South African Class MJ1 2-6-6-0

South African Class MJ1 2-6-6-0

SAR Class MJ1 no. 1673, c. 1920

Type and origin ♠ Locomotive as built - ♥ Reboilered locomotive Power type Steam Designer Montreal Locomotive Works Builder Montreal Locomotive Works Serial number 58427-58434 Model SAR Class MJ1 Build date 1918 Total produced 8

Specifications Configuration 2-6-6-0 (Denver) Driver 3rd & 6th coupled axles Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 28 1⁄2 in (724 mm) Coupled dia. 42 1⁄2 in (1,080 mm) as built 42 3⁄4 in (1,086 mm) retyred Tender wheels 34 in (864 mm) Wheelbase 60 ft 8 1⁄4 in (18,498 mm)  • Engine 32 ft 8 in (9,957 mm)  • Coupled 8 ft 4 in (2,540 mm) per unit  • Tender 17 ft 11 in (5,461 mm)  • Tender bogie 4 ft 7 in (1,397 mm) Length: ​  • Over couplers 68 ft 7 1⁄8 in (20,907 mm) Height ♠♥ 12 ft 6 1⁄8 in (3,813 mm) Frame type Bar Axle load ♠ 14 LT 2 cwt (14,330 kg)  • Leading ♠ 7 LT 10 cwt (7,620 kg)  • 1st coupled ♠ 13 LT 13 cwt (13,870 kg)  • 2nd coupled ♠ 13 LT 15 cwt (13,970 kg)  • 3rd coupled ♠ 14 LT 2 cwt (14,330 kg)  • 4th coupled ♠ 12 LT 11 cwt (12,750 kg)  • 5th coupled ♠ 13 LT 12 cwt (13,820 kg)  • 6th coupled ♠ 13 LT 7 cwt (13,560 kg)  • Tender axle 12 LT 14 cwt 2 qtr (12,930 kg) av. Adhesive weight ♠ 81 LT (82,300 kg) Loco weight ♠ 88 LT 10 cwt (89,920 kg) Tender weight 50 LT 18 cwt (51,720 kg) Total weight ♠ 139 LT 8 cwt (141,600 kg) Tender type LP (2-axle bogies) Fuel type Coal Fuel capacity 10 LT (10.2 t) Water cap 4,250 imp gal (19,300 l) Firebox type Belpaire  • Firegrate area ♠♥ 40 sq ft (3.7 m2) Boiler: ​  • Pitch ♠♥ 7 ft 9 1⁄8 in (2,365 mm)  • Diameter ♠ 5 ft 2 3⁄4 in (1,594 mm) ♥ 5 ft 1 1⁄2 in (1,562 mm)  • Tube plates ♠ 17 ft 3⁄8 in (5,191 mm) ♥ 17 ft 1⁄4 in (5,188 mm)  • Small tubes ♠ 146: 2 in (51 mm) ♥ 151: 2 in (51 mm)  • Large tubes ♠ 22: 5 3⁄8 in (137 mm) ♥ 18: 5 1⁄2 in (140 mm) Boiler pressure ♠♥ 200 psi (1,379 kPa) Safety valve Ramsbottom Heating surface ♠ 2,042 sq ft (189.7 m2) ♥ 1,913 sq ft (177.7 m2)  • Tubes ♠ 1,906 sq ft (177.1 m2) ♥ 1,780 sq ft (165 m2)  • Firebox ♠ 136 sq ft (12.6 m2) ♥ 133 sq ft (12.4 m2) Superheater: ​  • Type ♠♥ Schmidt  • Heating area ♠ 413 sq ft (38.4 m2) ♥ 350 sq ft (33 m2) Cylinders Four High-pressure cylinder 16 1⁄2 in (419 mm) bore 24 in (610 mm) stroke Low-pressure cylinder 26 in (660 mm) bore 24 in (610 mm) stroke Valve gear Walschaerts Valve type Piston Couplers Johnston link-and-pin AAR knuckle (1930s)

Performance figures Tractive effort ♠ 38,170 lbf (169.8 kN) @ 50% ♥ 37,950 lbf (168.8 kN) @ 50%

Career Operators South African Railways Class Class MJ1 Number in class 8 Numbers 1666-1673 Delivered 1918 First run 1918 Withdrawn c. 1960

The South African Railways Class MJ1 2-6-6-0 of 1918 was a steam locomotive.

In 1918, the South African Railways placed eight Class MJ1 Mallet articulated compound steam locomotives with a 2-6-6-0 wheel arrangement in branch line service.

Because of the difficulties experienced by the usual British and German suppliers to build new locomotives during the First World War, orders for the Class MJ1 2-6-6-0 Mallet articulated compound steam locomotive were placed with Montreal Locomotive Works (MLW) in Canada. The locomotive was designed by MLW, based on the specifications for the Class MJ Mallet which had been designed by D.A. Hendrie, the Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1910 to 1922. Eight of these branch line locomotives were built and delivered by MLW in November 1918, numbered in the range from 1666 to 1673.

The locomotives were superheated, had Walschaerts valve gear and, like the Class MJ Mallets, had Belpaire fireboxes, but slightly larger boilers. When compared to the Class MJ, a distinguishing feature of the Class MJ1 was the sandbox which was mounted on top of the boiler to the rear of the steam dome in North American style. In general appearance, they bore a family resemblance to the Class 14C and Class 15B 4-8-2 locomotives which were also built by MLW in 1918.

During 1922, the coupled wheels were retyred and their diameter was increased from 42 ¹⁄₂ inches (1,080 millimetres) to 42 ³⁄₄ inches (1,086 millimetres).

During 1939, while W.A.J. Day was the CME of the SAR, the Classes MJ and MJ1 were modified slightly to be reboilered with the same standard boiler.

The Class MJ1 was the last Mallet locomotive class to be placed in service by the SAR. All the Railway’s subsequent new articulated locomotives were to be Garratts, Modified Fairlies and Union Garratts.