Issue 4722 Model Engineer Magazine 20 PAGE FREE PREVIEW

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188SMOKERINGS

News,viewsandcommentontheworldof modelengineering.

189PARKLANDSRAILWAYWEEK

BrianBakerspendsaweekinHemsby,on theNorfolkcoast,atapopular7¼ inch gaugeevent.

194RADIALVALVEGEARSAGAIN

DuncanWebsterexploresthesubtletiesof valvegearoperation.

197AFIVE-INCHGAUGE0-4-0 PADARNRAILWAYTENDER LOCOMOTIVE

Luker presents FireQueen,aWelshslate quarrylocomotive.

201BOOKREVIEW

RogerBackhousereadsJamesNicholson’s bookontheHejazRailway,famouslysubject toraidsbyLawrenceofArabia.

202POSTBAG

Readers’letters.

204LNERB1LOCOMOTIVE

DougHewsonpresentsatruetoscale5inch gaugemodelofThompson’sB1.

207WILLIAMSPENCE

Inhisoccasionalseries,CliffAlmond considersthedesignofthecylindersforthe Guinnesslocomotive.

UP TO 49% Seepage186 fordetails.

213BEERHEIGHTSLIGHTRAILWAY SIGNALLING

MikeHanscombdescribesthesignalling systemattheBeerHeightsLightRailwayat PecoramainDevon.

215ANEWWORKSHOP

PeterSeymour-Howelltakesabreakfrom building FlyingScotsman tobuildanew workshop.

218ADRIVEUNITFORAMILLING MACHINETABLE

IainHailemotorisestheXaxisofhismilling machine.

219FINISHING ELLIE, THESTEAMTRAM

TonyBirdaddsaboilerandprototypical bodyworktocompletehissteamtram.

223THEEATINGOFELEPHANTS

SteveGoodbodyarguesthatanythingis possibleifyoutakeitabiteatatime.

228RECYCLINGA3½ INCH

GAUGESOUTHERNSCHOOLS LOCOMOTIVE

RobertHobbsturnsaboxofbitsintothe Southern’s‘V’Classlocomotive Winchester

232CLUBNEWS

GeoffTheasbycompilesthelatestfrommodel engineeringclubsaroundtheworld.

235CLUBDIARY FutureEvents

http://www.facebook.com/modelengineersworkshop

http://twitter.com/ modelengineers

AndyPotter’sSavagetractionengine Gavroche,seentickingoverbythesteaming baysattheParklandsRailwayWeek (photo:BrianBaker).

NAMEAwards

TheNorthernAssociation ofModelEngineers(NAME) presentedtheirNewsletter Awardtrophyfor2022to theeditorofthePolly OwnersGroupnewsletter, RichardTaylor,attheir recentAGMheldonthe 13thMay2022atthe AndoverSociety’strack site.Theawardgivenwas asuitablyengravedcup, andwaspresentedbyDenis Mulford,chairmanofNAME. Thereasonthisnewsletter waschosenwasfortheclear pictures,clearandveryclean textplusthefactthatRichard writesmostifnotallofthe articleshimself.

heritagelines.Charlotteis happytomuckinwhenthere isworktobedoneandisable toundertakemostifnotall jobsaroundthetrackand locomotives.

Theawardswerepresented byDenisMulford,whosaid“I’m sorryIdidnotgetboththeir ages-Archieisnow11years oldbutitwasimpropertoaska younglady’sage”.

ManythankstoBobHayter forsharingthisnewswithus.

Ihopethatwecanhave agoodturn-outofRobRoy engines,workingornot.There isstilltimetodosomefettling ifneeded!

Refreshmentsandalight lunchwillbeavailable. Ifyouknowsomeoneatyour clubwithaRobRoyplease persuadethemtocomealong too.

PleaseletIanHorsfield knowifyouareabletoattend (07857-336425or01386792628).

TonyWalshaw

Wewereverysorrytohearthat TonyWalshawdiedinApril ofthisyear.Hewastheson ofTomWalshaw,alsoknown as‘TubalCain’,andwasa professionalmodelengineer. Hecarriedoutalotofwork fortheGuinnesscollectionin Irelandandhisworkfeatured frequentlyin ModelEngineer Ourcondolencesgotohiswife AnneanddaughterKaren.

