GB1560131A

GB1560131A - Lightweight wheel

Info

Publication number: GB1560131A
Application number: GB3050177A
Authority: GB
Original assignee: Lester Industries Inc; LESTER IND Inc
Current assignee: Lester Industries Inc; LESTER IND Inc
Priority date: 1976-12-27
Filing date: 1977-07-20
Publication date: 1980-01-30
Also published as: JPS5383205A; FR2375057A1; IT1082272B; DE2735930A1

Description

(54) LIGHTWEIGHT WHEEL (71) We, LESTER INDUSTRIES INC, a corporation organised and existing under the laws of the state of Ohio, United States of America, of 25661 Cannon Road, Bedford Heights, Ohio 44146, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a lightweight wheel, and particularly, but not exclusively, to a lightweight motorcycle wheel, and to a method of making a lightweight wheel.

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 alunimum 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.

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 rollformed steel rim is weaker in some directions than in others. Furthermore, the roll-forming of the steel strip to the desired rim crosssection 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 aluminium hub and spoke units, the latter have steel inserts providing tabs for welding to the steel rims.

According to the present invention in one aspect there is provided a lightweight wheel comprising a die cast aluminim alloy hubspoke unit having a central hub portion and an outer circular ring portion integrally connected together in coaxial relation by radially extending spokes; and an extruded alunimum alloy drop centre rim having an inside diameter which is a shrink fit around the outside diameter of said ring portion to retain said rim and hub portion in coaxial relation and to preclude relative axial and rotary movement of said rim and unit.

According to the present invention in another aspect there is provided a method of manufacturing a lightweight wheel, comprising the steps of die casting an aluminium alloy hub-spoke unit to provide coaxial hub and outer ring portions integrally connected by radially extending spokes; forming a length of extruded aluminium alloy having a crosssection corresponding to that of a drop centre rim into a circular rim having butt welded ends; sizing and truing said rim by radial expansion to receive a pneumatic tyre of predetermined size; shrinkfitting said sized rim around said ring portion to frictionally interengage finished outside and inside diameters of said ring portion and rim; and locking said rim and unit together by aluminium alloy plug welds in radial holes through the bottom of a drop centre well of said rim and in coaxial conical depressions in the outside diameter of said ring portion at locations corresponding to the outer ends of said spokes.

In order to impart improved fatigue characteristics to the lighweight wheel the shrinkfitted extruded rim and die cast hub and spoke unit can be aluminium alloy plugwelded together not only at locations corresponding to the outer ends of the spokes but at locations mid-way between the spokes.

In accordance with a feature of the present invention, the extruded rim, after flash butt welding, is stretched to true circular form followed by accurate machining of the inside diameter of the rim to a diameter slightly smaller than the machined outside diameter of the die cast hub and spoke unit to provide the desired magnitude of shrinkfit of the rim on the outside of the hub and spoke unit.

An embodiment of the invention will now be described, by way of an example, with reference to the accompanying drawing, in which: Figure 1 is a side elevation view of a motorcycle front wheel embodying the present invention; Figure 2 is a cross-section view taken substantially along the line 2-2 indicated in Figure 1; Figure 3 is an enlarged fragmentary radial cross-section view illustrating the rim and hub-spoke unit prior to welding; Fig 4 is yet a larger view similar to Fig 3 except showing the rim and hub-spoke unit welded together; Fig 5 is a side elevation view of a motorcycle rear wheel embodying the present invention; and Fig 6 is a cross-section view taken substantially along the line 6-6 of Fig 5.

Figs 1 and 2 illustrate a lightweight front wheel 1 for a motorcycle, said wheel 1 comprising a die cast aluminium 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 anti-friction 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 1 crosssection 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 aluminium alloy drop center pneumatic tyre supporting rim in which the wall thicknesses and shapes of various portions are made to obtain optimum characteristics of the rim 14. Said rim 14 has tyre bead supporting flanges 15 and a drop centre well portion 16 of conventional form to facilitate mounting and removal of a pneumatic tyre on said rim 14.

