MARLES STEERING GEAR M A NUAL AN D P OWE R -ASS I STE D

FIrst published io MOTOR TRADER November 5, 1958

• -" /u!aClUrtrl : Adamanl &ginuri'TJ: Co ., .d., Dollo.., Road, Lu/o'l. &dfordshirt.

D ESPITE many other deve.Loplmnts of the automobile since iu incep­tion, the basic urangemau of

' l ing compooents bas altued very ~. Early coach designers had under.

stood the need for unltlng the pair 01 Slcered whccb 10 that the vehicle fol­lowed a true d rcular path, and it soon bCCiUIlC accc~)!cd that a wheel was the most convement method of controUing dicl:Ction.

The conversion of a rotary movement of 11. wheel 10 a aide-Io-side N fore -and. aft movement of a drOp arm entailed a gearbox 10 give a rcdllCCd. ratio cl rota­tion and, U • matter of design in most cascs, to ",un the planes of rotation thrCIugb a r ight angle. Since rhc cnd of the drop ann is cmpiOYl:d to deliver • linear motion 10 the steering arm iu H e of rotation i. lImall usually less than onc quarter of a turn. Thus the steering g~r must provide quile a r roucrion in ratio so that a reaiiOolllble degree of rotation of the steering wheel from lock 10 lock corresponds with thi~ limited arc of travel of the drop arm. The actual ratio is chosen {O ~ive a balance between too

'ct sleer lng (giving heavy steering. .cul ty of eonuol and pronounced

" k id< back ") and [00 low-gcared (givins: light steering but requiring too great a movement 01 the wheel to s:ive a desired ddkctioa for the cornfOR of !.he dri"er).

The ratio of reduction lIIlId chlllllge cl " 'pecl ion are luch lIIS to suggest III worm

wheel fo r the gearing. This has ... ~.:n employed, but since the drop arm shaft has such a limited rota tion, only a secrot oC III wheel is normally employed. 11 is appareot that only slight welllt be­tween the worm ~nd wheel (or simillllt mc.:::haoism) win give a greatly increased free movement of the dron arm, and thus of the steered wheels. Thus many other designs, employing a worm and various types of roUowen, ha"e been evolved to inerease the area of contact of the com­ponents I nd 10 redll« the friction in the mechanism.

One o f the few recenl basic develop.­ments has been the adootion of power­a$Sisted steering. With the development of modern lIIu[omobile$ a number 01 diffuent factors have combined to in_ crease the SI«rinR effort required. such a s heavier front axle loading. aod the use of heavier 10w. pre5Sure rrreJ. This has meant that the balance 0 stterin<! rati". hu been upset . To provide B sufficiently light steering tOO many turns of the wheel Crom lock to lock: are r"quired.. This has

DOtJ3LE

Sect/OIls of the IIthler Marle • • l~rint boxCf of che double-roller type. The mull is odjusted by setscrew and lhe rocker shof! moy be overhunt or SIJPporud by on odditlorKIl end

beorlnt as shown in ~ scrap view. Com Is carried III cup and COlle ball beorlnts

led to the inuoduction of power-assis· \lUtce, usually in me lann 01 a hydraulic double-acting ram.

The conlrol 01 this ram is by a valve which should provide a reaction to the turning of the wheel to provide "{eel." Another csswtial feature is thai, in the event of power-assistance failing, roan ual $leering is still poIisible. Power is usually provided by a hydraulic pump moum~ in unit with reservoir, filter, and coouol and relic! valves, the pump usually being driven by pulley or chain from the engine.

The Marles steering gear has been in use in various stages of development for many years. Its ou/standing feature is thllt foetion and wear arc minimized by providing roUins:, lIIlId not sliding. motion between the cam (or worm), and the rocker shlllft and roUer (or follower). This design thus ensul'C'$ a long service life, given rell50nlllb le IDlIIintenlllnCe, and pro-­vides l is:bt steering. The late. t Iype employs a double roller on the rocker shalt, thus giving greater bearing surface. With iu robun construction it has been filled widdy to commercial vehicles and to the larger eau.

