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The reference for locomotives and railcars

North Eastern and London & North Eastern Raven class A2

Great Britain 1922 5 produced
No. 2400 „City of Newcastle“ at King's Cross flickr/stratfordman72

The A2 was a Pacific express locomotive designed by Vincent Raven for the North Eastern Railway shortly before the grouping into the LNER. It was based on the class Z Atlantic with an additional driving axle and a longer boiler with a wide firebox. At six feet, the diameter of the boiler was the biggest in Britain, together with Gresley's GNR class H4, the later LNER class K3. Two were built in 1922 at Darlington of which only the first one was actually steamed up before the grouping. Three others followed in 1924 which were directly delivered to the LNER.

At the same time, Gresley had designed his A1 Pacific for the Great Northern. Direct comparisons between both classes showed that the A1 was more powerful and technically more advanced in general. Additionally, the A2 had a longer wheelbase, what possibly limited the suitability for some lines. Ultimately, as Raven reached his retirement age and Gresley became the chief mechanical engineer of the grouped LNER, his A1 was chosen as the new standard express locomotive.

The five A2 locomotives were numbered 2400 to 2404 and named after cities. In 1929, Gresley rebuilt 2404 with a taper boiler that had a reduced pressure of only 180 instead of 200 psi. As this did not deliver considerably more power, no others were rebuilt. When they needed repairs in the thirties, it was decided to rely on the greater number of A1 locomotives. So all five A2 were withdrawn and scrapped in 1936 and 1937.

Technical data

General

Built
1922, 1924
Manufacturers
Darlington
Wheel arrangement
4-6-2 (Pacific)
Gauge
1,435 mm (Standard gauge)

Dimensions and weights

Wheelbase
11.33 m
Total wheelbase
18.90 m
Service mass
98.6 t
Adhesion mass
61 t
Total mass
142.3 t
Rigid wheelbase
4.57 m
Axle load
20.3 t
Water capacity
18,753 l
Fuel capacity
5.6 t (coal)

Boiler

Grate area
3.855 m²
Firebox surface
19.603 m²
Tube heating surface
205.409 m²
Evaporative heating surface
225.011 m²
Superheater surface
64.753 m²
Total heating surface
289.8 m²

Power plant

Driver diameter
2,032 mm
Boiler pressure
13.8 bar
Expansion type
simple expansion
Cylinders
three, 483 x 660 mm

Power

Power source
steam
Estimated power
1,641 kW (2,231 PS)
Starting effort
133.1 kN

Calculated values

Factor of adhesion
1 : 4.49
Optimal speed
76 km/h
Power-to-weight ratio
16.7 kW/t
Heating Surface Equivalent
452.5 m²
Cylinder volume/HSE
1 : 800.83
Adhesive weight/Total
1 : 1.62
Tractive force/Heating surface
1 : 9.59
Grate area/Heating surface
1 : 75.17
Firebox/Tube surface
1 : 10.48
Total/Superheater
1 : 3.47
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