Wheel and spoke for a bicycle that is at least partially muscle-powered

Abstract

Spoke (1) with a spoke body (2) for a wheel (101, 102) of a bicycle (100) that is at least partially muscle-powered, wherein the spoke body (2) has a hub-side first end (3) and a rim-side second end (4), wherein the two ends (3, 4) are spaced apart from each other, and wherein the spoke body (2) is elongated and has at least one first central region (12) arranged closer to the first end (3) than to the second end (4) and at least one second central region (13) arranged closer to the second end (4) than to the first end (3), wherein the spoke body (2) has in the first central region (12) and in the second central region (13) of the spoke body (2) a flattened cross-section (42, 43) which is essentially accommodated in a longitudinal plane (6), characterized by that in the second central region (13) the spoke body (2) is more asymmetrically formed than in the first central region (12).

Description

[0001] The present invention relates to a spoke and a wheel equipped with at least one such spoke for a bicycle that is at least partially muscle-powered.

[0002] Aerodynamics plays a crucial role in vehicles in general, and especially in those that are at least partially muscle-powered, as wind resistance has the greatest impact on the power required for propulsion as speed increases. To reduce the wind resistance of bicycles, enclosed wheels have become popular, offering significantly reduced wind resistance. However, such enclosed wheels have the disadvantage that considerable crosswind forces act upon them, which can make steering a two-wheeler considerably more difficult. Therefore, enclosed disc wheels are not commonly used for road bicycles.

[0003] On spoked wheels, the spokes contribute significantly to wind resistance. Standard round spokes do not offer optimal aerodynamic drag. Therefore, so-called bladed spokes have become popular; these have a flat cross-section in the direction of travel and thus help to reduce wind resistance.

[0004] US 2005 / 0173971 A1 discloses a spoke or a wheel with the features of the respective preamble of claims 1 and 17, respectively.

[0005] It is therefore the object of the present invention to provide a wheel equipped with spokes and, in particular, a spoke that is easy to manufacture for such a wheel, thereby enabling an improved reduction of wind resistance.

[0006] This problem is solved by a spoke having the features of claim 1 and by a wheel having the features of claim 17. Preferred embodiments are the subject of the dependent claims. Further advantages and features of the present invention will become apparent from the general description and from the description of the exemplary embodiment.

[0007] A wheel according to the invention is intended for use on a bicycle that is at least partially muscle-powered and comprises a hub and a rim. The hub is connected to the rim via a plurality of spokes. At least one of the spokes has a spoke body with two ends located apart from each other, namely a first end on the hub side and a second end on the rim side.

[0008] The first end, or hub end, is connected to the hub, and the second end, or rim end, is connected to the rim.

[0009] The spoke body is elongated and has at least one first central section located closer to the first end than to the second end, and at least one second central section located closer to the second end than to the first end. Multiple (different) central sections are also possible.

[0010] The spoke body has a flattened cross-section in both its first and second central sections, essentially in a longitudinal plane. The cross-sections differ from each other.

[0011] In the second central area, the spoke body is more asymmetrically formed than in the first central area.

[0012] In a preferred embodiment, when the wheel is in its operational state, the forward-facing longitudinal half of the spoke in the second central section of the uppermost spoke is wider than the rearward-facing longitudinal half. This results in a teardrop shape that is particularly aerodynamically efficient.

[0013] A spoke according to the invention comprises a spoke body for a wheel of a bicycle that is at least partially muscle-powered. The spoke body has a hub-side first end and a rim-side second end, the two ends being spaced apart. The spoke body is elongated and has at least one first central region arranged closer to the first end than to the second end, and at least one second central region arranged closer to the second end than to the first end.

[0014] The spoke body has a flattened cross-section in both its first and second central sections, essentially in a longitudinal plane. In the second central section, the spoke body is more asymmetrical than in the first.

[0015] The invention has many advantages. The wheel and spokes according to the invention offer numerous benefits, as the spoke significantly reduces wind resistance. An optimal shape can be achieved at maximum speed. Manufacturing is simple and cost-effective.

[0016] Radially further inwards, during operation, speed constellations occur at the spoke where an overall teardrop-shaped spoke can be disadvantageous. Here, a longitudinally symmetrical (front / back) spoke offers advantages, as it exhibits better properties at the locally occurring negative speeds.

