South African Class 16B 4-6-2

South African Class 16B & 16CR 4-6-2
No. 805 plinthed at Johannesburg station, 1978
Type and origin ♠ Class 16B as built with a Belpaire firebox ♥ Class 16CR 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 21492-21501 Model Class 16B Build date 1917 Total produced 10
Specifications Configuration: ​  • Whyte 4-6-2 (Pacific)  • UIC 2'C1'h2 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 55 ft 11 3⁄4 in (17,062 mm)  • Engine 29 ft 5 1⁄2 in (8,979 mm)  • Leading 6 ft 2 in (1,880 mm)  • Coupled 10 ft 9 in (3,277 mm)  • Tender 16 ft 9 in (5,105 mm)  • Tender bogie 4 ft 7 in (1,397 mm) Length: ​  • Over couplers 64 ft 4 1⁄8 in (19,612 mm) Height ♠ 12 ft 10 in (3,912 mm) ♥ 12 ft 11 1⁄4 in (3,943 mm) Frame type Plate Axle load ♠ 18 LT (18,290 kg) ♥♣ 17 LT 14 cwt (17,980 kg)  • Leading ♠ 16 LT 3 cwt (16,410 kg) ♥♣ 16 LT 12 cwt (16,870 kg)  • 1st coupled ♠ 18 LT (18,290 kg) ♥♣ 17 LT 11 cwt (17,830 kg)  • 2nd coupled ♠ 18 LT (18,290 kg) ♥♣ 17 LT 14 cwt (17,980 kg)  • 3rd coupled ♠ 17 LT 18 cwt (18,190 kg) ♥♣ 17 LT 11 cwt (17,830 kg)  • Trailing ♠ 13 LT 12 cwt (13,820 kg) ♥♣ 13 LT 7 cwt (13,560 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 ♠ 53 LT 18 cwt (54,760 kg) ♥♣ 52 LT 16 cwt (53,650 kg) Loco weight ♠ 83 LT 13 cwt (84,990 kg) ♥♣ 82 LT 15 cwt (84,080 kg) Tender weight 51 LT 1 cwt (51,870 kg) Total weight ♠ 134 LT 14 cwt (136,900 kg) ♥♣ 133 LT 16 cwt (135,900 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 ♠♥ 37 sq ft (3.4 m2) Boiler: ​  • Model Watson Standard no. 2B  • Pitch ♠ 7 ft 9 in (2,362 mm) ♥ 8 ft (2,438 mm)  • Diameter ♠ 5 ft 4 5⁄8 in (1,641 mm) ♥ 5 ft 7 1⁄2 in (1,714 mm)  • Tube plates ♠ 18 ft 3 in (5,563 mm) ♥♣ 18 ft 4 in (5,588 mm) ♥♦ 18 ft 3 5⁄8 in (5,578 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 ♠ 190 psi (1,310 kPa) ♥ 200 psi (1,379 kPa) Safety valve ♠ Ramsbottom ♥ Pop Heating surface ♠ 2,186 sq ft (203.1 m2) ♥ 1,978 sq ft (183.8 m2)  • Tubes ♠ 2,040 sq ft (190 m2) ♥ 1,836 sq ft (170.6 m2)  • Firebox ♠ 146 sq ft (13.6 m2) ♥ 142 sq ft (13.2 m2) Superheater: ​  • Heating area ♠ 515 sq ft (47.8 m2) ♥ 472 sq ft (43.9 m2) Cylinders Two Cylinder size 22 in (559 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 ♠ 29,890 lbf (133.0 kN) @ 75% ♥ 29,960 lbf (133.3 kN) @ 75%
Career Operators South African Railways Class Class 16B & 16CR Number in class 10 Numbers 802-811 Delivered 1917 First run 1917 Withdrawn 1976
The 2nd coupled axle had flangeless wheels

The South African Railways Class 16B 4-6-2 of 1917 was a steam locomotive.

In November 1917, the South African Railways placed ten Class 16B steam locomotives with a 4-6-2 Pacific type wheel arrangement in passenger train service.

The Class 16B 4-6-2 Pacific type locomotive was designed by D.A. Hendrie, Chief Mechanical Engineer (CME) of the South African Railways (SAR), and built in 1917 by the North British Locomotive Company (NBL) in Glasgow, Scotland. Ten locomotives were delivered and placed in service in November 1917, numbered in the range from 802 to 811.

They were identical to the predecessor Class 16 and successor Class 16C in most respects, except that they had wider cabs than the Class 16, while the Class 16C was equipped with a combustion chamber in the firebox. Other minor alterations from the Class 16's characteristics were the injector and some cab and footplate arrangements.

During 1936, the coupled wheels were enlarged from 60 to 63 inches (1,524 to 1,600 millimetres) diameter and the boiler pressure setting accordingly adjusted from 190 to 200 pounds per square inch (1,310 to 1,379 kilopascals), which raised their tractive effort slightly from 29,890 to 29,960 pounds-force (133.0 to 133.3 kilonewtons) at 75% of boiler pressure.

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

Eventually all ten Class 16B locomotives as well as all thirty Class 16C locomotives were reboilered with Watson Standard no 2B boilers. In the process of reboilering, the main difference between the Class 16B and Class 16C, Hendrie's combustion chamber behind the Class 16C boiler, disappeared and the reboilered Class 16B locomotives were also reclassified to Class 16CR. Early conversions were equipped with copper and later conversions with steel fireboxes. In the process, they were also equipped with Watson cabs with their distinctive slanted fronts, compared to the conventional vertical fronts of their original cabs.

Some ex Class 16B locomotives erroneously received new number plates after reboilering which identified them as Class 16BR, even though such an SAR Class never officially existed.

Their original Belpaire boilers were fitted with Ramsbottom safety valves, while the Watson Standard boiler was fitted with Pop safety valves. An obvious visual difference between an original and a Watson Standard reboilered locomotive is usually a rectangular regulator cover, just to the rear of the chimney on the reboilered locomotive. In the case of the Class 16B and Class 16CR, two even more obvious differences are the Watson cab and the absence of the Belpaire firebox hump between the cab and boiler on the reboilered locomotives.