South African Class 26 4-8-4

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South African Class 26 4-8-4
3450 - Pretoria 250481.jpg
The Red Devil at Pretoria, Transvaal, 25 April 1981
Specifications
Power type Steam
Designer South African Railways
Builder Henschel and Son
Serial number 28769 [1][2][3]
Model Class 25NC
Build date 1953
Total produced 50
Rebuilder South African Railways
Rebuild date 1981
Number rebuilt 1
Configuration 4-8-4 "Northern"
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Leading wheel
diameter
30 in (762 mm)
Driver diameter 60 in (1,520 mm)
Trailing wheel
diameter
30 in (762 mm)
Wheelbase Total: 81 ft 4.6875 in (24.808 m)
Engine:
6 ft 10 in (2.083 m) bogie
15 ft 9 in (4.801 m) coupled
5 ft 6 in (1.676 m) trailing
38 ft (11.582 m) total
Tender:
10 ft (3.048 m) bogie
32 ft (9.754 m) total
Length 91 ft 6.5625 in (27.903 m) total
Height 13 ft (3.962 m)
Frame Cast steel
Weight on drivers 76 t (74.8 long tons)
Locomotive weight 123 t (121.1 long tons)
Tender weight 97,300 lb (44.1 t) empty
113 t (111.2 long tons) w/o
Locomotive and tender
combined weight
236 t (232.3 long tons)
Tender type EW2
* 3 axle bogies
* 34 in (864 mm) wheels
* Length 42 ft 10.5 in (13.068 m)
Fuel type Coal
Fuel capacity 20 t (19.7 long tons)
Water capacity 10,500 imp gal (48,000 l)
Fuel consumption 700 km (430 mi) range
Water consumption 230 km (140 mi) range
Boiler 6 ft 4.125 in (1.934 m) inside diameter
19 ft (5.791 m) inside length
9 ft 1.625 in (2.784 m) pitch
Boiler pressure 225 psi (1,550 kPa)
Firegrate area 70 sq ft (6.503 m2)
Heating surface:
– Tubes
158 tubes 2.5 in (63.5 mm) diameter
40 tubes 5.5 in (140 mm) diameter
3,059 sq ft (284.190 m2)
– Flues 37 sq ft (3.437 m2)
– Firebox 294 sq ft (27.313 m2)
– Total 288.35 m2 (3,103.8 sq ft)
Superheater area 94.23 m2 (1,014.3 sq ft)
Cylinders Two
Cylinder size 610 mm (24.0 in) bore
711 mm (28 in) stroke
Valve gear Walschaerts
Valve type 310 mm (12.2 in) diameter
Valve travel 156 mm (6.1 in)
Valve lap 55 mm (2.2 in) steam lap
4 mm (0.2 in) exhaust lap
Power output Maximum recorded:
3,350 kW (4,490 hp) at 75.5 km/h (46.9 mph)
Probable absolute:
3,750 kW (5,030 hp) at 100 km/h (62 mph)
Tractive effort 231 kN (52,000 lbf) starting
166 kN (37,000 lbf) at 25% adhesion
Career
Operator(s) South African Railways
Spoornet
Class Class 26
Number in class 1
Number 3450
Official name L.D. Porta
Nicknames Red Devil
First run 6 February 1981

The South African Class 26 4-8-4 of 1981 is a South African steam locomotive from the South African Railways era.

The Class 26, popularly known as the Red Devil, is a 4-8-4 steam locomotive that was rebuilt from a Class 25NC locomotive by mechanical engineer David Wardale from England while in the employ of the South African Railways. The rebuilding took place at the Salt River Works in Cape Town and was based on the principles developed by Argentinian mechanical engineer L.D. Porta.[4]

Manufacturer[edit]

The original locomotive from which the Class 26 was rebuilt entered service in 1953 as the last to be built of the Class 25NC 4-8-4 Northern locomotives. The Class 25 condensing and Class 25NC non-condensing locomotives were designed by the South African Railways (SAR) in conjunction with Henschel and Son and were built in 1953. The first Class 25, number 3451, most of the Class 25 condensing tenders and Class 25NC in the number range from 3412 to 3450 were built by Henschel, while Class 25NC in the number range from 3401 to 3411 and the other eighty-nine Class 25 condensing locomotives were built by the North British Locomotive Company (NBL) in Glasgow, Scotland.[5]

Trial run rebuilding[edit]

The rebuilding project suffered from the outset from, at best, half-hearted support on the side of the SAR management, who had by then already decided to replace all steam traction with electric and diesel-electric power.[5]

Wardale, however, was determined to demonstrate that the efficiency of steam locomotives could be drastically increased by making use of a Gas Producer Combustion System (GPCS) to produce more steam for less fuel consumed, and the Lempor exhaust system developed by Argentinian mechanical engineer L.D. Porta to utilise steam with maximum efficiency.[6]

Wardale Class 19D no. 2644

As a trial run Wardale was allowed to carry out extensive modifications on a Krupp-built Class 19D 4-8-2 branchline locomotive, number 2644. A GPCS and tandem dual Lempor exhausts were installed, along with some other small improvements that included high mounted smoke deflectors.[5]

