GB2496161A

GB2496161A - Aerodynamic bicycle cranks

Info

Publication number: GB2496161A
Application number: GB1118977.6A
Authority: GB
Inventors: David William Jack
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-11-03
Filing date: 2011-11-03
Publication date: 2013-05-08
Also published as: GB201118977D0

Abstract

A bicycle crank comprises a substantially planar member 1,3 including means 9 for receiving a bicycle pedal and means 7 for attaching to a spindle for rotation relative to the spindle. The means 9 for receiving a pedal may be plural, and located at differing distances from the spindle axis. The planar member 1,3 may be flat, or have a slightly curved or lens-like shape, and may be smooth or dimpled.

Description

BICYCLE CRANKS

This invention relates to bicycle cranks.

A bicycle chainset converts the reciprocating motion of a rider's legs into rotational motion used to drive a chain which, in turn, drives the rear wheel of the bicycle. Traditionally, a chainset includes a chainring attached at its centre to a spindle and a pair of crank arms which have pedals attached to free ends of the crank arms. The crank arms are usually mounted 180 degrees out of phase.

A problem with conventional chainsets is that they are not aerodynamic and the crank arms in particular disturb the air flow around the chainset, giving rise to unwanted drag, especially in a racing bicycle.

It is therefore an object of the present invention to provide a bicycle crank which overcomes or at least ameliorates the above disadvantage.

According to one aspect of the present invention there is provided a bicycle crank comprising a substantially planar member including means for receiving a bicycle pedai and means for attaching to a spindle for rotation reiative thereto.

According to another aspect of the present invention there is provided a pair of bicycle cranks, each comprising a substantially planar member including means for receiving a bicycle pedal and means for connecting to a spindle for rotation relative thereto. One of the cranks may be secured to a chainring.

The or each crank may be in the form of a disc. Alternatively, the or each crank may be in the form of an oval, square or star.

The or each crank may have a substantially continuous surface. Alternatively the or each crank may have a discontinuous surface, for example in that apertures could be provided in the crank.

The spindle connector may be made of metal, such as steel, titanium or an aluminium alloy. The or each substantially planar member may be made of carbon-fibre material or a metal, such as steel, titanium or an aluminium alloy.

The means for receiving a pedal may be made of a metal, such as steel, titanium oran aluminium alloy.

The or each substantially planar member may be planar or may be angled or curved, or may be lenticular with the outer surface being convex and the inner surface being planar. One or both of the surfaces of the or each substantially planar member may be smooth or may be dimpled.

The or each crank may be provided with a plurality of means for receiving a pedal, for example four receiving means may be provided. The plurality of pedal receiving means may be distributed substantially uniformly around a peripheral region of the substantially planar member. The receiving means may be provided at different distances from an axis of the spindle connector.

For a better understanding of the present invention and to show more clearly how it may be carried into effect reference will now be made, by way of example, to the accompanying drawing which shows one embodiment of a pair of bicycle cranks in accordance with the present invention.

The figure shows a pair of bicycle cranks 1, 3 which are not in the form of arms, but are in the form of discs which, in use, are connected one to each end of a spindle (not shown) as with conventional crank arms. One of the discs 1 is attached to an essentially conventional chainring 5 for driving the chain (also not shown).

The centre of each of the discs 1, 3 is formed with a spindle connector 7 which is configured to connect the discs with the spindle in conventional manner such that the discs are not rotatable relative to the spindle and transmit driving force from both of the discs to the chainring 5. The spindle connector 7 is suitably made of metal (for example, steel, titanium or an aluminium alloy) while the outer part of the disc may be made of the same or a different metal, but may advantageously be made of a carbon-fibre material which is moulded around the spindle connector 7.

The discs 1, 3 may be planar or may be angled or curved, or may be lenticular with the outer surface being convex and the inner surface being planar. The inner and/or outer surfaces of the discs may be smooth or may be dimpled to create a turbulent boundary layer adjacent to the disc surface.

One or more pedal connectors 9 is provided in a peripheral region of each of the discs 1,3. In the case of a carbon-fibre disc the or each pedal connector is moulded into the carbon-fibre material and may be made of metal, such as steel, titanium or an aluminium alloy, otherwise the pedal connector(s) may simply be in the form of a threaded aperture or aperture of any other suitable configuration.

As shown in the figure, four pedal connectors may be provided, but a fewer or greater number may be provided as required. The pedal connectors are distributed substantially uniformly around a peripheral region of the disc. This allows for multiple positions for the pedals. In particular, the various connectors can be positioned at different distances from the centre of the disc to provide a range of crank lengths, for example for training and competition, withoutthe need to replace the entire crank arm (that is, only needing to remove and replace the pedals in different pedal connectors 9). No modifications need to be made to the bicycle itself.

