motorcycles and sidecars 6. frame parts chapt. vi....

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Motorcycles and Sidecars 6. FRAME PARTS

Chapt. VI. Design, Construction of Frame Parts.The Motorcycle Frame Structure -Foot-boards -

Rear Wheel Stands-Spring Forks-

Spring Supported Seat-posts-Spring Frames-

Saddles and Tandem Attachments-Coasting and Braking Hubs, Why Used

Requirements of Pedal Drive Mechanism-What Brakes Should Do-

Force Needed at Brake-

Principle of Brake Action-Friction Coefficient and Its Relation to Brake Design-

Leading Types of BrakesOperation of Typical Braking and Coasting Hub-

How Rider’s Effort Is Multiplied-Motorcycle Tires-Sidecar Advantages-Forms of Sidecars-Sidecar Attachment and ControlMethods of Starting Motorcycles-Electric Starting and Lighting System-

Motorcycle Control Methods-

Bowden Wire Control 347-426

We have discussed at some length, in a previouschapter, the various forms of motorcycle framesand methods of power plant support in a generalway. In view of the important, functions of theframe structure, it, may he well to describe thisimportant component upon which the strengthand endurance of the entire assembly dependsmore completely. A typical loop frame, such asused on the Indian motorcycle is shown at Fig.217, and this shows clearly all of the parts, withthe exception of the wheels and handlebars thatare generally considered as being part of theframe assembly.

It will be observed that in certain essential re-spects this frame differs materially from thoseused in bicycle construction. The looped memberthat supports the motor, the drop at the seat-postmast, and the elimination of the usual diamondconstruction at the rear end are all radical depar-tures from bicycle frame design.

In this construction, the effort is made not only tosuspend the weight of the rider by resilient mem-bers other than pneumatic tires but by the use ofthe laminated leaf spring fork and the distinctivedouble cradle spring rear construction, the entireweight of the power plant and its auxiliaries aswell as the rider are spring supported and pro-tected from the undesirable influences of roadshock.

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The complete frame assemblyconsists of the main framemember to which are attachedthe front fork at the steeringhead, a saddle over the seat-post tube, a luggage carrier,chainguard, mudguard, andsuitable stand at the rear end.

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The frame shown at Fig. 218 isrepresentative of the form ofconstruction in which the motorbase is depended on to join theopen portion of the frame whenthe power plant is in place.

The important parts of this as-sembly are also clearly outlined.

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The frame at Fig. 219 is a loopdesign of merit, and shows thecomplete frame assembly minusthe rear wheel. The motor sup-ports are brazed to the frame loopand are in the form of brackets towhich the lugs attached to the

engine base are bolted. Attentionis directed to the distinctive meth-od of strengthening the rear endby means of vertical brace tubesthat join the rear forks and rear-fork stays together. The form ofthe mudguards, the design of the

saddle and handlebars, and themethod of housing the tool com-partment under the saddle, in thespace between the seat-post mastand the rear mudguards are alsoclearly depicted.

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Another open frame is shown atFig. 220. This differs from thatpreviously described, in that themotor casing is secured to an

extension of the crank-hangerby two bolts, and to the end ofthe diagonal tube with one bolt.

Both of these members areforked so it is a simple matter toremove the power plant from theframe when necessary.

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A motorcycle frame is generallybuilt up of seamless steel tub-ing, though sonic designs havebeen evolved in which a portionof the frame is composed of acasting member to which the

tubes were attached. The framesillustrated at Figs. 217 to 220are of the pattern in which thevarious fittings are joined to-gether by steel tubes. The Se-hickel frame which is depicted

at Fig. 221 is a distinctive con-struction be cause the mainportion of the frame is a largealuminum casting which servesas a fuel container.

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The steering head and a portionof the seat-post tube retainingmember are formed integrallywith it. Another suitable project-ing boss is employed to supportthe front diagonal tube.

The rear fork assembly is builtof tubing in the conventionalmanner. The Pierce motorcycleemploys a frame made of largediameter tubing, which mem-bers also serve as fuel and oilcontainers, and which provide aframe of exceptional strengththough unconventional in ap-pearance.

When motorcycles were first,made, light steel stamped rein-forcements of the form used inbicycle frame construction werewidely employed to hold thevarious parts of the motorcycleframe together.

At the present time, stampingshave been discarded for moresubstantial drop forgings andmalleable iron castings. Thesteering head of practically allmotorcycles is in the form of aforging or semi-steel casting

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provided with a substantial ribjoining the two bosses to whichthe frame tubes are brazed. Theseat-post cluster is also a forg-ing and has four projectingbosses. One of these is intendedto secure the seat-post tube, theone at the front is for attachingthe upper frame member whilethe two at the rear form an an-chorage for the rear-fork tubes.The crank-hanger is still anoth-er member which varies accord-ing to the design of the frame towhich it is fitted.

The two common methods ofbrazing the frame tubes em-ployed differ in one essential.The fittings are joined to thetubing in some frames by beingpushed in the interior of thetube. This makes what is knownas a flush joint because no evi-dence of the point of juncturebetween the frame and the fit-ting is noticed.

The steering head forging of theIndian motorcycle, which isshown at. Fig. 222 has internalreinforcement or flush joints,while the steering head fitting of

the frame shown at Figs. 219and 220 is attached by insertingthe tube inside of projectingbosses that form part of thefitting. This method is oftencombined with an internal rein-

forcement and is said to bestronger, though not so neat, inappearance, than the flush jointframe construction. The latterhas survived from bicycle prac-tice where it was desirable to

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eliminate all corners in whichdirt, or dust could collect, andalso to have a smooth or fin-ished appearance for the frame.In a motorcycle, the factor ofstrength is the most. importantconsideration so that externallyreinforced joints are used fullyas much as the flush joint con-struction.

The tubing used in motorcycleconstruction is not only of heavygauge and of large diameter butis invariably provided with aninternal reinforcement which inmost cases is a vertical steelpiece running through the cen-ter of the tube. This reinforce-ment is shown at Fig. 222.

Another reinforcement which iseven stronger than the singlevertical member that bisects thetube into two D-shape or semi-circular sections is in the formof a triangular tube securelyattached to the interior of theround frame tube. This tubing isused on the Emblem motorcy-cle, and is shown at Fig. 223.

The sizes of tubing used de-pends upon the character of thereinforcement and the strengthit is desired to obtain in themotorcycle frame structure,which, of course, depends large-ly on the size of the power plantinstalled. A frame that mayappear light when viewed fromthe outside on account of usingtubing of small diameter mayactually be stronger and weighmore than a more substantiallooking frame of large diametertubing, because it would havethicker walls and perhaps amore substantial internal bracemember.

The accepted method of fasten-ing the frame components to-gether is by a combination ofpinning and brazing. When theframe is first assembled, it isplaced in an alining fixturewhich insures that all the tubeswill fit the various fittings towhich they are attached proper-ly, and that the center line of allthe tubes comprising the mainportions of the frame coincide.

The next operation is to fastenthe members together by drillingholes through the tube, andfitting and driving steel pinsthrough these to hold the mem-bers together so the frame maybe handled during the brazingoperation.

This process consists of heatingthe portion of the frame wherethe joint is to be made to a con-siderably higher point. than themelting point of the spelter em-ployed in joining the parts.

The frame tube and fittings areraised to just below a white heat,and the binding material, whichis a brass alloy in a molten condi-tion is poured in the minute openspace between the frame tubeanti fitting at the joint. A flux,consisting of borax, is mixed withthe spelter so it will flow readilybetween the tube and projectingmember to which it is attached.When the joint is allowed to cool,the two members are held togeth-er by a thin layer of brass whichforms a very strong joint that willgive absolutely no trouble if it hasbeen properly made.

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There is also a tendency in mod-ern motorcycle factories to usethe oxy-acetylene flame in weld-ing parts together, and this alsomakes a very strong joint. Theprocess of electric butt weldingor spot welding may also beused to advantage at variousportions of the frame structure.Brazing is the method generallyfollowed, because the process iswell known and has been highlydeveloped through many yearsof use in building bicycleframes.

After the frame structure hasbeen permanently assembledand all its components are heldfirmly together, the alining fix-ture is again brought into playand the frame straightened bysuitable clamps if it has beenknocked out of proper alinementby distortion due to the heat itwas subjected to during thebrazing process. After this, theframes are thoroughly cleaned,and all of the protruding spelteror flux at the joints is chipped orfiled off. The frame tubes arethen polished and smoothed by

rapidly moving emery-coatedcloth belts preparatory to theapplication of the enamel.

The size of the tubing employedaverages about 1-1/8 inchesdiameter for the seat-post mastand the diagonal tube extendingfrom the steering head. Theupper and lower frame membersthat join the steering head tothe seat-post must and betweenthe scat-post mast are usuallyof 1-inch diameter tubing.

The rear forks and rear forkstays will be of 3/4-inch or 7/8-inch round tubing, thoughsometimes oval section tubemay be employed for the rearforks.

The front forks of most motorcy-cles are composed of oval sec-tion tubes which taper downfrom where it is brazed to thefork crown forging to the lowerportion designed to carry thewheel hub, or the links to whichthat member is secured.

Sometimes round tubing is usedfor front fork construction asshown at Fig. 218, though the

general practice is to use thetapered section, flat oval tube. Itis not considered good practiceto use tubing much thinnerthan 3/32-inch wall, and for themost part, even when it is wellreinforced, tubing with a 1/8-inch thick wall is used for theprincipal frame members, suchas the seat-post mast, the up-per frame tube and the motorsupporting loop member.

Foot BoardsThere is a growing tendency onthe part of motor cycle design-ers, which has been fosteredlargely by the demands of theriders, to provide auxiliary foot-rests in addition to the usualpedals that have been used onmotorcycles from the first.

Footrests were first used onforeign machines, many ofwhich have entirely discardedthe pedaling cranks so widelyused in this country.

As these members are replacedby a simple starting crank orkick starter on motorcycles

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employing variable speed gears,it is necessary to provide somemeans for supporting the rider’sfeet. Naturally the simplest waywas to braze extentions to theframe tube or attach footpads tothe power plant in some way.

Some of the examples of footsupports used on Americanmachines are shown in detailat Fig. 224.

That at the top is the riggingused on the Excelsior motorcy-cle. The footrests are steel dropforgings of approximately thesize of the average foot that arecarried by a substantial auxil-iary bracket member securedat its lower ends to one of thecrankcase bolts and at its up-per end to the diagonal frametube by a substantial clip com-posed of two steel stampingsheld together by through bolts.

