DETAILS OF SCREW ENGINES. 303
piston rod is attached by the T head, and thesecuring bolts connect the rod, block, and cap.The slipper portion is separate: the line ofcontact being angular, adjustment is effectedby the set nuts at the front end. The applica-tion of this block will be more readily seen byreferring to Plate 26.
As far back as the year 1862, we adoptedthe slipper type for return action engines,attaching the cross-head at the bach of theblock, which was illustrated in our “ Practi-cal Illustrations” in the year 1864, and dulyreferred to in our “ Practical Rules ” of thesame date. Messrs. Napier have lately intro-duced the same type of block, now illustrated
MESSRS. NAPIER’S DOUBLE PISTON ROD GUIDE BLOCK.
% Fig. 166, for return action engines. Thecross-head is an angular portion, with eyes atea ch extremity to support the piston rods;a bove and below the crank shaft, the rods aresecured in the cross-head by nuts. The blockis almost solid, the separate portion at thefront between the securing bolts being forthe purpose of adjusting the brasses when
requisite. The securing bolts are fitted ateach end with nuts and check nuts, thusequalizing the effect of the strains at theextremities. The slipper is a separate plateinto which the base of the block is recessed,with a dovetailed connection to prevent loose-ness. When the wearing surface of theslipper requires repair, the back end of thesame is removed, and the disconnection thusreadily effected. The connecting rod for thisand the former example is forked, and thepin merely a straight rod. The arrangementof engines in Plate 28 clearly pourtraysMessrs. Napier’s mode of applying the blocknow under notice.
To obviate the forked end of the connect-ing rod is the aim of many engineers; andMessrs. Maudslay accomplish this by adopting
Fig. 167.
= 3 *
MESSRS. MAUDSLAy’s DOUBLE PISTON ROD GUIDE BLOCK.
the form of block, as shown in Fig. 167, for areturn action engine. The cross-head is