Bagnall-Price valve gear

Bagnall-Price valve gear is a type of steam engine valve gear developed at locomotive manufacturer W.G. Bagnall as an alternative to the more common Walschaerts valve gear. The gear was patented in 1903 by W.G. Bagnall and T. S. Price, the manager of the works.

Layout

Schematic diagram showing the major components of the Bagnall-Price valve gear

Bagnall-Price valve gear on an 18 in gauge Bagnall product at the Kimberley diamond mine museum, South Africa

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.

Comparison to Walschaerts

W.G. Bagnall claimed that Bagnall-Price valve gear eliminated some of the complexity of Walschaerts gear, specifically the combination lever and return gear; this in turn meant the externally mounted gear had greater ground clearance which was an advantage in industrial locations where lineside obstructions could damage the gear of passing locomotives.

References

• Fairburn, Mike. "Bagnall Price Valve Gear" (– ^{Scholar search}). The Journal of the Welsh Highland Railway (121). 

• Baker, Allan C. (September 1966). "Bagnall Locomotive Valve Gear". The Industrial Railway Record (The Industrial Railway Society) 11: pp.264–270.