It was introduced to meet the need for considerably more powerful heavy freight locomotives than any of those designed by the former Railway Companies. It was intended that they should be capable either of hauling heavier trains or of maintaining higher average speeds than could the older regional types. 

This Bulletin was concerned with the performance of the design as it emerged, except for a few minor modifications and also formed the basis for the allocation of locomotives of the class to the duties for which they were best suited and to enable those duties to be performed within the most economical range of the locomotive in so far as the Operating Department's requirements were satisfied. It did not cover any of the later variations from the original design.

The test results were also presented as a record of the performance of the design of what was expected to be the last class of steam locomotive to be built for the railways of Great Britain. (It certainly was).

The presentation of the data in this Bulletin was divided into two main parts.

The first defined the relationship between coal as fired, water as drawn from the tender, tractive effort and horsepower both as available at the drawbar, data directly applicable to the immediate commercial purpose of examining train loadings and schedules to obtain reduction in fuel consumption by working the locomotives where possible nearest their point of maximum operating efficiency.

The second part was concerned mainly with thermal efficiency, giving data on a basis of indicated power, covering boiler and cylinder efficiencies, factors of more importance in locomotive design. .

The tests were planned and carried out partly by the Locomotive Testing Station at Rugby and partly by the Locomotive Testing Section of the Chief Mechanical and Electrical Engineer's Department of the London Midland Region using the Mobile Test Plant and this bulletin was prepared jointly by the staff at Rugby and Derby. The work was conducted on behalf of' the Locomotive Testing Joint Sub-Committee.

NATURE OF THE TESTS

The boiler and cylinder performances were first established by tests on the Stationary Testing Plant.

These tests were followed by tests on the line using the Mobile Testing Plant. On these the boiler efficiencies which had been established on the Stationary Plant were reproduced and the corresponding coal and steam rates were related to the work at the drawbar.

Two Standard Class 9F locomotives were fully tested, both at Rugby and on the line, and a third underwent a limited series of tests on the Stationary Plant. The data presented was that which was regarded as typical of the class.

Here are a few pictures of the tests and a summary graph.