Bagnall–Price valve gear

[1] The valves are driven from an eccentric cam mounted on one of the driving axles and linkage from the crosshead.

The driving axle cam drives a rocking shaft that is mounted inside a cylindrical sleeve (known as the rocking shaft bush) above the cylinder.

A drop lever and connecting link from the crosshead oscillates the sleeve to control the lap and lead of the cylinder.

[2] According to Baker the Bagnall–Price valve gear had only one common feature with the preceding Baguley valve gear, namely that "the application of the lap and lead motion by oscillating the expansion link (or sector) bodily, and thus superimposing this motion on the.

normal die block travel, the lead remaining constant in all positions of the gear.

Bagnall–Price valve gear on an 18 in gauge Bagnall product at the Kimberley diamond mine museum, South Africa
Schematic diagram showing the major components of the Bagnall–Price valve gear