To enable the benefi ts of powe r. aSliltance to be realized without grell ehpn~cs in chassis design a further development of the Marles steer in!: box has an additional control '1Ilve embodied on the gear c\Sing itself. This is used in conjunction with :I pump unit and a hydraulic ram which can be connected to any convenient poiot in the steering linkage.. n, for r.:Il$Oll ' of space or other considerations, this system, known 1$ Ihe univers.al Wl il, C8nnm be employed, Marlu also offe r a seU-ronlained l inkage un it. nu, component combines con trol va lve and power ram and is mounted in luch a way that the drop Ilrm applies movement 10 the valve lever via the drag link, while one end of the ram trans rers movemem to the steering ~rm. In both these sptems, since the power assistance is applied to the linkage, the steering gcar itseU is not subject to any greater forces

thao with manual stecrill£ j In fact its lile is less arduouJ.

Owing to the design of the Marles n eeting gear, repair is \IJ\Iikel.y to be neces.sary for a very long period provided that lubrication is correct. Attenlions are norm.:d1y c:onfi.ned 10 adjustmalt, and in the event of repair beillf necessary il sbould be comidued that wear is likely 10 be general and that replacement units are available. In any correspondence concerning these units quo te the type and serial number which are stamped on the Sleering box casting.

Power--assisted. steering components contain few moving parts Qnd arc con­tinually lubricated by the hydraulic fluid, therefore tbeir sc rvice lile is e~ceptiODally long. Premature failure can be caused by the use of tbe wrong 8uid or by the entry of din intO the system. ElIueme dcanh. ncss should be observed du ring any ser­vice ulteOlion 10 the bydniulic system and patl$ should not be d i'mlIntled or the circuit broken unless il i-s obvioU$ly necessary to do £0. N ote that Unified threads and hexagons are IoIsed in the hydrltu lic part of the steering unit.

A special test r ig is nccuslIIry for com­plete tcsting of the integral power_ anisted unit after assembly; Ihis point should be borne in mind before a unit is ,jismaOlled.

DOUBLE-ROLLER

STEERING GEAR Construc tion and Oper ation

The static components of the steering box are the casing a nd the colwnn tube. The column tube is a ttached o r clamped 10 a tOp cap relained by seucrew$ 10 the casing. There is a bottom ClI p ! imilarly retained. and both eaPI' ore recessed to take the caps of taper ro ller bearings. The cones afe mounted on Ihe earn, to which Ihe column is keyed. The cam i1 in the fonn of a wl isted (hour-glass) .0=

ServicinG Guide to British Motor Vehicles

The casine also ha. a side cover plate which ha. a bronz.e bushed boss 10 sup­pon the end of the rocker shah. This protrudes through a long boss in the opposite ,ide of the c~sing where it is supported in IWO bron~e bushes, with a lipped oil ,cal at the outer end. Beyond this prouudes the tapered and secrllted cnd of the rocker .haft with a threaded cnd ponion for the nut and spring washer which relain Ihe drop ami. Fonned on the rocker shaft is a double­lugged pro)eclion intO which is inserted the double roller. 11ti. rurn; on needle rollers on 11 pin passing through the lugs and riveted over. ThruSt washers fil between the lugs and the double roUers, and between the flanks of the projection on the roeku shah, and the casing and side cover p!:J.le.

The effective radii of the cam and the rollers on their respective shafts are together greater than the dimension between the shaft axis 11$ mounted. Thus the roller axis is not cemraUy below the Cam axis, but offset to one , ideo The rollers thus mesh sligluly to one side of the cam, and it follows that the depth of mesh can be rontrollcd by altering the latccal position of the rocker shaft.

