冯剑坚:追梦三尺台 驰骋万里路

XhVUz-news 发布时间: 2020-07-11 12:47:38

“买体育彩票的app【注册大礼】”Thefeedadjustmentofthetoolbeingintermittentandtheamountofcuttingcontinuallyvarying,thismovementshouldbeperformedbyhand,soastobecontrolledatwillbythesenseoffeeling.Thesameruleappliestotheadjustmentoftherackforspacing;beingintermittentandirregularastotime,thismovementshouldalsobeperformedbyhand.Thespeedofthecuttingmovementisknownfromordinarypracticetobefromsixteenfeettotwentyfeetaminute,andabelttwoandahalfincheswidemustmovetwohundredfeetaminutetopropelanordinarymetalcuttingtool,sothatthecrankmovementorcuttermovementmustbeincreasedbygearinguntilaproperspeedofthebeltisreached;fromthisthespeedofintermediatemoverswillbefound.

Toattemptageneralisationoftheoperationsofthefittingshopinthismannermaynotseemaverypracticalmeansofunderstandingthem,yettheapplicationwillbebetterunderstoodaswegofartheron.CHAPTERXXII.PATTERN-MAKINGANDCASTING.

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

Asetoflathetoolsshouldconsistofallthatarerequiredforeveryvarietyofworkperformed,sothatnotimewillbelostbywaitingtopreparetoolsaftertheyarewanted.Anordinaryenginelathe,operatingoncommonworknotexceeding[126]twentyinchesofdiameter,willrequirefromtwenty-fivetothirty-fivetools,whichwillserveforeverypurposeiftheyarekeptinorderandinplace.Aworkmanmaygetalongwithtentoolsorevenless,butnottohisownsatisfaction,norinaspeedyway.Eachtoolshouldbeproperlytemperedandground,readyforuse'whenputaway;'ifatoolisbroken,itshouldatonceberepaired,nomatterwhenitislikelytobeagainused.Aworkmanwhohasprideinhistoolswillalwaysbesuppliedwithasmanyasherequires,becauseittakesnocomputationtoprovethatfiftypoundsofextracaststeeltools,asaninvestment,isbutasmallmattercomparedtothegaininmanipulationbyhavingthemathand.

Powerderivedfromwaterbymeansofwheelsisduetothegravityofthewaterindescendingfromahighertoalowerlevel;butthequestionarises,Whathasheattodowiththis?Ifheatisthesourceofpower,andpoweraproductofheat,theremustbeaconnectionsomewherebetweenheatandthedescentofthewater.Water,indescendingfromoneleveltoanother,cangiveoutnomorepowerthanwasconsumedinraisingittothehigherlevel,andthispoweremployedtoraisethewaterisfoundtobeheat.Waterisevaporatedbyheatofthesun,expandeduntilitislighterthantheatmosphere,risesthroughtheair,andbycondensationfallsintheformofrainovertheearth'ssurface;thendrainsintotheoceanthroughstreamsandrivers,toagainresumeitsroundbyanothercourseofevaporation,givingoutinitsdescentpowerthatweturntousefulaccountbymeansofwater-wheels.Thisprincipleofevaporationiscontinuallygoingon;thefallofrainislikewisequiteconstant,sothatstreamsaremaintainedwithinasufficientregularitytobeavailableforoperatingmachinery.Thebookhasbeenpreparedwithafullknowledgeofthefact,thatwhatanapprenticemaylearn,aswellasthetimethatisconsumedinlearning,arebothmeasuredbythepersonalinterestfeltinthesubjectstudied,andthatsuchapersonalinterestonthepartofanapprenticeisessentialtopermanentsuccessasanengineer.Ageneraldrynessandwantofinterestmustinthis,asinallcases,beacharacteristicofanywritingdevotedtomechanicalsubjects:someofthesectionswillbeopentothischarge,nodoubt,especiallyinthefirstpartofthebook;butitistrustedthatthegoodsenseofthereaderwillpreventhimfrompassinghurriedlyoverthefirstpart,toseewhatissaid,attheend,ofcasting,forging,andfitting,andwillcausehimtoreaditasitcomes,whichwillintheendbebestforthereader,andcertainlybutfairtothewriter.

