South African Class 15 4-8-2

South African Class 15 & 15AR 4-8-2
No. 1566, reboilered and reclassified to Class 15AR, Port Elizabeth, 3 April 1978
Type and origin ♠ Class 15 as built with a Belpaire firebox ♥ Class 15AR rebuilt with a Watson Standard boiler ♣ Steel firebox - ♦ Copper firebox Power type Steam Designer South African Railways (D.A. Hendrie) Builder North British Locomotive Company Serial number 20364-20373 Model Class 15 Build date 1914 Total produced 10
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. 57 in (1,448 mm) Trailing dia. 33 in (838 mm) Tender wheels 34 in (864 mm) Wheelbase 60 ft 6 in (18,440 mm)  • Engine 33 ft 8 in (10,262 mm)  • Leading 6 ft 2 in (1,880 mm)  • Coupled 15 ft (4,572 mm)  • Tender 16 ft 9 in (5,105 mm)  • Tender bogie 4 ft 7 in (1,397 mm) Length: ​  • Over couplers 68 ft 10 3⁄4 in (20,999 mm) Height ♠ 12 ft 10 in (3,912 mm) ♥ 12 ft 11 3⁄4 in (3,956 mm) Frame type Plate Axle load ♠♥♣ 16 LT 11 cwt (16,820 kg) ♥♦ 16 LT 14 cwt (16,970 kg)  • Leading ♠ 15 LT 14 cwt (15,950 kg) ♥♣ 16 LT 1 cwt (16,310 kg) ♥♦ 16 LT 6 cwt (16,560 kg)  • 1st coupled ♠♥♣ 16 LT 10 cwt (16,760 kg) ♥♦ 16 LT 13 cwt (16,920 kg)  • 2nd coupled ♠ 16 LT 10 cwt (16,760 kg) ♥♣ 16 LT 9 cwt (16,710 kg) ♥♦ 16 LT 6 cwt (16,560 kg)  • 3rd coupled ♠♥♣ 16 LT 11 cwt (16,820 kg) ♥♦ 16 LT 14 cwt (16,970 kg)  • 4th coupled ♠♥♣ 16 LT 9 cwt (16,710 kg) ♥♦ 16 LT 11 cwt (16,820 kg)  • Trailing ♠♥♣ 12 LT 6 cwt (12,500 kg) ♥♦ 12 LT 7 cwt (12,550 kg)  • Tender bogie Bogie 1: 27 LT 10 cwt (27,940 kg) Bogie 2: 23 LT 11 cwt (23,930 kg)  • Tender axle 13 LT 15 cwt (13,970 kg) Adhesive weight ♠ 66 LT (67,060 kg) ♥♣ 65 LT 19 cwt (67,010 kg) ♥♦ 66 LT 4 cwt (67,260 kg) Loco weight ♠ 94 LT (95,510 kg) ♥♣ 94 LT 6 cwt (95,810 kg) ♥♦ 94 LT 17 cwt (96,370 kg) Tender weight 51 LT 1 cwt (51,870 kg) Total weight ♠ 145 LT 1 cwt (147,400 kg) ♥♣ 145 LT 7 cwt (147,700 kg) ♥♦ 145 LT 18 cwt (148,200 kg) Tender type MP1 (2-axle bogies) MP, MP1, MR, MS, MT, MT1, MT2, MX, MY, MY1 permitted Fuel type Coal Fuel capacity 10 LT (10.2 t) Water cap 4,250 imp gal (19,300 l) Firebox type ♠ Belpaire - ♥ Round-top  • Firegrate area ♠ 40 sq ft (3.7 m2) ♥ 37 sq ft (3.4 m2) Boiler: ​  • Model Watson Standard no. 2A  • Pitch ♠ 7 ft 9 in (2,362 mm) ♥ 8 ft 1⁄2 in (2,451 mm)  • Diameter ♠ 5 ft 4 5⁄8 in (1,641 mm) ♥ 5 ft 7 1⁄2 in (1,714 mm)  • Tube plates ♠ 21 ft 9 in (6,629 mm) ♥♣ 21 ft 8 in (6,604 mm) ♥♦ 21 ft 7 5⁄8 in (6,594 mm)  • Small tubes ♠ 131: 2 1⁄4 in (57 mm) ♥ 87: 2 1⁄2 in (64 mm)  • Large tubes ♠ 24: 5 1⁄2 in (140 mm) ♥ 30: 5 1⁄2 in (140 mm) Boiler pressure ♠ 185 psi (1,276 kPa) ♥ 190 psi (1,310 kPa) Safety valve ♠ Ramsbottom - ♥ Pop Heating surface ♠ 2,578 sq ft (239.5 m2) ♥ 2,313 sq ft (214.9 m2)  • Tubes ♠ 2,423 sq ft (225.1 m2) ♥ 2,171 sq ft (201.7 m2)  • Firebox ♠ 155 sq ft (14.4 m2) ♥ 142 sq ft (13.2 m2) Superheater: ​  • Heating area ♠ 601 sq ft (55.8 m2) ♥ 537 sq ft (49.9 m2) Cylinders Two Cylinder size 22 in (559 mm) bore 28 in (711 mm) stroke Valve gear Walschaerts Valve type Piston Couplers Johnston link-and-pin AAR knuckle (1930s)
Performance figures Tractive effort ♠ 32,990 lbf (146.7 kN) @ 75% ♥ 33,880 lbf (150.7 kN) @ 75%
Career Operators South African Railways Swaziland Railway Class Class 15 & 15AR Number in class 10 Numbers 1561-1570 Delivered 1914 First run 1914 Withdrawn 1980s
The leading coupled axle had flangeless wheels

