South African Class 19A 4-8-2

South African Class 19A & 19AR 4-8-2
Class 19A no. 685 at De Aar, 16 October 1978
Type and origin ♠ Class 19A as built with a round-topped firebox ♥ Class 19AR rebuilt with a Watson Standard boiler Power type Steam Designer South African Railways (Col F.R. Collins DSO) Builder Swiss Locomotive and Machine Serial number 3300-3335 Model Class 19A Build date 1929 Total produced 36
Specifications Configuration: ​  • Whyte 4-8-2 (Mountain)  • UIC 2'D1'h2 Driver 2nd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 28 1⁄2 in (724 mm) Coupled dia. 51 in (1,295 mm) Trailing dia. 33 in (838 mm) Tender wheels 34 in (864 mm) Wheelbase 58 ft 7 5⁄8 in (17,872 mm)  • Engine 32 ft 2 in (9,804 mm)  • Leading 6 ft 2 in (1,880 mm)  • Coupled 14 ft 5 in (4,394 mm)  • Tender 16 ft 9 in (5,105 mm)  • Tender bogie 4 ft 7 in (1,397 mm) Wheel spacing (Asymmetrical) 1-2: 4 ft 10 in (1,473 mm) 2-3: 4 ft 9 in (1,448 mm) 3-4: 4 ft 10 in (1,473 mm) Length: ​  • Over couplers 67 ft 6 in (20,574 mm) Height ♠ 12 ft 10 7⁄8 in (3,934 mm) ♥ 12 ft 11 7⁄8 in (3,959 mm) Frame type Bar Axle load ♠ 13 LT 4 cwt (13,410 kg) ♥ 13 LT 1 cwt (13,260 kg)  • Leading ♠ 13 LT 12 cwt (13,820 kg) ♥ 13 LT 12 cwt (13,820 kg)  • 1st coupled ♠ 12 LT 17 cwt (13,060 kg) ♥ 12 LT 15 cwt (12,950 kg)  • 2nd coupled ♠ 13 LT 4 cwt (13,410 kg) ♥ 13 LT 1 cwt (13,260 kg)  • 3rd coupled ♠ 12 LT 17 cwt (13,060 kg) ♥ 12 LT 15 cwt (12,950 kg)  • 4th coupled ♠ 12 LT 15 cwt (12,950 kg) ♥ 12 LT 12 cwt (12,800 kg)  • Trailing ♠ 9 LT 18 cwt (10,060 kg) ♥ 11 LT 7 cwt (11,530 kg)  • Tender bogie Bogie 1: 25 LT 15 cwt (26,160 kg) Bogie 2: 25 LT 4 cwt (25,600 kg)  • Tender axle 12 LT 17 cwt 2 qtr (13,080 kg) Adhesive weight ♠ 51 LT 13 cwt (52,480 kg) ♥ 51 LT 3 cwt (51,970 kg) Loco weight ♠ 75 LT 3 cwt (76,360 kg) ♥ 76 LT 2 cwt (77,320 kg) Tender weight 50 LT 19 cwt (51,770 kg) Total weight ♠ 126 LT 2 cwt (128,100 kg) ♥ 127 LT 1 cwt (129,100 kg) Tender type MP (2-axle bogies) MP, MP1, MR, MS, MX, MY, MY1 permitted Fuel type Coal Fuel capacity 9 LT 4 cwt (9.3 t) Water cap 4,250 imp gal (19,300 l) Firebox type Round-top  • Firegrate area 36 sq ft (3.3 m2) Boiler: ​  • Model Watson Standard no. 1A  • Pitch ♠ 8 ft (2,438 mm) ♥ 8 ft 1 in (2,464 mm)  • Diameter ♠ 4 ft 10 1⁄4 in (1,480 mm) ♥ 5 ft (1,524 mm)  • Tube plates ♠ 20 ft 3⁄8 in (6,106 mm) ♥ 20 ft 2 in (6,147 mm)  • Small tubes ♠ 86: 2 1⁄4 in (57 mm) ♥ 76: 2 1⁄2 in (64 mm)  • Large tubes ♠ 18: 5 1⁄2 in (140 mm) ♥ 24: 5 1⁄2 in (140 mm) Boiler pressure 200 psi (1,379 kPa) Safety valve Pop Heating surface ♠ 1,667 sq ft (154.9 m2) ♥ 1,839 sq ft (170.8 m2)  • Tubes ♠ 1,527 sq ft (141.9 m2) ♥ 1,700 sq ft (160 m2)  • Arch tubes ♠ 15 sq ft (1.4 m2) ♥ 16 sq ft (1.5 m2)  • Firebox ♠ 125 sq ft (11.6 m2) ♥ 123 sq ft (11.4 m2) Superheater: ​  • Heating area ♠ 415 sq ft (38.6 m2) ♥ 404 sq ft (37.5 m2) Cylinders Two Cylinder size 19 1⁄2 in (495 mm) bore 26 in (660 mm) stroke Valve gear Walschaerts Valve type Piston Couplers AAR knuckle
Performance figures Tractive effort ♠♥ 29,080 lbf (129.4 kN) @ 75%
Career Operators South African Railways Class Class 19A, 19AR Number in class 36 Numbers 675-710 Delivered 1929 First run 1929 Withdrawn c. 1977
The leading coupled axle had flangeless wheels

The South African Railways Class 19A 4-8-2 of 1929 was a steam locomotive.

In 1929, the South African Railways placed 36 Class 19A steam locomotives with a 4-8-2 Mountain type wheel arrangement in service. Five of them were later reboilered and reclassified to Class 19AR.

The Class 19A 4-8-2 Mountain type steam locomotive was a later modified version of the successful Class 19 which had been introduced a year earlier. Thirty-six Class 19A engines were delivered by Swiss Locomotive and Machine Works (SLM) of Winterthur in 1929, numbered in the range from 675 to 710.

Like the Class 19, the Class 19A also had Walschaerts valve gear and a bar frame. Col F.R. Collins DSO, Chief Mechanical Engineer (CME) of the South African Railways (SAR) at the time, redesigned the Class 19 to achieve a lighter axle loading by reducing the coupled wheel diameters from 54 to 51 inches (1,372 to 1,295 millimetres), reducing the cylinder diameter from 21 to 19 ¹⁄₂ inches (533 to 495 millimetres) and by using a slightly smaller boiler.

The reduction in axle load was to suit some of the lighter branch lines and, as part of the weight reduction, the Class 19A was delivered with a new smaller Type MP tender with a fuel capacity of 9 long tons 4 hundredweight (9.3 tonnes), a water capacity of 4,250 imperial gallons (19,300 litres) and a maximum axle load of 12 long tons 17 hundredweight 2 quarters (13,080 kilograms). The leading coupled wheels had flangeless tyres, but these were later flanged.

While the aim was to reduce the locomotive's total weight for use on some of the more lightly laid branch lines, the actual achieved weight saving was a mere four tons which could hardly have justified the cost of redesigning.

The trailing bissel truck was constructed with three holes to enable the compensating beam to be fitted at three locations which enabled it to be used to redistribute the engine's weight on the trailing axle. The axle load weights as listed for the Class 19A are with the trailing truck compensating beam pin in the leading of the three holes. The axle load weights as listed for the Class 19AR are with the trailing truck compensating beam pin in the centre hole.

From the 1930s, many serving locomotives were reboilered with a standard boiler type designed by then CME A.G. Watson as part of his standardisation policy. Such Watson Standard reboilered locomotives were reclassified by adding an "R" suffix to their classification.