| The Duke of Gloucester was
designed by Robert Riddles in 1952 as the
prototype for a new generation of steam passenger
engines for British Railways. Chief among the
locomotive's advanced features was the use of British Caprotti valve gear, a form of
rotary cam poppet valves. The locomotive was
completed by Crewe Works in 1954. When the Duke was
tested on the Swindon Test Plant, it was found to
have the highest cylinder efficiency of any
simple expansion engine on record and subsequent
trials showed it to be significantly more
powerful than any comparable type. Despite this,
however, the locomotive was known for having
difficulty steaming and was unusually heavy on
coal consumption. Shortly after Mr. Riddles
retired, BR management decided to withdraw steam
and dieselize as soon as possible. This prototype
was destined to become a "one of a
kind" locomotive, and due to the short
future of steam the locomotive's problems were
not investigated and corrected.
When the
locomotive was retired in 1962, it was initially
planned tobe preserved as part of the British
National Collection. However, because of the
steaming difficulties, the engine was considered
unsuccessful and deemed not worthy of
preservation. The locomotive's cylinders with
Caprotti valve gear were removed, and the right
one was sectioned and placed in the Science
Museum in Kensington. The Duke languished for the
next 10 years in the famous Barry Scrap Yard
without much hope of being saved.
In 1973, a group
was formed which rescued the locomotive and
declared that it would be restored to service.
Not only did new cylinders have to be cast and
machined, but a myriad of smaller components
required fabrication as well.
During the
restoration, two significant flaws were found in
the engine. The ashpan had been constructed
incorrectly, restricting the airflow to the
grates. A comparison of the locomotive's double
exhaust stacks showed the entire exhaust system
to be too small compared to other British
locomotives of comparable size. Based on this, a
new dual Kylchap system was designed and fitted
to the locomotive during its restoration. The
group gained confidence that the engine's
mysterious steaming difficulties had been solved.
When No. 71000
re-entered service in 1996, the locomotive proved
to be a transformed machine. It easily exceeded
its former performances and astounded former
enginemen who had known it during its BR days.
Very
interestingly, the work required during the
initial restoration generated an enthusiasm for
researching and developing continuing
improvements for the engine. After several years
of service, further improvements were made to the
ashpan. The water capacity of the tender was
increased and a coal pusher was constructed and
added to ease the firemen's jobs. New camshafts
of an altered profile to provide more complete
steam expansion were recently fitted. An
auxillary water tender is under construction to
increase the engine's operating range. Finally, a
design flaw was recently discovered in the
cylinder heads, which restricted the steam flow
into and out of the cylinders. This has been
corrected on 4 newly fabricated cylinder heads
which should significantly increase the
locomotive's already high cylinder efficiency.
For more on the
Duke, visit their website at: http://www.71000.org.uk/
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