Bicycle wheel HUB with dual damped synchronization

Abstract

The invention discloses a bicycle wheel hub architecture comprising a main axle (6) surrounded by a shaft sleeve (1) carrying an axle bearing (2) that supports rotation of a hub shell (7) together with a second hub bearing (14) which is positioned radially in a freehub body (15) enabling the hub shell (7) to rotate freely about the main axle (6); a brake‑side dropout spacer (3), a cassette‑side dropout spacer (17) and a spacer sleeve (16) for axial positioning; a cassette (18) secured by a cassette lockring (19); and a retaining ring (13) for axial retention; wherein the freehub body (15) couples inner (10) and outer (9) synchronization rings to a fixed toothed ring (8) which is mechanically fastened to the hub shell (7), and wherein a mechanical engagement is produced by axial motion of a set of outer (11) and inner (12) bellows along the shaft sleeve (1).

Description

BICYCLE WHEEL HUB WITH DUAL DAMPED SYNCHRONIZATION

[0001] The invention discloses a bicycle wheel hub architecture that shortens engagement response time and suppresses engagement noise. The bicycle rear wheel hub is suitable for any bicycle type—irrespective of discipline or power source (electric, pedal‑assist, or purely mechanical). The internal mechanism doubles the number of engagements points relative to conventional hubs and operates quietly thanks to damping during freewheeling.

[0002] Document US 8,312,976 B2 describes a straightforward synchronization mechanism made essentially of two components: pawls and a toothed ring.

[0003] Document US 11,400,754 B2 and US 8,757,341 B2 discloses synchronization systems with high torque‑transmission efficiency. Those solutions employ two toothed rings, which mitigate stress concentrations compared with the pawl‑and‑ring architecture noted above. In US 11,400,754 B2 the rings are biased by a single helical spring; in US 8,757,341 B2 multiple springs are distributed radially.

[0004] Document EP 2 703 680 B1 and DE 10 2012 016 949 A1 likewise employ two toothed rings but substitute magnetic actuation for springs to reduce friction. EP 2 703 680 B1 provides one magnet per ring, whereas DE 10 2012 016 949 A1 distributes multiple magnets radially on each ring.

[0005] The present invention describes a wheel hub system comprising a main axle surrounded by a shaft sleeve carrying an axle bearing that supports rotation of a hub shell together with a second hub bearing, said second hub bearing being positioned radially in a freehub body which enables the hub shell to rotate freely about the main axle; a brake‑side dropout spacer, a cassette‑side dropout spacer and a spacer sleeve for axial positioning; a cassette secured by a cassette lockring; and a retaining ring for axial retention; wherein the freehub body couples inner and outer synchronization rings to a fixed toothed ring which is mechanically fastened to the hub shell, and wherein a mechanical engagement is produced by axial motion of a set of outer and inner bellows along the shaft sleeve.

[0006] In a proposed embodiment of present invention, the outer and inner synchronization rings are mounted on the freehub body for axial translation, thereby reducing engagement time.

[0007] Yet in another proposed embodiment of present invention, the outer and inner synchronization rings alternately mesh with the fixed toothed ring.

[0008] Yet in another proposed embodiment of present invention, the outer and inner bellows comprise polymeric viscoelastic that enable storing energy when alternately compressed by the outer and inner synchronization rings and enforcing an alternating mechanical engagement of said outer and inner synchronization rings towards the fixed toothed ring.

[0009] Yet in another proposed embodiment of present invention, the mechanical engagement enabled between the inner and outer synchronization rings and the fixed toothed ring is enabled through a set of engagement teeth, which is damped during a non-engagement state.

[0010] Yet in another proposed embodiment of present invention, a tooth‑contact noise between the inner and outer synchronization rings and the fixed toothed ring during the non‑engaged states is reduced though vibration absorption provided by the outer and inner bellows.

[0011] Yet in another proposed embodiment of present invention, the axle bearing and the second hub bearing supporting the rotation of the hub shell enable efficient load distribution.

