South African Class 26 4-8-4
From Wikipedia, the free encyclopedia: http://en.wikipedia.org/wiki/South_African_Class_26_4-8-4
| South African Class 26 4-8-4 | |
|---|---|
The Red Devil at Pretoria, Transvaal, 25 April 1981
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| Type and origin | |
| 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 |
| Specifications | |
| 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 | EW1 * 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 |
| Performance figures | |
| 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(s) | 3450 |
| Official name | L.D. Porta |
| Nicknames | Red Devil |
| Delivered | 1981 |
| First run | 6 February 1981 |
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.
Manufacturer
The original locomotive from which the Class 26 was rebuilt entered service in 1953 as the last of the Class 25NC 4-8-4 Northern locomotives to be built. 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.Trial run rebuilding
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.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.
Wardale Class 19D no. 2644
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.
Red Devil rebuilding
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.Combustion
The primary objectives of the modifications were threefold.- To improve the combustion and steaming rate.
- To reduce the emission of wasteful black smoke.
- To overcome the problem of clinkering.
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.
Engine modifications
Amongst many minor detail improvements, other major modifications to the engine included the following:
- A lengthened smokebox to accommodate the tandem double Lempor exhausts.
- Offset double chimneys.
- A feedwater-heater between the chimneys.
- Improved lubrication on cylinder and valve liner rubbing surfaces.
- A booster for increased superheating.
- New piston valves.
- Articulated valve spindles.
- New cooled valve liners.
- Redesigned chromium cast iron rings and valve liners with streamlined cylinder ports.
- New cylinder liners.
- Altered valve gear.
- Herdner starting valves.
- 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
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).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).
Reclassification
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".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 no. 4068, Henschel works number 28697, which was withdrawn from service and stored at De Aar at about the time no. 3450 was being rebuilt to Class 26. The Red Devil's actual builder's works number, 28769, had the same digits, albeit in a different order.
Trials
Test runs
Performance
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.The Red Devil’s rated freight loads are:
- 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
Drawback
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.Final attempt
Dual Lempor no. 3454, "B.I. Ebing"
Class 25NC no. 3454's Dual Lempor chimneys and extended smoke deflectors
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.
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 when compared to 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.
Steam’s demise
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.
The most recent such project was 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 were likely to also prevent the 5AT proposal from becoming reality.
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More information can be found here: http://5at.co.uk/index.php/modern-steam-2/modern-steam-miscellany/the-red-devil.html
Great bit of history. It will take some time to read all the linked articles.
ReplyDeleteTerry
Fla.
I know it is long, but well worth the reads. A lot of info is out there on this one. She's a real beauty!
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