David Joy

David Joy (1825–1903) was a British engineer and prolific inventor, best remembered in railway history as the designer of Joy's radial valve gear (1879), which was widely fitted to late-Victorian British locomotives, particularly to LNWR engines under Francis Webb, and offered a simpler, lighter alternative to the Stephenson and Walschaerts gears.

Born at Leeds on 3 March 1825, Joy was apprenticed at Fenton, Murray and Jackson and worked at E. B. Wilson & Co. of Leeds (the Railway Foundry). He served as Manager of the Atlas Engine Works in Bradford and then on his own account, designing marine and stationary engines as well as locomotives. His Jenny Lind 2-2-2 single for the LBSCR in 1847 was an early notable design. He kept careful diaries through his career, which together with his autobiographical sketches form an important source for early Victorian engineering history. He died at Hampstead on 14 March 1903.