South African Class GL 4-8-2+2-8-4

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The South African Railways Class GL 4-8-2+2-8-4 of 1929 is an articulated steam locomotive.

During 1929 and 1930 the South African Railways placed eight Class GL Garratt articulated steam locomotives with a 4-8-2+2-8-4 Double Mountain type wheel arrangement in service. Constructed at Beyer, Peacock and Company's Gorton Foundry, they were originally designed to work on the Durban to Cato Ridge section of the Natal mainline. The Class GL was eventually displaced to the route between Glencoe and Vryheid, before spending their final working years operating on the line from Stanger to Empangeni.^[1][2][3]

Genesis

The Class GL had its origin in the steady increase in loads experienced by the Natal mainline in the years prior to World War I. The old Natal mainline had gradients of 1 in 30, whilst the newer line, relocated to provide an easier route, still had 38 miles (61 kilometres) of near-uninterrupted 1 in 66 gradients. Moreover, the tight curvature of the line, with curves of as little as 275 feet (84 metres) radius, precluded the use of large, long wheelbased rigid locomotives and restricted their length to a coupled wheelbase of 9 feet (2.7 metres). These factors, combined with ever-increasing train weights, ensured that the line quickly became a bottleneck.^[1][4]

The decision to electrify the line from Glencoe Junction to Durban had been taken in 1914, coincidentally the year in which the South African Railways (SAR) ordered its first Cape gauge Garratt, the Class GA 2-6-0+0-6-2. Electrification was placed in abeyance, along with the delivery of the Class GA, until the war’s end.^[4]

Despite this delay, the process of electrification began in earnest in 1922, and by 1926 full electrified haulage had been instituted between Glencoe and Pietermaritzburg, with lashups of three electric locomotives being used on the heaviest freights. These trains were then hauled onward to Durban by a pair of Class 14 4-8-2 locomotives.^[4]

Meanwhile, the success of the Class GA Garratt, which was approximately equivalent in power output to two Class 14 locomotives, in proving the basic suitability of the Garratt design for South African conditions, coupled with the economies in crew, fuel and water consumption it offered, provided a healthy incentive for the SAR to consider a new Garratt class for use on the Natal mainline. The aim was to eliminate double-heading as a regular practice, with such a locomotive to be equivalent to three of the Class 1E electric locomotives that were then in use, or two Class 14 steam locomotives.^[1][4]

Manufacturer

Colonel F.R. Collins, the Chief Mechanical Engineer (CME) of the SAR from 1922 to 1929, prepared the specifications and awarded the contract for the design and construction of these locomotives, the Class GL, to Beyer, Peacock and Company (BP). The design was to be approximately equal to two Class 14 locomotives in power output, with a maximum permitted axle loading of 18 long tons (18 tonnes) owing to the use of 80 pounds per yard (40 kilograms per metre) rail on both sections of the mainline, and a maximum all-up weight of 215 long tons (218 tonnes).^[1][3][5]

Since these locomotives would be some 48% larger and more powerful than any locomotive previously employed on the SAR and up to twice the rail gauge in width, the initial order was for two prototype locomotives only, with more to follow should they prove successful. They were delivered in September 1929 and were erected in the Durban shops, numbered 2350 and 2351, and placed in service in October. They proved to be so successful that the remaining six locomotives were quickly ordered, for delivery in 1930 and numbered in the range from 2352 to 2357.^[1][4][6]

Design

The Class GL embodied comparatively few features of any particular novelty. Instead, they were designed to make the best possible use of existing technologies to produce a locomotive of great power, efficiency and reliability. Their all-up weight of 214.1 long tons (218 tonnes), coupled with their 18 long tons (18 tonnes) axle loading, was almost exactly within the limits laid down by the SAR and was considered by Lionel Wiener, author of Articulated Locomotives, to show "such mastery in general and detail design that we have pleasure on congratulating Messrs. Beyer, Peacock & Co. on this achievement."^[7]

Frame

The main frames were 5 inches (127 millimetres) thick cut bar frames. On the SAR the bar frame had only been employed previously on the German-built Class GCA 2-6-2+2-6-2 Garratt.^[4]

Valves and cylinders

The valves were modern straight-ported types with long-lap, long-travel valves, used for the first time in a South African Garratt, making the Class GL very free-running and more efficient than its predecessors. The cylinders, of the same bore and stroke as those of the Class 14, drove the third coupled axle using long connecting rods, which stabilised the locomotive by reducing to a minimum any vertical forces at the crosshead. This method of design became the standard on most Beyer-Garratts thereafter.^[2][4]

Pivots

In order to allow for the tight curves, including 300 feet (91 metres) radius bends with 4.5 inches (114 millimetres) superelevation lacking any intermediate tangent, and the steep, twisting nature of the line, the front pivot bearing connecting the boiler framing to the engine unit was spherical, with its alignment controlled by sprung rollers. The rear pivot was of the normal Beyer, Peacock flat adjustable type.^[4]

