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The reference for locomotives and railcars

Central South African class 11

South African class 11

South Africa 1904 36 produced
SAR Museum / Terry Rowe collection

The class 11 designated 36 2-8-2 locomotives built by North British in 1904. They were designed by P.A. Hyde for freight service on newly upgraded lines with heavier tracks of 80 pounds per yard. It was a modern design with a superheated boiler and had many common parts with the class 10 Pacific. The Belpaire firebox was placed behind the last driving axle and supported by the trailing axle. The second and third driving axles had flangeless wheels to ensure better curve negotiation.

After their delivery, some had to be stored for some time to wait for the upgrade of more lines so that these could carry their axle load of 15.75 tons. When the South African Railways were founded, they were still designated class 11. On the Witbank line, they initially hauled trains of 1,050 tons. Later this was reduced to 900 tons to increase the average speed. It soon showed that the low load of 6 tons and 1 cwt on the leading axle led to bad running characteristics at high speeds.

After more powerful Garratts took over heavy freight service, the Mikados were used for local and shunting service. Unlike many other South African steam locomotives, they never received Watson standard boilers. The last ones were withdrawn from SAR service in 1975, after 71 years. Now 15 were sold for industrial work, most of them to gold mines. Some of these worked until the turn of the millennium when they reached an age of nearly 100 years.

Technical data

General

Built
1904
Manufacturers
North British
Wheel arrangement
2-8-2 (Mikado)
Gauge
1,067 mm (Cape gauge)

Dimensions and weights

Length
19.62 m
Wheelbase
8.92 m
Total wheelbase
16.97 m
Service mass
81 t
Adhesion mass
63.3 t
Total mass
131.1 t
Rigid wheelbase
4.00 m
Axle load
16 t
Water capacity
18,185 l
Fuel capacity
10.2 t (coal)

Boiler

Grate area
3.437 m²
Firebox surface
13.192 m²
Tube heating surface
169.92 m²
Evaporative heating surface
183.112 m²
Superheater surface
30.751 m²
Total heating surface
213.9 m²

Power plant

Driver diameter
1,219 mm
Boiler pressure
13.1 bar
Expansion type
simple expansion
Cylinders
two, 508 x 660 mm

Power

Power source
steam
Estimated power
858 kW (1,167 PS)
Starting effort
155.7 kN

Calculated values

Factor of adhesion
1 : 3.99
Optimal speed
34 km/h
Power-to-weight ratio
10.6 kW/t
Heating Surface Equivalent
310.6 m²
Cylinder volume/HSE
1 : 861.96
Adhesive weight/Total
1 : 1.28
Tractive force/Heating surface
1 : 15.20
Grate area/Heating surface
1 : 62.22
Firebox/Tube surface
1 : 12.88
Total/Superheater
1 : 5.95
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