February 1999 - American Bonanza Society

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CurrentsBI' LEWGAGEReconditioned crankcasesWhen we are up for overhaul witb an·'E" engine, what is involved regardingthe crankcase before assembly of the enginebegins?After the eng in e is disassembled,the various parts shouldhave all the oi l and sludge removedby using solvent, compressedair, hot water wash orother methods so accurate measurementsand verification offitscan be made. If the case halvesshow evidence of frell ing, thecase must be reconditioned.Fretting is the movement ofone case half against the otherduring engine operation whichwears away the metal betweenthe two surfaces. This wear usuallyshows only, or shows worst,at the main bearing bosses, butfrelling might also occur otherplaces on the case-mating surfaces.A fre ll ed surface looks asthough it had been bead-blasted withmedium grit bead blast material and severalthousandths of an inch of surfacemay have worn away. This loss of materialcauses the main bearing through boltsto lose the proper torque and pre-load.openi ng the door to accelerated furtherfretting, "spinning" of the main bearinginserts, oil leaks around the through boltsand possible engine failure-none ofwhich is good. The first indication ofcrankcase fretting on an operating "E"engine is usually oi l leaks around thethrough bolts.When the shop doing the reconditioningwork returns the crankcase, it shouldbe assembled by applying a light coat ofPrussian Blue to all mating surfaces ofone case half and then joined using thethrough bolts and the old nuts torqued tofu ll torque (490-510 inch pounds or 41to 43 foot pounds). The threads and nutbases should be lubricated with motor oil.The case flange or edge bolts do not needto be installed, only the bearing throughbolts. Suitable flat washers must be usedto equal the cylinder base thickness forthis assembly procedure.A measurement of all bores affected bythe surfacing of the case halves and a fewothers must be made. They are: (I) mainbearing saddles to be 2.5625 - 2.5635; andCrankcase bearing boss showing column supports. Thestructure acts as a compressively loaded column. Pencilindicates fretting area.(2) all other fits per table of limits.The amount which has been cut fromthe two case halves can be detemlinedby measuring the bo s on the nose of theengine that aligns either the Beech propmounting plate or the Hartzell OTU.When the case is machined flat, this bossgoes out of round by the amount cut fromthe case halves.Example: The top-to-bottom measurementof this boss is measured at 4.250while the left to right is 4.238, a .012 outof-roundcondition. Therefore, the casehalves have each been cut .006 or onecut .005 and the other .007, etc.This out-of-round condition does notaffect the performance of the Beech orHartzell propeller mechanisms (althoughit doesn't help either) because of built in"slop" allowances in both systems.Once the various measurements aretaken and recorded, the case is split apartand the imprint the Prussian Blue has leftis checked. The very cri tical areas are themain bearing boss pads. The case edgesare also critical, but if there is a slightlylighter "print" or a sma ll skip area, it willbe checked on the next case assemblywhichis to check the main bearings TDwhen installed.Install the bearing halves in thecrankcaseand again fasten the case halves togetherwith the through bolts andold nuts torqued to 41-43 footpounds. Measure the bearing TD(each 60 degrees around the bearing)for the expected bearingclearance. Also, if need be, installthe case edge bolts in the area ofquestion if a solid "blue" printwas not obtained during the firstassembly. Only tighten thesebolts to a snug torque. This slightcoaxing of the case flanges intocontact with each other will ensurethe proper clamping effecttakes place when the full torqueis applied.The little "tangs" or ears onthe main and rod bearing insertsare not what hold the bearingsrigidly in place in the crankcaseor rod end. The bearing relies onPage 5585 ABS February 1999
