South African Class 5A 4-6-2

South African Class 5A 4-6-2
Ex CGR Karoo Class 903, SAR Class 5A 721, Paardeneiland, circa 1940
Power type Steam
Designer Cape Government Railways
Builder Kitson and Company
Serial number 4193-4194
Model CGR Karoo Class
Build date 1903[1]
Total produced 2
Configuration 4-6-2 "Pacific"
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Leading wheel
diameter		 28.5 in (724 mm)
Driver diameter 60 in (1,520 mm)
Trailing wheel
diameter		 33 in (838 mm)
Wheelbase Total: 49 ft 1.625 in (14.976 m)
Engine:
6 ft (1.829 m) pilot
10 ft 10 in (3.302 m) coupled
28 ft 2.5 in (8.598 m) total
Tender:
10 ft (3.048 m)
Length 58 ft 9 in (17.907 m)
Height 12 ft 10 in (3.912 m)
Frame Bar frame
Axle load 12.75 long tons (13.0 t) on 2nd & 3rd drivers
Weight on drivers 38.2 long tons (38.8 t)
Locomotive weight 60.15 long tons (61.1 t)
Tender weight 32 long tons (32.5 t)
Locomotive & tender
combined weight		 92.15 long tons (93.6 t)
Tender type 3 axle tender
Wheels 37 in (940 mm) dia
Fuel type Coal
Fuel capacity 5 long tons (5.1 t)
Water capacity 2,825 imp gal (12,840 l)
Boiler 4 ft 7.75 in (1.416 m) int dia
14 ft 6.25 in (4.426 m) int length
7 ft 0.5 in (2.146 m) pitch
Boiler pressure 180 psi (1,240 kPa)
Firegrate area 26 sq ft (2.415 m2)
Heating surface:
Tubes		 154 tubes 2.25 in (57.2 mm) ext dia
1,317 sq ft (122.353 m2)
Heating surface:
Firebox		 110 sq ft (10.219 m2)
Heating surface:
Total		 1,427 sq ft (132.573 m2)
Cylinders Two
Cylinder size 18.5 in (470 mm) bore
26 in (660 mm) stroke
Valve gear Stephenson
Tractive effort 20,030 lbf (89.1 kN) at 75% boiler pressure
Career Cape Government Railways
South African Railways
Class CGR Karoo Class
SAR Class 5A
Number in class 2
Number CGR 903-904
SAR 721-722[1][2][3]
Nicknames Karoo
Delivered 1903
First run 1903
Withdrawn 1940
Disposition Retired

In 1903 the Cape Government Railways placed two Karoo Class steam locomotives with a 4-6-2 Pacific wheel arrangement in passenger service. In 1912, when they were assimilated into the South African Railways, they were renumbered and reclassified to Class 5A.[1][2][4]

Contents

Design

The Karoo Class of the Cape Government Railways (CGR) was the first locomotive with a 4-6-2 Pacific wheel arrangement to be introduced in Africa. It was the logical development of the CGR Class 6 2-6-2 that later became the Class 6Y on the South African Railways (SAR). Designed by CGR Chief Locomotive Superintendent H.M. Beatty at the Salt River shops in Cape Town, it was acquired to cope with the increasing weight of passenger trains on the one in eighty gradients between Beaufort West and De Aar.[1]

Since Beatty was very cautious about raising the boiler’s centre line to more than twice the rail gauge, or 7 feet (2.134 metres), and in this case also to accommodate the large 60 inches (1,520 millimetres) driving wheels, he resorted to cutting the boiler shell and installing specially shaped pockets to obtain the required clearance. The locomotive had a bar frame, Stephenson valve gear and used saturated steam.[1][4]

Manufacturer

Two locomotives were built by Kitson and Company in 1903, immediately after building the two Class 6Y locomotives since their works numbers follow in sequence. They were numbered 903 and 904, but were not allocated class numbers by the CGR and instead became known as the Karoo Class, from the region of the Western System that they were designed to work in.[1]

The 4-6-2 Pacific wheel arrangement was not used in other parts of Africa, but Kitson later used the Karoo design as basis for a batch of Pacifics it built for the Midland Railway of Western Australia.[5]

Class 5 sub-classes

When these two locomotives were assimilated into the newly established SAR in 1912, they were renumbered 721 and 722 and reclassified to Class 5A. The rest of the CGR’s Karoo Class locomotives were grouped into two more sub-classes by the SAR.[2][3][6]

Service

In service the Class 5A locomotives performed excellently. Beatty’s annual report for 1905 stated that they ran 159,000 miles (256,000 kilometres) before a failure occurred, that failure being a hot box. They spent most of their working lives in the Karoo, until they were displaced by larger locomotives and placed in suburban service around Cape Town. They were withdrawn by 1940.[1]

Gallery

See also

References

  1. ^ a b c d e f g Holland, D.F. (1971). Steam Locomotives of the South African Railways, Volume 1: 1859-1910 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 69-71. ISBN 0715353829. 
  2. ^ a b c Classification of S.A.R. Engines with Renumbering Lists, issued by the Chief Mechanical Engineer’s Office, Pretoria, January 1912, pp. 8, 12, 14, 34 (Reprinted in April 1987 by SATS Museum, R.3125-6/9/11-1000)
  3. ^ a b Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. p. 137. ISBN 0715354272. 
  4. ^ a b Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 39. ISBN 0869772112. 
  5. ^ Durrant, A E (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. p. 13. ISBN 0715386387. 
  6. ^ South African Railways and Harbours Locomotive Diagram Book, 2’0” & 3’6” Gauge Steam Locomotives, 15 August 1941, as amended