Boiler and firebox

The boiler, which had an inside diameter of 7 feet (2,134 millimetres), used a top feed and contained 263 small and 50 large tubes, plus superheater flues of 1.5 inches (38 millimetres) diameter, while the round-top firebox was fired by a duplex mechanical stoker, the only class on the SAR that had this feature, and contained two Nicholson thermic syphons and two arch tubes. Beyer, Peacock estimated the Class GL locomotive’s economical coal consumption rate at 3.5 long tons (4 tonnes) per hour.^[4]

Detail of the power reverser (left) and Pyle National Company turbo-generator (right) on no. 2352

The Class GL made use of Beyer, Peacock’s standard lever-actuated Sterling-type steam-operated power reverser and a Pyle National Company turbo-generator, along with a rocking grate and self-cleaning hopper ashpan with water and steam sprayers to dampen down the ash, preventing it from entering axle boxes, motion areas and other friction-sensitive places.^[4]

Crew comfort

Crew comfort was also considered. They were equipped with a Sturtevant type steam turbine powered fan blower to supply fresh air to the cab, sucked from ahead of the chimney, in deference to the almost 2 miles (3 kilometres) of tunnels to be found on this difficult section of the line. This proved less than satisfactory, as did the smoke deflecting cowls over the chimneys of the second batch of locomotives. Since Garratts are designed to be bi-directional, the problem was eventually solved by simply running them with the chimney trailing on the ascending legs of the tunneled routes.^[1][2][3][4]

Trials

Their tractive effort of 78,650 pounds-force (349.9 kilonewtons) at 75% boiler pressure made them the most powerful steam locomotives to be placed in service anywhere in the Southern Hemisphere at the time and attained the objective of constructing a locomotive to approximately equal the power output of two Class 14 locomotives. On their first test run and despite the cut-off on these locomotives being limited to 65%, 1,117 long tons (1,135 tonnes) were hauled from Durban to Cato Ridge in 163 minutes, as against 500 long tons (508 tonnes) in 184 minutes for a Class 14. Moreover, this was performed on half throttle (i.e. in first valve) and with the cut-off set at 45%.^[1][4]

This suggested that the Class GL had still more to give, a suggestion confirmed on the following day’s testing when a load of 1,205 long tons (1,224 tonnes) was hauled over the same stretch of track. It was as a result of these tests that the further six Class GL locomotives were ordered for delivery in 1930.^[1][4]

The Class GLs were eventually marshalled to standard loads of between 950 and 1,000 long tons (965 and 1,016 tonnes), despite having shown themselves capable of greater loads, in order to correspond with the load that could be hauled by a lashup of three electric locomotives. Apart from demonstrating the Class GL’s prodigious power and capacity for hauling heavy trains, these tests also showed that their running qualities were exceptional, being smooth and free-running machines. In many ways, the Class GL set a design standard that was followed later in the Class GM, Class GMAM and Class GO.^[2][4]

Service

Upon completion of the electrification project between Durban and Pietermaritzburg in 1938, the eight locomotives were transferred from the Durban section to the gruelling run between Glencoe and Vryheid, with the latter’s coal trains. This work entailed the regular haulage of 1,200 long tons (1,219 tonnes) up gradients of 1 in 50, taxing the Class GL even more heavily than the work for which it was designed. Despite this they maintained an effective service along this line until its electrification in 1968.^[1][2][4]

From Glencoe the Class GL was then transferred to work the line between Stanger and Empangeni. However, since the loads on this route did not fully justify the use of the mighty GL while their great weight and high axle loading restricted them to mainlines laid with heavy rail, they were eventually replaced by less powerful, more modern and more economical Class GMAM locomotives. Though briefly considered, somewhat improbably, as hump shunters at Bloemfontein, the Class GL had outlasted its use and, after some forty-two years of working the most difficult terrain on the SAR, they were withdrawn from service in 1972.^[3][4]

Preservation

Of the eight locomotives only two survived. Number 2351, named Princess Alice, is preserved at the Outeniqua Transport Museum. Number 2352, which waited at Germiston for some eight years before being shipped, shorn of around two hundred parts including its right-hand-side ashpan and much of its brick arch, resides at the Museum of Science and Industry in Manchester.^[4][8]

Illustration

The main picture shows Class GL no. 2351 "Princess Alice", circa 1930. The smoke deflecting cowl on the chimney, installed for tunnel working, was later removed. The only two survivors of the class are illustrated below.

• 

  No. 2351 at Camfer on the Montagu Pass during a tourist excursion, circa 2001

• 

  No. 2352 on display at the Manchester Museum of Science and Industry

References

Wikimedia Commons has media related to South African Class GL (4-8-2+2-8-4).

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 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