ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
Theweldedsteelbellowsprovidesahermetically sealedwaxchamberandreturnforceaswellas incorporating aninternalhardstop.Advantages ofthisHOPactuatorare: •Shockfreeactuation •Selfresetting •Hermetically sealed •Lowmass(35g)°Lowpower5W@28V °>500cyclecapacity •Highoutputforce155.7N •Integralinternalhardstop Figure3.HOPActuators andTangent Bands CoverDesign Thecover,Figure4,isconstrained torotateaboutafixedpoint,whichisnotatitscenterofmass.The thinshellcoverwasdesigned usingtwolayersofM55JfabricandYLA'sRS-12resinsystem. Two titanium arches werebonded tothecomposite cover,oneateachendusingHysol9394.Thearches provide theprimary interface between thescanmirrorhousing andthecover.Thesearchesalsoserveto stiffenthethinshellstructure. Thearchatoneendofthecoverincludes partofthehingeassembly, while thearchattheopposite endprovides arigidseatforthekick-off springs. HingeDesign Thehingedesignissimple, highlyreliable, anditemploys allpassive components. Thehingeconsists of twoparts,onelocated onthescanmirrorhousing andtheotheronthecover.Thefixedpartofthehinge consists ofabracket mounted onthescanmirrorhousing andcontains thehingepinandcamfollower. Thecamfollower isfabricated usingatitanium sleeve, whichrotates onastainless steelshaft.The stationary hingepinisalsomounted onthisbracket. Allofthehingepartswerecoated withDicronite, (tungsten disulfide, WS2)tominimize frictionandwear.Thisdryfilmlubricant hasacoefficient offriction of0.065invacuum. Therotating bracket, whichisanintegral partofthecover,contains thegrooved cam thathasbeenmachined intothebracket. Thehingepartsareillustrated inFigure5. NASA/CP--2002-211506 66
Hinge PinFigure4.Cover HingeTrack Roller CoverRotation Stop Stationary HingeHalfDicronite (WS2) DryLubrication Hinge Rotation Rotation Stop Hinge Fly-Away HingeHalf Figure5.Hinge Spring Plunger Design AsshowninFigure6,fourspring-loaded plungers, twoperside,wereusedtodeploythecover.Eachset oftwospring-loaded plungers wasdesigned tohaveahighmargin ofsafetyonthespringenergy. The fourspring-loaded plungers mounted inparallel exertamaximum totalforceof103.6Nwhen compressed 15.75mm.Theplungers werefabricated fromtitanium andwerealsovented toreduce air dampening whiletestingatambient conditions. Theplungers raninastainless steelsleevewithgenerous clearances. Thespringwasfullcaptured intheplunger whencompressed toprevent itfrombuckling. The stainless steelsleeves wereusedtoprevent thetitanium plungers fromscratching orgallingthesofter magnesium housing, allowing forhundreds ofdeployments. Additionally, allsurfaces werecoatedwith Dicronite drylubricant. Thesprings andplungers werealsodesigned tohavezeropreload, whichallowed hundreds ofdeployments tobemadewithout having toworryaboutthefasteners pounding outor loosening inthemagnesium housing. CRESorA286fasteners andlocking phosphor bronze Helicals weregenerally usedthroughout, exceptforsometitanium fasteners. NASA/CPm2002-211506 67
DICRONITECOATEDTITANIUMPLUNGER MgHOUSING DICRONITECOATEDSTAINLESSSLEEVE Figure6.Spring-Loaded Plungers Intended Deployment Initially, webelieved thecoverwouldrotate30°aboutthefixedhingepin.Thecoverstopwouldthen comeintocontact withtheinclined rotation stopbuiltintothestationary hinge.Thiswouldconvert someof thecoversrotational energy totranslational energy. Thecenterofmassofthecoverwouldalsomove alonganarccentered atthefixedhingepin30°andthentranslate alongatangent lineasthecover transitioned intocentroidal rotation aboutit'scenterofmass.However, duringlowgravitytesting, this clearlywasnotwhathappened. LowGravity Testing Onerequirement wasthatthecoverwoulddeploywithout hittinghittinganyofthesurrounding solarcells onthespacecraft. Thebestwaytoverifythedesign wastotestitaboard NASA's KC-135 Reduced Gravity Experiment aircraft1.Lowgravitydeployment testswereconducted