Note that the double roller is free to turn on needle roller bearinGS so that the rollers can remain in rolling contact with the cam al all times. This feamre of the design ensures that friction is reduced, wear is almost eliminated and internal clearances can be almost negligible. The CIUlI is, of course, rigidly locau d by its opposed taper roller bearings. Note that column can be tubular so that it is a simple maller to inrorpoIate wiring which can be brought OUt thrOugh a modified bottom cOlo"er.

Service Aueutinns

LUBRICATION. Only an S.A.E. 90 oll approved by Ihe ve hicle manufacturer should b~ u~d. and changed as the manu­facturer specifies . Under no circum_ stances should grcue or solidified oil be used. A filler plug is fitled at the tOp of the c .. sing and the box should be kept full. When refilling, it is advisable !O jack up front wheels and rotate steering wheel to prevent format ion of air locks.

ADJUSTMENT. Before assummg that free movement in sleering is due to play in steering box, check that it is not due to wear or loote connections in linkage.

There are only tWO main adjust­ments:_

Cam Bearings. To inspect for corr~ t adjusunent, jaci< up front wheels. Turn steerlllg wheel about onc turn to right from straight ahead driving posi­tion. Secure in this position to p«:vcm ~ny oscillation when front wheels are shJken violently. This can be done by tying onc spoke to a right side door column and holding the wheel against it as a brace. Grip column with other hand just below steering wheel with side of finger barely touching lower cnd of steer­ine wheel hub. Now have an assiSlam shake front wheels hard sideways. This will enable any end play in cam beatings to be relt by up and down movement of inner column at wheel hub. Any end play must be removed by adjustment but be sure e nd play h felt, and do not be ron­fused with play or give in the box nOSe rocker shaft bushes. Cam bearing adjust­ment should be COffect before any further adjustment of gear is made.

Cam Bt aring AdiUSlm~ nl. It will be noted that between the box casting and the bottom cap h a number of thin shims. End play of the cam between ItS bearings may, therefore, be taken up by taking out onc or more of lhese shims, thus allowing the be:tring outer "'CI:, backed up by the bottom cap, to ~nter further into the steering box and thus come closer 10 the cam. When this adjustment has been l.."Qrfl"<:t1y made, it should be such that after the bottom cap is aga.;n fastened securely to the box casting by the screws, the cam and ~leering whed should revolve freely, bUl there should be no end play at all.

Correction of gear m15alignmelll . Loosen the frame b ... cket bolts JUSt suffi­cient 10 allow gear to move in frame 10

line up at angle determined by height of instrument board bracket or dashboard b ... cket , then rc_tighten frame bracket bolts. Now loosen instrument board bracket or dashboard bracket bolts to match gear column position, and re-tighten all bolts. This will have corrected any possible misal ignment of colwnn.

Diagrammatic viow ar the MQrlcf linkage-type steerinJ: a .. istance unit, sh_ing valYe aperatio~ (alsa aPfJlicable to univer",,/ unit) in detail. Valve lever is held In posltlan by light springs, bur movement either way brlngJ heavier ce~trolizing springs into play acting an valve pistons. When valve I~er is central. fluid flaws uncheCked through u~it, but when lever is disp lace4 (on right) annular port< on one valve prevent return of fluid and divert it to appropriate side of power ram, while ather va/ve allows fluid to pan from a[her side a( ram. Note that valves are not in line. so that reactions caused by fluid pressure an valves impose di fferent torques on lever; this com!spond. to difference I~ effective areos ofthc tW"II

Jides of rOm pislan caused by intrusian of piston rad. Thus reaclion is praportio~al to pawer­aS$luance. loIver end a{ valve lever m~t< stops on caJinr 10 provide manual .t~rint if

Mceuary

l[VU

Mesh Between Roller and Cam. In­spection for proper mesh of rocker sbaft roller in cam should never be made with­out first correcting adjustment above. Turn steering wheel to the mid posilion of its complete tra~el from lock to lock (drag liok previously disconnected). Shake drop arm to d etennine amount of slack or lost motion. If this lost motion eX­ceeds one thiny-second of an inch, adjust­ment should be made. It will be seen that the J.>05ition of comact between the roller and cam is offset from the =tr~­line of the cam and that a number of thin shims are located behind the rocker shaft and between the thrust washers. By re­moving one or more of these shims the rollo:r is pennilled to enter furth er into the steering box .lOd make closer contact with the cam.

