U4

MODERN STEAM PRACTICE.

as for the solid one could be given. Suffice it to say, however, thatwhen solid links are adopted the eccentric rods are connected to

Fig. 61.—Link Motion and Starting Gear for Marine Engines.

the ends of the link, one of the pins taking the lifting rod being con-nected to the lifting arm with similar mechanism as for the slottedlink. However, when the link is suspended from any other centrethan the true one, at or near the centre of the link, the motion ofthe valve is not so correct as with the plans described above. Forvery small engines we would certainly adopt the usual starting gearas applied to the locomotive engine, having a plain lever handlefitted with a catch, and quadrant notched to suit a varying expan-sion; but of course this must only be used where the strength ofone man is sufficient to work the valve-gearing.

From the brief sketch above given of some of the plans most inuse for giving motion to the slide-valves of the marine engine, itwill be seen that, where circumstances admit, the two formerexamples are the simplest motions, as having fewer working parts;and it must be borne in mind that simplicity in the machinery onboard ship is the main thing to be studied.

In concluding this part of the subject attention must be drawn toa species of valve and gear for working expansively, termed thegridiron expansion-valve, of which there are two kinds; one being