SR Z Class

The SR Z Class was a series of eight outside-cylinder 0-8-0 heavy shunting tank locomotives designed by Richard Maunsell and built at Brighton Works in 1929, specifically intended for heavy hump shunting at Feltham marshalling yard in Middlesex — the large SR freight sorting facility that had been built in 1921 and was served by the earlier LSWR G16 4-8-0T hump shunters. The Z Class provided more powerful shunting capability than the G16, with eight coupled wheels giving maximum adhesion for pushing heavy wagon rakes up the hump at the controlled, low speed demanded by gravity-hump marshalling yard operation.

Maunsell designed the Z Class at Brighton in 1928–29, specifying outside cylinders and Walschaerts valve gear for accessibility in the confined Feltham yard environment where maintenance had to be carried out rapidly between shunting turns. The 0-8-0T wheel arrangement — all eight wheels coupled and driven, with no leading or trailing carrying wheels — gave the maximum possible tractive effort from the locomotive's weight and was essentially identical in concept to the LSWR G16s it supplemented at Feltham. The Z Class was slightly more powerful than the G16, with larger cylinders and higher boiler pressure.

In service the Z Class worked Feltham hump shunting alongside the G16s through the SR and BR periods, remaining at Feltham throughout their working lives as the G16 had done. All eight examples were withdrawn by 1962 and none was preserved, though the Z Class represents an important specialist type in SR locomotive history alongside the G16 Class that preceded it at Feltham.