The proper method of carrying OU t this adjusuoent is as follows: _ Remove drop arm from th ~ rocker shaft and rocker shaft compl~te with the shiJrus and the thrust washers from the steering box. Care should be taken ro see that no shims or thrust washers are left behind in the box to cause interference with the operation of the gear. Select by trial the proper nwnber of thin shims (keeping inner thrust W2sher . with its chamfered side next to the rocker shaft) to produce nm more than .006 inch of play measured at the end of the drop arm when the roll er is p:lssing over the centre of its travel and without heavy drag on the st~ering wheel. Remove only onc shim and insert rocker shaft into the steering box. Now turn the steering wh~1 till the roller almost reaches Ihe slap nearest the column. Hold :-ocker shaft in place with thtunb pressure and revolve SteerinG wheel unli! roller is in its central position. Still hold­ing the rocker shaft in position with the tbwnb, test for play by gripping the spllned end of the rocker shaf!. If an)' pl;y is felt, remove another shim and cc­peat the opcration until all pl;y i$ eliminated ",·hen the roller i, in the CCOlr~ nf its travel.

When the proper number of shims has been sclected, turn the steering wheel so that the roller comes close to either lock and replace 3t the coverplate end of the rocker shaft all the shims which were re­moved during this adju! uoent. These shims should be inserted between the tllrwt washers. After this has been done, replace the rovc rplatc and cove rplate liner and loci< up with fined bolt and setsc rews, making ~ure that nuts on fitted boIl and setscrews are tightened securely.

Fit me drop "rm to the rocker shaft Just sufficiently right to ensure no play is present in the splincd joint, and check for end float of rocker shaft. If play is pre­scrtt, this is corrected by addition of the required nwnhcr of shims behind the

One application of the Ijn~age-t~pe unit. The drat lin~ I. attached to the val .. e le .. er. the ram rod anchored all the chan;s and fhe cylinder to the relay lever. Mony

other arrangements ore p<mible

Sec!!on o{the u/I; .. o:"ol type. in which the ten oral dos;r" is tIIDt Of the /ttovier type of double-roller manual need,,: bo;t,

but .. aloe IInll is o ttoched to end. Getlrs referred to In rut (lre A (HI tnd of volv" nxI. 8 on spindle below and C on md of (om column. Nou then olld 0(

,,,/u rod con" flQ(lI •• ,id_or'

-,:wcrplate, Thil cbec::k m us.! be made irh the toIkr over on full lock. No end

d"" l whalever is pC'tmiuible, but the rod<er abaf, should tOtate quile [r«:]y. If the movement of rockn shaft is heavy it would indicate 100 much pre-Ioadine: on th" lhrun washer and is corrected by r~ moval of the shims as ne~cssary from be·

ind the covuplate. NOTE.-Altcr any or .U ad juSltnents

have been tn9.dc and before repladns the steering gear in the car or before con­necting the drop arm to the drag link, t~t the gear for freedom of operation through· OUt iu available movement and test also fo r absc:ncc of cnd play in !he rocker .haft.

Movement of the drop arm is rcstrict~ by lock naps inside the ueecing box, but the lock slaps on Ihe wheels should come into use before these are mel. If lhe rocker dtaf[ hits iu SlOp on one lock, but nOI on the other, it ind lCllles mat the o;hQp arm Ius betn incorrectly positioned.

UNIVERSAL POWER­ASSISTED STEERING UNIT

(lntegr.&l Valves) CoostruC"tion aod Operation

The Marks univenal type of pown­'ssinw sleering unit oonsislJ of the lIan_ ~ rd M arln manual necti~ unit witb a

valve unit mounted 8t tOp or bollom for controlling a separate double acting jack in place of the bottom covet.

