South African Class 12 4-8-2

South African Class 12 & 12R 4-8-2

No. 1505 crossing the Great Fish River near Nelland, between Cradock and Cookhouse, 22 April 1981

Type and origin ♠ Class 12 as built with a Belpaire firebox ♥ Class 12R rebuilt with a Watson Standard boiler ♣ Steel firebox - ♦ Copper firebox ʘ No. 1494-1501 - ʘ All others Power type Steam Designer South African Railways (D.A. Hendrie) Builder North British Locomotive Company Beyer, Peacock and Company Order number BP 01830 Serial number NBL 19593-19596, 19684-19687, 20173-20180, 20812-20821 BP 5988-5997, 6003-6012 Model Class 12 Build date 1912-1921 Total produced 46

Specifications Configuration 4-8-2 (Mountain) Driver axle 2nd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia Coupled dia 51 in (1,295 mm) Trailing dia 33 in (838 mm) Tender wheels 34 in (864 mm) Wheelbase ʘ ʘ  • Engine ʘ ʘ  • Leading ʘ 6 ft (1,829 mm) ʘ 6 ft 2 in (1,880 mm)  • Coupled 13 ft 6 in (4,115 mm)  • Tender 16 ft 9 in (5,105 mm)  • Tender bogie 4 ft 7 in (1,397 mm) Length:  • Over couplers ʘ ʘ Height ♠ 12 ft 10 in (3,912 mm) ♥ Frame type Plate Axle load ♠ ♥♣ ♥♦  • Leading ♠ ♥♣ ♥♦  • 1st coupled ♠ ♥♣ ♥♦  • 2nd coupled ♠ ♥♣ ♥♦  • 3rd coupled ♠ ♥♣ ♥♦  • 4th coupled ♠ ♥♣ ♥♦  • Trailing ♠ ♥♣ ♥♦  • Tender bogie Bogie 1: Bogie 2:  • Tender axle Adhesive weight ♠ ♥♣ ♥♦ Loco weight ♠ ♥♣ ♥♦ Tender weight w/o Loco & tender weight ♠ ♥♣ ♥♦ Tender type MP1 (2-axle bogies) MP, MP1, MR, MS, MT, MT1, MT2, MX, MY, MY1 permitted Fuel type Coal Fuel capacity 10 LT (10.2 t) Water cap Boiler ♥ Watson Standard no. 2  • Pitch ♠ 7 ft 7 in (2,311 mm) ♥  • Diameter ♠♥  • Tube plates ♠ 20 ft (6,096 mm) ♥♣ 19 ft 4 in (5,893 mm) ♥♦  • Small tubes ♠ 139: ♥ 87:  • large tubes ♠ 24: ♥ 30:  • Firebox type ♠ Belpaire - ♥ Round-top Boiler pressure 190 psi (1,310 kPa) Safety valve ♠ Ramsbottom ♥ Pop Firegrate area ♠ 40 sq ft (3.7 m2) ♥ 37 sq ft (3.4 m2) 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) Cylinders Two Cylinder size bore 26 in (660 mm) stroke Valve gear Walschaerts Valve type Piston Couplers Bell link-and-pin AAR knuckle (1950s)

Performance figures Tractive effort ♠♥ 36,780 lbf (163.6 kN) @ 75%

Career Operators South African Railways Class Class 12 & 12R Number in class 46 Numbers 1494-1519, 1859-1878 Delivered 1912-1921 First run 1912

The leading coupled axle had flangeless wheels

The South African Railways Class 12 4-8-2 of 1912 was a steam locomotive.

Between April 1912 and 1922, the South African Railways placed altogether 46 Class 12 steam locomotives with a 4-8-2 Mountain type wheel arrangement in goods train service.

Manufacturers

Design work commenced in 1910 for a new heavy goods engine, for use on the heavy coal service between Witbank and Germiston. The resulting Class 12 was the first locomotive design to originate from the newly established South African Railways (SAR) in 1912. It was, in effect, an enlarged version of the already successful Class 3B, which had also been designed by SAR Chief Mechanical Engineer (CME) D.A. Hendrie during his years on the Natal Government Railways.

File:D.A. Hendrie.jpg

D.A. Hendrie

Orders for the first eight locomotives in the Class were placed on 22 March 1911. They were built in two batches of four, the first of which was delivered from North British Locomotive Company (NBL) in April 1912, numbered in the range from 1494 to 1497. The second batch, numbered in the range from 1498 to 1501, followed shortly thereafter. These first eight locomotives had bogies with a 6 feet (1,829 millimetres) wheelbase.