[0017] According to the invention, the first or hub-side end of the spoke body is provided for being connected to the hub and the second or rim-side end of the spoke body is provided for being connected to the rim.

[0018] The “hub-side end” can also be referred to as “first end” or “first hub-side end” or “hub-side first end” and refers in each case to the end of the spoke body facing the hub and attached there.

[0019] The “rim-side end” can also be referred to as “second end” or “second rim-side end” or “rim-side second end” and refers in each case to the end of the spoke body facing the rim and attached there.

[0020] For the purposes of this application, a flattened cross-section means, in particular, that the spoke body has a thickness transverse to the longitudinal plane over at least the first and second central regions that is less than the longitudinal extent of the spoke body in the circumferential direction of the wheel when installed. Transverse to the longitudinal plane means transverse to the wheel.

[0021] In all embodiments, it is possible for a multitude of adjoining central areas to be provided, with a continuous, stepped, or quasi-continuous change in the local cross-section. For example, the radial (almost) inner section of the spoke body may have a cross-section that is symmetrical in both the longitudinal and transverse directions, while the radial (almost) outer section may have a (nearly or completely) teardrop-shaped cross-section.

[0022] In preferred further developments, the spoke body in the first central area has a cross-section of a first cross-sectional type, which is essentially axially symmetric to a longitudinal extension and a transverse axis.

[0023] The longitudinal axis extends through the greatest length and the transverse axis (perpendicular to the wheel) through the greatest thickness of the spoke body.

[0024] Preferably, the spoke body in the second central region has a cross-section of a second cross-sectional type, which is essentially axially symmetrical to a longitudinal extent and which is thicker on average in the first longitudinal half than in the second longitudinal half. In the installed state, this means, in particular, that the uppermost spoke in the second central region is thicker towards the front of the bicycle than towards the rear. In particular, the second cross-sectional type is teardrop-shaped.

[0025] Preferably, the first cross-sectional type is (essentially) elliptical. Such a cross-section offers the advantage that the same flow resistance is present during (relative) forward and backward movements, which is not the case with a teardrop shape.

[0026] In all configurations, many adjoining intermediate areas can be provided. It is also possible that only a few or only two intermediate areas are provided, between which (each) a transition area is formed with a continuous or stepped transition between the (each) first and the (each) second (or subsequent) intermediate area.

[0027] Preferably (in the case of two middle sections) the height of the first middle section is between 1 / 5 and 2 / 3 of the spoke height (length from the first end to the second end).

[0028] A height of the second central section is particularly preferred, being between 1 / 5 and 2 / 3 of the spoke height.

[0029] In all embodiments, it is preferred that the surface of the spoke body is smooth. The surface of the spoke body is preferably polished.

[0030] It is possible that at least one central region has a constant cross-section along its length. However, it is also possible that the cross-section changes along the length of a central region.

[0031] Preferably, the spoke body has a first end section at the hub-side end and / or a second end section at the rim-side end. The first and / or second end section is preferably round. A spoke head may be formed on the first end section. The spoke head may be round, but is preferably flattened. This allows the spoke head to provide anti-rotation protection when it rests against a flat surface.

[0032] In all embodiments, it is preferred that the flattened cross-section fits at least substantially (or completely) into the round cross-section. This means that the largest dimension of the flattened cross-section is no more than 10% or 20% larger than the diameter of the round cross-section. Such an embodiment is possible if the flattened cross-sections are incorporated into a thinner segment of the spoke in the central areas, for example, if the spoke body has been tapered in the central areas before stamping, for instance, by mechanical processing or drawing, etc. For example, the spoke body can be tapered in the central areas from a diameter of 2.0 mm to 1.5 mm before stamping.

[0033] When riding a bicycle, the wheel, equipped with such a spoke, rolls along the ground or road. At the lowest point of the wheel, the relative velocity to the surrounding air or ground is zero. At the highest point of the wheel, or at the highest point of the uppermost spoke, the relative velocity is essentially twice the actual speed of travel relative to the surrounding air. Therefore, by shaping the cross-section in the outer central area, for example, into a teardrop shape, the outer second central area, which is subject to particularly high circumferential and relative velocities, is formed more aerodynamically than in the prior art, thus achieving a significantly reduced air resistance.