The South African Railways Class 15 4-8-2 of 1914 was a steam locomotive.

In 1914, the South African Railways placed ten Class 15 steam locomotives with a 4-8-2 Mountain type wheel arrangement in service.

D.A. Hendrie, Chief Mechanical Engineer (CME) of the South African Railways (SAR), commenced with design work on the Class 15 in 1913. It was intended as a mixed-traffic locomotive for use in the Orange Free State, where gradients and curvature were less severe than on the coastal sections. The locomotive was similar in general layout to the Classes 12 and 14, but with larger 57 inches (1,448 millimetres) coupled wheels. Ten locomotives were built by the North British Locomotive Company (NBL) and delivered in February and March 1914, numbered in the range from 1561 to 1570.

The engines had plate frames, Walschaerts valve gear, Belpaire fireboxes without combustion chambers and were superheated. They were delivered with Type MP1 tenders which had a coal capacity of 10 long tons (10.2 tonnes) and a water capacity of 4,250 imperial gallons (19,300 litres).

To reduce the weight on the trailing wheels, steel fireboxes were originally used instead of copper since the water quality in the Free State was considered suitable for this metal. Some locomotives in Natal had been fitted with steel fireboxes years previously and the results were fairly good, but wherever water supplies were of poor quality, steel fireboxes gave a lot of trouble and necessitated the introduction of water treatment plants to prevent corrosion.

This reintroduction of steel fireboxes eventually led to its widespread use on all the larger locomotive types, but it also forced the SAR to adopt locomotive water treatment as a general policy. There was no settled policy on water treatment for some years, but engines with copper fireboxes were used mainly in areas where the water was not of good quality. Hendrie followed a conservative policy in this respect and steel fireboxes were only to be fitted in large numbers by his successor, Colonel F.R. Collins DSO.

In the case of the Class 15, it was still early days for water treatment and enough trouble was experienced to result in their steel fireboxes being replaced with copper fireboxes. The locomotive's one flaw was excessively long fire tubes. On later models like the Class 15A, Hendrie improved the boiler by adding a combustion chamber, which shortened the distance between tube plates from 21 feet 9 inches (6,629 millimetres) to 19 feet (5,791 millimetres).