A steam wonder of the Diesel Era: streamline Garratt locomotive.
For starters, a short quote: "In 1934 the standard gauge between Algeria and Morocco was completed. The expresses Alger - Oran, hauled by the fantastic Garratts 231-132-AT, then BT, had cars for the express Oran - Casablanca..." (trains-worldexpresses.com)
Romantic, isn't it? But before we proceed to the loco's story, let's get some info on Garratts - or, to be more exact, Beyer-Garrat locomotives. "This locomotive had two engine units, between which the boiler was fitted by means of a pivot at each end. The Garratt locomotive was especially popular in Africa, giving a high power output with its weight spread over a very long wheel-base; the wheelbase, being flexible, was no obstacle to fast running on curved track. " (HW Garratt biography)
Now we can enjoy an excellent article by Andy Hart, published in SNCF Society Journal, #124, 2006:
"The early development of railways in Algeria was somewhat disorganised. The PLM, a dominant player from the start, steadily expanded its network. The four other principal concessionaires had by 1921 coalesced into the state-run Chemins de Fer Algériens de l'Etat. To rationalise matters, the latter exchanged some of its lines with the PLM Algérien. Then in 1933, the CFAE and PLM-A came under joint management (Chemins de Fer Algériens - CFA), in part as common measure to combat the recession. <...>. We are here concerned with the PLM-A, whose principal routes extended from Algiers west to Oran and the Moroccan frontier, and East to Constantine and the Tunisian border. These were standard gauge. From Blida - not far from Algiers on the line to Oran - south to Djelfa the line was to 1055 mm gauge, originally built by the Ouest Algérien. This gauge was used on several lines in Algeria. It may have been considered compatible with 3 ft 6 in, being only ½-inch narrower. French sources occasionally refer to it as 'métrique', though there were also genuine metre-gauge lines in the country.
"The chief engineer of the PLM-A, Ducluzeau, no doubt aware of the success of the Garratt type on railways farther south in Africa, felt that they could be a solution to traction problems on both his standard-gauge and narrow-gauge routes which had similar heavy gradients and sharp curves. From Franco-Belge at Raismes, who already held a licence from Beyer, Peacock, to build Garratts in France, he first ordered four of the 4-8-2+2-8-4 wheel arrangement for use on the Blida - Djelfa line. The design was closely based on the existing EC1 class of Kenya-Uganda Railways and the new engines were delivered in 1931. They were gallicised with air brakes and ACFI feed-water heaters and had piston valves, Walschaerts' gear and duplicated cab controls for running in either direction. The engines were numbered 241-142 YAT 1 to 4, 'Y' being the designator for 1055 mm gauge, 'A' the class letter and 'T' meaning locomotive-tender in the normal PLM style.
"The standard-gauge Algiers - Oran trunk line had gradients of 22 ‰ (1 in 45 ½) and Algiers - Constantine 26‰ (1 in 38½); both had curves down to 300 m radius on the mountain sections, but also long straight stretches where sustained high speed was possible. Express-passenger Garratts already existed elsewhere, such as on the FC Paulista in Brazil (2-6-2+2-6-2, 1927 - soon converted to 4-6-2+2-6-4) and the Central de Aragón (4-6-2+2-6-4, 1931). The Algerian specification called for haulage of 540-ton trains at 105 km/h on a straight level track, and 24 km/h on 300m-radius curves. The design for a double Pacific was worked out by Franco-Belge in conjunction with Beyer, Peacock. I think we can discount the statement that the design was done by Beyer, but they certainly exploited the Algerian locomotives in their promotional literature. It had many features in common with the YAT class, including Walschaerts' gear and piston valves to two simple-expansion cylinders at each end, ACFI, and duplicated cab controls. It was fitted with Beyer, Peacock's patented conical revolving bunker to bring the coal forward to the shovel plate. The exhaust was a single Kylchap. Numbered 231-132 AT 1, the engine was outshopped in 1932. After running-in, it was subject to intensive testing on the parent PLM. On 12 July it joined a roulement of Pacifics and 4-8-2s between Laroche and Dijon, working 26 rapides as well as omnibus and freight trains. Typical loads were 560-570 t. but up to 719 t. were taken over Blaisy-Bas. In March 1933 it moved to the other classic proving ground from Lyon to Roanne via the Rampe des Sauvages, before going to Algeria, where it was subjected to further tests throughout 1933. Its regular turn was the night express between Algiers and Affreville, a daily round trip of 238 km with a load of 350-450 ton. By May 1934 it had clocked up 75,000 km.
"It was felt that better performance should be possible, and in 1934, it was modified with Cossart valve gear, new cast steel cylinders and a PLM exhaust double à croisillons - which had to be fitted transversally due to the short, fat smokebox - and smoke deflectors. The steam-servo reversing gear was replaced by an electrically-operated mechanism. Although its performance was deemed 'average' by French standards, given the size of the loco, it was still way ahead of anything that had hitherto been achieved in Algeria and was sufficient to warrant the production of more Garratts. In order to allow the engines to be stabled in the roundhouse at Algiers, a huge 35-metre turntable was installed.
"The new requirement included speeds of 120 km/h on level track with curves of 750 m radius and 50 km/h on 200 m radius; haulage of 450 t. at 100 km/h on gradients of 3.5‰ and 45 km/h on 20‰. Henschel is reported to have offered a Garratt with four-cylinder compound propulsion on each engine unit, an enormous boiler of 2.5 m diameter with an 8 sq.m grate. This was considered a loco too far, and CFA went back to Franco-Belge for a design based on the improved 231-132 AT. The boiler pressure was raised from 16 kg/cm² to 20, grate area increased and a Clyde soot blower fitted. The transverse double PLM chimney and Cossart valve gear were retained. The revolving bunker was replaced with a conventional bunker with coal pusher, but still fully lidded; the first batch of these engines were hand-fired, requiring two firemen. The firedoor was interlocked with the blower to prevent flames backing up into the cab. A Beyer, Peacock brochure refers to the design being capable of conversion to oil-firing, but (pace Durrant) I do not think this was ever carried out.
"The feature causing most comment, and which possibly contributed to the locos' downfall, was the electrically-operated reversing gear. On the left-hand mainframe girder was a contactor box, linked by long universally-jointed shafts to the cam boxes on each engine (the modified 231-132 AT appears at one stage to have had a separate electrical unit on each engine). The cab control, duplicated for each way running, was a small lever by which "the smallest alteration in the cut-off can be accurately and quickly effected". Power came from a turbo-generator (separate from the one supplying the lighting) which could run off low steam pressure, or even compressed air from a brake reservoir.
"The most visible change was in the styling. The fore and aft tanks were given a similar profile to the boiler and the ends streamlined, giving a uniform outline, disguising the Garratt look of a barrel between two boxes. Smoke deflectors were fitted to both the front tank and the smokebox and the boiler had a 'skyline' casing. The headlights were buried in the downswept running plate; the right-hand one in each direction of travel was a powerful searchlight. The result was striking, and from some angles even elegant.
"The first of the class was delivered in early 1936 to the joint management and carried the initials CFA. By September 1936 enough were available to provide much-accelerated schedules. The timing of Algiers - Oran expresses was cut from some nine hours to just under 7 hours with 19 stops, averaging 62.5 km/h over 422 km; Algiers - Constantine was reduced by four hours to 8½ (464 km). In combination with the comfort of new coaches this wooed back passengers: from 5¾ million in 1932, journeys reached a peak of over 11 million in 1936.
"No 231-132 BT 11 could now be spared to run trials in France. One suspects that this may have been at the request of the Nord itself, anxious to see its very own Cossart gear in action on a high-powered locomotive, following the failure in 1933 of its two Cossart simple Pacifics (due, it has been said, to wrongly proportioned cylinders). Testing took place in March and April 1937, on the transversale Nord-Est, particularly between Valenciennes and Hirson; then from Paris to Aulnoye and Paris to Calais. On one trip, BT 11 accelerated a 568-tonne train up Survilliers bank, which it topped at 119 km/h, recording an output of 2900 dbhp. On 23 March, on a high-speed run to Calais, the loco attained 135 km/h on the downgrade between La Faloise and Ailly-sur-Noye, an unofficial record for an articulated locomotive, which has never been equalled.
"Other 'records' claimed for the class (not all easily verifiable) are: largest driving wheels and highest boiler pressure applied to any Garratt; heaviest weight of any French (-built) locomotive; highest tractive effort of any express passenger steam locomotive outside the USA (30,000 kg/66,000 lb). <...>
"Three more batches of the BTs followed: Nos 13-16 in 1937, 17-22 in 1939 and 23-29 in 1940. The last two batches were fitted with mechanical stokers.
"In the small hours of 17 April 1938, 231-132 BT 3 was involved in a gruesome and notorious incident. A permanent-way worker, Eugène Calvert, who had recently been dismissed as mentally unstable, took revenge by unbolting a turnout on the approach to St Cyprien-les-Attafs, so causing the wreck of train 1033, the Algiers - Oran night express. Six passengers were killed, all of them in an older, wooden sleeping car which was crushed between two of the modern steel coaches. The Garratt rolled on its side, trapping passed-fireman Marchica by his arm which was outside the cab. To free himself, he amputated the arm himself with his pocket knife. After treatment for the resultant gangrene, he eventually made a good recovery. Calvert was duly tried, found guilty and executed.
"The heyday of these imposing locomotives was short-lived. On 8 November 1942 the Allies landed in North Africa and the railways, although still under Algerian management, had to meet the demands of the military and accept drafted-in personnel. The sophisticated Garratts may have been fine when manned by titular crews and serviced by staff trained in the French tradition, but the 'rough soldiery' was more attuned to Dean Goods and USATC S-160s. Several factors affected the operation of the Garratts; commentators have placed different emphasis on each. The reversing gear caused problems: delicate electrical equipment does not work well in an environment of soot, grime and moisture; and despite the back-up systems to ensure the generator kept operating, there does not seem to have been provision for manual reversing if the contactors themselves failed. If the mechanical stoker failed, spares could not be obtained in wartime, though the engine could revert to hand firing, as half of them were hand-fired anyway. Probably the most important factor was priming (carry-over of water into the cylinders). The local water was of poor quality - to say nothing of difficulties of supply - and, even in peacetime, the boilers needed washing out after every return trip. The small vertical piston valves of the Cossart gear were very vulnerable to damage from this cause.
"Ducluzeau, now Deputy Director of the CFA, was one of a mission which went to the USA in early 1944 to seek equipment to keep the North African lines running. Whilst there he was asked to discuss requirements for the post-war recovery of France itself, which was then still under Nazi occupation - studies that ultimately led, among other things, to the 141R. During his 5 months in America and Canada Ducluzeau was impressed by US practice. On his return to Algeria, he initiated a crash programme of dieselization on the American model, using ready-to-run road-switchers from Baldwin and Alco (the Alsthom 060 DBs came later). Along with other steam power, the Garratts were laid aside, the last of the standard-gauge engines being withdrawn in 1951. The 1055-mm gauge locos remained in service rather longer, principally on freight and livestock trains, until the Blida - Djelfa line was dieselized in the 1960s, this time using French-built machines. "