History
The steam locomotive HG 4/4 (four axes coupled) have been built in the workshops of the Swiss Locomotive and Machine Factory in Winterthur between 1923 and 1930. France purchased during these years seven of these engines for its colony Indochina (today Vietnam). These and other Cogwheel steam locomotives were operating in the southern part of the country, connecting the coast with Da Lat a village 5000 feet above sea level with a pleasant climate. The railroad line suffered considerably during the Vietnam war and with its end exploitation stopped. The locomotives fell into hibernation. Only in 1983 some Swiss people remembered the existence of these veterans. After several years of negotiations and thanks to a competent and enthusiastic group of the DFB " Furka Cogwheel Steam Railway" two locomotives HG 4/4 were purchased and repatriated with much publicity. The two complete locomotives and one frame were transfered to the DFB workshop in Chur where they await the complete rework. It was to our great advantage, that the railroad in Vietnam was using the same technical standard as the Furka Oberalp line (Today Matterhorn Gotthard Bahn) There should be no problem to operate these engines on the tracks of the DFB. Once operational they will be the most powerful cogwheel steam locomotives in Europe (if not the world) and will represent together with the original Locomotives of the Visp Zermattbahn and the Furka Oberalpbahn a unique testimony of Swiss engineering art and knowledge.
Mixed Cogwheel and Adhesion Steam Locomotive
Manufacturer: Swiss Locomotive and Machine Factory (SLM) in Winterthur
Year of manufacturing: 1924 - 1930
Serial number: 2937 - 2941 Propulsion Systems
Length over buffers: 8,95 m Adhesion: Control Heusinger ( Walschaerts)
Storage of coal: 1,8 tons Piston diameter: 455 mm
Weight empty: 34 tons Piston stroke: 450 mm
Water reserve: 4000 liters diameter driving wheel: 865 mm
Total weight: 45 tons
boiler pressure: 14 bar Cogwheel: Control Heusinger (Walschaerts)
Towing load: 75 tons Piston diameter: 455 mm
Total heating surface: 92,4 m2 Piston stroke: 430 mm Cogwheel System Abt
Maximum speed: Adhesion 40 km/h Number of teeth: 22
Maximum speed: Cog rack: 15 km/h Pitch: 120 mm
Delivery of locomotives was made to the "Chemin de fer de l'Indochine" (CFI) beginning 1924. (Serial 701 - 705) In 1929 the Machine factory of Esslingen in Germany supplied two more of these locomotives built under license of SLM as war indemnification with the numbers 708 and 709 (SLM No 3413 and 3414. After 1949 and now under Vietnamis administration all locomotives received new numbers with prefix VHX (Vietnam Hoa Xa) Serial 40-302 to 40-308
HG 4/4 No VHX 308
In front of the depot in Da Lat Vietnam
(Foto by Jakob Knöpfel
Construction Highlights in the development of Cogwheel Steam Locomotives
Separated Mechanism for the cogwheel and adhesion drive "System Winterthur" The two Low pressure cylinders drive over an intermediate reduction gear the two cogwheel. These are adjustable in height and can be easily adapted to the wear of the adhesion drive wheels. The adhesion drive is as commonly used on steam engines on the outside with its respective cylinders.
Driving on the adhesion tracks only, the lower outside cylinders i.e. the High Pressure Cylinders receive the live steam. Traveling on the cogwheel sections the locomotive works in the compound action mode i.e. the live steam after expansion in the high pressure cylinders is directed to the low pressure cylinders driving the cog wheels. This allows an optimal power distribution and control.
This type of driving mechanism has been used by the Swiss Locomotive and Machine Factory with great success and was part of many export orders.
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