Great Western Railway class 4700
The class 4700 was a mixed traffic 2-8-0 with large drivers designed by George Jackson Churchward. These locomotives were commonly known as “Night Owls”, since they were mostly used for fast, long distance overnight freight services. The boiler was larger than that of the Castle class. Like most GWR locomotives of the time, they had a Belpaire firebox. Their superheater either had four or six elements and a surface of 211.2 or 276.98 square feet.
Swindon built No. 4700 in 1919 and only eight others followed in 1922 and 1923. Sometimes the GWR also used them for very heavy passenger trains during holiday times. From 1957, British Railways frequently used some class members for Saturday relief passenger services in the summer months. The whole class was withdrawn and scrapped between 1962 and 1964. The Great Western Society is constructing the tenth class member from parts of several other locomotives that will be numbered 4709. Lately there are not many news about their progress.
Technical data
General
- Built
- 1919, 1922-1923
- Manufacturers
- Swindon
- Wheel arrangement
- 2-8-0 (Consolidation)
- Gauge
- 1,435 mm (Standard gauge)
Dimensions and weights
- Length
- 20.23 m
- Wheelbase
- 8.92 m
- Total wheelbase
- 17.32 m
- Service mass
- 83.3 t
- Adhesion mass
- 74.6 t
- Total mass
- 130.8 t
- Rigid wheelbase
- 6.10 m
- Axle load
- 19.9 t
- Water capacity
- 18,185 l
Boiler
- Grate area
- 2.813 m²
- Firebox surface
- 15.77 m²
- Tube heating surface
- 191.599 m²
- Evaporative heating surface
- 207.369 m²
- Superheater surface
- 25.732 m²
- Total heating surface
- 233.1 m²
Power plant
- Driver diameter
- 1,727 mm
- Boiler pressure
- 15.5 bar
- Expansion type
- simple expansion
- Cylinders
- two, 483 x 762 mm
Power
- Power source
- steam
- Estimated power
- 1,268 kW
- Starting effort
- 135.5 kN
Calculated values
- Factor of adhesion
- 1 : 5.40
- Optimal speed
- 58 km/h
- Power-to-weight ratio
- 15.2 kW/t
- Heating Surface Equivalent
- 337.7 m²
- Cylinder volume/HSE
- 1 : 825.54
- Adhesive weight/Total
- 1 : 1.12
- Tractive force/Heating surface
- 1 : 12.14
- Grate area/Heating surface
- 1 : 82.87
- Firebox/Tube surface
- 1 : 12.15
- Total/Superheater
- 1 : 8.06