GWR Thunderer locomotive

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Thunderer was the first of a pair of steam locomotives (the other being Hurricane) built for the Great Western Railway (GWR), England, by R. & W. Hawthorn & Co. whose design was very different from other locomotives. In order to meet Isambard Kingdom Brunel's strict specifications, an 0-4-0 frame carried the 'engine', while the boiler was on a separate six-wheeled frame. The driving wheels were geared 10:27 to reduce the cylinder stroke speed while allowing high track speed, in line with the specifications.

The locomotive was delivered to the GWR on 6 March 1838 and ceased work in December 1839^[1] after running only 9,882 miles (15,904 km), but its boiler section was kept as a stationary unit.

• GWR Haigh Foundry locomotives, further geared locomotives

• Reed, P. J. T. (February 1953). White, D. E. (ed.). The Locomotives of the Great Western Railway, Part 2: Broad Gauge. Kenilworth: RCTS. ISBN 0-901115-32-0.
• Waters, Laurence (1999). The Great Western Broad Gauge. Hersham: Ian Allan Publishing. ISBN 0-7110-2634-3 – via Archive.org.