DETAILS OF SCBEW ENGINES.

tice of Messrs. Penn, rather than any otherfirm.

To render the arrangement of the details in

Fig. 191.

PLUMMER BLOCK FOR SCREW SHAFT.

a screw alley and the means of connecting theshafting obvious, the illustration, Fig. 192,is introduced. This is a sectional elevation,

319

SCREW PROPELLERS.

In pages 10 to 14, inclusive, a brief noticeis given of the types of propellers at presentadopted, and those remarks may be considereda preface to this section. As already stated,the “ Common, Griffiths, and Mangin ” pro-pellers are the practice of the present day,and to these examples further attention is nowdirected.

The common type has two or more blades—four as a maximum—cast with the boss ; thepitch being therefore unalterable, as shown

Fis

192.

n t rn t

SCREW ALLEY AND FITTJNGS.

showing the turning gear, thrust and plum-lller blocks, supports, shafting, and stern tube,■^he propeller is keyed on the extremity of the8 haft beyond the stern post, thus the requisi-h°n of two thrust blocks, as depicted. The8 Wting is coupled by discs forged on theSarri e, and bolts and nuts secure the connection.

tubing and cocks are also shown for^ater lubrication during the occurrence ofheated bearings. The practice of Messrs. Penn,■^audslay, Watt, Ravenhill, Rennie, Napier,hfurnphrys, and the remaining leading firms,ls Dearly similar in connection with the fittingsscrew alleys; and the illustration nowEluded to is a truthful representation of actuala Qd general construction.

by Fig. 193. This is a three-bladed propeller,often adopted for twin screw propulsion, and is

Fig. 193.

COMMON I'KOPELLEB.

example constructed by many firms. The