[0012] Yet in another proposed embodiment of present invention, the brake rotor being clamped by a threaded brake lockring onto the left‑hand end of the hub shell.

[0013] Yet in another proposed embodiment of present invention, an inner diameter of the inner synchronization ring equals an inner diameter of the fixed toothed ring; an outer diameter of the outer synchronization ring equals an outer diameter of the fixed toothed ring; an inner diameter of the outer synchronization ring exceeds an outer diameter of the inner synchronization ring, enabling axial mechanical independent movement between each ring.

[0014] Yet in another proposed embodiment of present invention, the outer diameter of the inner synchronization ring comprises a toothed surface; the inner diameter of the outer synchronization ring comprises a toothed surface; the inner synchronization ring being axially positioned inside the outer synchronization ring; and both synchronization rings are axially aligned with the fixed toothed ring and angularly offset to mechanically engage with the fixed toothed ring alternately, doubling engagement points and halving engagement time.

[0015] The present invention also discloses the method of operating a wheel hub system which comprises a main axle surrounded by a shaft sleeve carrying an axle bearing that supports rotation of a hub shell together with a second hub bearing, said second hub bearing being positioned radially in a freehub body which enables the hub shell to rotate freely about the main axle; a brake-side dropout spacer, a cassette-side dropout spacer and a spacer sleeve for axial positioning; a cassette secured by a cassette lockring; and

[0016] a retaining ring for axial retention; the method being characterized by allowing the freehub body to couple inner and outer synchronization rings to a fixed toothed ring mechanically fastened to the hub shell; and producing a mechanical engagement by axially moving a set of outer and inner bellows along the shaft sleeve, thereby controlling the transmission of rotational motion between the freehub body and the hub shell.

[0017] While existing rear hub systems for bicycles, offer various improvements, they still suffer from at least two major key limitations. The first is related with the lack of responsiveness in torque engagement: Existing systems may introduce delay or slack during the transition from coasting to pedalling, especially in pawl-based or toothed disc mechanisms. This can reduce the rider’s control and efficiency, particularly in performance or technical riding scenarios. The second is related with noise during operation: Pawl and ratchet systems, and even some sprag clutch designs, tend to produce audible clicking or mechanical noise during freewheeling. This detracts from the overall riding experience, especially for users seeking a smoother and quieter ride.

[0018] Compared with existing hubs, the disclosed hub halves the engagement time and reduces vibration associated with engagement within the hub, thereby lowering the characteristic acoustic signature of such mechanisms.

[0019] The invention improves bicycle performance without compromising rider safety. It also enhances comfort, as the device is designed to absorb vibrations generated during freewheel relative motion and thus reduce the resulting noise, providing a more pleasant riding experience.

[0020] The developed hub outperforms the mentioned prior art since its assembly comprises two primary bodies rotating about a common axis, supported by bearings that connect them directly or indirectly to a hollow shaft. One body is laced to the rim by spokes; the other carries a cassette that receives torque from the crankset. The two bodies synchronize when the freehub / cassette body attains the rotational speed of the hub body, enabling one ring to engage so that both bodies rotate together. Coupling between the primary bodies is achieved using three rings, each with one toothed lateral face of different diameters and co‑axially mounted. A fixed toothed ring is rigid with the hub shell; the remaining two rings are splined to the freehub body. The outer diameter of the inner ring is smaller than the inner diameter of the outer ring.

[0021] The inner and outer rings alternately mesh with the fixed ring, doubling the number of engagement points and, in consequence, halving the time to engagement.

[0022] The two rings splined to the freehub body translate axially toward the fixed ring so that their toothed faces mate. Axial motion is generated by bellows mounted to each ring. The selection of viscoelastic polymers for actuation absorbs vibrations generated by contact between the moving rings and the fixed ring, yielding quieter operation.

[0023] In summary, the developed freehub comprises a coupling system featuring three ratchet rings: one fixed and two movables, which provides a quicker response in power transmission. The freehub enables to reduces pedaling response time by half compared to systems with two ratchet rings. The use of polymeric actuating bellows, rather than helical springs or magnets, significantly reduces noise, offering a smoother and quieter cycling experience. It is also disclosed a set of optimized hub bearings, with a larger diameter, to reduce bending moments and improve durability.

