Table1alsoshowstheplayattheendofatypicalzeroplayhingelatchforside1andside2 perpendicular tothedirectionofrotationwiththehingelockedintheopenposition.Theamountofplayin thisdirectionwilldependontheinteractionoftheclearancebetweenthehinges,andtheclearances betweentheholesandaxlesofthehinges.Theclearancebetweenthehingesislistedasaxialspace betweenthehingesinTable1,aswellastheclearancebetweenthehingeaxlesandthehingeaxle holes.Alloftheseclearances causeplayinthehingewhenthehingeisnotusingthewedgedlatchpin. Anattemptwasmadetomeasuretheplayperpendicular tothedirectionofrotationandthatislistedin Table1also.Therewereproblemsinthisregardbecausewhenattemptingtomeasuretheplayinthe unlockedposition,thehingetendedtomovenotonlyinthedirectionofmeasurement, butalso perpendicular toit.Inaddition,theindicatortendedtoslipoffthetopofthecircularrodwheretheplay wasbeingmeasured.Theresultshowninthetableisfromattemptstomeasuretheplayoneachside. Eachsidewasaddedupproportionally sothattheresultwouldshowtheplayfromoneendtotheother. Inretrospect,onthesinglehinge,itwouldbebettertouseasharperedgewithataperonittomatchthe taperonthelatchpin,andtouseamuchstrongerandhardermaterialwithoutacoatingthatcouldflake off.Onthelatchpin,itwouldbebettertousehardermaterial,andnocoatingandtoreducetolerances. Onthedoublehingeitwouldhavebeenbettertouseclosertolerances. Lessons Learned 1.Hardanodized surfaces andhardlowfriction surfaces willflakeoffifthecontact stressishigh enough. 2.Contact stresscouldhavebeenreduced bymaking thematinghingefacetapered likethehingepin. 3.Frictional coefficients varywidelyanddepend among otherthingsuponthefinishofthemating surfaces, thehumidity, thespeedofloading, theduration ofloading, etc.Sincecoefficients varyso widely,itisnecessary totestthedeviceunderexactly thesameconditions thatyouexpectittoseein service. 4.Usehardsurfaces andunderlying materials onbothbearing parts. 5.Thelatchpinwilltendtobackoutslowlyifalowfrictioncoating andtaperisusedonthepin.One mayconsider locking thepininplacetocounteract this. Advanta,qes oftheZeroPlayHin,qeLatch 1.Zeroornearzeroplayinthedirection ofrotation ofthehinge. 2.Zeroornearzeroplayinthedirection perpendicular tothehingeduetothewedging action. 3.Wedging actionisavailable topre-load thehingeintheopenposition. 4.Thetaperhelpsthelatchtounlatch bytending topushoutthetapered pin. 5.Atwisting actionwithapullingorpushing actiontendstomakethetapered latchbackoutevenmore easilyunderload. AreasofConcern 1.Sliding outofthehingepinespecially whenahardnickel/Teflon coating isusedonthemating surfaces. 2.Working outofthelatchpinwhenthehingepartisoscillated especially inanaxialdirection orrotary axialdirection tothelatchpinwhenusinglowfrictioncoatings. 3.Overloading thecontact areabetween thehingeandthetapered pintobeyond thecontact stress limit,whether itisahardcoating ortheunderlying material. Conclusion Inconclusion, thezeroplayhingelatchwillreduceanyplayinitshingemechanism tovirtually zerowhen itiscarefully designed. Areasofconcern aretheloadsonthehinge,thecontact areaofthetapered latch onthehinge,thecoatings onthematingsurfaces anddesigning themsotheydonotflakeoff,andthe tendency ofthetapered hingepintoworkitselfoutundercontinued loadifitisnotrestrained. Allofthese issuesshouldbesuccessfully addressed inthedesign. Thereremains moreapplications andareasthat canbestudied inregards tothismechanism anditsuseinspace. 117