CA J ZeroPlayHingeLatch MikeCabiran Abstract Azeroplayhingelatchwasdesigned byusingatapered latching pintostopthehingefromreturning fromitsunfolded position. Thetapered latchpinwouldholdthehingewithout anyplaybywedging it against abackstop. Anyplaycaused bytolerances istakenupbyadditional axialmovement and therefore wedging bythespring-loaded tapered latching pin.Thisparticular ideashould bewidely useable inspacestructures sincemanystiff,long,andlightstructures areusedinspaceasoftenitis necessary tokeepplayataminimum. Somereasons forthiswouldbetheneedtoholdacamera steady tofocus,toholdstowage inprecise volumes, etc. Introduction Thispaperpresents adescription ofthedesign, manufacture, testing, andproblems ofazeroplaylatch design usingatapered latchpin.Thezeroplayhingelatchwasdesigned toprovide asmall,stiff, minimum playhingeandlatcharrangement forfolding, thenunfolding atubular frame,asshowninFigure 1,whichwouldsupport aclothcoverasshowninFigure4.Figure4showstheframeandclothcoverbut notthecordthatgoesthrough theholesandaround theframeandtiesattheend.Thisframeandcloth coverwereoriginally designed tobefoldedintoacompact shape,transported totheInternational Space Station (ISS),thenthrough several hatches totheZaryamodule, (formerly knownastheFGBmodule), unfolded, thenclamped inposition intheZaryamodule whileon-orbit asshown inFigure5.Figure5 showsFGBenclosure 17clamped totheZaryaframe. Somedimensions areshown. AlsotheCrew Transfer Bag(CTB)isshownintheframe.ThisframewiththeclothcoverwascalledtheFGBenclosure. TheFGBenclosures weretoolargetofitthrough theentryhatches ofthemodules oftheISSattheirfull volume andtherefore hadtobefoldedtofitthrough whenon-orbit. Whentheywereunfolded, theyhadto beprecisely sizedandstiffsinceanyextraplaywouldresultinviolating theimposed boundaries of1cm (0.394in)outside ofthedefined volume. Thiswastoprevent interference bythestowed itemswith delicate avionics andclearances usedforventilation. Otherrequirements werethattheFGBenclosure hadtobeabletobeassembled intoalargerspacethanitcouldfitthrough meaning thatithadtoeasily expand intoplace.Ithadtobeabletobeeasilyclamped intoplaceinzerogeesandwithout anytools. SeeFigure5.Also,therecouldbenopinchpointsinthehingemechanism. Thehingeneeded tobe aboutasstiffasthetubing, however, muchofthestiffness oftheenclosure assembly wasprovided by thecrossbracing fromcornertocorneroftheassembly withNomexwebbing asshowninFigure4.Two mainfeatures oftheenclosure thenwasthatithadtobefoldable andcompact, andonceunfolded, ithad tobestiff.Oneoftheproblems withmaking complex mechanisms stiffistheaccumulation ofclearances duetotolerances frommanufacturing. Thisproblem wassolvedbyusingatapered latchpin,whichby axialmovement couldholdthehingeopenandtakeupanyaccumulation ofclearances. Description ofaZeroPlayHingeLatch TheactualloadsontheFGBEnclosure wererelatively lowsincetheywerecaused bystowed goodsina micro-gravity environment. Themaximum loadtheframewouldencounter fromacceleration wouldbe.11 g'sfromaberthing maneuver foraduration of1second. Duringthismaneuver theframewouldneedto restrain themassofitscontents, i.e.,CTBs,towithin1cm.TheCTBshaveamassdensity of400.5 kg/m3orabout22.7kgfor1fullsizeCTB.TheFGBvolumes arenumbered from1to22andthevolumes weweredesigning for,1-4and14and17werecalculated todeflectatmost0.292cm(0.115in)fromthe Lockheed MartinSpaceOperations, Houston, TX Proceedings ofthe35thAerospace Mechanisms Symposium, AmesResearch Center,May9-11,2001 115