[0024] For better understanding of the present application, figures representing preferred embodiments are herein attached which, however, are not intended to limit the technique disclosed herein.

[0025] – illustrates a lateral half‑section view of the assembly of the hub.

[0026] – illustrates an isometric quarter‑section view of the hub.

[0027] – illustrates an isometric detail of the ring engagement system with the inner ring engaged to the fixed ring.

[0028] – illustrates an isometric detail of the synchronization actuation system with the inner ring engaged to the fixed ring.

[0029] – illustrates the geometry of the ratchet rings for a larger contact area in the teeth.

[0030] – illustrates a bearing arrangement for the proposed invention.

[0031] – illustrates the drive of the inner synchronization ring (A) and drive of the outer synchronization ring (B).

[0032] – illustrates the boundary conditions in fixed tooth ring (8) for engagement with the inner synchronization ring (10) (C) and the outer synchronization ring (9) (D).

[0033] – illustrates the boundary conditions in outer synchronization ring (9) for engagement with the tooth ring (8).

[0034] – illustrates the boundary conditions in inner synchronization ring (10) for engagement with the toothed ring (8).

[0035] – illustrates the boundary conditions in freehub body (15) for engagement with the inner synchronization ring (10) (E) and the outer synchronization ring (9) (F).

[0036] – illustration of the boundary conditions in the bellows (11, 12) for activating the inner synchronization ring (10)(G) and the outer synchronization ring (9) (H).

[0037] – illustrates an exploded view of the designed wheel hub system, along with all its components and the assembly sequence.

[0038] With reference to the figures, some embodiments are now described in more detail, which are however not intended to limit the scope of the present application.

[0039] Figures 1 and 2 illustrate the proposed system which comprises a main axle (6) surrounded by a shaft sleeve (1) carrying an axle bearing (2) that supports rotation of the hub shell (7), together with a second hub bearing (14). Axial positioning is established by a brake‑side dropout spacer (3), a cassette‑side dropout spacer (17), and a spacer sleeve (16). Drive is provided by a cassette (18) secured by a cassette lockring (19). Synchronization is achieved by a freehub body (15) supported on the shaft sleeve (1) by two axle bearings (2) and axially retained by a retaining ring (13). The freehub body (15) couples inner (10) and outer (9) synchronization rings to a fixed toothed ring (8) fastened to the hub shell (7). Engagement is produced by axial motion of outer (11) and inner (12) bellows along the shaft sleeve (1). The assembly also accommodates a brake rotor (4) at the opposite end, clamped by a brake lockring (5).

[0040] The hub shell (7) is connected to the remaining wheel components by spokes (not shown) anchored in holes on its outer surface. The rear hub assembly is secured to the bicycle dropout (not shown) by a main axle (6) threaded at one end. Within the dropout, a brake‑side dropout spacer (3) bears on one side and a cassette‑side dropout spacer (17) on the other. An axle bearing (2), on the brake‑rotor (4) side which is radially fixed to the shaft sleeve (1), together with a second hub bearing (14) positioned radially in the freehub body (15), enables the hub shell (7) to rotate freely about the main axle (6). Rotation of the freehub body (15) is provided by two axle bearings (2) at the cassette side (18), radially fixed to the shaft sleeve (1), about the same main axle (6).

[0041] On the brake‑rotor (4) side, the inner race of the axle bearing (2) abuts the brake‑side spacer (3) and a circumferential shoulder on the shaft sleeve (1), while the outer race bears against the hub shell (7). In the second hub bearing (14), the inner race abuts a retaining ring (13) on one side and the freehub body (15) on the other; the outer race contacts the hub shell (7). These outer‑race abutments axially locate the hub shell (7).

