Aluminum alloy motorcycle wheel having an extruded rim shrink fitted and resin bonded to a die cast hub-spoke unit

A lightweight motorcycle wheel and method of making the same comprising a die cast alumnium alloy hub and spoke unit around which an extruded aluminum alloy drop center rim is shrinkfitted and bonded by high strength thermosetting resin adhesive between coaxial cylindrical walls of said rim and unit.

BACKGROUND OF THE INVENTION 
It is known to provide automobile wheels comprising roll-formed steel rims 
and steel hub-spoke castings which are pressfitted and welded together or 
comprising such steel rims and aluminum castings which are pressfitted 
together and locked as by dimpling the rims into peripheral depressions in 
the castings or by providing steel plugs in radial holes in the castings 
welded to the inside diameters of the rims. For examples of automobile 
wheels of the character indicated, reference may be had to the U.S. Pat. 
Nos. 3,484,137, 3,635,529, and No. 3,807,805. 
In the manufacture of automobile wheel rims of the character indicated, 
strip steel stock is roll-formed to rim cross-section and into circular 
form followed by welding together of the ends and pressfitting the rim 
around the machined outside diameter of the casting. Accordingly, in a 
roll-formed steel rim, it is not possible to obtain optimum metal 
distribution as required to best withstand the stresses and strains 
imposed on the finished wheel in use. Moreover, a roll-formed steel rim is 
weaker in some directions than in others. Furthermore, the roll-forming of 
the steel strip to the desired rim cross-section entails relatively sharp 
angle bending of the strip so as to impose severe tensile stresses on the 
outside of the angles and severe compressive stresses on the inside of the 
angles. 
Aside from the foregoing, in some known automobile wheels having 
roll-formed steel rims and cast aluminum hub and spoke units, the latter 
have steel inserts providing tabs for welding to the steel rims. 
SUMMARY OF THE INVENTION 
In contradistinction to the foregoing the present invention provides a 
lightweight motorcycle wheel which has an extruded aluminum alloy drop 
center rim and a die cast aluminum alloy hub-spoke unit, said rim and unit 
being shrinkfitted and bonded together. 
The present invention also provides a novel method of manufacturing a 
lightweight motorcycle wheel in which the tire bead supporting surfaces of 
the extruded rim are true circles coaxial with the bearing bore of the die 
cast hub-spoke unit. 
To impart improved fatigue characteristics to the lightweight motorcycle 
wheel herein the shrinkfitted extruded rim and die cast hub and spoke unit 
are bonded together by a high strength thermosetting adhesive confined in 
a radially thin annular chamber defined between widely axially spaced 
apart shrinkfitted surfaces of the rim and hub and spoke unit. 
Other objects and advantages will appear from the ensuing description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 illustrate a lightweight front wheel 1 for a motorcycle, said 
wheel 1 comprising a die cast aluminum alloy hub and spoke unit 2 to 
provide: a continuous outer ring portion 3 having a radially inwardly 
extending reinforcing flange 4; a central hub portion 5 of lightweight 
hollow construction reinforced by webs 6 and 7 and having tapped holes 8 
on opposite sides thereof for brake disc mounting screws. In the event 
that the wheel 1 is to have but one brake disc, the other side of the 
wheel 1 will be covered by a suitable cover plate (not shown) attached as 
by screws having threaded engagement with the tapped holes 9. The hub 
portion 5 has a central bearing bore 10 for mounting of the front axle in 
well-known manner in suitable antifriction bearings retained in the 
bearing bore 10. Interconnecting the hub portion 5 and the outer ring 
portion 3 are seven integral spokes 11 of decreasing I cross-section from 
the hub portion 5 to the ring portion 3. Said spokes 11 are joined to the 
outer ring portion 3 by generously rounded gussets or continuations 12 of 
the flange 4. 
Shrinkfitted on the hub and spoke unit 2 is an extruded aluminum alloy drop 
center pneumatic tire supporting rim 14 in which the wall thicknesses and 
shapes of various portions are made to obtain optimum characteristics of 
the rim 14. Said rim 14 has tire bead suporting flanges 15 and a drop 
center well portion 16 of conventional form to facilitate mounting and 
de-mounting of a pneumatic tire on said rim 14. 
The outside of the outer ring portion 3 of the die casting 2 is accurately 
finished, as is the inside of the well 16 so that the rim 14 and the hub 
and spoke unit 2 will have a dimetrical shrink fit at widely spaced apart 
areas as shown in FIGS. 3 and 4. In FIG. 3 the rim 14 has an internal 
locating rib 17 for axially centering the rim 4 and portion 3, said rib 17 
being of axial width and radial depth about 0.005 inch less than the axial 
width and radial depth of the peripheral groove 18 around the portion 3 to 
define an annular chamber filled with high strength thermosetting resin 
adhesive which positively locks the rim 14 and hub and spoke unit 2 
together against relative rotation and axial movement. In FIG. 4 the rib 
17 is omitted and the groove 18 is of about 0.005 radial depth to define 
the annular chamber for high strength thermosetting resin adhesive. 
One important feature of the present invention is that the hub-spoke unit 2 
may have shrinkfit and bonded thereto a rim 14 of any desired width 
between the beadsupporting flanges 15 and of course the die split may be 
on the circle 19 (see FIG. 1) so that any selected hub 5 configuration may 
be provided to suit the particular make of motorcycle with which the wheel 
1 is to be used. 
