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The double beat Cornish valves on the Lilleshall engine are positioned between the cylinders. The valves and their seats are of gunmetal, the latter being bolted into the valve casing and can be fairly easily removed for re-machining of the faces. Each pair of inlet valves are individually connected to a common steam main running between the cylinders below floor level.  Each pair of exhaust valves is connected to an exhaust main running alongside each cylinder below floor level.

As designed, valve closing was by gravity but later the inlets were  assisted by a spring fastened between one of the metallic packing bolts and the trip die housing. The final lowering onto the valve seats was controlled by pneumatic dash-pots with the inlet ones having an external tap to adjust the rate.

P6170822b -m03

RH side - valve gear and expansion mechanism casing. (The bearing caps have been temporarily removed)

North  winder  LH side -  valve gear

North  winder  LH side -  Cornish valve gear and steam ports

BD05378_02a

see the operation of a double-beat Cornish valve

Each cylinder has a small drain hole cast in the bottom of the steam port whilst the valve blocks have a drain hole cast in the outer wall. 

The LH cylinder drains have 1/4-turn taper-plug cocks whilst those on the RH cylinder are fitted with blanking plugs. These drain-cocks are not easily accessible and were probably never used. The blanking off of the RH was most likely done when the cylinder was removed for the bed-frame replacement.

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LH rear cylinder drain-cock

DSC01375 -s

LH front cylinder drain-cock

DSC01450 -s

RH rear cylinder-drain plug

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RH front cylinder-drain plug

The valve chamber drains also differ between the two cylinders, with the LH fitted with a combined drain cock and blow-off valve whilst the RH side has a drain cock only - possible another consequence of the bed-frame repairs.

P6170823b -s

LH  valve drain cocks under restoration

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