[0034] Simultaneously, in the central area of ​​the impeller, i.e., the first middle section located closer to the hub, deterioration is avoided because locally negative relative velocities perpendicular to the spoke surface exist there. Negative relative velocities prevent negative effects. A teardrop shape is only advantageous in one flow direction. Overall, the wind resistance of an impeller equipped with this design is reduced compared to a conventional impeller.

[0035] In the wheel according to the invention, the hub is connected to the hub-side end of a plurality of the spokes, and the rim is connected to the rim-side end of the plurality of the spokes. This is very advantageous because the flattened and more teardrop-shaped cross-section in the second central region is arranged radially further outwards than the first central region, which has a preferably elliptical cross-section.

[0036] Air resistance increases quadratically with the relative speed between the spoke and the air. Therefore, the improved teardrop shape positioned radially further outwards significantly reduces overall air resistance.

[0037] A wheel with such spokes is aerodynamic where required, and further inwards it has a shape where relative negative speeds have no adverse effect, since it has a point-symmetrical shape.

[0038] Preferably, the cross-sectional areas in the central regions are reduced compared to the cross-sectional areas at the ends. This results in a lower overall weight of the spokes and the wheel.

[0039] In all embodiments, it is particularly preferred that the flattened cross-section of the spoke bodies is aligned substantially parallel to a plane spanned by the rim. "Substantially parallel" within the meaning of the present invention also includes a certain inclination of, for example, preferably up to 10°, or particularly up to 20°, or possibly even up to 30° to the longitudinal direction. A certain inclination is normal and often desirable.

[0040] In any case, it is ensured that the central areas with the flattened cross-section are (essentially) aligned in the plane of travel, thus reducing wind resistance and not increasing it. An increase could occur if the flattened area were oriented completely or substantially perpendicular to the direction of travel of a bicycle equipped with such a wheel.

[0041] In all embodiments, it is preferred that the flattened cross-section is aligned completely within or parallel to the longitudinal plane. However, it is also possible that the flattened cross-section of the spoke body in the first central region does not extend completely within or parallel to the longitudinal plane, for example, if the first central region has a slight curvature or is very slightly helical. In all cases, the flattened region does not extend transversely to the longitudinal plane, but at most within a range of ±30°, and in particular ±20°, and preferably ±10°, relative to the longitudinal plane. It is particularly preferred that at least one longitudinal edge of the flattened cross-section is parallel to the longitudinal plane, within the limits of the manufacturing accuracy of the spoke body.

[0042] In a preferred embodiment of the wheel or spoke, the spoke body has a constant cross-section over at least one longitudinal section. This longitudinal section is selected from a group of longitudinal sections comprising the first end section and the second end section, and optionally the first central section and the second central section.

[0043] In the context of the present invention, a constant cross-section is understood to mean a substantially constant cross-section. This means that small cross-sectional changes of, for example, less than 10% and, in particular, less than 5% along the length of the longitudinal section are disregarded and are still considered a constant cross-section. Preferably, cross-sectional changes along the length of the longitudinal section are within a dimensional range of less than 5% and, in particular, less than 2%.

[0044] At least one end section, and preferably both end sections, are preferably short in the longitudinal direction of the spoke body. Preferably, all end sections are shorter than 30 mm, and in particular shorter than 25 mm, 20 mm, or 15 mm.

[0045] Preferably, the length of at least one transition region and preferably of all transition regions is smaller than the length of at least one and, in particular, the shortest end section.

[0046] In all embodiments, it is preferred that the flattened cross-section in the first and second central regions (and further central regions) is achieved by embossing. The spoke according to the invention is easy to manufacture. The cross-section can also be created by other means.

[0047] In preferred embodiments, the first end section and the second end section have identical cross-sections. "Identical cross-sections" within the meaning of the present invention means that the cross-sectional shapes are the same, although it is possible for the individual end sections to have different cross-sectional dimensions. Particularly preferably, the first end section and the second end section have identical cross-sections. In particularly preferred embodiments, the cross-sections of at least the first end section and the second end section are each round, and in particular, substantially round.