The discs 1, 3 have several advantages over conventional crank arms. The discs are stronger and more rigid than conventional crank arms and permit greater acceleration and the bicycle is more balanced because the weight of the cranks is consistent throughout each rotation instead of creating a wobble as with conventional crank arms because of the constant opposing shift in weight.

The discs are more aerodynamic than conventional crank arms because the disc travels smoothly through the air and does not repeatedly break through the air as is the case with conventional crank arms. Also, the discs improve the air flow around the frame of the bicycle from the front of the bicycle to the rear thereof, thus reducing the overall drag coefficient of the bicycle when in use. There is a safety consideration too, in that in crash situations the disc 1 on the chain side prevents the rider's body or clothing becoming caught in the teeth of the chainring or in the chain itself in the region of the chainring.

Clearly, the discs 1, 3 do not need to be circular and could have other configurations, such as oval, square or star-shaped, and the surface does not need to be continuous and could be discontinuous, for example in that apertures could be provided. However, the ideal shape is circular and the ideal surface is continuous.

Claims

<claim-text>CLAIMS1. A bicycle crank comprising a substantially planar member including means for receiving a bicycle pedal and means for attaching to a spindle for rotation relative thereto.</claim-text> <claim-text>2. A bicycle crank as claimed in claim 1, wherein the crank is in the form of a disc.</claim-text> <claim-text>3. A bicycle crank as claimed in claim 1, wherein the crank is in the form of C\J an oval, square or star. r</claim-text> <claim-text>4. A bicycle crank as claimed in claim 1, 2 or 3, wherein the crank has a substantially continuous surface.</claim-text> <claim-text>5. A bicycle crank as claimed in claim 1, 2 or 3, wherein the crank has a discontinuous surface.</claim-text> <claim-text>6. A bicycle crank as claimed in claim 5, wherein apertures are provided in the crank.</claim-text> <claim-text>7. A bicycle crank as claimed in any preceding claim, wherein the spindle connector is made of metal.</claim-text> <claim-text>8. A bicycle crank as claimed in claim 7, wherein the spindle connector is made of steel, titanium or an aluminium alloy.</claim-text> <claim-text>9. A bicycle crank as claimed in any preceding claim, wherein the substantially planar member is made of carbon-fibre material.</claim-text> <claim-text>10. A bicycle crank as claimed in any one of claims 1 to 8, wherein the substantially planar member is made of a metal.</claim-text> <claim-text>11. A bicycle crank as claimed in claim 10, wherein the substantially planar (\J member is made of steel, titanium or an aluminium alloy. r</claim-text> <claim-text>12. A bicycle crank as claimed in any preceding claim, wherein the means for receiving a pedal is made of a metal.</claim-text> <claim-text>13. A bicycle crank as claimed in claim 12, wherein the means for receiving a pedal is made of steel, titanium or an aluminium alloy.</claim-text> <claim-text>14. A bicycle crank as claimed in any preceding claim, wherein the substantially planar member is planar.</claim-text> <claim-text>15. A bicycle crank as claimed in any one of claims 1 to 13, wherein the substantially planar member is angled.</claim-text> <claim-text>16. A bicycle crank as claimed in any one of claims 1 to 13, wherein the substantially planar member is curved.</claim-text> <claim-text>17. A bicycle crank as claimed in any one of claims 1 to 13, wherein the substantially planar member is lenticularwith the outer surface being convex and the inner surface being planar.</claim-text> <claim-text>18. A bicycle crank as claimed in any preceding claim, wherein one or both of the surfaces of the substantially planar member is smooth.(\J 19. A bicycle crank as claimed in any one of claims 1 to 17, wherein one or r both of the surfaces of the substantially planar member is dimpled.0) 20. A bicycle crank as claimed in any preceding claim, wherein the crank is provided with a plurality of means for receiving a pedal.21. A bicycle crank as claimed in claim 20, wherein the crank is provided with four means for receiving a pedal.22. A bicycle crank as claimed in claim 20 or 21, wherein the plurabty of pedal receiving means is distributed substantially uniformly around a peripheral region of the substantially planar member.23. A bicycle crank as claimed in claim 20, 21 or 22, wherein the receiving means are provided at different distances from an axis of the spindle connector.24. A bicycle crank substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.25. A pair of bicycle cranks, each crank as claimed in any preceding claim.26. A pair of bicycle cranks as claimed in claim 25, wherein one of the cranks is secured to a chainring. (4 r27. A pair of bicycle cranks substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings. 0)</claim-text>