South African class 19A
Since the axle load of the SAR class 19 was still too high for some branch lines, Col F.R. Collins designed the lighter class 19A. Changes included a smaller boiler, a cylinder diameter of 19.5 instead of 21 inches and a driver diameter of 51 instead of 54 inches. In total, this made a weight saving of four tons. Additionally, the axle load could be changed by setting of a pin in the suspension of the trailing axle.
36 were built in 1929 by the Swiss SLM. As early as in the middle of the thirties, five got a standard boiler developed by A.G. Watson and were designated class 19AR. Two of these got domeless boilers. The SAR used the classes 19A and 19AR until 1977. After this, a few were sold for industrial service. Three 19 and two 19A have been preserved.
Technical data
General
| Property | as built | rebuilt 19AR |
|---|---|---|
| Built | 1929 | 1935 |
| Manufacturers | SLM | |
| Wheel arrangement | 4-8-2 (Mountain) | |
| Gauge | 1,067 mm (Cape gauge) | |
Dimensions and weights
| Property | as built | rebuilt 19AR |
|---|---|---|
| Wheelbase | 9.80 m | |
| Total wheelbase | 17.86 m | |
| Service mass | 76.4 t | 77.3 t |
| Adhesion mass | 52.5 t | 52 t |
| Total mass | 128.1 t | 129.1 t |
| Rigid wheelbase | 4.39 m | |
| Axle load | 13.4 t | 13 t |
| Water capacity | 19,321 l | |
| Fuel capacity | 9.1 t (coal) | |
Boiler
| Property | as built | rebuilt 19AR |
|---|---|---|
| Grate area | 3.345 m² | |
| Firebox surface | 13.006 m² | 12.914 m² |
| Tube heating surface | 141.863 m² | 157.935 m² |
| Evaporative heating surface | 154.87 m² | 170.849 m² |
| Superheater surface | 38.555 m² | 37.533 m² |
| Total heating surface | 193.4 m² | 208.4 m² |
Power plant
| Property | as built | rebuilt 19AR |
|---|---|---|
| Driver diameter | 1,295 mm | |
| Boiler pressure | 13.8 bar | |
| Expansion type | simple expansion | |
| Cylinders | two, 495 x 660 mm | |
Power
| Property | as built | rebuilt 19AR |
|---|---|---|
| Power source | steam | |
| Estimated power | 969 kW (1,317 PS) | |
| Starting effort | 146.6 kN | |
Calculated values
| Property | as built | rebuilt 19AR |
|---|---|---|
| Factor of adhesion | 1 : 3.51 | 1 : 3.48 |
| Optimal speed | 40 km/h | |
| Power-to-weight ratio | 12.7 kW/t | 12.5 kW/t |
| Heating Surface Equivalent | 297.0 m² | 310.5 m² |
| Cylinder volume/HSE | 1 : 856.83 | 1 : 819.64 |
| Adhesive weight/Total | 1 : 1.45 | 1 : 1.49 |
| Tractive force/Heating surface | 1 : 15.83 | 1 : 14.69 |
| Grate area/Heating surface | 1 : 57.83 | 1 : 62.30 |
| Firebox/Tube surface | 1 : 10.91 | 1 : 12.23 |
| Total/Superheater | 1 : 4.02 | 1 : 4.55 |