The footrests are attached tosuitable extensions by a hingethat permits of folding them upout of the way or to provide asafeguard against breakingthem off or bending them,should the machine fall over.

With the Excelsior assembly, abrake-operating pedal is in-cluded in order that the ridermay work the brake as effec-

tively when his feet are on thefootrest as when they are onthe pedal crank. The simpleform shown in the lower left

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hand corner is used on the Schick-el motorcycle, and consists of twosimple cast aluminum membersattached to a laminated leaf springthat is intended to provide a resil-ient support for the feet of the rider.

The Iver-Johnson footrest alsodepicted at Fig. 224 is a folding typethat offers a secure support for therider’s feet. It is carried by twohinges from a stamped steel mem-ber anchored to the frame.

In some machines, notably theHenderson and the two-speedIndian, the foot-boards are depend-ed on entirely to support the feet ofthe rider, and no pedals are provid-ed.

There seems to be a tendencytoward the elimination of the pedal-ing gear that has for so long been afeature of bicycles and motorcycles,and while it was formerly an essen-tial part of the machine on the earlytypes without two-speed gears orfree engine clutches and equippedwith power plants of low rating, it isno longer necessary to assist themotor up a hill by vigorous pedalingor to constantly restart the motorafter stopping it in traffic.

The free engine clutch makes itpossible for the rider to control hismachine, and to bring it to a stopwithout affecting the motor, and thevariable speed gear makes it possi-ble to overcome all adverse condi-tions by the power of the motoralone. For this reason there issome talk about the elimination ofthe pedaling gear, and the substitu-tion of footrests and suitable con-trolling levers that will permit ofpositive motorcycle control.

There is considerable to be said infavor of the pedaling gear, however,and its value is clearly establishedin the mind of the rider who hastried to start a stiff motor on a coldday by a more or less positive kickstarter which does not, permit ofspinning the motor, as is possiblewhen the effort of the rider can heapplied with both feet through asubstantial chain and crank to therear wheel of the machine, which inturn rotates the motor crankshaftvery briskly through the drivinggearing, and which induces anobstinate motor to start even whenit is difficult to vaporize the gaso-line.

Another feature is that brisk pedal-ing produces a hot spark at thespark plug, because the currentproduction from the magneto is ofmore value when that member isrotated briskly. While it is thor-oughly practical to start a four-cylinder motor by a starting crank,it is conceded that it is more diffi-cult to start a single cylinder to twinmotor with a starting handle, un-less conditions are favorable.

The writer believes that the pedal-ing gear is a desirable fitting, be-cause it provides a means of sup-porting the rider’s limbs when theybecome cramped from maintaininga constant position on the footrest.

Pedals also permit of considerablymore comfortable riding on roughroads than footrests do, because itis possible for the rider to re-lieve the saddle of his weightwhen running on rough groundby using the pedals for support.They are also valuable in provid-ing a positive control of thebraking and coasting hub whichforms an essential part of manyAmerican motorcycles of moderndesign.

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Rear Wheel StandsThe motorcyclist of today is fortunate inhaving many devices included as stan-dard equipment on the motorcycle hepurchases, that had to be bought as anaccessory or that could not be obtainedat any price with the early machines.

No motorcycle sold at the present timewould be considered complete withoutan integral stand by which the rearwheel can be raised from the groundand the machine kept, upright whenleft, by the rider.

It is not more than six years ago thatthe portable stand which is now consid-ered indispensable was unknown. If itwas necessary to stand the machine up,it had to be leaned against some wall ortree which did not always prove to be assecure a backing as the rider wished,because the machine might slip from itsupright position, and when the riderreturned to his mount he was just asapt to find it lying on its side as in theupright position that he left it in. If itwas necessary to raise the rear wheelfrom the ground, as in changing a tireor in making adjustments to the brakeor hub, considerable ingenuity was

Fig 225 Indian Rear Wheel Stand

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necessary to improvise a suit-able support for the rear endfrom a couple of boxes, oddsand ends of boards, or evenpiles of bricks.

It is said that the first stand wasoffered by the Hendee Manufac-turing Company for use in con-nection with the Indian motorcy-cles, during the early part of1908. This consisted of twoseparate supporting members orlegs fitted with clamps designedfor attachment to the rear forkstays and hinged so the legsection could be folded up andaway from the ground when thedevice was not in use.

While this was a big improve-ment, it had the grave defectthat it could not be used verywell on soft ground, as the limit-ed amount of contact at thelower portion of the legs wouldpermit one or the other to settleinto the earth, and either allowthe machine to fall over orwould permit the rear wheel tireto drag against the ground whenthe motorcycle was being tunedup on the stand.

At the present time, the standsare made with a cross piece atthe bottom, which not onlyserves as a reinforcement butwhich provides an added meansof support on soft ground.

A motorcycle stand must be

light, strong and rigid. It mustbe applied so it can be swunginto place easily and securelyfastened out of the way whennot in use.

The stand at Fig. 225 is a tubularconstruction employed on the

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Indian motorcycle. It is hinged at itsupper end to the slotted platemember or rear hub carrier at thepoint of intersection between therear forks and rear fork stays. Twoarms or projecting members of Tsection are brazed to the standtubes, and are of such form thatthey will rest against suitable stopson the frame.

The stand at Fig. 226 is that usedon the Eagle, and is an automatictype. Instead of tubing, channelsection steel with substantial brac-ing members and forged arms isemployed. The arms have a forkend at their upper portion thatrests against; the frame tube whenthe stand is in its operative posi-tion. A pair of tension springs areprovided to return the stand to theposition it occupies when not inuse, automatically as the motorcy-cle is pushed off of the stand.

The springs draw the member intothe stand retaining dip in the formof a piece of spring steel securelyriveted to the lower portion of therear mud guard. The front, wheelstand which forms an item ofequipment, on many European

machines and which has beenpreviously illustrated is not. sup-plied as a standard fitting onany of the American types,

though some have been fitted totheir machines by experiencedriders familiar with the advan-tages obtained through its use.

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Fig. 228 - Spring Case of Reading-StandardSpring Forks - shows Load Carrying &Recoil Check Springs

Spring ForksOne of the first concessions made forthe comfort of the rider was the appli-cation of a resilient support, for thefront end of the frame in order that theshock incidental to operation overrough roads would be taken by springsinstead of transmitted directly to thehandlebars of the machine. This jarringpromoted fatigue because of the shocksthe rider’s arms received.

Even the earlier forms of saddles werecomfortable, inasmuch as they wereprovided with fairly resilient, springs orwere well padded, so the attention ofthe designer was directed first to springfork development on account of thecomplaints of the riders of the vibrationat the handle bars. Spring forks havebeen made in infinite variety, thoughthe object of all designers is to obtainthe resilient feature without sacrificingstrength unduly.

Two types of springs have been utilizedto take the shock imposed on the frontwheels.

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Fig 229 Leaf Spring on Eagle MC toControl Movable Fork Member

When coil springs are employed they areusually housed in casings of tubularform, though with leaf spring the resil-ient member is necessarily exposed.

The fork used on the Yale motorcycle isshown at Fig. 227. It consists of twomembers, a fixed fork attached to thesteering head in the usual way, and amovable fork.

An extension piece carried from thefixed fork is mounted between springsat the upper end of the movable mem-ber, while the lower portion is attachedat. the center of the hub carrying linkmembers. These are attached to thewheel hubs at one end and fulcrum onsuitable bearing studs attached to thefixed fork end at the other.

When the wheel encounters an obstacle,the hub carrying link will move on thesupporting bearing, and will force themovable member upward. This motionis resisted by the extension forming partof the fixed fork and by a spring carriedbelow the extension in the upper por-tion of the movable fork tube.

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Another spring is mountedabove the extension in order toprevent rapid rebound.

The sectional view of the springfork used on the Reading-Stan-dard shown at Fig. 228 showsanother application of the spiralspring principle.

The movable fork member isattached to the hub carryinglinks in the same manner as.previously described, and car-ries two spring members insideof a movable spring case whichis guided by a fixed spring caseattached to the upper portion ofthe steering head.

The shock absorbing and recoilcheck springs are clearly shownand both arc thoroughly en-cased and protected inside ofthe spring casing.

The application of the laminatedspring to secure resilient wheelsupport was first tried out on theMarsh-Metz motorcycles, and hasbeen retained on the modernproduct manufactured by theseinterests which is known as the“Eagle” motorcycle.

This construction is clearlyshown at Fig. 220. The fronthub is carried by links whichfulcrum on suitable bearings atthe end of the fixed fork assem-bly. Attached to the plate thattakes the place of the usual forkcrown is a six leaf spring, andfrom the eye at the forward endof this member a movable forkmember composed of two steelrods passes to the front hubcarrier.

As the wheel is moved by irregu-larities on the road surface, it isapparent that, the leaf springwill be raised and that theshock will be absorbed in thismanner.

The cradle spring fork which is animportant feature of design on theIndian motorcycles is shown atFig. 230. The advantages claimedfor this type of spring includemaximum flexibility, which is saidto be produced by the curved endof the lower leaves, and the quickdampening of the oscillations orabsorbtion of rebound due to thefriction between the spring leaves.

The spring fork of the Indianmotorcycle is of the trailing type,which means that the hub axlefollows the forks instead of hav-ing the hub mounted ahead ofthe fork as is also commonpractice.

The advantage of the trailinghub is not as clearly realized asit should be. With the forms inwhich the hub is carried aheadof the fork, when the wheel israised, it is apt to produce anupward movement of the entirefront end of the machine be-cause a certain portion of theshock is transmitted by the hubcarrier link directly to the fixedfork members as the wheel sur-mounts the obstacle.

With the trailing hub construc-tion, which is clearly outlined atFig. 230, any movement of thewheel will affect only the shockabsorbing spring.

The advantage of the trailinghub construction may be readilygrasped by comparing its actionto that of a wheelbarrow when itpasses over a raised object. If a

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Fig 230 Indian Cradle Spring Fork

wheelbarrow is pushed againsta curb, for instance, it will befound difficult to force it overthe obstruction, whereas if it ispulled over it will surmount ahigh curb with comparativelylittle effort on the part of theperson wheeling it. The usualmethod of supporting the frontwheel ahead of the fork may belikened to pushing a wheelbar-row over; the trailing hub actionis the same as when it is pulledover the obstruction.

