DIESELS SLM WINTERTHUR BROWN BOVERI & Co.
Gallery N°29 : SLM Winterthur (C.F.E. period)
Gallery N°30 : SLM Winterthur (C.D.E. period)
From 1945 onwards the Franco-Ethiopian Railway considered modernising its rolling stock. In 1946 the C.F.E. contracted the Swiss firm of "S.L.M. Winterthur" for the study, development and delivery of a series of 6 double 1340hp diesel locomotives. An order was placed on 31 December 1946, with the final schedule of conditions established in July 1948. This order comprised 5 locomotives, designated 1V to 5V, destined for the express service and 7 locomotives, designated 6M to 12 M, allocated to the mixed passenger/goods service.
The harsh climatic and topographic environment demanded particular attention to the quality and finish of these locomotives. The 800 km narrow gauged line from Djibouti to Addis Ababa included inclines of 30°/oo, and reached an altitude of 2400 m. It covered regions of varied climatic conditions. Around Djibouti the air temperature could reach 50°, with high humidity and salt content, but the line also crossed deserts swept by violent sand storms as well as the Abyssinian plateau, with a temperate climate and subject to frequent, heavy downpours.
The final schedule of conditions required two different types of locomotives: one for the mixed passenger/goods transport, and the other for the express service. The requirement for the mixed transport was a pair of locomotives able to pull a 300t train at a speed of 15 Km/h up inclines of 30°/oo, and capable of reaching 65 Km/h on a level straight. For the express service a locomotive capable of pulling an 80 t express train at 90 Km/h on a level straight was required. The two types of locomotive were to be of similar construction, with a weight per axle of 8t (+ 10%).
The control panel was situated at the front of the locomotive. This part was heavily reinforced and equipped with fenders for protection against frequent collisions with large animals. In the rear of the locomotive were the high capacity water and oil radiators needed to cool the engines which worked in temperatures up to 50°. Special filters prevented sand particles from entering the engine. The driver's cab was ventilated by filtered air.
These locomotives were equipped with a 6 VD 25 TrTH 6 cylinder 4 stroke diesel engine built by S.L.M. It was adapted for the unusual conditions, with a continuous power of 580 hp (peaking at 680 hp) and regulated at 750 revolutions per minute. It worked with direct fuel injection, equipped with an exhaust gas turbo blower that delivered full power at all altitudes.
The body was attached to two 3 axled bogies. It was connected to each bogie by a ball and socket arrangement, with lateral shock absorbing bearings that prevented rolling movement of the cab. Each bogie was interchangeable. It had 2 motorised axles and a central axle designed for later removal. Each motor was suspended "by the nose", with a geared transmission fixed on the motor axles. The gear had a reduction ratio of 1:5.69 (17 / 70) at a speed of 65 Km/h with a torque at the wheel rim of 9800 kilos.
For a rational use of all these locomotives, the reduction ratio of the gears was changeable. The crowns of the cogs could be stripped down to two pieces, without having to remove the wheels.
In July 1948 this order was once again altered as follows: a locomotive,1V, was ordered for the express train and 11 locomotives, 2M to 12M, were ordered for the mixed trains with extra sets of mixed bogies to be held as spares.
The electrical equipment of the locomotives was manufactured by B.B.C. and installed by S.L.M. All the locomotives could be coupled in pairs back to back. During the months of May and June 1950, rigorous behaviour and traction tests were carried out by the engineers of S.L.M. on the Coire-Disentis and Bernina sections of the Rhaetian Railway line. The characteristic of this line was very similar to the one the locomotives would face in Ethiopia.
The speed trials took place in Ethiopia, but following an accident, it was decided that the 12 locomotives would be equipped with bogies of mixed passenger/goods gearing. They were designated 1M to 12M.
Consequently, 12 A1A-A1A diesel locomotives capable of 580 hp and weighing 50 tons were manufactured by "S.L.M. of Winterthur" in association with "Brown Boveri & Co" of Baden. They were delivered to the Franco-Ethiopian Railway between September 1950 and February 1951.
The line reinforcement works allowed loads of 12.5T/axle. In 1963/1964 the Dire-Dawa workshops removed the median axle, transforming these machines into Bo-Bo and therefore improved their stability.
This locomotive was in a class of its own, having unique characteristics. It was manufactured by a reputable company renowned for the quality of its products, but also known for ignoring the wishes of its customers and disrespecting delivery dates.
From 1972 as the 1200 hp BB Alsthom locomotives were delivered, the SLM locomotives were gradually withdrawn from service. Three locomotives covered the local service, 3M, 6M and 10M. They were recognisable by the yellow and black stripes on their cowcatchers. The nine remaining locomotives were reserved for shunting at the station, or remained in the Dire-Dawa engine sheds as a source of spare parts.
In 1990 a study was undertaken to look at the feasibility of equipping these three remaining locomotives with more powerful engines. It proved to be financially unviable. Some of these locomotives would end their careers with over 4 million kilometres on their odometers. They remain a testimony to the C.F.E.'s expansion.
Of these twelve unique locomotives, only the wreck of 3M remains near the Dire-Dawa workshops. It appears that its renovation is planned for a hypothetical museum that might, one day, see the light of day at Addis Ababa or Dire-Dawa.
(Daniel Ammann)