Even with increased pressure, this effect will be more appreciable when the area and travel of slide valve are in excess.
The slide valve is usually driven by an eccentric attached to the main shaft.
The cylinder A has a steam chest B, which contains therein a slide valve C to cover the ports at the ends of the cylinder.
In setting the slide valve of an engine having a link motion, there are two distinct operations.
The lap of a slide valve is the distance it extends over the edges of the ports when it is at the middle of its travel.
Second, because the steam is wire drawn during the time that the slide valve is closing the port to effect the cut off.
The reasoning applied here would hold good also to a less extent on the slide valve, but is not the point of absolute cut off.
The slide valve nut may have slackened back, thus loosening the slide valve.
The slide valve is now shifted to its first position and the process is repeated.
The reciprocating motion of the slide valve is nearly always derived from an eccentric fixed on the crank-shaft of the engine.