London & North Western No. 3020 “Cornwall”
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.
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