NZ544690A - Aerodynamically designed cycle wheel with spokes increasing in width and decreasing in thickness from hub to rim - Google Patents

Abstract

The cycle wheel has spokes 3 which increase in width (in the plane of the wheel) and decrease in thickness (from 6 to 7) in the direction from the hub 1 to the rim 2.

Description

Intellectual Property Office of N.Z. - 9 MAR 2007 RECEIVED Our Ref: DCL001NZ Patents Form No. 5 PATENTS ACT 1953 Complete After Provisional No. 544690 Filed: 16 January 2006 COMPLETE SPECIFICATION A CYCLE WHEEL I, Milton John Bloomfield, a New Zealand citizen of 1/42 Main Road, Christchurch, New Zealand, 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: A CYCLE WHEEL FIELD OF THE INVENTION This invention relates to a high performance cycle wheel for competition or general use.

BACKGROUND OF THE INVENTION Designers are continually searching for cycle wheel designs having improved performance. Disc wheels are preferred where a cycle is not subject to cross winds. Where a cycle is exposed to cross winds spoked wheels may be employed.

Currently the best performing spoked wheel design employs five spokes which taper in width in the plane of the wheel from the hub to the rim of the wheel. All but one wheel design known to the applicant have spokes of constant width or which taper in the plane of the wheel from the hub to the rim. This is believed to be due to the focus of design in minimising linear rather than rotational drag.

W0 1 998/057812 discloses a wheel having three spokes that taper in width in the plane of the wheel from the rim to the hub. However the spoke thickness normal to the plane of the wheel is constant, resulting in increased rotational drag towards the rim of the wheel. The depth of the rim also varies circumferentially in this design.

It would be desirable to provide a cycle wheel having improved aerodynamic performance or to at least provide the public with a useful choice.

SUMMARY OF THE INVENTION In designing the wheel of the invention rotational drag was considered as well as linear drag. In order to reduce rotational drag the thickness of the spokes tapers from the hub to the rim where the rotational speed, and thus rotational drag, is highest. The spoke design must be optimized to meet the structural loads as well as the aerodynamic requirements.

JUL 2007 According to one aspect of the invention there is provided a cycle wheel comprising: a. a rim; b. a hub; and c. a plurality of spokes extending between the rim and the hub, wherein the width of each spoke in the plane of the wheel increases from the hub to the rim and the thickness of each spoke normal to the plane of the rim decreases from the hub to the rim.

The width of each spoke in the plane of the wheel preferably ranges between 50mm to 70mm near the hub, more preferably between 55mm to 65mm and optimally about 65mm. The width of each spoke in the plane of the wheel ranges between 70mm to 120mm near the rim, preferably between 85mm to 100mm and optimally about 90mm.

The maximum thickness of each spoke near the hub is preferably between 18mm to 22mm and optimally about 20mm. The maximum thickness of each spoke near the rim is preferably between 12mm to 20mm and optimally about 15mm.

The cross section of each spoke is preferably an aerofoil that is symmetrical about its main axis. The maximum thickness of the aerofoil is preferably between 30 to 40% of the chord length.

The cycle wheel preferably has three spokes which vary in width continuously from the hub to the rim.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings which are incorporated in and constitute part of the specification, illustrate embodiments of the invention and, together with the general description of the invention given above, and the detailed description of embodiments given below, serve to explain the principles of the invention.

Figure 1 shows a side view of the cycle wheel; JUL 2007 Figure 2 shows an end view of the cycle wheel; Figure 3 shows a perspective view of the cycle wheel; Figure 4 shows a cross-sectional view of a spoke near the hub (A-A); and Figure 5 shows a cross-sectional view of a spoke near the rim (B-B).

DETAILED DESCRIPTION OF THE INVENTION The drawings show a cycle wheel according to one embodiment of the invention optimized to reduce linear and rotational drag at about 50 Kmph. The wheel consists of a hub 1 and rim 2 interconnected by three spokes 3, 4 and 5. Although three spokes are preferred the invention is not limited to a three spoke embodiment and more spokes could be provided. The spokes preferably have a symmetrical aerofoil cross section as shown in figures 4 and 5. The maximum thickness 6, 7 of each spoke is preferably between 30 to 40% of the chord length of the aerofoil section.

