From the Ashes to a 21st Century Duke
The story of the development of the express passenger steam locomotive in this country is one of the
search for speed, hence power, within the constraints of the existing infrastructure, and with a keen
eye on costs, high reliability and low maintenance.
As the last express steam locomotive, 125 years down the line from Stephenson’s Rocket, the Duke
incorporated ideas and practices from the Big Four. In the choice of 3 cylinders we see the hand of
LNER man J F Harrison who was also impressed by the final version of the British Caprotti valve gear
as used on H G Ivatt’s Black Fives. The Duke was intended to incorporate all the best technology
and produce the ultimate UK passenger design.
Tests had shown that the Duke’s cylinder efficiency was the best achieved in this country, but that, at
the top end, it’s boiler performance was woeful. Despite the cylinder efficiency test results, it
developed a reputation for being heavy on coal and water. Because of flaws in the design which it
shared with other Standards, piston ring wear was very heavy, leading to loss of steam tightness. The
Caprotti gear performed admirably.
The restoration of the Duke’s rusting remains began in 1974 and the aims that masterminded its
triumphant reincarnation were promoted by the image of a Phoenix carrying the inscription Pro
Potentia Vaporis.
It was apparent from test bulletin that the Duke’s draughting needed attention, and the adoption of the
Kylchap system has, after minor adjustment, proved a complete success, with maximum output steam
rates of over 40,000 lb/hr delivering 3000HP and more at the cylinders. Over the years it has
erroneously been stated that an out of specification ashpan was the reason for the Dukes steaming
limitations on test.. Perhaps, understandable in the circumstances, the idea of a simple oversight that
answers all had it attractions, but this was without foundation – for the incorrect ashpan found at Barry
was likely fitted later. The Duke’s ashpan in preservation was built to the original workshop drawing.
For good steaming and a clear exhaust it is routinely operated with the rear damper fully closed or just
cracked open, as its designers intended. Clear testimony the damper area was, and is, more than
adequate.
The Duke has proved himself to be the equal of the best in terms of the power he delivers, and he has
firmly established himself as a star in the top rank of UK power. On today’s increasingly busy
mainlines, locomotives with the Duke’s power are essential to move economic loads quickly out of the
way of other traffic. Top class power is critical and both operators and fans alike need the Duke back
on the mainline.
One strength of the Duke seldom touched upon is the high superheat. Under typical working
conditions the steam temperature is around 50 or 60 degrees F higher than for a Duchess. All things
considered, and the steam rate of 30000 lbs/hr, the drawbar horsepower advantage to the Duke at 70
mph is about 60, roughly equivalent to the proverbial “extra coach“. There have been many great
Duke performances benefiting from this, and after making record climbs to Whiteball, Rattery,
Hemerdon and Dainton summits, Mike Notley was moved to write “May 28 th 2007 is another day that
will go down in steam history…The Phoenix has risen right to the top of the pile, and how”
There are however still ways to move the design forward. Reliability is crucial in today's world, also
the need to deliver top power in less favourable circumstances. Modern safety requirements for
traction is also needed to be met, and more sensors would help deliver consistently reliable outputs.
The areas of draughting efficiency, superheat and mechanical integrity are subjects for review. This
rebuild aims to create a Duke that fulfils all its designers intentions in terms of performance and
reliability and will incorporate new best practices needed for the 21 st century mainline. The rebirth of
the Duke from a rusting cannibalised hulk has proved a magnificent example of restoration and
technical advancement but there is more that can be done.
Given the opportunity for another mainline innings, the best may be yet to
come. The evolution of the Duke is not complete. It will look perfect in its
original 1954 condition, but inside it will be a different beast.
Please help to ensure the fulfillment of the “Impossible Dream”
Doug Landau
and
David Pawson
20th January 2015