The fixed fork member of theIndian machine is well bracedby a. tubular arch member ex-tending from the top of thesteering column to the lowerportion of the fixed fork. Thehub carrier links are attached attheir front end to the fixed forks,carry the wheel hub at theircenter, and the movable forks atthe back end. The curved lowerleaf of the shock absorbingspring provides a certain degreeof flexibility which makes thewheel respond to slight irregu-larities of the road surface, and

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when greater resistance is en-countered the entire spring isbrought in action because themovable fork member exerts itspressure against the lower leafat a point calculated to bringthe remainder of the springleaves in action.

The foreign spring forks varyfrom the American designs, andthe preference seems to be forcoil springs as shock absorbingmembers, which are invariablyexposed. A number of typicalEnglish spring forks are shownat Fig. 231. In the member out-lined at A, the wheel is carriedin a substantial movable forkmember, that, is secured to themember passing through thesteering head by means of dis-tance links which permit a cer-tain amount of up and downmotion, but which do not allowthe wheel to move backwardappreciably.

In most American designs, thewheel may move backward aswell as up and down. At thelower portion of the piece pass-ing through the steering head a

pair of spiral springs are mount-ed which are attached at theirlower ends to extensions brazedto the fork tube.

When the wheel meets an ob-struction, its upward motion isresisted by the springs whichare under compression whilethe violent rebound is checkedby the tension resistance of thespring. in the form shown at B,the fixed fork member is ful-crumed on a pair of links whichare attached to the piece pass-ing through the steering head.

The shock absorbing spring isalso secured to the steeringhead member and resists up-ward motion or vertical travel ofthe fork member, which canmove in that plane as the dis-tance links oscillate on theirbearings. The upward motion isresisted by the upper coil springwhile the recoil is checked by asuitable member at the lowerpart of the steering head. Bothsprings are under compression.

Another form which is very simi-lar to the American design

depicted at Fig. 228, withoutenclosed springs, is shown at C.In this, the lower of the twosprings is a compression mem-ber that is provided to absorbthe shock, while the shorter ofthe two or upper spring is usedto check the recoil.

The hub in this construction iscarried in a movable fork mem-ber which is kept in proper rela-tion with the fixed fork by suit-able distance links. A point thatshould be noted by the reader isthe system of applying a pair ofbrakes that act against the frontwheel rim on all three of theforks shown at Fig. 231.

This brake is actuated throughthe medium of Bowden wirecontrol running to a suitablehandle on the steering bar. TheU-shape member carrying thebrake blocks or contact shoes isguided at its lower ends by clipssecured to the fork side, while itis steadied at the upper end bya bearing through which thewire or a lifting rod passes.

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Fig 232 Spring Supported Seat Post of theReading-Standard Motorcycle

Spring Supported Seat PostAfter the springing of the front end hasbeen satisfactorily accomplished by theuse of spring forks some of the designersbegan to consider the best method of elimi-nating the jar at the rear end of the ma-chine. Some of the manufacturers haveadopted a resilient frame construction withthe idea that this would suspend the powerplant on springs, as well as the rider. Oth-er makers contend that the spring sup-ported saddle coupled with a resilientspring fork is all that is needed to insurecomfort of the rider, and reduction ofshock on the machine.

The spring seat post attachment employedon the Reading-Standard motorcycle hasdemonstrated its efficiency and is verysimple. As is true of the spring fork previ-ously described, the resilient support ofthe saddle is attained by the use of coilsprings protected by and housed in a tu-bular housing hinged at its lower portionjust forward of the pedal crank hanger,and maintained in proper position at theupper end with a movable distance mem-ber or link.

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Fig 233 - Spring Seat Post used on the EagleMotorcycle

The seat post is extended to form aplunger that is guided by a suitablehearing at the upper end of the springhousing. The long coil spring is the loadcarrying member, while the shorterspring at the upper end is a recoil check.Another feature that tends to prevent toorapid movement of the seat post is thefriction shock-absorbing hinge by whichthe movable link is held to the scat posttube.

The spring seat post used on the Eaglemotorcycle, and illustrated at Fig. 233, issimilar in construction to that just de-scribed, though it is different in detailand application. The seat post is hingedat its upper end to a clip attached to theupper frame tube. It is adapted to bearon a plunger member that projectsthrough the seat post tube, which alsoserves to house the load-carrying andrecoil spring.

A simple application of a spring-supportedseat post is shown at Fig. 234. The forwardend of the seat post is hinged to the frame,while the rear end is secured to a conicalspring that bears on a supporting memberattached to the rear fork.

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The method of mount-ing the saddle on theYale motorcycle, shownat Fig. 235, is similarexcept that two springsare used, one at eitherside of the seat posttube in supporting thesaddle. These are coilsprings and are intend-ed to supplement theaction of the memberswith which the saddleitself is provided.

Another application of aspring seat post is shownat Fig. 236, as applied tothe Fielbach motorcycle.The saddle supportingmember is in the form ofa bell crank, the longarm of which carries thesaddle, while the shortarm is attached to aplunger that worksthrough the lower of thetwo upper frame tubeswhich serves as a hous-ing to retain the load-carrying and recoil-ab-sorbing members.

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Spring FramesThere is a marked distinctionbetween spring scat. posts andspring frames, and this is wellshown by comparing the twodifferent methods shown at Fig.237. That at A is a simple springframe, which means that theweight of the rider is carried bya frame which in itself is capa-ble of movement, and that thesame frame to which the powerplant is secured also directlysupports the weight of the rider.

The rear hub of the Pope motor-cycle is mounted in simple forgedyokes that are guided by plungersextending through bosses at theend of the U-shape bracketsattached at the rear of the frame.The heavy coil springs are undertension and the tendency of theupward movement of the rearwheel when it strikes an obstruc-tion is to extend rather than com-press them. The spring supportedseat-post representative of theother construction, shown at Fig.237, B, also includes a coil springunder tension.

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Fig 238 Indian Chief Spring Frame

The seat post is guided by dis-tance links, one end of thespring being attached to theframe, while the lower end issecured to the movable seat-post member.

The cradle spring frame utilizedon the Indian motorcycle is con-ceded to be one of the biggeststeps forward ever made in thedevelopment of the motorcycleframe. The construction is notunlike that of the spring forkexcept that two load-carryingsprings are used, one at eachside of the wheel.

The wheel hub is carried in amovable rear fork stay hinged atits forward end to the lowerportion of the tube that takesthe place of the seat-post mast,of conventional design frames.The load-carrying springs areattached to a semi-steel castingmember in the form of a horse-shoe that takes the place of theusual seat-post cluster.

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A movable rear fork member isattached to the springs in thesame manner as the movablefork member of the spring forkassembly is, and is hinged at itslower portion to the hub-carry-ing plates.

It will be evident that with thisconstruction the rear wheel maymove independently of the mainportion of the frame that carriesthe weight of the rider and thepower plant, and that the combi-nation of this member with theeffective spring fork should notonly provide for maximum com-fort of the rider but contributematerially to the long life andendurance of the mechanism byinsulating it from the destructiveroad shocks in a much superiormanner to that which obtains inthe conventional constructionwhere the air-filled tire is the onlyresilient support.

Two spring frame constructionsin which coil springs are usedare shown at Fig. 239. That at Ais the form used on the Merkel,and has been a feature of thismachine for several years.

The rear portion of the frame,which is comprised of the forksand rear-fork stays, operates inthe same manner as the springforks in which the enclosed coilsprings are used. The rear-forkstay members are employed tohouse the coil springs, whilethe front end of the fork as-

sembly is hinged to the crankhanger in order to permit freemovement, of the rear portionof the frame.

The method of incorporating aheavy compression spring inthe frame of the N. S. U. mo-torcycle, a foreign design, isshown at Fig. 239, B.

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The application of ‘four laminat-ed leaf springs to support therear wheel of an English four-cylinder motorcycle employingworm drive is shown at Fig. 240.

In view of what has been pre-sented before, and the completeexplanations that have beengiven of spring fork and springframe action, the method ofoperation of these various formsshould be clearly grasped.

Saddles and TandemAttachmentsThe first motorcycle includedpractically all the parts of thebicycle without much change andit was some time before some ofthe parts were .altered or en-larged, even after considerableimprovement had been made inmotor design and in the construc-tion of the mechanism.

One of the fittings that was notchanged for several years be-cause the designers had all theycould do to make the mecha-nism reliable was the support orsaddle for the rider. The saddles

that had been used in bicycleswere of simple form, usuallyconsisting of a light wooden orsteel frame covered with leather;in some cases a padding would

be interposed between theleather covering and the base.Bicycle saddles were narrow,and they were very satisfactoryon those machines where the

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riders weight was distributed tosome extent, on the crank hang-er through the efforts made andpressure applied to the pedalsto propel the vehicle.

With the motorcycle, the riderdid not have to pedal any morethan was necessary to start themachine, which meant thatpractically all of his weightwould rest on the saddle.

Several forms of bicycle saddleswere made that provided a widesupport, but it was found thatthese materially interfered withthe effective action of the rider’slimbs when pedaling. This ob-jection did not obtain in themotorcycle and the saddles weregradually increased in size, bothin length and in width, until theforms used today provide asecure and comfortable seat.

It was not desirable to have a veryresilient saddle on a bicycle be-cause the spring detracted some-what from the effectiveness of thepedaling. On a motorcycle, how-ever, it was soon learned that itwas much more uncomfortable tosit on an inflexible non-yielding

seat on a machine going 35 or 40miles an hour than was the casewhen traveling but one-third thatspeed on a bicycle. The saddlemanufacturer was not slow indevising wide seats that wereprovided with substantial springmembers in order to make themeasy riding.

Two modern saddles are shown atFig. 241. That at A consists es-sentially of a metal frame overwhich a leather scat is placed, theleather being kept under tensionby the coil spring at the front end.This spring gives somewhat underthe rider’s weight, though themain reliance for easy riding is

upon the coil springs at the rearof the saddle. The form shown atB is similar in construction as faras the frame work is concerned,except that the seat is formed toconform to the anatomy of theaverage rider and has a paddedcushion interposed between theleather covering and the metalframe.

The arrangement of the springsused to support the rider in theusual motorcycle saddle as wellas the general construction ofthe form in which coil springsare used is clearly outlined atFig. 242, A.

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The metal frame work withthe leather coverings re-moved to show the ar-rangement, of the parts ofthe Persons ChampionSaddle is shown at Fig.243. Coil springs are notthe only type that havebeen adopted in saddleconstruction. A form inwhich leaf springs are usedto support the rider’sweight, is shown at Fig.242, B. Practically all sad-dles are provided with anadjustable clamp that per-mits of tilting the saddle tosome extent and moving itback and forth on the seatpost tube to adjust the seatmember for different buildsof riders.

