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The reference for locomotives and railcars

Great Western Railway class 4700

Great Britain 1919 9 produced
No. 4705 in November 1962 at Southall Locomotive Depot Ben Brooksbank CC BY-SA 2.0

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 The whole class was withdrawn and scrapped between 1962 and 1964.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.

Schematic drawing Locomotive Magazine, June 1919

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
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