South African Class MD 2-6-6-2

Last updated

CSAR Mallet 2-6-6-2 Saturated
South African Class MD 2-6-6-2
SAR Class MD 1617 (2-6-6-2) CSAR 1001.jpg
CSAR no. 1001, SAR no. 1617, c. 1910
Type and origin
Power typeSteam
Designer American Locomotive Company
BuilderAmerican Locomotive Company
Serial number46581
ModelCSAR Mallet
Build date1910
Total produced1
Specifications
Configuration:
   Whyte 2-6-6-2 (Prairie Mallet)
   UIC (1'C)C1'nv4
Driver3rd & 6th coupled axles
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Leading dia. 28+12 in (724 mm)
Coupled dia.46 in (1,168 mm)
Trailing dia. 28+12 in (724 mm)
Tender wheels33+12 in (851 mm)
Minimum curve 350 ft (107 m)
Wheelbase 65 ft 6 in (19,964 mm)
  Engine40 ft 3 in (12,268 mm)
  Coupled8 ft 4 in (2,540 mm) each
  Tender17 ft 11 in (5,461 mm)
  Tender bogie4 ft 7 in (1,397 mm)
Length:
  Over couplers73 ft 7+14 in (22,435 mm)
Height12 ft 10+38 in (3,921 mm)
Frame type Bar
Axle load 15 LT 0 cwt 2 qtr (15,270 kg)
   Leading 7 LT 14 cwt 3 qtr (7,862 kg)
  1st coupled14 LT 9 cwt 3 qtr (14,720 kg)
  2nd coupled14 LT 2 cwt 2 qtr (14,350 kg)
  3rd coupled13 LT 17 cwt 1 qtr (14,080 kg)
  4th coupled15 LT 0 cwt 2 qtr (15,270 kg)
  5th coupled14 LT 11 cwt 1 qtr (14,800 kg)
  6th coupled14 LT 10 cwt 3 qtr (14,770 kg)
   Trailing 6 LT 7 cwt 3 qtr (6,490 kg)
  Tender axle14 LT 3 cwt 1 qtr (14,390 kg) av.
Adhesive weight 86 LT 12 cwt (87,990 kg)
Loco weight100 LT 14 cwt 2 qtr (102,300 kg)
Tender weight56 LT 14 cwt (57,610 kg)
Total weight157 LT 8 cwt (159,900 kg)
Tender type2-axle bogies
Fuel typeCoal
Fuel capacity10 LT (10.2 t)
Water cap.5,000 imp gal (23,000 L)
Firebox typeRound-top
  Firegrate area49.5 sq ft (4.60 m2)
Boiler:
  Pitch7 ft 9 in (2,362 mm)
  Diameter6 ft 18 in (1,832 mm)
  Tube plates19 ft 10+18 in (6,048 mm)
  Small tubes271:2+14 in (57 mm)
Boiler pressure200 psi (1,379 kPa)
Safety valve Ramsbottom
Heating surface3,325 sq ft (308.9 m2)
  Tubes3,169 sq ft (294.4 m2)
  Firebox156 sq ft (14.5 m2)
Cylinders Four
High-pressure cylinder18 in (457 mm) bore
26 in (660 mm) stroke
Low-pressure cylinder28+12 in (724 mm) bore
26 in (660 mm) stroke
Valve gear Walschaerts
Valve typeHP Piston
LP Richardson balanced slide
Valve travelHP 5 in (127 mm)
LP 5+12 in (140 mm)
Valve lapHP 1 in (25 mm)
LP 78 in (22 mm)
Couplers Johnston link-and-pin
Performance figures
Tractive effort 45,900 lbf (204 kN) @ 50%
Career
Operators Central South African Railways
South African Railways
Class Class MD
Number in class1
NumbersCSAR 1001, SAR 1617
Delivered1910
First run1910
Withdrawn1926

The South African Railways Class MD 2-6-6-2 of 1910 was a steam locomotive from the pre-Union era in Transvaal.

Contents

In March 1910, the Central South African Railways commissioned a single experimental Mallet articulated compound steam locomotive with a 2-6-6-2 wheel arrangement. In 1912, when the locomotive was assimilated into the South African Railways, it was renumbered and designated Class MD. [1] [2] [3] [4]

Manufacturer

The first Mallet articulated compound steam locomotive on the Central South African Railways (CSAR) was ordered for test purposes from the American Locomotive Company in 1910. It was numbered 1001 and placed in service in March 1910. With its full working order weight of 157 long tons (160 tonnes), it was the heaviest locomotive in the world working on Cape gauge at the time. [1] [2] [3] [4] [5] [6]

Compound expansion

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. By comparison, in the more usual arrangement of simple expansion (simplex), steam is expanded just once in any one cylinder before being exhausted through the smokebox. [1] [7]

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 which drive the front set of coupled wheels. [1] [3]