[0042] At the cassette side (18), the inner race of the axle bearing (2) abuts the cassette‑side dropout spacer (17) and the spacer sleeve (16). The inner race of the central axle bearing (2) bears against shoulders of the hollow shaft sleeve (1) and against the spacer sleeve (16), while its outer race contacts the freehub body (15). Together with the second hub bearing (14), this arrangement prevents axial motion of the freehub body (15). Using different bearing types for the axle bearing (2) and the secund hub bearing (14), both contacting the hub shell (7), enables a more efficient layout.

[0043] Figures 3 and 4 disclose the engagement solution which employs three toothed rings: a fixed toothed ring (8) on the hub shell (7), and an outer ring synchronization ring (9) and an inner synchronization ring (10) splined to the freehub body (15) for axial motion. The inner diameter of the inner synchronization ring (10) equals the inner diameter of the fixed toothed ring (8); the outer diameter of the outer synchronization ring (9) equals the outer diameter of the fixed toothed ring (8). In addition, the inner diameter of the outer synchronization ring (9) exceeds the outer diameter of the inner synchronization ring (10), allowing axial travel without interference, so the two rings are mutually independent.

[0044] The toothed faces between the fixed toothed ring (8) and the outer synchronization ring (9), and between the fixed toothed ring (8) and the inner synchronization ring (10), provide meshing. The outer synchronization ring (9) and inner synchronization ring (10) are angularly offset so that they engage the fixed toothed ring (8) alternately, doubling engagement points and thereby halving engagement time.

[0045] Inthe fixed toothed ring (8) is threaded (thread not shown) to improve fastening to the hub shell (7) and to enable correct tightening using a dedicated tool (not shown). The fixed toothed ring (8) has internal protrusions complementary to the protrusions visible on the left side of the shaft sleeve (1).

[0046] As shown in Figures 3 and 4, the outer synchronization ring (9) and inner synchronization ring (10) are driven by an outer bellows (11) and an inner bellows (12), respectively. The bellows (11, 12) are polymeric and elastic, storing energy when alternately compressed by the moving rings (9, 10) and continuously urging them toward the fixed toothed ring (8). The chosen materials also absorb vibrations from the freewheel mechanism and tooth contact, further reducing noise.

[0047] The brake rotor (4) is keyed to the hub shell (7) via a splined interface so that both rotate together; axially, the brake rotor (4) is clamped against the hub shell (7) by a brake lockring (5) threaded onto the left‑hand end of the hub shell (7).

[0048] The cassette (18) is radially coupled to the freehub body (15) via splines and axially retained by the cassette lockring (19) threaded on the right‑hand end of the freehub body (15).

[0049] From Figures 5 to 13 additional details on the developed invention are provided.

[0050] As illustrated in, the coupling concept consists of three ratchet rings, the toothed ring (8), the outer synchronization ring (9) and the inner synchronization ring (10). The outer (9) and inner (10) synchronization rings are movable and coaxial, offset from each other. The toothed ring (8) is fixed to the freehub body (15). The movable rings (9, 10) will be coupled to the freehub body (15) through standardized splines, sliding through them independently, which can be advantageous as they are constantly moving in opposite directions, thus reducing frictional forces.

[0051] To increase the contact area between the teeth of the movable outer synchronization ring (9) and the inner synchronization ring (10), and the teeth of the freehub body (15), a protrusion was created on both the inner (10) and outer (9) rings, as shown inwhich enables the use of longer teeth, increasing the contact area when the teeth are engaged during the cyclist pedalling. This, in turn, will reduce shear and contact stresses on the teeth of the rings.

[0052] As supported by, it should be noted that the second hub bearing (14) used in the freehub body (15) will be almost aligned with the internal hub bearings (20), which allow for a better load distribution. However, these bearings should not be perfectly aligned to ensure that when exposed to axial loads, the bearings' spheres always contact the same side of their race. Therefore, this will be the bearing configuration to be used.

[0053] depicts the drive of the movable rings; this could be done using helical springs or magnets. However, in order to reduce noise and make the mechanism quieter, inner bellows (12) and outer bellows (11) made of a polymeric material with elastic properties will be designed. These bellows will aim to move the movable rings and reduce vibrations coming from their engagement with the fixed ring.

