Sharps Planet

Sharp's Planet refers to the 2-2-2 inside-cylinder locomotive design manufactured by Sharp Roberts & Co. of Manchester from 1839, which was a contractor-built version of Robert Stephenson's celebrated Planet Class configuration — the 2-2-0 design of 1830 that had established the basic layout of the steam locomotive (subsequently developed into the 2-2-2 Patentee by addition of a trailing axle). Sharp Roberts, one of the pioneer private locomotive builders of the early Victorian era, adopted and refined the Stephenson Planet configuration to produce a standard design that could be offered to the growing number of new railways seeking motive power during the railway expansion of the late 1830s and 1840s.

The significance of Sharp's Planet lies partly in its locomotives and partly in what it represented: the emergence of the private locomotive manufacturer as a major force in British railway development, supplementing and eventually in many cases superseding the locomotive building capability of the railway companies themselves. Where the early railways had largely relied on Stephenson's Newcastle works or their own embryonic workshops, companies like Sharp Roberts offered an alternative source of reliable and increasingly standardised locomotive designs that gave the explosion of new railways in the 1830s–40s access to proven motive power without the delay of building their own works.

Sharp Roberts supplied their Planet-derived locomotives to numerous new railways of the late 1830s and 1840s, contributing to the rapid expansion of the British railway network during the railway mania period. None of the original Sharp's Planet examples was preserved, though the Planet configuration they represented lives on in the working replica at the Science and Industry Museum, Manchester.