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 type Steam
Designer Henschel and Son
Builder Henschel and Son
Serial number 18578-18583
Model Class NG5
Build date 1921
Total produced 6
Specifications
Configuration 2-8-2 (Mikado)
Driver 3rd coupled axle
Gauge 600 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 wheels 20 12 in (521 mm)
Wheelbase 38 ft 6 58 in (11,751 mm)
 • Engine 17 ft 1116 in (5,199 mm)
 • Coupled 9 ft 7 in (2,921 mm)
 • Tender 11 ft 5 34 in (3,499 mm)
 • Tender bogie 3 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 couplers 49 ft 9 14 in (15,170 mm)
Height 10 ft 9 1516 in (3,300 mm)
Frame type Plate
Loco weight 32 LT 17 cwt (33,380 kg)
Tender weight 25 LT 11 cwt 3 qtr (26,000 kg)
Total weight 58 LT 8 cwt 3 qtr (59,380 kg)
Tender type 2-axle bogies
Fuel type Coal
Fuel capacity 2 LT 17 cwt (2.9 t)
Water cap 2,860 imp gal (13,000 l)
Firebox type Round-top
 • Firegrate area 16.7 sq ft (1.55 m2)
Boiler:
 • Pitch 5 ft 8 78 in (1,749 mm)
 • Diameter 3 ft 11 34 in (1,213 mm)
 • Tube plates 13 ft 1 12 in (4,000 mm)
 • Small tubes 114: 1 34 in (44 mm)
 • Large tubes 12: 4 2332 in (120 mm)
Boiler pressure 171 psi (1,179 kPa)
Safety valve Salter
Heating surface 948 sq ft (88.1 m2)
 • Tubes 880 sq ft (82 m2)
 • Firebox 68 sq ft (6.3 m2)
Superheater:
 • Heating area 145 sq ft (13.5 m2)
Cylinders Two
Cylinder size 15 34 in (400 mm) bore
17 34 in (451 mm) stroke
Valve gear Walschaerts
Valve type Slide
Loco brake Vacuum
Train brakes Vacuum
Couplers Buffer-and-chains
Performance figures
Tractive effort 16,610 lbf (73.9 kN) @ 75%
Career
Operators South African Railways
Class Class NG5
Number in class 6
Numbers NG71-NG76
Delivered 1922
First run 1922
Withdrawn 1960

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. 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 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