Characteristics

The bar frames of the rear engine unit and its high-pressure cylinders were rigidly attached to the boiler with the engine's wide firebox extending over the coupled wheels. The front engine unit and its low-pressure cylinders were not rigidly attached to the boiler barrel, but carried the boiler on a single sliding bearing which was placed between the leading and intermediate coupled wheels. The underside of the smokebox was flattened to provide clearance between it and the cylinder assemblies of the front engine unit. The two engine units were coupled together by a single vertical pin connection, arranged at a point on the centre-line of the high-pressure cylinder saddle casting. This arrangement gave the locomotive a short rigid wheelbase of 8 feet 4 inches (2,540 millimetres) which made it capable of traversing curves of short radius. [2]

The locomotive used saturated steam. The high-pressure cylinders had piston valves arranged above the cylinders, while the low-pressure cylinders had Allen Richardson balanced slide valves, also arranged above the cylinders and all actuated by Walschaerts valve gear. Copper steam pipes were arranged on each side of the dome and passed vertically down outside the boiler to the steam chests of the high-pressure cylinders. The exhaust from the high-pressure cylinders passed through a receiver pipe along the centre of the engine to the low-pressure cylinders. The exhaust from the low-pressure cylinders passed to the smokebox and blast pipe through a pipe fitted with flexible connections. [2]

The firebox had a short combustion chamber. The boiler barrel was telescopic and made up in three courses from 58 inch (16 millimetres), 1116 inch (17 millimetres) and 34 inch (19 millimetres) thick plate respectively. The Walschaerts valve motion was operated by hand screw gear, with the reversing gear for one engine unit's set of gear arranged to be raised while the other's was lowered for forward or reverse, thereby balancing each other. [2]

Performance

At low speed, the locomotive proved to be capable of handling heavier trains than any of the existing CSAR fleet of goods locomotives, but at higher speeds of 25 to 30 miles per hour (40 to 48 kilometres per hour) it could not compete successfully because of excessive wear on the moving parts which resulted in failures and as a consequence, high maintenance cost. Part of the problem arose from the fact that the Mallet was expected to run to the same train schedules as the non-articulated locomotive fleet in spite of the fact that its smaller coupled wheels made it more suited to heavy low-speed work. It has been surmised that, had it been superheated and equipped with larger diameter coupled wheels, the results may have been much better. [1] [2] [6]

Service

The Mallet was acquired as an experiment, the ultimate object being to improve traffic flow on the 80 miles (129 kilometres) coal line between Witbank and Germiston. The increase of traffic and the resultant congestion on this line with a ruling gradient of 1 in 100 (1%) was causing considerable delays en route, which led to excessive hours of duty being imposed on crews. The intent was to determine the feasibility of replacing the existing Class 11 locomotives on this line with more powerful Mallets to be able to increase train loads from 900 to 1,600 long tons (914 to 1,626 tonnes). [1]

South African Railways

Railway network of the Central South African Railways in 1910 upon the establishment of the Union of South Africa and the South African Railways Central South African Railways map 1910.svg
Railway network of the Central South African Railways in 1910 upon the establishment of the Union of South Africa and the South African Railways

When the Union of South Africa was established on 31 May 1910, the three Colonial government railways (Cape Government Railways, Natal Government Railways and CSAR) were united under a single administration to control and administer the railways, ports and harbours of the Union. Although the South African Railways and Harbours came into existence in 1910, the actual classification and renumbering of all the rolling stock of the three constituent railways were only implemented with effect from 1 January 1912. [8]

While the South African Railways (SAR) came into existence in 1910, the actual classification and renumbering of all the rolling stock of the three constituent railways required careful planning and was only implemented with effect from 1 January 1912. [4]

In 1912, the engine was renumbered 1617 and designated the sole Class MD locomotive on the SAR. It remained in service on the line between Witbank and Germiston until it was withdrawn from service and scrapped in 1926. [1] [3] [4] [9]

Illustration

Related Research Articles

<span class="mw-page-title-main">2-6-6-2</span> Articulated locomotive wheel arrangement

Under the Whyte notation for the classification of steam locomotives by wheel arrangement, a 2-6-6-2 is a locomotive with one pair of unpowered leading wheels, followed by two sets of three pairs of powered driving wheels and one pair of trailing wheels. The wheel arrangement was principally used on Mallet-type articulated locomotives, although some tank locomotive examples were also built. A Garratt locomotive or Golwé locomotive with the same wheel arrangement is designated 2-6-0+0-6-2 since both engine units are pivoting.

<span class="mw-page-title-main">4-10-2</span> Locomotive wheel arrangement

Under the Whyte notation for the classification of steam locomotives by wheel arrangement, 4-10-2 represents the arrangement of four leading wheels, ten powered and coupled driving wheels and two trailing wheels. In South Africa, where the wheel arrangement was first used, the type was known as a Reid Tenwheeler. In the United States of America it was known as a Southern Pacific on the Southern Pacific Railroad and as an Overland on the Union Pacific Railroad.

<span class="mw-page-title-main">South African Class 11 2-8-2</span> Class of 36 South African 2-8-2 steam locomotives

The South African Railways Class 11 2-8-2 of 1904 was a steam locomotive from the pre-Union era in Transvaal Colony.