UnknownEngine

RichardSiddall,oftheLeyland SME,asksifanyonecan identifythisengine(see photo),whichhewouldliketo complete.Itsvitalstatistics are:base10⅞ x5½ x2⅛ inches;cylinder2inchesbore andstroke;flywheel6inches diameterx ⅞ inchwide;disc crank3inchesdiameter.Any informationgratefullyreceived!

Acoupleofweekslaterat theWhitwellandReepham ModelEngineeringClub track,nexttotheWhitwell andReephamrailwaystation, onSundaythe2ndJuly NAMEpresentedtheirJunior EngineersAwardsfor2022.

Thewinnerinthe8to10 yearsoldcategorywasArchie Munnings.Archieisdedicated tohelpingtoruntherailway andhelpsoutwithanyjobsthat aregoingon,includingtrack work.Heshowsagoodability tobearoundlocomotivesand miniaturerailways.

Inthe14to17yearsage groupthewinnerwasCharlotte Munnings.Charlotteisalso dedicatedtohelpingatthis miniaturerailwayandother

RobRoyRally

IanHorsfieldfromthe Bromsgroveclubhasaskedme remindyouoftheforthcoming RobRoyRally.

Thisyear’srallywillbeheld onSaturday16thSeptember, 2023-adateforyourdiary! Theeventistobeheldat theBromsgroveSociety ofModelEngineers,next totheAvoncroftMuseum, Bromsgrove,B604JR.

Canyouidentifythisengine?

MartinEvanscanbecontacted onthemobilenumberor emailbelowandwouldbe delightedtoreceiveyour contributions,intheform ofitemsofcorrespondence, commentorarticles. 07710-192953

MEeditor@mortons.co.uk

DIANE CARNEY Assistant Editor

MARTIN EVANS Editor

DenisMulford(left),chairmanof NAME,presentstheirnewsletter awardtoRichardTaylor(right),Polly Owners’GroupNewslettereditor (photoIanMortimer).

Archiereceiveshisaward (photoSueMulford).

Charlottereceivesheraward(photo SueMulford).

ParklandsRailway Week2023

Oneproblemthatweface atParklandsRailway, locatedinthevillage ofHemsbyinEastNorfolk, isthatweareneverquite surehowmany,orifanyat all,locomotivesaregoingto turnupforourannualRailway

week.Wecould,weknew,rely onourregulars,somealready bookedintobungalowsonsite, or‘locals’visitingforoneor afewdays,butwearenever sureabouttheothervisitors, manyofwhomjustseem tocomeonthespurofthe

KevinBrown,onholidayfromEchillsWoodRailway,easesBlack5No.5026outofParklandsCentral,aimingtogetaquickfew lapsinonSaturdaybeforethecrowdsappear.

BrianBaker reports froma regularandverypopular eventontheNorfolk coast.

NigelSurmanhadbarelyunloadedhisHunslet,beforeGeorgeWitheridge,alocal lad,haditinsteamandonthetrack.Wedon’tthinkNigelgotmanydrivingturnsin duringtheweek.

AnotherearlybirdwasMartinParhamfromMaidstonewithhisNERsingleNo1.

moment.Howeverthenumbers thisyear,including43visiting locomotives,meantthat everybodywasboundtohavea greattime…andsowedid.

Locomotiveswerealready unloadingonSaturdaymorning forthisyear’sevent,the43rd,

andwithinaveryshorttime vewerecirculating.Lateron inthedaytheywerejoinedby fouror veothersandwewere stillunloadingarrivingvisitors’ enginesat5.00pm.Thisyear everyoneseemedtowantto bringrollingstockaswelland

wehad,atonepoint,anextra 18coachesto ndspacefor. Nevertheless,wedid tthemall inandalthough,intheory,the railwayusuallyoperateswith amaximumof8locomotives onthetrackatanyonetime, thankstothesmartoperators inthestationkeepingthings

moving,wedidmanageit,even thoughtherewasregularly doublethatnumbercirculating. SundayandMondaywerevery busybuteveryonegotarun moreorlesswhentheywanted toandalthoughsomeleftat theendoftheBankHoliday theywereinstantlyreplacedby

Aregularrunneronthetrack,enjoyinghis rstvisittoHemsby,wasBaldwin Lyn, ownedbyA.Hall,andattractingtheinterestofDonWitheridgeJnr.initsstriking Southernlivery.