While some of the earlymotorcycles were made ina tandem form, i.e., justthe same as the two-pas-senger bicycler except forthe addition of the powerplant, this form of con-struction is now aban-doned.

The reason for discarding thetandem was that the ma-chine was unwieldy and hardto handle if but one personwas riding. For this reason,tandem attachments thatwould convert the ordinaryform of one-passenger mo-torcycle so that two peoplecan be carried effectivelyhave been evolved.

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Fig 244 - Tandem Attachment

A typical tandem attachmentremoved from the machine isshown at Fig. 244, while asimilar device attached is de-picted at Fig. 245.

The tandem attachment in itssimplest form consists merelyof a supplementary rear forkmember carrying a pair of foot-rests or pedals at its lower end,and a saddle at the upper part.

A brace extends from the top ofthe fork to the seat, post clus-ter of the machine, and in mostcases this brace carries a pairof non-movable handle bars bywhich the passenger maysteady himself.

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Why Powerful Brakes areNecessaryIt is now generally concededby manufacturer and rideralike that the motorcycle oftoday is practically a two-wheeled automobile capableof speeds rarely attained bythe larger conveyance.

Engines used are rated atfrom 7 to 9 horsepower, andthese will usually developtwice their nominal rating.Larger motors call for heavierframes to carry them and therider safely, more powerfultransmission systems arefitted and spring frame andforks are also required toinsure comfortable riding athigh speeds over ordinaryroads.

All control elements must alsobe designed with a view ofgiving the rider positive mas-tery of the machine.

When one considers the mo-mentum it is possible to at-tain with a vehicle weighing,with average rider, nearly 100

pounds, and capable of a speed of75 miles per hour in many cases,the need of a positive retardingmember or brake can be properlyrealized.

Brakes designed primarily forbicycle service and increased insize without due regard to thestresses obtaining in motorcycles,cannot work adequately or proveenduring.

The brake as well as the otherparts of the machine must beincreased in size and capacity tocorrespond in efficiency to thelarger power plants now fitted.

The problem is therefore essential-ly one of automobile design, andcan only be solved by a correctapplication of motorcar engineer-ing principles.

Why Coasting, Driving andBraking Hub is UsedOne of the most important acces-sories developed for the bicycletrade, and one which has contrib-uted materially to the expansion ofthat business by promoting the

comfort and safety of the riderwas the coasting and brakinghub.

In this device, the motorcyclemanufacturer obtained a rearhub construction, already highlydeveloped, that was just as wellsuited in principle to motorcycleuse as it was to the bicycle,though applied in a slightlydifferent manner in bicycle ser-vice, it is provided to give therider an opportunity to stoppedaling on down grades orsmooth roads with favoringwinds, and yet permits him tokeep control of the bicycle, be-cause a slight back pedal actionapplied a brake to the wheel.

On a motor-propelled cycle themotor does the driving normally,and the pedals are only broughtin action when it is desired topropel the machine by foot pow-er to start the motor. As soon asthe engine starts, the coastingfeature comes into play, and theaction is just the same asthough the rider of a foot-pro-pelled cycle was taking advan-tage of down grade. The pedals

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provide a rest for the feet, andthe back pedaling or reversepressure begins to bring thebrake in action any time it isnecessary to retard the speed ofthe machine.

The rear sprocket of a chain-drive machine is attached di-rectly to the hub shell, the beltpulley, if that system of trans-mission is used, can be securedto wheel rim or to hub shell, asdesired.

The only difference in principlebetween a coaster hub intendedfor motorcycle work and the simi-lar device made for bicycles isthat two methods of driving therear wheel are provided, one bymechanical power to a memberrigidly secured to the hub shell,the other by foot power throughthe medium of a friction clutchthat automatically engages thehub shell interior as soon as thepedals are pushed forward.

Requirements of PedalDrive MechanismThe requirements of the pedaldrive mechanism are well knownat the present time, and thatemployed has demonstrated itscorrectness in theory andpractical application by years ofactual use in millions of bicycles.

The basic principle of the spiral-ly threaded member and lateral-ly shiftable connector to drivethe hub, declutch to provide afree wheel and to apply thebrake by further movement hasbeen developed in this countryto a state of practical perfection.

The best argument in favor ofthis pedal drive mechanism isthat a simple and successfulcoaster brake cannot be builtwithout incorporating this sys-tem, and that all devices on themarket embody this principle.

The construction is such thatthe hub is driven smoothly andpositively whenever the pedalsare rotated forward, the hub isfree to rotate independently of

the pedal drive sprocket as soonas the feet cease rotating and a.reverse motion of the pedals orback pedaling action will applythe brake without slipping.

Coaster brakes have been madewith ratchets, ball or roll clutch-es, etc., but these have not beenas successful, reliable or endur-ing as the double taper coneprinciple of driving and brakeactuation universally applied.

What Brake End Should DoWhile the requirements of thepedal drive mechanism werewell understood, the principlesmaking for efficient brake actionof motorcycle hubs were notrealized so completely, and it ison this portion of the mecha-nism that most manufacturersdisagree.

To begin with, the essentialrequirement, is that the brakemember be capable of retardingthe cycle velocity to any degreefrom a simple and momentaryslowing down to a quick, emer-gency stop.

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This condition is not hard tomeet, almost any form of brakewill do it, when new, clean andin proper adjustment. The suc-cessful and really practicalbrake must be one that willprovide this essential promptbraking action but it must do itin a gradual manner, because aharsh acting brake will imposeinjurious stresses in the entiremechanism of brake and relatedwheel and frame parts.

The practical brake should be aform that will not need constantadjustment, the essential mech-anism should be thoroughlyprotected from the abradinginfluence of road dirt, the brakemember should be housed inand supported in a manner thatwill preclude liability of rattling.The brake parts should be ofmaterial that will not only havea high degree of resistance towear in service, but the mem-bers that come in contact toprovide the braking actionshould also have a high degreeof frictional adhesion because itis the absorption of power by

the frictional contact that re-tards the momentum of themachine.

The design of the brake endshould be such that the partswill not drag or tend to engageeach other when the brake isreleased, and the arrangementof braking members should besuch as to provide immediatecessation of braking effort assoon as the pressure exerted bythe rider on the actuating mem-bers ceases.

While the brake should be easyto apply so the maximum brak-ing effect will be obtained with-out too much effort on the partof the rider, at the same time,the brake should not be so sen-sitive that it can be appliedinadvertently through uncon-scious back pedaling. The abilityof the brake end to functionproperly even though floodedwith the oil or grease used inlubricating the hub bearingsand interior mechanism is alsoessential.

Let us carefully consider the forceneeded to afford positive controlof the modern motorcycle, thenbecome familiar with the principleof braking action, and a carefulanalysis of the construction ofvarious types of brakes will per-mit the rider to form his ownconclusions regarding the typethat best meets all of the require-ments previously enumerated.

Force Required at BrakeThe most any brake can do is toskid the wheel to which it isapplied. If it can accomplishthis, it is adequate to cope withany of the normal operatingconditions. The amount of forceneeded to lock the wheel de-pends upon the amount of thetotal weight of the machinesupported by the wheel to whichthe braking effort is applied,and the relative diameters ofwheel and brake member.

Much less force will be neededto stop a wheel if the brake isapplied near the tire than if itacts near the axle.

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Structural limitations make itnecessary to locate the brake inthe hub so it can be actuatedpositively by back pedalingmechanism that will be entirelyprotected and properly lubricat-ed but at, the same time it ispossible to follow automobilepractice and provide a drum forthe brake to act against, thatwill be of such diameter that thewheel may be controlled withouttoo much exertion on the part ofthe rider, or producing unduestress on the brake members.

Assume that the machine weare to stop is a powerful twinweighing 250 pounds with tan-dem attachment and carrying apassenger load of 300 pounds,that being the weight of twoaverage riders. This makes atotal of 550 pounds, and we canjustly assume that 450 poundswill be supported by the rearwheel. The amount of adhesionbetween the tire and the groundis generally taken as 60 per centof the weight on the wheel, sowe will have traction enough soa retarding force must be ap-

plied at the brake drum equiva-lent to the adhesive force of 270pounds at point of contact be-tween wheel tire and theground.

If the wheel is 28 inches in di-ameter, it will have a radius of14 inches. The moment at theaxle center due to the leveragefactor would be the adhesivepressure times wheel radiuswhich would give a value of3,780 inch pounds at 1 inchfrom wheel center.

If the brake had an effectivediameter of but 3 inches, aswould be the case if it. was car-ried in the hub shell, we wouldbe forced to apply a retardingeffect of 2,520 pounds to lockthe wheel.

With a brake drum 6 inches indiameter, it would take only1,260 pounds retarding force toskid the wheel. If a brake blockwas applied directly to the tire,it would take but 270 poundsadhesive force, or the sameamount as maintains traction,to stop the driving member.

It will be apparent that the larg-er diameter brake membersrequire less effort to stop thewheel than those forms in whichthe braking effect is exertednear the axle. This use of a largebrake drum not only makes foreasier brake operation on thepart of the rider but conduces tolonger life of the parts becauseof the lessened stresses on thebrake anchorage members andalso lower unit stress on thematerials in contact.

While it is very desirable to havea compact brake assembly, stillit is more important to use therequisite proportions that willinsure positive braking under allconditions even if compactnessand lightness are sacrificed bymaking the brake drum andbrake shoes of adequate diame-ter, and all parts heavy enoughso they will have an ample mar-gin of safety over the actualrequirements.

Where human life and safety areconcerned, it is best to err onthe safe side, and the additionof a few ounces of metal is

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sometimes all that is needed tomake a part of doubtful strengthone with a large enough marginto guard against the weakeninginfluence of hidden flaws orinsure against breakage whensubjected to abnormal stress.

At the other hand, the brakeparts require careful designingto keep the weight down andretain strength, and materials ofconstruction must be selectedintelligently to insure absolutereliability and endurance.

Principle of Brake ActionThe friction form of brake is thatgenerally applied to all forms ofvehicles. The principle of actionmay be concisely expressed bysaying that if a fixed member isbrought to hear against a rotat-ing one, the friction betweenthem will bring the one iii mo-tion to a stop.

The time needed to stop a rotat-ing body depends entirely uponthe amount of friction presentbetween the braking members.This in turn depends upon the

coefficient of friction existing,which varies with the nature ofthe materials in contact, theeffective diameter of the brakemembers and the pressureholding the parts together. Wehave seen why large diametersare more desirable than smallones.

The amount of surface in thebrake is not as important aseffective diameter, because thebraking effort depends primarilyupon the diameter of the surfac-es rather than their width.