[0048] In particularly preferred embodiments, the spoke is manufactured from an originally round or essentially round profile, wherein the central areas are tapered, in particular by a drawing process or local hammering and / or a cold forging process and / or another machining step or process, so that after the drawing process or machining process there are two end sections with larger diameters and, for example, a homogeneous central area with a reduced diameter.

[0049] The center can then be embossed, creating central sections with a flattened cross-section. This results in two end sections, preferably with identical cross-sections, and a first and second tapered central section, both with a flattened cross-section. Such a manufacturing process is simple and very cost-effective.

[0050] However, it is also possible that the spoke is not made from a round original profile, but from an oval, angular or other cross-sectional profile.

[0051] Preferably, the flattened cross-section in the second central region has a cross-sectional shape that is at least approximately wing-shaped with rounded corners. The first central region preferably has an oval and / or (multi-)angular and / or elliptical shape.

[0052] In particularly preferred embodiments, the spoke body has an external thread and / or a fastening means with an external thread at at least one of its two ends in order to connect the spoke body to the rim and / or the hub.

[0053] Preferably, the spoke body has a spoke head at at least one of its two ends to connect the spoke body to the hub and / or the rim via the spoke head. The spoke head can be rotationally symmetrical, mirror-symmetrical, or point-symmetrical. For example, the spoke head can be hemispherical or spherical. A T-shaped design of the spoke head is also possible.

[0054] In particular, the spoke head is T-shaped and / or features a "T-head". This T-shaped spoke head allows the spoke to be securely attached to or within the hub, preventing it from twisting. This ensures the correct and, in particular, optimal alignment of the spoke relative to the direction of rotation.

[0055] Preferably, the wheel is equipped with at least one spoke, as described above.

[0056] Overall, the invention provides an advantageous spoke and an advantageous wheel, with which a particularly low wind resistance can be achieved.

[0057] Further advantages and features of the present invention will become apparent from the exemplary embodiments, which are explained below with reference to the accompanying figures.

[0058] The figures show: Fig. 1 a schematic side view of a mountain bike; Fig. 2 a schematic side view of a racing or touring bicycle; Fig. 3 a schematic side view of a spoke according to the invention along the longitudinal plane; Fig. 4 a schematic cross-sectional view of the spoke made of Fig. 3; Fig. 5 a schematic side view of another spoke according to the invention along the longitudinal plane; and Fig. 6 a schematic cross-sectional view of the spoke Fig. 5.

[0059] Fig. Figure 1 shows a schematic representation of a mountain bike as a bicycle or two-wheeler 100. The bicycle has two wheels 101, 102, namely a front wheel 101 and a rear wheel 102. Furthermore, a frame 103, a suspension fork 104, a rear shock absorber 105, handlebars 106, and a saddle 107 are provided. Pedals and, in this case, a derailleur system are provided as the drive mechanism 112. The front wheel 101 and the rear wheel 102 are each attached to dropouts 113 on the fork 104 and the frame 103, respectively.

[0060] Fig. Figure 2 shows a highly schematic side view of a racing or touring bicycle as a two-wheeler 100, wherein the bicycle again has a front wheel 101 and a rear wheel 102 according to the invention as wheels. The wheels are attached to the dropouts 113. The front wheel and the rear wheel 101, 102 each have a rim 110 and spokes 1 according to the invention. Due to the scale of the illustration, the spokes 1 are only shown schematically and are discussed in detail below with reference to the other figures.

[0061] Wheels 101 and 102 in the Fig. 1 and Fig. Each of the two spokes has a plurality of spokes. The spokes are connected to the hub 108 at their first or hub-side ends 3 and to the rim 110 at their second or rim-side ends 4.

[0062] In Fig. 3 and Fig. Figure 4 shows a spoke 1 of a wheel 101 or 102 according to the invention in a longitudinal view and in a side view.

[0063] Fig. Figure 3 shows a schematic view of a spoke 1 in the direction of travel, not to scale, particularly in the longitudinal direction 5. The longitudinal plane 6 extends transversely to the plane of representation, along which a bicycle 100 equipped with such a spoke is moved.

[0064] The spoke 1 has a spoke head 10 at the hub-side end 3 and an external thread 9 at the rim-side end 4, which is for screwing into a [partially specified] Fig. 3 spoke nipples not shown.