These engines were followed by another eight in August 1913, numbered in the range from 1502 to 1509, and ten more in January 1915, numbered in the range from 1510 to 1519, all built by NBL. These and all subsequent Class 12 locomotives had leading bogies with a 6 feet 2 inches (1,880 millimetres) wheelbase. These locomotives were also 2 inches (51 millimetres) longer between couplers than the first eight.

In June 1921, Beyer, Peacock and Company (BP) delivered the final twenty Class 12 locomotives, built in two batches of ten and numbered in the range from 1859 to 1878.

Characteristics

When the Class 12 was introduced, it was the largest non-articulated engine in South Africa, and possibly in the world, on railways of less than gauge. The first eight locomotives had cast steel frames for the leading bogies, with three-point suspension links, similar to those of the Class 3B. On subsequent engines, this arrangement was modified to the two-point swing-link type, controlled by laminated side springs, a design Hendrie adhered to in all his later engines.

The locomotives were built with plate frames, Walschaerts valve gear, superheaters and Belpaire fireboxes. It was designed to have as short a fixed wheelbase as possible and the close spacing of the coupled wheels necessitated specially designed brake hangers outside the wheels. As built, the leading coupled axle had flangeless wheels, but it was subsequently retyred with flanges.

The NBL-built locomotives were very similar in appearance to the Class 3B, with running boards which curved down below the cab at the rear and down to meet the buffer beam at the front. The only major design alteration between the NBL and BP locomotive orders was to the cab. With the earlier cabs, many drivers wore leather guards on their left legs to protect them from the heat when the fire door was open. The BP-built locomotives had larger and more spacious cabs to provide increased comfort for the enginemen, and running boards which ran straight through to the rear buffer beams.

Tender

The Class 12 locomotives introduced a new Type MP1 tender with a coal capacity of 10 long tons (10.2 tonnes) and a water capacity of . This marked the introduction of a standard tender type which, with few modifications, was eventually to be used on all the Hendrie-designed locomotives. The tender bogies were interchangeable with other tender types operating in the Transvaal and Orange Free State at the time, while its centre longitudinal frame members were carried through unbroken from buffer to buffer. The arrangement of the buffing gear between engine and tender was the result of a long series of experiments, made with the view to avoid excessive fore and aft action between engine and tender while running at high speed.

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.

From 1935, all 46 Class 12 locomotives were eventually reboilered with Watson Standard no. 2 boilers and reclassified to Class 12R. In the process, they were also equipped with Watson cabs, with their distinctive slanted fronts to facilitate access to the firebox side stays, compared to the vertical fronts of the original cabs. In the case of the NBL-built locomotives, the reboilered engines were also fitted with running boards which continued straight through underneath their cabs. The new boilers raised the engine's boiler pitch by .

At the same time, the footplate was extended at the back end, in the form of a platform overhanging the tender, which dispensed with the usual fall plate between engine and tender. A handrail was provided, passing round the back of the footplate without impeding the stoker's access to the coal bunker, an arrangement which was subsequently adopted as standard practice. It gave the stoker a much more stable foothold and reduced the risk to the crew in the event of a broken intermediate drawbar. Many of the reboilered locomotives also received new Type MT tenders with a coal capacity of 12 long tons (12.2 tonnes) and a water capacity of .

Their original boilers were fitted with Ramsbottom safety valves, while the Watson Standard boilers were fitted with Pop safety valves. An obvious difference between an original and a Watson Standard reboilered locomotive is usually a rectangular regulator cover, just to the rear of the chimney on the reboilered locomotive. In the case of the Class 12 engines, two even more obvious differences are the Watson cab and the absence of the Belpaire firebox hump between the cab and boiler on the reboilered locomotives.

Service

South African Railways

The locomotives gave outstanding performance with low maintenance costs. They proved to be most successful in the service they had been designed for, handling loads of 1,400 tons and doing the return trip between Witbank and Germiston in one day. This compared favourably with the 2-6-6-0 and 2-6-6-2 Mallet locomotives which, while able to handle 1,600 tons, could not make a round trip in one day.

They were also used around Ladysmith in Natal. In the 1940s, the Natal locomotives were relocated to the Orange Free State.

By the 1970s, some were allocated to the Cape Midland system, stationed at Sydenham in Port Elizabeth for use as dock shunters and for yard work in the New Brighton marshalling yards. In the Orange Free State, some were shedded at Bloemfontein and at Bethlehem, all in shunting service. The Transvaal had a large contingent, stationed at Springs, Germiston and Krugersdorp, also mainly used for shunting.

Zambian Railways

Ten Class 12R locomotives were briefly hired to the Zambian Railways during a peak in that country's perpetual diesel motive power crisis in 1980, but were soon returned, since the Zambian knowledge base on steam maintenance had virtually disappeared by then.

Industrial

For some reason, few Class 12 locomotives ended up in industrial service, despite their evident suitability for such work. Only five were sold into private service.

