position, the dial will be upside down, making itnecessary to use a mirror and flashlight to obtain areading.NOTE: Once you have placed the indicator inposition for the first deflection reading, do not touch thegauge until you have taken and recorded all fourreadings.Deflection readings are also used to determinecorrect alignment between the engine and the generatoror between the engine and the coupling. However, whendetermining alignment, you should take a set ofdeflection readings at the crank nearest the generator orthe coupling. In aligning an engine and generator, youmay need to install new chocks between the generatorand its base to bring the deflection within the allowablevalue. You may also need to shift the generatorhorizontally to obtain proper alignment. To align anengine and a coupling, first, correctly align the couplingwith the drive shaft; then, properly align the engine tothe coupling, rather than aligning the coupling to theengine.BEARING TROUBLESBearings become a continual source of troubleunless personnel entrusted with operating the enginefollow the recommended operation and maintenanceprocedures exactly.Severe bearing failures are indicated during engineoperation by a pounding noise or by the presence ofsmoke in the vicinity of the crankcase. Impendingfailures may sometimes be identified by a rise in thelubricating oil temperature or a lowering of thelubricating oil pressure. Impending bearing failure maybe detected during periodic maintenance checks orduring engine overhauls by inspection of the bearingshells and backs for pits, grooves, scratches, or evidenceof corrosion.The indication of an impending failure does notnecessarily mean that the bearing has completed itsuseful life. Journal bearings may perform satisfactorilywith as much as 10 percent of the load-carrying arearemoved by fatigue failure. Other minor casualties maybe repaired so that a bearing will give additional hoursof satisfactory service.Bearings should not be rejected or discarded forminor pits or minute scratches; however, areasindicating metallic contact between the bearing surfaceand the journal do mean replacement is needed. Use abearing scraping tool to smooth minute pits and raisedFigure 3-30.—Using a torque wrench to tighten a main bearing.surfaces. After working on bearings, make every effortto ensure that the bearing surfaces are clean. This alsoapplies to the bearing back and the connecting rodjournal Place a film of clean lubricating oil on thejournals and the bearing surfaces before you reinstallthem.INSTALLING JOURNAL BEARINGSAlways check the markings of the lower and upperbearing halves so you install them correctly. Manybearings are interchangeable when new, but once theyhave become worn to tit a particular journal they mustbe reinstalled on that particular journal. You must markor stamp each bearing half with its location (cylindernumber) and the bearing position (upper or lower) toprevent incorrect installation.You must also pull the connecting rod bearing capnuts down evenly on the connecting rod bolts to preventpossible distortion of the lower bearing cap andconsequent damage to the bearing shells, cap, and bolts.Use a torque wrench (fig. 3-30) to measure the torqueapplied to each bolt and nut assembly. Apply the sametorque to each bolt. If a manufacturer recommends theuse of a torque wrench, the specified torque will be listedin the manufacturer’s technical manual.Another method for pulling down the nuts evenly isto stretch each bolt an equal amount and measure thedistance from end to end of the bolt before and aftertightening. Figure 3-31 shows the type of gauge used,3-20
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