In addition to the design work of the cylinders themselves, work has been progressing on the production and assembly of the cylinder drain cock gear.  For those unfamiliar with these, the drain cocks overcome an inherent problem with steam locomotives, that of water condensing in the cylinders themselves.  Since water doesn’t compress well, starting a piston-valve or poppet fitted locomotive with water in the cylinders can result in significant damage.  To allow this water to escape steam locomotives are fitted with manual (sometimes steam operated) drain valves, three per cylinder, actuated from the cab by the locomotive crew.  The drains are normally left open when the locomotive is standing and for the first few revolutions when it starts moving, allowing egress of any condensed water, hence the clouds of steam in front of British locomotives when they initially start moving (US and European locomotives often have the valves aimed outwards from the cylinder).  In addition the cylinder ends are usually fitted with a pressure relief valve but this is designed to release excess steam rather than water.  To operate all three sets of drain valves simultaneously, cross shafts and a linkage back to the cab are required, all of which have to be fitted between the locomotive’s frames or along some other route from the front of the engine to the lever in the cab, in this case on the fireman’s side.

Cylinder drain cock linkage rocker bracket – Daniela Filová

Cylinder drain cock linkage rocker bracket and in-to-out bracket – Bob Hughes

Cylinder drain cock linkage rod ends – Bob Hughes

Cylinder drain cock linkages – Daniela Filová

Cylinder drain cock linkages – Daniela Filová