• NBL-built no. 1510 went to Umgala Colliery at Utrecht as no. 7.
• NBL-built no. 1511 went to Middelplaas Manganese as no. SL001.
• NBL-built no. 1515 went first to Tweefontein Colliery and later to Witbank Consolidated Coal Mine.
• BP-built no. 1863 and 1864 went to Middelplaas Manganese as numbers SL002 and SL003 respectively.

Works numbers

The Class 12 builders, years built and works numbers are listed in the table.

Class 12 & 12R 4-8-2
Builders, years built, works numbers and bogie wheelbase

Builder	Year built	Works No.	Bogie wheelbase	SAR No.
NBL	1912	19593	6 ft (1,829 mm)	1494
NBL	1912	19594	6 ft (1,829 mm)	1495
NBL	1912	19595	6 ft (1,829 mm)	1496
NBL	1912	19596	6 ft (1,829 mm)	1497
NBL	1912	19684	6 ft (1,829 mm)	1498
NBL	1912	19685	6 ft (1,829 mm)	1499
NBL	1912	19686	6 ft (1,829 mm)	1500
NBL	1912	19687	6 ft (1,829 mm)	1501
NBL	1913	20173	6 ft 2 in (1,880 mm)	1502
NBL	1913	20174	6 ft 2 in (1,880 mm)	1503
NBL	1913	20175	6 ft 2 in (1,880 mm)	1504
NBL	1913	20176	6 ft 2 in (1,880 mm)	1505
NBL	1913	20177	6 ft 2 in (1,880 mm)	1506
NBL	1913	20178	6 ft 2 in (1,880 mm)	1507
NBL	1913	20179	6 ft 2 in (1,880 mm)	1508
NBL	1913	20180	6 ft 2 in (1,880 mm)	1509
NBL	1914	20812	6 ft 2 in (1,880 mm)	1510
NBL	1914	20813	6 ft 2 in (1,880 mm)	1511
NBL	1914	20814	6 ft 2 in (1,880 mm)	1512
NBL	1914	20815	6 ft 2 in (1,880 mm)	1513
NBL	1914	20816	6 ft 2 in (1,880 mm)	1514
NBL	1914	20817	6 ft 2 in (1,880 mm)	1515
NBL	1914	20818	6 ft 2 in (1,880 mm)	1516
NBL	1914	20819	6 ft 2 in (1,880 mm)	1517
NBL	1914	20820	6 ft 2 in (1,880 mm)	1518
NBL	1914	20821	6 ft 2 in (1,880 mm)	1519
BP	1921	5988	6 ft 2 in (1,880 mm)	1859
BP	1921	5989	6 ft 2 in (1,880 mm)	1860
BP	1921	5990	6 ft 2 in (1,880 mm)	1861
BP	1921	5991	6 ft 2 in (1,880 mm)	1862
BP	1921	5992	6 ft 2 in (1,880 mm)	1863
BP	1921	5993	6 ft 2 in (1,880 mm)	1864
BP	1921	5994	6 ft 2 in (1,880 mm)	1865
BP	1921	5995	6 ft 2 in (1,880 mm)	1866
BP	1921	5996	6 ft 2 in (1,880 mm)	1867
BP	1921	5997	6 ft 2 in (1,880 mm)	1868
BP	1921	6003	6 ft 2 in (1,880 mm)	1869
BP	1921	6004	6 ft 2 in (1,880 mm)	1870
BP	1921	6005	6 ft 2 in (1,880 mm)	1871
BP	1921	6006	6 ft 2 in (1,880 mm)	1872
BP	1921	6007	6 ft 2 in (1,880 mm)	1873
BP	1921	6008	6 ft 2 in (1,880 mm)	1874
BP	1921	6009	6 ft 2 in (1,880 mm)	1875
BP	1921	6010	6 ft 2 in (1,880 mm)	1876
BP	1921	6011	6 ft 2 in (1,880 mm)	1877
BP	1921	6012	6 ft 2 in (1,880 mm)	1878

Illustration

The main picture shows NBL-built Class 12R no. 1505. An unmodified locomotive with its Belpaire firebox and reboilered locomotives from both manufacturers are shown below.

• Class 12 no. 1494.jpg

  NBL-built no. 1494, as built, with a Type MP1 tender and running boards dipping down below the cab

• SAR Class 12R 1509 Germiston 070479.jpg

  NBL-built no. 1509 with a Type MT tender, Germiston, 7 April 1979

• SAR Class 12R 1499 Sydenham 160479.jpg

  NBL-built no. 1499 with a modified Type MP1 tender, Sydenham, 16 April 1979

• SAR Class 12R 1862 New Brighton 310379.jpg

  BP-built no. 1862 with a Type MR tender, New Brighton, 31 March 1979