William Dean's Express Tank - MikeOxon's Pre-Grouping Blog - RMweb
Bonhams : A finely engineered 10 inch gauge (scale 8.221) live steam model of a broad gauge GWR 4-2-2 Rover class Express locomotive 'Dragon', The original designed by Daniel Gooch, model built by Ken Woodham,
THe parts diagram for the linkage/valve gear
Blender Tutorial: Stephenson, Gooch, Allan Valve Gear Animation - YouTube