EAR class 59

EAR class 59
Numbering:	5901-5934
Number:	34
Manufacturer:	Beyer, Peacock & Co.
Year of construction (s):	1955
Retirement:	around 1980
Type :	(2'D1 ') (1'D2') h4 (Garratt)
Gauge :	1000 mm ( meter gauge )
Length over coupling:	31,737 mm
Service mass:	256 t
Friction mass:	160 t
Top speed:	70 km / h
Driving wheel diameter:	1372 mm
Cylinder diameter:	520 mm
Piston stroke:	711 mm
Boiler overpressure:	155 N / cm²
Grate area:	6.69 m²
Superheater area :	69.4 m²
Evaporation heating surface:	330.65 m²
Brake:	Air brake

The class 59 vehicles of the former East African Railways (EAR) are steam locomotives of the Garratt design . They are considered to be the largest and heaviest locomotives ever built for an African railway and they are also the world's largest locomotives for meter gauge .

history

The meter-gauge railway line of the Kenya-Uganda Railway (KUR) from Mombasa in Kenya to Kampala in Uganda , built at the beginning of the 20th century, has a very demanding route profile. From sea level, the route climbs over Nairobi, which is around 1,600 m high, to 2,743 m, before descending again to Kampala, which is around 1,150 m high and is located on Lake Victoria .

The initially used two- and three-coupled tank locomotives could not move much more than their own mass over the steepest gradients of the line, so that mallet locomotives with the wheel arrangement C'C procured for the steep sections and 2'D tender locomotives for the flatter sections were.

After the KUR had observed the successful use of Garratt locomotives by other railways, the railroad procured its first Garratts ( class EC ) in 1926 . The running gear was based on that of the 2'D locomotives, with a running axle being added in each case, so that for the first time a Garratt was created with the later very successful axle arrangement (2'D1 ') (1'D2'). The locomotives proved their worth, and the railway - apart from two series - subsequently only procured Garratt locomotives.

In 1948 the East African Railways (EAR) emerged from the merger of the KUR and Tanganyika Railways . The EAR took over numerous Garratt locomotives, especially from the KUR, and introduced a new designation system, with the Garratt locomotives being assigned to classes from 50 onwards. The EAR continued the procurement policy of the KUR and limited itself to the Garratt design for new locomotives.

At the beginning of the 1950s, the volume of traffic in the Mombasa – Nairobi section reached the performance limit of the existing locomotives, and the section developed into a bottleneck for imports and exports via the port of Mombasa. It was considered to double-track the line or to electrify it, but this would have taken too long and would have been too costly.

Investigations and calculations showed that the existing superstructure allowed significantly larger locomotives than were in use at the time. The strongest Garratt machines at the time (class 54) had an axle load of 14.2 t, the single-frame locomotives of class 28 weighed 17.8 t. However, the investigations showed that the track would withstand an average axle load of 20.3 t. On this basis, a Garratt locomotive was ordered from Beyer-Peacock , which in terms of its axle load and pulling power even exceeded the Gar series Garratt of the Soviet state railways built for the Russian broad gauge . Before the nine machines ordered in 1950 were delivered, the order was increased to 34 units.

All locomotives were delivered in 1955 and designated as Class 59. They were the last steam locomotives procured by the EAR, because the class 60 had been built before the delivery of the class 59. All 34 class 59 locomotives were named after East African mountains, which is why the class was also known as the "Mountain Class".

technical features

The locomotives have the wheel arrangement (2'D1 ') (1'D2'), also called "double mountain". Other large Garratt series were also built with this wheel arrangement. Only a few Garratts received bogies instead of the inner running axles and thus the wheel arrangement (2'D2 ') (2'D2'), but less to achieve high performance than to keep the axle loads within limits. A design planned by the EAR as class 61 with this wheel arrangement, which would have significantly surpassed class 59 in terms of performance and tractive power, has no longer been implemented.

The class 59 boiler has a diameter of 2286 mm - more than twice the gauge and as much as the aforementioned Soviet Garratt. Because of the narrow profile, this led to some design problems; On the whole, however, the locomotives had no special technical features compared to other Garratts from the Beyer-Peacock house.

The driving and coupling wheels were given a diameter of 1371 mm, as in classes 57 and 58. The wheel flanges of the two inner coupled wheel sets were weakened in order to enable narrower arcs to be negotiated (on the previous models, these wheels had no wheel flanges at all). The third coupling axis, counted from the cylinder blocks, is the drive axis. For the first time in a locomotive series built for Africa, the axle and rod bearings were roller bearings .

The locomotives would be supplied with oil firing, but are intended to be converted to coal firing with mechanical grate charging ( stoker ) in the event that the supply situation changes. The locomotives could carry 39 m³ of water and 12.27 m³ of oil. They received the English hook coupling common in East Africa and a compressed air brake

Like class 57 ( class EC3 of the KUR) and all of the Garratt locomotives built subsequently for East Africa, class 59 was also prepared for gauge changeover to Cape gauge, as a connection between the East African meter gauge and the Cape gauge network of southern Africa was foreseeable at this time . For this purpose, the wheel stars were given slightly wider wheel rims, so that only changed wheel tires had to be shrunk on and the position of the brake pads had to be adjusted. In addition, these locomotives were prepared for the installation of the Janney couplings used in southern Africa in a higher position than the hook coupling. Such re-gauging has not yet taken place, although the Cape gauge with the TAZARA reached Dar es Salaam as early as 1976.

Instead of purchasing the above-mentioned Class 61, it was decided to increase the performance of the existing locomotives by installing Giesl ejectors . After initial trials in the years 1957 to 1959, all existing Garratt locomotives of the EAR were rebuilt from 1960 onwards, with the majority of the class 59 not being turned until 1962. The performance of the converted machines was significantly higher, so that even in the timetables a distinction had to be made between converted and non-converted locomotives.

Preserved locomotives

The class 59 locomotives were in daily use until around 1980. Two copies of class 59 have survived. While the locomotive No. 5930 "Mount Shengena" is only externally repaired in the Nairobi Railway Museum , No. 5918 "Mount Gelai" was taken from the museum in 2001 and restored to working order. It mostly runs on tourist trains, but has also been used as a replacement for fancy diesel locomotives.

The future of this locomotive is open. The privatization of Kenya Railways in 2006 may temporarily suspend steam train operations; However, the feared complete cessation of passenger transport and thus also the operation of special steam trains in favor of pure freight traffic is off the table.

Class 59 in comparison

Only one Garratt locomotive was larger and heavier than the class 59 - the one-off Я-01 that was already mentioned and built in 1932 for the Soviet Railways (SZD). But even this huge locomotive, built for the Russian broad gauge, had a slightly lower axle load (20 instead of 20.3 tons) - with the same wheel arrangement - and thus also a lower pulling power than the class 59. In addition, it was apparently not a success and should be as early as 1937 have been dismantled.

The largest Garratts after Class 59 are the eight Kapspur class GL machines of the South African Railways built from 1929 onwards , but they had to make do with 19 t axle load. The class 20 and 20A locomotives of the Rhodesian Railways (now National Railways of Zimbabwe ) are somewhat smaller, but heavier than the GL class . At around 268 t, the Australian garratts of NSWGR class AD60 are even heavier than EAR class 59; However, their pulling power is less than that of the locomotives mentioned because of the comparatively low axle load of around 16 t.