The whole syslem consists of an engine­driven pump with I"Cservoir Row control and relief valve, the manual nccrina: un it

·ilh ~1«rinJ cont rol valve and the .ydrauli<: cylmder connccted at any con­

veni"nt pOLnt in th" steering linkage. The hydraulic system is Ihe usual Con­Slanl flow variable preSlure type employ­ing piston type va lyC$ wbich iLrc open m Ibe o"utra l position. Due 10 their pi$lon action the pressure used 10 steer the vehicle is also used to prodU(e "feel" lit Ib" steering wheel.

The inner column of the steeriog unit is separated from the cam column and cam anembly by a 10sI motioo joint. T bis joint consists of a pin throulL;h the inner column wt)rk ing in slou in tbc ,l"evc. When woe-king normally tbere is no contaCt bcctween the pin and the ends of the slol$ but should the hydraulk Il$sislance fail for any reason, the cam is d riven direct l,. by the stcering wheel through Ihe pm.

The "nd of [he inner column carries a valye rod which passe. through the elm and cam oolumn inlO the vl lve box. The low"r "od of the valve rocl hu a gear wt."el A ko:yed to it .nd .lso carries the valve operating roller which run. on need]" bccarings. The gear A meshes with ~ wider gear B which rot3tes freel y

on needle meshes i the cam column cam manual steering dfon Slcering thus passes column through the Ihr"e geau ,=.

The r"attion from tbe first g"ar (A) is rcsisted by the pressure behind Ihe valve pistons which bear on the valve roUer. When Ihe driver tunU the $leering whc"l a torque is apf'lied by the inner column to fi;car (A ) which moves the gelr and its $haft in a direction tangenti.al to gear B. The shaft is sufficiently flexible 10 allow this small sideways movemcnt. This movement is l rans("rrcd. to the valves which then ratria Ihe /low of oil and caus" pressur" 10 be built up in onc. "nd or om"r of the sleering jack. This prt"S_ SUI"(: is abo I pplied 10 Ihe " od of the valve piston wbK:h bas bttn displaced OUtwards and tends 10 force it towards tbe cemr". This force is resisted by the lorque applied [0 me gear wheel. As this lorque to maintain displacement of th" \""alves is proponiooal 10 Ihe prcJlure .nd is applied by the drive through the stcering wheel Ibe .,ffon ."."tled by the driver is proportional to the pressure which is i[self propoltional 10 the .,ffort ncceuary to steer the road wheels. Whcn sufficieO( pressur" is applied to Ihe sleer_ ing jack the whole system will start to move and the cam and gear wheel system 10 rotate.

This rotation of the cam in the same dirc<:lion as [hc [orquc on inncr column will tend to relieve the force between the tWO gear whccls A & B and so allowing the valve shaft and valv" piston to move towards the centre and release the pres­sure.

Thus so long as the driver continues to turn the wheel Ihe valves are displaced but u soon as he S[OPS the slight over_ run by the: cam, driven by the: cylinders, allows Ibe valves 10 assume a position where a Slate of balancc is obtained bclween th" force necessary to maintain Ibe road wbeels in [he desired dir"ction, Ihe pressure neccsJary 10 produce tb is forc" and the d isplacemenl oC th" valve pillons so tbat the r"quired P"'$$ure is omained.

Any" kick " horn Ibe road wheels will caUK the valves 10 be: displ~ in the Slme way as turning tb" wheel by Ih" drivCf aUK~ their d isplacement. For this case, however, Ihe: direCiion of d is­placcment will taUK preuw" 10 build up ID such a direct ion that tht .. kick " from

MARLES STEERING GEAR

the road whc~ls is ruined and i~ no! (ransferred to the !(eering wheel.

The operation of the: hydraulic system I nd thc valve is e:llacdy 1$ e~pla ined for th" linkage system.