a closely controlled amount of "crush."This produces the same effect achievedin a one-piece bearing bushing pressedinto a solid bore.The ears or tangs on thebearing halves are used onlyas locating lugs during engineassembly. If the propercrush or interference fit isnot achieved, the bearingmay have too little clearancewith the crankshaft journal:the bearing may "spin" in thesaddle; oil pressure may belost out the space betweenthe backside of the bearingand the saddle; insufficientcontact between the bearingand crankcase results, whichdegrades bearing heat transferor excess bearing clearanceresults, which lowersoil pressure.The main and thrust bearinginsert halves should be.093 thick for standard bearingsand .098 for crankshaftswhich have been ground undersize by .010.After all measurementshave been recorded andcompared with the table oflimits, the engine "powersection" (crankcase and cylinders)may be assembledusing new through bolt nuts.Be sure that no paint is underthe cylinder stud andthrough bolt nuts and thethreads and nut contact surfacesare lubricated with 010-tor oi I.Any condition that mightcontribute to in sufficientpre-load of the "compressivelyloaded column" of thethrough bolts will lead tofuture fretting of the crankcase.An excellent manual,which offers a comprehensivedescription of this andmany other considerationsregarding Continental and Lycomingopposedaircraft engines. is the Sky RanchEngineering Manllal (800-433-3564). Ithi nk il is the best buy around for yourDescript ionGEAR BACKLASHCamshaft Gear and Accessory Drive Gear . ........... Bacdash:Cam5hah Gear and Magneto Drive Gear . ............ Backlash:Camshaft Gear Unternall and Generator Drive Gear . .... eacldash:Camshaft Gear ~nd Accessory Drive Idler Gear . .... , ... 8acit ta sh:Camshaft Gear and Right Side Accessory Drive Gear . . . .. Ba:::!dash:Accessory Drive Idler And Left Side AccessoryIScavenqe) Pu mp Orive Gear ............ . , .... Back.lash :Oil Pressure Pump Impellers . .. . . ... ........ . .... Badtlash:LefT MAGNETOSTARTER DRIVE CEARrP~// - '\,\".I.-.-+-;+!;i -. : 1-jI-. -h-'~'; IjJreference library for about $20. This is aplain language publication that can makeclear, to just about anyone, some of themysteries of what's happening and why inServicelim itNewMin..0 14 .006.0 1B .010.019 .010.Q15 .007.0 15 ,007.0 16 .OOB,017 .009PartsMax..0 10,014.014.011.0 11.012.013CRANKSHAFTI' 1 " ~ACCESSDRY DRIVE GEAR·-H\,{( /T\--:;:;'~,!. ) je . ~ ~~GI~! ~E~GRNETO~--'......~ ~ • / //I ~If /"''\. ~ if r':\1 \)DRIVE GEAR....{ ~ \ ~-- ~-=--..... -... "",.,\! I ) Ij~"'''""' '" ,". i\.~ / - , - 'jDRIVEN IMPEllER - ~\ '\ -~TACHOM~TER i" ""~f' @,. ~. CAMSHAFT EXTERNjLDRIVE SHAFT f II ,\,:;' GEARINTEGRAL /,' ,( . -: CAMSHAFT INTERNAL;1 " 1(/1~ -\ \ . .GEARPRESSURE OIL PUMP \i \ \ ' ~7- '--- - rr' .- INTEGRALORIVING IMPEllER \\ \ . .~ + /1 i /GENERATOR~\" . ''0\r')i i /' //I Y 'DRIVE GEAR \,'"'&¥;/.I ,/1'"".~~. ~;// 'o./ J RIGHT Sl OE ACCESSORY~..,.. '- _;~._ -;:.#'f < ~ DRIVE SHAFTGEAR\1.\ ) )!~_~"I \ : ,~\ .SCAVENGE OIL PUMP ;~~-(;;--. (--" '\DRIVEN lMPElLER------"';/r-, JSCAVENGE OIL PUMP __"t>--\ ! ,:,\\... ~.J-- , . i) ",--= .::7~,,\, )// ~~SCAVENGE OIL PUMP-~ ,.7' . ACCESSORY DRIVE ID LE R GEARAND LEFT SIDE ACCESSORYORIVE SHAFTGEARDRIVING IMPElLER (! i C I\\ /IE GEAR TRAIN DIAGRAM.ABS February 1999Page 5586
Page 2 and 3: TCM1s Factory Installations,built b
Page 4 and 5: BONANZA OF THE MONTHCover: Wi ll ia
Page 6 and 7: Bonanza provides wayfor medical rel
Page 8 and 9: Bonanza pre-purchaseinspectionDavid
Page 10 and 11: 835 electric boost pumpjoe SalernoP
Page 12 and 13: A: AirTex at 215-295-4115 has legal
Page 14 and 15: ITSDEAD,JIM'--../---.-.Tips on anAV
Page 16 and 17: A CASE STUDYThe cost of converti ng
Page 18 and 19: Regarding the use of GAMljectorscan
Page 20 and 21: 1999 CD-ROM is now availableOrder y
Page 22 and 23: Re: Braly's article on leaningAfter
Page 24 and 25: Slipped the surly bondsAs we \rere
Page 26 and 27: AvionicsBY JIM HUGHESArchangelI wan
Page 28 and 29: Shop TalkBY LYNN JENKINSRaytheon (B
Page 32 and 33: these engines.After an overhauled "
Page 34 and 35: FLIGHT TO ARGENTINAMADELEINE DUPONT
Page 36 and 37: The ABS Board of Directors is happy
Page 38: C I dAMERICAN BONANZA SOCIETY HEADQ

February 1999 - American Bonanza Society

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