ChrisandMickJonesareregularvisitorstoParklandsandthisyearthey alternatedbetweenthiselegantSouthernSchoolsclassNo.901 Winchester and theirGWRCollett.

SophieB isaregularvisitortoParklandsandiswellknownonthe7¼ circuit,fresh fromstarringonthe7¼ InchGaugeSociety’sstandattheMidlandShow.

TheweatherturnedcloudierlaterintheweekbutthatdidnotputoffAlan Beasleywithhiswonderfulshay,orB.HenleywithhisStafford Kitty,visitingfrom Chelmsford.

There’salwayslotsofadviceandcommentaroundanysteamingbaybutIamnot surePeteLawsonappreciatedit,lightinguphisLMS4F.

ConnerDuncanshowingdadJamiehowtodrivethisGWRPrairie5552.

WehadatotalofthreetractionenginesthisyearandAndyPotterbroughtthis ne Savage,whichlookednicelysettledinbythesteamingbays.

IhavetoadmitthatIspentmanyhourswatchingthefullsizedSchoolspullingout ofMargate,WhitstableandotherIsleofThanetstations,andtheywereoneofmy favourites,whichiswhatIpleadwhenIsubmitasecondphotoofChrisJones’No. 901 Winchester

ParklandsRailwayhasamaximumpermittedaxleweightlimitandwhenIheard that TomRolt fromEchillsWoodwascomingIwasabitworried,butthisexcellent model,ownedbyAndySpencer,didn’tworryusatall.

newcomerswhoallseemedto enjoyrunningonourenticing anddelightfulrailway.

Alookattherailway

Therailwaywasstartedas ahobbylinebythelateDon

Witheridgeintheearly1970s andrecentlysomeofhisearly videoshavebeenrefurbished toshowhowdifferentthe railwaywasthenfromasit isnow.Initiallyaquartermile

outandbackrailway,thetrack lengthisnowabout4/5ofa mileandalthoughonesection issingletracktherestis mainlydoubletrackwithavery largereversingloop.Theline includestwobridges,aviaduct, atunnel,athroughstation (LaurelGreen)andthemain terminal,ParklandsCentral. IamsurethatDonwould havebeendelightedtosee howenthusiasticpeoplewere

NigelSurmanvisitseveryyearwhenheandPeteLawsonhelpussomuchwiththe operationoftherailway.However,Nigel’sdecisiontodressastheFatControlleris notonourwishlist,howevergrandhelooks.

abouthislovelyrailwayandhe wouldhavereallyenjoyedthe companyofthevisitors.

Duringtheweekthevariety ofthelocomotivesvisiting wassuchthatIhaveelectedto showcaptionedphotographsto illustratethis-mucheasierthan wordydescriptions.Forpartof theweektheChairofthe7¼ InchGaugeAssociation,Janet Royston,visitedtherailway

forthe rsttimeandenjoyed herselfsomuchthatshesaid shewouldbereturningnext year,asdidourworthyEditor, MartinEvans,whoreturnedto usand,asever,enjoyedhisvisit (orwasitjustthecake?)

Therailwaydoesnotand neverhaschargedforrides. Itsoperationisfundedby themembers’subscriptions, donationsfromthepublicand

Asusualwithroadworks,despitethesignsthereislittleactivitysurroundingthis splendidrollerandowner,JohnDaltonfromChelmsford,istryingtoexplainwhy thisis.

WehadtwooftheseGWR0-4-2tanklocomotiveswithusthisweek;MattGunn broughtthisone,No.4863fromEchillsWoodRailwayand…

Howdoeshekeepthatjacketclean,wanderingroundsteamingbaysandcloseto dirtysteamlocomotives?MartinandMartin(Parham)deepinconversation,nodoubt aboutthecontrastinGNRexpresspassengerandfreightlocomotivesondisplay.

DespitethebesteffortsofthePlatformStaff,youjustcannotavoidajamof locomotivesandstockinParklandsCentral,butperhapstheywerewonderingifa GreatWesternLocomotiveshouldbepullingPullmanstock?

…AndySpencerbrought5806.

Apartfromassistingwiththerailway,NigelalsobroughthisModelTFordagain andenjoyedtakingourgallantEditorforarideroundthelocalvillages.Onedayall carswillbelikethis.

…D.Smithdisplayshissaddletankversion, Bess;thefullsizedversionalsohad bothtypesoftankonoffer.