[0065] The first or hub-side end 3 of the spoke body 2 is attached to the hub 108 and the spoke body 2 extends from the hub 108 outwards to the second or rim-side end 4, where the external thread 9 is then attached to the rim 110 with a spoke nipple (not shown).

[0066] The spoke body 2 has a first end section 11 adjacent to the first or hub-side end 3, a first central section 12, a second central section 13, and a second end section 14. A transition section 51 is provided between the first end section 11 and the first central section 12. A transition section 53 is arranged between the second central section 13 and the second end section 14. A transition section 52 may be provided between the first central section 12 and the second central section 13. Multiple central sections or a continuous transition are also possible.

[0067] It is also possible to equip the spoke 1 with fastening means other than spoke heads and threads at the end sections 11 and 14, or to attach the spoke to the hub or the rim using other suitable fastening means. Preferably, however, the spoke 1 has a spoke head at the hub-side end and an external thread at the rim-side end.

[0068] The first end section 11 and the second end section 14 each have round cross-sections 41 and 44, respectively. The cross-sections 41 and 44 are preferably identical. This means that the thickness 21 of the first end section 11 is essentially the same as the thickness 24 of the second end section 14.

[0069] In comparison, the first mid-section thickness 22 at the first mid-section 12 is significantly lower. In a specific example, the first end-section thickness 21 is 2.0 mm, as is the second end-section thickness 24 at the second end-section 14. The first mid-section thickness 22 in the first mid-section 12, however, can be only 1.0 or approximately 1.2 mm.

[0070] The exemplary embodiment according to the Fig. 5 and Fig. 6 essentially corresponds to the embodiment shown in the Fig. 3 and Fig. 4. One difference is that the central sections 12 and 13 were made thinner before embossing, so that the end section thickness 21 is also 2.0 mm there, while the central section thickness 22 and 23 was reduced to 1.5 mm before the final shaping. Therefore, in the Fig. 5 and Fig. 6. The thickness and width of the central areas are correspondingly smaller than in the embodiment according to the Fig. 3 and Fig. 4.

[0071] In Fig. 3 and Fig. 4 the middle area thickness 22 is approximately 1.0 to 1.2 mm and the first and second middle area widths are approximately 3.2 to approximately 5 mm.

[0072] In Fig. 5 and Fig. In contrast, the thickness of the middle section 22 and 23 is approximately 0.6 to 0.8 mm, and the width of the first and second middle section is approximately 2.8 to approximately 4 mm.

[0073] In the second central section 13, which is located closer to the second end section 14 than the first central section 12, the second central section 13 has a significantly different cross-section 43. The cross-section is approximately teardrop-shaped, with the thicker end of the teardrop pointing in the direction of travel.

[0074] In the first central section 12, closer to the hub, lower maximum relative velocities to the ambient air occur. The cross-section 42 in the first central section 12 is therefore more symmetrical than in the second central section 13. The cross-section 42 is symmetrical with respect to the longitudinal plane 6 and the transverse direction 68, such that the front end of the spoke in the direction of travel and the rear end of the spoke are identically shaped.

[0075] The second central section 13 is located further out and, at its upper end, is exposed to almost twice the vehicle's speed as a relative velocity between the spoke and the surrounding air. Since the bicycle's wind resistance does not increase linearly with the relative speed, but quadratically, and the required power increases cubically, the particularly aerodynamic design of the second central section contributes significantly to reducing air resistance.

[0076] In the radially inner region, the prevailing relative velocity (perpendicular to the spoke surface) can even become less than zero. Therefore, a teardrop-shaped design is actually disadvantageous there, as negative relative velocities also occur, which are particularly detrimental to a teardrop shape. Here, a symmetrical and especially point-symmetrical cross-section offers considerable advantages, since wind resistance is quite low for both positive and negative velocities.

[0077] Also shown are in Fig. Figure 3 hatches the respective cross-sectional shapes in the respective sections or areas. It is clearly recognizable that the first end section 11 has a substantially round cross-section 41. The cross-section 44 in the second end section 14 is also substantially round.

[0078] In contrast, the cross-sections 42 and 43 in the first and second central areas 12, 13 are flattened, as can be seen from the dashed lines drawn in the cross-sections 42 and 43.

