Joy valve gear is a type of steam locomotive valve gear, designed by David Joy (1825–1903), Locomotive and Marine engineer, and patented in 1870. The movement is derived from a vertical link connected to the connecting rod. The vertical movement is translated into the horizontal movement required by the valve spindle by a die block moving in a slide which can be varied in inclination. The necessary 90 degree phase shift is obtained not from an eccentric, as with most designs, but from the 90 degree phase difference between the horizontal and vertical components of the motion of the connecting rod.
[edit] Applications
Joy valve-gear was used extensively on Lancashire and Yorkshire Railway and London and North Western Railway locomotives, and also on the Manning Wardle-built narrow gauge 2-6-2 locomotives of the Lynton and Barnstaple Railway. Joy gear was also used by John Fowler & Co. and several other steam traction engine manufacturers.
[edit] Preservation
The last locomotives with Joy valve gear to remain in service with British Railways were the LNWR G2 and G2A classes, one of which is preserved.
[edit] References
[edit] See also
- Extracts from the Diaries of David Joy: [1]
- A software simulation of Joy - and other common valve gear configurations - is available for download from: [2]