That’squitealoadfor Jessie topullupDabsonbank,particularlywhenthetrack becomesoilylaterintheweek,butshemanagedjust neinthecapablehandsof ChrisDay.

Thisisararemodelin7¼ inchgaugebutthisisthesecondonetograceParklands. JordonAndrewbroughtthisonefromYorkshireandenjoyedagoodspellofrunning.

AcontrastinHolmside.DawnSmithandHusbandPaulareregularvisitorsto Parklandswiththeirsidetankversion,whilst…

Withoutthevalianteffortsoftheseladiesandthemembersandfriendswhomade deliciouscakes,everyonewouldbehungryandthirstybuttheymanagedtofeed andwatermorevisitorsandmembersthanever.

themodestpro tsthatour cateringvolunteersearnforus byservinghotdrinks,baconrolls andcakeduringthewholeweek. Thisyearwewereverypleased thattheireffortsresultedinan excellentcontributiontoour fundswhichwillnegatetheneed forthesubscriptionsrisingat theendoftheyear.

Forsometimethefutureof therailwayhasbeenuncertain but,justpriortotheweek starting,welearnedthatthe ownersofthesitehadregretfully foundthemselvesunableto continueholidaylettingafterthe

endof2024andthatchanges wouldbenecessary.Sowenow knowthatnextyearwillbethe lastParklandsrailwayweek whichissadbutinevitablegiven thechanges.Assomanywill besuretowanttoattendnext year,ithasbeendecidedto giveprioritytothosestayingon siteandtothoseregularpast visitorswhohavesupportedus overtheyears.Consequently, wewillhavealocomotive bookingsysteminplacenext year.

OvertheyearsParklandsRailwayhavebeensupportersofthe7¼ InchGauge SocietyPro ciencySchemeandthisyearBobWhit eldrepresentedthecommittee andpresentedthreeSilverandthreeBronzeawardstosuccessfulcandidateswho passedtheir naltestduringtheweek.HerehepresentsaSilverawardtoHarrison Frosdick.

AllthewayfromSomerset,7¼ InchGaugeSocietyChair,JanetRoystonbroughther MaxitrackSimplicity,whereitenjoyedafewdaysofbracingEastCoastweather.

BobWhit eldbroughthisC19Denver&RioGrande2-8-0No.407tovisitusagain and,asusual,handledmuchofthepassengertraf c.Sadly,Ididnotgetthename ofthedriver,aCanadianenthusiastwhoseemedtobeenjoyinghimself.

FirstrunatParklandsafewyearsago,EricChurch’sPetclasslocomotiveranwell butthereseemedtobenotakersforthe‘SuicideSeat’.

GeorgeWitheridge,apreviousSilverawardwinner,coachesKyleOliver,who passedhisSilverthisyear,indrivingaHunsletsteamlocomotive,whilstowner NigelSurmanstillhasn’thadadrive.

GWR PhenrhosGrange No.6868,liftsawellloadedrakeofPullmancarsreadyto tackleDabsonBankinthecapablehandsofSimonDuncan.

RadialValve GearsAgain

PART5 –HACKWORTHVALVEGEAR

Exceptingslipeccentric thismustbethesimplest valvegearavailable.The gearwaspatentedin1859 byJohnWesleyHackworth (1820-1891),sonofTimothy Hackworthwhodesigned SansPareil ofRainhilltrial fame.Itisbasedonthe principlesoutlinedinPart1 (M.E.4718,June2)but,aswill beseenlater,ithascertain shortcomingswhichhave restricteditsuseexceptwhere extremesimplicityisrequired attheexpenseofperformance.

Thelayoutofthegear isshownin g19,anda photographofthelocomotive EdwardThomas showsthe valvegear(photo1).

LayoutoftheHackworthvalvegear.

EdwardThomas (photobyPeterBroster-EdwardThomas,CCBY2.0,commons.wikimedia.org/w/index.php?curid=49576914)

Continuedfromp.147 M.E.4721July14

Duncan Webster shedslight onwhatisoftenseenas acomplexsubject.

