South African class GG
South Africa 1925 1 produced
The sole member of the SAR class GG was a Double Prairie Garratt built for fast passenger service in the Touws River area. For this task it had the largest drivers yet seen on a Garratt in South Africa with 57 inches or 1,448 mm. A coal pusher was installed in the tender to ease the work of the fireman. It could reach a speed of 57 mph or 92 km/h, but at speed its running was somewhat unsteady due to the single leading axle. So it had to give way to 4-8-2 locomotives and was usually only used for slower passenger and freight trains. On an incline of 1 in 80 (1.25%) it could haul 1,245 tons, what was reduced to 340 tons on 1 in 40 (2.5%). It was withdrawn from active service in 1938 and scrapped nine years later.
Technical data
General
- Built
- 1925
- Manufacturers
- Beyer, Peacock & Co.
- Wheel arrangement
- 2-6-2+2-6-2T (Double Prairie (Garratt))
- Gauge
- 1,067 mm (Cape gauge)
Dimensions and weights
- Wheelbase
- 20.52 m
- Service mass
- 150.1 t
- Adhesion mass
- 96 t
- Rigid wheelbase
- 3.05 m
- Axle load
- 16.5 t
- Water capacity
- 20,911 l
- Fuel capacity
- 10.2 t (coal)
Boiler
- Grate area
- 4.831 m²
- Firebox surface
- 19.51 m²
- Tube heating surface
- 219.809 m²
- Evaporative heating surface
- 239.318 m²
- Superheater surface
- 36.232 m²
- Total heating surface
- 275.6 m²
Power plant
- Driver diameter
- 1,448 mm
- Boiler pressure
- 12.4 bar
- Expansion type
- simple expansion
- Cylinders
- four, 457 x 660 mm
Power
- Power source
- steam
- Estimated power
- 1,268 kW (1,724 PS)
- Top speed
- 92 km/h
- Starting effort
- 201.2 kN
Calculated values
- Factor of adhesion
- 1 : 4.68
- Optimal speed
- 39 km/h
- Power-to-weight ratio
- 8.4 kW/t
- Heating Surface Equivalent
- 409.3 m²
- Cylinder volume/HSE
- 1 : 1,059.48
- Adhesive weight/Total
- 1 : 1.56
- Tractive force/Heating surface
- 1 : 15.25
- Grate area/Heating surface
- 1 : 57.04
- Firebox/Tube surface
- 1 : 11.27
- Total/Superheater
- 1 : 6.61