[0054] With regard to the fixed ring, i.e., the toothed ring (8), which illustration is depicted in, it will be fixed to the hub shell (7) through a threaded connection. In one embodiment of the invention, toothed ring (8) comprises 60 teeth responsible for transmitting the movement from the synchronization rings (9, 10) to the hub shell (7) and, consequently, to the wheel of the bicycle. The teeth comprise a negative inclination, which facilitates meshing with full contact across its the entire surface. The toothed ring (8), it will be subjected to two types of situations, namely meshing with the inner toothed ring (10) [event C] and meshing with the outer toothed ring (9) [event D]. These two events never occur simultaneously, as both the movable toothed rings will engage alternately, as shown inC and D. It is important to note that the threaded area (R.1) of the toothed ring (8) represent the fixations to the hub shell (7). As for the applied loads in situations C and D, they will have the same value in both cases and will be applied to a contact face area of the teeth, depending on which movable ring (9, 10) is engaged.

[0055] In the outer synchronization ring (9), represented in, the geometry of the teeth is very similar to the geometry of the teeth of the fixed toothed ring (8), as well as the number of teeth, to allow engagement. This outer synchronization ring (9) also features DIN 5480 – 32 x 1 x 34 splines, which will connect it to the freehub body (15), as well as a rear protrusion whose function is to center the outer bellows (11) responsible for its activation. The outer synchronization ring (9) must transmit the maximum torque from the splines to the tooth faces. On the surfaces of the splines that will be in contact with the splines of the freehub body (15), torque forces (9.1) will be applied, and on the faces of the teeth that will be in contact with the teeth of the fixed toothed ring (8), fixations (R.2) will be applied.

[0056] In the inner synchronization ring (10), shown in, the geometry of the teeth is very similar to that of the fixed toothed ring (8), as well as the number of teeth, to ensure proper meshing. This inner toothed ring also features DIN 5480 – 27 x 1 x 26 splines that will connect to the freehub body (15), as well as a rear bump designed to center the inner bellows (12) responsible for its activation. Similar to the fixed toothed ring (8), the inner synchronization ring (10) must also transmit the maximum torque from the splines to the faces of the teeth. Therefore, as shown in, the torque forces (10.1) will be applied to the spline surfaces that make contact with the splines of the freehub body (15), while fixations (R.3) will be applied to the tooth faces that mesh with the teeth of the fixed toothed ring (8).

[0057] In the design of the freewheel body (15), aspects for the proper functioning of the designed hub were considered, as shown in. In this illustration, the inner and outer splines are visible, where the inner and outer synchronization rings (9, 10) will slide, respectively. For the validation of the freewheel body (15), it is important to note that it will be subjected to two types of situations, as seen in, namely engagement with the inner synchronization ring (10), event E, and engagement with the outer synchronization ring (9), event F. These two events, E and F, will never occur simultaneously since the movable toothed synchronization rings (9, 10) will engage alternately. In the first case E, the inner area (R.4) represents the component fixations, specifically at the bearing zones and the inner splines, where the inner synchronization ring (10) will be coupled. The maximum torque is applied in the inner area (R.4), specifically at the area where the cassette will be connected. In the second case F, the boundary conditions are very similar to those of the first case E, with the only difference being in the defined fixations, which have moved from the inner splines to the outer splines, where the maximum torque is applied in the outer area (R.5), where the outer synchronization ring (9) will be coupled.

[0058] In the modelling of the inner (12) and outer (11) actuating bellows, whose function is to press the inner (10) and outer (9) synchronization rings, respectively, against the fixed toothed ring (8), a design was used that maximizes their elastic properties, as seen in. The purpose of these components is to store elastic energy. Also, in the context of elastic energy storage, and in one preferred embodiment of the invention, a material with favourable characteristics was selected, namely neoprene rubber, with an elasticity modulus of 6.1 MPa and a Poisson's ratio of 0.49. The validation of the actuating bellows (11, 12) differs somewhat from the validation carried out for the previous components, as it serves to determine the displacement of the bellows when subjected to a force corresponding to the actuation force of the bellows, which must be equal to or greater than the sum of the frictional force of the rings and the acceleration force, as presented in Table 1.