Fig19

Allofthedriveisprovided bythereturncrank ag which extendstotheoppositeside oftheaxletothecrankpin. Attachedtothereturncrankpin isthevibratinglever gmh,the topendofwhich, h,isfreeto runupanddowntheslide.With theslidevertical,whentheaxle rotates,themagnitudeofthe horizontalmotionofpoint m canbeseentobeinphasewith, butintheoppositedirection tothepistonmotion,whereas themotionupanddownthe slideofpoint h is90degrees outofphasewiththepiston motion.Iftheslideistilted, someofthisvertical,outof phase,motionistranslatedinto horizontalmotionwhichwillbe addedtothein-phasemotion, thusful llingtherequirements above.Thelinkageisarranged suchthatpoint h iscoincident withthesliderotationaxis, j, atTDCandBDCsothatslide inclinationhasnoeffectin thesepositions.

Thisallseemsdelightfully simple,sowhywasn’tthisgear morewidelyused?Thereare threemainproblems.

Firstly,asthecrankturns, theconnectingrodisdisplaced fromthecentrelineandits effectivelengthchanges.This isshownin g20 (exaggerated forclarity).

Usingthedimensionsofthe well-knownSweetPeamodel, whenthepistonhastravelled halfstrokethecrankhasonly rotated86.7degrees,and whenthecrankhasrotated 90degreesthepistonhas travelled1.06inchesrather thanthe1inchcrankradius. Thisdistortstherelationship betweenvalveandpiston andispartofthereasonfor thecurvedmidgearlinein g22.Comparedwithsome locomotives,SweetPeahasa longconnectingrodcompared withitsstroke,sothiseffectis notassevereasinothers.

Secondlyforthesame reason,thedieblockwilltravel furtheruptheslidefromits midpositionthanitwilldown, asshownin g21.Thisputs aseconddistortionintothe relationship.

Thirdly,astheaxlemovesup anddownonthesuspension

Connectingroderror.

Asymmetryindieblocktravel.

Valvetravelvs.pistontravel–straightslide.

Fig20

Fig21

Fig22

Fig23

itwillaffecttheoutofphase component-onatank locomotive,therideheight ishigherwhenthetanksare empty.

Fourthlythestraightslide causesasmallerror.Evenwith noslideinclinationthefront endofthevalverodwould movebackandforthasthedie blockroseandfell.Ideallyit wouldbecurvedbutthatwould costmore.

Figure22showstheoutput frommycomputermodelof theSweetPeavalvegear.The valvemotionhasbeenplotted verticallyagainstthepiston travelhorizontally.Resultsare notgood-strangelytheyare betterinbackgear.Agood gearwouldhavethesame resultsinforwardandreverse andaverygoodgearwould havetheshapeoftheovalsthe sameinthebottomhalfasthe top(i.e.rotationalsymmetry). Deviationfromtheevents whichwouldbeobtainedfrom theidealisedgearinPart1are notnecessarilyabadthing,for instancealargerportopening couldbeobtained.Comparing

theseresultswith‘ideal’would notbefruitful.Backgearbeing betterwasexploitedin ref12, whereanextrarockerwas insertedinthevalverodlinkage toreversethevalvemotion. NotetogettheseresultsI changedtheheightoftheslide slightlytoensurethatpoints m and j coincideatdeadcentres.

Design

Ihadhopedtoavoidanysums anddoitallonCADbutthis wasnottobe.Again,avoiding theworkingout,theradiusof thereturncrank ag isgivenby: ag =inphase+(outphase/ tan(w))

Variousauthorshave recommendedthatthe maximumslideangle(w) shouldberestrictedto20 degrees.Onceyouhave positionedtheslideabovethe axle,theCADcanbeusedto determine gh andverticallines displacedeithersideofthe verticalbetweencrankcentre andslidepivotwillgive mh FurtherworkontheCADwill givethevalverodlength.There isalittleprogram hackDesign

whichwilldothesumsforyou.

Inalmostallapplications ofHackworthgear,thevalve rodslopesdowntowardsthe cylinderendwiththecrankon centres.Thisisunavoidable asonewants j tobehigh tomaximise gh.Atthevery leastithastobehighenough toclearthewheelsatfullupsuspensiontravel.The computermodelallowsfor thisandsetstheslideangle appropriately,inthecaseof SweetPeato5.4degrees anticlockwisefromvertical. Slideanglesquotedin g22 and g23 aremeasuredfrom thismidgearposition,positive clockwise.

