South African Class NG G11 2-6-0+0-6-2

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The South African Railways Class NG G11 2-6-0+0-6-2 of 1919 is a narrow gauge steam locomotive.

Between 1919 and 1925 the South African Railways placed five Class NG G11 Garratt articulated steam locomotives with a 2-6-0+0-6-2 Double Mogul type wheel arrangement in service on the Avontuur narrow gauge line through the Langkloof and also in Natal. They were the first Garratt locomotives to enter service in South Africa.^[1][2][3]

Background

The challenges of Africa resulted in the regular need for double-heading of steam locomotives on heavy trains. While West Africa found its solution in larger 4-6-2 Pacific and 2-8-2 Mikado locomotives at the beginning of the twentieth century, the steeper gradients and tighter curves in South Africa made a different solution necessary.^[3]

On South African Railways (SAR) narrow gauge lines that solution was found in 1914 when orders were placed with Beyer, Peacock and Company for a narrow gauge Garratt locomotive which was to become the first Garratt to enter SAR service.^[3]

Garratt characteristics

A powerful steam locomotive is problematic on a track gauge of only 2 feet (610 millimetres) and a tight minimum radius of about 150 feet (46 metres), which in practice restricts powerful rigid-frame locomotives to four-coupled driving wheels, often with at least one flangeless driving wheel set.^[4]

The same problem also existed on Cape gauge single line light rail track, where train lengths would be limited because conventional locomotives had been enlarged to the limit of their possible power due to restrictions on axle loading. Alternative solutions would either be double-heading longer trains or re-building and re-laying large parts of the lines to accommodate heavier locomotives. Either method was expensive and in such conditions the Garratt design had distinct advantages.^[4]

Garratt advantages

A Garratt is actually two separate locomotives combined in a double articulated format, thereby providing multiple powered axles over which the total locomotive weight is spread. This in turn results in a more powerful locomotive, since a much larger percentage of the locomotive’s total mass contributes to traction, compared to a tender locomotive of similar total mass.^[4]

Unlike tender locomotives, Garratts are bi-directional, which eliminates the need for turntables or triangles, also known as wyes. The fact that they did not need to be run through to terminals to be turned around also made increased operational flexibility possible.^[5]

Probably the greatest advantage of the Garratt was the fact that, with its boiler and grate area suspended between two engine units without the need to leave room for driving wheels and cylinders, wide and deep fireboxes with large grate areas and large diameter boilers were possible. On a Garratt the boiler could literally be dimensioned up to the full cross section of the loading gauge. With each set of cylinders and drivers constituting a separate engine, the end result was two locomotives in one with one huge boiler that needed only one crew. A Garratt is therefore a single locomotive with double the tractive effort and, with its weight distributed over a long and flexible multi-axle wheelbase, a lower axle loading.^[4][6]

Garratt drawbacks

The Garratt design has some inherent drawbacks, however, the first being a diminishing factor of adhesion over long distances. As water and coal is consumed, the weight over the drivers is reduced, thereby reducing their factor of adhesion, the ratio of weight on drivers to tractive effort. Therefore, as the weight on the drivers decreases, the locomotive has less adhesion and becomes increasingly prone to slipping.^[1][2]

With Cape gauge Garratts this was usually overcome by the use of auxiliary water tankers behind the locomotives, which enabled the onboard water tanks to remain filled longer and hence kept the factor of adhesion high farther.^[1][2][7]

Another drawback is the risk of tilting. These narrow gauge Garratts had boilers of 4 feet 2 inches (1,270 millimetres) diameter on a frame width of about 6 feet 10.5 inches (2,096 millimetres). This created the risk of the locomotive tilting over on tight curves.^[2]

Manufacturer

Although they had already been ordered in 1914, production was disrupted by the Great War and Beyer, Peacock and Company was only able to deliver the first three locomotives in 1919, after cessation of hostilities. All three, numbered in the range from NG51 to NG53, were erected at Uitenhage and put on trials on the Avontuur line in May 1920. These three locomotives were not superheated. They had outside plate frames, Walschaerts valve gear, Belpaire fireboxes and used saturated steam and slide valves.^[1][8]

Having been proved successful during trials, another two locomotives were ordered from Beyer, Peacock. Numbers NG54 and NG55 were delivered in 1925 and entered service in Natal. These two were superheated and as a result had longer smokeboxes and were 9.5 inches (241 millimetres) longer in overall length. Superheating also required alteration of the valve gear and piston valves were therefore used instead of slide valves. The cabs of the second order locomotives were also improved to offer better protection to the crew.^[1][2]

Classification

The system of grouping narrow gauge locomotives into classes was only adopted by the SAR somewhere between 1928 and 1930 and at that point these Garratt locomotives were classified as Class NG G11, with the letters "NG" indicating narrow gauge and the "G" prefixing the classification number identifying it as a Garratt locomotive.^[1][9][10]

Service

Brass bilingual plate

English only plate

The first three locomotives were placed in service on the Avontuur line, but were all soon transferred to Natal where all but one remained for the rest of their service lives, until withdrawal by 1962. Number NG51 was later returned to the Avontuur line to replace the retiring Class NG3 number NG5 as yard shunter at Humewood Road.^[1]

