The South African Railways Class 12A 4-8-2 of 1919 was a steam locomotive.
Between 1919 and 1929, the South African Railways placed 67 Class 12A steam locomotives with a 4-8-2 Mountain type wheel arrangement in service. Between 1947 and 1953, eight were also built for industrial use.[1][2][3]
Manufacturers
The Class 12A was the final locomotive design by D.A. Hendrie, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1910 to 1922, and one of his finest. It was an improved and larger version of his Class 12 locomotive, with larger diameter cylinders to increase tractive effort and a redesigned boiler.[1][2]
The first twenty were built by NBL and were delivered in 1919, numbered in the range from 1520 to 1539.[1][4][5]
These were followed by another fifteen from NBL, which were built in late 1919 but were only delivered in 1921, numbered in the range from 2111 to 2125.[1][4]
The Henschel-built locomotives only arrived several years later. Six were delivered in 1928 and numbered in the range from 1540 to 1545.[1][6][7]
Another thirteen were delivered by Henschel in 1929, numbered in the ranges from 1546 to 1550 and 2103 to 2110, filling the gaps in the numbering sequence.[1][7]
The final thirteen, once again built by NBL, were also delivered in 1929 and numbered in the range from 2126 to 2138.[1][4][8]
Characteristics
At the time, these locomotives were of the maximum size permissible for the Mountain type on Cape gauge. They were designed primarily to supplement the Class 12 locomotives which were already working on the coal line between Witbank and Germiston. Since these engines had a slightly heavier axle load than the predecessor Class 12, it was foreseen that they would be able to take a slightly increased load on the Witbank-Germiston section.[1][5]
D.A. Hendrie
The locomotives were built on 1+1⁄2-inch thick (38-millimetre) plate frames. They were superheated and had piston valves, Walschaerts valve gear and Belpaire fireboxes which included combustion chambers. The boilers of the first two batches of 1919 and 1921 were equipped with Ramsbottom safety valves, while works pictures of the remainder show that they were equipped with Ross pop safety valves. The feedwater supply of the third and subsequent batches was by a top feed arrangement through copper pipes which were run from the running boards on each side to the top of the boiler ahead of the steam dome.[1]
The original Class 12A superheater header was arranged with the Gresley type air valve which was introduced to prevent the risk of superheater elements being burned or damaged by overheating while engines were drifting. The valve automatically opened when the regulator was closed and allowed outside air to be drawn into the superheater elements. Even though experience showed that the heated air which then entered the steam chests and cylinders was harmful to cylinder lubrication with no apparent effect on the life of the superheater elements, it was some years before the use of these air valves was finally discontinued.[1]
The first two batches, delivered in 1919 and 1921, were equipped with the Johnston link-and-pin couplers which had been in use since the establishment of the Cape Government Railways in 1873. By the time the third batch arrived in 1928, the SAR had begun to convert its Cape Gauge rolling stock to AAR knuckle couplers. The third to fifth batches were therefore delivered with the new coupling system.[8][9][10]
Tenders
The locomotives were delivered new with two tender types, the Types MP1 and MT. While sources are unclear about which batches of the Class 12A were delivered with which tender type, builder's works photographs show the NBL-built locomotives of 1919 and 1921 with Type MP1 tenders, and the Henschel-built and subsequent NBL-built locomotives with Type MT tenders.[1][6][8][9][10]
Type MP1 tender
On the Type MP1 tender, the top of its coal bunker sides were distinctly separate, mounted within the top edging of the water tank. It had a fuel capacity of 10 long tons (10.2 tonnes) and a water capacity of 4,250 imperial gallons (19,300 litres), with a 13 long tons 15 hundredweight (13,970 kilograms) axle load.[8][9][10]