Slidedesign

Inmostapplicationsthe slideisasinglesidedtee slotarrangementwith theconnectiontopoint m outboardoftheslide.Thisis notaterriblygoodfeatureand wearisreportedtobefairly heavy.Itwouldbebetterwith aslideeithersideofpoint m asusedinJoygear(see laterepisode).Theoriginal

designerJackBucklercame upwithanarrangementof linkswhichhecalled‘Jacob’s Ladder’whichgaveaverygood approximationtoastraight-line motion(ref13).Thiswillbe exploredinthenextepisode.

Oneofthebeautiesofa computermodelisthatit allowsonetochangethings easilyandseewhattheeffect is.TakingtheSweetPea dimensionsandchangingthe slidefromstraighttoa4inch radiuscurvegivestheresults shownin g23.

Thisismuchbetter.NoteI haven’tbuiltthisforrealbut I’dbeverysurprisedifthe sumswerewrong.TheJacob’s Ladderstraightlinelinkage couldbemodi edtoproducea curvebutthereisasuggestion thatitmightthenfoulthecab, sodon’tleapinyet.Inthenext episodestraightlinelinkagesin generalwillbediscussed.

Therearemanyother manifestationsofHackworth. Marshallgear,alsoknown asKlug,usesaradiallink toreplacetheslidebutitis usuallytooshortsodoesnot givegoodevents.Bremmegear turnsthelinkagethrough90 degreesandhasaradiallink insteadofaslide.Itthenhasa bellcranktoconnecttheend ofthevibratinglever gh tothe valverod.Asthisallows gh tobelong,andtheradiallink isasimilarlengthtothenow vertical pm,quitegoodevents canbeobtained.Thisisvery similartotheStrong/Southern gearusedonquitealotofUSA locomotives.Thecomputer modelwillcopewithMarshall gearanditwouldnotbe dif culttomakeitdoBremme etc.BrianRemnantwonIMLEC someyearsagowithaSweet Pea ttedwithBremmegear.

lTobecontinued.

REFERENCES

Valvetravelvs.pistontravel–curvedslide.

Ref12. SimonBowditchin EngineeringinMiniature

Ref13. JackBucklerin EngineeringinMiniature

AFive-InchGauge 0-4-0PadarnRailwayTender Locomotive

Pistonsandendcaps.

Luker builds a veinch gaugemodel ofaWelshslatequarry locomotive.

Continuedfromp.171

M.E.4721July14

Thepistons

Oneofthecommonthemes inthisserieshasbeen takinguptolerancebetween componentsintheassemblies. Thisisnothingnewformodel engineers.Intheprevious articleImentionedhowthe originalpistonsin1848had adjustableringstotakeup wear;thankfully,ourlittle modelsarealittlemore forgivingwiththepistondesign andmanufacture.

Thetolerancetake-upon theboresneedstobedone withthepistons( g16) andthey,inturn,needto beperfectlyconcentricto therods.Inormallystartby roughmachiningthepiston, leavingatleast0.5mmon alldimensionstoskimto sizewhenassembledonthe pistonrod.Therodisasimple turningexerciseandrequires littledescriptionotherthan tokeepaneyeonthepress

ttolerancesoftheshaft. Therodisassembledtothe pistonbyclampingthepiston inthechuckandtherodinthe tailstockandturningthepiston rodhomebyhand.Ialways punchtheendoftherodonthe threadasanaddedmeasureto makesurethepistonwon’tturn loose.

Thewholeassemblycanbe placedinacolletonthelathe andthepistonmachinedto drawing.Keepthecylinderon

handtocheckthe t.Youare lookingforamechanicallyfree butsteamtight t.Aneasy waytocheckistodropthe pistondownthecylinderwith thebottomopen;itshould dropdowneasily(nopiston ringoroil-thatischeating!). Thenplacethecylinderon a atpieceofgranite(or

somethingsimilarlikeglass); thepistonshouldsinkdown slowly.Theothermethodisto ‘seal’theendofthecylinder inthepalmofyourhandand pullthepistonandrelease; itshouldbounceback.Don’t betoopedanticaboutthis t;it’snicetogetitperfect butpractically,withthesoft

packingforringsandathick steamoil,un-superheated cylinder,youwouldneeda substantialrattle tbefore you’dnoticeblow-by.

