6o8

MODERN STEAM PRACTICE.

hollow or tube section has been adopted; this plan for guiding thepiston rod in a true line necessitates a long fork on the connectingrod. This peculiar arrangement, as applied to the locomotiveengine by Messrs. Sharp & Stewart of Manchester, has not foundrnuch favour. It is, however, decidedly more cheaply executedthan the ordinary motion bars and adjuncts, but we think itshould be confined to agricultural engines, moving at a slow rateof piston.

The plate for carrying the back end of the motion bars is forgedin some instances, with provision for carrying the end of the pump;and has Hanges at the end fitting against the longitudinal frames,to which it is securely bolted. In other arrangements the motionplate is formed of plate iron, with angle-iron Hanges for securingit to the main framing. It is generally made of considerable depth,with holes cut out for the connecting rods and eccentric motionrods, and sometimes the plate is carried up and securely rivetted tothe boiler, in fact, forming the support for the boiler; this is tobe preferred to the old method, having the boiler brackets boltedthereto, and likewise to the rigid framing, as the plate is not sorigid, yielding to the expansion and contraction of the boiler. Themotion plate for outside-cylinder arrangements is carried beyondthe framing, extending the whole width across the framing, with along hole cut out for the wheel coupling rods, working through theplate extending from nearly the centre of the boiler to within a fewinches of the rails.

Connecting rods .— Much attention has been paid to the con-struction of the connecting and the coupling rods. The body andthe straps are of scrap iron, with brass bushes and Steel cotters.The length of the connecting rod from centre to centre should besix times the length of the crank, and even longer when convenient,shorter connecting rods throwing an undue strain on the motionbars, causing much friction. In former examples the body of theconnecting rod was turned, but this plan, although cheaper, wasobjectionable. Flat sections are now universally adopted, as thatform gives rods much stiffer, and better calculated to take the severestrains they are subjected to. Long forked connecting rods should,as far as practicable, be discontinued, as forked ends are not nearlyso strong as plain ends; short forks, however, are extensivelyadopted, and are not so objectionable, although we decidedly prefersingle ends.