Sharp Single

The Sharp Single designation covers the range of 2-2-2 inside-cylinder single-driver express passenger locomotives manufactured by Sharp Roberts & Co. and its successors Sharp Brothers and Sharp Stewart & Co. of Manchester through the 1840s–1870s, representing the mature development of the contractor-built single-driver express locomotive that Sharp supplied to railways across Britain and increasingly across the world as the firm's reputation and capabilities grew. The Sharp Single was a refinement of the earlier Sharp locomotive types, incorporating the improvements in boiler design, valve events, and wheel dimensions that experience had shown to give the best performance from the single-driver 2-2-2 configuration.

By the 1850s Sharp Stewart had become one of the leading locomotive manufacturers in Britain, with an export trade that supplied locomotives to India, Australia, South America, and continental Europe alongside its home market deliveries. The Sharp Single represented the firm's standard high-speed express type: a well-proportioned inside-cylinder 2-2-2 with driving wheels up to 7 ft in diameter, capable of the sustained express running that the expanding British railway network demanded of its passenger motive power through the 1850s and 1860s. The large driving wheel gave the smooth, vibration-free running at speed that made the single-driver so valued for express passenger work before the heavier trains of the 1870s and 1880s demanded the greater adhesion of coupled wheel types.

None of the original Sharp Single locomotives from the 1840s–70s was preserved, though the type they represent — the mid-Victorian express 2-2-2 — is well documented through engineering drawings, the work of contemporary illustrators, and the preserved GNR Stirling Single No. 1 at the National Railway Museum, which represents the ultimate development of the large-wheel single-driver express tradition.