York & North Midland 4-2-0 Locomotives in Great_Britain

Class Details by Steve Llanso of Sweat House Media

Class Great A (Locobase 3030)

Data from John S Maclean, Locomotives of the North Eastern, 1841-1922 (London: Locomotive Publishing Company, 1922), pp.5-7; and Gustav Reder (Michael Reynolds, trans), The world of steam locomotives (New York: Putnam, 1974)

In November 1845, the nonpareil engineer of his day, Isambard Kingdom Brunel of the Great Western, threw down the gauntlet in the struggle over whether to standardize the railway gauge at 4' 8 1/2" or let it expand to the GW's 7 feet. He suggested trials over broad gauge and standard-gauge track between London and Exeter.

Although drawings for the Great A were prepared before Brunel's challenge, it seemed logical to assume that she was built to compete in these trials against the Firefly-class Ixion. The A was a modification of the 2-2-2 longboiler type, which had been criticized as having dangerous riding qualities over 45 mph. So Stephenson rearranged the three axles, putting the driver back just ahead of the overhanging firebox. The two carrying axles forward were independent of each other and had the cylinders between them.

Maclean's 1922 book reported that W G Brown of York, "whose knowledge of the early NER engines is as reliable as it is extensive ...knew the Great A well, and as a boy moved it in steam. John Pattison, its fireman, told him it could do 90 miles an hours [145 kph] on the easy ground between Belford and Beal on the main line."

Most observers agree, however, that the Great A wasn't a success. Riding qualties were still daunting. Reder reports that Daniel Gooch's trip on the Great A's footplate led him to dissuade Brunel from also taking a ride on the engine. Of course, since the Great A ran on the standard gauge and Gooch was the pre-eminent broad gauge locomotive designer, the objectivity of his judgement cannot be guaranteed. Even so, few successors employing this layout were built.

Principal Dimensions by Steve Llanso of Sweat House Media

ClassGreat A
Locobase ID3030
RailroadYork & North Midland
CountryGreat Britain
Number in Class1
Road Numbers38
Number Built1
BuilderRobert Stephenson & Co
Valve Gear
Locomotive Length and Weight
Driver Wheelbase (ft / m)
Engine Wheelbase (ft / m)12 / 3.66
Ratio of driving wheelbase to overall engine wheelbase
Overall Wheelbase (engine & tender) (ft / m)
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)
Engine Weight (lbs / kg)51,296 / 23,268
Tender Loaded Weight (lbs / kg)13,664 / 6198
Total Engine and Tender Weight (lbs / kg)64,960 / 29,466
Tender Water Capacity (gals / ML)
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)
Minimum weight of rail (calculated) (lb/yd / kg/m)
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)79 / 2007
Boiler Pressure (psi / kPa)90 / 6.20
High Pressure Cylinders (dia x stroke) (in / mm)15" x 24" / 381x610
Tractive Effort (lbs / kg)5229 / 2371.84
Factor of Adhesion (Weight on Drivers/Tractive Effort)
Heating Ability
Tubes (number - dia) (in / mm)139 - 1.75" / 44
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)13.50 / 4.11
Firebox Area (sq ft / m2)59 / 5.48
Grate Area (sq ft / m2) 9.25 / 0.86
Evaporative Heating Surface (sq ft / m2)939 / 87.24
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)939 / 87.24
Evaporative Heating Surface/Cylinder Volume191.29
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation833
Same as above plus superheater percentage833
Same as above but substitute firebox area for grate area5310
Power L12979
Power MT

All material Copyright © SteamLocomotive.com
Wes Barris