The modifications enabled the locomotive to achieve significantly higher power and lower fuel consumption than other unmodified Class 19Ds, which resulted in Wardale being allowed to continue with the building of a Class 26 prototype.[4]

Red Devil rebuilding[edit]

Work on Class 25NC number 3450 started at the end of 1979. The manufacturing of all new items and modifications to existing parts were carried out at the SAR workshops at Salt River in Cape Town, Bloemfontein, Beaconsfield in Kimberley, Koedoespoort in Pretoria and Pietermaritzburg, the work being allocated to the workshop best suited to the particular task at hand.[6]

Combustion[edit]

The primary objectives of the modifications were threefold.[6]

  • To improve the combustion and steaming rate.
  • To reduce the emission of wasteful black smoke.
  • To overcome the problem of clinkering.

This was achieved by the use of a single-stage gas producer, the GPCS, which relies on the gasification of coal on a low temperature firebed so that the gases are then fully burnt above the firebed. It minimises the amount of air being drawn up through the firebed, the main source of air required for combustion being through ancillary air intakes located above the firebed.[7][8]

The most serious waste of fuel in a conventional steam locomotive is the loss of unburned coal particles from the fuel bed because of the rapid flow of air through the grate. With the GPCS the coal is therefore heated to drive off the volatile components which are then burned in the secondary air admitted above the grate. The result is improved combustion, thereby minimising black smoke which is evidence of incomplete combustion with the result that unburnt coal particles are ejected through the exhaust.[7][8][9]

Engine modifications[edit]

Amongst many minor detail improvements, other major modifications to the engine included the following:[6]

  • A lengthened smokebox to accommodate the tandem double Lempor exhausts.
  • Offset double chimneys.
SAR Class 26 3450 (4-8-4).jpg
  • A feedwater-heater between the chimneys.
  • Improved lubrication on cylinder and valve liner rubbing surfaces.
  • A booster for increased superheat.
  • New piston valves.
  • Articulated valve spindles.
  • Redesigned chromium cast iron rings and valve liners with streamlined cylinder ports.
  • New cooled valve liners.
  • New cylinder liners.
  • Altered valve gear.
  • Herdner starting valves.[10]
  • Air sanding.
  • An altered self-cleaning smokebox.
  • Enlarged steam chests.
  • Direct steam pipes.
  • Improved pistons.
  • Improved valve and piston rod packings.
  • An improved variable stroke lubricator drive.
  • Improved insulation.
  • Improved Walschaerts valve gear with computer calculated dimensions.
  • Continental European style high mounted exhaust deflectors, curved round but not parallel to the smokebox.

Tender modifications[edit]

The coal capacity of the Class 25NC’s type EW1 tender was increased from 18 tonnes (17.7 long tons) to about 20 tonnes (19.7 long tons). The modified tender was reclassified to Type EW2.[6]

When done, the total weight of the locomotive in full running order had been increased from 231 tonnes (227 long tons) to about 236 tonnes (232 long tons).[6]

Reclassification[edit]

These extensive modifications justified reclassification and the locomotive became the first and only Class 26, although the locomotive’s original Class 25NC number 3450 was retained. The Class 26 number plates, builder’s plate and the Salt River rebuild plate that were attached to the cab sides at the time have since been replaced with plates inscribed "Transnet National Collection".[6]

The Henschel works plates that were mounted on the cab sides of 3450 were not the originals, but were taken off Class GMAM 4-8-2+2-8-4 Garratt 4068, Henschel works number 28697, which was withdrawn from service and stored at De Aar at about the time 3450 was being rebuilt to Class 26. At least 3450’s actual works number, 28769, had the same digits, albeit in a different order.[3]

Trials[edit]

Test runs[edit]

SAR Class 26 3450 (4-8-4) Wing.JPG

The locomotive was painted in a red livery and was officially named "L.D. Porta" after the Argentinian engineer responsible for some of the ideas and developments incorporated in its modification. Initial steaming and yard running took place on Thursday 5 February 1981 and the first test trip, running light from Salt River to Bellville and back, took place the following day. On Monday 9 February 1981 the rebuilt 3450 hauled its first three coach train filled with various railway officials, staff and media representatives to Dal Josafat, about 66 kilometres (41 miles) from Cape Town. In subsequent Cape Town press reports the locomotive was dubbed the "Red Devil". The nickname eventually became official and the locomotive now bears it on the Class 25NC type exhaust deflectors that later replaced the Continental European style exhaust deflectors.[6]

Performance[edit]

Compared to an unmodified Class 25NC, the Red Devil achieved a 28% measured saving on coal and a 30% measured saving on water, measured during freight service, and a 43% increase in drawbar power based on the maximum recorded drawbar power. Its approximate maximum range in full load freight service on 1% to 1.25% grades is 700 kilometres (430 miles) based on its coal capacity, and 230 kilometres (140 miles) based on its water capacity.[6]

The Red Devil’s rated freight loads are:[6]

