GWR 5700 Class - The 9700 Class

The 9700 Class

The 9700 Class Pannier Tanks were a direct development of the 5700 Class. The prototype for the class, No.8700 (later 9700), was a rebuilt 5700 locomotive. They were specifically for working on the Metropolitan/Hammersmith & City lines between Paddington Stations and Smithfield Meat Market. They replaced 'Metro' and '633' class locomotives.

The eleven locomotives in the class had condensing apparatus that fed the exhaust steam back into the water tanks. The tanks themselves were shortened to make room for the external exhaust pipes and were extended down to the footplate in front of the cab to increase their capacity. As condensing the steam heated the water, a reciprocating pump (Weir pump) was fitted as a boiler feedwater pump because standard injectors will not work with hot water. The pumps led to (unsuccessful) tests with these locomotives acting as fire engines during World War II.

To work over the electrified underground lines, the 9700 Class locomotives had a special type of ATC equipment that lifted clear of the centre rail and had tripcock brake valves that matched the London Transport signalling system.