The outside diameter of the outer ring portion 3 of the die casting 2 is accurately finished, as is the inside diameter of the well 16 so that the rim 14 and the hub and spoke unit 2 will have a diametrical shrink fit of from about .006 to .009 inch.

Although the shrinkfit of rim 14 on die casting 2 provides adequate frictional resistance to prevent relative rotation and axial movement of the rim 14 and die casting 2, they are positively locked against relative movement by aluminium alloy plug welds 17 as shown in Fig 4. To make such plug welds 17, holes 18 of say 1/4" diameter are drilled through the bottom of the drop centre well portion 16 as shown in Fig 3 with just the point of the drill entering the outer ring portion 3 at the location of each spoke 11. The holes 18 and conical depressions are then filled with plug weld metal as by a M.I.G.

welding process which welds the rim 14 to the outer ring portion 14 as shown in Fig 4.

To provide increased fatigue characteristics of the rims 14 and die casting 2 assembly, such plug welds 17 will also be made at locations midway between the spokes 11.

One important feature of the present invention is that the hub-spoke unit 2 may have shrinkfitted and welded 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 21 for accommodating the tyre valve.

Figs 5 and 6 illustrate a lightweight rear wheel 21 for a motorcylce having a die cast aluminium alloy hub-spoke unit 22 to the outer ring portion 23 of which the extruded aluminium alloy rim 24 is shrinkfitted and welded as described in relation to Figs 1 to 4.

In Figs 4 and 5 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 casing 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 as shown to provide a rigid support of the ring portion 23 with respect to the brake drum insert 26 and the bearing bore 25. The wheel 21 in 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 4 and 5 has safety beads 31 in addition to the bead supporting flanges 32 and drop centre well 33. It is to be understood that the rim 14 of the Fig 1 and 2 wheel may have similar safety beads 31.

The die cast hub-spoke units 2 and 22 are preferably formed of aluminium-siliconmagnesium 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 centre 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 aluminium alloy rim 14 or 24 is concerned, it is preferably formed of magnesium-silicon-aluminium 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 2-3So stretch. Then, the sized rim 14 or 24 is finished on its I.D. to have a shrink fit with respect to the O.D. of the hub-spoke unit 2 or 22.

As a final machining operation, holes 18 are drilled through the well 16 or 33 of the rim 14 or 24 with only the point of the drill penetrating the outer ring portion 3 or 23.

Then, using M.I.G. welding, a plug weld 17 of aluminium alloy wire is formed so as to be flush with the surface of the well. As shown in Fig 4, the plug welding operation provides a relatively deep penetration around each drilled hole 18 and around each conical depression. The plug welds 17 are centered with respect to the spokes and preferably similar plug welds 17 are provided mid-way between the spokes to enhance fatigue characteristics of the composite wheel assembly.

By making the rim 14 or 24 of extruded aluminium 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 finished as not to require any finishing operations except for the machining of the I.D. of the well 16 or 33 to provide the required shrinkfit. By providing the shrinkfit seizing or galling is avoided as would be encountered in pressfitting an aluminium alloy rim onto an aluminium alloy die casting.

In the M.I. G. plug welding of the rim 14 or 24 to the die casting 2 or 22 the preferred aluminium alloy wire is No. 4043 which has excellent welding properties with both the rim and hub-spoke unit alloys previously referred to.

The shrinkfit of the rim on the hub-spoke unit is effective to preload the ring portion, said spokes, and the hub portion in compression and to preload the rim in hoop tension.

WHAT WE CLAIM IS: 1. A lightweight wheel comprising a die cast aluminium alloy hub-spoke unit having a central hub portion and an outer circular ring portion integrally connected together in coaxial relation by radially extending spokes; and an extruded aluminium alloy drop centre rim having an inside diameter which is a shrink fit around the outside diameter of said ring portion to retain said rim and hub portion in coaxial relation and to preclude relative axial and rotary movement of said rim and unit.

2. A wheel as claimed in claim 1, in which said ring portion and said rim are welded together at locations corresponding to the radially outer ends of said spokes.

