South African Class 1B 4-8-2

NGR Class B 4-8-2 1906 South African Class 1B 4-8-2
SAR Class 1B no. 1445, ex NGR Class B no. 324
Type and origin Power type Steam Designer Natal Government Railways (D.A. Hendrie) Builder North British Locomotive Company Natal Government Railways Serial number 16414-16419 Model NGR Class B Build date 1906 Total produced 6 Rebuilder South African Railways Rebuild date 1926-1928 Number rebuilt 6 to SAR Class 1 4-8-0 (Mastodon)
Specifications Configuration: ​  • Whyte 4-8-2 (Mountain)  • UIC 2'D1'n2 Driver 2nd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 28 1⁄2 in (724 mm) Coupled dia. 45 1⁄2 in (1,156 mm) Trailing dia. 28 1⁄2 in (724 mm) Tender wheels 30 in (762 mm) Wheelbase 49 ft 5⁄8 in (14,951 mm)  • Engine 27 ft 6 in (8,382 mm)  • Leading 6 ft (1,829 mm)  • Coupled 12 ft 9 in (3,886 mm)  • Tender 15 ft 6 in (4,724 mm)  • Tender bogie 4 ft 6 in (1,372 mm) Length: ​  • Over couplers 56 ft 4 7⁄8 in (17,193 mm) Height 12 ft 6 in (3,810 mm) Frame type Plate Axle load 14 LT 17 cwt (15,090 kg)  • Leading 12 LT 2 cwt (12,290 kg)  • 1st coupled 14 LT 2 cwt (14,330 kg)  • 2nd coupled 14 LT 17 cwt (15,090 kg)  • 3rd coupled 14 LT (14,220 kg)  • 4th coupled 13 LT (13,210 kg)  • Trailing 2 LT 10 cwt (2,540 kg)  • Tender bogie Bogie 1: 18 LT 18 cwt (19,200 kg) Bogie 2: 19 LT 1 cwt (19,360 kg)  • Tender axle 9 LT 10 cwt 2 qtr (9,678 kg) Adhesive weight 55 LT 19 cwt (56,850 kg) Loco weight 70 LT 11 cwt (71,680 kg) Tender weight 37 LT 19 cwt (38,560 kg) Total weight 108 LT 10 cwt (110,200 kg) Tender type SH (2-axle bogies) SH, SK permitted Fuel type Coal Fuel capacity 6 LT (6.1 t) Water cap 3,225 imp gal (14,700 l) Firebox type Belpaire & combustion chamber  • Firegrate area 34 sq ft (3.2 m2) Boiler: ​  • Pitch 7 ft 3 in (2,210 mm)  • Diameter 5 ft 4 3⁄4 in (1,645 mm)  • Tube plates 12 ft 1 in (3,683 mm)  • Small tubes 325: 2 in (51 mm) Boiler pressure 190 psi (1,310 kPa) Safety valve Ramsbottom Heating surface 2,222.8 sq ft (206.50 m2)  • Tubes 2,094.17 sq ft (194.555 m2)  • Firebox 128.63 sq ft (11.950 m2) Cylinders Two Cylinder size 20 1⁄2 in (521 mm) bore 24 in (610 mm) stroke Valve gear Walschaerts Valve type Murdoch's D slide Couplers Johnston link-and-pin AAR knuckle (1930s)
Performance figures Tractive effort 31,600 lbf (141 kN) @ 75%
Career Operators Natal Government Railways South African Railways Class NGR Altered Class B SAR Class 1B Number in class 6 Numbers NGR 319-324 SAR 1440-1445 Delivered 1906 First run 1906 Withdrawn 1935-1975
The leading coupled axle had flangeless wheels

The South African Railways Class 1B 4-8-2 of 1904 was a steam locomotive from the pre-Union era in the Colony of Natal.

In 1904, the Natal Government Railways placed fifty Class B locomotives with a 4-8-0 Mastodon wheel arrangement in service. Of these, six were modified in 1906 to Altered Class B locomotives, the first tender engines in the world with a 4-8-2 Mountain wheel arrangement. In 1912, when these six engines were assimilated into the South African Railways, they were renumbered and designated Class 1B.

At the time when D.A. Hendrie was appointed as the Locomotive Superintendent of the Natal Government Railways (NGR), it had a large fleet of tank locomotives with an inherent limited coal and water range. It was also often necessary to double- and even triple-head trains over the worst sections of the mainline with its steep 1 in 30 (3⅓%) gradients. Hendrie was therefore tasked to produce a locomotive of greater power and capable of longer distances without refuelling or rewatering. His resulting Hendrie B achieved this and fifty such locomotives were delivered from the North British Locomotive Company (NBL) in 1904.

The engines used saturated steam and had plate frames, Belpaire fireboxes, Walschaerts valve gear and "D" slide valves. While the boiler was not pitched very high, Hendrie had still managed to extend the firebox sideways over the trailing driving wheels, with the result that the grate was almost on a level with the bottom of the boiler shell. To prevent the fire from entering the lower row of tubes, Hendrie arranged a vertical firewall towards the front of the grate, which created a dry combustion chamber.

In 1906, six of these locomotives with numbers in the range from 319 to 324, were modified to a 4-8-2 wheel arrangement by adding a trailing bissel truck below the cab. The modification was deemed necessary to ensure extra smooth running while hauling fast passenger trains. This modification turned them into the NGR’s Altered Class B, the first 4-8-2 Mountain type tender locomotives in the world.