Dean Single Achilles Class
Class: Dean Single Achilles Class
Designer: William Dean
Weight: 50 tons (not including tender)
Purpose: Mixed Traffic
Information: A total of 79 Dean Achilles Class Single wheelers built between 1891 and 1899 for express passenger services out of Paddington by the Great Western Railway. Built during the period of conversion to standard gauge, the first thirty members were built with a 2-2-2 wheel arrangement, with the first eight also featuring convertible frames with the eminent demise of the broad gauge infrastructure.
Details: Typical of conventional engineering during the late 19th century, speed meant large driving wheels on a single driven axle. The Achilles Class featured enormous 7’-8-1/2” diameter driving wheels with two internal cylinders between the frames. Also typical of the era was the original 2-2-2 wheel design. The 2-2-2 locomotives being later converted to the familiar 4-2-2 wheel arrangement after an accident involving a broken axle in Box tunnel during 1893. The broken axle shaft was blamed on front end weight associated with the larger boilers being used on the class.
As express passenger locomotives the class took on individual names. Livery was GWR lined green. Several class members were allocated to Royal Train duties. No. 3065 “Duke of Connaught” made a record-breaking run with the “Ocean Mail” on 9th of May 1904, covering the distance from Plymouth to Paddington in 227 minutes.
Engineering of steam locomotives took a tremendous leap forward in the early twentieth century resulting in many rebuilds. Consideration of converting the design to a 4-4-0 wheel arrangement by George Churchward was considered during the early 20th century; but not pursued due to difficulties associated with converting the frames because of the large driving wheels, resulting in withdrawal of the entire class between 1908 and 1915. All were scrapped.