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5Po11-news 发布时间: 2020-07-05 12:48:04

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CHAPTERXVI.MACHINERYOFAPPLICATION.

Water-wheels,nexttosteam-engines,arethemostcommonmotiveagents.Forcenturieswater-wheelsremainedwithoutmuchimprovementorchangedowntotheperiodofturbinewheels,whenitwasdiscoveredthatinsteadofbeingaverysimplematter,thescienceofhydraulicsandwater-wheelsinvolvedsomeveryintricateconditions,givingrisetomanyproblemsofscientificinterest,thatintheendhaveproducedtheclassknownasturbinewheels.

Inordertorenderwhatissaidofshopprocessesmoreeasilyunderstood,itwillbenecessarytochangetheorderinwhichtheyhavebeennamed.Designing,andmanymattersconnectedwiththeoperationofmachines,willbemoreeasilylearnedandunderstoodafterhavinggonethroughwithwhatmaybecalledtheconstructiveoperations,suchasinvolvemanualskill.

Suchtoolsconsistofacombinationofcuttingedges,allofwhichmaybesaidtodependoneachone;becauseifonebreaks,thenextinorderwillhaveadoubledutytoperform,andwillsoonfollow—areversaloftheoldadage,that'unionisstrength,'[142]ifbystrengthismeantendurance.

Millingtoolslargeenoughtoadmitofdetachablecuttersbeingemployed,arenotsoexpensivetomaintainassolidtools.Edgemovementcansometimesbemultipliedinthisway,soastogreatlyexceedwhatasingletoolwillperform.

Thefeedmotioninslottingmachines,becauseofthetoolsbeingheldrigidly,hastooperatedifferentlyfromthatofplaningmachines.Thecross-feedofaplaningmachinemayactduringthereturnstroke,butinslottingmachines,thefeedmovementshouldtakeplaceattheendoftheup-stroke,orafterthetoolsareclearofthematerial;somuchofthestrokeasismadeduringthefeedingactionisthereforelost;andbecauseofthis,mechanismforoperatingthefeedusuallyhasaquickabruptactionsoastosaveuselessmovementofthecutterbar.

Examiningmachinesmadebythebestdesigners,itwillbefoundthattheirdimensionsbearbutlittleifanyreferencetocalculatedstrains,especiallyinmachinesinvolvingrapidmotion.Accidentsdestroyconstants,andadraughtsmanordesignerwhodoesnotcombinespecialandexperimentalknowledgewithwhathemaylearnfromgeneralsources,willfindhisservicesto[89]beofbutlittlevalueinactualpractice.

Anapprenticemustguardagainstthetoocommonimpressionthattheengine,cylinder,piston,valves,andsoon,arethemainpartsofsteammachinery,andthattheboilerandfurnaceareonlyauxiliaries.Theboileris,infact,thebaseofthewhole,thatpartwherethepowerisgenerated,theenginebeingmerelyanagentfortransmittingpowerfromtheboilertoworkthatisperformed.Thispropositionwould,ofcourse,bereachedbyanyoneinreasoningaboutthematterandfollowingittoaconclusion,butthefactshouldbefixedinthemindatthebeginning.

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网友评论

  • 雨花郡主nYzAL

     Power-hammersoperatedbycrankmotion,adaptedtothelighterkindsofwork,arenowcommonlymetwithintheforging-shopsofengineeringestablishments.Theyareusuallyofverysimpleconstruction,andIwillmentiononlytwopointsinregardtosuchhammers,whichmightbeoverlookedbyanapprenticeinexaminingthem.

  • 雪灵芝xxu3D

  • 如萱紫儿sjl6Y

    Asremarkedinthecaseofothermachinestreatedof,thereisnouseofdescribingthemechanismoftrip-hammers;itispresumedthateveryengineerapprenticehasseentrip-hammers,orcandoso;andtheplanhereistodealespeciallywithwhathecannotsee,andwouldnotbelikelytolearnbycasualobservation.

  • 但法国hc5Bx

    1.Themosteconomicalandeffectualmechanismforhandlingisthatwhichplacestheamountofforceandrateofmovementcontinuallyunderthecontrolofanoperator.

     

  • 大笨蛋mRBHE

    v

  • 扒皮成7R5RY

     

  • 草莓果AeboK

    (1.)Whatchangehastakenplaceinthemeaningofthename"invention"asappliedtomachineimprovement?—(2.)Whatshouldprecedeanattempttoinventorimprovemachinery?—(3.)InwhatsenseshouldthenameinventionbeappliedtotheworksofsuchmenasBentham,Bodmer,orStephenson?

     Invention,asappliedtomechanicalimprovements,shouldnotmeanchancediscovery.Suchameaningisoften,ifnotgenerally,attachedtotheterminvention,yetitmustbeseenthatresultsattainedbyasystematiccourseofreasoningorexperimentingcanhavenothingtodowithchanceorevendiscovery.Suchresultspartakemoreofthenatureofdemonstrations,anamepeculiarlysuitableforsuchinventionsasaretheresultofmethodicalpurpose.

  • 绿卡纸u87wQ

     Agreatshareoftheallegedimprovementsinmachinery,wheninvestigatedwillbefoundtoconsistinnothingmorethanthecombinationofseveralfunctionsinonemachine,thenoveltyoftheirarrangementleadingtoanimpressionofutilityandincreasedeffect.

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