Many of these tenders were subsequently rebuilt to smooth-sided Type MR tenders with a 4,600 imperial gallons (20,900 litres) water capacity and a 13 long tons 14 hundredweight (13,920 kilograms) axle load.[9][10]
Type MT tender
The heavier Type MT tender had smooth sides all the way to the top of the coal bunker. It had a fuel capacity of 12 long tons (12.2 tonnes) and a water capacity of 6,000 imperial gallons (27,300 litres), with a 16 long tons 11 hundredweight (16,820 kilograms) axle load.[8][9][10]
Reboilering
During the 1930s, many serving locomotives were reboilered with a standard boiler type designed by then CME A.G. Watson as part of his standardisation policy. In the process, they were then also equipped with Watson cabs with their distinctive slanted fronts, compared to the conventional vertical fronts of the original cabs. Such Watson Standard reboilered locomotives were reclassified by adding an "R" suffix to their classification.[2][8][9][10]
When Class 12A locomotives numbers 1540 and 2135 became the first to be reboilered in 1943, however, none of the Watson Standard boilers were deemed suitable since the Watson Standard no. 2 series were too small, while the no. 3 series were too large. A special boiler was therefore designed for them by Dr. M.M. Loubser, the CME at the time. These boilers did not conform to any of the Watson Standard boilers and were a totally new type of rather massive proportions which, on a locomotive with relatively small coupled wheels, created an impression of great power. Certain features common to the Watson Standard boilers were incorporated in the design, however, since it was deemed necessary to have the greatest possible degree of interchangeability of parts with those of the Watson Standard boilers. The boiler size was between that of the Watson Standard numbers 2 and 3 boilers.[1][2][8][11]
Unlike the original Class 12A boilers, initial and in-service repair cost considerations led to the Loubser boiler being built without a combustion chamber. The round-top firebox was radially stayed and the first two rows of stays were flexible. Similar stays were fitted in the side, back and throat plates and in the breaking zones. There were eight cross stays over the top of the firebox, which was of steel.[1][2][8]
The original Belpaire boilers were fitted with Ramsbottom safety valves while, like the Watson Standard boilers, the Loubser boiler was fitted with two 3+1⁄2 inches (89 millimetres) Ross pop safety valves. Feedwater was supplied by two Davies and Metcalf injectors through a top-feed arrangement. At the firebox, the boiler was carried by a vertical transverse plate at the back and at the two front corners by sliding grease-lubricated shoes which rested on gunmetal liner plates which, in turn, were fixed to specially-designed steel brackets welded to the inside of the bridle casting. The boiler barrel was attached to the engine frame by four diaphragm plates, bolted to "T" sections which were riveted to the barrel.[1]
Altogether 44 Class 12A locomotives were eventually reboilered with Loubser boilers and reclassified to Class 12AR. During the reboilering, which included the installation of Watson cabs, the locomotives were also equipped with a longer smokebox which resulted in the distinctive appearance of the Class 12AR. Like the Watson Standard boilers, the Loubser boilers also had the distinctive rectangular regulator cover just to the rear of the chimney. In the case of the Classes 12A and 12AR locomotives, three even more obvious differences are the extended smokebox, the Watson cab and the absence of the Belpaire firebox hump between the cab and boiler on the reboilered locomotives.[9][10]
The reboilered locomotives were considered by some enginemen to be inferior steamers compared to the as-built engines. A shortened version of Loubser's Class 12AR boiler was later used on the new Class S1 shunting locomotives.[3]
Service
South African Railways