overtwodaysaboard theKC135.TheHOPactuators wereremoved andahandoperated leveractuator wasinstalled. Therewereno significant issuesregarding HOPsactuating themechanism inzerogravity. However, wewanted tobe abletodeploy thecovertheinstantthecrewindicated minimal gravityconditions werepresent. The typicaltimefortheHOPactuators todeploythecoverwasgreater thantheduration ofthelowgravity conditions. Therefore, toeliminate guessworkanderroneous deployments, thehand-actuated leverwas utilized. Theonlyissueswiththehandactuated leverwerethephysical condition oftheoperators. Asa result,wewereunable toachieve adeployment oneveryparabola thefirstdayastwoofthe experimentalists succumbed tomotionsickness. Inall,57deployments, allsuccessful, werecompleted duringatotalof80parabolas. Included inthe57 deployments, wereseveral deployments withtwospring-loaded plungers de-activated. Thedeployment trajectories wereidentical exceptthevelocities, rotational andtranslational, wereslower. Figure7showsJimBell,fromCornell, deploying thecoverandthelocation ofthevideocamera used. NASA/CP--2002-211506 68
Figure7.CoverDeployment AboardtheKC-135 Equations ofMotion T=lm_ 21 2Vg+Igoo2(1) --rgO)o (2) Io=Ig+mr_(parallel axistheorem) (3) an=/"(_0 2 (4) at=ra (5) T=12(mr2+ie,)= 1z   OoIo(6) NASA/CP_2002-211506 69
NonCentroidal Rotation Thecoverisarigidbodyconstrained torotateaboutafixedhingepoint(O')thatisnotatthecover's centerofmass(g),Figure8.Thecover's centerofmass,g,willmovealonganarcofradius(r)centered atthefixedhinge,O',untilitfliesaway.Atthatinstant, thecoverwilltranslate alongastraight line tangent tothearcandsimultaneously rotateaboutitscenterofmass,g2. Asthelatches open,thecoverbeginstorotateaboutitsfixedhingeaccelerating untilthespringenergy is released andtheplungers reachtheendoftheirtravel.Thecovercontinues torotateataconstant angular velocity untilitseparates andfliesaway.Thus,termscontaining _,Equation 5,reducetozero.  _CENTER OFMASS / -"-.. "_,_t'/TRAJECTORY / \";;  ?---","_ 58-5°'i_,','  _,'__,,,,' ',\....._---',-J-i......... ','.!/'_......_.....Z-z-g(CENq-ER OFMASS) '  i;,.',/,.,---: .q,&P_.,,,,.......  ...._.,._-;.......,.- ..\/..,,._.__,,(. ',.!,./. ',,.rg',., /"_' t\'!,!)o"!_ O" EROFROTATION) Figure8.CoverGeometry man Ry Figure9.HingeFreeBodyDiagram NASA/C P--2002-211506 70
CRISPCoverRelease 120[ I _" 100FI...... 0gAnalysis II,0gTest  lgAnalysis . ;.............  •1gTest .... 80 . o.,t............... aft'  40 ..,,.;"---- mm .... 0 0.14 0,16 0 0.02 0.04 0.06 0.08 0.1 0.12 Time(Seconds) Figure10.CoverAngular Velocity Analysis Measurements madefromtheCADmodel,flighthardware, andvideoswereusedinequations 1-6as follows: m=.325kg rg=.136m k=.0998m (_oo=10.472 rad_s (_.0g=10.76rad_ss =l44m/_s Vg Ig=.O03239kgm 2 Io=.009250kg m2 To=5072kgm2/• /S2 kgm2/ Tf=.5226 /s2measured CADmodel CADmodel Highspeedvideo KC-135video KC-135video Eq.(3) Eq.(3) Eq.(6) Eq.(1) To-- x100% =-3.0% NASA/CP--2002-211506 72
Acomposite picture ofthreeframes ofvideowascreated toshowthecoverinasimilarorientation at threedifferent times,Figure11.Thesecond composite picture, Figure12,showasimilarresult,butwith twoofthefourspringplungers de-activated. Theangleofdeployment remains unchanged, verifying, that itisindependent ofspringenergy. Linearandangular velocities anddeployment anglesweremeasured fromthevideostakenonboardtheKC-135. Theangleofdeployment wasmeasured at60°vs.58.5° calculated. Conservation ofenergy wasalsoverified towithin3%fromthemeasurements andequations ofmotion. Theerrorisbelieved tobeattributable toinaccuracies inmeasurements madefromthevideo frames. Figure11.CoverDeployment Composite NASA/CPm2002-211506 73
