A single-motor cross-medium composite rotorcraft drive system and control method

Abstract

The present invention relates to a single-motor cross-medium composite rotorcraft drive system and control method. The drive system includes a motor, a servo, a gear meshing transmission device, a variable collective pitch mechanism, a blade folding mechanism, a self-locking bearing, an underwater drive device, and an aerial drive device. The variable collective pitch mechanism is used to achieve variable collective pitch operation on the upper and lower rotors of the coaxial twin rotors. The blade folding mechanism is used to unfold and fold the blades. The underwater drive device includes a self-locking bearing and a marine propeller for underwater propulsion. The aerial drive device includes four blades, two hubs, and two self-locking bearings for aerial propulsion. The gear meshing transmission device is used to drive three groups of blades to rotate in different directions at different times. The present invention realizes that under the control of a single drive motor, only the marine propeller is propelled underwater, the marine propeller does not move in the air, and only two pairs of rotors rotate. This can ensure that the amphibious rotorcraft can fly efficiently and with low power consumption in the air and underwater, thereby improving the compactness of the amphibious rotorcraft.

Description

Technical Field

[0001] The present invention relates to the technical field of amphibious rotorcraft, and in particular to a single-motor cross-medium composite rotorcraft drive system and a control method. Background Art

[0002] A cross-medium composite rotorcraft can fly both in the air and underwater, seamlessly combining the advantages of aircraft and submarines. This is a key research direction in the field of cross-medium aircraft. The wider range of space opens up new possibilities for aircraft, and it holds enormous potential in areas such as marine rescue and reconnaissance. The key to cross-medium composite rotorcraft technology lies in its ability to operate both in the air and underwater, while also enabling stable switching between these two modes.

[0003] Currently, there is a lack of research on cross-medium composite rotorcraft. Due to the different working media, the characteristics of air and underwater blades differ significantly: air blades are generally slender and less solid, while underwater blades are relatively wide. Equipping a vehicle with two power systems significantly increases the load, and one unit is always idle, resulting in extremely low efficiency. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention cleverly designs a set of air blade retraction and extension devices, so that the resistance encountered by the air blades when the aircraft is working underwater is greatly reduced. The drive system of the present invention has only one motor and uses a gear transmission system including self-locking bearings to achieve the purpose of changing the working state of the aircraft by changing the direction of the main drive gear.

[0005] This cross-medium composite rotorcraft is equipped with only one drive motor and is always in working condition, which reduces the workload of the aircraft while also improving work efficiency.

[0006] This application achieves the above effects through the following technical solutions:

[0007] On the one hand, the present application provides a single-motor cross-medium composite rotorcraft drive system, the drive system includes a main drive shaft, and the drive shaft is composed of a gear meshing transmission device, an aerial drive device, a long shaft, a short shaft, a variable collective pitch control mechanism, a blade folding mechanism, a servo tray, an underwater drive device, and a self-locking bearing from bottom to top; the aerial drive device, the variable collective pitch control mechanism, and the variable collective pitch disc blade folding mechanism are arranged symmetrically up and down with the motor tray as the center, and the aerial drive device and the underwater drive device are both connected to the motor and driven by the motor.

[0008] Furthermore, the gear meshing transmission device includes a gear box, a main drive gear, a secondary drive gear and a transmission gear, wherein the main drive gear is directly meshed with the secondary drive gear and the transmission gear A, and the transmission gear B is directly meshed with the secondary drive gear, ensuring that the upper blade and the lower blade rotate in opposite directions at the same speed.

[0009] Furthermore, the aerial drive device includes two parts, an upper and lower rotor, which are symmetrically distributed with the motor tray as the center; the upper and lower rotor parts are composed of a hub, a blade rocker arm, a self-locking bearing, and a blade. In the lower rotor, the self-locking bearing C is connected to the short shaft by a key, the hub is connected to the blade rocker arm, and the blade rocker arm is connected to the blade; in the upper rotor, the self-locking bearings A and B are connected to the long shaft by a key, the hub is connected to the blade rocker arm, and the blade rocker arm is connected to the blade; through the positioning of the self-locking bearing, the upper rotor and the lower rotor rotate in opposite directions.

[0010] Furthermore, the long shaft is connected to the aerial drive device, the upper blade hub, the variable collective pitch disc, the servo tray, and the transmission gear A from top to bottom; the short shaft is connected to the lower blade hub and the transmission gear B.