The two locomotives of the second order also served in Natal, ending up working on the branch from Estcourt to Weenen by 1966, when they were both transferred to the Avontuur line in exchange for two newer Class NG G13 locomotives. There they were employed on yard duty and on transfer trips to and from the docks until, after the arrival of the Class 91-000 diesel-electric locomotives in 1973, they were withdrawn from service in October 1974.^[1][2]

Preservation

Of the first three locomotives, only number NG52 still exists. It was sold to Rustenburg Platinum Mines in 1956 and became their number 7. After retirement at the mine, it was preserved at the Museum of Man and Science in Johannesburg in 1974, then moved to the Klein Jukskei Motor Museum by 1981 and finally donated to the South African National Railway And Steam Museum (SANRASM). In 2010 it was acquired by Sandstone Estates and by 2011 it was being restored and rebuilt in Bloemfontein.^[11] The other two were scrapped after being retired from SAR service.^[12]

The two superheated locomotives still exist. Although number NG54 was restored in Bloemfontein in 1989, it was staged out of service at Humewood Road until it was removed by Sandstone Estates in 2011 to be restored once again. Number NG55 was restored to full working order and was being run on the Patons Country Narrow Gauge Railway (PCNGR) at Ixopo in Natal by 2005. At the time the PCNGR was operating tourist excursion trains between Ixopo and Ncalu.^[2][13]

Illustration

The main picture and the following photographs illustrate views of the Class NG G11 locomotive from different sides and in different liveries.

• 

  Beyer, Peacock and Company works picture of no. NG51, c. 1919

• 

  NG G11 no. NG55 at Ixopo, KwaZulu-Natal, 4 June 2005

• 

  The compact Walschaerts valve gear on NG G11 no. NG55, 4 June 2005

• 

  NG G11 no. NG55 entering Ixopo station, 3 September 2005

References

Wikimedia Commons has media related to South African Class NG G11 (2-6-0+0-6-2).

