Class MA (Locobase 2776)

Data from Holland (1972,I), p. 105. See also See also Cdr J Plomer, "A Long Line of Mountains", The Railway and Locomotive Historical Society Bulletin, No. 122 (April 1970), pp. 7-25. Works number was 46044 in July 1909'

The NGR applied to a North American builder when they decided a Mallet layout would improve their drag-freight ton-mileage and Alco responded with this prototype. The big steam dome sat near the rear of the boiler to feed the HP cylinders below. These had piston valves. The larger LP cylinders in front used balanced Richardson slide valves.

Plomer noted the initial resistance from railwaymen in the "ultra British colony", which he characterized as "some prejudice in the guise of patriotism ...But no one could deisny their performance." Indeed, the first supporters were the crews "who got the feel of the engine."

Not big for a North American articulated, the MA proved quite suitable for its helper (banker) service on the grades between Escourt and Highlands.

Class MB (Locobase 2935)

Data from Holland (1972,II), p. 14. Works numbers were 48237-48241 in August 1910.

The first Mallet in South Africa was the MA, described in Locobase 13067. These five followed as enlargements of what had proved to be a satisfactory prototype. Although they were originally assigned NGR numbers, the class was delivered after the NGR was incorporated into the South African Railways system.

Compared to the MA, the MBs put more weight on the drivers and, thanks to the last axles's support of a heavier firebox, had a higher maximum axle loading as well. Increased grate area led to a larger firebox and 30 more tubes (of shorter length) filled a larger boiler. Like the MA, the MBs used piston valves on the HP cylinders, slide valves on the larger LP cylinders in front.

Ten more arrived in 1912, built to almost identical specifications; see Locobase 13089.

Class MC (Locobase 13087)

Data from Holland (1972, II), pp. 21-22. Works numbers were 19577-19586 in in 1912.

These essentially repeated the Alco MBs of the previous two years (Locobase 13088), but the builder was headquartered in Glasgow rather than Schenectady. The MCs had two fewer tubes that were about 4" shorter between the tubesheets. Like the others, these were satisfactory as low-speed bankers.

North British followed shortly with 15 superheated versions of this design; see Locobase 3615

Class MC1 (Locobase 3615)

Data from Holland (1972, II), pp. 21-22. Works numbers were 20442-20456 in 1913-1914..

By the time the MCs arrived on SAR rails (Locobase 13089), it was clear that any future Mallets would have to be superheated. So the SAR went to the MC's builder and worked out a dry-steam variant, taking advantage of the greater implicit power by slightly enlarging the cylinder volumes.

Holland reports that the result showed "...far better performance, and an increased tractive effort." They joined the Alcos and the MCs hauling coal trains from the Witbank mines. Some later served as bankers (helpers) at De Doorns.

Class MJ (Locobase 2864)

Data from Holland (1972,II). Maffei works numbers were 3452-3461 in 1914.

Mallet articulated compound similar to the Alco-built engines that pioneered Mallets in South Africa (see Locobases 13087-13088). The MJs had a Belpaire firebox, outside bearings on the leading truck, and slide valves forward with piston valves supplying the rear cylinders. Their light axle loading responded to the need for Mallet power on branch lines.

Maffei built the first two, North British the next eight and, after the 1918 Armistice, Maffei supplied the last eight. Their service was as pusher engines up the 16-mile (26 km) Hex River Pass section between De Doorns and Matroosburg in the Cape Province. The ruling grade is 1.8%, but the heaviest work was done on the five miles that were pitched at 2.3%.

Holland notes that two MJs were the last Mallets to work in South Africa, being scrapped in 1962.

Class MJ1 (Locobase 13093)

Data from Holland (1972,II), pp. 36-37. See also "Mallet Locomotives for the South African Railways", Locomotive Magazine, Volume XXIV [24], No 315 (15 November 1918), pp. 173-174. Works numbers were 58427-58434 in 1918.

Following up on the earlier orders for the branch-line MJ Mallet (Locobase 2864), this octet from Canada had a larger boiler and put more weight on the drivers. At the same time, superheater area increased to claim a larger percentage of combined heating surface.

NB: Locobase initially entered the tube count as given by Holland in his diagram on page 37. After calculating the tube surface area, however, the compiler changed the count from 146 to 156 to match the area given in the specifications. The change was in line with Holland's comment that these were repeats of the MJ with larger boilers.