The Z class was the only Maunsell eight-coupled design to materialise, although there were plans for others. It was designed and produced for the specialist role of heavy shunting in hump and marshalling yards. In doing so a considerable number of standard parts and an existing Brighton boiler design were utilised, this class also incorporating the experience of the Urie G16 class 4-8-0T which had been produced for the same purpose. The specialist requirements were for a locomotive which was capable of delivering a lot of power after lengthy periods of idling, to do so without excessive blowing off and slipping, being quiet in operation and to be able to negotiate tight curves.

30954 photographed in very early British Railways days at Exmouth Junction on 28 July 1949. She still has SOUTHERN on her tanks but has her BR number in Sunshine style numerals on her bunker.

To achieve the required specification a large water and steam capacity was required, the boiler selected was of the parallel non-superheated type with a moderate grate area of 18.6 sq ft and total evaporative heating surface of up to 1279 sq ft. The boiler pressure was 180 lb per sq in resulting in a tractive effort at 85 percent pressure of 29,380 lb. The water tanks could hold 1500 gallons and the coal bunker 3 tons. Three 16in diameter 28in stroke cylinders (interchangeable with those on N1 and U1 classes) were used, the outside pair driving the third axle through 11ft 6in connecting rods and the inside cylinder set at 1 in 8 driving the second axle. Walschaerts valve gear controlled the outside pistons, the inside one having custom designed gear. The wheels were of 4ft 8in diameter and the leading and trailing pair had sufficient sideplay so that curves of 4½ chains could be negotiated despite the 17ft 6 in wheelbase. The only adverse feature was the overhang of 11ft at each end which meant that the class could only be used where sharp curves were not in tight surroundings. Steam brakes were fitted as was vacuum apparatus and a steam reverser. Steam heating for passenger stock and banana vans was also provided. The overall result was a responsive, powerful engine practically immune to slipping with a very quiet beat.

photograph by the late Trefor David, courtesy of Mike Morant

Eight locomotives numbered 950-957 (30950-7 under BR) were built at Brighton works in 1929. Such was the success of the class that a further ten were planned for Eastleigh works in 1931 but were cancelled because of the economic climate. Instead with much farsightedness ultimately three diesel electric shunters were ordered. This class quietly and without ceremony went about its designed tasks successfully for its entire life, although they were not as successful at trip workings as the G16s. Three, 951/5/6, were loaned to the war department during World War Two and served in Scotland. Throughout their lives they were allocated to Ashford, Brighton, Dover, Eastleigh, Exmouth Junction, Gillingham, Hither Green, Salisbury, Templecombe, Three Bridges and Tonbridge. Towards the end of their lives they took their turn on banking duties up the 1 in 37 hill from Exeter St Davids to Exeter Central. Their appearance was largely unchanged throughout and the entire class was withdrawn throughout 1962. Regrettably none is preserved.

photograph: Mike Morant collection