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London & North Western No. 3020 “Cornwall”

Great Britain 1847 1 produced
“Cornwall” after the rebuilding of 1858 Stadtarchiv Mainz / BPSF/9850 A PD

In an attempt to combine large driving wheels with a low center of gravity, No. 3020 “Cornwall” of the LNWR was one of the most complicated, but unsuccessful designs. Designed by Francis Trevithick, son of the famous Richard Trevithick, it was a 4-2-2 with driving wheels of 8 ft 6 in (2,591 mm) built in 1847. To keep the boiler low, but out of the way of the driving axle, it was placed below this axle.

Even though the driving axle could be held out of the boiler, the trailing axle went through a tube in the firebox, what created some problems when assembling the locomotive. Another problem was the long rigid wheelbase that effected the running characteristics. For these reasons, John Ramsbottom rebuilt it into a conventional 2-2-2 with boiler above the driving axle. 

Although it was only a single locomotive, the rebuilt “Cornwall” was used successfully in express service. With light trains, it delivered average speeds of 50 mph (80 km/h) and top speeds of up to 70 mph (113 km/h). In the 1870s, it got a semi-open cab.

It remained in regular express service until 1902. After that, it was not retired, but used as an inspection locomotive. For this task, it got a six-wheel carriage whose front part filled the task of a tender, while its rear part was a passenger compartment. When it reached its final retirement in the twenties, it was one of the first locomotives to be preserved on purpose. Today it can be found in the Buckinghamshire Railway Centre.

Original state from 1847 with a low boiler PD
Sectional frawing of the original state PD

Technical data

General

Built
1847
Manufacturers
Crewe
Wheel arrangement
2-2-2 (Jenny Lind)
Gauge
1,435 mm (Standard gauge)

Dimensions and weights

Wheelbase
4.52 m
Service mass
28.8 t
Adhesion mass
12.7 t
Rigid wheelbase
4.52 m
Axle load
12.7 t
Water capacity
8,184 l

Boiler

Grate area
1.394 m²
Firebox surface
4.738 m²
Tube heating surface
94.482 m²
Evaporative heating surface
99.221 m²
Total heating surface
99.2 m²

Power plant

Driver diameter
2,591 mm
Boiler pressure
9.7 bar
Expansion type
simple expansion
Cylinders
two, 438 x 610 mm

Power

Power source
steam
Estimated power
149 kW (203 PS)
Top speed
113 km/h
Starting effort
37.1 kN

Calculated values

Factor of adhesion
1 : 3.36
Optimal speed
24 km/h
Power-to-weight ratio
5.2 kW/t
Heating Surface Equivalent
122.9 m²
Cylinder volume/HSE
1 : 1,495.63
Adhesive weight/Total
1 : 2.26
Tractive force/Heating surface
1 : 7.80
Grate area/Heating surface
1 : 71.18
Firebox/Tube surface
1 : 19.94
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