The background to the 5AT Project begins with the classic work of the French engineer André Chapelon (1892 – 1978) and the improvements he achieved in both the efficiency and performance of the steam locomotive. By taking a rational scientific approach to steam locomotive development Chapelon was able to incorporate improvements into rebuilds of existing designs which resulted in locomotives with a drawbar thermal efficiency of up to 12% (compared to a typical average of 6% for unrebuilt locomotives). Chapelon’s methodology contrasted sharply with the empirical and rule of thumb methods that had hitherto been the norm.
In 1949 a young Argentinean engineer, Livio Dante Porta, impressed by Chapelon’s work rebuilt a metre gauge Argentinean locomotive into a 4 cylinder 4-8-0 compound locomotive which then equalled the thermal efficiency achieved by the best of Chapelon’s rebuilds. The two men subsequently became friends and collaborators and the scientific approach to further evolution of the steam locomotive was continued by Porta right up until his death in 2003.
Porta classified steam locomotives into three generations namely:
- First Generation steam locomotives (FGS) typically designed in the 1930s – 1950s and producing in service drawbar thermal efficiencies in the region of 6 - 8%.
- Second Generation Steam (SGS): locomotives which incorporate the technological advances from 1950 to date and can be built without further technical advances. These are anticipated to produce in service drawbar thermal efficiencies in the range 12 - 16%.
- Third Generation Steam (TGS): yet-to-be developed engines, the prototypes of which would cost US $109 to develop and build. Porta anticipated that such engines could provide drawbar thermal efficiencies of up to 25% - comparable to modern diesels.
David Wardale, a British locomotive engineer who was working on steam locomotives in the CME’s department of South African Railways in the 1970s was impressed by Porta’s work. He persuaded his employers that he should rebuild two steam locomotives (a class 19D 4-8-2 and a class 25NC 4-8-4) using Chapelon/Porta technology. The subsequent performance of these locomotives fully justified their rebuilding. Later, and after working on steam developments in the USA and China, Wardale wrote a book describing his experiences and suggested that an SGS locomotive of the same size and format as the ex BR Class 5MT 4-6-0 could be developed which would provide a performance superior to any of the FGS UK express locomotives. This was the spark from which the 5AT Project developed.
It is significant the 5AT will be the first fully optimised SGS locomotive to be developed and as such will be a crucially important demonstrator for SGS technology. The development of the 5AT will carry steam locomotive technology forward and involve the recruitment and training of a new generation of steam locomotive designers who will ensure that the steam locomotive continues to evolve.
From the start of the 5AT Project in 2001 until its suspension in 2012, a considerable amount of background work was undertaken to assess all the many and various factors that were likely to influence the success of the Project. This work culminated in the completion in March 2010 of a study entitled “Feasibility Study regarding the formation of a Steam Locomotive Development Company to produce advanced technology Second Generation Steam Locomotives”.
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Active members of the 5AT Group include professional engineers and other professionals whose efforts are motivated by a determination that development of steam traction will continue into the foreseeable future.