[0079] Fig. Figure 4 shows a schematic side view of spoke 1. Fig. 3, whereby the rounded end sections 11 and 14 result in an essentially identical view.

[0080] The view of the first and second central sections 12 and 13 differs considerably, as the flattened cross-sections 42, 43 of the first and second central sections 12, 13 are shown from the side. While in the first end section 11, due to the rounded shapes, the first end section thickness 21 corresponds to the first end section width 31, and in the second end section 14, the second end section thickness 24 corresponds to the second end section width 34, the (first) second central section width (32) 33 deviates considerably from the (first) second central section thickness (22) 23. In the exemplary embodiment, the central section widths 32, 33 are up to 5 mm and can thus be more than twice as large as the first or second central section thickness 22, 23, which is approximately 1 to 1.2 mm.

[0081] In transition areas 51 and 53, there is a gradual transition between the respective sections or areas.

[0082] The transition areas 51 and 53 are considerably shorter in the longitudinal direction 5 of the spoke body 2 than the central areas 12 and 13 and also shorter than the end sections 11 and 14.

[0083] If two separate central areas 12 and 13 are formed, a transition area 52 can be provided between them, which has a length of, for example, 5 mm to 10 mm. A continuous transition is also preferred.

[0084] Fig. 5 shows a longitudinal view and Fig. Figure 6 shows a side view of another spoke 1, which was manufactured from a starting material that had been previously reduced in thickness in the middle. The length 15 of the second central section 13 with the flattened and approximately teardrop-shaped cross-section 43 preferably lies between about 2 / 3 and about 1 / 3 of the length 8 of a spoke body 2. In a specific embodiment, the second central section 15 has slightly more than half the length of the entire spoke body 2. The design is basically as in Fig. 3 and Fig. 4.

[0085] The length 8 of the entire spoke 1, i.e., from end section 11 to end section 14, depends on the application and installation situation. In a specific case, the length 8 of the spoke body is 290 mm, but can be up to, for example, 10% or 20% shorter or longer depending on the rim and installation position, etc.

[0086] The cross-section 41 from the first end section 11 is also shown as a dashed line in the figures. From the originally longitudinally homogeneous body, a machining operation or, for example, a drawing operation is produced in which a body has a reduced cross-section in the central regions 12 and 13, while the original diameter is retained in the first end section 11 and the second end section 14. Subsequently, the spoke body 2 is stamped in the first and second central regions 12, 13, resulting in the flattened cross-section 42, 43.

[0087] Overall, the invention offers significant advantages. While the drag coefficient of cross-sectional shapes such as circles and ellipses is the same for an airflow from the right and left, for a streamlined profile, the direction of the airflow is crucial. The power required by a body to overcome drag is disproportionately dependent on speed. The resistance that the rider must overcome while riding consists of several components. At higher speeds, the largest component is air resistance, which in turn comprises a rotational and a translational component.

[0088] The movement of the rider and the non-rotating part of the bicycle is simply a displacement in the direction of travel. The movement of the wheels, however, is a combination of rotation and translation. Therefore, two forms of air resistance occur for the wheels: translational and rotational air resistance.

[0089] Rotational air resistance arises from compressive forces on the spokes and frictional forces on the surfaces of the tire, rim, spokes, and hub. The product of these forces and their distance from the wheel's axis of rotation produces a resistance torque that slows the wheel's rotation. The surface friction on the rim, as part of the rotational air resistance, acts similarly to a slightly rubbing brake.

[0090] The speed of a point on the wheel depends on its distance from the wheel as well as the angular velocity of the wheel.

[0091] The instantaneous center of rotation is at a distance of zero. Consequently, its velocity is also zero. Since this point is twice as far from the instantaneous center of rotation as the hub axis, the velocity at the highest point of the wheel is twice the vehicle's speed. The velocity profile between the highest and lowest points of the wheel is proportional to the distance from the instantaneous center of rotation – that is, linear.

[0092] If, in the next step, arbitrary points on the spokes that lie between the horizontal and vertical spokes are considered, the following becomes apparent: if the side in which the upper vertical spoke moves is defined as the front ("V" in the figure), then the spoke under consideration in the upper half of the wheel also moves in the direction of its front, while the speed in an area of ​​the lower half of the wheel points in the direction of its trailing edge.

