Gresley conjugated valve gear

LNER Class V2 4771 Green Arrow. Note Gresley conjugated valve gear located ahead of the piston valves, driven from the valve spindles

The Gresley conjugated valve gear is a valve gear for steam locomotives designed by Sir Nigel Gresley, chief mechanical engineer of the LNER, assisted by Harold Holcroft. It enables a three-cylinder locomotive to operate with only the two sets of valve gear for the outside cylinders, and derives the valve motion for the inside cylinder from them by means of levers (the "2 to 1" or "conjugating" lever and the "equal" lever).[1] The gear is sometimes known as the Gresley-Holcroft gear, acknowledging Holcroft's major contributions to its development.

  1. ^ Restoration of Gresley A4 #60019 Bittern Archived 12 March 2007 at the Wayback Machine Diagram of Gresley and Walschaerts valve gear arrangement on LNER A4 locomotive - retrieved 4 October 2006 [dead link]