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South African class 21
In the late thirties A.G. Watson designed a heavy mixed-traffic locomotive that had to be limited to an axle load of 15 tons. As he had an aversion against articulated locomotives, it had to have five driving axles an...
General
| Property | South African class 21Remove |
|---|---|
| Built | 1937 |
| Manufacturers | North British |
| Wheel arrangement | 2-10-4 (Texas) |
| Gauge | 1,067 mm (Cape gauge) |
Dimensions and weights
| Property | South African class 21Remove |
|---|---|
| Length | 23.42 m |
| Wheelbase | 11.20 m |
| Rigid wheelbase | 5.72 m |
| Total wheelbase | 20.83 m |
| Service weight | 108.3 t |
| Adhesive weight | 74 t |
| Axle load | 15.2 t |
| Total weight | 175.2 t |
| Water capacity | 25,400 l |
| Fuel capacity | 10.2 t (coal) |
Boiler
| Property | South African class 21Remove |
|---|---|
| Grate area | 5.853 m² |
| Firebox surface | 21.554 m² |
| Tube heating surface | 294.317 m² |
| Evaporative heating surface | 315.871 m² |
| Superheater surface | 62.803 m² |
| Total heating surface | 378.7 m² |
Power plant
| Property | South African class 21Remove |
|---|---|
| Driver diameter | 1,372 mm |
| Boiler pressure | 14.5 bar |
| Expansion type | simple expansion |
| Cylinders | two, 610 x 660 mm |
Power
| Property | South African class 21Remove |
|---|---|
| Power source | steam |
| Estimated power | 1,864 kW (2,534 PS) |
| Starting effort | 220.2 kN |
Calculated values
| Property | South African class 21Remove |
|---|---|
| Factor of adhesion | 1 : 3.30 |
| Optimal speed | 51 km/h |
| Power-to-weight ratio | 17.2 kW/t |
| Heating Surface Equivalent | 549.2 m² |
| Cylinder volume/HSE | 1 : 701.86 |
| Adhesive weight/Total | 1 : 1.46 |
| Tractive force/Heating surface | 1 : 12.15 |
| Grate area/Heating surface | 1 : 64.70 |
| Firebox/Tube surface | 1 : 13.65 |
| Total/Superheater | 1 : 5.03 |
