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The reference for locomotives and railcars

Great Western Railway Caesar class

originally Pyracmon, Ariadne and Caliph classes

Great Britain 1851 117 produced
“Liffey” from the Ariadne class Locomotive Magazine, December 1913

Today, more than 100 GWR broad gauge freight locomotives, which originally belonged to different classes, are called the Caesar class. They all had the 0-6-0 wheel arrangement and were designed by Daniel Gooch and built in Swindon. In contrast to their predecessors, they did not have a haystack firebox, but one with a round top.

Using the possibilities of the broad gauge, they were significantly more powerful than other locomotives with this wheel arrangement. Due to the gentle curves of the broad-gauge tracks, the wheelbase could be made very long in order to obtain sufficient running smoothness despite the lack of carrying axles. At five feet in diameter, the wheels were smaller than the boiler diameter.

The actual Caesar class consisted of eight saddle tank locomotives built in 1851 and 1852. Their service life ended between 1871 and 1880. A restructuring of the class names in 1865 resulted in the Pyracmon, Ariadne and Caliph class tender locomotives being included in the Caesar class.

The seven Pyracmon class locomotives were based on the Premier class, which were the first locomotives built in Swindon and were withdrawn between 1871 and 1873. The Ariadne and Caliph classes were also referred to as “Gooch Standard Goods” and were delivered in seven lots between 1852 and 1863.

Most locomotives were named after gods or well-known figures from ancient Greece, but some were named after British rivers or given other names altogether. This resulted in 102 locomotives which were withdrawn between 1871 and 1883. An exception was the “Europa”, which was extensively rebuilt in 1869 and remained in service until 1892, when traffic on the broad gauge was discontinued.

Schematic drawing of “Cato” Locomotive Magazine, April 1902

Technical data

General

Property Caesar Pyracmon Ariadne, Caliph
Built 1851-1852 1847-1849 1852-1863
Manufacturers Swindon
Wheel arrangement 0-6-0ST (Six-coupled) 0-6-0 (Six-coupled)
Gauge 2,140 mm (GWR broad gauge)

Dimensions and weights

Property Caesar Pyracmon Ariadne, Caliph
Service mass 33 t 28.6 t 31.6 t
Adhesion mass 33 t 28.6 t 31.6 t
Axle load 11.9 t 10.3 t 12.4 t
Wheelbase 4.67 m 4.94 m
Rigid wheelbase 4.67 m 4.94 m

Boiler

Property Caesar Pyracmon Ariadne, Caliph
Grate area 1.61 m² 1.713 m² 1.784 m²
Firebox surface 10.008 m² 11.272 m² 12.059 m²
Tube heating surface 116.619 m² 115.355 m² 134.171 m²
Evaporative heating surface 126.627 m² 146.23 m²
Total heating surface 126.6 m² 146.2 m²

Power plant

Property Caesar Pyracmon Ariadne, Caliph
Driver diameter 1,448 mm 1,524 mm
Boiler pressure 8.3 bar 7.9 bar 8.3 bar
Expansion type simple expansion
Cylinders two, 432 x 610 mm two, 406 x 610 mm two, 432 x 610 mm

Power

Property Caesar Pyracmon Ariadne, Caliph
Power source steam
Estimated power 261 kW (355 PS) 298 kW (405 PS) 336 kW (457 PS)
Starting effort 55.2 kN 44.5 kN 52.4 kN

Calculated values

Property Caesar Pyracmon Ariadne, Caliph
Factor of adhesion 1 : 5.86 1 : 6.30 1 : 5.91
Optimal speed 29 km/h 40 km/h 39 km/h
Power-to-weight ratio 7.9 kW/t 10.4 kW/t 10.6 kW/t
Heating Surface Equivalent 176.7 m² 183.0 m² 206.5 m²
Cylinder volume/HSE 1 : 1,010.59 1 : 864.28 1 : 864.49
Adhesive weight/Total 1 : 1.00
Tractive force/Heating surface 1 : 9.11 1 : 7.34 1 : 7.49
Grate area/Heating surface 1 : 78.65 1 : 73.92 1 : 81.97
Firebox/Tube surface 1 : 11.65 1 : 10.23 1 : 11.13
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