[0059] Table 1 - Actuation force of the bellows as a function of friction force and acceleration force

[0060] FFriction(N)FAcceleration(N)FActuation(N)Interior toothed ring0,2344,54,734Exterior toothed ring0,2043,9194,123

[0061] In, the boundary conditions for both the inner (12) and outer (11) actuator bellows are presented. For the inner bellow (12), the surface that will be in contact with the freehub body (15) will have a fixation (R.6), and the surface in contact with the inner synchronization ring (10) will have the activation force (F.6) applied. For the outer bellow (11), the surface that will be in contact with the elastic ring will have a fixation (F.7), and the surface in contact with the outer synchronization ring (9) will have the activation force (F.7) applied.

[0062] In a preferred embodiment of the invention, the construction of the modelled metallic components, namely the three rings (8, 9, 10) and the freehub body (15), comprise an alloy steel will be used due to its high strength, specifically the DIN 30 CrNiMo 8, with a yield stress of 1050 MPa.

[0063] It is important to mention that all components responsible for power transmission are pedal driven by the cyclist's force on a conventional bicycle to the freehub, which in turn is connected to the rear wheel. All the force exerted on the pedal is transmitted through the crank set to the chainring, which engages with a single-speed chain and simultaneously with one of the various toothed rings on a cassette. The cassette is coupled to the rear hub via splines.

[0064] Additionally, during freewheel movement, the clicks between the movable ratchet rings and the fixed ratchet ring were felt, totalling 120 engagement points, resulting from the 60 teeth on the interior ratchet ring and 60 on the exterior ratchet ring. This confirmed that the addition of a third ratchet ring provided faster engagement. Regarding the noise generated during the attempts to engage the rings, it was reduced and muffled, due to the absorption of vibrations by the polymer bellows designed.

[0065] To conclude, the current development enables to improve the energy transfer from the chain to the rear wheel more efficiently and smoothly. The use of three ratchet rings provides twice the engagement points compared to a system with only two rings, resulting in halving the cyclist’s pedal response time and delivering a much quicker torque transmission. The introduction of two actuating bellows made from polymeric material, as an alternative to typical helical springs or magnets, makes the engagement process much quieter. The material's excellent vibration absorption properties result in a significantly smoother user experience. Choosing a larger diameter bearing to connect the hub and the freehub greatly improves the bending moment on the axle bushing. By positioning the bearing closer to the axle's end, it reduces the length of the arm responsible for the bending moment, consequently extending the life of the designed hub. All single-row ball bearings used provide effective protection against dust, moisture, and other contaminants. This sealing helps to prolong the bearings' lifespan by reducing wear and maintaining proper lubrication within the bearing balls.

[0066] Bicycle hub drive trains; synchronization mechanisms in power‑transmission equipment and machinery.

[0067] 1 - shaft sleeve; 2 - axle bearing; 3 - brake‑side dropout spacer; 4 - brake rotor; 5 - brake lockring; 6 - main axle; 7 - hub shell; 8 - toothed ring; 9 - outer synchronization ring; 10 - inner synchronization ring; 11 - outer bellows; 12 - inner bellows; 13 - retaining ring; 14 - second hub bearing; 15 - freehub body; 16 - spacer sleeve; 17 - cassette‑side dropout spacer; 18 – cassette; 19 - cassette lockring; 20 - internal hub bearing; 9.1 - Torque forces between the outer synchronization ring (9) surface and the toothed ring (8); 10.1 - Torque forces between the inner synchronization ring (10) surface and the toothed ring (8); R.1 - threaded area of the toothed ring (8); R.2 – inner fixations of the outer synchronization ring (9); R.3 – outer fixations of the inner synchronization ring (10); R.4 – inner fixations of the freehub body (15); R.5 – outer fixations of the freehub body (15); R.6 – inner bellow (12) fixation surface; F.6 – inner bellow (12) activation force; R.7 – outer bellow (11) fixation surface; F.7 – outer bellow (11) activation force.