Service Allentions Owina to the &mall working ckarances

in thc valves and other parts the greatt"St danger to I hydraulic Iystem is din. The , rcateSl care Ihnuld be laken wh"o check­.ng or refiUi.na the reservoic to ensure that no din is aUowed to enler. If any ~rk i.1 done on the Marles power stcc.­IIlg unll, other thao the rwo sunple: adjusl ­ments provided, it is beller to remove tbe ... nit frwn the vehicle SO that it can be Ihorouahly cleaned CX(c;n"l.Uy before il is open"d.

Th"se instructions oovcr th" hydraulic valvc unit only. The maoual pan of the gear should be: serviced in accordanc" wilh the inSlrU(OonS for the M arles s["cr­ing gear.

Servlcinr with unit IUOUllted iD the chauis

(i) Ch"ck level of oil in tbe reservoi r a~ lOP up it neces,..!y using a hydraulic oil sU(h as Shell T e:lIus 27, Mobilflwd 200, tbe oil used fat American type fuUX automalic gear boxes or a good en~e 011 to S.A.E. IOW. Do not m ix differem makes or grades of oil. If much oil is required check the system thoroughly 10 determine cause of Ion.

(ii) Check the level of oil in the manual pan of the steering box and fill up if necessary with a good fi;ea. oil 10 S.A.E. "'. (ii;) Check for fl ow of oil from mc drain hole in the low"r cod of the outer oolumn. If oil is flowing from this hole it probably meanl thll one or both or the internal oil seals h leaking.

(iv) Adjuni"t: m'il! of w/ve·opuati"g gern- whuli.

If play an be felt when the steering whet:! is tumed tbrough I very unall angle when the "ngine is runn ina tbe mesh of the spur eears (A, B and C) may need ad­JUSting.

Two adjustmeots a re provided. 0 0" is a serew 10 adjust the mnh bC1weell A and B, Ihe othCT is an ccx:enllic shafl which Mijuau the mesh of B with C. T he: slotted head of the shaft is sllmped witb a centre pop which mows th" highesl point of the eccentric. Adjustmenls shouki be made with the enain<: switched olf.

Servicine Guide to Bri tish Motor Vehicles

To (:;Ifry OUt the adiustmellu firSt dis­connea tbe dng link from the drop aon. Slacken botb loek nuts and remove the onc 00 ad.justing saew and the oil sn1 unclc:mcath it. Slacken adjustini' screw and increlUe mesh of B by ruming lhe: eccentric: $haft Wltil light resisrance is felt. T ighten the IIdjustina: screw lightly u ntiL resistance is fel! . Now nun the gear by means ol the uceritls: wheel. If the teeth can be felt bumpini; over onc another the adjuiuncnts are tOO l ight. Slad<en 011 fir$[ onc adju.nmcnt and rueD the gear again and then Ihe other unlil bolh gears are cor­rectly in mesh with no bum ping.

Replace oil 5nl and locknut nn SCJew. Tighten both locknuu and rceooncct drag link.

(v) Oil leaking from QTound rhl! TOCItIfT $halt can be ",,"cd, if the $holt il nor damGf,d, by /if/ing a nnu eil sta/.

Remove !he drop arm and wi!hdraw the o ld SQI. Thorougbly clean the recess and the rocker shaft cnd, remove any burn, wrap some thin lOUgh material such IS ~heet Cellophane round the splinn and fi l a new oil seal with the lip toward, the body of the box.

When refining the drop arm, a Un;ll! quantity of dry gnphile on the splinu will cue removal on a future occasIon.

(vi) TCJling l or /a,1t 0/ JtCllring 4$Jil_ !al1cc.

In order to check the peTformanc<' of the whole unit and to locate the reason for loss of stee r in~ aSlisl)nce, ti rst check the oil level, and If this is yti,raclory, insrill a stop valve ill the pj~ from tht now con­Hol valve to lhe sl«ring un;l Wilh a pres­lure g-~uge between the flow conlrol valve and tht ,tOp """

With the valve

u p ·proves thc {lump !tIg unit should chusis and Ihe "\,, non-retu rn by·pau

If there is no dose

, Disma.lltling

•

Finl remove the unit from the ch~ssi~ IInd thoroughly clean tbe (Jutsidc. It on­not be tOO strongly Stres~ that the rnl secret of trouble· free oper.l tion of hydt3ulic equipment for long periods is cleanliness and the exclusion 01 :iJI din.