The outer ring portion 3 of the unit 2 is provided with an internal boss 20 
for a radially-drilled hole 20' accommodating the tire valve. 
FIGS. 5 and 6 illustrate lightweight rear wheel 21 for a motorcycle having 
a die cast aluminum alloy hub-spoke unit 22 to the outer ring portion 23 
of which the extruded aluminum alloy rim 24 is shrinkfitted and bonded as 
described in relation of FIGS. 1 to 4. In FIGS. 5 and 6 there is provided 
a central bearing bore 25 and concentrically therearound the die casting 
22 has a steel brake drum insert 26. Openings 27 may be provided in the 
die casting 22 through which the brake linings may be inspected for wear, 
said openings 27 having been formed by brake drum locating pins in the die 
casting die. The spokes 28 integrally connect the hub 29 and outer ring 
portion 23 with respect to the brake drum insert 26 and the bearing bore 
25. The wheel 21 is well-known manner will be provided with a suitable 
drive means such as a drive spline. The pockets 30 are provided for weight 
saving and a bearing retainer cap (not shown) will cover the pockets 30. 
The rim 24 shown in FIGS. 5 and 6 has safety beads 31 in addition to the 
bead supporting flanges 32 and drop center well 33. It is to be understood 
that the rim 24 of the FIGS. 1 and 2 wheel may have similar safety beads 
31. 
The die cast hub-spoke units 2 and 22 are preferably of 
aluminum-silicon-magnesium alloy such as a modified 360 alloy which 
provides a good combination of castability, strength, and corrosion 
resistance. 
The die castings 2 and 22 have smooth surfaces and a high degree of 
accuracy to minimize the amount of metal removal on machined surfaces, 
e.g. the center bearing bores 10 and 25 and the O.D. of the outer ring 
portions 3 and 23 for shrinkfit purposes with respect to the respective 
rims 14 and 24. 
Insofar as the extruded aluminum alloy rim 14 or 24 is concerned, it is 
preferably magnesium-silicon-aluminum alloy No. 6061-T6 or -T651. The 
extrusion die is designed to provide for optimum distribution of the 
metal. After extrusion the extruded bar is cut to desired length and is 
stretched beyond its yield point to straighten the same. The straightened 
bar may then be placed in an oven for appropriate heat treatment 
whereafter the bar is ready to be rolled into a rim followed by truing the 
ends and flash butt welding the ends together. The butt weld is then 
finished and the wheel 1 or 21 is sized by subjecting the rim 14 or 24 to 
a 2-3% stretch. Then, the sized rim 14 or 24 is finished on its I.D. as in 
FIG. 3 or 4 to have a shrink fit with respect to the O.D. of the hub-spoke 
unit 2 or 22 and to define the bonding chamber 18. 
By making the rim 14 or 24 of extruded aluminum alloy as aforesaid, the rim 
is of great strength in all directions and has desired ductility and 
elongation. All of the surfaces of the rim 14 or 24 are sufficiently 
smooth finish as not to require any finishing operations except for the 
machining of the I.D. of the well 16 or 33 as in FIG. 3 or 4 to provide 
the required shrinkfit and for bonding. By providing the shrinkfit seizing 
or galling is avoided as would be encountered in pressfitting an aluminum 
alloy rim onto an aluminum alloy die casting. 
In the manufacture of the wheel 1 or 21 herein a high strength adhesive (or 
so-called "structural" adhesive) in paste form is applied by brush, 
trowel, or knife in the groove 18 (FIG. 3 or FIG. 4) to about 0.010 inch 
thickness. The rim 14 is then heated to expand the same so that it may be 
positioned around portion 3 of the hub and spoke unit. As the rim 14 
cools, it shrinks onto the portion 3 to provide the shrink fit at the 
widely spaced areas adjacent the ends of groove 18. As the rim 14 shrinks, 
it applies pressure on the adhesive in chamber 18 and squeezes out excess 
adhesive through the decreasing gaps of the shrink fit surfaces of the rim 
14 and portion 3. 
As a final operation, the wheel 1 or 21 is placed in an oven for curing of 
the adhesive which is confined under pressure in chamber 18 and thereby 
providing a wheel 1 or 21 in which the rim 14 or 24 and hub and spoke unit 
2 or 22 are positively locked against relative movement by shrink fitting 
and bonding even under severe load conditions including shock loads. When 
the completed wheel 1 or 21 cools to ambient temperature it shrinks and 
thus maintains the cured adhesive under pressure in the closed chamber 18. 
By way of illustrative example, the thermosetting resin adhesive may be a 
modified epoxy resin such as HI-FLEX 2214 (3M Company) or CYBOND 
X-10255-191-1 (American Cyanamid Company) or a vinyl/phenolic base resin 
such as PLIOBOND 9001 (The Goodyear Tire and Rubber Company). These resins 
can be cured at temperatures between about 200.degree. F. and 400.degree. 
F. with curing times decreasing with increasing temperature. These or 
other suitable thermosetting resins with appropriate silane adhesion 
promotors are listed below: 
Diallyl Phthalate (DAP) . . . 
Epoxide, Cycloaliphatic . . . 
Epoxy . . . 
Melamine . . . 
Phenolic . . . 
Polybenzimidazole . . . 
Polybutadiene . . . 
Polyester . . . 
Polyethylene, Crosslinked . . . 
Polyimide . . .