[0093] The result is that, depending on where the spoke is located, it moves in the direction of its front or back.

[0094] Or, to put it another way: On the lower half of the wheel, there is an area where the direction of movement of the spokes reverses.

[0095] Since a wheel rotates continuously, every position of the spoke is equally important. The velocity profile for each point on the spoke follows a sine function. The highest velocity occurs for each point on the spoke when the spoke is in its upper vertical position (0°), and the highest negative velocity when the spoke is in its lower vertical position (180°). Because the velocity depends on the distance from the instantaneous center of rotation, the maximum positive and negative velocities differ for various points on the spoke. A point at the end of the spoke closest to the rim is far from the instantaneous center of rotation when the spoke is in its upper vertical position—therefore, the velocity is very high. Conversely, if the lower vertical spoke is considered, this point is only a short distance away, namely the height of the tire and rim.The speed is therefore very low here. A point at the end of the spoke near the hub represents the other extreme: its distance to the pivot point changes only slightly because it rotates around the hub on a much smaller circle. The maximum positive and negative speeds are therefore of a similar order of magnitude.

[0096] For symmetrical bodies, the drag does not depend on whether the body is approached from the right or left. However, if a body is symmetrical in only one direction, the direction of the flow makes a difference.

[0097] Near the hub, similarly large positive and negative airspeeds occur. The profile should therefore have a similarly aerodynamic efficiency on both sides. Near the rim, however, the highest positive airspeed is many times greater than the highest negative airspeed. Improving the shape for positive airflow is therefore advantageous overall. Since airspeed is cubed in the aerodynamic power requirement, aerodynamic efficiency in the direction of positive airspeed is significantly more important than in the direction of negative airspeed.

[0098] In the hub area, positive and negative speeds are of a comparable magnitude. Here, it is advantageous if the aerodynamics of the spoke cross-section function equally well from both directions. In the rim area, however, the maximum positive speed is significantly greater than the maximum negative speed. It is considerably beneficial if one direction becomes more aerodynamically efficient – ​​even if the other direction becomes less efficient.

[0099] It turns out that the greatest negative velocities occur for points near the hub. These points – considering only the range of negative velocities – have the greatest distance from the instantaneous center of rotation.

[0100] As with any body, the flow resistance of a spoke is also divided into pressure resistance and frictional resistance. The latter depends primarily on the size and roughness of the spoke surface.

[0101] It is advantageous if the spoke profile near the hub has similar aerodynamic properties for both positive and negative speeds. For this reason, a symmetrical cross-section is preferably chosen for this end of the spoke.

[0102] At the end of the spoke facing the rim, optimizing the cross-sectional shape for positive airflow is advisable. For this reason, a uniaxially symmetrical profile is chosen. A NACA aero airfoil can serve as the basis for this shape design.

[0103] Since the velocity profile (perpendicular to the spoke) between the two ends of the spoke is linear, a linear profile of the cross-sectional shape is preferably also chosen.

[0104] Advantageously, a spoke has a spoke body with a biaxially symmetrical profile near the hub and a uniaxially symmetrical profile near the rim. A linear transition between the profiles at the two ends of the spoke is preferred. Preferably, a constant cross-sectional area is maintained along the length of the spoke (at least in the middle). Reference symbol list: 1 spoke 2 spoke bodies 3 hub-side, first end 4 rim-side, second end 5 Longitudinal direction 6 Longitudinal plane 7 Longitudinal section 8 Length of 2 9 threads 10 spoke head 11 first final section 12 first middle range 13 second middle area 14 second final section 15 Length of 13 21 first end section thickness 22 first mid-range thickness 23 second mid-range thickness 24 second end section thickness 31 first end section width 32 first mid-range width 33 second mid-range width 34 second end section width 41 Cross section 42 Cross section 43 Cross section 44 Cross section 51 Transition area 52 Transition area 53 Transition area 62 Cross-section type 63 Cross-section type 64 first longitudinal half 65 second longitudinal half 66 first thickness 67 second thickness 68 Transverse axis 69 Thickness 100 Two-wheeler, bicycle 101 Wheel, front wheel 102 Wheel, rear wheel 103 frames 104 Fork 105 dampers 106 handlebars 107 saddles 108 hub 109 spoke 110 rim 111 Brake disc 112 Drive 113 breakdowns

