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

The South African Railways Class NG G11 2-6-0+0-6-2 of 1919 was 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][4]

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.^[4]

On the 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.^[4]

Garratt characteristics

A powerful steam locomotive is problematic on a track gauge of only 2 feet (610 millimetres) with a tight minimum radius of about 150 feet (46 metres) which, in practice, restricts powerful rigid-frame locomotives to four-coupled wheels, often with at least one flangeless coupled wheelset.^[5]

The same problem also existed on Cape gauge light-rail single-line 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-aligning large parts of the lines to accommodate heavier locomotives. Either method was expensive and, in such conditions, the Garratt design had distinct advantages.^[5]

On a Garratt locomotive, the shared boiler and cab are carried on a cradle frame, which is suspended on pivot centres attached to the frames of the two engine units, which are both free to align itself to the track curvature. To accommodate the pivoting, the steam and exhaust pipes have flexible connections between the engine units and the central cradle.^[1]

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. The use of a Garratt locomotive enables the capacity of a line to be approximately doubled, without having to strengthen the track, bridges and culverts, or re-align the curvature.^[1][5]

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.^[6]

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 coupled 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 coupled wheels constituting a separate engine, the end result was two locomotives in one, with one huge shared boiler which 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.^[5][7]

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 coupled wheels is reduced, thereby reducing their factor of adhesion, the ratio of weight on coupled wheels to tractive effort. Therefore, as the weight on the coupled wheels decreases, the locomotive has less adhesion and becomes increasingly prone to slipping.^[2][3]

Another drawback is the risk of tilting. These narrow gauge Garratts had boilers of 4 feet 2 inches (1,270 millimetres) inside diameter on a frame width of about 6 feet 10 ¹⁄₂ inches (2,096 millimetres). This created the risk of the locomotive tilting over on tight curves.^[3]

Manufacturer

Although they had already been ordered in 1914, production was disrupted by the First World War. 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 the Uitenhage workshops and put on trials on the Avontuur line in May 1920. One initially remained there after the trials, while the other two went to the Stuartstown line in Natal. These three locomotives were not superheated. They had outside plate frames, Walschaerts valve gear, Belpaire fireboxes and used saturated steam and slide valves.^[1][2][8]

Having been proved successful during trials, another two locomotives were ordered from Beyer, Peacock. Numbers NG54 and NG55 were delivered in 1925 and erected at the Durban workshops in April of that year. Both entered service in Natal. These two were superheated and, as a result, had longer smokeboxes and were 9 ¹⁄₂ 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][3]

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.^[2][9][10]

Service

Brass bilingual plate

English only plate

The first three locomotives were all working in Natal soon after entering service. All but one remained there for the rest of their service lives, until withdrawal by 1962. No. NG51 was later returned to the Avontuur line to replace the retiring Class NG3 no. NG5 as yard shunter at Humewood Road.^[1][2]

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. In Port Elizabeth, 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.^[2][3]

Preservation

Of the first three locomotives, only no. NG52 still exists. It was sold to Rustenburg Platinum Mines in 1956 and became their no. 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]

Both superheated locomotives still exist. Although no. 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. No. 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.^[3][13]

Illustration

• 
  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 0-4-0VB Table Bay 0-4-0ST Table Bay 0-4-0T Table Bay 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 CGR 0-4-0ST 1881 Coffee Pot CGR 0-6-0ST CGR 0-6-0T 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 CGR 1st Class 4-4-0T CGR 2nd Class 4-4-0T CGR 3rd Class 2-6-0T CGR Railmotor CSAR Class C CSAR Class E CSAR Rack 4-6-4RT CSAR Railmotor Durban's Congella Durban's Edward Innes Durban's John Milne Durban's Sir Albert Port Elizabeth 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 13 Tonner NZASM 14 Tonner NZASM 18 Tonner NZASM 19 Tonner NZASM 32 Tonner NZASM 40 Tonner PPR 26 Tonner PPR 35 Tonner Portuguese 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 Railmotor SAR Dock 0-4-0ST SAR Dock 0-4-0T SWA 2-8-0T 3' 6" gauge Tender engines CGR 1st Class 2-6-0 1876 BP 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 CGR 1st Class 4-4-0TT CGR 2nd Class 2-6-2TT 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 1882 Joy CGR 4th Class 4-6-0TT 1884 CGR 5th Class 4-6-0 1890 CGR 5th Class 4-6-0 1891 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 1st SAR Class 14C 2nd SAR Class 14C 3rd SAR Class 14C 4th 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 1928 SAR Class 16DA 1930 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 SAR Katanga SWA 2-8-0 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 John King & Miner Cape Copper Britannia Cape Copper Caledonia Cape Copper Clara Cape Copper Condenser Cape Copper Scotia Namaqua Copper Pioneer Walvis Bay 2-4-2T Hope 2' & 600mm gauges ACR Class NG-G16A CGR NG 0-4-0T CGR NG 0-6-0T CGR NG 4-6-2T CGR Type A 2-6-4T CGR Type C 0-4-0T NGR Class N 4-6-2T SAR Dutton SAR NG 0-4-0T 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 SWA Class Ha SWA Class Hb SWA Class Hc SWA Class Hd SWA Jung SWA Zwillinge
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 Spoornet Class 7E4 SAR Class 8E SAR Class 9E s1 SAR Class 9E s2 SAR Class 10E SAR Class 10E1 s1 Spoornet Class 10E1 s2 SAR Class 10E2 SAR Class 11E SAR Class 12E Spoornet Class 14E Spoornet Class 14E1 TFR Class 15E Spoornet Class 16E Spoornet Class 17E Spoornet Class 18E s1 TFR Class 18E s2 TFR Class 19E TFR Class 20E TFR Class 21E TFR Class 22E
Gas-electric	SAR Gas-electric
Diesel	3' 6" gauge Diesel-electric PRASA Class Afro 4000 SAR Class DS SAR Class DS1 SAR Class 31-000 SAR Class 32-000 SAR Class 32-200 SAR Class 33-000 SAR Class 33-200 SAR Class 33-400 SAR Class 34-000 SAR Class 34-200 SAR Class 34-400 SAR Class 34-500 SAR Class 34-600 SAR Class 34-800 SAR Class 34-900 SAR Class 35-000 SAR Class 35-200 SAR Class 35-400 SAR Class 35-600 TFR Class 35-800 SAR Class 36-000 SAR Class 36-200 SAR Class 37-000 Spoornet Class 39-000 TFR Class 39-200 TFR Class 43-000 TFR Class 44-000 2' gauge Diesel-electric SAR Class 91-000 3' 6" gauge Diesel-hydraulic SAR Class 61-000 3' 6" gauge Electro-diesel Spoornet Class 38-000
List of South African locomotive classes South African locomotive numbering and classification