<span class="mw-page-title-main">South African Class 10B 4-6-2</span>

The South African Railways Class 10B 4-6-2 of 1910 was a steam locomotive from the pre-Union era in Transvaal.

<span class="mw-page-title-main">South African Class 10A 4-6-2</span> South African steam locomotive

The South African Railways Class 10A 4-6-2 of 1910 was a steam locomotive from the pre-Union era in Transvaal.

<span class="mw-page-title-main">South African Class 10 4-6-2</span>

The South African Railways Class 10 4-6-2 of 1904 was a steam locomotive from the pre-Union era in Transvaal Colony.

<span class="mw-page-title-main">South African Class KM 0-6-0+0-6-0</span>

The South African Railways Class KM 0-6-0+0-6-0 of 1904 was an articulated steam locomotive from the pre-Union era in Transvaal Colony.

<span class="mw-page-title-main">South African Class Experimental 1 4-6-2</span> Class of 1 South African 4-6-2 locomotive

The South African Railways Class Experimental 1 4-6-2 of 1907 was a steam locomotive from the pre-Union era in the Cape of Good Hope.

<span class="mw-page-title-main">South African Class Experimental 2 2-8-0</span>

The South African Railways Class Experimental 2 2-8-0 of 1902 was a steam locomotive from the pre-Union era in the Cape of Good Hope.

<span class="mw-page-title-main">South African Class Experimental 3 2-8-0</span>

The South African Railways Class Experimental 3 2-8-0 of 1903 was a steam locomotive from the pre-Union era in the Cape of Good Hope.

<span class="mw-page-title-main">South African Class MA 2-6-6-0</span>

The South African Railways Class MA 2-6-6-0 of 1909 was a steam locomotive from the pre-Union era in the Natal Colony.

<span class="mw-page-title-main">South African Class MB 2-6-6-0</span>

The South African Railways Class MB 2-6-6-0 of 1910 was a steam locomotive from the pre-Union era in the Colony of Natal.

The South African Railways Class MC 2-6-6-0 of 1912 was a steam locomotive.

<span class="mw-page-title-main">South African Class MC1 2-6-6-0</span>

The South African Railways Class MC1 2-6-6-0 of 1914 was a steam locomotive.

The South African Railways Class ME 2-6-6-2 of 1912 was a steam locomotive.

<span class="mw-page-title-main">South African Class MF 2-6-6-2</span> Class of 14 South African Mallet locomotives

The South African Railways Class MF 2-6-6-2 of 1911 was a steam locomotive from the pre-Union era in Transvaal.

The South African Railways Class MG 2-6-6-2 of 1911 was a steam locomotive from the pre-Union era in Transvaal.

<span class="mw-page-title-main">South African Class MH 2-6-6-2</span>

The South African Railways Class MH 2-6-6-2 of 1915 was an articulated Mallet-design steam locomotive.

<span class="mw-page-title-main">CSAR Rack 4-6-4RT</span>

The Central South African Railways Rack 4-6-4RT of 1905 was a South African steam locomotive from the pre-Union era in Transvaal Colony.

<span class="mw-page-title-main">South West African 2-8-0T</span>

The South West African 2-8-0T of 1907 was a steam locomotive from the German South West Africa era.

References

  1. 1 2 3 4 5 6 7 Holland, D.F. (1971). Steam Locomotives of the South African Railways. Vol. 1: 1859–1910 (1st ed.). Newton Abbott, England: David & Charles. pp. 138–140. ISBN   978-0-7153-5382-0.
  2. 1 2 3 4 5 6 Espitalier, T.J.; Day, W.A.J. (1945). The Locomotive in South Africa - A Brief History of Railway Development. Chapter VI - Imperial Military Railways and C.S.A.R. (Continued). South African Railways and Harbours Magazine, March 1945. pp. 181-183.
  3. 1 2 3 4 Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 86. ISBN   0869772112.
  4. 1 2 3 4 Classification of S.A.R. Engines with Renumbering Lists, issued by the Chief Mechanical Engineer’s Office, Pretoria, January 1912, pp. 9, 12, 15, 46 (Reprinted in April 1987 by SATS Museum, R.3125-6/9/11-1000)
  5. "Powerful Freight and Passenger Locomotives for a Narrow Gauge Railway". American Engineer and Railroad Journal: 192–194. May 1910. Retrieved 31 December 2012.
  6. 1 2 Soul of A Railway, System 7, Western Transvaal, based in Johannesburg, Part 21: Witbank Line by Les Pivnic, Eugene Armer, Peter Stow and Peter Micenko. Caption 1. (Accessed on 4 May 2017)
  7. Compounding Steam Engines
  8. The South African Railways - Historical Survey. Editor George Hart, Publisher Bill Hart, Sponsored by Dorbyl Ltd., Published c. 1978, p. 25.
  9. Holland, D. F. (1972). Steam Locomotives of the South African Railways. Vol. 2: 1910-1955 (1st ed.). Newton Abbott, England: David & Charles. p. 140. ISBN   978-0-7153-5427-8.