Inshadingdrawings,becarefulnottousetoodeeptints,andtoputtheshadesintherightplace.Manywillcontend,andnotwithoutgoodreasons,thatworkingdrawingsrequirenoshading;yetitwilldonoharmtolearnhowandwheretheycanbeshaded:itisbettertoomittheshadingfromchoicethanfromnecessity.Sectionsmust,ofcourse,beshaded—notwithlines,althoughIfeartoattacksooldacustom,yetitiscertainlyatediousanduselessone:sectionswithlightinkshadingofdifferentcolours,toindicatethekindofmaterial,areeasiertomake,andlookmuchbetter.Bythejudiciousarrangementofadrawing,alargeshareofitmaybeinsections,whichinalmosteverycasearethebestviewstoworkby.Thepropercolouringofsectionsgivesagoodappearancetoadrawing,andconveysanideaofanorganisedmachine,or,tousetheshopterm,"standsoutfromthepaper."Inshadingsections,leaveamarginofwhitebetweenthetintsandthelinesontheupperandleft-handsidesofthesection:thisbreakstheconnectionorsameness,andtheeffectisstriking;itseparatestheparts,[85]andaddsgreatlytotheclearnessandgeneralappearanceofadrawing.

Apendulumvibratinginuniformtimeregardlessofdistance,butalwaysasitslength,ifarrangedtoperformonevibrationinagiventime,gaveaconstantmeasureoflength.Thuslinealmeasurecomesfromtime;cubicorsolidmeasuresfromlinealmeasure,andstandardsofweightfromthesamesource;becausewhenacertainquantityofasubstanceofanykindcouldbedeterminedbylinealmeasurement,andthisquantitywasweighed,astandardofweightwouldbereached,providedtherewassomesubstancesufficientlyuniform,towhichreferencecouldbemadeindifferentcountries.Suchasubstanceisseaorpurewater;weighedinvacuo,orwiththeairatanassumeddensity,watergivesaresultconstantenoughforastandardof[147]weight.

Thegaugingsystemhasbeennolittleretardedbyaselfishandmistakenopinionthatanengineeringestablishmentmaymaintainpeculiarstandardsofitsown;infact,relicsofthisspiritareyettobemetwithinoldmachines,wherethepitchofscrew-threadshasbeenmadetofractionalpartsofaninch,sothatengineers,otherthantheoriginalmakers,couldnotwellperformrepairing,orreplacebrokenparts.Aplaningmachinewitharunningplatenoccupiesnearlytwiceasmuchfloorspace,andrequiresaframeatleastone-thirdlongerthaniftheplatenwerefixedandthetoolsperformedthecuttingmovement.Theweightwhichhastobetraversed,includingthecarriage,willinnearlyallcasesexceedwhatitwouldbewithatoolmovement;sothattheremustexistsomeverystrongreasonsinfavourofamovingplaten,whichIwillnowattempttoexplain,oratleastpointoutsomeofthemoreprominentcauseswhichhaveledtothecommonarrangementofplaningmachines.

(1.)Whyhastheliftingofweightsbeenmadeastandardforthemeasureofpower?—(2.)Namesomeofthedifficultiestocontendwithintheoperationofmachineryforliftingorhandlingmaterial.—(3.)Whatanalogyexistsbetweenmanualhandlingandtheoperationofhydrauliccranes?—(4.)Explainhowtheemploymentofoverheadcranessavesroominafittingshop.—(5.)Underwhatcircumstancesisitexpedienttomovematerialvertically?—(6.)Towhatcircumstancesisthedangerofhandlingmainlyattributable?