[0011] Furthermore, the self-locking bearing includes a stationary ring, a spring, a movable ring, and a blocking block; the movable ring is connected to the major axis or the minor axis, the spring is located in the groove of the movable ring, and acts as a blocking block for the blocking block, the blocking block is connected to the stationary ring, and the stationary ring is connected to the propeller hub; when the movable ring protrudes toward the inside of the stationary ring and rotates, the blocking block will drive the stationary ring to rotate, thereby driving the propeller hub to rotate; when the movable ring rotates counterclockwise, the blocking block is compressed and moves toward the direction of the movable ring groove, thereby not driving the stationary ring to rotate.

[0012] Furthermore, the collective pitch variable mechanism includes N collective pitch servos, N pitch variable rods, a transmission disc and N rocker arms, each servo is connected to a pitch variable rod, the pitch variable rod is connected to the collective pitch variable transmission disc, the collective pitch variable transmission disc is connected to the collective pitch variable rocker arm through the pitch variable rod, and the collective pitch variable mechanism is symmetrically distributed on the upper and lower rotor parts.

[0013] The blade folding mechanism includes N folding servos, N folding rocker arms, a blade folding pull ring, a folding pull rod and N groups of folding four-bar linkage mechanisms; the folding servos are connected to the blade folding pull ring through a connecting rod, the blade folding pull ring is connected to the folding rocker arm, the folding rocker arm is connected to the blade through a connecting rod mechanism, and the blade folding mechanism is symmetrically distributed on the upper and lower rotor parts.

[0014] Furthermore, the servo tray is divided into two parts, upper and lower rotors, which are connected to the long shaft; the underwater drive device includes a marine propeller and a self-locking bearing, the marine propeller is connected to the long shaft through the self-locking bearing, and the underwater drive device is restricted from rotating in a single direction by the self-locking bearing.

[0015] Furthermore, the self-locking bearing is composed of a moving ring, a stationary ring, a spring, and a stop block. The stationary ring is fixed to the hub by bolts, and the moving ring is connected to the drive shaft. The self-locking bearing ensures that the hub rotates in a single direction.

[0016] On the other hand, based on the above-mentioned single-motor cross-medium composite rotorcraft drive system, the present application also provides a control method thereof, which includes two working modes: air mode and underwater mode; wherein,

[0017] In the aerial mode of the rotorcraft drive system, when the main drive gear rotates in a first direction, the transmission gear A rotates in a second direction, the transmission gear B rotates in the first direction, the major axis rotates in the second direction, the minor axis rotates in the first direction, the upper rotor portion rotates along with the major axis in the second direction, the lower rotor portion rotates clockwise along with the minor axis, and the marine propeller does not rotate along with the major axis; when the lift of the aircraft needs to be changed, the variable collective pitch mechanism pushes the variable collective pitch rocker arm through the variable pitch servo, and the connecting rod pushes the variable collective pitch transmission disc, and the variable collective pitch transmission disc changes the collective pitch of the blades through the variable pitch pull rod, thereby changing the lift of the entire system and adjusting the height of the entire system;

[0018] In the underwater mode of the rotorcraft drive system, when the main drive gear rotates in the second direction, the transmission gear A rotates in the first direction, the transmission gear B rotates in the second direction, the major axis rotates in the first direction, and the minor axis rotates in the second direction. Due to the presence of the self-locking bearing structure, the upper and lower rotor parts do not rotate with the value, and the marine propeller rotates in the first direction with the major axis;

[0019] The first direction is opposite to the second direction.

[0020] Furthermore, when the air mode is switched to the underwater mode, the folding servo of the blade folding mechanism pushes the connecting rod to drive the folding transmission pull ring, and the folding transmission pull ring drives the blades to fold the blades, thereby reducing the resistance of the drive system underwater.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. The single-motor cross-medium composite rotorcraft drive system and control method described in the present invention has the characteristics of the aircraft operating efficiently in both water and air, organically combining the advantages of aircraft and submarines.

[0023] 2. The single-motor cross-medium composite rotorcraft drive system and control method described in the present invention achieves the goal of retracting and extending the air blades when working underwater, which greatly reduces the resistance encountered during underwater operation.

[0024] 3. The single-motor cross-medium composite rotorcraft drive system and control method described in the present invention has a drive system equipped with only one motor that is always in operation, thereby reducing the workload while increasing work efficiency.

