South African Class 12B 4-8-2

The South African Railways Class 12B 4-8-2 of 1920 was a steam locomotive.

South African Class 12B & 12R 4-8-2
Class 12R no. 1931 at Port Elizabeth sheds, with Belpaire firebox, c. 1930
Type and origin
♠ Class 12B as built with a Belpaire firebox
♥ Class 12R rebuilt with a Watson Standard boiler
Power typeSteam
DesignerSouth African Railways
(D.A. Hendrie)
BuilderBaldwin Locomotive Works
Serial number52476, 52558-52559, 52583-52584, 52649-52651, 52690-52693, 52712-52713, 52723-52724, 52754-52767
ModelClass 12B
Build date1920
Total produced30
Specifications
Configuration:
​
 • Whyte4-8-2 (Mountain)
 • UIC♠ 2′D1’n2 - ♥ 2′D1’h2
Driver2nd coupled axle
Gauge3 ft 6 in (1,067 mm) Cape gauge
Leading dia.28 1⁄2 in (724 mm)
Coupled dia.51 in (1,295 mm)
Trailing dia.33 in (838 mm)
Tender wheels34 in (864 mm)
Wheelbase58 ft 3 3⁄4 in (17,774 mm)
 • Engine31 ft 9 1⁄2 in (9,690 mm)
 • Leading6 ft 2 in (1,880 mm)
 • Coupled13 ft 6 in (4,115 mm)
 • Tender16 ft 9 in (5,105 mm)
 • Tender bogie4 ft 7 in (1,397 mm)
Length:
​
 • Over couplers66 ft 8 in (20,320 mm)
Height♠ 12 ft 10 in (3,912 mm)
♥ 12 ft 7 1⁄2 in (3,848 mm)
Frame typePlate
Axle load♠ 16 LT 15 cwt (17,020 kg)
♥ 17 LT 9 cwt (17,730 kg)
 • Leading♠ 15 LT 13 cwt (15,900 kg)
♥ 16 LT 2 cwt (16,360 kg)
 • 1st coupled♠ 16 LT 13 cwt (16,920 kg)
♥ 16 LT 15 cwt (17,020 kg)
 • 2nd coupled♠ 16 LT 15 cwt (17,020 kg)
♥ 17 LT 9 cwt (17,730 kg)
 • 3rd coupled♠ 16 LT 14 cwt (16,970 kg)
♥ 16 LT 17 cwt (17,120 kg)
 • 4th coupled♠ 16 LT 15 cwt (17,020 kg)
♥ 16 LT 15 cwt (17,020 kg)
 • Trailing♠ 12 LT 4 cwt (12,400 kg)
♥ 11 LT 16 cwt (11,990 kg)
 • Tender bogieBogie 1: 27 LT 10 cwt (27,940 kg)
Bogie 2: 23 LT 11 cwt (23,930 kg)
 • Tender axle13 LT 15 cwt (13,970 kg)
Adhesive weight♠ 66 LT 17 cwt (67,920 kg)
♥ 67 LT 16 cwt (68,890 kg)
Loco weight♠ 94 LT 14 cwt (96,220 kg)
♥ 95 LT 14 cwt (97,240 kg)
Tender weight51 LT 1 cwt (51,870 kg)
Total weight♠ 145 LT 15 cwt (148,100 kg)
♥ 146 LT 15 cwt (149,100 kg)
Tender typeMP1 (2-axle bogies)
MP, MP1, MR, MS, MT, MT1, MT2, MX, MY, MY1 permitted
Fuel typeCoal
Fuel capacity10 LT (10,160 kg)
Water cap4,250 imp gal (19,300 l)
Firebox type♠ Belpaire - ♥ Round-top
 • Firegrate area♠ 40 sq ft (3.7 m2)
♥ 37 sq ft (3.4 m2)
Boiler:
​
 • ModelWatson Standard no. 2
 • Pitch♠ 7 ft 7 in (2,311 mm)
♥ 7 ft 8 1⁄4 in (2,343 mm)
 • Diameter♠♥ 5 ft 7 1⁄2 in (1,714 mm)
 • Tube plates♠ 20 ft (6,096 mm)
♥ 19 ft 4 in (5,893 mm) steel
♥ 19 ft 3 5⁄8 in (5,883 mm)
 • Small tubes♠ 139: 2 1⁄4 in (57 mm)
♥ 87: 2 1⁄2 in (64 mm)
 • Large tubes♠ 24: 5 1⁄2 in (140 mm)
♥ 30: 5 1⁄2 in (140 mm)
Boiler pressure♠♥ 190 psi (1,310 kPa)
Safety valve♠ Ramsbottom - ♥ Pop
Heating surface♠ 2,488 sq ft (231.1 m2)
♥ 2,075 sq ft (192.8 m2)
 • Tubes♠ 2,328 sq ft (216.3 m2)
♥ 1,933 sq ft (179.6 m2)
 • Firebox♠ 160 sq ft (15 m2)
♥ 142 sq ft (13.2 m2)
Superheater:
​
 • Heating area♠ 574 sq ft (53.3 m2)
♥ 492 sq ft (45.7 m2)
CylindersTwo
Cylinder size22 1⁄2 in (572 mm) bore
26 in (660 mm) stroke
Valve gearWalschaerts
Valve typePiston
CouplersJohnston link-and-pin
AAR knuckle (1930s)
Performance figures
Tractive effort♠♥ 36,780 lbf (163.6 kN) @ 75%
Career
OperatorsSouth African Railways
ClassClass 12B & 12R
Number in class30
Numbers1931-1960
Delivered1920
First run1920
Withdrawnc. 1984
The leading coupled axle had flangeless wheels

