returnedtoroomtemperature ortakentohightemperature, theefficiencywouldbeexactlyasexpected frompreviousruns(noproblemindicated). Iftheunitwasagainreturnedto-54°C(-65°F),thetorque rampefficiencywouldreturntonormal. Afterreviewofallpreviousdata,itwasdecidedthatthelowandhightorqueMOissueswererelated, thoughtheywerepreviouslythoughttobetwoseparateissues.Thisphenomena causedtheprogramto completethemaindriveQualification, andthentroubleshoottheMOissue.Afreshlyassembled and greasedunitwouldrun3mate-demate MOcyclesat-54°Cwithoutissueandshowgoodlowloadinput torqueandhighloadrampefficiency. Repeatedly, onthefourthcycle,theunitwouldbegintoshow steadilyhigherinputtorqueatnoload.Whenthedirectionwasreversed,thelowloadtorquewouldstart lowandsteadilyincreaseinpeaktopeakoscillationandaverage.Eachcyclewouldshowahigher averagestarttorqueuntilthenoisewassustainedacrossthewhole30minutetest(60revsat4rpm=15 minuteseachdirection).Evenmorequizzicalwasthatperiodically, thenoisewouldsuddenlydropoff significantly forsometime,andthenreturn.Inaddition,theforwardrampwouldshowlowerandlower (andmoreerratic)efficiency.Whenevertheunitwasbroughtuptoroomtemporhigher,theunitwould performnominally(bothlowandhighload),suggestingthatnoproblemswerepresentandshowingthere wasnodamagetothewormsurface. Anextendedinvestigation ensued.Severalsuspectareaswerefoundthatmightexplainthereasonfor thetorquelossthroughtheunit.Chiefamongthemweretheseveralsetsofuncagedneedlebearings usedintheMOmechanism. Thesebearingswereselectedasuncagedforloadoravailabilityreasons. Severalgearandbodyborescontainedlightpressfitswiththeseneedlebearings,whichhadaluminum bronzewashersoneitherside.Itwasfoundthatthesebearingshadatendencyto"walk"atcold temperature. OnetheorywasthattheBraycote_601EF,whichhadaviscositytwoordersofmagnitude higherat-54°Cthanat20°C,causedaslightdragonlyatcoldonthelesserloadedendoftheneedle set.Thisdragcausedaskewintheneedlesthatmeanttheywerenolongerparalleltotheaxisofthe shafttheywereridingon.Thisforcedtheresultantloadontheneedlesettoalsobeskewed,settingupa drivingforceinthebearing pressfitdirection. Thecombination ofthisdrivingforce,thenormalbearing rotation, andaloadindirection perpendicular totheshaftaxis,caused thebearing tomovefromits original assembly location. Atroomtempandabove,therewasinsufficient dragfromthegrease to generate aneedleskew,andthusnobearing movement wouldtakeplace.Thetheoryatthetimealso assumed thatintheforward direction, thebearing wouldtendtodrivetheneedlebearing oneway,while reverse direction wouldforceittheopposite way.Also,ifthebearing hadmovedcompletely tooneside duringlowload,itcouldbeenvisioned thathightorqueatlowtempcouldcausethebearing tojam heavily against it'smatingwasher, accounting forthesignificant lossathightorque. Whilemostofthe abovetheories wereprovenasfact,thereweretwopiecesofthepuzzlethatjustdidnotfit. First,therewastheoccasional sudden reduction ofthelargepeaktopeaktorqueoscillations ataverage lowloadinputtorque,whichcouldnotbeexplained bytheneedlebearing shifttheory. Second, the amount oftorqueloss(andthusenergy dissipation) duringthehightorquerampsdidnotcorrespond to thedamage seeninthealuminum bronzewashers, whichtended tobenoticeable butnotsignificant. Itis stillsuspected thatthesefactors, whilenotthemajorplayers, didcontribute totheproblem. Inthefinalanalysis, itwasdeduced thattheonsetofthe"torque blooming" couldbecontrolled bythe amount ofBraycote ®placedintheworminterface. This " ® wassomewhat perplexing astheBraycote was originally applied asaslightcorrosion protection anda"nicetohave". Itwasoriginally anticipated that theWC/Ccouldhaveworked byitselfduetoitslowfrictionnature, butwasnevertestedearlyonwithout greaseapplied. Intheend,itappears theBraycote ®601EF, whichisalightgreaseandisnotcapable of carrying ahighload,wasasignificant parameter inthelubrication equation. TheBraycote ®apparently allowed theslidingmechanism ofthewormdrivetoworkfreelyatlowload,andaddedtothelubrication pictureduringthehighloadramp.ThelackofBraycote _intheinterface duringtorqueblooming reduced theefficiency ofthesystem, butdidnotcausetheWC/Ctofail.Theoccasional reductions intorque noiseweremostlikelycaused byglobsofgreasecoming backintoaction(backintotheslidingpath). Testsshowed thatanabsence ofgrease intheworminterface wouldinitiatethetorquenoisealmost 86