South African Class 1A 4-8-0

NGR Class B 4-8-0 1910
South African Class 1A 4-8-0

SAR Class 1A no. 1301, ex NGR Class B no. 25, Mason's Mill Loco, 6 July 1962

Type and origin Power type Steam Designer Natal Government Railways (D.A. Hendrie) Builder North British Locomotive Company Serial number 19051-19071 Model NGR Hendrie B Build date 1910 Total produced 21

Specifications Configuration 4-8-0 (Mastodon) Driver 2nd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 28 1⁄2 in (724 mm) Coupled dia. 46 in (1,168 mm) Tender wheels 30 in (762 mm) Wheelbase 50 ft 3 1⁄4 in (15,323 mm)  • Engine 22 ft 6 in (6,858 mm)  • Leading 6 ft (1,829 mm)  • Coupled 12 ft 9 in (3,886 mm)  • Tender 16 ft 6 in (5,029 mm)  • Tender bogie 4 ft 6 in (1,372 mm) Length: ​  • Over couplers 57 ft 10 in (17,628 mm) Height 12 ft 7 1⁄4 in (3,842 mm) Frame type Plate Axle load 14 LT 11 cwt (14,780 kg)  • Leading 13 LT 12 cwt (13,820 kg)  • 1st coupled 14 LT 7 cwt (14,580 kg)  • 2nd coupled 14 LT 11 cwt (14,780 kg)  • 3rd coupled 13 LT 17 cwt (14,070 kg)  • 4th coupled 14 LT 6 cwt (14,530 kg)  • Tender bogie Bogie 1: 20 LT 1 cwt (20,370 kg) Bogie 2: 20 LT 10 cwt (20,830 kg)  • Tender axle 10 LT 5 cwt (10,410 kg) Adhesive weight 57 LT 1 cwt (57,970 kg) Loco weight 70 LT 13 cwt (71,780 kg) Tender weight 40 LT 11 cwt (41,200 kg) Total weight 111 LT 4 cwt (113,000 kg) Tender type TJ (2-axle bogies) TJ, TL, TM permitted Fuel type Coal Fuel capacity 6 LT (6.1 t) Water cap 3,500 imp gal (15,900 l) Firebox type Belpaire & combustion chamber  • Firegrate area 34 sq ft (3.2 m2) Boiler: ​  • Pitch 7 ft 4 1⁄4 in (2,242 mm)  • Diameter 5 ft 4 1⁄2 in (1,638 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 2,188 sq ft (203.3 m2)  • Tubes 2,056 sq ft (191.0 m2)  • Firebox 132 sq ft (12.3 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 Piston on no. 33 Couplers Johnston link-and-pin AAR knuckle (1930s)

Performance figures Tractive effort 31,240 lbf (139.0 kN) @ 75%

Career Operators Natal Government Railways South African Railways Class NGR Class B SAR Class 1A Number in class 21 Numbers NGR 13-33 SAR 1289-1309 Delivered 1910 First run 1910 Withdrawn 1974

The leading coupled axle had flangeless wheels

The South African Railways Class 1A 4-8-0 of 1910 was a steam locomotive from the pre-Union era in the Colony of Natal.

In 1910, the Natal Government Railways placed 21 improved Class B 4-8-0 Mastodon type tender locomotives in service. In 1912, when these locomotives were assimilated into the South African Railways, they were renumbered and designated Class 1A.

By 1909, more locomotives were required for goods operation on the lower sections of the Natal mainline and a further 21 locomotives of the Class B 4-8-0 Mastodon design were ordered by the Natal Government Railways (NGR). They were delivered and placed in service in 1910, built by the North British Locomotive Company with Type TJ tenders and numbered in the range from 13 to 33. These locomotives were also officially designated Class B and, since they incorporated various improvements on the locomotives of 1904, they became commonly known as the Class Improved Hendrie B.

Like their predecessors, they had Belpaire fireboxes with combustion chambers and Walschaerts valve gear. While they were practically identical to the 1904 lcomotives in most respects, their boilers had been raised by 1 ¹⁄₄ inches (32 millimetres), which raised the boiler pitch by 1 inch (25 millimetres) to 7 feet 4 ¹⁄₄ inches (2,242 millimetres) and gave a better rake on the sides of the ash pan.

With one exception, they used Murdoch's D slide valves like the 1904 locomotives. The last locomotive, no. 33, was an experimental locomotive equipped with piston valves.

They were built with Hendrie’s steam reversers. The Hendrie steam reversing gear consisted of a 5 ¹⁄₂ inches (140 millimetres) diameter steam cylinder and a 5 inches (127 millimetres) diameter oil cylinder, arranged in line on a bracket which was fixed to the main engine frame on the driver's side. The cylinders had a common piston rod which had a slot in the centre, between the cylinders. This slot accommodated a sliding crosshead which engaged with an arm fixed to the reversing shaft.