When new, the Class 12A locomotives were placed in service hauling coal on the section from Witbank to Germiston. The unreboilered locomotives spent a large part of their working lives in Transvaal, mainly in Western Transvaal and shedded at Springs and Germiston, a few in Eastern Transvaal and shedded at Nelspruit and Waterval Boven, and one at De Aar in the Cape Province. The class also served in Natal during the late 1920s, probably after the arrival in numbers of the Class 15CA in 1929. Here they were worth two more coaches than a Class 14 on the 1921 mainline between Durban and Pietermaritzburg. A Class 12A locomotive was in charge of the last steam-hauled mainline passenger train to depart from Durban station after electric traction reached Durban from Pietermaritzburg during 1936. In 1977, all the remaining Class 12A locomotives were relocated to the Cape Northern system for shunting at De Aar and at Beaconsfield in Kimberley.[2][3][5][12]
The more numerous reboilered Class 12AR locomotives worked throughout most parts of South Africa, being shedded at Kimberley, De Aar, Port Elizabeth and East London in the Cape Province, Glencoe and Newcastle in Natal, Klerksdorp in Transvaal and Kroonstad in the Orange Free State. East London and Port Elizabeth each received four, the latter being allocated engine numbers 1544, 1545, 2125 and 2129 for use on the fast Saturday morning passenger trains to Cape Town.[2][3]
The Classes 12A and 12AR versions both proved to be very successful engines which performed well, with low repair costs. Modifications in design of details after entering service were negligible.[1]
Industrial service
None of the SAR Class 12A or Class 12AR locomotives were sold into industrial service, but between 1947 and 1953 eight Class 12A locomotives, similar to the unreboilered SAR locomotives but without superheaters, were built new for industrial service by NBL.[3]
Works numbers
The builders, years built, works numbers, reboilering particulars and original tender types are listed in the table.[9][10]
Class 12A 4-8-2 Builders, works numbers, class & original tender type
Builder
Year built
Works no.
SAR no.
Class
Tender type
NBL
1919
21738
1520
12AR
MP1
NBL
1919
21739
1521
12A
MP1
NBL
1919
21740
1522
12AR
MP1
NBL
1919
21741
1523
12AR
MP1
NBL
1919
21742
1524
12A
MP1
NBL
1919
21743
1525
12A
MP1
NBL
1919
21744
1526
12A
MP1
NBL
1919
21745
1527
12A
MP1
NBL
1919
21746
1528
12A
MP1
NBL
1919
21747
1529
12AR
MP1
NBL
1919
21748
1530
12AR
MP1
NBL
1919
21749
1531
12A
MP1
NBL
1919
21750
1532
12AR
MP1
NBL
1919
21751
1533
12A
MP1
NBL
1919
21752
1534
12AR
MP1
NBL
1919
21753
1535
12AR
MP1
NBL
1919
21754
1536
12AR
MP1
NBL
1919
21755
1537
12AR
MP1
NBL
1919
21756
1538
12A
MP1
NBL
1919
21757
1539
12A
MP1
Henschel
1928
21046
1540
12AR
MT
Henschel
1928
21047
1541
12AR
MT
Henschel
1928
21048
1542
12AR
MT
Henschel
1928
21049
1543
12AR
MT
Henschel
1928
21050
1544
12AR
MT
Henschel
1928
21051
1545
12AR
MT
Henschel
1929
21428
1546
12AR
MT
Henschel
1929
21429
1547
12A
MT
Henschel
1929
21430
1548
12A
MT
Henschel
1929
21431
1549
12AR
MT
Henschel
1929
21432
1550
12AR
MT
Henschel
1929
21433
2103
12AR
MT
Henschel
1929
21434
2104
12AR
MT
Henschel
1929
21435
2105
12AR
MT
Henschel
1929
21436
2106
12A
MT
Henschel
1929
21437
2107
12A
MT
Henschel
1929
21438
2108
12AR
MT
Henschel
1929
21439
2109
12AR
MT
Henschel
1929
21440
2110
12AR
MT
NBL
1921
22751
2111
12A
MP1
NBL
1921
22752
2112
12AR
MP1
NBL
1921
22753
2113
12AR
MP1
NBL
1921
22754
2114
12A
MP1
NBL
1921
22755
2115
12AR
MP1
NBL
1921
22756
2116
12AR
MP1
NBL
1921
22757
2117
12A
MP1
NBL
1921
22758
2118
12AR
MP1
NBL
1921
22759
2119
12AR
MP1
NBL
1921
22760
2120
12AR
MP1
NBL
1921
22761
2121
12AR
MP1
NBL
1921
22762
2122
12AR
MP1
NBL
1921
22763
2123
12A
MP1
NBL
1921
22764
2124
12AR
MP1
NBL
1921
22765
2125
12AR
MP1
NBL
1929
23891
2126
12A
MT
NBL
1929
23892
2127
12AR
MT
NBL
1929
23893
2128
12AR
MT
NBL
1929
23894
2129
12AR
MT
NBL
1929
23895
2130
12A
MT
NBL
1929
23896
2131
12AR
MT
NBL
1929
23897
2132
12AR
MT
NBL
1929
23898
2133
12A
MT
NBL
1929
23899
2134
12A
MT
NBL
1929
23900
2135
12AR
MT
NBL
1929
23901
2136
12AR
MT
NBL
1929
23902
2137
12AR
MT
NBL
1929
23903
2138
12A
MT
Preservation
Class
Number
Works nmr
THF / Private
Leaselend / Owner
Current Location
Outside South Africa
?