In 1920, the South African Railways placed thirty Class 12B steam locomotives with a 4-8-2 Mountain type wheel arrangement in service.[1][2]

Manufacturer

In May 1920, an additional thirty locomotives, built to the Class 12 design of SAR Chief Mechanical Engineer (CME) D.A. Hendrie, were delivered to the South African Railways (SAR) from Baldwin Locomotive Works in the United States of America. Most of them were erected in the SAR workshops, but a few were contracted to James Brown and Company at Durban for erection. Even though they were very similar to the second and subsequent orders of the Class 12 which was also designed specifically for the Midland System, they were classified separately as Class 12B and numbered in the range from 1931 to 1960. Like the Class 12, they were also built with plate frames, Walschaerts valve gear and Belpaire fireboxes.[1][2][3][4]

Classification
D.A. Hendrie

The separate 12B classification has been ascribed to the fact that the wheelbase of the leading bogie was 2 inches (51 millimetres) longer than on the original Class 12 locomotives. This was probably not the reason, bearing in mind that only the first eight out of altogether 46 Class 12 locomotives were built with leading bogies with a 6 feet (1,829 millimetres) wheelbase, while the other thirty-eight all had leading bogies with a 6 feet 2 inches (1,880 millimetres) wheelbase, the same as the Class 12B. More likely, the separate classification was simply based on the fact that the Class 12 was British-built while the Class 12B was American-built.[1][2][3]

Watson Standard boilers

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. Such Watson Standard reboilered locomotives were reclassified by adding an "R" suffix to their classification.[2][5][6]

All thirty Class 12B locomotives were eventually reboilered with Watson Standard no. 2 boilers. In the process, they were also equipped with Watson cabs with their distinctive slanted fronts, compared to the conventional vertical fronts of their original cabs. Upon reboilering, the unknown original reason for the separate classification was ignored and instead of becoming Class 12BR, the reboilered locomotives were reclassified to Class 12R along with the reboilered Class 12 locomotives.[1][5][6][7]

Their original Belpaire saturated steam boilers were fitted with Ramsbottom safety valves, while the Watson Standard superheated steam boiler was fitted with Pop safety valves.[5][6]

Service

South African Railways

All thirty locomotives were placed in service on the Cape Midland to work on the mainline out of Port Elizabeth, where they largely remained until being withdrawn after more than sixty years in service. Even though they were not designed to be mixed traffic locomotives, they saw service on both passenger and goods working. Until the Class 15F arrived on the Midland, the mainline was ruled by these locomotives. Later, in spite of their small 51 inches (1,295 millimetres) diameter coupled wheels, they were comfortable at 60 miles per hour (97 kilometres per hour) when employed on the mainline in tandem with the larger Class 15F.[2][3][4][8]

The Class 12Rs saw mainline work until well into 1969, when the arrival of new Class 33-400 diesel-electrics brought almost fifty years of mainline service to an end. The entire Class gave more than fifty years of service before the first one was withdrawn.[4]

Even in their twilight years, these locomotives still saw mainline service on the Klipplaat run and as local goods haulers around Port Elizabeth.[8]

Industrial

For some reason, few Class 12Rs ended up in industrial service despite their evident suitability for such work. Of the ex Class 12B locomotives, only no. 1936 was sold to Enyati Colliery and later became Western Holdings Gold Mine's no. 8.[7]

Works numbers

The Baldwin works numbers did not run consecutively for the whole order and are shown in the table.[2][3]

Preservation
ClassNumberWorks nmrTHF / PrivateLeaselend / OwnerCurrent LocationOutside South Africa?
12R1865BP 5994PrivateKimberley Locomotive Depot
12R1947BALDWIN 52754THFReefsteamersGermiston Locomotive Depot
12R1505NBL 20176THFUmgeni Steam RailwayKloofstation (Inchaga)
12R1510NBL 20812PrivateCreighton Station
12A2111NBL 22751THFBloemfontein Locomotive Depot
12AR1535NBL 21753THFReefsteamersGermiston Locomotive Depot

Illustration
  • Class 12R no. 1939 on the shunt at New Brighton, 31 March 1979

References
  1. Espitalier, 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. p. 780.
  2. Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 10–11, 54–56. ISBN 0869772112.
  3. Holland, D. F. (1972). Steam Locomotives of the South African Railways. 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 38–41, 82. ISBN 978-0-7153-5427-8.
  4. Soul of A Railway, System 3, Part 10: The Midland Main Line, Part 2, Paterson to Alicedale. Captions 4, 31 (Accessed on 15 February 2017)
  5. South 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. p. 43.
  6. South African Railways & Harbours/Suid Afrikaanse Spoorweë en Hawens (15 Aug 1941). Locomotive Diagram Book/Lokomotiefdiagramboek, 2'0" & 3'6" Gauge/Spoorwydte, Steam Locomotives/Stoomlokomotiewe. SAR/SAS Mechanical Department/Werktuigkundige Dept. Drawing Office/Tekenkantoor, Pretoria. pp. 6a-7a, 41, 43.
  7. Durrant, A. E. (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. p. 59. ISBN 0715386387.
  8. Soul of A Railway, System 3, Part 9: The Midland Main Line, Part 1, Port Elizabeth to Paterson. Captions 14, 52, 58 (Accessed on 5 February 2017)
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