Figure12.CoverDeployment 2of4Spring Plungers De-Activated Composite Conclusions andLessons Learned Lowgravitytesting provedtobebeneficial inthatitnotonlydemonstrated thatthecoverisunlikely to damage anysurrounding solarcellsupondeployment, butitalsoallowed ustolearnhowthecover actually deployed inamanner somewhat simpler thanwhatwehadoriginally conceived. Wealsowouldbeinterested toseemoredetailed studies oftheperformance ofWS2dryfilmlubricant as compared toMoS2forbearings andothermechanisms. Although itmaynothavethelowestpossible coefficient offrictionunderidealcircumstances invacuum, oursamples showed ittobevastlysuperior to MoS2duringambient testingconditions theredoesn't appear tobeverymuchWS2information available intheliterature thatwewereabletofind. NASA/CP--2002-211506 74
Inthisembodiment, thenodemustaccomplish manyfunctionsinalimitedvolume.Itmustsynchronize fromtwotofourstrutsthrough90°ofrotation,beverymassefficient,andhouseblanketmanagement mechanisms. Sinceamajorityofthenodesdonotincorporate amotorandareratherdistantfrommotive input,thenodemustnotintroducesignificantretardingforcesduringdeployment. Parasiticmoments wouldleadtolossofkinematictiminggivenstrutflexibilityandcouldleadtobinding.Also,inorderto maintainsomestiffnessduringdeployment, thenodeshouldhaveminimaldeadbandinthesynchronizing mechanism. node(shownherewith motorandgearhead) doublestrutside.....-.-_ singlestrutside /-/..-"._.t,t--._ Figure 2.Baynomenclaturemid-strut hinge Requirements Asthearrayconcept matured, thenoderequirements continued toberefined. Several designs were competed basedontheserequirements. Among theserequirements, several emerged asmostimportant asidefromlowmass,reliability, tolerance tothermal extremes andmanufacturability. 1.Function asapowered orunpowered synchronizer. Theabilitytofunction asasynchronizer isimportant fortworeasons. Inordertokeepmass,costand complexity toaminimum, theabilityofthenodedesign tosynchronize strutsinanunpowered mode affords theabilitytoreduce motorcount.Also,intheeventofamotorloss,theaffected nodemustnot inhibitthedeployment ofthearray.Thisisrealized bylinkingthemotorina'pusher' configuration that doesnotretardstructure motion. NASA/CP--2002-211506 79
2.Maintainnon-zerostiffnessduringdeployment (nodeadband) Adesirablefeatureofthenodewastheabilitytomaintainsomereasonable levelofstiffnessinorderto reducethelikelihoodofbaydistortionandthusthepotentialforbindingduringdeployment. Also,thisis typicallyadesirablecharacteristic inanydeployable structuretofacilitateattitudecontrolschemesand latchout. 3.Possessahighdegreeofapplicability toperipheralnodes. Thenodedesignmustaccommodate fromtwotofourstrutsinordertobeapplicabletotheperipheral nodesaswellasinteriornodes.Inthearrayconfiguration depictedinFigure1,16ofthe21nodesinthe wingarelocatedontheperiphery.Onlyfivenodesarerequiredtosynchronize thefullcomplement of struts. 4.Possesstheabilitytopackageadditionalmechanism forblanketmanagement. Giventhedesiretousethestructuredeployment motorsinordertodeploytheblankets,additional mechanism wouldhavetobepackagedatthepowerednodes.Thisdualuseapproachallowsthemotor counttobeminimized. Theabilitytomeetalloftheserequirements hasadirectadvantageous effectonthereliability,massand complexityofthearraysystembyreducingthenumberofuniquemechanisms. Thegoalindeveloping an arrayofthisnatureistomaintaintheabilitytotilebaysinvariousconfigurations tosuitparticularmission power,stowedanddeployedenvelope,anddeployedfrequency requirements withoutsignificant mechanism redesign. Design Concept Atapedrivemechanism wasthechosen concept basedonitsabilitytomeetalloftheabove requirements inaverysimplemanner. Central tothenodeisacylindrical drumwithanaxisofrotation thatisrotated 90°fromtheaxesofrotation ofeachstrutend.Agivenstrutclevisisfittedwithtwoarc sectors eachlaterally displaced tothetangent ofthedrumasshowninFigure3.Thearcsectors actas portions ofapulleyandaresizedaccording totherequired rotation ofthestrut.Inthiscase,90°ofstrut rotation corresponds tofulldeployment. Apairoftapesrequired foreachstruttobesynchronized is mutually preloaded toeliminate deadband. Asthedrumrotates, onetapeiswoundaround thedrumand isunwound fromonepulleysectorofthestrutclevis.Theopposite tapeisunwound fromthedrumand woundonthepulleysectorontheopposite sideofthestrutclevis. Thisarrangement canbeusedtodrivethedeployment ofoneormorestrutswithasinglemotorthatfits wellinthevolume between thestowed struts.Synchronizing additional strutsisaccomplished inthe samemanner. Figure4illustrates thetapearrangement for4struts.Inthisapplication, thepulley diameter ratiois-1.1andso82.5°ofdrumrotation causes therequired 90°ofstrutrotation. Tapesare generally thincompared tothepulleyradiiandcanthusoverlap withlittleerrorintheangular relationship between thedrumandstrutclevis. NASA/C P--2002-211506 80
Tapes(2x)aregrounded)f_ ateachpulley / i !_''_--Input motortorquePulleysectors grounded tostrut(bothsectors are  grounded onthesame ('levis) Figure3.Synchronization arrangement foronestrut Synchronizer drumwith4sets oftapes/L/7i jJ  _ /_Typical strutclevis _f _ _'_-_'-_=====::=_f--__'_¢./ withintegral pulley    sectors Figure4.Tapearrangement for4struts(onestrutclevisshown) Tapepreload results inazerodeadband mechanism withastiffness largely driventhetapes.This preload alsodriveshingeefficiency duetofrictional lossesateachpinaxis.Anodearrangement withtwo orthogonal strutsresultsintheworst-case bearing load(andtherefore lowestefficiency) onthedrumto nodestructure bore.Abalanced node(twoopposite strutsorfourstrutsinthiscase)withequaltape preload resultsinazerobearing onthedrum. Inthearrangements showninFigures 3and4,bothrotating elements (thedrumandtheclevis)rotateon floating pins(forredundancy) inthenodestructure. Thisarrangement canbeanalyzed forstiffness using methods illustrated inthefollowing section. Synchronization Stiffness Analysis Thenodestructure, showninFigure5illustrates thescaleofthenode.Nodeplateslocatethedrum. Nodelugslocateeachstrutclevis.Thenodehousing isoptimized toprovide stiffness between latched struts. NASA/C P--2002-211506 81
Figure5.Nodehousing Thesynchronization stiffness ofthemechanism canbedescribed bythesensitivity inrelative rotational position ofeachclevisandthedrumwithrespect toastatically balanced setofmoment loads.This parameter isapplicable totheanalysis ofalargerstructure employing themechanism forinvestigating globalstructure shapeandloadsaswellaselasticstability (buckling) andelasticbinding modes. Itisalso usefulindynamic analysis forcalculation ofstructure vibration frequencies anddeployment dynamics. Ifthemechanism drum,housing andclevisareassumed toberigid,mechanism stiffness islargelydueto tapestiffness. Thisassumption isgenerally validsincethetapesarerelatively thinandnarrow duetothe pulleyradiiandthe90°twistrespectively. Afurtherassumption isthatthetapesarepreloaded beyond thestiffness kneeduetothetwist.Figure6showsasimplified stiffness modelofthemechanism where theeighttapesaretheonlyelasticelements. Eachclevishasbeenrotated 90°toallowatwo-dimensional visualization. Eachtapeisrepresented byalinearspringofstiffness k.Staticanalysis ofthemechanism yieldsfiveequilibrium equations, M,=2r_,m2=21%, m3=2rf3,m4=2rF4, (1)rMmI+M2+m3+m4+- j=0 rz Thespringforcesareassumed positive intension andyieldfourspringconstitutive equations, F, < (2) Fivekinematic equations relateelement rotations tospringstretch(smallrotations areassumed), A1=rOl,A2=r02,A3--1"03, A4--t"04,A/--r/Oj. (3) Relations between theapplied moments andtheelement anglesarederived bysubstituting thekinematic andconstitutive equations intotheequilibrium equations, 2kr2=M1 ....-M2 -M3 -M4 - M't (4)-) O,-'i'O O_-'i_Oj 03-':'0_, 04-'_'Oj4UO -r_t(O, +0_+03+04)d _ . 2cl F F F t" F 1" Equation (4)reveals therotational stiffness (M/O) ofanyclevisrelative thedrum(0/=0)is2kr_. Similarly, thestiffness ofthedrumrelative tothefourlimbs(0_--02--03=04=0)is8/,t_.Therelations arealsoapplicable togeneral casesofarbitrarily imposed loadsorangles. However, themechanism has onerigidbodydegree offreedom; itisunder-constrained. Specifying oneoftheelement angles sufficiently constrains theproblem toallowsolution oftheequations (4).Forexample, with0j=0,the remaining element anglesasafunction oftheapplied loadsare, NASA/C P--2002-211506 82