Anenginelatheisformanyreasonscalledthemastertoolinmachinefitting.Itisnotonlytheleadingtoolsofarasperformingagreatershareofthework;butanenginelatheasanorganisedmachinecombines,perhaps,agreaternumberofusefulandimportantfunctions,thananymachinewhichhaseverbeen[122]devised.Alathemaybeemployedtoturn,bore,drill,mill,orcutscrews,andwithastrongscrew-feedmaybeemployedtosomeextentforplaning;whatisstillmorestrange,notwithstandingthesevariousfunctions,alatheiscomparativelyasimplemachinewithoutcomplicationorperishableparts,andrequiresnoconsiderablechangeinadaptingittothevariouspurposesnamed.

文章推荐:

2015年外交部发言人谈话

一个国家、一个民族不能没有灵魂

中共中央办公厅印发《2019—2023年全国党政领导班子建设规划纲要》

全国最大超级电容有轨电车线路空载试跑取得成功

1941年6月1日 新华社洛阳电:中外记者赞扬八路军战绩

我国“一箭双星”再发两颗“北斗星” 完成北斗三号全球系统核心星座部署

外媒:以史为鉴 金价涨势或难以持续(3)

网友评论

  • 雨花郡主fglep

    Thedirectapplicationofsteamtoforging-hammersiswithoutdoubtthegreatestimprovementthathaseverbeenmadeinforgingmachinery;notonlyhasitsimplifiedoperationsthatwerecarriedonbeforethisinvention,buthasaddedmanybranches,andextendedtheartofforgingtopurposeswhichcouldneverhavebeenattainedexceptforthesteam-hammer.

     Anotherobjectgainedbyequalactiononbothsidesoflargepiecesisthequalityoftheforgingsproduced,whichisgenerallyimprovedbytherapidityoftheshapingprocesses,andinjuredbytoofrequentheating.

  • 雪灵芝StqqH

    Forpulleys,gearwheels,orotherstandardpartsofmachinerywhicharenotlikelytobemodifiedorchanged,ironpatternsarepreferable;patternsforgearwheelsandpulleys,whenmadeofwood,asidefromtheirliabilitytospringandwarp,cannotbemadesufficientlystrongtowithstandfoundryuse;besides,thegreatestaccuracythatcanbeattained,evenbymetalpatterns,isfarfromproducingtruecastings,especiallyfortoothwheels.Themoreperfectpatternsare,thelessrappingisrequiredindrawingthem;andthelessrappingdone,themoreperfectcastingswillbe.

  • 如萱紫儿mtapA

  • 但法国FGO6p

     

  • 大笨蛋doK33

    v

  • 扒皮成zQnZ8

     Inthedrivinggearingofplaningmachines,conditionswhichfavourthereversingmovementarehighspeedandnarrowdrivingbelts.Thetimeinwhichbeltsmaybeshiftedisastheirspeedandwidth;tobeshiftedabeltmustbedeflectedorbentedgewise,andfromthiscausewindspirallyinordertopassfromonepulleytoanother.Tobendordeflectabeltedgewisetherewillberequiredaforceinproportiontoitswidth,and[133]thetimeofpassingfromonepulleytoanotherisasthenumberofrevolutionsmadebythepulleys.

  • 草莓果L9kgo

    Formerlyanapprenticeenteredashoptolearnhandskill,andtoacquainthimselfwithanumberofmysteriousprocesses;tolearnaseriesofarbitraryruleswhichmightservetoplacehimatadisadvantageevenwiththosewhosecapacitywasinferiorandwhohadlesseducation;butnowthewholeischanged.Anengineerapprenticeenterstheshopwithaconfidencethathemaylearnwhateverthefacilitiesaffordifhewillputforththerequiredefforts;therearenomysteriestobesolved;nearlyallproblemsarereachedandexplainedbyscience,leavingagreatershareoftheshop-timeofalearnertobedevotedtostudyingwhatisspecial.

     

  • 绿卡纸kECux

    Asecondpointtobenoticedinhammersofthisclassisthenatureoftheconnectionwiththedrivingpower.Inallcasestherewillbefoundanequivalentfortheelastichelveofthetrip-hammer—eitheraircylinders,deflectingsprings,orotheryieldingattachments,—interposedbetweenthecrankandthehammer-head,alsoaslippingfrictionalbeltorfrictionalclutchesfordriving,asinthecaseoftrip-hammers.

     

标签列表