12R
1865
BP 5994
Private
Kimberley Locomotive Depot
12R
1947
BALDWIN 52754
THF
Reefsteamers
Germiston Locomotive Depot
12R
1505
NBL 20176
THF
Umgeni Steam Railway
Kloofstation (Inchaga)
12R
1510
NBL 20812
Private
Creighton Station
12A
2111
NBL 22751
THF
Bloemfontein Locomotive Depot
12AR
1535
NBL 21753
THF
Reefsteamers
Germiston Locomotive Depot
Illustration
NBL builder's picture of no. 1520, 1st batch, with Type MP1 tender, c. 1919. Note the absence of a top-feed feedwater supply.
No. 2111, 2nd batch, with Ramsbottom safety valves and Type MP1 tender, c. 1921
Henschel builder's picture of no. 1543, 3rd batch, with pop valves, top-feed feedwater supply and Type MT tender, c. 1928
Henschel builder's picture of no. 1548, 4th batch, with pop valves and Type MT tender, c. 1929
NBL builder's picture of no. 2131, 5th batch, with pop valves and Type MT tender, c. 1929
NBL-built 12A no. 1526 at De Aar, with Type MR tender, 6 April 1979
Henschel-built 12A no. 1547 at Visrivier, 14 April 1979
Henschel-built 12AR no. 1542 at Kimberley, 27 March 1983
^ abcdefghijklmnopEspitalier, T.J.; Day, W.A.J. (1945). The Locomotive in South Africa - A Brief History of Railway Development. Chapter VII - South African Railways (Continued). South African Railways and Harbours Magazine, October 1945. pp. 779-783.
^ abcdefghPaxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 10–11, 55. ISBN0869772112.
^ abDulez, Jean A. (2012). Railways of Southern Africa 150 Years (Commemorating One Hundred and Fifty Years of Railways on the Sub-Continent – Complete Motive Power Classifications and Famous Trains – 1860–2011) (1st ed.). Garden View, Johannesburg, South Africa: Vidrail Productions. pp. 106–108. ISBN9 780620 512282.
^ abHenschel-Lieferliste (Henschel & Son works list), compiled by Dietmar Stresow
^ abcdefghHolland, D. F. (1972). Steam Locomotives of the South African Railways. Vol. 2: 1910-1955 (1st ed.). Newton Abbott, England: David & Charles. pp. 38–40, 102–103. ISBN978-0-7153-5427-8.
^ abcdefghSouth African Railways & Harbours/Suid Afrikaanse Spoorweë en Hawens (15 Aug 1941). Locomotive Diagram Book/Lokomotiefdiagramboek, 3'6" Gauge/Spoorwydte. SAR/SAS Mechanical Department/Werktuigkundige Dept. Drawing Office/Tekenkantoor, Pretoria. pp. 43-44.
^Espitalier, T.J.; Day, W.A.J. (1946). The Locomotive in South Africa - A Brief History of Railway Development. Chapter VII - South African Railways (Continued). South African Railways and Harbours Magazine, Jul 1946. p. 542.