Claims

[1] Spoke (1) with a spoke body (2) for a wheel (101, 102) of a bicycle (100) that is at least partially muscle-powered, wherein the spoke body (2) has a hub-side first end (3) and a rim-side second end (4), wherein the two ends (3, 4) are spaced apart from each other, and wherein the spoke body (2) is elongated and has at least one first central region (12) arranged closer to the first end (3) than to the second end (4) and at least one second central region (13) arranged closer to the second end (4) than to the first end (3), wherein the spoke body (2) has in the first central region (12) and in the second central region (13) of the spoke body (2) a flattened cross-section (42, 43) which is essentially accommodated in a longitudinal plane (6), characterized by , that in the second central region (13) the spoke body (2) is more asymmetrically formed than in the first central region (12). [2] Spoke according to claim 1, wherein the spoke body (2) has in the first central region (12) a cross-section (42) of a first cross-sectional type (62) which is substantially axially symmetric to a longitudinal extent and a transverse axis (68). [3] Spoke according to one of the preceding claims, wherein the spoke body (2) in the second central region (13) has a cross-section (43) of a second cross-sectional type (63) which is substantially axially symmetric to a longitudinal extent and which is thicker on average in a first longitudinal half (64) than in the second longitudinal half (65). [4] Spoke according to one of the preceding claims, wherein the second cross-sectional type (73) is teardrop-shaped. [5] Spoke according to one of the preceding claims, wherein the first cross-sectional type (72) is elliptical [6] Spoke according to one of the preceding claims, wherein a transition area (52) is formed with a continuous or stepped transition between the first and the second central area (12, 13). [7] Spoke according to one of the preceding claims, wherein a plurality of intersecting central regions (12, 13) are formed. [8] Spoke according to one of the preceding claims, wherein the height of the first central region (12) is between 1 / 5 and 2 / 3 of the spoke height. [9] Spoke according to one of the preceding claims, wherein the height of the second central region (13) is between 1 / 5 and 2 / 3 of the spoke height. [10] Spoke according to one of the preceding claims, wherein a surface of the spoke body (2) is polished. [11] Spoke according to one of the preceding claims, wherein a constant cross-section is present over at least one central region (12, 13). [12] Spoke according to one of the preceding claims, wherein the spoke body (2) has a first end section (11) at the hub-side first end (3) and a second end section (14) at the rim-side second end (4). [13] Spoke according to the preceding claim, wherein at least one of the end sections (11, 14) has a round cross-section (41, 44). [14] Spoke according to one of the preceding claims, wherein the flattened cross-section (42, 43) fits into the round cross-section (41, 44). [15] Spoke according to one of the preceding claims, wherein the spoke body (2) has an external thread (9) at the rim-side end (4) and / or wherein the spoke body has a spoke head (10) at the hub-side end (3). [16] Spoke according to one of the preceding claims, wherein the spoke head (10) is T-shaped. [17] Wheel (101, 102) of a bicycle (100) that is at least partially muscle-powered, comprising a hub (108) and a rim (110), wherein the hub (108) is connected to the rim (110) via a plurality of spokes (1), wherein at least one of the spokes (1) has a spoke body (2) with two ends (3, 4) that are far apart from each other, namely a hub-side first end (3) and a rim-side second end (4), wherein the hub-side end (3) is connected to the hub (108) and wherein the rim-side end (4) is connected to the rim (110), wherein the spoke body (2) is elongated and has at least one first central region (12) arranged closer to the first end (3) than to the second end (4) and at least one second central region (13) arranged closer to the second end (14) than to the first end (3), wherein the spoke body (2) has in the first central region (12) and in the second central region (13) of the spoke body (2) a flattened cross-section (42, 43) which is essentially accommodated in a longitudinal plane (6), characterized by , that in the second central region (13) the spoke body (2) is more asymmetrically formed than in the first central region (12). [18] Wheel according to claim 17, wherein in the ready-to-use state, in a cross-section in the second central area of ​​the uppermost spoke, the longitudinal half (64) oriented towards the front is wider than the longitudinal half (65) oriented towards the rear.

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