For example, there would be nodifference in braking efficiencyas relates to retarding powerbetween a brake band 1/4 inchwide or 2 inches wide if thediameter was the same.

The wider brake band wouldprovide an important advantageof having greater life becausethe braking pressure would bedistributed over a larger area. Itwould not be any more effectiveas a brake, however, than thenarrower member. It is generallybelieved that braking power

depends upon the surface incontact, but this is not true.

A brake of small diameter mighthave three times the surface ofone of twice the diameter, yetthe one with lesser surfacewould be twice as effective as abrake. The capable designer willalways endeavor to provide sur-face enough to prevent unduedepreciation, and will employmaterials in contact that willhave a high degree of resistanceto deformation.

In some forms of brakes, howev-er, the large amount of surfaceprovided is an actual detrimentto efficient brake action andserves no useful purpose.

The materials employed forbrake depend largely upon thedesign, and in every case theseshould be chosen with two con-siderations in mind, the mostimportant being the enduranceof the material and ability tokeep its shape under pressureas well as high degree of resis-tance to abrasion.

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The material should not be affect-ed by the heat generated whenthe brake is used, nor should itbecome decomposed or its effi-ciency reduced materially by oildeposits. Another consideration,but one of secondary importance,if it calls for the sacrifice of thequalities previously enumerated,is to employ sub-stances having ahigh degree of frictional adhesion.

Friction Coefficient ofVarious MaterialsIn brake design, engineers mustseek to increase friction, where-as in bearing construction ev-ery effort is made to reduce it.

The following brief notes on thecharacteristics of friction and adefinition of the meaning offriction coefficient will permiteven the reader not thoroughlyposted on mechanical subjectsto understand clearly what ismeant when the terms are used.

Friction acts on all matter inmotion, and is present as aretarding influence that requires

expenditure of power to over-come. As a rule, augmenting thepressure will increase the fric-tion, while lessening the loadwill reduce it.

Friction increases with the ronghn sof surfaces in contact and decreas-es as they become smoother. Fric-tion tends to bring everything inmotion to a state of rest, and, in sodoing, mechanical energy is con-verted into heat which is dissipatedand lost.

A simple experiment to showwhat coefficient of frictionmeans can be made by anyone.This consists of drawing a blockof iron or other metal across awood table top by means ofweights suspended by a cordpassing over a pulley at the edgeof the table, and then attachedto the block, in order to avoid asharp bend and eliminate lostenergy as much as possible.

Assuming the , block is smooth,also the surface of the table, thefirst trial can be made with thesurfaces absolutely dry.

Weights are added to the corduntil enough have been placedthereon to move the block onthe table, The weight requiredto move the block divided bythe weight of the block will equalthe coefficient of friction forthose surfaces.

If the bock of metal weighs 50pounds, and the amount of weightnecessary to move it is 25pounds, the coefficient of frictionis 25 divided by 50, or 0.50.

If the surface of the table isgreased with tallow, and theunder surface of the blockcovered with oil, it will befound that considerably lessweight will be needed to movethe block, proving that thefriction has been reduced bylubrication.

This explains why it is desirableto lubricate bearings, whereason first thought it would seemthat, the best braking effort;would occur between perfectlydry materials.

It would also appear that thesofter and rougher materials

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which have greater frictionwould be better for brake con-struction than hard and smoothones. This would be true if brak-ing effect was all that was to belooked for, and if the factors ofgradual application of retardingforce and endurance of brakemembers could be disregarded.

As it is important that deprecia-tion be reduced to a minimum,and that all shock should beavoided when braking, one cansee a logical reason for the use ofmaterials that would have lessfriction adhesion though greaterresistance to wear, and whichprovide smoother brake action.

The materials ordinarily usedfor brakes and their frictioncoefficients follow:

Asbestos Fabric on Dry Metal 0.30

Asbestos Fabric on Oily Metal 0.12

Metal to Dry Metal 0.15

Metal to Oily Metal 0.07

These values mean that if anasbestos fabric block or bandbears against a dry metal drum,less than one-third or 30 per

cent of the pressure maintainingthe parts in engagement will beavailable for stopping brakedrum rotation.

If the asbestos fabric worksagainst an oily surface, the fric-tional adhesion or braking forceis reduced to but one-eighth ofthe pressure keeping the partstogether.

Asbestos fabric is a soft, yieldingmaterial that is very effective ifused as an external brake, butit is entirely unsuited for usewhere much oil is present.

While it provides a gradualbraking action, it is not capableof withstanding as high unitpressures as metal, so a largersurface must be provided toinsure against untimely depreci-ation.

As it is a rough-surfaced materi-al that depreciates as used,constant, adjustment and re-newal will be necessary to keepthe brake in a satisfactory con-dition.

For this reason, this material isbetter adapted to external con-

stricting band brakes than toother forms, because it, can beeasily reached for adjustment,and it will be free from oil de-posits.

A metal is always used as onebrake member, usually therotating one, and sometimes itis used for both members, fixedas well as movable. While metaldoes not possess as much fric-tion as the asbestos fabrics, itdoes not depreciate throughaction of oil, and it can be usedwith higher unit pressures thanthe softer fabric.

The surface need not be so greatif the metals are properly select-ed. When used in motorcyclebrakes, the revolving metaldrum is usually harder than thefixed shoes or retarding mem-bers, and in all cases efforts aremade to use different metals incombination such as bronzeagainst steel.

The metals are much more en-during if lubricated, and the oilfilm serves to cushion the shockof braking by providing gradual

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Fig 246 - External ConstrictingBand Brake used on Harley-Davidson Belt Drive Model

application, as well as reducingthe liability of dragging or heat-ing, when brake members arereleased, should there be slightfrictional contact between them.Metal brake shoes or discs aretherefore better suited for internalbrakes than asbestos fabric facedbands, if there is as much oilpresent, as exists in motorcyclehubs.

Leading Types of BrakesThe most common forms ofbrake are the various band orshoe types, and the brakingmembers may act against, ei-ther the inner or outer drumperipheries.

The external band forms, shownat Figs. 246 to 248 inclusive,tighten around the drum, theinternal form as Fig. 249 expandsinside the drum or hub shell.

There is still another form ofexternal brake in which a fric-

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tion block bears against thewheel rim or the belt pulleywhen that method of driving isemployed.

The external band is usually aflat steel strip faced with asbes-tos fabric which is sometimesmade wedge shaped (Fig. 250)where it fits into the brake drumto provide greater frictionaladhesion.

The wedge-shape band offers animportant advantage, in that itprovides a positive grip, but ithas an equally great disadvan-tage in that it is apt to engagetoo suddenly, and then again it,may wedge in place so tightlythat the spring provided to re-lease it will not be effective, andit must be pried out of the V-groove in brake drum. The flatband provides more gradualbraking, and if made of properdiameter is amply effective.

The brake block form shown atFig. 252 has the fault that itcannot be easily operatedthrough the pedals, or incorpo-rated as a part of the hub. It is aseparate attachment that is

used in this country only foremergency brake service, beingcontrolled by a separate pedaldistinct from those utilized indriving the hub.

The external brakes have agreat disadvant age, inasmuchas they are exposed to dirt andcollect this matter which arts asall abrasive that promotes wearof friction material and drum.They are also liable to become

loose and rattle, and they allhave more small parts than thesimple internal shoe forms.

While these external brakes aregood, they are not ideal by anymeans, and if only one brakemember is fitted this should bepreferably of the internal form.A combination of two brakes,one internal and one external, isprovided on some machines, asshown at Fig. 251.

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The internal brakes are offeredin threes classifications. Theform using a pair of shoes ex-panded in a drum by a cans isthe most popular.

The internal ring form, in whichthe fixed member acts againstthe inside of the hub shell, is ata disadvantage on account of itssmall diameter and the greatwear due to the excessive pres-sure necessary to have it gripthe hub shell interior with suffi-cient force to stop the wheelpositively. These also are a formthat will nut release promptly atall times, and are likely to stickif applied too suddenly.

The multiple disc brake (Fig.255) is a form in which a largenumber of braking members areused, one-half being rotatablewith the hub shell, the othersbeing fixed to the axle.

Suitable mechanism is inter-posed between the pedals anddiscs so the brake elements arebrought together with consider-able degree of pressure. Thisform of brake, if copiously lubri-

cated, will provide smooth brakeapplication, and also offers alarge amount of frictional sur-face. It has the disadvantage ofnot always releasing promptly,because as the oil is squeezedfrom between the discs by thebraking pressure, the platestend to adhere together whenpressure is released because ofthe partial vacuum existingbetween them.

If lubrication is neglected, or ifthe brake is used for long peri-ods, as in mountainous sec-tions, there will be sufficientheat generated by the brakingfriction to cut or roughen thediscs, and even to actually de-form them.

Under such conditions, thebrake becomes harsh in action,no matter how much oil is used,

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and will also drag even whenreleased because the roughsurfaces have myriads of micro-scopic projections that tend tointerlock as the movable discsrevolve by the fixed members.

The internal brake in which bronzeshoes of ample size are broughtinto engagement with a hardenedsteel drum interior offers a largenumber of advantages.

To enumerate these briefly, wehave:

First, utmost simplicity;

second, strong parts;third, high retarding power;

fourth, freedom from dragging;fifth, efficient braking with oil

between the surfaces;

sixth, gradual or immediatebrake application as desired;

seventh, all brake parts lubri-cated and kept cleats;

eighth, complete enclosure ofbrake members;

ninth, absolutely prompt releaseof brake shoes;

tenth, braking force obtained byminimum effort;

eleventh, brake actuated di-rectly from pedals by strong,simple mechanism; and

twelfth, maximum endurancebecause of the ability of thebronze shoes to resist wear dueto abrasion better than any othermaterial and practical indestruc-

tibility of the hardened steelbrake drum.

This endurance is augmented bythe oil always present betweenbrake surface’s and the lessenedstrain on the parts, because the oilfilm absorbs the first shuck due tobrake application.

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Operation of TypicalBraking and Coasting HubThe New Departure, Model L,has been devised with specialreference to the requirements ofmotorcycle service. As will beevident from inspection of illus-tration, Fig. 256, the generalconstruction of the pedal drivemechanism follows the well-established practice except thatall parts are heavier and stron-ger than anything devised todate. Beginning with a 5/8 inchdiameter axle, the entire mecha-nism has been

augmented in size to conform toautomobile rules of practicerather than adhering to bicycleconstruction. The ball bearingsare large enough for the wheelof an automobile, and, in addi-tion to the use of large balls, anautomobile type or heavy sepa-rator is utilized.

