Gresley conjugated valve gear [SEP] named after
Gresley conjugated valve gear
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 lever" and "equal lever"). The gear is sometimes known as the Gresley-Holcroft gear, acknowledging
Holcroft valve gear
The Holcroft valve gear was a type of conjugated valve gear designed by Harold Holcroft and used on three-cylinder steam locomotives of the South Eastern and Chatham Railway (SECR). It bore many similarities to the Gresley conjugated valve gear used on the original LNER A1 design. It varied from the Gresley method of operation by using the combination lever assembly instead of the valve spindles to drive the middle cylinder of a three-cylinder design. This had operational advantages over Gresley's design.
Background.