Thecylinderendcaps

Thepistonsideendcapsare uniqueforthislittlelocomotive andbecausetheyaren’thidden underrunningboardstheytend tocatchtheobserver’seye.It wouldhavebeenmucheasier togetridofalltherecesses andmaketheglandmounting angesthicker,butIdecided tokeepthemperfectlyto scale.Thisforcedtheuseof mynewAlBrtoimprovethe shearstrengthforthegland studsandIalsohadtosplit thecomponentforeasierdemoulding(photo73).Theend capglandbossesand anges werethensilversolderedto theendcapdisk(photos74 and 75).

Allendcapsshouldhavea spigottomakethemachining easier.Generally,itmakes sensetoaddconvenienthold pointstopatternstostreamline machining.Regardlessofthe qualityoftheas-castsurface,I willalwaysskimthesespigots beforemachiningtherestof thecasting.ClampinganascastsurfaceissomethingItry toavoid,especiallywithsofter alloys.Theeasiestmethodto lineupthecastingistohold thespigotinthetailstockand clamptherestofthecastingin thechuck;thiswillensurethe castingisreasonablyparallel tothelatheaxis.Fromthere themachiningcanproceedas normal(photo76).

Therestofthemachining issimpleturningoperations buthereareafewtips.The pistonrodboreisbestreamed andthisshouldbedoneinthe sameset-upwiththecylinder borelip,i.e.withoutre-chucking thepart.Thefrontcapscan belooseinthecylinderbore, butthepistonrodsideneeds tobeatight t;thereason being,anymisalignmenttothe cylinderboreandthepistonwill becometightwhenit’sclosest tothecap.Keepthecylinder handyandwhenyou’recloseto size,takesmallcuts,checking the ttotheboreasyougo. Alsomakesurethereareno burrsoneitherthecylinderor thecapthatmightleadyou tobelieveyoustillhaveaway togo.Thisiswhereholding backontheboresteamports paysoff.Allcornerscanbe brokenandaveryslightlead inonthelipcanbe ledusing a ne le.Makesureyouhold the lesafelytoavoidan

Pistonsideendcapglandpattern,includingtwoendcap angebossesaswellas theglands.

Pistonendcap nalassembly.Notethedetail(undercuts)thatwouldbevery dif cultasaonepiecesandcasting.

Cleaningthespigotforamoresecureholdwhenmachiningthelargeroutsidediametersofthecap.

Pistonsideendcapcomponentsbeforesoldering.Withthiscon gurationthe pistonrodslidesonthestrongerAlBronly.

embarrassinghospitalvisit becauseyoustabbedyourself withthe letang!

The nalmachiningisdone inaholdingjig.Abottom recess(tocleartheendcap lip)isneededtoensurethe angeseatsnicelyinthejig. Thestudholesforallthecaps canbedrilledforinterchangeabilityusingthesteamport positionsasreference.These sameholescanbeused toholdtheendcapsinthe jigfortheremainderofthe machiningoperations.With thejiginthethreejaw,the backoftheendcapscan befacedandtheglandseal machinedusingthepiston holeforalignment(photo77). Ifthejigismachinedproperly a6mmpointerpushedinthe pistonshaftholewillhaveno wobblewhenspuninthelathe (photo78).

Withtheendcapstillin thejigandareference at pressedonthe xedjawof themillingvice(alignedwith thetableaxisusingaDTI)the atsforthecrossheadsliders canbemilled.Icouldn’tbe botheredusingthedialgauges tomachinethese ats;the chanceofmakingamistakeis toogreat.Theeasiestwayto machinethemisusingaguide collar(photo79).Thisisjusta cylinderwiththeODmachined totheacross atsdimension withaspigotthat tsintothe pistonrodhole.Takinglight cutsacrossthe atsuntilthe collarisjusttouchedwillleave

thedistanceoverthe ats perfect.Thedimensionswill bespotonandthe atswill besymmetricalandparallel aroundthepistonshafthole, makingthelater tmentof thecrossheadandguidebars mucheasier.

Thecylindergland

Thecylinderglandwaspartof theendcapcastingand,after sawingitoff,onlyrequired skimmingtheouterfaceand thespigotpartedofftothe correctlength.Thestudholes canbedrilledwiththegland assembledtotheendcapin theholdingjigusinganM6 screwtokeepitfrommoving. Thestudclearanceholeand tappingholeshouldbedrilled asanassemblywiththeholes tappedusingtheclearance holeasatappingguide.

