South African Class NG5 2-8-2

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South African Class NG5 2-8-2
SAR Class NG5 (2-8-2).jpg
Class NG5, c. 1960
Type and origin
Power typeSteam
DesignerHenschel and Son
BuilderHenschel and Son
Serial number18578-18583
ModelClass NG5
Build date1921
Total produced6
Specifications
Configuration:
 • Whyte2-8-2 (Mikado)
 • UIC1D1h2
Driver3rd coupled axle
Gauge600 mm (1 ft 11 58 in) narrow
Leading dia.21 2132 in (550 mm)
Coupled dia.33 78 in (860 mm)
Trailing dia.21 2132 in (550 mm)
Tender wheels20 12 in (521 mm)
Wheelbase38 ft 6 58 in (11,751 mm)
 • Engine17 ft 1116 in (5,199 mm)
 • Coupled9 ft 7 in (2,921 mm)
 • Tender11 ft 5 34 in (3,499 mm)
 • Tender bogie3 ft 3 38 in (1,000 mm)
Wheel spacing
(Asymmetrical)
1-2: 3 ft 1 716 in (951 mm)
2-3: 3 ft 4 18 in (1,019 mm)
3-4: 3 ft 1 716 in (951 mm)
Length:
 • Over couplers49 ft 9 14 in (15,170 mm)
Height10 ft 9 1516 in (3,300 mm)
Frame typePlate
Loco weight32 LT 17 cwt (33,380 kg)
Tender weight25 LT 11 cwt 3 qtr (26,000 kg)
Total weight58 LT 8 cwt 3 qtr (59,380 kg)
Tender type2-axle bogies
Fuel typeCoal
Fuel capacity2 LT 17 cwt (2.9 t)
Water cap2,860 imp gal (13,000 l)
Firebox typeRound-top
 • Firegrate area16.7 sq ft (1.55 m2)
Boiler:
 • Pitch5 ft 8 78 in (1,749 mm)
 • Diameter3 ft 11 34 in (1,213 mm)
 • Tube plates13 ft 1 12 in (4,000 mm)
 • Small tubes114: 1 34 in (44 mm)
 • Large tubes12: 4 2332 in (120 mm)
Boiler pressure171 psi (1,179 kPa)
Safety valveSalter
Heating surface948 sq ft (88.1 m2)
 • Tubes880 sq ft (82 m2)
 • Firebox68 sq ft (6.3 m2)
Superheater:
 • Heating area145 sq ft (13.5 m2)
CylindersTwo
Cylinder size15 34 in (400 mm) bore
17 34 in (451 mm) stroke
Valve gearWalschaerts
Valve typeSlide
Loco brakeVacuum
Train brakesVacuum
CouplersBuffer-and-chains
Performance figures
Tractive effort16,610 lbf (73.9 kN) @ 75%
Career
OperatorsSouth African Railways
ClassClass NG5
Number in class6
NumbersNG71-NG76
Delivered1922
First run1922
Withdrawn1960

The South African Railways Class NG5 2-8-2 of 1922 was a narrow-gauge steam locomotive.

In 1922, the South African Railways placed six narrow-gauge steam locomotives with a 2-8-2 Mikado type wheel arrangement in service on the Otavi Railway in South West Africa. When a system of grouping narrow-gauge locomotives into classes was eventually introduced somewhere between 1928 and 1930, they were designated Class NG5.[1][2]

Manufacturer[edit]

Six narrow-gauge steam locomotives with a 2-8-2 Mikado type wheel arrangement were built for the South African Railways (SAR) by Henschel and Son in Germany in 1921. They were built to the same design as the three Class Hd locomotives which had been built in 1912 for the German administration in German South West Africa (GSWA) for leasing to the Otavi Mining and Railway Company. The locomotives, numbered in the range from NG71 to NG76, were delivered in 1922.[1][2][3]

Characteristics[edit]

Like their predecessor Class Hd, they were superheated, with Walschaerts valve gear and outside plate frames. The new locomotives differed from the Class Hd in having different boilers, which were of the same dimensions but with a different tube arrangement and, as a consequence, a slightly reduced total heating surface.[4][5]

In keeping with SAR practice at the time, they had vacuum train brakes instead of the air brakes which the Class Hd was equipped with. They had slide valves which was unusual on a superheated locomotive, instead of piston valves like the Class Hd. As built, the sand boxes were mounted on top of the boiler between the chimney and the steam dome.[1][4][5]

Their rigidly mounted leading and trailing carrying wheels were also arranged as radial axles to allow for sideways motion of the wheels in relation to the locomotive frame, since the locomotive did not have separate bogie trucks. As on the Class Hd, this resulted in a rigid wheelbase of 17 feet 1116 inch (5,199 millimetres), even though the leading carrying wheels were arranged to the rear instead of ahead of the cylinders.[2][4][5]

Classification[edit]

In service, these six locomotives and the three Class Hd locomotives were operated in a common pool. The system of grouping narrow-gauge locomotives into classes was only adopted by the SAR at some date between 1928 and 1930. At that point, these six locomotives and the three Class Hd locomotives were all designated Class NG5.[1][2][4]

Service[edit]

The 1922-vintage Class NG5 was placed in service on the 352-mile long (566-kilometre) narrow-gauge line from Swakopmund on the Atlantic coast to Tsumeb and Grootfontein in South West Africa (SWA). They spent their whole service life in SWA, except for a brief period when one of them was sent to the Avontuur Railway in the Eastern Cape for trials. However, since it jammed on the tighter curves in the Langkloof despite having one set of flangeless coupled wheels, it was soon returned to SWA.[1]

The Class NG5 were all withdrawn from service when the narrow-gauge system in SWA was regauged to Cape gauge in 1960. Since they were unsuitable for use in the Langkloof, all six 1922-vintage Class NG5 locomotives were sold as scrap in 1962.[1]

Preservation[edit]

Two of the 1912-vintage ex Class Hd locomotives were preserved and plinthed at Otjiwarongo and Usakos respectively.[1]

References[edit]

  1. ^ a b c d e f g Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 102, 110, 116–117. ISBN 0869772112.
  2. ^ a b c d Espitalier, T.J.; Day, W.A.J. (1947). The Locomotive in South Africa – A Brief History of Railway Development. Chapter VII – South African Railways (Continued). South African Railways and Harbours Magazine, December 1947. pp. 1033-1034.
  3. ^ Henschel-Lieferliste (Henschel & Son works list), compiled by Dietmar Stresow
  4. ^ a b c d South African Railways and Harbours Narrow Gauge Locomotive Diagram Book, 2'0" Gauge, S.A.R. Mechanical Dept. Drawing Office, Pretoria, 28 November 1932
  5. ^ a b c South African Railways and Harbours Locomotive Diagram Book, 2'0" & 3'6" Gauge Steam Locomotives, 15 August 1941, as amended