where,02--M2-M103M3-M104-M4-Ml0_:=-M----L 2r2k,=2r2k, 2r2k,2rrdk, (6) M,- rMj-(M 2+M3+M4). (7) Astiffness reduction factorduetothetwistineachtapeissometimes needed inevaluating theabove equations. Thetheoretical stiffness ofastraight tape(notwist)isgivenby, AE k=--, (8) l whereAisthecrosssectional area,EisYoung's modulus andlistheactivetapelength.Introduction ofa twistmodifies thetapeload-path sothatitbecomes curvedtoward theedgesofthetape.Withcertain geometries (generally, widerandthinner tapes)thetwistcanalsocausetapebuckling patterns. Afinite element analysis (nonlinear transient dynamic) wasusedtoinvestigate tapestiffness andbuckling issues. Anillustrative buckling pattern isshowninFigure7.Effective extensional stiffness analysis resultsfora relatively thin(0.025-mm thick)tapeareshowninFigure8.Atlowtensions, atapeshowing buckling patterns exhibits adrastically reduced effective extensional stiffness, butathigherpreloads, thebuckling patterns canberemoved andnearlyfulltapestiffness isachieved. Evenafterbuckling patterns are removed, however, only88%ofthefullstiffness isachieved. Thephysical models builtforthisstudy employed tapedimensions (0.132x2.54mmx135.6mmlong)suchthatbuckling neveroccurred and theeffective extensional stiffness wasnotsignificantly reduced duetothetwist(lessthan2%reduction). Forthesedimensions, theeffective springstiffness ofanindividual tapeis1900N/mm,therotational stiffness ofanyclevis(r=16.5mm)relative thedrumis1034N-m/rad andtherotational stiffness ofthe drum(rj=19.0mm)relative tothefourlimbsis5487N-m/rad. A:F: Ad F_ El A4 Figure6.Mechanism stiffness model NASA/CP--2002-211506 83
Figure 7.Finiteelement model oftapebuckling pattern 0.9 U_ i "0.8 0 --0.7 N0.6 =0.5m =0.4 "0 o 0.3 o.2 w0.12.54x0.0254 mmtape E=206.8GPa,Nu=0.3 Irregularities dueto removal ofbuckling patterns 0 10 20 30 40 50 Stress (MPa) Figure 8.Effective modulus ofthintapewith90°twistandbuckling atlowstress levels NASA/C P--2002-211506 84
Thesemethodsdidnotpossessallthecharacteristics requiredforareliable,simple,andcost-effective solutionandafterfurthersearching,laserweldingprovedtobetheperfectsolutionforthisapplication. Unlikeconventional welding,laserweldingproducesaverysmallheataffectedzone,isextremely controllable andrepeatable, allowsforprecisefixturing,andturnedouttobeextremelycosteffective. Also,usingthisprocessitwaspossibletoweldtheElgiloy®tapestoalmostanycommonstainlesssteel except303or316.Tapeanchorswereweldedtoeachendofthetapeandtestedintension.Thewelded tapeassemblystrengthprovedtobeveryrepeatable atapproximately 70%oftheyieldstrengthofthe tape.Figure10showsatypicallaserweldedtapeanchor. Tapepreloadandlengthadjustment wasaccomplished viaanadjustment screwlocatedonthestrut clevis.Accessandtune-ability provedtobeveryeasy.Accurately measuringthepreloadinthetapes provedtobedifficultandforexpediency wasdonebyfeel.Duringthefirstiteration,tapepreloadandstrut angularpositioning wasaccomplished bylockingthedrumtothenodehousingusingapinwhilekeeping thestrutsinalatchedandthereforeknownposition.Thepinwasabletospinfreelyinthedrumand housing.Tapeswerethenpreloadedoneclevisatatime.Bypreloadingopposingtapesapairatatime, equalpreloadcouldbeverifiedbythelockingpin'sabilitytospin.Onetapewouldbepreloadeduntilthe desiredvaluewasreached,thentheopposingtapewouldbeloadeduntilthepinwasfreetospinagain. Thisprocedurewasthenrepeatedfortheadjacentstrutinthenode.Thismethodproducesa progressively higherpreloadineachsubsequent