Classic Racer — September — October 2017

34 ClassicRacer

TheFoxwellSupercharger

TheunusualsuperchargerthatMessrsIrvingand

Willischosefortheirexperimentwasaproductof

DanielFoxwellandSonofCheadle,Manchester.

Themaininterestforthislong-established

companywastextilemachineryandtheFoxwell

blowersappeartohavebeenasideline,apparently

intendedforusewithindustrialvacuumcleaners.

However,itwasacompactunit,suitableforthe

initialpurposeand,eventually,relativelyeasyto

installonamotorcycle.

ThisonecomponentsetsClaraaparrtttfrom

anyotherKTTVelocette.While IvanRhodes

couldgatheralltheotherbitsheneededfor

therestorationfromvarioussources,withouta

replacementsuperchargerit lookedasif theproject

wouldstall. Salvationarrivedcourrtttesyof Velocette

enthusiastDennisFrost,whohadmanagedto

trackdownsomeoriginalFoxwelldrawings. Fellow

enthusiastChrisWigginsdidsomeupdatingtothe

designandhisbrotherRobproducedthecasting

patterns.Anotherenthusiast,HaroldBeal,offfffered

hisservicesandeventuallytookoverthecastings

forfinishmachining,aswellasdealingwiththe

otherinternalparrttts.

Thesupporrtttofthevanesis unusual onthe

Foxwellunit. Acircular,aluminiumbronzeplate

locateswithineachendcapp.Eachpplatehasa

circulargroovethatdeterminesthepathofsix

aluminiumsegments.Eachsegmenthasacircular

holetosupport aroundpieceofbrass.Eachbrass

piecehasaslottolocatetheendofavane,but

thedesignalsopermitsacertainamountoffloat.

It leavesaminimalclearancebetweenthevanes

andthehousing.Comparedtoothercentrifugal

compressors, theunusualbearingdesignreduced

somefrictionallosses, butcreatedothers.

While thedrawingsthatDennisFrost had

locatedhadenabledthecastingstobemade,there

werenoprecisedimensionsforthemachiningof

thesupercharger.Haroldisaretiredengineer,but

healsohasacomprehensivehomeworkshopand

aknowledgeofCAD(computeraideddesign).He

workedhiswaythroughthecomponents untilhe

couldprove,intheory,thatmachiningeverything

totheparametershehadworkedout,the

superchargershoulddoasitsdesignersintended.

Theclearancebetweenthevaneandthehousing

wasjustone-thousandthofaninch!

It tookmanyhoursofworkshoptimeto

completetheworkbut,eventually,itwastimeto

putthere-createdsuperchargertoa‘drytest’.Ivan

suppliedaBest&Lloydoilpump,whichwasthe

sameasthatfittedoriginallytoClara.Therestof

thetrialjigincludeda2hpelectricmotortodrive

thesupercharger.

Apparently,usedinthis application,the

mechanicaloperationofthevanesabsorbsalotof

power.InHarold’sopinion,theoriginalset-upwas

probably worthnomorethananadditionalthree

orfourhorsepower.

Thesuperchargerwasrunforanhour,

dismantledandchecked,thenrunforafurther

hour.Withnothinguntoward,it washandedover

toIvanforhimtocarryonwiththerebuild.

Above:Les Archer,possibly at the1933

BrooklandsGrand Prix, Pa Archer is farleft,

HaroldWillisthirdfromleft, thenEric Fernihough.

IV

A

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RH

O

DE

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Ivan demonstrates

Claraatthe 2012

InternationalWest

Kent Run.AUTHOR

had beenspecially producedinthe Nineties,

but is, regrettably,nolongeravailable.All the

controlcables were madeup frommystock of

originalperiodmaterialand onlytwo features

remainincorrect.The front brakeshouldhave

arod and wing-nut adjustertocomplete it.We

usedaBowden period twistgrip, insteadofthe

originallevercontrolfavoured by both Harold

Willis and Alec Bennett, accordingtoaletter

from high authority–Percy Goodman.”

Meanwhile, Ivan’s son Grahamewas kept

busywith the stove enamelling. Jim Plant

donatedaprimary chaincase,which was

re-worked appropriately with an additionalcover

protecting the chain drivetothe supercharger.

Ivan had discoveredfromIrving’snotes that this

wasdriven at halfcrankshaftspeed.Suitable

sprockets camefromDerek Stride atTD Cross

in Birmingham.Mostof the work wasdone

‘in house’and RayPettittofNottingham made

thefinal components.Sheetmetal skills were

needed to re-createthe plenum chamberand

oiltanks.The lugsthatoncelocatedthem had

also beenremoved, but thesewere re-instated

fromIvan’s stock of ex-factory parts.

John Goodall wasyet another personwho

helped with the project, locating and modifying

an oil coolertotry and matchthe photographed

original.Hemade the pressure reliefvvvaaalllvvveee

that bolts into theplenumchamber.

John wasalsoresponsible forthe

inlet manifold andthe air filterbody thatisa

distinguishing feature of the timingsideof

the bike.

Onetrickypart wasthe pipethat fedfrom

the blowertothe plenumchamber.Thisled

underthe engine and therestrictedspace

allowedlittleroom forerror.The exhaustpipe

wasanotherfabrication project.

Thework wascompleted in 2010 and

the bikewas soonfired up. After further

experimenting, it wasfoundthat the engine

runs nicelyonamix of petrol/methanol in

an80:20 ratio. Usefully,thisalsoworks

satisfactorilywith the ‘Roarer’, another of

Ivan’s high-profile Velocette restorations.With

5psi boost,the engine performsextremely

well.Itclimbed the BrooklandsTest Hill with

someaplomb!

Perhaps,in isolation, ‘WhifflingClara’ was

not asuccess, as no other bikewas similarly

modified. However, the lessonslearnedin

superchargingdoubtlessprovedvaluable

forVelocette’slaterexperiments, as well

as guiding futuredevelopmentsofthe KTT.

Whateverthe conclusions –it’sgoodtohave

her back.

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