Locomotives of South Africa Steam 7' ¼" gauge East London Harbour 0-4-0 Table Bay Harbour 0-4-0ST Table Bay Harbour 0-4-0T Table Bay Harbour 0-4-0WT 4' 8½" gauge Cape 0-4-0T Blackie Cape 0-4-2 Cape 2-4-0T CGR 0-4-0ST Aid Natal 0-4-0ST Durban Natal 0-4-0WT Natal Natal 4-4-0T Perseverance 3' 6" gauge Tank engines CGR 0-4-0ST 1873 CGR 0-4-0ST 1874 CGR 0-4-0ST 1881 Coffee Pot CGR 0-6-0ST 1902 CGR 0-6-0T 1876 Back-to-Back CGR 2-6-0ST 1900 CGR 2-6-0ST 1902 CGR 1st Class 0-4-0ST 1875 CGR 1st Class 0-4-0ST 1876 CGR 1st Class 2-6-0ST 1876 CGR 1st Class 4-4-0T 1875 CGR 2nd Class 4-4-0T 1882 CGR 3rd Class 2-6-0T CGR Railmotor CSAR Class C CSAR Class E CSAR Rack CSAR Railmotor DSWA Eight-Coupled Tank 2-8-0T Durban's Congella Durban's Edward Innes Durban's John Milne Durban's Sir Albert Port Elizabeth Harbour 0-4-0ST Kowie Railway 0-6-0T Kowie Railway 4-4-0T Metropolitan & Suburban 4-6-2T NGR 2-6-0T Durban & Pietermaritzburg NGR Class I 2-6-2T NGR Class K 0-4-0ST NGR Class K 0-6-0ST NGR Class K 2-6-0T NZASM 10 Tonner NZASM 14 Tonner NZASM 18 Tonner NZASM 19 Tonner NZASM 32 Tonner NZASM 40 Tonner PPR 26 Tonner PPR 35 Tonner Portuguese SAR 0-4-0ST 1903 SAR 0-4-0T no. 69 SAR Class A SAR Class B SAR Class C SAR Class C1 SAR Class C2 SAR Class D SAR Class E SAR Class F SAR Class G SAR Class H SAR Class H1 SAR Class H2 SAR Class J SAR Class K SAR Clayton Railmotor 3' 6" gauge Tender engines CGR 1st Class 2-6-0 1876 Beyer, Peacock CGR 1st Class 2-6-0 1876 Kitson CGR 1st Class 2-6-0 1879 CGR 1st Class 2-6-0 1891 CGR 1st Class 4-4-0 1879 CGR 1st Class 4-4-0TT 1881 CGR 2nd Class 2-6-2TT 1875 CGR 3rd Class 4-4-0 1883 CGR 3rd Class 4-4-0 1884 CGR 3rd Class 4-4-0 1889 CGR 3rd Class 4-4-0 1898 CGR 3rd Class 4-4-0 1901 CGR 3rd Class 4-4-0 1903 CGR 4th Class 4-4-2 CGR 4th Class 4-6-0TT 1880 CGR 4th Class 4-6-0TT 1882 CGR 4th Class 4-6-0TT 1884 CGR 5th Class 4-6-0 1890 CGR 5th Class 4-6-0 1891 DSWA Eight-Coupled Tender 2-8-0 NGR Havelock NGR Class I SAR Class Exp 1 SAR Class Exp 2 SAR Class Exp 3 SAR Class Exp 4 SAR Class Exp 5 SAR Class Exp 6 SAR Class S SAR Class S1 SAR Class S2 SAR Class 1 SAR Class 1A SAR Class 1B SAR Class 2 SAR Class 2C SAR Class 3 SAR Class 3A SAR Class 3B SAR Class 4 SAR Class 4A SAR Class 5 SAR Class 5A SAR Class 5B SAR Class 6 SAR Class 6A SAR Class 6B SAR Class 6C SAR Class 6D SAR Class 6E SAR Class 6F SAR Class 6G SAR Class 6H SAR Class 6J SAR Class 6K SAR Class 6L SAR Class 6Y SAR Class 6Z SAR Class 7 SAR Class 7A SAR Class 7B SAR Class 7C SAR Class 7D SAR Class 7E SAR Class 7F SAR Class 8 SAR Class 8A SAR Class 8B SAR Class 8C SAR Class 8D SAR Class 8E SAR Class 8F SAR Class 8R SAR Class 8X SAR Class 8Y SAR Class 8Z SAR Class 9 SAR Class 10 SAR Class 10A SAR Class 10B SAR Class 10C SAR Class 10D SAR Class 11 SAR Class 12 SAR Class 12A SAR Class 12B SAR Class 13 SAR Class 14 SAR Class 14A SAR Class 14B SAR Class 14C SAR Class 15 SAR Class 15A SAR Class 15B SAR Class 15C SAR Class 15CA SAR Class 15E SAR Class 15F SAR Class 16 SAR Class 16A SAR Class 16B SAR Class 16C SAR Class 16D SAR Class 16DA SAR Class 16E SAR Class 17 SAR Class 18 SAR Class 19 SAR Class 19A SAR Class 19B SAR Class 19C SAR Class 19D SAR Class 20 SAR Class 21 SAR Class 23 SAR Class 24 SAR Class 25 SAR Class 25NC SAR Class 26 Red Devil 3' 6" gauge Articulated engines CGR Fairlie CGR Kitson-Meyer SAR Class FC SAR Class FD SAR Class GA SAR Class GB SAR Class GC SAR Class GCA SAR Class GD SAR Class GDA SAR Class GE SAR Class GEA SAR Class GF SAR Class GG SAR Class GH SAR Class GK SAR Class GL SAR Class GM SAR Class GMA SAR Class GO SAR Class HF SAR Class KM SAR Class MA SAR Class MB SAR Class MC SAR Class MC1 SAR Class MD SAR Class ME SAR Class MF SAR Class MG SAR Class MH SAR Class MJ SAR Class MJ1 SAR Class U 2' 6" gauge Cape Copper 0-6-0T 1871 Cape Copper Britannia Cape Copper Caledonia Cape Copper Clara Class Cape Copper Condenser Cape Copper Scotia Class Namaqua Copper Pioneer 2' & 600mm gauges ACR Class NG-G16A CGR NG 0-6-0T CGR NG 4-6-2T CGR Type A 2-6-4T CGR Type C 0-4-0T DSWA Class Ha DSWA Class Hb DSWA Class Hc DSWA Class Hd DSWA Jung DSWA Zwillinge NGR Class N 4-6-2T SAR NG 0-4-0T 1899 SAR Class NG1 SAR Class NG2 SAR Class NG3 SAR Class NG4 SAR Class NG5 SAR Class NG6 SAR Class NG7 SAR Class NG8 SAR Class NG9 SAR Class NG10 SAR Class NG-G11 SAR Class NG-G12 SAR Class NG-G13 SAR Class NG-G14 SAR Class NG15 SAR Class NG-G16 Electric Amcoal Class E38 SAR Class ES SAR Class ES1 SAR Class Exp-AC SAR Class 1E SAR Class 2E SAR Class 3E SAR Class 4E SAR Class 5E s1 SAR Class 5E s2 SAR Class 5E s3 SAR Class 5E1 s1 SAR Class 5E1 s2 SAR Class 5E1 s3 SAR Class 5E1 s4 SAR Class 5E1 s5 SAR Class 6E SAR Class 6E1 s1 SAR Class 6E1 s2 SAR Class 6E1 s3 SAR Class 6E1 s4 SAR Class 6E1 s5 SAR Class 6E1 s6 SAR Class 6E1 s7 SAR Class 6E1 s8 SAR Class 6E1 s9 SAR Class 6E1 s10 SAR Class 6E1 s11 SAR Class 7E SAR Class 7E1 SAR Class 7E2 s1 SAR Class 7E2 s2 SAR Class 7E3 s1 SAR Class 7E3 s2 SAR Class 8E SAR Class 9E s1 SAR Class 9E s2 SAR Class 10E SAR 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