South African Class GH 4-6-2+2-6-4

39 ft 6+1⁄2 in (12,052 mm)Length:
​ • Over couplers85 ft (25,908 mm)Height12 ft 11+7⁄16 in (3,948 mm)Frame typeBarAxle load18 LT 2 cwt (18,390 kg) ​ • Leading25 LT 12 cwt (26,010 kg) front
25 LT 14 cwt (26,110 kg) rear • 1st coupled18 LT 2 cwt (18,390 kg) • 2nd coupled18 LT (18,290 kg) • 3rd coupled18 LT 2 cwt (18,390 kg) • 4th coupled17 LT 16 cwt (18,090 kg) • 5th coupled17 LT 14 cwt (17,980 kg) • 6th coupled17 LT 16 cwt (18,090 kg) • Trailing13 LT 2 cwt (13,310 kg) front
12 LT 17 cwt (13,060 kg) rearAdhesive weight107 LT 10 cwt (109,200 kg)Loco weight184 LT 15 cwt (187,700 kg)Fuel typeCoalFuel capacity13 LT 10 cwt (13.7 t)Water cap.3,650 imp gal (16,600 L) front
2,350 imp gal (10,700 L) bellyFirebox:​ • TypeRound-top • Grate area60 sq ft (5.6 m²)Boiler:
​ • Pitch8 ft 3 in (2,515 mm) • Diameter6 ft 11 in (2,108 mm) • Tube plates13 ft 8 in (4,166 mm) • Small tubes195: 2+1⁄4 in (57 mm) • Large tubes43: 5+1⁄2 in (140 mm)Boiler pressure180 psi (1,241 kPa)Safety valvePopHeating surface:​ • Firebox214 sq ft (19.9 m²) • Tubes2,416 sq ft (224.5 m²) • Arch tubes25 sq ft (2.3 m²) • Total surface2,655 sq ft (246.7 m²)Superheater:
​ • Heating area665 sq ft (61.8 m²)CylindersFourCylinder size19+1⁄2 in (495 mm) bore
26 in (660 mm) strokeValve gearHeusingerValve typePistonCouplersAAR knuckle

Performance figures
Tractive effort	44,490 lbf (197.9 kN) @ 75%

Career
Operators	South African Railways
Class	Class GH
Number in class	2
Numbers	2320-2321
Delivered	1928
First run	1928
Withdrawn	c. 1958

The South African Railways Class GH 4-6-2+2-6-4 of 1928 was an articulated steam locomotive.

In 1928, the South African Railways placed two Class GH 4-6-2+2-6-4 Double Pacific type passenger versions of the Class U Union Garratt articulated steam locomotive in service. The Union Garratt design embodied the Garratt design at the front end and the Modified Fairlie design at the rear end.^{[1][2][3][4][5]}

Manufacturer

The Class GH, the heavy passenger version of the Class U Union Garratt, was designed and built by Maffei in Munich, Germany, to the specifications of Colonel F.R. Collins DSO, Chief Mechanical Engineer of the South African Railways (SAR). Two locomotives were delivered in 1928, numbered 2320 and 2321. They were erected at the Salt River shops in Cape Town.^[1][3][4][5]

If the same classification practice as that which was used for Garratt and Mallet locomotives had been followed, the Classes GH and U Union Garratts should have been designated Class UA and Class UB respectively. During the design phase of the two Union Garratt types, they were designated classification letters in the regular SAR Garratt range as Classes GH and GJ respectively. When orders were placed with the manufacturers, however, the Class designation of the Class GH was retained while that of the Class GJ Double Prairie type was changed to Class U. The reasoning behind this inconsistency is not known.^[6][7]

Characteristics

The locomotives were superheated and had round-topped fireboxes, bar frames, Walschaerts valve gear and Z-ported cylinders with short-lap, short-travel valves. The design of the two Union Garratt types deviated from the Garratt principle, the patent of which was held by Beyer, Peacock and Company, and the end results were hybrid locomotives, part Garratt and part Modified Fairlie. The front end of the locomotive was of a typical Garratt arrangement with a water tank mounted on the front engine unit's frame, while the rear end was constructed in the Modified Fairlie fashion with the coal bunker mounted on a rigid extension of the locomotive's main frame and with the pivoting rear engine unit positioned beneath the coal bunker.^[1][5][8]