strutduetotheaddedstiffnessofthepreloadedtape setsofpriorstruts.Analternativetothisapproachmightbetopreloadallstruttapesofthesamefunction (forexamplethosethatareusedtomovethestrutsinthesamedirection)atonceagainstthelockingpin thentheremainingtapesintheopposingdirectionwouldbepreloaded. Secondgeneration hardwaremayinvolvebondingastraingaugeoneachtapeorpossiblyaremovable extensometer andpreloadingtheentirenodeonthebenchpriortointegrationintothestructure.Each tapeandstraingaugeassemblywouldbecalibratedpriortoinstallation. Straingaugeplacement(ifused) wouldlikelybeonaportionofthetaperunningoverthedrumorclevissegmentinordertoeliminatethe torsionalstrainsduetotapetwist.Strainduetobendingoverthepulleywouldhavetobeconsidered. All tapeswouldbetakenfromzero-loadtotherequiredpreloadatthattime.Thenodewouldthenbecycled inordertoexercisethetapesovertheentirerangeofmotionandthencheckedagain.Theabilityto exerciseanodeisimportanttoensureuniformstrainalongtheentiretape.Exercisinganodewhile integratedwithinapotentiallyverylargearraywouldrequirecyclingtheentirearrayandthereforebetime consuming, riskyandcouldpotentiallydegradesystemreliability. Figure 10.Laser-welded tapeanchor NASA/CP--2002-211506 86
Design Progress Hardware hasbeenmanufactured andintegrated intoademonstration singlebayofthearraystructure measuring approximately 2.5x5m(bothsidesofonenodeisshowninFigure11).Thebayhasbeen successfully cycledupwards of50timeswithverypromising results. Second generation nodehardware designisunderway andprogress hasbeenmadeincorporating additional functionality. Thetapedrive portion ofthemechanism hasremained essentially unchanged fromthefirstgeneration hardware. The abilitytopackage additional mechanism canbeasignificant driverincompeting designs thatmustbe implemented inlimitedvolume. Thetopandbottom nodeplatesaswellasthevolume withinthedrum wereusedtomountorhouseadditional mechanism. Thebottomnodeplate,around whichthestrutsare stowed, provided theinterface foreitheramotororspring. Latches andhardstops weremounted tothe uppernodeplate.Alltheblanket management mechanism ishoused completely withinamodified drum. Thesamemotors usedtodeploythestructure areusedtodeploytheblankets. Byreversing thedirection ofthemotor,themotorshaftdisengages thedrumandengages amulti-track cabletake-up reelthat deploys theblankets intwobays.Sincethedrumonlyrotates approximately 90°,windows located inthe wallofthedrumprovide radialaccess fortheblanket cables. Clutchdesignandcablemanagement are beyond thescopeofthispaper,butFigure12showsthesecond-generation nodewiththeadditional planned drummechanism installed. Figure12.Drumwithblanket mechanism anddrumintegrated intonode Conclusions Thetape-driven nodemetthedesignrequirements andfitverywellwithinthelimiteddesignspace.The mechanism proved tobeveryefficient bothintermsofenergy transfer andminimal mass.Theuseof tapesandpulleysegments allowed simpleanalysis methods. Thehardware function isvisually clearand sofacilitates inspection andtesting. Accurate determination oftapepreload canbedifficult although itmaybeaccomplished usingstrain gauges permanently fixedorextensometers temporarily fixedtoeachtape.Othermethods mayprove morepractical. Tapetermination usinglaserwelding proved tobeverystrong, reliable andeconomical. Tapeanchors canberoutedandsizedtoadapttotherequirements andvolume limitations ofvarious embodiments. Tapedrivessuchasthispossess wideapplicability duetoscalability andefficiency. Rollerorsleeve bearings canbeincorporated tofurther increase overall efficiency. Nodearrangements withalternate numbers ofstruts, non-orthogonal axes,and/or different rotation angles arepossible. Theabove discussion ismeanttoprovide thereader withsomedesign andmanufacturing lessons learned in implementing suchamechanism withreal-world designrequirements. NASA/CP--2002-211506 88