| South African Class MJ 2-6-6-0 | |
|---|---|
| SAR Class MJ 1651, circa 1914 | |
| Power type | Steam |
| Designer | South African Railways |
| Builder | Maffei North British Locomotive Company |
| Order number | NBL L657 |
| Serial number | Maffei 3452-3461 NBL 21248-21255[1][2][3] |
| Model | SAR Class MJ |
| Build date | 1914 |
| Total produced | 18 |
| Configuration | 2-6-6-0 Mallet |
| Gauge | 3 ft 6 in (1,067 mm) Cape gauge |
| Leading wheel diameter |
28.5 in (724 mm) |
| Driver diameter | 42.75 in (1,090 mm) |
| Wheelbase | Total: 58 ft 11.25 in (17.964 m) Engine: 8 ft 4 in (2.540 m) per coupled set 32 ft 8 in (9.957 m) total Tender: 4 ft 7 in (1.397 m) bogie 16 ft 9 in (5.105 m) total |
| Length | 67 ft 5.125 in (20.552 m) |
| Height | 12 ft 6.125 in (3.813 m) |
| Axle load | 13.75 long tons (14.0 t) on 6th driver |
| Weight on drivers | 76.15 long tons (77.4 t) |
| Locomotive weight | 84 long tons (85.3 t) |
| Tender weight | 51.35 long tons (52.2 t) w/o 49,452 lb (22.4 t) empty |
| Locomotive & tender combined weight |
135.35 long tons (137.5 t) |
| Tender type | MP1 – MP, MP1, MR permitted * 2 axle bogies * Wheels 34 in (864 mm) dia * Length 25 ft 10.75 in (7.893 m)[4] |
| Fuel type | Coal |
| Fuel capacity | 10 long tons (10.2 t) |
| Water capacity | 4,250 imp gal (19,300 l) |
| Boiler | As built: 5 ft 1.5 in (1.562 m) int dia at 1st ring 17 ft (5.182 m) int length 7 ft 9.125 in (2.365 m) pitch Reboilered: 5 ft 1.5 in (1.562 m) int dia 17 ft 0.25 in (5.188 m) int length 7 ft 9.125 in (2.365 m) pitch |
| Boiler pressure | 200 psi (1,380 kPa) |
| Firegrate area | 40 sq ft (3.716 m2) |
| Heating surface: Tubes |
151 tubes 2 in (50.8 mm) ext dia 18 tubes 5.5 in (140 mm) ext dia 1,783 sq ft (165.646 m2) as built 1,780 sq ft (165.367 m2) reboilered |
| Heating surface: Firebox |
130 sq ft (12.077 m2) as built 133 sq ft (12.356 m2) reboilered |
| Heating surface: Total |
1,913 sq ft (177.724 m2) |
| Superheater area | 343 sq ft (31.866 m2) as built 350 sq ft (32.516 m2) reboilered |
| Cylinders | Four |
| High-pressure cylinder size |
16.5 in (419 mm) bore 24 in (610 mm) stroke |
| Low-pressure cylinder size |
26 in (660 mm) bore 24 in (610 mm) stroke |
| Valve gear | Walschaerts[5] |
| Tractive effort | 37,950 lbf (168.8 kN) at 50% boiler pressure[2] |
| Career | South African Railways |
| Class | Class MJ[4] |
| Number in class | 18 |
| Number | 1651-1660, 1674-1681[2] |
| Delivered | 1914-1921 |
| First run | 1914 |
| Withdrawn | 1962 |
| Disposition | Retired |
Between 1914 and 1921 the South African Railways placed eighteen Class MJ Mallet articulated compound steam locomotives with a 2-6-6-0 wheel arrangement in branch line service.[2][4][5]
Contents |
The Class MJ 2-6-6-0 Mallet articulated compound steam locomotive was designed by D.A. Hendrie, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1910 to 1922. Ten of these branch line locomotives were ordered from Maffei but, as a result of the outbreak of World War I, only two could be delivered from Germany in 1914, numbered 1651 and 1652 with works numbers 3452 and 3453.[2][5]
The order for the remaining eight was then transferred to North British Locomotive Company (NBL) in Scotland, who delivered them in 1917, numbered 1653 to 1660.[2][5]
The works numbers for the eight NBL built locomotives are recorded as 21248 to 21255, but these numbers are in conflict with the NBL works numbers 21246 to 21275 that were allocated to thirty 2-8-2T locomotives, numbered 5381 to 5410 and built by NBL in 1917 for the Paris-Orleans railway in France.[1][2][3]
After the cessation of hostilities in 1918, Maffei approached the SAR and requested that the balance of the original order, which had been built in 1914 but could not be delivered because of the war, also be accepted. These eight locomotives were subsequently delivered in 1921, numbered 1674 to 1681 with works numbers 3454 to 3461.[2][5][6]
They were superheated and had Walschaerts valve gear. Unlike most of the other SAR Mallet classes which had round top fireboxes, they had Belpaire fireboxes.[2][5]
In a compound locomotive steam is expanded in phases. After being expanded in a high pressure cylinder and having then lost pressure and given up part of its heat, it is exhausted into a larger volume low pressure cylinder for secondary expansion, after which it is exhausted through the smokebox. By comparison, in the more usual arrangement of simple expansion, steam is expanded just once in any one cylinder before being exhausted through the smokebox.[2][7]
In the compound Mallet locomotive, the rear set of coupled wheels are driven by the smaller high pressure cylinders which are fed steam from the steam dome. Their spent steam is then fed to the larger low pressure cylinders that drive the front set of coupled wheels.[2][5]
With its light axle loading, the Class MJ was intended for branch line working. Most of them were placed in service in the Eastern Cape, but four went to Natal and are believed to have worked on the Eshowe branch line.[2][5]
Two of the Class MJ locomotives, NBL built number 1655 and Maffei built number 1674, had the distinction of being the last two Mallet locomotives to remain in SAR service. They were scrapped in the East London workshops in 1962 after having worked on the branch line between Amabele and Umtata in the Transkei and then having spent their last days in shunting service in East London.[8]
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