loco-info.com - Great Central class 9N

Robinson developed these heavy GCR class 9N tank locomotives for fast suburban traffic. With a driving wheel diameter of 5 feet and 7 inches or 1,702 mm and three coupled axles, they were also able to achieve good acceleration. Otherwise they were state-of-the-art with piston valves and superheaters. Between 1910 and 1917, 21 locomotives were built in GCR's Gorton works.

The second production lot was delayed until after the First World War. In 1923, ten more were built with adjustments by Gresley, including a smaller heating surface. These were now being built by Hawthorn, Leslie & Co. as were the next 13 in 1925 and 1926.

The previous class 9N became the A5 at the LNER. In order to be able to distinguish the first and second series, these became the A5/1 and A5/2. British Railways took over 43 of 44 locomotives. The rest were retired between 1957 and 1960.

Variant	A5/1	A5/2

General
Built	1911-1917	1923-1926
Manufacturer	Gorton	Hawthorn, Leslie & Co.
Axle config	4-6-2T (Pacific)
Gauge	4 ft 8 1/2 in (Standard gauge)

Dimensions and Weights
Length	42 ft 11 7/8 in
Wheelbase	32 ft 9 in
Rigid wheelbase	13 ft
Service weight	185,920 lbs	192,640 lbs
Adhesive weight	120,960 lbs
Axle load	41,840 lbs
Water capacity	2,738 us gal
Fuel capacity	9,296 lbs (coal)

Boiler
Grate area	21 sq ft
Firebox area	141 sq ft	141.3 sq ft
Tube heating area	1,294 sq ft	1,138.7 sq ft
Evaporative heating area	1,435 sq ft	1,280 sq ft
Superheater area	214 sq ft	178 sq ft
Total heating area	1,649 sq ft	1,458 sq ft

Variant	A5/1	A5/2

Power Plant
Driver diameter	67 in
Boiler pressure	160 psi
Expansion type	simple
Cylinders	two, 20 x 26 in

Power
Power source	steam
Estimated power	975 hp (727 kW)	925 hp (690 kW)
Optimal speed	29 mph	28 mph
Starting effort	21,110 lbf

Calculated Values
Factor of adhesion	1 : 5.73
Power-to-weight ratio	0.0052 hp/lb	0.0048 hp/lb
Heating Area Equivalent	2,568 sq ft	2,342.5 sq ft
Cylinder volume/HAE	1 : 1122.10	1 : 1230.11
Adhesive weight/Total	1 : 1.54	1 : 1.59
Tractive force/Heating area	1 : 2877.94	1 : 3254.94
Grate area/Heating area	1 : 71.81	1 : 62.70
Firebox/Tube area	1 : 10.70	1 : 9.32
Total/Superheater	1 : 6.71	1 : 7.19

steam locomotive

passenger

tank locomotive

John George Robinson

Herbert Nigel Gresley

last changed: 03/2023

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