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342 After all the planing operations are completed, the link blocks are fitted with composition gibs that bear on the link bars. These gibs are accu- rately machined to fit the curvature of the links and are provided with oil holes to insure proper lubrication at all times. Eccentrics Present Many Problems The eccentrics of any marine en- gine present serious problems, due to the fact that the space which can be allotted to them is generally lim- ited. As a triple-expansion engine carries six eccentrics, it is necessary to make four of them in sections due to the fact that a split design is re- quired to permit their being installed with set screws to facilitate getting the correct leads are firmly located on the crankshaft through the medium of keys embedded in the crankshaft. In machining a solid eccentric, the casting is located in the chuck on a vertical boring mill where the hole for the crankshaft and one side is turned at one setting. For. turning the other side and the periphery, the eccentric is located by its hole on a fixture that is placed offset on the boring mill table the required dis- tance to give the stroke desired in the finished eccentric Due care is exercised to make sure that the. stud locating the eccentric FIG. 19--UNIQUE: TYPE: OF 'PLANER' 'HQUIPPED® WITH - "TWO : "HOUSINGS--THE PIBCES. SHOWN ON "THE PLATEN ARE' LINK : 'BARS | on the crankshaft. Two ecsenizics can generally be made. solid as it is a simple matter to' 'slip them over the free end of: 'the: shaft.' For two reasons, centrics. for the engine | 'under: discus: sion are installed: over. couplings. CPA eccentric is" a comparatively. large: necessary in this case -which gives a large bearing surface'on the: strap. This causes unnecessary' friction and consequent heat. Again, when eccen- trics are installed over couplifigs, it is impossible to disconnect one. sec- tion of the shaft to eliminate a cylin- der in case of a breakdown at sea. The eccentrics for the MHooven, Owens, Rentschler engines are cast iron. The low-pressure and interme- diate eccentrics are made in two parts, fastened together with steel bolts, while the high-pressure eccentrics 'are. made solid. All ecceutrics are fitted "none -of the ec- eS equ with the boring mill table. : This is quite essential for if it should deviate even a slight de- gree -thei "periphery. of -the finished ec- centric: would - not' stand 'parallel 'with *: 'the. 'bore. - Ais would: result in what ae machinist, Of...a "mariné engineer, " +terms. if "wobbly" eccentric... Such a unit -always. causes trouble and _ is the direct' cause: of many -cases "of undue heating: which. sometimes re- sults in carrying away. -or otherwise disabling the entire valve. gear. Castings for the split eccentrics are first accurately 'planed' to form the joint. _Next the' holes for the bolts that fasten the two. halves' together are drilled, tapped and counterbored. The units thus formed are machined by precisely 'the same méthods - fol- lowed in turning and 'boring: solid ec- "centrics. After eccentrics of both types, that THE MARINE REVIEW in assembly and > fastened. This work. is generally done : om'a shaper, care being taken to Seer: that*theplaned svrfacee'stands square | July, 1919 is solid and split, are bored ang turned, they are drilled and tappeq for the set screws that fasten them to the crankshaft. They are further secured through the medium of keys let into the crankshaft. The eccen- trics are not keyseated, however, untit the engine is assembled because they must be set to give' the proper lead to the valves before the keyseat can be located. The' eccentric straps are made in: two parts each. They are steel cast- ings lined with bearing metal. the joint between the halves. Next, the sections are drilled and reamed to accommodate the bolts that 'fasten them together. A jig is used for this purpose which insures exact 'duplica- tion of parts. After the sections are fastened' together, is poured in place. When it has cooled, it is thoroughly peened in place 'and the strap is ready for boring and turning.. This work is done on the vertical "boring mill; © The "hole is bored and one side faced at one set- ting after ;which "the turned over and the other side faced. Planing Must be Accurate . The "next operation "-consists : of , planing the flat' portion on which ° wthe "E-end "ol the , eccentric: red' ig: - with the sides and parallel wath 'thé bore. . Lhiss and 'eliminates: uftnecessary 'shimming » 'in the assembling Operation. .' These are | 'drilled: anid 'teamed gener- | 'ally "on 'the radial' drill, ' duplication "of parts a Jig is used for 2 résults:- in? a> workiianlike job After this surface 4is:-finished,:-the upper sec- 'tion-of the strapzis drilled and reamed 4 for the" accontmodation. of the bolts that loéate thé? eccentric rod in place. locating the idles. -These bushings have provision for tak- ing. up wear as it' develops and are ; : medium - of -steel bolts with collar. nuts locked The 'eccentric 'rods are steel forg= in&§; straps. The upper ends, rately - bored --to fit» the link pins. held in: place. through. the in -place, The forgings for. the eccentric rods | are first carefully centered and turned | At -this setting, the flat ° portion -at the bottom' of the T-end | fork ; in. the lathe. is also »machined.: Next, the end is finished. on. the shaper. . The holes for the link-pin bushings are bored The : first machining operation consists of © planing the flat surfaces that form ° the bearing metal eccentric is ° and ° 'to insure: ! "finished -all ~ over ~but* not pol-:* ished...Lhese .rodsare..of..the fork. 'type "with ¥Y-ends to fasten to the : ~ eccentric which span. the links, 'combination bushings which are accu- ° are' fitted with - | 2