Technical | Winders | North | Engine | Valves  >  Expansion gear

Section under development

The purpose of the expansion gear was to cut off the steam to the cylinder at an earlier than normal point as the speed of the winder increased, allowing it to do work by expansion, resulting in a much more economical operation. The details of the expansion gear on the original Worsley Mesnes engine are unknown but the Lilleshall engine utilised a Mellings Patent rising-wedge cut-off device.  At some point after 1966, the governor operating link was disconnected and the engine was run with no cut-off.  The reason for this is not known.  Unfortunately the trip operating mechanism itself was also removed although the Lilleshall drawings for it still exist.

N-winder governor-side elev 2 -s02

Lilleshall drawing (1931) showing expansion mechanism arrangement.  (FoPP/JST)

The mechanism consisted of a wedge-shaped block which could slide up and down the upper section of a pivoted bar inside the central frame. The lower end of the bar was connected to a “rocker” shaft operated by an eccentric on the drum-shaft.  The wedge was lifted by the operation of the governor, and as it did so, it came closer to the ends of two rods from the valve lifting mechanism.  As the wedge oscillated to the right and left, it pushed the rods and tripped catches which disconnected the valve rods from the tappets, thus allowing the valve to close early.  The greater the speed, the more the wedges were lifted and the earlier the trip mechanism operated.

N winder 1960s 1 -m

In this grainy photo from the late 1960s, the operating mechanism and governor linkage is still in place. The governor can just be seen on the RH edge, the balls partly hidden by a funnel shaped cover. The RH rocker lever can be seen but the link-rod is out of sight behind the cylinder.

P6170824c -s

RH side operating mechanism housing - minus the internal mechanism.

Melling trip dies 1

Inlet valve trip mechanism


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05 Jan, 2018


01:43:24 PM

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