As th~ valve box Cln be mounted in four di lferent plnitions On Ihe bouom of the manual unit, tht posi lion of the valve box rduive {O the monual unit should be noted and marked.

Complete dismantlin~ is most easily done in the follow ing o rder :

(i) Rnnove fWO ""Ive plalC'$ and dis . rane.: piccc.s, .. 0" rinp, sprin~ and valve lieev~ and valve piston.. Bc c;a.rcful nOI

to damage any or the grooves in the valve $luvcs Cl piSIOlU. Keep each p is ton with iu OWll sleeve as cllcy arc lapped. together in palr:s.

(ii) Rrmove back C(lverpiale and rocker $luft as for manual unil.

(ui) Remove Ihe four boltl fixing the valve bolt 10 the t»uom Clp adaptor and bo~

( iv) Draw off valve box leaviog tbe 3daplor pbte in position..

(v) Wnp a shuI of $OIIle th in mIItaiaJ such ai C<:lIophane or: celluloid round the gears (A and C) to prorccl the lip of seal and withdnw bollom c:ap. K eep adjusting shitm arcfully logCthcr for rCII$$C:tJIbly. Remove roller bearing cage.

(vi) The whole cam, inner column and valve shah assembly can now be rerooved. through the bottom of lIle steeriog box.

(vi i) Remove circli p, ad justing roller. spaccn and gear. Note tbe adjlUting roLlcr nms on nc«ile roUers gnd the gear is loaled by key.

(viii) Drive OUt pin. Tht inner column and valve lever can now be SC:PlIraled. from the cam column aod cam as.sembly. Do not remove bus.h or gear unless absolutely ncx:usary as !hey 3fe a press fit on the cam column IS well as being p inned.

(ix) The remoV31 of locknut allows the eccentric :adjusting screw 10 be withd.r.aIVll from the valve box thw pcmUlting the removal of geat.

Jn~tioQ

Afler d ismantling, all pans shouJ.d be c.JC1Ined and inspected for wcar or damage. This u mostly $ln ight forward but the followi ng: points should be w:uched..

Ci) S t als Qnd" 0" Ril1l!s. AlL $(au and " 0" rings used in this unit a re maker's standard. produetion sizes. The nylon bearing at Ihe bouom of the inner column is a special. AD seals and '·0" rings should be supple, free from cu tS, cncl<s or fill spots. ADy M'Jl showing Ihe leau sign of damage should be n:placed..

Owing to Ihc difficulty of withdrawing: cam column seal .nd the dange r of damag­ing fhe scaling lips on Ihe ge~ r tecth it is adviuble to fit a new onc each time thc gear is di$llUJltled.

(i i) V4l",.. Vdves should show velY little 'ign of wear eveD aber long service unlns grit has been allowed to ge l in with the oil. As there are no seais between Ihe stniOtlary and movin@: PlIfU of the valves then: is always a liuk leauge. This is chttked in a special g:.uge dUIing manu· facture to emUfe thJ I it does nOt exceed .06 !t.p.m. wirh Ihe valve fuUy clo$.;d. Check for freo:dom of operarion.

(iii) See tha, the J?Drtion of the cam coiwnn where the lipped seal s.cats is free from scratches or roughnQS.

An cDlbJ,. Assembly of the universal type po,",r

$leering un:r is carried out in Ihe revene order to dismoontling.

(i) Asscmble inner column valve column ~nd cam col'Jmn by insefling pio. Note Ihat Ihis pin is in F..N.36 H igh Tensile Srl.-cl and an ord' :-.a ry soh stecl pin must on no account be used. "Illis pm trans· mits fhe drivet"s st.:cring effort if Ihe hydrau lic system fails or the vehicle is being moved without the engine fUnning.