[0025] 4. The single-motor cross-medium composite rotorcraft drive system and control method described in the present invention cleverly designs a gear meshing transmission device including a self-locking bearing, which changes the working state by changing the direction of the main drive gear, thereby achieving efficient operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the overall structure of the cross-medium composite rotorcraft drive system of the present invention;

[0027] Figure 2 This is a view of a marine propeller hub;

[0028] Figure 3 This is the upper rotor hub view;

[0029] Figure 4 This is the lower rotor hub view;

[0030] Figure 5 Detailed diagram of the variable collective pitch and folding mechanism;

[0031] Figure 6 .This is the servo tray view;

[0032] Figure 7 .It is the internal structure diagram of the gearbox;

[0033] Figure 8 .It is the view of self-locking bearing;

[0034] In the figure, 1. marine propeller, 2. upper air blade, 3. upper blade folding mechanism, 4. upper blade collective pitch variable mechanism, 5. lower blade folding mechanism, 6. lower air blade, 7. lower blade collective pitch variable mechanism, 8. gearbox, 9. self-locking bearing A, 10. marine propeller hub, 11. upper rotor folding four-bar linkage, 12. upper rotor hub, 13. self-locking bearing B, 14. lower rotor folding four-bar linkage, 15. lower rotor hub, 16. self-locking bearing C, 17. collective pitch variable rocker arm, 18. collective pitch variable disk, 19. pitch variable pull rod, 2 0. Folding rocker arm, 21. Folding transmission pull ring, 22. Upper rotor pitch-changing servo A, 23 Upper rotor folding servo A, 24. Upper rotor folding servo B, 25. Upper rotor pitch-changing servo B, 26. Lower rotor pitch-changing servo A, 27. Lower rotor folding servo A, 28. Lower rotor folding servo B, 29. Lower rotor pitch-changing servo B, 30. Short shaft, 31. Transmission gear B, 32. Transmission gear A, 33. Auxiliary drive gear, 34. Main drive gear, 35. Long shaft, 36. Fixed ring, 37. Spring, 38. Moving ring, 39. Block. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings in the examples of the present invention. Figure 1 As shown, this design utilizes a single-motor cross-medium composite rotorcraft drive system and control method to design a novel cross-medium composite rotorcraft drive system and control method. The drive system includes a marine propeller 1, upper air blades 2, lower air blades 6, and a gearbox 8. The control system includes four variable collective pitch servos, four blade folding servos, an upper blade folding mechanism 3, an upper blade variable collective pitch mechanism 4, a lower blade folding mechanism 5, and a lower blade variable collective pitch mechanism 7. Through the unique meshing mechanism between the main drive gear 34, the auxiliary drive gear 33, the transmission gear B31, and the transmission gear A32, the two transmission gears always rotate in opposite directions, thereby ensuring that the aerial and underwater drive devices do not operate simultaneously. The present invention utilizes multiple self-locking bearings to achieve efficient switching between aerial and underwater operating modes. The present invention utilizes a total of eight servos and a series of ingenious linkage mechanisms to achieve variable collective pitch and folding of the air blades. Example 1

[0036] On the one hand, the present application provides a single-motor cross-medium composite rotorcraft drive system, the drive system includes a main drive shaft, and the drive shaft is composed of a gear meshing transmission device, an aerial drive device, a long shaft, a short shaft, a variable collective pitch control mechanism, a blade folding mechanism, a servo tray, an underwater drive device, and a self-locking bearing from bottom to top; the aerial drive device, the variable collective pitch control mechanism, and the variable collective pitch disc blade folding mechanism are arranged symmetrically up and down with the motor tray as the center, and the aerial drive device and the underwater drive device are both connected to the motor and driven by the motor.

[0037] Furthermore, the gear meshing transmission device includes a gear box, a main drive gear, a secondary drive gear and a transmission gear, wherein the main drive gear is directly meshed with the secondary drive gear and the transmission gear A, and the transmission gear B is directly meshed with the secondary drive gear, ensuring that the upper blade and the lower blade rotate in opposite directions at the same speed.

[0038] Furthermore, the aerial drive device includes two parts, an upper and lower rotor, which are symmetrically distributed with the motor tray as the center; the upper and lower rotor parts are composed of a hub, a blade rocker arm, a self-locking bearing, and a blade. In the lower rotor, the self-locking bearing C is connected to the short shaft by a key, the hub is connected to the blade rocker arm, and the blade rocker arm is connected to the blade; in the upper rotor, the self-locking bearings A and B are connected to the long shaft by a key, the hub is connected to the blade rocker arm, and the blade rocker arm is connected to the blade; through the positioning of the self-locking bearing, the upper rotor and the lower rotor rotate in opposite directions.

