1secondof.11gberthing acceleration. ThesizeoftheFGBenclosures variesfrom0.481to0.065cubic meters (17to2.29cubicfeet)andinlengthfrom32.5to1388.4cm(12.8to54.7in).Sinceeverykilogram ofmassisexpensive tolaunchandsincetheloadswerelow,theframewasmadewithrelatively small, 1.27-cm (0.5-in) outside diameter x0.953-cm (0.375-in) innerdiameter aluminum tube.Thehingeswere thenmadeassmallasreasonably possible or1.78x2.29x5.84cm(0.7x0.9x2.3in)notincluding the pinsusedtoconnect withthetubing. Enclosure 17'smassis3405g(7.5Ib)andthehingeassembly massis81g(0.178Ib). TheFGBenclosure istransported totheFGBvolume intheZaryamodule oftheISSandunfolded into thevolume whilethepaneldoorisbeingheldopen.Whenpossible, onesideoftheenclosure isclamped totheZaryaframeandthissideandframeservesasastablebasetheastronaut canholdontoandfrom whichtheycanunfoldtherestoftheframe.Then,theopposite sideoftheenclosure isclamped tothe Zaryaframe.Finally, thebackpartoftheFGBenclosure ispushed outintotheemptyvolume andthe hinges lockintoplace.Thespringloadedpaneldoorisallowed toclose.TheFGBenclosure assembly wasbrieflytestedbyanastronaut andhercomments helpedguidethedevelopment oftheenclosure. Thehingeisexpected tobefoldedthenunfolded atleastonceandpossibly moretimesiftheenclosure is removed andstoredorreinstalled. Thehingeisunlatched bypressing inonthelatchpinswiththethumb orforefinger frominsidetheenclosure. Itcanalsobeunlatched fromoutside oftheenclosure bypulling onthebackofthelatchpinwiththelatchpingrip(Figure 2). Thehingeismadeupofadoublehingepiecewithholesfortwohingeaxlesandcorresponding holesfor twohingelatchpins.Hingeaxlesareplacedinthehingeaxleholesinthedoublehingeandheldinplace withretaining rings.Springs areplacedinthehingelatchpinholesbeforethehingelatchpinsareplaced intheholes.Thesinglehingesarefitoverthehingeaxleswhilepressing thehingelatchpinsinthelatch pinholesbycompressing thesprings. Alatchpinscrewthenattaches thetapered latchpintothelatch pingripassembly whichhastwospringpins.Thesespringpinsareusedtoholdthelatchpininthefully retracted position sothatitwillnotinterfere withclosing thehingeassembly. Thelatchpingripassembly isnotnecessary forthezeroplayhingelatchassembly towork,butitmakesiteasiertouse(Figures 1 and2). Theeffectofthetapered hingelatchpinsisthatthesinglehinges onthefoldable tubesarewedged between thebackstop ofthedoublehingeandthetapered wedgeofthelatchpin.Thetapered latchpin willnotallowanyplay.Itwilldothisbyspringing axiallyforward totakeupanygapthatwouldbeopened byplayinthehingeassembly. Thisgapisusuallycaused byclearances duetotolerances. TestsandResults Theobjectofthistestwastoseewhether thetapered latchpinassembly trulyhasremoved alloftheplay fromthemechanism. Table1showstheplayattheendofatypicalzeroplayhingelatchforside1and side2withthehingelatchassembly locked intheopenposition. Figure3shows thesetupofthe measuring equipment. Playwasmeasured intherotational direction. Thisisthedirection thatthehinge wouldnormally rotate.Theplayintheopened, rotational direction isaverylowvalue0.00254 -0.00381 mm(0.0001-0.00015 in)butisnotzero.Thiswascaused bythefactthatintestingitacertainamount of forcewasapplied tothehinge,about30g(1oz),sothatsomereading wouldappear onthedial indicator. Itwasnecessary todothistomakesuretheweightofthehingewasnotpreventing thehinge frommoving freely.Whentheforcewasapplied, itprobably pushed thelatchpinbackward inanaxial direction, causing somelooseness. Thereading wouldbeclosertozeroiflessforcewereused.Afterthe playinthehingewasmeasured, eachsideofthehingewastakenapartandtheaxlesandholeswere measured. Theseresults aregiveninTable1.Usingbasicgeometry andtrigonometry, theplaywas calculated inthehingeassembly assuming nowedging actionofthelatchpins,butjustastraight latch pinfromoneendtotheother.TheseresultsarealsogiveninTable1.Whencomparing theplayinthe hingelatchintheopened andlockedposition withthecalculated playfromtherelatively loosefitofthe hingeaxlesintheholesintherotational direction, onecanconclude thatthetapered hingepinsare preventing alargeamount ofplayinthehingeassembly inarotational direction. Theoretically theplay shouldbezerowiththetapered latchpins. 116