BR Standard Class 4 2-6-4T - Design and Construction

Design and Construction

On the decision to build the BR standard series of locomotives, a series of class four tank engines was ordered, based on the ex-LMS Fairburn 2-6-4T with some modifications. The lineage of the class could therefore be tracked through the LMS/BR Class 4 2-6-4T locomotives back to the Fowler design of 1927.

Design work was done at Brighton, the overall programme being overseen by R.A. Riddles. The principal modifications to the Fairburn design involved the reduction of their envelope to enable them to fit into the L1 loading gauge. To do this the tanks and cab were made more curved than the Fairburn design, the Fairburn having a straight-sided tank. The biggest mechanical change was a reduction in cylinder size, also to reduce cross-section, and a corresponding increase in boiler pressure to compensate. Other visible changes include the reintroduction of plating ahead of the cylinders.

130 of the class of 155 were built at Brighton, 15 (80000–80009, 80054–80058) at Derby Works and 10 (80106–80115) at Doncaster Works between 1951 and 1956. The first to emerge was 80010 from Brighton in 1951. Fifteen that were due to be constructed in 1957 were cancelled due to impending dieselisation, and the last five would have been too had they not been at an advanced stage of construction when the order came to cancel them.

No significant modifications were made to the design. The tank vent was found to restrict the driver's vision and was moved further forward from 80059. Initially built with fluted coupling rods, these caused problems on other classes and from 80079 plain section coupling rods were substituted.

The BR standard class 4 4-6-0 was essentially a tender engine derivative of the Standard Class 4 tank.