South African Class 16D 4-6-2

South African Class 16D 4-6-2
No. 860 on the Union Limited, Paarl, c. 2001
Type and origin ♠ With 60 inch (1,520 mm) coupled wheels ♥ With 63 inch (1,600 mm) coupled wheels ♣ 22x26 Cylinders - ♦ 23x26 Cylinders Power type Steam Designer Baldwin Locomotive Works Builder Baldwin Locomotive Works Serial number 58309-58310, 58703-58707 Model Class 16D Build date 1925-1926 Total produced 7
Specifications Configuration: ​  • Whyte 4-6-2 (Pacific)  • UIC 2'C1'h4 Driver 2nd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 30 in (762 mm) Coupled dia. ♠ 60 in (1,524 mm) ♥ 63 in (1,600 mm) Trailing dia. 33 in (838 mm) Tender wheels 34 in (864 mm) Wheelbase 60 ft 3 3⁄16 in (18,369 mm)  • Engine 30 ft 8 in (9,347 mm)  • Leading 6 ft 10 in (2,083 mm)  • Coupled 11 ft (3,353 mm)  • Tender 20 ft 5 in (6,223 mm)  • Tender bogie 6 ft 2 in (1,880 mm) Length: ​  • Over couplers 68 ft 2 3⁄16 in (20,782 mm) Height ♠ 12 ft 10 in (3,912 mm) ♥ 12 ft 11 1⁄2 in (3,950 mm) Frame type Bar Axle load ♠ 18 LT 15 cwt (19,050 kg) ♥ 19 LT 2 cwt (19,410 kg)  • Leading ♠ 18 LT 10 cwt (18,800 kg) ♥ 18 LT 10 cwt (18,800 kg)  • Coupled ♠ 18 LT 15 cwt (19,050 kg)  • 1st coupled ♥ 19 LT 2 cwt (19,410 kg)  • 2nd coupled ♥ 19 LT (19,300 kg)  • 3rd coupled ♥ 19 LT 2 cwt (19,410 kg)  • Trailing ♠♥ 14 LT 17 cwt (15,090 kg)  • Tender bogie Bogie 1: 33 LT 18 cwt (34,440 kg) Bogie 2: 35 LT 10 cwt (36,070 kg)  • Tender axle 17 LT 15 cwt (18,030 kg) Adhesive weight ♠ 56 LT 5 cwt (57,150 kg) ♥ 57 LT 4 cwt (58,120 kg) Loco weight ♠ 89 LT 12 cwt (91,040 kg) ♥ 90 LT 11 cwt (92,000 kg) Tender weight 69 LT 8 cwt (70,510 kg) Total weight ♠ 159 LT (161,600 kg) ♥ 159 LT 19 cwt (162,500 kg) Tender type KT (2-axle bogies) Fuel type Coal Fuel capacity 14 LT (14.2 t) Water cap 6,000 imp gal (27,300 l) Firebox type Round-top  • Firegrate area 45 sq ft (4.2 m2) Boiler: ​  • Pitch ♠ 8 ft 6 in (2,591 mm) ♥ 8 ft 7 1⁄2 in (2,629 mm)  • Diameter 5 ft 10 1⁄4 in (1,784 mm)  • Tube plates 17 ft 10 5⁄8 in (5,451 mm)  • Small tubes 181: 2 in (51 mm)  • Large tubes 30: 5 3⁄8 in (137 mm) Boiler pressure ♠ 195 psi (1,344 kPa) ♥ 205 psi (1,413 kPa) Safety valve Pop Heating surface 2,639 sq ft (245.2 m2)  • Tubes 2,453 sq ft (227.9 m2)  • Arch tubes 22 sq ft (2.0 m2)  • Firebox 164 sq ft (15.2 m2) Superheater: ​  • Heating area 593 sq ft (55.1 m2) Cylinders Two Cylinder size ♣ 22 in (559 mm) bore ♦ 23 in (584 mm) bore ♣♦ 26 in (660 mm) stroke Valve gear Walschaerts Valve type Piston Couplers Johnston link-and-pin AAR knuckle (1930s)
Performance figures Tractive effort ♠♣ 30,670 lbf (136.4 kN) @ 75% ♠♦ 33,530 lbf (149.1 kN) @ 75% ♥♣ 30,710 lbf (136.6 kN) @ 75% ♥♦ 33,570 lbf (149.3 kN) @ 75%
Career Operators South African Railways Class Class 16D Number in class 7 Numbers 860-866 Nicknames Big Bertha Delivered 1925-1926 First run 1925 Withdrawn 1972

The South African Railways Class 16D 4-6-2 of 1925 was a steam locomotive.

In 1925, the South African Railways placed two American-built Class 16D locomotives with a 4-6-2 Pacific type wheel arrangement in passenger train service. Five more of these locomotives were ordered and placed in service in 1926.

On 15 December 1924, after an official tour of investigation to the United States of America by G.E. Titren, the Superintendent Motive Power of the South African Railways (SAR), an order was placed with the Baldwin Locomotive Works of Philadelphia for four experimental locomotives, two of which were of a 4-6-2 Pacific type wheel arrangement. These locomotives were all delivered in 1925. The two Pacifics were designated Class 16D and numbered 860 and 861.

The two Mountain types, which arrived from the same builders in the same shipment, were designated Class 15C. The Classes 16D and 15C were specially designed for working the Union Limited (Johannesburg to Cape Town) and Union Express (Cape Town to Johannesburg) passenger trains, the forerunners of the Blue Train.

These locomotives conformed to SAR requirements as far as practicable but also incorporated the latest American railway engineering practices. The engines introduced several features which were new to the SAR at the time, such as top feeds to the boiler, self-cleaning smokeboxes, Sellar's drifting valves, and grease lubrication to the coupled wheel axle boxes, crank pins and connecting rod big ends.

The locomotive's size quickly earned it the nickname Big Bertha, while its contemporary Class 15C locomotive was nicknamed Big Bill. The first two Pacifics were followed by another five locomotives from the same manufacturer in 1926, numbered in the range from 862 to 866.

They had 5 inches (127 millimetres) thick bar frames, which extended from the front buffer beam to the rear dragbox. The boilers were equipped with three Coale pop type safety valves and Schmidt type superheaters. Their fireboxes were equipped with flexible side stays and water siphon arch tubes to support the brick arch and to improve circulation. Their Type KT tenders, arranged with self-trimming type coal bunkers, had a coal capacity of 14 long tons (14.2 tonnes) and a water capacity of 6,000 imperial gallons (27,300 litres) which was considered sufficient for the engines to travel 100 miles (161 kilometres) without having to replenish water.