  • 700 tonnes (690 long tons) on 2% grades
  • 1,080 tonnes (1,060 long tons) on 1.25% grades
  • 1,320 tonnes (1,300 long tons) on 1% grades

The maximum recorded freight load hauled relative to gradient was 900 tonnes (885.8 long tons) on 2% grades, and it can haul a 650 tonnes (639.7 long tons) passenger train at a constant speed of 100 kilometres per hour (62 miles per hour) on 1% grades.[4][11]

Drawback[edit]

The Red Devil’s great power, however, also turned out to be its one weakness. The Class 25NC had already proven to be on the slippery side and the much more powerful Class 26, with essentially still the same dimensions as the Class 25NC, was even worse. It was a poor performer at starting or at low speeds on steep gradients. On its first working run from Pretoria to Witbank in Transvaal, a signal stop on a 1 in 50 (2%) gradient resulted in great struggles to restart, eventually causing about twenty minutes delay. Neither the Herdner valves nor the air sanding seemed able to overcome these problems.[5]

Final attempt[edit]

Dual Lempor no. 3454, "B.I. Ebing"
Class 25NC no. 3454's Dual Lempor chimneys and extended smoke deflectors

Following Wardale’s departure from the SAR, the Beaconsfield shops carried out a minimal modification on an NBL built ex Class 25 condenser, number 3454 that had been converted to a free exhausting non condensing Class 25NC named "BI Ebing".[5]

Modifications on this locomotive consisted mainly of equipping it with a dual Lempor exhaust system and extending its smoke deflectors upwards and curved around the smokebox. In order to save the cost of extending the smokebox, the chimneys were installed side by side instead of in tandem like on the earlier Wardale locomotives. Apart from the blastpipe and chimneys, no other modifications were incorporated.[5]

The modified no. 3454 was put to work in February 1985. Results as reported by locomotive crews and shed staff were noticeable savings in coal and water consumption compared with a standard Class 25NC, although the amounts were never quantified. The locomotive was also noticeably more sure-footed than the Class 26, which tended to slip every time it started.[5]

Steam’s demise[edit]

In a sense, the outstanding success achieved with the South African Class 26 can be considered as the final spasms of a dying breed. Although it ended up as the most efficient and powerful steam locomotive on South African rails, electric and diesel-electric locomotives had already nearly completely replaced steam by the early 1980s and the project was halted with only the one prototype ever built. It last ran on a steam excursion on 23 September 2003 and has since been mothballed, being preserved by private enthusiasts at Monument Station in Cape Town.[12][13]

SAR Class 26 3450 (4-8-4) TNC ID.JPG

Even though the Red Devil project proved that locomotives, built according to the principles behind some of the modern designs for steam locomotives, will outperform older technology steam locomotives by a large margin, it came too late to prevent the demise of steam rail traction in South Africa. Similar projects with the American Coal Enterprises (ACE) in the United States and later in China also failed to resurrect official interest in steam traction.[14][15]

The most recent such project is Wardale’s proposed 5AT Advanced Technology Steam Locomotive in the United Kingdom, but the same factors that prevented further development of modern steam locomotives in South Africa, the United States and China will likely also prevent the 5AT proposal from becoming reality.[14]

Modifications illustrated[edit]

The main picture shows the Red Devil in Pretoria just over two months after the rebuilding was completed. Several modifications were done later, some of which are externally visible when comparing the main picture with the later pictures below. Wardale considered some of these modifications to be actually detrimental to the performance of the locomotive.[6]

See also[edit]

References[edit]

  1. ^ Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 109–111. ISBN 978-0-7153-5427-8. 
  2. ^ Henschel-Lieferliste (Henschel & Son works list), compiled by Dietmar Stresow
  3. ^ a b Middleton, John N. (2002). Railways of Southern Africa Locomotive Guide - 2002 (as amended by Combined Amendment List 4, January 2009) (2nd, Dec 2002 ed.). Herts, England: Beyer-Garratt Publications. p. xx. 
  4. ^ a b c The Ultimate Steam Page
  5. ^ a b c d e f g Durrant, A E (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. pp. 194–198. ISBN 0715386387. 
  6. ^ a b c d e f g h i j k South Africa's 'Red Devil'
  7. ^ a b Information supplied by Phil Girdlestone
  8. ^ a b Gas Producer Combustion System (GPCS)
  9. ^ Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 78–79. ISBN 0869772112. 
  10. ^ Background information on Herdner Starting Valves, known as Heusinger gear in Germany (comment by Steffen)
  11. ^ South African Railways Index and Diagrams of Steam Locomotives: SAR Class 26
  12. ^ South African Railways and Harbours Locomotive Diagram Book, 2’0” & 3’6” Gauge Steam Locomotives, 15 August 1941, as amended
  13. ^ Excursion from Cape Town to Spier Estate
  14. ^ a b The ACE 3000
  15. ^ Proposed 2-10-2+2-10-2 Garratt for China

External links[edit]

External video
South African Railways RED DEVIL on goods 1991 Chasing class 26 no 3450 on the De Aar to Kimberley line in 1991, near Spytfontein. (2 minutes 50)