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Great Northern (UK) class O1 “Tangos”
London & North Eastern class O3
Great Britain | 1914
20 produced
Locomotive Magazine, January 1914

The O1 was designed by Sir Nigel Gresley for the Great Northern Railway to reduce the number of heavy coal trains between Grantham and London with more powerful locomotives. So far, the classes Q1 and Q2 with the 0-8-0 wheel arrangement had been used for this task and the required larger boiler was to be made possible by means of an additional axle. Since there were many diverging points to be run over when entering London, the additional axle was added as a leading axle to improve the running characteristics. The number of four coupled axles remained the same.

Schematic drawing with dimensions
Schematic drawing with dimensions
Locomotive Magazine, January 1914

Gresley derived the larger boiler from the class C1 Atlantic express locomotives that his predecessor Ivatt had developed. As with the 2-6-0 locomotives of the K1 and K2 classes, Gresley arranged the cylinders on the outside in order to be able to increase their dimensions. The very first engine showed its capabilities, hauling a train of 78 two-axle coal wagons and two 20-ton brake vans at speeds of up to 27.5 mph. Their predecessors had been limited to 60 cars.

LNER O3 No. 3491 in 1947 at Immingham Depot
LNER O3 No. 3491 in 1947 at Immingham Depot
Ben Brooksbank / Gresley ex-GNR Class O3 2-8-0 at Immingham Locomotive Depot

The first five locomotives were built in Doncaster in 1914, but the second order of 15 could not be completed due to the war. However, after the end of the war, the completed parts could be taken to the North British Locomotive Company and delivered as finished locomotives in 1918 and 1919. A development of the O1 was the O2 with three cylinders. As with all GNR stock, the O1 were taken over by the LNER in 1923 and were renamed O3 in 1944, as another locomotive called the O1 by Thompson was introduced at that time. When British Railways was founded in 1948, there were still 17 examples, all of which were retired by 1952.

General
Built1914-1919
ManufacturerDoncaster, North British
Axle config2-8-0 (Consolidation) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Length60 ft 11 1/2 in
Wheelbase26 ft 4 in
Rigid wheelbase18 ft 6 in
Service weight170,688 lbs
Adhesive weight150,976 lbs
Total weight267,232 lbs
Axle load39,984 lbs
Water capacity5,044 us gal
Fuel capacity16,016 lbs (coal)
Boiler
Grate area27 sq ft
Firebox area162 sq ft
Tube heating area1,922 sq ft
Evaporative heating area2,084 sq ft
Superheater area570 sq ft
Total heating area2,654 sq ft
Power Plant
Driver diameter56 in
Boiler pressure180 psi
Expansion typesimple
Cylinderstwo, 21 x 28 in
Power
Power sourcesteam
Estimated power1,200 hp (895 kW)
Optimal speed23 mph
Starting effort33,736 lbf
Calculated Values
steam locomotive
freight
Herbert Nigel Gresley
last changed: 04/2022
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