 The design also featured raised running plates above the wheels , which allowed easy access to the inside of the frames for purposes of lubrication . The lack of wheel splashers on this running plate also reduced the risk of the bearings overheating , by allowing more air to flow around the axles when at speed . Wheel splashers were used on older locomotive designs to box @-@ in the top portion of the driving wheels for aesthetic reasons , and to prevent water and dirt from being thrown at the cab windows . The " <unk> ' " footplate was designed around the requirements of the operating crews , with a mock @-@ up being constructed at Crewe to test ergonomics and usability . For ease of maintenance , availability of spare parts and increased reliability , two sets of Walschaerts valve gear were used , along with the largest cylinders capable of staying within the British loading gauge . The " inside " cylinders located between the frames of a three- or four @-@ <unk> locomotive are difficult to access for maintenance ; the two @-@ cylinder design of the Class 7 – with all the valve gear on the outside – avoided these maintenance problems . Boiler ' plumbing ' was also generally exposed to maintain ease of access . In common with other BR standard designs there was no exhaust injector , as this device was temperamental unless rigorously maintained . 
