There are many people (including many with great knowledge of the subject) who challenge Wardale’s choice of Walschaerts valve for the 5AT, believing that British Caprotti (as used on the BR 8P Pacific No 71000 Duke of Gloucester) would have been a far more appropriate choice because it offers larger port openings and zero back […]
The following comes from a “Is it just a Phantom” – David Wardale’s response to Herr Ebel published in Lok Report in March 2001: “It should be noted that needle roller bearings were an integral part of the American Baker valve gear, and are extensively used on Walschaerts valve gear on Chinese locomotives, operating successfully […]
There has been much debate over the years since this project was initiated as to whether Wardale was mistaken in adopting piston valves driven by Walschaerts valve gear on the 5AT instead of British Caprotti valves driven by rotary cams. The issue is discussed in the FAQ pages and two or three letters on the subject appear […]
Note: With 30 inch piston stroke and 6′ 2″ wheels, the piston speed at the max. design speed of 200 km/h (125 mph) will be 23.8 m/s or 24.8 m/s with worn tyres. David Wardale responds as follows: Whatever the mean piston speed, a piston always moves slowly close to the end of its stroke […]
The effects of “hammer blow” are discussed in the response to the FAQ relating to perceived benefits of a 3-cylinder arrangement. However they are covered in more detail in the Notes on FDC 8 where Wardale’s conclusions are presented as follows: The 5AT locomotive can be satisfactorily balanced for 200 km/h operation by all criteria […]
The following comes from a “Summary Specification” drafted by Wardale on 17 Apr 2001: “The power of the 4-6-0 proposal fully utilizes the available adhesion, therefore any larger locomotive designed for higher power will have to have more coupled axles. A 4-6-2 of higher power would not have adequate adhesive weight, and an 8-coupled locomotive […]
The following answer is taken from Wardale’s response to an unpublished letter from Bryan Attewell written in response to Wardale’s two-part article “Steaming into the Future” published in Steam Railway magazines #272 and #273 (see ‘Articles and Letters’ page of this website): “Regarding the designations “mixed traffic” and “express” we should not forget that for […]
In fact we recognize that it will be impossible to gain approval to run any faster than 75mph in its initial period of life. We would hope that lifting of the limit to 90 mph would be granted after the locomotive has proved itself safe when running at 75mph for some (unknown) period of time. […]
In May 2008, John Tasker wrote to ask: “With the current price of oil and the re-opening of some coal mines, has any thought been given to coal-fired alternative mentioned in the design spec for the 5AT?”. Chris Newman offered the following response: What you say about the effects of oil price rises is quite […]
In 2005, the question was asked as to whether consideration had been given to firing the 5AT with “bio-mass”, ethanol or other fuel that is more environmentally friendly than gas oil, since this might offer cash benefits through government grants. Chris Newman responded as follows: This is a very valid question that I have been […]
On page 83 of his book, Wardale quotes a 19th century writer, saying: “We were trying to keep out of trouble by preventing smoke, but soon found that the prevention of smoke and the saving of fuel did not agree. If you prevented smoke, you burned more fuel.” Chris Newman asked why this should be […]
Stuart McIntosh from Australia commented: “Higher boiler pressure must mean a smaller (lighter) piston disc and less unbalanced mass and reduced hammer blow. Efficiency would also be increased.” Chris Newman’s replied to say: “Higher boiler pressure would provide all sorts of benefits, not least being higher efficiency. And you’re right too that it would mean […]