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The reference for locomotives and railcars

Great Western Railway class 3700 “City”

Great Britain 1902 20 produced
No. 3440 “City of Truro” at Railfest 2012 in York Tony Hisgett / City of Truro Railfest 2012 CC BY 2.0

In 1902, the GWR rebuilt a 4-4-0 Atbara class locomotive with a new domeless taper boiler with Belpaire firebox. This was No. 3405 “Mauritius”, which now served as a prototype for the new City class. Ten more of this type were built in 1903 with numbers 3433 to 3442. In 1907 and 1908, nine more Atbaras were rebuilt, bringing the number of the City class to 20. Soon they were given the numbers 3700 to 3719.

No. 3440 “City of Truro”, which later became 3717 and is considered the first steam locomotive to actually reach 100 mph or 161 km/h, achieved greater fame. This happened on the ninth of May 1904 on the Wellington Bank in Somerset, which had a gradient of 1 in 90. However, due to the inaccuracies of the measurement methods at the time, it is still not entirely clear whether the speed achieved was up to 102.3 or even just 99 mph. 

Between 1910 and 1912 all members of the City class received a superheater. Further modifications carried out over the years included the boiler feed, chimney, valves, a steam reverser and a different bogie. All were withdrawn between October 1927 and May 1931. Due to its history, the “City of Truro” is the only one that has been preserved and is now no longer operational.

Technical data

General

Property as built superheated
Built 1902-1909 1910
Manufacturers Swindon
Wheel arrangement 4-4-0 (American)
Gauge 1,435 mm (Standard gauge)

Dimensions and weights

Property as built superheated
Wheelbase 6.55 m
Service mass 56.2 t
Adhesion mass 36.7 t
Total mass 93.5 t
Rigid wheelbase 2.59 m
Axle load 18.6 t
Water capacity 16,364 l
Fuel capacity 5.1 t (coal)

Boiler

Property as built superheated
Grate area 1.91 m²
Firebox surface 11.919 m² 11.958 m²
Tube heating surface 150.661 m² 125.352 m²
Evaporative heating surface 162.58 m² 137.311 m²
Total heating surface 162.6 m² 155.1 m²
Superheater surface 17.837 m²

Power plant

Property as built superheated
Driver diameter 2,045 mm
Boiler pressure 13.4 bar
Expansion type simple expansion
Cylinders two, 457 x 660 mm

Power

Property as built superheated
Power source steam
Estimated power 634 kW (862 PS) 783 kW (1,065 PS)
Starting effort 77.2 kN

Calculated values

Property as built superheated
Factor of adhesion 1 : 4.66
Optimal speed 50 km/h 63 km/h
Power-to-weight ratio 11.3 kW/t 13.9 kW/t
Heating Surface Equivalent 222.2 m² 232.8 m²
Cylinder volume/HSE 1 : 975.99 1 : 931.55
Adhesive weight/Total 1 : 1.53
Tractive force/Heating surface 1 : 9.91 1 : 10.39
Grate area/Heating surface 1 : 85.12 1 : 81.23
Firebox/Tube surface 1 : 12.64 1 : 10.48
Total/Superheater 1 : 7.70

Topics

  • steam locomotive
  • express
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Last changed: 12/2023

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