Crampton locomotive
A Crampton locomotive is a type of steam locomotive designed by Thomas Russell Crampton and built by various firms from 1846. The main British builders were Tulk and Ley and Robert Stephenson and Company.
Notable features were a low boiler and large driving wheels. The crux of the Crampton patent was that the single driving axle was placed behind the firebox, so that the driving wheels could be very large. This helped to give this design a low centre of gravity, so that it did not require a very broad-gauge track to travel safely at high speeds. Its wheel arrangement was usually 4-2-0 or 6-2-0.
Design variations
Because the single driving axle was behind the firebox, Crampton locomotives usually had outside cylinders. However, some inside cylinder versions were built using indirect drive, then known as a jackshaft. The inside cylinders drove a crankshaft located in front of the firebox and the crankshaft was connected to the driving wheels by outside rods. Some long-wheelbase 0-4-0 tank locomotives were also built using this crankshaft system. The boiler feed-pump was often driven from the crankshaft as well because many Cramptons were built before the injector was invented.
