 26" / 457x66018" x 26" / 457x66018" x 24" / 457x610
Tractive Effort (lbs / kg)20,457 / 9279.1519,648 / 8912.1913,770 / 6245.9713,770 / 6245.9714,798 / 6712.27
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.38 4.80 5.00 4.28
Heating Ability
Tubes (number - dia) (in / mm)254 - 1.875" / 48142 - 1.75" / 44238 - 1.75" / 44236 - 1.75" / 44
Flues (number - dia) (in / mm)18 - 5" / 127
Flue/Tube length (ft / m)11.58 / 3.5310.50 / 3.2010.42 / 3.18
Firebox Area (sq ft / m2)133 / 12.36120.50 / 11.20102.67 / 9.54118 / 10.97104.72 / 9.73
Grate Area (sq ft / m2)22.50 / 2.0919.50 / 1.8121 / 1.9520 / 1.8617 / 1.58
Evaporative Heating Surface (sq ft / m2)1577 / 146.511062 / 98.701081 / 100.431266 / 117.661235 / 114.74
Superheating Surface (sq ft / m2)220 / 20.45
Combined Heating Surface (sq ft / m2)1577 / 146.511282 / 119.151081 / 100.431266 / 117.661235 / 114.74
Evaporative Heating Surface/Cylinder Volume184.83124.47141.17165.33174.72
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation45003218315030002550
Same as above plus superheater percentage45003764315030002550
Same as above but substitute firebox area for grate area26,60023,26315,40117,70015,708
Power L168327870406047264167
Power MT336.20270.91302.53289.84

Principal Dimensions by Steve Llanso of Middle Run Media

ClassN / D25P / D50RR - reboilered / D51The Dougal Cratur // D30/1
Locobase ID2238 6408 10250 3769 20082
RailroadNorth BritishNorth BritishNorth BritishNorth BritishNorth British
CountryGreat BritainGreat BritainGreat BritainGreat BritainGreat Britain
Whyte4-4-04-4-0T4-4-0T4-4-0T4-4-0
Number in Class12330302
Road Numbers592494-49619+400, 363
GaugeStdStdStdStdStd
Number Built123302
BuilderCowlairsNeilsonCowlairsCowlairs
Year18861880188019081912
Valve GearStephensonStephensonStephenson
Locomotive Length and Weight
Driver Wheelbase (ft / m) 9.25 / 2.828 9.50 / 2.90
Engine Wheelbase (ft / m)22.35 / 6.8121.08 / 6.4317.87 / 5.4523.58 / 7.19
Ratio of driving wheelbase to overall engine wheelbase 0.41 0.38 0.40
Overall Wheelbase (engine & tender) (ft / m)
Axle Loading (Maximum Weight per Axle) (lbs / kg)37,408 / 16,96828,224 / 12,80244,072 / 19,991
Weight on Drivers (lbs / kg)67,312 / 30,53251,744 / 23,47184,812 / 38,470
Engine Weight (lbs / kg)103,152 / 46,789105,728 / 47,95778,848 / 35,765128,324 / 58,207
Tender Loaded Weight (lbs / kg)71,680 / 32,514103,040 / 46,738
Total Engine and Tender Weight (lbs / kg)174,832 / 79,303105,728 / 47,95778,848 / 35,765231,364 / 104,945
Tender Water Capacity (gals / ML)3000 / 11.36650 / 2.46720 / 2.73650 / 2.46
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) 5.50 / 5 2.20 / 2 2.20 / 2
Minimum weight of rail (calculated) (lb/yd / kg/m)56 / 2843 / 21.5071 / 35.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)84 / 213472 / 182960 / 152460 / 152478 / 1981
Boiler Pressure (psi / kPa)150 / 10.30150 / 9140 / 9.70140 / 9.70165 / 11.40
High Pressure Cylinders (dia x stroke) (in / mm)18" x 26" / 457x66017" x 26" / 432x66016" x 22" / 406x55916" x 22" / 406x55920" x 26" / 508x660
Tractive Effort (lbs / kg)12,786 / 5799.6413,306 / 6035.5111,170 / 5066.6311,170 / 5066.6318,700 / 8482.19
Factor of Adhesion (Weight on Drivers/Tractive Effort) 5.26 4.63 4.54
Heating Ability
Tubes (number - dia) (in / mm)206 - 1.75" / 44220 - 1.75" / 44142 - 1.75" / 44142 - 1.75" / 44152 - 1.5" / 38
Flues (number - dia) (in / mm)18 - 5.5" / 140
Flue/Tube length (ft / m)10.67 / 3.25 9.21 / 2.81 9.42 / 2.8713.67 / 4.17
Firebox Area (sq ft / m2)119 / 11.06101.40 / 9.4262 / 5.7679.96 / 7.43139.70 / 12.98
Grate Area (sq ft / m2)21 / 1.9516.50 / 1.5313.75 / 1.2821.13 / 1.96
Evaporative Heating Surface (sq ft / m2)1126 / 104.651177 / 109.35648 / 60.22666 / 61.901306 / 121.33
Superheating Surface (sq ft / m2)266 / 24.71
Combined Heating Surface (sq ft / m2)1126 / 104.651177 / 109.35648 / 60.22666 / 61.901572 / 146.04
Evaporative Heating Surface/Cylinder Volume147.04172.32126.57130.09138.14
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation3150247519253486
Same as above plus superheater percentage3150247519254079
Same as above but substitute firebox area for grate area17,85015,210868011,19426,969
Power L147204438262029159980
Power MT309.18248.39518.84

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