Referring to the illustration, wesee that the main portion of thedevice is a hub shell carrying abrake drum and flanges towhich the spokes are secured.

The outer ball races are formedin the hub shell, which is glasshard at the point where theballs run. The brake drum is asteel stamping 6 inches in diam-eter, and securely attached tothe hub shell flange by a pro-

cess of electric spot welding,which fuses the members at anumber of points to form anintimate bond between them.Contrast this to the usual meth-od of riveting or keying such a

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member in place and it will beapparent that every precautionhas been taken to avoid anytrouble from loose fastenings. Inthe chain drive type the sprock-et-retaining flange is secured tothe brake drum by the sameprocess.

The pedal-chain sprocket isattached to a rotatable membersupported on an adjustable ballbearing, and at the inner endthe member is provided with aspiral thread.

This male thread fits into acorresponding female portion inthe laterally shiftable member,and the angle of the thread issuch that when the pedalsprocket is rotated forward, thespiral draws the shiftable mem-ber against the tapering femaleclutch member forming part ofthe hub shell.

The clutching action connectsthe sprocket to the hub androtates it. If the pedals are heldfrom moving, the clutch releasesautomatically, and the hub shellcan run independently of thefoot pedal mechanism.

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If the foot action is reversed, orthe pedal sprocket rotated back-ward, the female clutch memberin the inner portion of the later-ally shiftable connector will beforced tightly against the maletaper of the brake cam-leveractuator, which can oscillate onthe axle only in the directionnecessary to apply the brake.

If one refers to sketch of brakeend at Fig. 257, it will be seenthat the oscillating motion of theactuator transmits a similarmotion to the end of the lever ofwhich the brake shoe spreadercam forms a part.

Any displacement of the carewill spread the brake shoesapart, and they will fulcrum onthe supporting pin secured tothe brake end plate. The brakeshoes then take up the clear-ance existing between theirouter surface and the innersurface of the drum, and exert aretarding effect in proportion tothe amount of pressure appliedby back pedaling.

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As soon as the back pedalingpressure is released, the springsserve to bring the brake shoesout of engagement immediately.The upper one holds the brakeshoes firmly against the cam,the lower one returns the camlever back against its stop andalso brings the oscillating actua-tor back in position ready forfurther brake application whenthe laterally shiftable memberclutches it.

The brake shoes and spreadercam are carried by a drop forgedsteel plate which has an armformed integrally that is intend-ed to be attached to the framemembers and serve as an an-chorage to prevent brake shoerotation.

How Rider’s Effort isMultipliedA diagram is presented at Fig.258 for the benefit of those me-chanically disposed, whichdemonstrates clearly how thepressure of the rider’s foot onthe pedal is multiplied, and how

much pressure is available be-tween brake shoes and drum tostop the wheel. This shows theeffectiveness and correct designof the internal brake, and howpositive control is obtained withbut little effort.

In this case, we have assumedthat the total weight of a heavymotorcycle, tandem attachmentand two heavy riders is 600pounds.

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The amount of braking forcerequired at wheel rim is equal to36 per cent of the total weight,or 216 pounds, which repre-sents the adhesion between tireand ground. This is not an ex-treme case, as the modern mo-torcycle and two large riderswould easily weigh 600 pounds,and a brake must be desigrnedwith the abnormal service itmay be subjected to in mindrather than the average if it is tohe relied on to cope with theunexpected emergency.

Almost any rider can exert a backpedal pressure of 100 pounds. Thisis applied at. the end of a 6-inchpedal crank, and if the frontsprocket is 5.4 inches in diameter,a pull of 222 pounds is applied tothe chain. This is directed to asprocket having a radius of 2.2inches, which is equivalent to amoment of 488-inch pounds at 1inch from axle center. Owing to thepoint where the spreader-cam leverend bears against the brake shoesbeing less than 1 inch from axlecenter, we have an effective force of601 pounds at the end of the lever.

The difference in length betweenlever and spreader cam furthercompounds the pressure, and ifwe consider all the load concen-trated against one brake shoefor simplicity, we find that wehave an effective spreading forceof 3,606 pounds at the end ofthe brake shoe.

The brake shoe is really acurved lever, so at a point half-way between where the cantbears and the fulcrum pin, we

find that it is possible to exert apressure of 7,165 pounds.

All of this is not available forbraking, however, because if weconsider the coefficient of fric-tion, we will have an effectiveretarding force of 1,075 poundsat the brake drum, and this, inturn, is equivalent to a retardingforce of 230 pounls at contactpoint of wheel tire and roadsurface, which is at 14 inchesradius, or considerably more

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398


than is needled toskid the wheel. If arider is alone, a backpedaling pressure ofabout 50 poundswould suffice to lockthe wheel.

It will be apparent,that positive controlwith minimum exer-tion on part of therider is possible,because the initialforce is compoundedmany times by thesimple and strongleverage provided.Obviously, the brakeforce can be variedat will and is entirelywithin the control ofthe rider.

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400


Motorcycle TiresThe single tube tires used onbicycles did not have sufficientresistance to perform satisfacto-rily on motorcycles, and alsohad the grave disadvantage ofbeing difficult to repair.

The double tube tire which wasused to some extent in bicyclepractice was strengthened andmade larger, and adapted forthe heavier vehicle. This con-struction consists essentially oftwo members, an outer casingor shoe, and an inner tube thatis depended on to retain the air.

The outer casing is attached tothe rim in such a way that it maybe easily removed to gain accessto the inner tube. In event of asmall puncture, the patch isapplied to the inner tube mem-ber, and the outer casing neednot receive attention until a moreconvenient time.

A typical outer casing is shown atFig. 259, A, and it consists essen-tially of a carcass or body com-posed of layers of Sea Islandcotton fabric impregnated with

rubber. A number of plies of thisfabric are placed around a suit-able iron core with vulcanizingcement between each layer, andover these are attached a numberof layers of rubber compositionthat forms the tread of the tires.

After being built up, the assem-bly is placed in a steam heaterand vulcanized or cured until itis practically a solid mass.

The casing is provided withbeads around the inside whichare intended to fit into channelsin the rim. When the innertubes are inflated, the beads willbe forced tightly into the clinch-er rim and the tare will be heldpositively in place. To removethe outer casing, it is necessaryto deflate the tire.

The outer or tread portion,which is the part of the tire thatis in contact with the road sur-face, is made of exceptionallytough rubber compound whichis not apt to depreciate rapidly.

The inner tube, upon which theresiliency of the tire depends,is composed of practically pure

rubber, and is therefore adapt-ed for holding air, though thematerial of which it is com-posed is too soft to possess anystrength. or resistance to abra-sion, which must be providedby the outer casings.

Inner tubes are made in twoforms, the continuous or one-piece type, which is the sameas that so generally used onautomobiles, and the jointed orbutt end form as shown at Fig.259, 13 and C, over.

In the former, the joint is madeby slipping one end of the tubeinto the other, and when the tubeis inflated the collar member willbe forced out tightly against theinner face of the retaining mem-ber on the other end, and an air-tight joint will be obtained. In theform shown at. C, the inner tubeis a closed end form, and has atapering end that is intended tofit into a corresponding femalemember at the other.

The advantage of the jointedinner tube is that it may beremoved from the wheel with-out taking that member out of

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the frame which obviously isnot possible with a one-pieceinner tube.

The form shown at. B, howev-er, is apt to leak to some ex-

tent, and if the jointed innertube is used, the form shownat C is preferred. The ends ofthe tube in contact are also aptto chafe and leak.

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Sidecar AdvantagesWhile the tandem attachment isan inexpensive solution of thepassenger-carrying problem, itis not the most satisfactorybecause it is not a really practi-cal means of carrying an elderlyperson or one of the fair sex.

The occupant of the tandemattachment may throw a ma-chine out of balance by movingaround, and may seriously in-terfere with the proper control ofthe machine by the rider, unlessvery careful and experienced.Then again, it is difficult to car-ry on a conversation betweenthe motorcycle rider and thetandem passenger, so this de-vice is not as sociable as thesidecar.

The sidecar is a simple one-wheel framework that may bereadily clamped to the motorcy-cle, and which carries a seat ofcomfortable proportions that willprovide thorough protection forthe passenger. When a sidecaris used, it is imperative to em-ploy a machine of ample power,

and it is necessary to use a two-speed gear to secure properresults when touring.

A typical side car attached to amotorcycle is shown at Fig. 260,and it will be apparent that thethree-wheel vehicle thus provid-

ed is much more sociable thanthe tandem attachment, andalso much more comfortable forthe passenger.

Owing to the three-point sup-port, neither the rider nor thepassenger need concern them-

403


selves with maintaining balance,as it is impossible for the ma-chine to tip over. It costs butvery little more to use the sidecar than it, does to ride themachine without this attach-ment.

An important advantage of thesick ear construction is that thismember may be readily removedat, such times that, the motor-cycle alone is to be used.

Forms of SidecarThere are two main types ofsidecars, the rigid and the cast-er wheel, both forms beingshown at Fig. 261.

In the rigid wheel type, the out-board supporting member re-volves on a fixed axle and iscapable of only a rotary move-ment.

In the caster wheel form, theoutboard supporting member iscarried in a fork supported by aball bearing steering head so thewheel may turn automatically inthe same direction as the front,wheel of the motorcycle. Experi-

enced users of sidecars areinclined to favor the rigid type,as it, is claimed, it is simpler,and if properly alined with themotorcycle frame there will bebut little more wear on the tirethan is evidenced in the casterwheel type.

The form with the movablewheel is easier to steer however,

owing to the wheel automaticallyassuming the angle required todescribe the curve made whenturning corners.

A sidecar of American designwhich has attracted some atten-tion on account of the novelconstruction is shown at Fig.262. This is a flexible form in

404


which it, is possible for the riderof the motorcycle to lean whenturning corners just as thoughthe sidecar was not fitted to themotorcycle.

The wheel of the sidecar is car-ried on an axle spindle support-ed by a hinged member fromwhich the lever B extends. Thisis joined with lever A on theother end of the axle by a rodpassing through the hollow tubeforming the rear frame member.

Any inclination of the motorcy-cle wheel will produce a corre-sponding movement of the side-car wheel, as lever A controlledby the motorcycle will transmitits motion to lever B that con-trols the sidecar wheel.

A locking lever is provided sothe wheels will remain vertical,and the same effect obtain aswith the rigid type sidecar, ifdesired. It is claimed that, theflexible feature makes the ma-chine easier to steer than theusual rigid type.

The sidecar frame may he fittedwith a variety of bodies depend-

ing upon the preference of thepurchaser, ranging from thesimple chair form, shown atFigs. 261 and 263, to the more

expensive coach-built body de-signs, such as shown at Fig.260.

405


Sidecar AttachmentThe chassis of a typical side earwith the body removed is shownat Fig. 264 to outline the meth-od of attachment ordinarilyfollowed.

Clamps are provided on themotorcycle frame at two points,one at the front end of the diag-onal tube, just, below the framecross bar, and one on the rearfork stay, just a little ahead ofthe motorcycle rear wheel axle.

The front end of the side carchassis is carried by a curvedtube extending from the clampon the frame tube to a similarclamping member at the front,end of the sidecar.

A yoke at the end of the sidecaraxle attaches to the clamp atthe rear end of the motorcycle,and a cross bar or brace ex-tends from the seat post clusterof the motorcycle to a point onthe axle of the side car adjacentto the supporting wheel.

When the clamps are firmlysecured a very strong and rigid

frame structure is obtained, andthe motorcycle and its side carattachment are practically onestructure.

Considerable care is needed infitting a sidecar, because diffi-culty will be experienced insteering if the wheel of the mo-torcycle and that of the sidecarare not in proper alinement.

This means that not only thewheel centers must coincide but

that the front end of the sidecarwheel must be separated from asimilar point on the motorcyclewheel by exactly the sameamount of space as obtains atthe rear end.

In other words, the sidecarwheel must be parallel to themotorcycle wheel and a linedrawn through the axle centersof both wheels must also coin-cide.

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407


The method oflining up asidecar with astraight edge isshown at Fig.265, A.

If the wheel of asidecar is setahead of that ofthe motorcycleor if it is notparallel, steer-ing will be verydifficult be-cause the wheelwill not rollaround on anare of a circlebut will movewith a com-bined rollingand slidingmotion as indi-cated by thedotted lines atFig. 265, B.

The diagrams presented at C will show amethod of sidecar operation recommendedby an English authority in order to secureeasier steering.

Even if the sidecar is perfectly linedup, some difficulty may be experi-enced in steering, though after arider becomes proficient, it will notbe a difficult matter to control thesidecar combination satisfactorily.

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Methods of StartingMotorcyclesThe writer will now describe thecommon methods of starting mo-torcycles equipped with two-speedgear, as the accepted method ofsetting the power plant in motion ina single-geared machine by meansof the pedals is generally under-stood at this time.

The starting crank is a satisfactorymeans, if a multiple-cylinder engineis used and the crank can be ap-plied to the driving gearing in sucha way that the engine will be rotat-ed faster than the starting handle.The starting arrangement used onthe Henderson motorcycle, andillustrated at.

Fig. 266, is a distinctive design,because the handle may be foldedout of the way after the engine isstarted. At A, the crank is shownextended for starting the motor,while at B the crank handle isshown in place in the clip attachedto the frame that holds it out of theway when the machine is in use.

A large and near view of the Indian

kick starter, which is a thoroughlypractical and simple device, isshown at Fig. 267.

A large sprocket is mounted on asuitable bearing, and is adapted tobe oscillated by a starter pedalcarrying a suitable pad memberagainst which foot pressure may beexerted.

The large sprocket is joined a muchsmaller starting sprocket that con-nects with the engine shaft, whenthe pedal is pushed forward andwhich turns the interior mecha-nism of the engine fast enough to

set the power plant in motion.

It is said that the Indian was thefirst American motorcycle to departfrom the conventional pedalingstarting system and to introducethe foot starter.

A forward thrust of the pedal crankengages the ratchet drive thatconnects the small starting sprock-et to the engine shaft and at theend of the stroke the mechanismreleases automatically, and permitsthe crank to return to its normalposition. An automatic mecha-nism provides positive discon-

410


nection from the engine should abackfire occur. The foot rest on thestarting crank is hinged and can befolded out of the way when not inoperation to allow unobstructeduse of the footboard.

With the foot starter, prompt start-ing is facilitated by priming thecylinders with gasoline, particularlywhen the motor is cold. This opera-tion is made easy on the Indianmachines by placing a small sy-ringe or priming gun in the filleropening of the gasoline tank so asmall amount of gasoline may bedrawn out to fill the priming cupson the cylinders.

It is said that when the engine hasbecome heated it will be easilystarted without priming by one ortwo forward thrusts of the foot.

The step-starter used on the Har-ley-Davidson motorcycle is shownin some detail at Fig. 268. Thearrangement is such that a pair ofpedals are provided just. as in theusual construction, though nochain extends from the pedal crankhanger to the hub. Instead, theengine is rotated directly from thepedals through an ingenious ratch-

et and pawl arrangement. Thepawl-carrier plate is securely at-tached to the pedal crankshaft, andwhen that member is rotated for-ward, the pawls fly out and drop

into suitable depressions in theratchet ring which is attached tothe first reduction sprocket, andwhich transmits the motion ofthe crank directly to the small

411


sprocket on the engine shaft.

The countershaft assemblyincludes a substantial ball-bearing carrying the member onwhich the first reductionsprocket and the rear wheeldrive sprocket revolve.

As soon as the engine is started,in some detail at Fig. 268. The

arrangement is such that a pairof pedals are provided just. as inthe usual construction, thoughno chain extends from the pedalcrank hanger to the hub. In-stead, the engine is rotateddirectly from the pedals throughan ingenious ratchet and pawlarrangement. The pawl-carrierplate is securely attached to the

pedal crankshaft, and when thatmember is rotated forward, thepawls fly out and drop into suit-able depressions in the ratchetring which is attached to the.first reduction sprocket, andwhich transmits the motion ofthe crank directly to the smallsprocket on the engine shaft..The countershaft assembly in-

412


cludes a substantial ball-bear-ing carrying the member onwhich the first reductionsprocket and the rear wheeldrive sprocket revolve.

As soon as the engine is started,the pawls are released automat-

ically and remain out of engage-ment as long as the ratchetrevolves faster than the pawl-carrier plate.

Another ingenious fitting is aratchet which works only on

back-pedaling carried at theother end of the countershaftwhich is used to operate thebrake on the rear hub from thepedals when desired.

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Electric Starting andLighting SystemsElectric lighting has long beenrecognized as an ideal illuminat-ing system for motorcycles aswell as motor cars, but it hasbeen somewhat difficult to applyan electric lighting system suc-cessfully to rigid frame ma-chines.

The vibration encountered-tended to rapid depreciation ofthe batteries, and if attemptswere made to utilize currentdelivered directly from a smalldynamo driven from the engine,other difficulties were encoun-tered.

Either the rider was experienc-ing continual trouble with thesmall round leather belts usedin driving the generator or hewas burning out a bulb, whenthe motor was suddenly acceler-ated and the generator pro-duced an excess amount ofcurrent. If the motor was runslowly, the generator would notdeliver enough current and thelights would burn dimly.

In some models of the Indianmotorcycle, two sets of batteriesare furnished and are separatelyconnected to the light. Withreasonable precaution, the ridershould never be without currentfor lights and electric horn oper-ation.

In the machines without theelectric starter attachment whenthe lights become dim, the bat-tery in service is cut out and thefresh battery carried in reserveis connected to the circuit. Thebatteries do not depreciate fromvibration on account of being

415


carried by the spring framewhich insulates them from roadshocks. A patented safety ventis used which permits the es-cape of gas from the batteryinterior, but which absolutelyprevents the leakage of any ofthe electrolyte. Therefore, inpassing over rough roads, or if a

machine upsets in a fall, thereis no weakening of the batteriesby loss of liquid.

The Hendee special model,which is clearly the highestdeveloped form of motorcycleever offered, inasmuch as it notonly incorporates full equipment

including the various necessaryaccessories but also has a two-speed gear and electric self-starter, is shown at Fig. 269. Onthis model, the batteries are soconnected that both of themdischarge into the electric start-ing motor to secure the highestamperage for turning the engine

416


over as fast as possible. It issaid that it is possible to crankthe engine over at the rate of500 revolutions per minute,which is faster than any auto-mobile starter.

The nominal rating of the com-bined electric starter and gener-ator is 1.5 horsepower, but thepower actually developed isinfluenced by the energy neces-sary to start the engine.

The starter has a high overloadcapacity. and just as soon asthe engine begins firing, thestarter automatically becomes agenerator and delivers a currentthat charges the storage battery.

The generator is always runningwhile the engine is in operation,and an automatic regulator isincluded in the system so thatwhen the batteries are fullycharged the surplus electricitygenerated is dissipated.

The current consumption of thelighting system is approximate-ly two amperes. When the bat-teries are connected in multiplea current of 6 volts and 70 am-

peres is available, and whenjoined in series a current of 12volts and 35 amperes is avail-able for starting.

The batteries are charged at. aroad speed of 12 miles per houron the high gear, and the maxi-

mum charging current flows tothe batteries when the machineis operated at 16 miles perhour.

As shown at Fig. 271, the elec-tric starter is attached to theengine crankshaft by a roller

417


chain, and is geared approxi-mately 2 to 1. It is said thatunder ordinary operating condi-tions it will start a cold motor in12 or 15 seconds.

When a motor is warm but 3 to5 seconds will be necessary tostart it. As the generator is con-stantly charging the batterieswhile the engine is running, thepossibility of the cells becomingdischarged is very slight.

The current for ignition is derivedfrom the batteries instead of fromthe usual high tension magneto,and as the batteries are kept fullycharged, the main objection ad-vanced against battery ignition,that of irregular and uncertaincurrent supply, sloes not apply inthis case. A wiring diagram show-ing the connections of the systemis presented at Fig. 270.

The combination motor-genera-tor used in connection with thissystem has been designed espe-cially for the work, and as maybe readily ascertained from theviews at Fig. 272 it is a verycompact and effective piece ofelectrical apparatus.

In order to keep the device to theproper width, an internal commu-tator is used which is carriedinside of the armature member.The brushes are supported by thecover plate, and project into theinterior of the armature to makesuitable connections with thecommutator segments placedtherein. The armature shaft re-volves on single row annular ball-bearings, andI the device thusworks with minimum friction.

By a simple change of the wiringwhich is accomplished by a man-ually controlled switch at thefront end of the tool box, thedevice may be converted intoeither a dynamo or a motor. Theautomatic regulator and switchnumber used in connection withthe system are shown at Fig. 273.

When the switch is placed in thestarting position, the circuitsare arranged so that current isdrawn from the batteries anddirected to the starting motorfields. When the switch handleis moved back for the runningposition, the circuits are alteredso that the current delivered

from the generator armature issupplied to the batteries, firstpassing; through the automaticregulator, which operates on amagnetic principle so that cur-rent is being supplied to thebatteries only when it is of prop-er value for charging thosemembers.

As soon as the engine stopsrotating, if the switch is left inthe charging position, the auto-matic regulator will break con-tact and prevent the batteriesdischarging back through thewindings of the motor-dynamo.

The automatic regulator alsofunctions and disconnects thewindings from the batteries atsuch time that, more than thecharging current, is delivered.The low current release portionof the automatic regulator alsoserves to break time circuit.,when the power plant, is run-ning at, rates of speed thatwould produce less than theproper amount of current forcharging.

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Motorcycle Control MethodsWhen the motorcycle was firstevolved, there was no attemptmade to have the control ar-ranged in a convenient manner,as the various levers by whichthe motor speed was variedwere placed at any point on theframe that proved convenient,for the designer in attachingregardless whether it was thebest position for time pelscmwho would operate the machine.At the present time, every effortis made to locate the importantand frequently manipulatedcontrol members where they canbe easily reached, and veryoften the arrangement is suchthat the rider may have com-plete mastery of the machinewithout removing the hand fromthe handle bars.

The control of American motor-cycles is considerably simplerthan that generally provided onthe foreign mounts, as the com-mon practice in this country isto regulate the motor speedthrough the medium of twistinggrips.

Of course, when a two-speedgear is used, an auxiliary con-trol member is placed conve-nient to the rider to regulate thegear ratio desired, and on somemachines still another lever isused to control the free engineclutch.

Several of the American motor-cycles employ grip control of thefree engine clutch, prominentamong which may be mentioned

by the air and throttle leversmounted on the handle barsand connected to the carburetorthrough the medium of Bowdenwire control.

At the end of each grip, a leveris fulcriuned, one being used towork the front wheel brake,which is a fitting prescribed bylaw abroad, while the other isthe exhaust valve lifter.

On the same bar that carries

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the Schickel, Excelsior and Ea-gle machines. For use in traffic,or operating under conditionsthat necessitate frequent use ofthe clutch, it is apparent that,the most convenient method isby the grip because this doesnot. require the rider to take hishands from the handle barswhich insures positive control ata time that it is most needed.The free engine clutch is regu-lated on some machinesthrough the medium of a pedal,and this control is very satisfac-tory on machines equipped withrunning boards to support therider’s feet and where the usualform of pedaling gear is dis-pensed with.

The first of the American manu-facturers to utilize grip control,to regulate engine speed, werethe makers of the Indian motor-cycle, and this method wasincorporated in even the earliestmodels of these machines.

The method of regulating themotor speed and the constructionof the universal joints and rodsused in connection with practical-

ly all Indian models is shown atFig. 274. The right hand gripcontrols the spark advance andthe exhaust valve lift.

The valves are lifted to relievethe compression and to make itpossible to turn the engine overeasily for starting. The left handgrip is used to control the throt-tle. The twisting movement ofthe grips is transmitted bymeans of a flexible shaft run-ning from the grip through thehollow tube comprising thehandle bar to a hearing fromwhich the end of the shaftprojects.

A universal joint attached to thisshaft transmits its motion to acompound member consisting ofone shaft. telescoping into an-other, that is secured to theactuating lever attached to thesteering head.

The reason for using the tele-scope shaft arrangement is thatit is necessary to have someflexible connection other thanthe universal joint to permit thehandle bars to be turned whensteering the machine.

If one compares this simple anddirect control with that shown atFig. 275, which is an illustrationof a representative Englishconstruction, it will he appar-ent that the American design isconsiderably neater. Of course,on the single-speed Indian mod-els it is necessary to have alever to actuate the free engineclutch which is carried at theside of the machine and anauxiliary pedal is provided nearthe footboard to operate the hubbrake.

On the two-speed machines, alever is provided to shift thepositive change speed clutchand a foot-controlled membersupplied to release .the masteror free engine clutch. In additionto the control members shownat Fig. 275, there is anotherlever which is not illustrated,provided to operate the variablespeed pulley. The control of theignition is by a small lever at theside of the tank connected withthe magneto contact breaker.

The speed of the motor is con-trolled by the magneto lever and

421


the exhaust valve lifter, a handlever to control the free engineclutch is mounted and as is trueof the other elements it is joinedto the clutch member by theflexible wire connection.

From the handle bar assemblyshown, five of the Bowden wiresextend to the various elementsthey are intended to control.One goes to the air slide of thecarburetor, another to the throt-tle regulating the supply of gas.

The third member goes to theexhaust valve-lifting arrange-ment, while the fourth and filthextend to the free engine clutchand the front wheel brake re-spectively.

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Bowden Wire ControlWhile the Bowden wire control isused on practically all of the for-eign motorcycles, and is em-ployed to some extent on Ameri-can machines as well, there is ageneral lack of understanding ofits principle of action on the partof the American rider, and con-siderable trouble is experiencedfrom time to time in fitting up ormaking repairs to this system.

The Bowden wire mechanismconsists mainly of two parts,one which, termed “the outermember,” is a closely coiled andpractically incompressible spiralspring while the “inner member”

is an inextensible wire cablepassing through the outer mem-ber which acts as a casing.

The usual mechanical method oftransmitting power in otherthan a straight line in this coun-try is by means of universaljoints, small bell crank leversand suitable connecting rods.The Bowden wire mechanism isconsiderably simpler and iseasily fitted.

The principal requirement isthat the outer member or casingshall be anchored to a stop ateach end, while the inner mem-ber is attached to an operatinglever at one end and to the ob-ject to be moved at the other.

A diagram showing the method ofoperation is shown at Fig. 276,and the reader should have nodifficulty in understanding theaction of this control system. Aline of Bowden wire mechanismsufficient to reach from the pointwhere the object is to be moved tothe point where the necessarypower is to be applied is repre-sented by D D D.

The outer cable of the mechanismis passed around any interveningcorners or obstacles. At C C theinner member of the mechanismwill be seen emerging.from theouter case being attached at. oneend of the actuating lever A andat the other to the object to bemoved B.

The outer member is anchoredto fixed abutments G G. If thelever A is moved, the motion is

at once imparted to the otherend. When being actuated, themechanism will exhibit a wrig-gling movement at the curvesbecause the inner member at-tempts to reach the straight lineof pull, but is resisted by theouter casing which cannotshorten its length inasmuch asit is anchored at both ends.

The movement should not berestrained, as the mechanismfunctions best when the curvesare free. The dotted lines showthe lever A in its actuated posi-tion, and the weight B, or objectto be moved, correspendinglyraised. E E are adjustablescrews or stops, the screwingout of which is equivalent tolengthening the outer member,and arc held in posit ion by thelock nuts F F.

Various examples of the leversused in connection with Bowdenwire mechanism are shown atFig. 277. The hand lever withratchet retaining lever shown atA is widely used for clutch actu-ation, brake application andlifting the exhaust valves.

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Fig 278 - BowdenWire Mechanism

for ControllingFront Wheel

Brake, AuxiliaryAir Intake, and

Magneto

425


The assembly shown at B con-sists of two levers carried abovethe clamp, and a lifting leverbelow it. One of the upper mem-bers may be used to control thespark time and the other con-nected to the throttle, or bothmay be used to regulate thecarburetor.

The handle at the lower part ofthe assembly may be connectedto brake, clutch, or exhaustvalve release. A group of threecontrol levers, each being plain-ly marked to show the functionsperformed, designed for handlebar attachment is shown at C.The pedal at D is adapted forbrake actuation.

The Bowden wire control is alsosold in connection with com-plete control devices, two popu-lar fittings being outlined at Fig.278. At A a front wheel brakeassembly is shown. The contactblocks which bear against thewheel rim are carried by a U-shaped member that is held atits lower portion by clips at-tached to the fork sides.

The upper portion may be guid-ed by any suitable bracket andis connected with a hand leverintended to be attached to thehandle bar by a length of theBowden wire mechanism. Anauxiliary air fitting and suitablecontrolling means are shown atB, while the usual method ofrigging up to a magneto contactbreaker is shown at C.

The following hints on fitting theBowden wire mechanism, given bythe makers, will undoubtedly befound of value by riders and repairmen who are not thoroughly famil-iar with the application or mainte-nance of this system of control.

It is important that the innermember of the mechanismshould be soldered before it, iscut, as it is composed of a num-ber of fine strands which areliable to become untwisted un-less this precaution is taken.

With the smaller sizes, up to No.3, a pair of pliers or a spoke-cutting machine will suffice forcutting, but larger sizes willrequire a file or cold chisel tosever the strands.

The brass nipple supplied forthe purpose should be carefullyattached to the end of the innermember. A good method of ef-fecting this is as follows: Thewire, after being soldered andcut, should be passed throughthe nipple, the end then beingnipped fiat for about 1/16 inch.This will prevent it drawing outagain during the process ofsoldering the wire and nippletogether, which should be clonein combination with a non-cor-rosive soldering fluid (on noaccount should killed spirit beused), care being taken that thesoldered joint extends the fulllength of the nipple.

The nipple should then be heldin the vise, and the wire burredover and finished off with a blobof solder. It will then be foundimpossible to remove the nippleby any fair means.

For the varieties of the mecha-nism known as Bowdensilver,Bowdenbrass, and Bowdenite,special metal caps are providedfor encasing the ends.

426


These serve the purpose of fin-ishing the ends off neatly, and,in the case of Bowdensilver andBowdenbrass, prevent the pro-tecting cover uncoiling.

When a single-pull lever is used, itis necessary to have a spring at theopposite end of the wire to whichthe lever is fixed, in order to ensureprompt recovery. This spring maybe made either to pull the innermember back through the outermember, after pressure has beenrelieved from the operating lever, orit may be inserted between the stopholding the outer member and theend of the inner member, in whichcase, of course, it will be in com-pression. In the latter case, it willgenerally be found that the simplestmethod of fixing is to fit the deviceup minus the spring, and to windthe spring on afterward, as oneputs a key on a split ring.

But when a double-pull lever isused, a spring is not necessary,as the separate mechanisms sobalance each other that whilethe lever is pulling on in onedirection it is pulling off in theother.

Care should be taken that theinner member, on leaving thestop the outer member termi-nates, should be kept in anabsolutely straight line, asshould it be otherwise, it willrub on the edge of the stop, andbe gradually worn away in con-sequence.

The inner member should bethoroughly smeared with motorgrease or.vaaeline before beingpassed through the outer mem-ber.

motorcycles and sidecars 6. frame parts chapt. vi....

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