304

DETAILS OF SCREW ENGINES.

angularly formed, the position of the eyescorresponding with that of the piston rods,and the centre part is turned to receive theconnecting rod. The block, it is seen, hasraised sides, each supporting the cross-head,the connection being effected by the caps,nuts, and studs. The form of the guidingportion is dovetailed or angular at the sides,and the slipper is similarly connected as thatin Fig. 166—the adjustment in the presentexample being by studs acting vertically onthe slipper at the ends of the block.

The more universal mode of guiding thecross-head for single-end connecting rods isshown by Fig. 168. This is attained by

Fig. 168.

TUT TOT

MESSES. EAVENniLLS MODE OF GUIDING THE CROSSHEADSOF RETURN ACTION ENGINES.

double guides, one on each side of theconnecting rod on the centre link of motion,rather than below it, as in the previousexamples. The blocks are merely plates ofgun-metal with flanges, and suitably con-nected to the cross-head.

Messrs. Rennie have also adopted this modeof guidance, and many other firms who con-struct engines of all classes of single and returnaction. Messrs. Napier have fitted in theDanish armour-plated cupola ship “Rolfkrake”engines with single guide blocks, having the

connecting rods—single ends — inserted inthem, which will be better understood byalluding to Fig. 8 in page 60, and the descrip-tion in page 61.

CONNECTING RODS.

In close proximity with the guide blocksare the connecting rods—being, in fact, themain motion details of the engine. Theoriginal type of head of the rod was the strap,gib, and cotter. This has, however, given placeto the flat brass, and T end, and the semi-solid head. The flat brass head has beenbrought to its present form by Messrs. Penn,who have developed what the correct propor-

Fig. 169.

Messrs, penn’s connecting rod head.

tions should be. The illustration, Fig. 169,is partly in section and complete, and showsthe design of the firm in question. Thesecuring bolts are as near the bearing as thethinness of the brass will permit, thus reducingthe material, while retaining the correct lo-cality for the bolts; that being as near thecentre of motion as practicable. The nuts arerecessed in the cap, and set screws preventlooseness by bearing in the grooved portion ofthe nuts. The connection for the lubricatoris not seen, but can be understood by referringto the example in Plate 27.