Since the rear bunker carried only coal, an additional large underbelly water tank under the boiler compensated for the resulting diminished water capacity. All the engine's water was carried in the front bunker tank and in the underbelly water tank, with a combined capacity of 6,000 imperial gallons (27,000 litres), while the rear bunker had a coal capacity of 13 long tons 10 hundredweight (13.7 tonnes). The main frame therefore carried the smokebox, boiler, firebox, cab, coal bunker, as well as the underbelly water tank.^[1][2][5]

The Class GH were massive and powerful locomotives and, having been designed for passenger service, were built for speed with their large 60 inches (1,524 millimetres) diameter coupled wheels. With their 60 square feet (5.6 square metres) firegrates, they were equipped with mechanical stokers of the duplex type. One reason which was put forward for the construction of the rear end of the Union Garratts on the Modified Fairlie principle was to enable their coal bunkers to be rigidly in line with their boiler frames to ensure a satisfactory arrangement for the installation of mechanical stokers. The subsequent designs of the Classes GL and GM Garratts showed that this precaution was unnecessary.^[1][2]

Shortcomings

The Modified Fairlies and the Union Garratt variations of it were not successful in South Africa and they suffered from the same shortcomings.^[1]

On the Union Garratts, as on the Modified Fairlies, the frames were prone to metal fatigue and cracking, brought about by the long frame overhang at the rear beyond the engine unit pivot centre. The overhang, laden with the coal bunker which extended completely beyond the rear engine unit's pivot centre was subjected to severe vertical oscillation while the locomotive was in motion and this led to structural weakening of the frame over time.^[1][6]

In addition, since the coal bunker was mounted on the frame instead of on the engine unit, the rear pivot bearings were subject to quite rapid wear since they carried a considerable additional vertical load compared to those on a purebred Garratt. As was the case with the Modified Fairlies, this resulted in increased frequency of maintenance and as a consequence, increased operating cost.^[1][5][6]

Service

The Class GH was acquired for working the named fast passenger trains of the era, the Union Express and Union Limited, and was initially shedded in Cape Town. The service career of the Class GH had a rough start, however, since on the first trip it was discovered that it exceeded the loading gauge in width. It returned to Salt River minus its steps and sundry fittings after having scraped the platforms of every station along its route. Considerable modifications had to be carried out before the two locomotives could be placed back in regular service.^[1]

The Class GH made several trips working the Union Express out of Cape Town and was capable of taking the train up Hex River Railpass without a banker, but they were not as successful as had been hoped and they were soon taken off that duty. Their mechanical stokers also proved to be troublesome and were eventually removed. They were transferred to Natal and worked on the Natal mainline north of Glencoe for the rest of their service lives. Both were withdrawn from service by 1958.^[2][5][8]

Illustration

• 
  Class GH Union Garratt staged at Glencoe, Natal, c. 1950

References

1. ^ ^{a b c d e f g h i} Holland, D. F. (1972). Steam Locomotives of the South African Railways. Vol. 2: 1910-1955 (1st ed.). Newton Abbott, England: David & Charles. pp. 56–57. ISBN 978-0-7153-5427-8.
2. ^ ^{a b c d} 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, December 1945. p. 969.
3. ^ ^{a b} 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. 32.
4. ^ ^{a b} 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. p. 32.
5. ^ ^{a b c d e f} Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 93. ISBN 0869772112.
6. ^ ^{a b c} Durrant, AE (1989). Twilight of South African Steam (1st ed.). Newton Abbott: David & Charles. p. 31. ISBN 0715386387.
7. ^ Drawing: 2-6-2-2-6-2 Type Garratt Engine, Class GJ (Ordered as Class U). S.A.R. Mechanical Department, Drawing Office, Pretoria, 29-10-25. Approved by F.R. Collins, Chief Mechanical Engineer, 31-10-25. (Class U 2-6-2+2-6-2 drawing).
8. ^ ^{a b} Soul of A Railway, System 1, Part 2: Cape Town to Wellington. Caption 3. (Accessed on 26 November 2016)

Steam

7' ¼" gauge	East London 0-4-0VB Table Bay 0-4-0ST Table Bay 0-4-0T Table Bay 0-4-0WT
Standard 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
Cape 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
Cape 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
Cape 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

ElectricGas-electricDiesel

Cape 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 TFR Class 45-000
2' gauge Diesel-electric	SAR Class 91-000
Cape gauge Diesel-hydraulic	SAR Class 61-000
Cape gauge Electro-diesel	Spoornet Class 38-000