South African Class MC1 2-6-6-0

South African Class MC1 2-6-6-0
SAR Class MC1 1642, circa 1914
Power type Steam
Designer American Locomotive Company
Builder North British Locomotive Company
Serial number 20442-20456[1][2]
Model NGR Mallet
Build date 1913-1914
Total produced 15
Configuration 2-6-6-0 Mallet
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Leading wheel
diameter
28.5 in (724 mm)
Driver diameter 45.5 in (1,160 mm)
Wheelbase Total: 60 ft (18.288 m)
Engine:
8 ft 4 in (2.540 m) per coupled set
33 ft 5 in (10.185 m) total
Tender:
4 ft 7 in (1.397 m) bogie
16 ft 9 in (5.105 m) total
Length 68 ft 5.125 in (20.857 m)
Height 12 ft 5.1875 in (3.789 m)
Axle load 16.2 long tons (16.5 t) on 6th driver
Weight on drivers 89.95 long tons (91.4 t)
Locomotive weight 97.9 long tons (99.5 t)
Tender weight 50.9 long tons (51.7 t)
Locomotive & tender
combined weight
148.8 long tons (151.2 t)
Tender type 2 axle bogie
Wheels 34 in (864 mm) dia
Fuel type Coal
Fuel capacity 10 long tons (10.2 t)
Water capacity 4,250 imp gal (19,300 l)
Boiler 5 ft 8 in (1.727 m) int dia
16 ft 2.75 in (4.947 m) int length
7 ft 6 in (2.286 m) pitch
Boiler pressure 200 psi (1,380 kPa)
Firegrate area 42.5 sq ft (3.948 m2)
Heating surface:
Tubes
152 tubes 2.25 in (57.2 mm) ext dia
27 tubes 5.375 in (137 mm) ext dia
2,060 sq ft (191.380 m2)
Heating surface:
Firebox
154 sq ft (14.307 m2)
Heating surface:
Total
2,214 sq ft (205.687 m2)
Superheater area 580 sq ft (53.884 m2)
Cylinders Four
High-pressure
cylinder size
18 in (457 mm) bore
26 in (660 mm) stroke
Low-pressure
cylinder size
28.5 in (724 mm) bore
26 in (660 mm) stroke
Valve gear Walschaerts[3]
Tractive effort 46,414 lbf (206.5 kN) at 50% boiler pressure[1]
Career South African Railways
Class Class MC1
Number in class 15
Number 1634-1648[1]
Delivered 1914
First run 1914
Withdrawn 1939[3]
Disposition Retired

In 1914 the South African Railways placed fifteen Class MC1 Mallet articulated compound steam locomotives with a 2-6-6-0 wheel arrangement in service.[1][3]

Contents

Manufacturer

Orders for an improved version of the Class MC were placed with the North British Locomotive Company (NBL) in 1913. When the fifteen locomotives were delivered and placed in service in 1914, they were classified as Class MC1 and numbered 1634 to 1648.[1][3]

Characteristics

The improvements in the Class MC1 consisted mainly of a redesigned boiler that included a superheater, instead of the saturated steam boiler of the Class MC, and 0.5 inches (12.7 millimetres) larger diameter low pressure and high pressure cylinders. The result was a much better performing locomotive with an increased tractive effort brought about by the larger cylinders.[1][3]

In a compound locomotive steam is expanded in phases. After being expanded in a high pressure cylinder and having then lost pressure and given up part of its heat, it is exhausted into a larger volume low pressure cylinder for secondary expansion, after which it is exhausted through the smokebox.[4]

In the compound Mallet locomotive, the rear set of coupled wheels are driven by the smaller high pressure cylinders which are fed steam from the steam dome. Their spent steam is then fed to the larger low pressure cylinders that drive the front set of coupled wheels. By comparison, in the more usual arrangement of simple expansion, steam is expanded just once in any one cylinder before being exhausted through the smokebox.[1][3]

Service

The Class MC1 was placed in service on the coal line from Witbank to Germiston. In later years some also saw service on the Natal main line and the Cape Midlands System, while a number of them were transferred to the Cape Western System where they served as banking locomotives up the Hex River Pass between De Doorns and Touws River. They remained there until they were withdrawn from service by 1939.[1][3]

Gallery

See also

References

  1. ^ a b c d e f g h Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 21-22. ISBN 0715354272. 
  2. ^ North British Locomotive Company works list, compiled by Austrian locomotive historian Bernhard Schmeiser
  3. ^ a b c d e f g Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 85. ISBN 0869772112. 
  4. ^ Compounding Steam Engines