The spokes taper from the rim to the hub and the thickness of each spoke tapers from the hub to the rim. This reduces rotational drag as the outer sections of the spokes exposed to higher rotational speeds have a thinner section. For a 700mm wheel the width of the spokes (i.e. section length in the plane of the wheel) near the hub at section A-A is preferably 50 to 70mm, more preferably 55 to 65mm and optimally about 65mm. Near the rim at section B-B the width is preferably between 70 to 120mm, preferably 85 to 100mm and optimally about 90mm. The maximum thickness 6 of each spoke at section A-A is preferably between 18 to 22mm and optimally about 20mm. The maximum thickness 7 of each spoke at section B-B is preferably between 12 to 20mm and optimally about 15mm.

The wheel is preferably integrally formed from a plastics resin fiber reinforced material. Preferably the material includes carbon fibers.

The resulting wheel has low rotational and linear drag whilst having good structural characteristics. Although the wheel may initially find application in the high performance market it could also be produced for general cycling markets, possibly utilising less expensive fiber composite materials.

While the present invention has been illustrated by the description of an embodiment thereof, and while the embodiment has been described in detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and method, and illustrative example shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of the applicant's general inventive concept.

Claims (19)

CLAIMS 10

1. A cycle wheel comprising: a. a rim; b. a hub; and c. a plurality of spokes extending between the rim and the hub, wherein the width of each spoke in the plane of the wheel increases from the hub to the rim and the thickness of each spoke normal to the plane of the rim decreases from the hub to the rim.

2. A cycle wheel as claimed in claim 1 wherein the width of each spoke in the plane of the wheel ranges between 50mm to 70mm near the hub.

3. A cycle wheel as claimed in claim 1 wherein the width of each spoke in 15 the plane of the wheel ranges between 55mm to 65mm near the hub.

4. A cycle wheel as claimed in claim 1 wherein the width of each spoke in the plane of the wheel is about 65mm near the hub. 20

5. A cycle wheel as claimed in any preceding claim wherein the width of each spoke in the plane of the wheel ranges between 70mm to 120mm near the rim.

6. A cycle wheel as claimed in any preceding claim wherein the width of 25 each spoke in the plane of the wheel ranges between 85mm to 100mm near the rim.

7. A cycle wheel as claimed in any preceding claim wherein the width of each spoke in the plane of the wheel is about 90mm near the rim. 30

8. A cycle wheel as claimed in any preceding claim wherein the width of each spoke increases continuously from the hub to the rim.

9. A cycle wheel as claimed in any preceding claim wherein the maximum 35 thickness of each spoke near the hub is between 18mm to 22mm. 10 JUL 2007

10. A cycle wheel as claimed in any preceding claim wherein the maximum thickness of each spoke near the hub is about 20mm. 10

11. A cycle wheel as claimed in any preceding claim wherein the maximum thickness of each spoke near the rim is between 12mm to 20mm.

12. A cycle wheel as claimed in any preceding claim wherein the maximum thickness of each spoke near the rim is about 15mm.

13. A cycle wheel as claimed in any preceding claim wherein the cross section of each spoke is an aerofoil that is symmetrical about its main axis. 15

14. A cycle wheel as claimed in claim 13 wherein the maximum thickness of the aerofoil is between 30 to 40% of the chord length. 20

15. A cycle wheel as claimed in any preceding claim wherein the aerofoil of each spoke is optimized to reduce linear and rotational drag for a bicycle operating speed of about 50 Kmph.

16. A cycle wheel as claimed in any preceding claim wherein the wheel has three spokes. 25

17. A cycle wheel as claimed in any preceding claim wherein the wheel is integrally molded.

18. A cycle wheel as claimed in any preceding claim formed of a fiber composite material. 30

19. A cycle wheel as claimed in claim 18 including carbon fibers. 35 Intellectual property Office of N.Z. 2 6 FEB 2007 s RECEIVED DYNAMIC COMPOSITES LTD By their Attorneys Ellk | Veri/oeket | Terry 7