Cil) Fit gear with kev to valve shaft, followed by splICer, adjusting roller on n~le be.lrings, a ~ond spacer and circlip. Cheek thal when the leeth of the tWO gear whetu A aod C arc in line thc pin is in the centre of ils slot in bush.

(iii) Insert cam and colwnn aucmbly in steering bolt wi!h cam bnrings. Replace ~ing cap with Ihe necessary ad,wtment shims. Tig~ten nun holding cap and check prcJ~d adjustment.

The torque necessary to turn the cam should be 2/6lb/ins, wbich is equivalent to an aaial prd oad of 100Ut 801b. If lhis figure is not obt3ined. add or remove sbims from under the bnring cap as DCcessary.

Shims I~ oblainable in .005, .008, .010 and .015in thicknnse1.

(iI') Assemble gcar B illlo valve bax wilh special sPlIcers either side of the £;car, and leave lIle c«entrie adjustment screw in il:1 10,",it posi l ion. Sce that adjusting screw is slacked back.

(v) COli lIle outside of sal with a thin C031 of ioinl ing compound and using a lhin piece of protec::tive wrapping such as C<:llop.'l~ne or ce lluloid to proteet the $Cal­ing lips from the gCat wheels, 5lide the seal into po~ition . T ap it firmly home with a piece of lubing 01 suirable siZe.

(vi) Fil valve box into position and tighten screws.

(vii) Ad jnn mesh of gutS Band C while rotning the cam by turning eccen­tric pin. Continue tightcning Ih~ adju.t­ment until Ihe leelh of the tWO scts of g:ears can be fclt bumping agaiost each other. Then slacken off until this bump­ing JUSt di$aPPcars. T ighten the locknut.

(viii) Fit valves complete with ,. 0 " rings and springs. ret.:linmg with plates.

(is) AdjuSl mesh 01 gears A and B by tig:hteniog adjusting screw until bump­ine: of lIle teeth is felt whtn the cam is lumed and Iben slackening off the ,dju". menl until this bumping juSl d illlppcan.

(x) At this palm ~nd before fitting the rockeuball it is advisable 10 test selu and by circulating warm hyd raulic oil at a pre~sure not exceeding 6Olb/sq in and a temperature not over 160· F. through the valve box.

(xi) After this test complete building Ihc manual side of the sleering box.

NOTE: Adjustment of rocker shaft mesh must only be made wi th the foller JI the centre of the cam. There will then he backlash on lode.

(xi i) Refill the manua l gnr with the recommended oil to S.A.E.90.

T e.lille The quick test consistS of connccting

the un;1 to th" I·ehicle pump by the usual supply and return pipes and blocking off tbe tWO oulk t, from Ihc valve box which ne usu~Jly connected to the twO ends of the cylinder. Connect a p re~$u re gauge in the pip: between Ihe outlet from !he flow control va lye and rhe c~nneclion 10 ti,e stening valve box. FIll Ihe unit th rough the reservoir with the specified hydt:lulic oil 10 S.A.E. 10 (W) and wi!h the pump (\Inning turn Ihe steeriog wheel once or twice from lock 10 lock 10 ClIpel tbe ai r. Top up lhe reservoir as necClury.

When the SYSI~m is full of oil and Ihe eoginc idlmg so Ihar the pump run~ 3S slowly as pOSsible, turn the stee ring wheel 10 onc lock when efron is Ihen applied 10

the \\"Md Ihe pressure in Ihe supply pipe should build up 10 at least 650lbfsq ill. ApVI~ th is ttSt at bolh locks. This telr may be applied with the cylinder con­nected in the hydraulic circuit instead of a temporary connKting pip~.

The full test '$ more elaborate and Jlso tall for in lernal leakage and back prCSSut." at highn lempcraturcs. This tCSI 11 cJrri~ out with a special tCSI un it .