Great Central class 9N
London & North Eastern class A5
Robinson developed these heavy 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 The rest were withdrawn between 1957 and 1960.
Technical data
General
| Property | A5/1 | A5/2 |
|---|---|---|
| Built | 1911-1917 | 1923-1926 |
| Manufacturers | Gorton | Hawthorn, Leslie & Co. |
| Wheel arrangement | 4-6-2T (Pacific) | |
| Gauge | 1,435 mm (Standard gauge) | |
Dimensions and weights
| Property | A5/1 | A5/2 |
|---|---|---|
| Length | 13.10 m | |
| Wheelbase | 9.98 m | |
| Service mass | 84.3 t | 87.4 t |
| Adhesion mass | 54.9 t | |
| Rigid wheelbase | 3.96 m | |
| Axle load | 19 t | |
| Water capacity | 10,364 l | |
| Fuel capacity | 4.2 t (coal) | |
Boiler
| Property | A5/1 | A5/2 |
|---|---|---|
| Grate area | 1.951 m² | |
| Firebox surface | 13.099 m² | 13.127 m² |
| Tube heating surface | 120.217 m² | 105.789 m² |
| Evaporative heating surface | 133.316 m² | 118.916 m² |
| Superheater surface | 19.881 m² | 16.537 m² |
| Total heating surface | 153.2 m² | 135.5 m² |
Power plant
| Property | A5/1 | A5/2 |
|---|---|---|
| Driver diameter | 1,702 mm | |
| Boiler pressure | 11 bar | |
| Expansion type | simple expansion | |
| Cylinders | two, 508 x 660 mm | |
Power
| Property | A5/1 | A5/2 |
|---|---|---|
| Power source | steam | |
| Estimated power | 727 kW (988 PS) | 690 kW (938 PS) |
| Starting effort | 93.9 kN | |
Calculated values
| Property | A5/1 | A5/2 |
|---|---|---|
| Factor of adhesion | 1 : 5.73 | |
| Optimal speed | 47 km/h | 45 km/h |
| Power-to-weight ratio | 8.6 kW/t | 7.9 kW/t |
| Heating Surface Equivalent | 238.6 m² | 217.6 m² |
| Cylinder volume/HSE | 1 : 1,122.10 | 1 : 1,230.11 |
| Adhesive weight/Total | 1 : 1.54 | 1 : 1.59 |
| Tractive force/Heating surface | 1 : 12.80 | 1 : 14.48 |
| Grate area/Heating surface | 1 : 78.52 | 1 : 69.43 |
| Firebox/Tube surface | 1 : 9.18 | 1 : 8.06 |
| Total/Superheater | 1 : 6.71 | 1 : 7.19 |