Drillingthesteamports

Finally,Icouldcomebackto thedrilledsteamports.To matchtheprototypecylinder capstudlayout,theseholes aren’tthesameatthebackand thefrontofthecylinder,soI wouldmakeapointofleaving littlecrib-notesonwhatis needed.Thetheoreticalangles forallthesteamportsaregiven inthecylinderdrawingsbutI wouldchecktheanglestothe sideofthecylinderasperthe norm(photo80).

Facingthepistonsideendcapandboringouttheglandhole.

Checkingthealignmentofthecentreholewithapointer;ifeverythingisablur exceptthepointer,you’regood!

Machiningtheguidebar atsusingaguidecollar ttedtoashaft,slippedintothe pistonrodhole.

Checkingalignmentofthesteamports tothevalveslots.

Theexhaustportsare simpledrillingoperations withthecylinderassembled and-otherthancheckingthe depthandmakingsurethe holesclearthereferencehole drilledpreviously-posedfew problems(photo 81).

Final owthroughthe steamportsandcylinder exhaust ange

Thesteampaththrough thesecylindersisrather unconventionalwhen comparedtoother locomotives.Thesteaminlets arepipeslikesomeofthe Cramptonlocomotivesandthe exhaustdoesafewtwistsand turnstogettothesmokebox fromthecylinderassembly. Ipaidcarefulattentiontothe owdynamics,withthe ow

pathsspeci callydesignedfor thesecylinders.Theoriginal locomotiveactuallyhadvery wellproportionedas-cast steampathwaysandwas probablyagoodsteamerwhen thepistonswereadjusted properly.Thereareafew notesonthedrawingswhere cornersneedtoberemoved, speci callytheexhaust channels,todecrease ow impedance.

After ttingtheendcaps andusingthemasdrillingand tappingjigsforallthestuds, thecylinderandboilerpadscan be xedtogetherusingRTV silicone.Aftercuring,adrill shouldbeturnedbyhandinall thesteamchannelstoremove any ashfromthesilicone. Beforepaintingthecylinders, anytraceofsiliconeneeds

toberemovedbywipingwith asolventtogetproperpaint coalescenceandadhesion.

Thevalvechest

Thevalvechestisproof thatIcanfabricatecertain componentsratherthanbeing lazyandjustcastthem.In fairnessthough,itwasmuch easiertosolderbrasssquare bartogetherandmachine thegeneralpro le.Thevalve spindleinsertandglandwere madefromleftoverAlBrrisers. Theoutersurfacewas led usingengineeringbuttons andradiiguides,withthe restofthejobsimplelathe turning.Theglandshould haveadistinctroundand steponthevalvespindle,if thefullsizecomponentsare followedpedantically,which

ofcourse,theyshouldbe!This iseasilyreproducedusinga formingtoolinthetailstock, groundtothecentreline similartoasimpleD-cutter.If youdon’twantthebotherof heattreatingsilversteel,any brokenHSStoolwitharound shankwouldmakeanexcellent cutter.Togetaperfectround recessatthecentreoftheHSS blank,itisclampedinahand drill,whichisinturnclamped down(safely).Thisissetto runasfastaspossibleanda seconddrillormicro-grinder withasmallsphericalgrinding wheel(ordiamondbitfrom thenextvisittothedentist)is usedtogrindtherecess.It’s surprisinghowthetworotating partstendto ndthecentre. Therestofthegrindingisdone theusualway.

Thesteamline angesfor thevalvechestfollowthe prototypewithanO-ringas sealing,suitablyshieldedfrom thelivesteam(photo82).A numberofthese angeswere neededsoitmadesenseto drillalltheboltholesinastack oftwoorthreeusingadrilling jig.TheslotfortheO-ringwas cutusingasimpleclamping xtureinthelathewiththe groovingtoolgroundfroma brokencentredrill.

The angesweresilver solderedtoasuitablybent pieceofcopperandthiswas softsoldered(hightemp,i.e. Pbfree)tothevalvechest. Similarly,thespindleinsert wasalsosoftsolderedwiththe glandstudstappedthrough boththeglandbossandthe valvechestsides,tomakeup foranystrengthshortfalldueto thesolderrunningatelevated temperatures(photo83).

Valvespindleinsertandsteaminlet pipingand angesoftsolderedtothe valvechest.

Steamportsdrilledandmilledtothecylinderbore.Notethecentrelandfortheendcapstud.

Valvecheststeam anges,groovemachinedinasimpleclampingjig.

lTobecontinued.