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The Ultimate Steam Page

Steam Improvements of the Last 30 Years

updated September 27, 2002

Duke of Gloucester No. 71000

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: