CA1037520A - Wheel with detachable hub unit - Google Patents

Abstract

In re application of Thomas J. Lester For COMPOSITE MOTORCYCLE
WHEEL CONSTRUCTION

ABSTRACT OF THE DISCLOSURE
A lightweight composite motorcycle wheel construction characterized in that it comprises a wheel unit casting includ-ing concentric outer and inner rim and sleeve portions integrally connected together by angularly spaced spokes; and a hub unit casting having an interference fit within the bore of said sleeve portion thus to frictionally retain said units together against relative angular and axial movement while the bearing receiving bore in said hub unit is located and held coaxially of said rim portion, said wheel and hub units additionally being welded together to retain them as aforesaid despite application of torque and axial loads exceeding the frictional resistance of said interference fit.

Description

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BACKGROUND OF THE INVENTION
Historically, all commercially produced motorcycles have been equipped with wire spoke wheels which are relatively light in weight and which have adequate strength and resilience in normal operation of the motorcycle.
Wire spoke wheels, however, have certain disadvan-tages such as the necessi$y of using a tire inner tube, the necessity o~ periodic tightening of the spokes to avoid unsafe riding and handling conditions of the vehicle, the abrasion of the tire inner t~e, and the danger of puncturing the tire inner tube by the head of a broken spoke.
Moreover, wire wheels have an inherent weakness when subject to severe impacts, such as when crossing chuckholes or bumps. Although wire spokes are effective against tensile forces absorbed in the side of the wheel away from the impact, they do not function against compression forces and ~hus do not provide radial support of ~he rim in resisting deformation at ~he point along the rim perimeter subjected to severe im~act. ~; -;
In Leaning a motorcycle on curves at high speeds, the xims of ~ -wire spoke wheels are especially stressed and tend to twist relative to the neutral axis of the rim. Hence, the warping of rims, the fracturing of rims along circumferential break lines, the stretching and loosening o spokes that are common-place under severe service conditions are important as a basis fox improvements in ~he manufacturing of motorcycle wheels.
In departing from wire wheel construction for motor- ;
cycles, lightweight construction must be maintained through the ^
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use of lightweight metals such as aluminum, magnesium, or alloys thereof. In any attempt to construct motorcycle whe~ls ~rom these metals, this invPntion is based on the premise that it i5 most practical from a commercial standpoint to make the wheels as castings. It is known that therè have been attempts to manu-facture motorcycle wheels in the form of light metal castings.
These efforts have been generally unsuccessful, particularly in -building wheels for the medium to large size motorcycles. An insurmountable difficulty in forming wheels as a single casting, ~`
probably attributable to the wheel configuration itself, is the tendency to have porous rims if the hubs are good and, if the ;~
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casting practice is changed to get good rims, then the hubs are ~ ;
porous.
Porous metal is weak and prone to cracking or yielding ~ -.~
in the high stress areas of the rim or in those portions of the ;
hub which support bearing races, etc. Porous metal i5 further unacceptable in the rims of wheels used with tubeless tires since the sealing compounds normally used on rim surfaces do not seal this type of porosity. MoreoverJ porosity is unacceptable in any portion of the wheel which must be threaded to receive ` . .
cap screws or other threaded elements.
Yet a~other difficulty encountered with wheels formed of a single casting is the inevitable presence of shrink frac-tures which are believed due to shrinkage o the hub portion to a greater extent than the~rim portion.
Nonetheless, there is great inducement to equip motorcycles with wheels formed from lightweight metal castings ~ .
because there is a great need to reduce the unsprung weight of motoxcycles. For example, a cast aluminum alloy wheel accord-ing to the invention can ~e substantially lighter than a wire

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wheel of the same tire size and p~rmits the use of a tubeles~
tire. The elimination of the inner tube result~ in a further ten to fifteen percent reduction of total wheel weight.
Another problem that arises in the casting of motor-cycle wheels is the complicated web structure of many rear wheel hubs. Such hubs, if formed of a lightweight metal, must frequently contain steel or iron inserts which provide such ~-elements as brake drum surfaces and bearing race supports. Most rear wheel hubs define recesses for rubber drive compensators.
Some hubs have bosses to which brake discs may be applied.
Hence, objects of the invention are: to provide light-weight wheels for motorcycles which are superior in strength, road life and freedom from maintenance, labor, and cost when compared with conventional wire spoke wheels.
A further object is to provide motorcycle wheels of a design enabling the casting thereof by te`chnologically modern methods, such as those employing the use of permanent molds in the casting of such lightweight metals as aluminum, magnesium, and alloys thereof, and to use casting technology which will permit the use of weldable lightweight metals and alloys in casting the wheels.
It is a further object to adopt a method of casting motorcycle wheels which a~oids porous metal formation in ths castings.
An object also is to pro~ide a wheel unit having a central open region of standard dimension suitable for receiving a variety of hub assemblies insertable thereunto which enables use~o~ a standard wheel unit with hub assemblies o~ standard exterior configuration but which may vary as to brake design, power coupling and the like. ~

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Another object ancillary to the foregoing object is to achieve a wheel design which substantially reduces the cost ~:
of molds through the use of a standard wheel unit with a variety of hub units thereby obviating the necessity for providing an . ;
equal variety of complete wheel molds.
An object ancillary to the foregoing object is to.de- . :
vise a wheel uniquely adapted for mass production assembly . - .:
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methods enabling assembly of two basic interchangeable parts. .: -. A further object is to design a motorcycle whe.el which achieves the foregoing functional objects with such visual :.
features as to be commercially acceptable to the trade.
S~MMARY OF THE INVENTION ~ ;
In attempts to cast whole motorcycle wheels of light-weight weldable aluminum and magnesium alloys, it has been dis-covered that a round wheel casting cannot be obtained if~the center opening of the wh~el is less than abo~ut four inches in diameter.
. The above objects and others that may be apparent hereinbelow are achieved in a vehicle wheel, especially a mo~or- -;
cycle wheel, which comprises two basic portions, i.e., a wheel `~
unit and a hub unit of which the wheel unit comprises a rim, an ~ . :
inner tubular-element, and radial spokes integrally joined with ~
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- the rim and tubular element and of which the hub unit has an ;~
interference fit in the bore of the tubular element to coaxially locate the bearing receiving bore of the hub unit with respect to the rim and to frictionally retain the wheel and hub unit against relative rotation and relative axial movement~
Another feature of the invention is that the high- ~
strength rim section of the wheel unit has bead retaining side ;:
walls o which each defines an outward axially-facing substantially .:

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~3>~0 planate sur~ace under cut at least along substantial portions of the side wall by a conc~ntric groove which divides a radially . outer~part of the planate !surface ~rom a radially inner par~
thereof.
Accordinq to its broadest aspect, the present invention provides a lightweight composite wheel and hub construction : -comprising a wheel unit casting of lightweight metal including .
aluminum, magnesium and alloys thereofi said wheel unit casting .
including concentric rim and tubular portions integrally --connected together by angularly spaced-apart spokes; said ~tubular portion having a bore therethrough coaxial with said rim portion, and a hub unit casting of lightweight metal including aluminum, magnesium, and alloys thereof; said hub unit casting . .
having a central bearing receiving bore and a coaxial cylindrical -~ :
exterior surface which has an interference fit with said bore o~ .
said tubular portion to compressively preload said spokes, to ;
frictionally retain said units together against relative rotation ;
and relative axial movement, and to locate and retain said bearing receiving bore coaxially of said rim portion; said cylindrical surface projecting axially beyond one annular end of said tubular portion: said units being welded together around said one annular end and said axially projecting cylindrical surface to prevent re~ative movement thereof despite application of torque and axial loads exceeding the frictional resistance of said interference fit. ~ ~ :
According to another aspect, the present invention `: -~-provides a method of making a motorcycle wheel comprising the :~
steps of providing as castings of a weldable lightweight metal :~
including aluminum, magnesium and alloys thereof, a hub unit, and a wheel unit having a centrally open tubular portion to receive said hub unit and having ~ concentric rim portion integrally ~ -5~

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connected to said tubular portion by angularly spaced-apart spokes~ heat treating the castlngs to relieve casting stresses; ,~, ' - machine finishing the units including finishing th~'circular,end- ; ~
surfaces of said tubular portion and finishing the outer surface ' ~ ' of the hub unit and the inner surface of the tubular portion of ~ -' the wheel unit to provide substantially complementary cylindrical surfaces of which said inner surface is slightly smaller in diameter than said outer surface at ambient temperature `~
and slightly larger in diameter at an appreciably higher than ambient temperature when the hub unit means remains at ambient temperature; inserting the hub unit into said machined inner , ~ -surface with said wheel unit heated sufficiently to receive the ,~
hub ùnit; cooling said wheel unit to shrink-fit it on said hub '"
unit; and welding one circular end surface of the tubular portion around an end portion of said outer surface which projects axially beyond said one end surface while rotating said shrink-fitted wheel and hub units about the axis of said inner and outer surfaces, BRIEF DESCR~PTION OF T~E DRAWINGS . ~;
Fig. 1 is a perspective view of a portion of a wheel in accordance with one form of the invention, i.e., a wheel '~
unit having spokes radiating along a common diametral transaxial `'~
plane;
Fig. 2 iS a cross section of the wheel unit of Fig. 1 taken along a diametral plane.
Fig. 3 is a cross section of a spoke taken along line III-III of Fig. l; -Fig. 4 is a perspective view of a modified wheel having two series of spokes in staggered relati~n; ~ ;~
Fig. 5 is a cross section of the wheel of Fig. 4 taken along a diametral transaxial plane;

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Fig. 6 is a cross section of a spoke taken along lines VI-VI of Fig. 4;
; ~ Fig. 7 is a fragmentary sch~natic cross section ~f a - ~
portion of a mold in ~nveloping relation with a pair of spoke~ -of the wheel of Fig. 1 as-viewed along a surface of revolution - ` concentric to the wheel unit axis;
Fig. 8 is a fragmentary schematic cross section of a `-~
portion of a mold in enveloping relation with spoke~ of the wheel of Fig. 4 as viewed along a surface of revolution concentric to the axis of the wheel unit;
Fig. 9 is a fragmentary view in cross section taken ~-along line IX-IX of Fig. 11 of a rear motorcycle hub unit shown in combination with a wheel unit of the type shown in Figs. 4 and 5;

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~ ig~ 10 is a view of the right side of the hub unit as shown in Fig. ~;
Fig. 11 is a left side view of the hub unit as viewed in Fig. 9;
Fig. 12 is a fragmentary view in cross section taken along a transaxial diametral plane of a front motorcycle wheel having a hub unit received within a wheel unit of the type shown in Figs. 1 and 2;

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Fig. 13 is a ragmentary view in transaxial diametral cross section of a modified motorcycle front wheel having a hub unit received within a wheel unit of the type sho~n in Figs. 1 and 2.

DETAILED DESCRIPTION OF
THE P REF1~ RRE D EMBO DI MENT `
Figs. 1, 2, 3 and 7 relate to one of the two basic components o~ the improved wheel described ~erein, i.e., a wheel unit 5. Unit 5, in its preferred form, is a one-piece casting which, when u~ed in a wheel for a motorcycle or other stringent use, is preferably cast from a lightweight weldable metal such ~ ~ -as aluminum, magnesium or alloys thereof by permanent mold cast-ing. For less strenuous uses, wheel units embodying the design of unit 5 may be produced rom moldable plastic mate~ials includ~
ing reinforced plastics by wéll-known molding methods.
As shown, the unit 5 comprises a rim 6, a sleeve-like or tubular hub element 7 and spokes 8. The spokes 8 join inte- `~
grally with both the hub element 7 and the rim 6 to form a one-piece structure. The rim 6 comprises sidewalls 11, 12 joined~
by a center wall 14. As shown, the sid~walls are o mirror image similarity with each sidewall having a laterally outward facing side surface having portions 15, 16 at different radii separated '' ' ~' ~

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17. As shown, surface portions 15, 16 lie ~ssentially in res-pective side planes of the rim perpendicular to the wheel axis - ~
N-N and extend substantially over the full radial width of ' ' respective side walls. It is found that the groove construction ~ ~' of the rim sidewalls contributes greatly to the strength and `' road life of the wheel by eliminating stress concentrations which ordinarily occur in the center wal} 14 in the region between the sidewall and the spokes 8. The grooved sidewall also contri- 'butes greatly to the beam strength of the rim between intersections of adjacent, spokes with the rim and causes bending of the rim in , the region of the sidewalls 11, 12 to be a rarity. ,~
It may be noted that the groove 17 is interrupted adja~
cent the intersections of the spokes with the rim by filled-in ,, ~ , areas 18. Areas 18 are useful as points of`engagement for mold '~
ejection pins.
The rad~ally outer surface oE the center wall 1~ of the }Lm has the usual drop center cross sectional contour for enabl-~ng t:e removal of pneumatic tires. The rim 6 is centrally ' - apertured through a radially inwardly extending boss 21 having ~ ~ -an openiny 22 through which a valve stem is normally installed.
The sidewalls and center wall of ~he rim form an impermeable '- barrier to air. With a valve stem installed in oper.ing 22 and `;,'~
a tire mounted wi~h its beadsin airtight contact with the inner , ' surfaces of walls 11 and 12, the air is retained by the tire on the rim without the aid of an inner tube, an important innova- ' t'' ~ ' ' '' tion în the use of motorcycle wheels.
The spokes 8, as indicated by the cross section of '~ , Fig. 3, are of I-beam construction each of which tapers or ~ ' -7- " , ; - : . ...... ....

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decreases in ~xoss section along their full length outwardly from the hub element 7 to the rim 6~ As shown by Fig. 3, the spokes extend in radial planes M-M parallel to, and containing, the axis N-N. The I-beam construction or the spokes contri-butes greatly to the strength of the whe~l disclosed herein and to a wheel strength substantially greater than the conventional wire spoke wheel. From Fig. 3, it may be seen tha~ the spokes 8 are "drafted" with respect to a mold parting line P-P. The 1 term "parting line" is used herein as normally used in the mold-ing trades and refers to a plane or area along which two adja-cent mold sections or halves may part. Parting of the molds is facilitated by designing all parts of a casting so that molded surfaces of a casting are at no less than a minimum inclination with respect to the mold parting direction as to cause the mold to break away and separate from the molded article at the slight-est movement of the mold sections along their path o~ departure.
The "minimum angle" just referred to is what is known in the trade as "draft" and is an important eature in the wheel units of this invention. Thus it will be noted that the flange por-20 - tions 25, 26, 27, 28 taper outwardly in a direction away from ;~
their connecting web 2~ and the parting line or plane P-P. This is also true of the rim 6 along its surfaces 31, 32 and along outer surfaces 33, 34 of the hu~ element 7. An inner surface 35 - of the hub element shown in dot-dash outline is normally cast . with "draft" and then machined to obtain the finished cylindrical surface 36.
The mode of obtaining the wheel unit structure is -further illustra~ed by Fig. ? which illustrates a cross section of a mold and adjoining spokes 8 of a unit 5 taken along a sur-face o revolution with respect to the axis N-N. The mold 41 .. ~ ~
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comprises mold halves 42, 43 separating at the partin~ line P-P.
The relationship of "draft" with respect to the parting line is ;;
illustrated. Obviously, the channel surfaces of the rim 6 cannot be a portion of the mold halves 42, 43. A plurality of core pieces capable of defining the channel surface of the rim are -inserted into the mold chamber prior to bringing the mold sections 42, 43 into position for molding which easily detach from the wheel unit after it is cast. The channel surface of the rim and the interior hub element surface of the casting are trued to the precise dimensions required for use by machining operations. ~
For aesthetic purposes, the lateral surfaces of the rim and the ~ -spoke flange edges may be machine finished andl if desired, polished. ~-Figs. 4, 5, 6 and 8 relate to a wheel unit 50 in which -~spokes 51, 52 join integrally with a rim 54 and a hub element 55 to form a one piece unit or casting. The e`ssential difference ~`
between unit 50 and the previously described wheel unit 5 is in `;
the arrangement of the spokes. Unit 51) i9 depicted with one set ;
of four spokes 51 in angularly staggered relation with another se~.of four spokes 52. Viewed only in their angular location about the axis of rotation S-S of the wheel unit, the spokes of one set are located halfway between angularly adjacent spokes of the other set although other angular spacing arrangements are possible. FigO S shows that the rim 54 also has grooves in ~
~he outer side surfaces of its side walls. The grooves are cir- ;
cularly continuous, as shown in Fig~ 4O
The spokes of each set occur in a conical surface of revolution extending radially from the hub element 55 toward a transaxial central plane T-T of the wheel unit and thus in con~
vergent relation with the surface of revolution of the other-1" .
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set of spokes~ As shown, the junctions of the spokes of each set with the hub element 55 are spaced axially along the hub element at a greater distance ~rom the transaxial plane T-T
than their junctions with the rim 54. The spokes of each.set approach ~ut are just short of an intersection with plane T-T
at junction with the rim. This arrangemen results in an ex-tremely deformation-resistant wheel in which somewhat smallex spokes may be used than are used in a wheel of similar size comprising the unit 5 under similar service conditions.
10 . Fig. 6 illustrates that each of the spokes, e.g., spoke 51, is symmetrical with respect to a radial plane R-R
which is parallel to, and contains, the axis of rotation S-S. ~ -Thus, the spokes may be said to extend in a radial direction while leaning in an axial direction toward the central plane T-~. Further to be noted from Fig. 6 is that the spokes 51, 52 are of I-beam cross section with the web of the spoke approxi-mately bisected by the plane R-R and the surfaces of the flanges having mold-parting draft with respect to a mold parting line 58.
This arrangement is better understood with reference to Fig. 8 in which is shown a fragmentary cross section of.the mold 61 in enclosing relation with spokes 51, 52 of the wheel unit 50. The cross section is taXen along.a surface of revolution concentric to axis S-S as projected into a plane. The mold 61 comprises : mold portions 62, 63 whlch may part~with respect to the irreqular - parting line 58. It will be understood that any cross sections of the mold and the wheel unit taken at different radii from .
the axis S-S will depict a change in relative positions and cross section size of the spokes 51, 52 because of he convergence o~
the surfaces of revolution in which the spokes are contained and tha tapering size of the spokes.

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~7~2`i3 WHEEL VNITS AND HIJB UNITS IN COMBINATION ~ .
Fig. 9 depicts the wheel unit SO in combination with a hub unit 65 adapted for use on a Kawasaki Motorcycle Model 903 manufactured in AXashi, Japan.
Fig. lO illustrates the left side of the hub as seen in Fig. 9 and outlines pockets 66 of irregular contour adapted for receiving resilient blocks (not shown) of mechanism (not .j .
shown3 for coupling the hub in drive relationship with drive apparatus of the motorcycle.
Fig. 11 illustrates the right side of the hub as shown '~
in Fig. 9 in which is formed an annular recess 67 for recelving brake mechanism. Fixedly seated on an interior drum surface 68 ;~
wi~hin the recess is a brake drum 69. ;
The unit 65 is formed with an outer finished cylin~
drical surface 71 having an interference fit with the interior cylindrical ~inished surface 72 of the whee~ unit 50. me sur- -ace 71 terminates toward the left in a shoulder 74 which axially locates the wheel unit 50 on the hub unit 65. The inter-; . .
ference fit not only accurately locates the bearing recesses 78 ~`
and 79 in coaxial relation to the rim of the wheel unit 50 but --additionally provides high frictional resistance to relatiYe rotation and relative axial movement of the wheel and hub units ~ -50 and 65. The interference fit also serves to impose compres~
sive preloading of the spokes of the wheel unit 50, as does the ~ ~ -` air pressure in a tire mounted on the rim o~ the wheel unit 50.
4 As known, permanent mold and die castings generally have superior strength in compression as compared to tension, and hence, the present invention by reason of compressive preloading lessens the tensile stresses during use of the composite construction herein. me units 50, 65 are further secured from relative , ' , , .

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angular ox axial movement by a weld 75 which joins wi~h an end surface of the hub element 55 of wheel unit 50 and an adjacent portion of the cylind~icai surface 71 of unit 65. Preferably another weld 75 will be provided at the other end of the hub element 55 and the adjoining shoulder 74. As evident, noxmal usage of the composite wheel and hub unit construction herein will not impose any stresses on the welds 75 whereas relative rotation and axial movement due abnoxmally high axial and torque loads are resist~d by the welds 75.
10 . The hub unit 65. further provides a central axially extending chamber 77 which provides bearing recesses 78, 79 for receiving and supporting a bearing and axle assembly by ~ .
which the wheel comprising units 50 and 65 may be attached to a vehicle frame.
Fig. 9 shows that the.hub ellement 55 of the wheel unit 50 is in immediate radial proximity with the brake drum 69 and therefore in excellent heat exchange relationship there-with. The wheel unit therefore acts as a heat reservoir and heat radiating facility for effectively dissipating heat from .20 the brake area of the hub unit. The interior.details of hub units other than special relationships, such as named above, with respect to the wheel unit in general are not of interest regarding this invention. .
~ igs. 12 and 13 typify front wheel designs in accord~
ance with the invention. As shown in Fig. 12, a front wheel hub unit 81 is shown in place within the wheel unit 5 with its ~.
exterior finished cylindrical suxface 82 in tightly fitting frictionally engaged relation with the interior finished surface 83 of the hub element of unit 5O The hub unit 81 further pro~ides :~
a shoulder 84 against which the wheel unit is seated. Units 5 , ` , '~ ' -;

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and 81 are seçured from relative ~xial or angular movement against excessive axial and torque load~ by a weld 85. Again, as in Fig. 9 the shoulder 84 will preferably be of smaller 1 diameter than the hub element 7 for another weld 85 at the other end of the hub element 7 and the shoulder 84. A plurality of counterbored axially-extending bores 87 located along a circum- ` -ference concentric to the hub axis accommodate bolts tnot shown~
by which an annular disc or other brake device is secured to the surface 88.
Fig. 13 illustrates a modified front motorcycle wheel -~
comprising the wheel unit 5 and a hub unit 91 of modified design.
As found in previous embodiments, the hub unit and the wheel ; ;~
unit have circumferentially mating surfaces 92 and 93, respect-ively, which provide an interference fit. During assembly, the hub unit 91 is pressed into the wheel unit 5 to the proper rela- `
tive position such as by the use of a jig. 'The wheel unit 5 is preferably heated to 2~0F. or more ~or receiving the hub unit 91. Upon cooling, the wheel unit S will shrink on the hub unit 91 to frictionally retain the wheel unit S and hub unit toget-.
her against relative angular`and axial movement. Thereupon the units are welded along opposite edges of the hub element by i~
welds 95, 96 which join with the hub unlt surface 92 and the end edges of the wheel unit. In connection with any of the embodi-ments herein described, it is to be understood that the wheel ;`
units o~ different design, as typified by those of Figs. 1 and 4, are interchangeable for substantially any purpose.
As before indicated, the preferred practice of produc-ing wheels in accordance with the invention is to provide cas~-ings of weldable metals. A highly satisfactory aluminum alloy 1 used in the manufacturing of the wheel and hub units described ~, .

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, , 3~5~) above is a co~mercially available alloy identified by numeral "A356" according to standard commercial nomenclature of Aluminum Manufacturers Association. This alloy is also identified by the American Society of Testing Materials designation "SG70B".
To start the manufacturing process, the wheel unit and the hub unit are provided as castings molded through the use of "permanent" metal molds with the hub element of the wheel unit potentially adapted to receive the unit. The mating sur- ~
faces of the units are not less than about four inches in dia- ;
meter. Permanent molds yield a desired finish and quality in castings comprising one of the preferred weldable alloys. -~
The castings then undergo a heat treating program in which they are first heated to a T4 (commercial nomenclature) condition, i.e., heated to 1000FI to 1100F. for twelve hours and then-quenched in warm water. They are then trued and shape-corrected by cold working. Thereafter~ they are heat treated to a T6 condition, i.e., heated to 350''F. and held at this tem-perature four or five hours and then allowed to air cool.
The units are thus prepared for machining. With the center o~ the mass of the casting in mind, the wheel unit is chucked so that the hub element thereof is bored and the internal -~
channel sur~ace of the rim is finished in concèntricity. The `~
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extern`al laterai planate surfa~es of the rim are machined to planes perpendicular to the axîs of revolution of the wheel unit.
The exterior drum surface of the hub unit is machined to a dia-meter at room temperature slightly larger than the internal diameter of the hub element of the wheel unit, and is otherwise prepared by machining, e.g., for receiving bearing races, a brake disc, cap screwx, etc.
Assembly of ~he two units proceeds with heating of the wheel unit to a temperature appreciably higher than room -. '':. . .' 1 . . . . . .

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temperature, e.g., in the range of 2~0 to 300Fo after which t~.e hub unit is inserted into the heated hub element with both elements being relatively positioned within a revolvable jig ~ -of a welding machine. On cooling of the wheel unit, khe wheel unit and hub unit are secured together in a "shrink fit". The jig and wheel assembly are then rotated while weld beads are applied within an inert or deoxygenated atmosphere to circular -~
end suraces of the hub element and circular surfaces of the hub unit adjacent to opposite ends of the hub element. The -hub and wheel units are thus assembled into an integral wheel on the welding machine.
While it is preferred in the rear driving wheel of a motorcycle that the mating hub surfaces of the whee~ unit and the hub unit be cylindrical and continuously engaged in an , axial direction, the front undriven wh~eel is subject to less stress and may be constructed with a wheel unit of which axially-spaced end portions of its hub element which bear on a hub unit are of smaller diameter than an intermediate internal surface of not less than about one and one-half inches which does not , engage the hub unit. The internal cylindrical end surfaces of ~
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the hub element will then be in the order of not less than ap-proximately three-sixteenths of an inch in width exclusive of the associated welds. -~
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The foregoing description is intended to point out those features of wheel structure which render the motorcycle wheels described herein substantially advantageous over the prior art motorcycle wheels, especially wire spoke wheels.
Wheels such as described will result in the elimination of inner tubes from the motorcycle tires. This will not only reduce C09t '~
but render ~he sidewalls o ~he tires more flexible with greater -15~
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~' ~ ; : "; ' 1~33~752~;3 road yripping capacity. The wheel herein described is greatly improved over prior art devices with regard to the overall s~rength of the wheel especially in the spoke and rim construc-tionr The side wall oonstruction of the rim is of particular interest. A wheel as described herein holds great promise for substantially reduced manufacturing costs on a mass-produced basis.
The construction of the wheel as two separate cast-ings permanently joined by an interference fit and additionally -~
by welds enables for the first time the successful application of casting technology to the manufacturing of a practical wheel cast from light metals. The wheel unit i9 constructed in such a manner that it can never become loose and unstable within its own structure, whereas the motorcycle wire wheels of the prior art in prevalent use are subject to deterioration resulting in a relatively short road life. Moreover, the wheels disclosed herein ofer great flexibility to mari~facturers in the combining of a few types of wheel units with a greater number of types of hub units. For the immediate future, the invention offers special interest for the purchaser in the so-called "after market"
who seeks better equipment than that of standard merit normally occurring on the vehicle as originally equipped.

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The composite wheel construction herein eliminates porosity and shrink fractures as previously discussed and more- ~;
over the shrink fit facilitates asse~bly of the wheel and hub units without use of anti-seizing compounds to provide high frictional resistance to relative angular and axial movement of the wheel and hub units. -.

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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A lightweight composite wheel and hub construction comprising a wheel unit casting of lightweight metal including aluminum, magnesium and alloys thereof; said wheel unit casting including concentric rim and tubular portions integrally connected together by angularly spaced-apart spokes; said tubular portion having a bore therethrough coaxial with said rim portion; and a hub unit casting of lightweight metal including aluminum, magnesium, and alloys thereof; said hub unit casting having a central bearing receiving bore and a coaxial cylindrical exterior surface which has an interference fit with said bore of said tubular portion to compressively preload said spokes to frictionally retain said units together against relative rotation and relative axial movement, and to locate and retain said bearing receiving bore coaxially of said rim portion; said cylindrical surface projecting axially beyond one annular end of said tubular portion; said units being welded together around said one annular end and said axially projecting cylindrical surface to prevent relative movement thereof despite application of torque and axial loads exceeding the frictional resistance of said interference fit.

2. The construction of claim 1 wherein said hub unit has an integral collar which abuts the other annular end surface of said tubular portion to predeterminedly axially locate said hub unit with respect to said wheel unit.

3. The construction of claim 2 wherein said hub unit has a brake drum locked therewithin by casting of said hub unit therearound; said brake drum being located in the axial region of the interference fit between the bore of said tubular portion and said cylindrical surface of said hub unit.

4. The construction of claim 2 wherein said hub unit has a circular series of holes axially therethrough within said cylindrical surface for screw means by which a brake disc is adapted to be clamped against one end of said hub unit in coaxial relation to said cylindrical surface thereof.

5. The construction of claim 4 wherein said one end of said hub unit is at the end of the axially projecting cylindrical surface.

6. The construction of claim 1 wherein said hub unit has an integral collar of diameter greater than the bore of said tubular portion and smaller than the outside diameter of said tubular portion to form a shoulder abutting the other annular end surface of said tubular portion thus to predeterminedly axially locate said hub unit with respect to said wheel unit; and wherein additional welding material is deposited around the outside diameter of said collar and around the radially outer portion of said other annular end.

7. A method of making a motorcycle wheel comprising the steps of providing as castings of a weldable lightweight metal including aluminum, magnesium and alloys thereof, a hub unit, and a wheel unit having a centrally open tubular portion to receive said hub unit and having a concentric rim portion integrally connected to said tubular portion by angularly spaced-apart spokes; heat treating the castings to relieve casting stresses; machine finishing the units including finishing the circular end surfaces of said tubular portion and finishing the outer surface of the hub unit and the inner surface of the tubular portion of the wheel unit to provide substantially complementary cylindrical surfaces of which said inner surface is slightly smaller in diameter than said outer surface at ambient temperature and slightly larger in diameter at an appreciably higher than ambient temperature when the hub unit means remains at ambient temperature; inserting the hub unit into said machined inner surface with said wheel unit heated sufficiently to receive the hub unit; cooling said wheel unit to shrink-fit it on said hub unit; and welding one circular end surface of the tubular portion around an end portion of said outer surface which projects axially beyond said one end surface while rotating said shrink-fitted wheel and hub units about the axis of said inner and outer surfaces.

8. The method of claim 7 wherein said step of machine finishing said inner and outer surfaces brings about a diameter relationship enabling insertion of said hub unit at ambient temperature into said wheel unit heated to a temperature in the range of 240°F. to 300°F.

9. The method of claim 7 wherein said step of machine finishing said hub unit includes finishing a collar portion at the other end of said outer surface which abuts the other circular end surface for locating said units in predetermined axial relationship.

10. The method of claim 7 wherein said step of machine finishing said hub unit includes finishing a collar portion at the other end of said outer surface which abuts the radially inner portion of the other circular end surface when said hub unit is inserted into said wheel unit; and wherein the radially outer portion of said other circular end surface is welded around the periphery of said collar portion while said units are rotated as aforesaid.