South African Class 5B 4-6-2

The South African Railways Class 5B 4-6-2 of 1904 was a steam locomotive from the pre-Union era in the Cape of Good Hope.

This article is about one of several different Cape Government Railways locomotive types to be designated “Karoo Class”. For the others, see Cape Government Railways Karoo Class locomotives.

CGR Karoo Class 4-6-2 1904
South African Class 5B & 5BR 4-6-2

No. 723 plinthed at Strand, 12 April 1970
Type and origin
♠ Class 5B as built with a round-topped firebox
Class 5BR rebuilt with a Watson Standard boiler
Power type Steam
Designer Cape Government Railways
(H.M. Beatty)
Builder Beyer, Peacock and Company
Order number 9124
Serial number 4567-4570
Model CGR Karoo
Build date 1904
Total produced 4
Rebuilder South African Railways
Rebuild date 1930s
Number rebuilt 1 to Class 5BR
Specifications
Configuration:
  Whyte 4-6-2 (Pacific)
  UIC 2’C1’n2 as built
2’C1’h2 modified & Class 5BR
Driver 2nd coupled axle
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Leading dia.

28+12 in (724 mm)

Coupled dia. 60 in (1,524 mm)
Trailing dia. 33 in (838 mm)
Tender wheels 37 in (940 mm)
Wheelbase 48 ft 10+58 in (14,900 mm)
  Engine 28 ft 3 in (8,611 mm)
  Leading 5 ft 9 in (1,753 mm)
  Coupled 10 ft 5 in (3,175 mm)
  Tender 10 ft 6 in (3,200 mm)
Wheel spacing
(Asymmetrical)
1-2: 5 ft 2 in (1,575 mm)
2-3: 5 ft 3 in (1,600 mm)
Length:
  Over couplers 57 ft 7+34 in (17,570 mm) (Bell)
59 ft (17,983 mm) (AAR knuckle)
Height ♠ 12 ft 10 in (3,912 mm)
12 ft 11 in (3,937 mm)
Frame type Bar
Axle load ♠ 14 LT 7 cwt (14,580 kg)
14 LT 12 cwt (14,830 kg)
  Leading ♠ 10 LT 16 cwt (10,970 kg)
14 LT 8 cwt (14,630 kg)
  1st coupled ♠ 12 LT 13 cwt (12,850 kg)
14 LT 7 cwt (14,580 kg)
  2nd coupled ♠ 13 LT 16 cwt (14,020 kg)
14 LT 12 cwt (14,830 kg)
  3rd coupled ♠ 14 LT 7 cwt (14,580 kg)
14 LT 9 cwt (14,680 kg)
  Trailing ♠ 10 LT 6 cwt (10,470 kg)
12 LT 3 cwt (12,340 kg)
  Tender axle 11 LT 6 cwt 3 qtr (11,520 kg) av.
Adhesive weight ♠ 40 LT 16 cwt (41,450 kg)
43 LT 8 cwt (44,100 kg)
Loco weight ♠ 61 LT 18 cwt (62,890 kg)
68 LT 19 cwt (70,060 kg)
Tender weight 34 LT (34,550 kg)
Total weight ♠ 95 LT 18 cwt (97,440 kg)
102 LT 19 cwt (104,600 kg)
Tender type YE1 (3-axle)
YB, YC, YE, YE1 permitted
Fuel type Coal
Fuel capacity 6 LT (6.1 t)
Water cap 2,825 imp gal (12,800 l)
Firebox type Round-top (copper or steel)
  Firegrate area ♠ 26.5 sq ft (2.46 m2)
36 sq ft (3.3 m2)
Boiler:
  Model Watson Standard no. 1
  Pitch ♠ 7 ft 1 in (2,159 mm)
8 ft (2,438 mm)
  Diameter ♠ 4 ft 9 in (1,448 mm)
5 ft (1,524 mm)
  Tube plates ♠ 15 ft (4,572 mm)
17 ft 9 in (5,410 mm) steel f/b
17 ft 8+58 in (5,401 mm) copper
  Small tubes 181: 2 in (51 mm)
77: 2 in (51 mm) modified 5B
76:2+12 in (64 mm)
  Large tubes 16:5+12 in (140 mm) modified 5B
24:5+12 in (140 mm)
Boiler pressure 180 psi (1,241 kPa)
Safety valve ♠ Coale (723 & 724)
Ramsbottom (725 & 726)
Pop
Heating surface ♠ 1,528.5 sq ft (142.00 m2)
1,620 sq ft (151 m2)
  Tubes ♠ 1,421.5 sq ft (132.06 m2)
1,497 sq ft (139.1 m2)
  Firebox ♠ 107 sq ft (9.9 m2)
123 sq ft (11.4 m2)
Superheater:
  Heating area ♠ 324 sq ft (30.1 m2) modified 5B
366 sq ft (34.0 m2)
Cylinders Two
Cylinder size 18+12 in (470 mm) bore
26 in (660 mm) stroke
Valve gear Stephenson
Valve type Slide (as built), Piston (modified)
Couplers Johnston link-and-pin
AAR knuckle (1930s)
Performance figures
Tractive effort ♠ 20,030 lbf (89.1 kN) @ 75%
22,240 lbf (98.9 kN) @ 75%
Career
Operators Cape Government Railways
South African Railways
Class CGR Karoo Class
SAR Class 5B & 5BR
Number in class 4
Numbers CGR 905-908
SAR 723-726
Delivered 1904
First run 1904
Withdrawn 1969
The centre coupled axle had flangeless wheels

In 1904, the Cape Government Railways placed four Karoo Class 4-6-2 Pacific type passenger steam locomotives in service. In 1912, when they were assimilated into the South African Railways, they were renumbered and classified as Class 5B.[1][2][3][4]

. . . South African Class 5B 4-6-2 . . .

Following on the success of the first two Karoo Class locomotives of the Cape Government Railways (CGR), a further four were ordered from Beyer, Peacock and Company in 1904 and delivered in that same year. In view of the experience gained with the original two Karoo Class locomotives, their design was modified slightly by CGR Chief Locomotive Superintendent H.M. Beatty.[1][4][5][6]

They were numbered in the range from 905 to 908 and, like the previous two locomotives, they were also not allocated class numbers by the CGR. Instead, they were also known as the Karoo Class, from the region of the Western System where they were designed to work.[1]

The type YE1 tender was introduced along with these locomotives. It rode on three axles and had a capacity of 6 long tons (6.1 tonnes) coal and 2,825 imperial gallons (12,800 litres) water.[6]

H.M. Beatty

With these locomotives, Beatty allowed a 12 inch (13 millimetres) increase in the boiler pitch compared to that of the first two Karoo Class engines, to 7 feet 1 inch (2,159 millimetres) above the railhead.[4]

This increase still did not allow sufficient clearance between the boiler barrel and the 60 inches (1,524 millimetres) diameter coupled wheels. Pockets in the boiler barrel, similar to those used on the earlier locomotives, were therefore still necessary. The boilers of the first two locomotives, numbers 905 and 906, were fitted with Coale patent safety valves, while numbers 907 and 908 had Ramsbottom safety valves. The eccentrics and motion were actuated from the driving (centre) axle instead of the trailing axle. The firebox had an inside width of 4 feet 2+12 inches (1,283 millimetres).[4]

. . . South African Class 5B 4-6-2 . . .

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. . . South African Class 5B 4-6-2 . . .