GWR 4000 Class

GWR 4000 Class

A Star class locomotive was a particular type of steam locomotive of the Great Western Railway. The prototype was an experimental locomotive, North Star (originally given number 40), constructed with the 'Atlantic' 4-4-2 wheel arrangement for comparative trials with 4-cylinder compound locomotives of the de Glehn type that had been purchased from France. This established the benefits of the balanced 4-cylinder layout but the designer, George Churchward, decided that he would continue the class with simple steam expansion, and also with the 4-6-0 wheel arrangement he had introduced with the 2900 class. As in the de Glehn design, the outer cylinders drove the centre driving axle, the inside pair of cylinders were set well forward and drove the leading driving axle.

Construction of the production class began in 1907. In the production class (4001 to 4072) there were just two set of Walschaerts valve gear between the frames, the valves to the outside cylinders being driven by rocking levers.

An enlarged version of the design was introduced in 1923, as the Castle Class, of which about 170 were constructed, including some rebuilds from the 'Star' class.

One example of the 'Star" class, 4003 Lode Star, survives in preservation as a static, non-working, exhibit. On withdrawal from service, it was overhauled and repainted at Swindon Works, and as such is a rare example of a locomotive untouched since overhaul by preservationists. As a result of this, it is unlikely that it will ever be restored to operating condition.