BR standard class 4 tank: Encyclopedia II - BR standard class 4 tank - Design and construction

BR standard class 4 tank - Design and construction

On the decision to build the BR standards, a standard class of class four tank engines was ordered, based on the ex-LMS Fairburn 2-6-4T with some modifications. The Fairburn tanks themselves had been based on the LMS Stanier 2-6-4T which in turn had been based on the LMS Fowler 2-6-4T.

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 a fall plate.

90 of the class of 115 were built at Brighton, 15 (80000-9/54-8) at Derby and 10 (80106-15) at Doncaster 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 in an advanced stage of construction when the order came to cancel them.

The BR standard class 4 4-6-0s were essentially a tender engine derivative of the standard four tanks.

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.

Adapted from the Wikipedia article "Design and construction", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki