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Great Northern (UK) class K
London & North Eastern classes Q1, Q1s and Q2
Great Britain | 1901 | 55 produced
Locomotive Magazine, June 1901

To haul heavy coal trains from Peterborough to London, Ivatt developed the K class, which was soon dubbed the “Long Tom” because of its longer boiler compared to the six-coupled locomotives. The dimensions of this boiler roughly corresponded to the class 990 or C1 (small boiler) Atlantics. It could generate enough power to haul 60 full wagons of coal. This corresponded to a train weight of 1,052 long tons compared to 681 long tons for the previous, six-coupled freight locomotives. With the cylinder dimensions required for this, it was still possible to arrange the cylinders within the frame. From 1901 a total of 55 engines were made.

Although the engines could handle the required train weights without any problems, the high consumption of coal was noticeable. Therefore, from 1908 almost all engines were superheated, with two different variants being created. The first one, later designated by the LNER as the Q1s class, retained the original cylinder dimensions and piston slides. The other, which later became the LNER's Q2 class, used cylinders with a diameter of 21 instead of 20 inches and piston valves instead of slide valves. Both variants had Schmidt-type superheaters and both had the fully automatic Klinger-type lubrication required for superheated steam operation.

In 1913 number 445 was fitted with the Doncaster superheater developed by Gresley. No other engines with this superheater followed. From 1923, it was listed as class Q3 by the LNER due to the different performance characteristics. In 1914, number 420 was fitted with a significantly larger boiler. Since the other boilers of this type were finally used for the 2-6-0 machines of the K2 class, the 420 remained a one-off.

No. 420 with bigger boiler
No. 420 with bigger boiler
Locomotive Magazine, December 1918

In the 1920's the superheaters were replaced with the Robinson type which were standard on the LNER. With the introduction of the 2-8-0 locomotives of classes O1 and O2, the engines were no longer needed for transporting coal to London and were increasingly used in more northerly areas. During this time they were nicknamed “Sea Pigs” because of their high water consumption compared to other locomotives. From 1926 the retirement began, whereby the few locomotives with wet steam boilers were affected first. By 1935 all Q1s and Q2s were gone and the only Q3 lasted until 1937.

Variantas builtrebuilt Q1srebuilt Q2rebuilt No. 420
Axle config0-8-0 (Eight-coupled) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase41 ft 4 in
Fixed wheelbase17 ft 8 in
Service weight122,304 lbs124,768 lbs130,480 lbs135,408 lbs
Adhesive weight122,304 lbs124,768 lbs130,480 lbs135,408 lbs
Total weight213,920 lbs216,384 lbs227,024 lbs231,952 lbs
Axle load33,572 lbs33,600 lbs34,680 lbs36,848 lbs
Water capacity3,700 us gal3,700 us gal
Fuel capacitycoal12,320 lbs (coal)coal12,320 lbs (coal)
Power sourcesteam
Estimated power800 hp (597 kW)900 hp (671 kW)1,000 hp (746 kW)
Optimal speed18 mph21 mph19 mph22 mph
Starting effort28,414 lbf26,836 lbf29,586 lbf
Power Plant
Driver diameter56 in
Boiler pressure180 psi170 psi
Expansion typesimple
Cylinderstwo, 20 x 26 intwo, 21 x 26 in
Grate area24.5 sq ft24 sq ft
Firebox area136.8 sq ft135.5 sq ft144 sq ft
Tube heating area1,302.3 sq ft981.5 sq ft1,523 sq ft
Evaporative heating area1,439 sq ft1,117 sq ft1,667 sq ft
Superheater area254 sq ft403 sq ft
Total heating area1,439 sq ft1,371 sq ft2,070 sq ft
Calculated Values
steam locomotive
Henry Alfred Ivatt
last changed: 06/2022

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