Claims

A wheel hub system comprising a main axle (6) surrounded by a shaft sleeve (1) carrying an axle bearing (2) that supports rotation of a hub shell (7) together with a second hub bearing (14), said second hub bearing (14) being positioned radially in a freehub body (15) which enables the hub shell (7) to rotate freely about the main axle (6); a brake‑side dropout spacer (3), a cassette‑side dropout spacer (17) and a spacer sleeve (16) for axial positioning; a cassette (18) secured by a cassette lockring (19); and a retaining ring (13) for axial retention; wherein the freehub body (15) couples inner (10) and outer (9) synchronization rings to a fixed toothed ring (8) which is mechanically fastened to the hub shell (7), and wherein a mechanical engagement is produced by axial motion of a set of outer (11) and inner (12) bellows along the shaft sleeve (1).The system of claim 1, wherein the outer (9) and inner (10) synchronization rings are mounted on the freehub body (15) for axial translation, thereby reducing engagement time.The system of any of the preceding claims, wherein the outer (9) and inner (10) synchronization rings alternately mesh with the fixed toothed ring (8).The system of claim 1, wherein the outer (11) and inner (12) bellows comprise polymeric viscoelastic that enable storing energy when alternately compressed by the outer (9) and inner (10) synchronization rings and enforcing an alternating mechanical engagement of said outer (9) and inner (10) synchronization rings towards the fixed toothed ring (8).The system of any of the preceding claims, wherein the mechanical engagement enabled between the inner (10) and outer (9) synchronization rings and the fixed toothed ring (8) is enabled through a set of engagement teeth, which is damped during a non-engagement state.The system of any of the preceding claims, wherein a tooth‑contact noise between the inner (10) and outer (9) synchronization rings and the fixed toothed ring (8) during the non‑engaged states is reduced though vibration absorption provided by the outer (11) and inner (12) bellows.The system of any of the preceding claims, wherein the axle bearing (2) and the second hub bearing (14) supporting the rotation of the hub shell (7) enable efficient load distribution.The system of any of the preceding claims, characterized by the brake rotor (4) being clamped by a threaded brake lockring (5) onto the left‑hand end of the hub shell (7).The system of any of the preceding claims, wherein an inner diameter of the inner synchronization ring (10) equals an inner diameter of the fixed toothed ring (8); an outer diameter of the outer synchronization ring (9) equals an outer diameter of the fixed toothed ring (8); an inner diameter of the outer synchronization ring (9) exceeds an outer diameter of the inner synchronization ring (10), enabling axial mechanical independent movement between each ring (9, 10).The system of any of the preceding claims, characterized by the outer diameter of the inner synchronization ring (10) comprising a toothed surface; the inner diameter of the outer synchronization ring (9) comprising a toothed surface; the inner synchronization ring (10) being axially positioned inside the outer synchronization ring (9); and both synchronization rings (9, 10) are axially aligned with the fixed toothed ring (8) and angularly offset to mechanically engage with the fixed toothed ring (8) alternately, doubling engagement points and halving engagement time.Method of operation of the wheel hub system described in any of the previous claims, comprising a main axle (6) surrounded by a shaft sleeve (1) carrying an axle bearing (2) that supports rotation of a hub shell (7) together with a second hub bearing (14), said second hub bearing (14) being positioned radially in a freehub body (15) which enables the hub shell (7) to rotate freely about the main axle (6); a brake-side dropout spacer (3), a cassette-side dropout spacer (17) and a spacer sleeve (16) for axial positioning; a cassette (18) secured by a cassette lockring (19); and a retaining ring (13) for axial retention; the method being characterized by: allowing the freehub body (15) to couple inner (10) and outer (9) synchronization rings to a fixed toothed ring (8) mechanically fastened to the hub shell (7); and producing a mechanical engagement by axially moving a set of outer (11) and inner (12) bellows along the shaft sleeve (1), thereby controlling the transmission of rotational motion between the freehub body (15) and the hub shell (7).

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