3. A wheel as claimed in claim 2, in which said ring portion and rim are further welded together at locations mid-way between the radially outer ends of said spokes.

4. A wheel as claimed in claim 2 or claim 3, in which said ring portion and rim are welded together by aluminium alloy plug welds filling radial holes through the bottom of a drop centre well of said rim and coaxial conical depressions and said ring portion.

5. A wheel as claimed in claim 4, in which said plug welds are flush with the outside diameter of the bottom wall of said drop centre well to obviate the need of further finishing operations.

6. A method of manufacturing a lightweight wheel, comprising the steps of die casting an aluminium alloy hub-spoke unit to provide coaxial hub and outer ring portions integrally connected by radially extending spokes; forming a length of extruded aluminium alloy having a cross-section corresponding to that of a drop centre rim into a circular rim having butt welded ends; sizing and truing said rim by radial expansion to receive a pneumatic tyre of predetermined size; shrinkfitting said sized rim around said ring portion to frictionally interengage finished outside and inside diameters of said ring portion and rim; and locking said rim and unit together by aluminium alloy plug welds in radial holes through the bottom of a drop centre well of said rim and in coaxial conical depressions in the outside diameter of said ring portion at locations corresponding to the outer ends of said spokes.

7. The method claimed in claim 6, in which said tim and unit are additionally

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The rim 24 shown in Figs 4 and 5 has safety beads 31 in addition to the bead supporting flanges 32 and drop centre well 33. It is to be understood that the rim 14 of the Fig 1 and 2 wheel may have similar safety beads 31. The die cast hub-spoke units 2 and 22 are preferably formed of aluminium-siliconmagnesium 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 centre 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 aluminium alloy rim 14 or 24 is concerned, it is preferably formed of magnesium-silicon-aluminium 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 2-3So stretch. Then, the sized rim 14 or 24 is finished on its I.D. to have a shrink fit with respect to the O.D. of the hub-spoke unit 2 or 22. As a final machining operation, holes 18 are drilled through the well 16 or 33 of the rim 14 or 24 with only the point of the drill penetrating the outer ring portion 3 or 23. Then, using M.I.G. welding, a plug weld 17 of aluminium alloy wire is formed so as to be flush with the surface of the well. As shown in Fig 4, the plug welding operation provides a relatively deep penetration around each drilled hole 18 and around each conical depression. The plug welds 17 are centered with respect to the spokes and preferably similar plug welds 17 are provided mid-way between the spokes to enhance fatigue characteristics of the composite wheel assembly. By making the rim 14 or 24 of extruded aluminium 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 finished as not to require any finishing operations except for the machining of the I.D. of the well 16 or 33 to provide the required shrinkfit. By providing the shrinkfit seizing or galling is avoided as would be encountered in pressfitting an aluminium alloy rim onto an aluminium alloy die casting. In the M.I. G. plug welding of the rim 14 or 24 to the die casting 2 or 22 the preferred aluminium alloy wire is No. 4043 which has excellent welding properties with both the rim and hub-spoke unit alloys previously referred to. The shrinkfit of the rim on the hub-spoke unit is effective to preload the ring portion, said spokes, and the hub portion in compression and to preload the rim in hoop tension. WHAT WE CLAIM IS:

1. A lightweight wheel comprising a die cast aluminium alloy hub-spoke unit having a central hub portion and an outer circular ring portion integrally connected together in coaxial relation by radially extending spokes; and an extruded aluminium alloy drop centre rim having an inside diameter which is a shrink fit around the outside diameter of said ring portion to retain said rim and hub portion in coaxial relation and to preclude relative axial and rotary movement of said rim and unit.

7. The method claimed in claim 6, in which said tim and unit are additionally

plug-welded together at locations mid-way between said spokes.

8. A lightweight wheel substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 4 or Figures 5 and 6 of the accompanying drawing.

9. A method of making a lightweight wheel, substantially as hereinbefore described with reference to the accompanying drawing. - '.