LNWR 2-2-2 3020 'Cornwall'
Built at Crewe in 1847 to a Francis Trevithick design.
Cornwall was an attempt to avoid the damaging long wheelbase of the Crampton designs (with the driving axle behind the firebox), whilst still permitting large driving wheels. By moving the driving axle ahead of the firebox, one of the carrying axles could be moved backwards, giving a shorter overall wheelbase. The difficulty of how to fit the axles past the boiler recurred, to which Trevithick provided an "extremely complicated" solution. The boiler was placed entirely underneath the driving axle. Even then, it was necessary to recess a transverse channel across the top of the boiler, so as to provide clearance for the driving axle. The trailing carrying axle passed through a crosswise tube through the middle of the firebox. This made assembly difficult, but as it was only a straight carrying axle rather than a cranked driving axle, the tube diameter required was manageable. This use of a cross-firebox axle tube was part of Crampton's patent of 1842. As completed in 1847, and first numbered 173, Cornwall was a 4-2-2 with 8' 6" drivers, paired leading wheels of 3' 6", single trailing wheels of 4' and an overall wheelbase of 16' 6". It was extensively rebuilt and converted to a 2-2-2 in 1858