Geared steam locomotive
This gearing is part of the machinery within the locomotive and should not be confused with the pinion that propels a rack locomotive along the rack between the rails. The geared steam locomotives that have been built have been for conventional track, relying on the adhesion between wheels and rail.
Holcroft valve gear
When working for the GWR at Swindon, Holcroft schemed out and patented (in 1909) a conjugated valve gear for three-cylinder steam locomotives, which allowed for the elimination of the valve gear for the inside cylinder by deriving the motion for the inside valve from that of the outside valves. This would be done by an assembly of levers behind the cylinder block.