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London & North Western Railway Society
The LNWR Company

Engines for Shunting

While the Edge Hill  ‘Grid Iron’  used gravity to shunt wagons, tank engines were needed in most yards. Shunting  did not require large supplies of fuel — coal and watering facilities were nearby and easily visited — so a separate tender  was not required. The fuel could all be carried around the engine. In tanks the weight of water over the driving wheels  contributed to adhesive weight, while in some designs water was kept in ‘saddle’ tanks  mounted on top of the boiler — this made access to working parts easier for maintenance.
Since a tank had no tender, it was much easier to judge when the buffers came close to the train – ‘buffering-up’ was a delicate operation, even more difficult in the dark. Inanimate goods might not complain at a ‘rough shunt’ as passengers would, but much damage might be caused.
Shunting required frequent changes of direction, for which the reversing wheel  of LNW engines had to be spun from full forward to full back, and vice versa repeatedly, requiring much strength and energy. One driver experienced at shunting at Stafford could remember exactly how many turns fore-to-aft decades later! Only the later eight-coupled tanks had the quicker lever reverse .
Small driving wheels, all driven, enabled good acceleration, particularly important if running lines had to be crossed in between trains. Brakes needed to be quick in operation yet were rarely fully tested.