[0039] Furthermore, the long shaft is connected to the aerial drive device, the upper blade hub, the variable collective pitch disc, the servo tray, and the transmission gear A from top to bottom; the short shaft is connected to the lower blade hub and the transmission gear B.

[0040] Furthermore, the self-locking bearing includes a stationary ring, a spring, a movable ring, and a blocking block; the movable ring is connected to the major axis or the minor axis, the spring is located in the groove of the movable ring, and acts as a blocking block for the blocking block, the blocking block is connected to the stationary ring, and the stationary ring is connected to the propeller hub; when the movable ring protrudes toward the inside of the stationary ring and rotates, the blocking block will drive the stationary ring to rotate, thereby driving the propeller hub to rotate; when the movable ring rotates counterclockwise, the blocking block is compressed and moves toward the direction of the movable ring groove, thereby not driving the stationary ring to rotate.

[0041] Furthermore, the collective pitch variable mechanism includes N collective pitch servos, N pitch variable rods, a transmission disc and N rocker arms, each servo is connected to a pitch variable rod, the pitch variable rod is connected to the collective pitch variable transmission disc, the collective pitch variable transmission disc is connected to the collective pitch variable rocker arm through the pitch variable rod, and the collective pitch variable mechanism is symmetrically distributed on the upper and lower rotor parts.

[0042] The blade folding mechanism includes N folding servos, N folding rocker arms, a blade folding pull ring, a folding pull rod and N groups of folding four-bar linkage mechanisms; the folding servos are connected to the blade folding pull ring through a connecting rod, the blade folding pull ring is connected to the folding rocker arm, the folding rocker arm is connected to the blade through a connecting rod mechanism, and the blade folding mechanism is symmetrically distributed on the upper and lower rotor parts.

[0043] Furthermore, the servo tray is divided into two parts, upper and lower rotors, which are connected to the long shaft; the underwater drive device includes a marine propeller and a self-locking bearing, the marine propeller is connected to the long shaft through the self-locking bearing, and the underwater drive device is restricted from rotating in a single direction by the self-locking bearing.

[0044] Furthermore, the self-locking bearing is composed of a moving ring, a stationary ring, a spring, and a stop block. The stationary ring is fixed to the hub by bolts, and the moving ring is connected to the drive shaft. The self-locking bearing ensures that the hub rotates in a single direction.

[0045] like Figure 4 As shown, when 34. the main drive gear rotates clockwise (viewed from the bottom up from the perspective of the engine), 32. the transmission gear A rotates counterclockwise, and 31. the transmission gear B rotates clockwise, thereby causing 35. the long shaft to rotate counterclockwise and 30. the short shaft to rotate clockwise. Due to the presence of the self-locking bearings in the structure, 9. the self-locking bearing A will not drive 1. the marine propeller to rotate, and 13. the self-locking bearing B drives 12. the upper rotor hub below it to rotate counterclockwise, causing 2. the upper air blade to rotate counterclockwise. At this time, 16. the self-locking bearing C rotates clockwise, thereby driving 6. the downward blade to rotate clockwise. The marine propeller does not rotate, and the upper and lower air blades rotate at the same speed and in opposite directions. This is the aerial working state of the invention. When it is necessary to increase or change the lift, as shown in the attached Figure 6 The four collective pitch servos shown are working, driving the collective pitch rocker arm 17 to move the collective pitch disc 18 toward the two ends of the drive system, which in turn causes the pitch rod 19 to move, thereby changing the collective pitch of the air blades and achieving the purpose of changing lift. Example 2

[0046] On the other hand, based on the above-mentioned single-motor cross-medium composite rotorcraft drive system, the present application also provides a control method thereof, which includes two working modes: air mode and underwater mode; wherein,

[0047] In the aerial mode of the rotorcraft drive system, when the main drive gear rotates in a first direction, the transmission gear A rotates in a second direction, the transmission gear B rotates in the first direction, the major axis rotates in the second direction, the minor axis rotates in the first direction, the upper rotor portion rotates along with the major axis in the second direction, the lower rotor portion rotates clockwise along with the minor axis, and the marine propeller does not rotate along with the major axis; when the lift of the aircraft needs to be changed, the variable collective pitch mechanism pushes the variable collective pitch rocker arm through the variable pitch servo, and the connecting rod pushes the variable collective pitch transmission disc, and the variable collective pitch transmission disc changes the collective pitch of the blades through the variable pitch pull rod, thereby changing the lift of the entire system and adjusting the height of the entire system;

[0048] In the underwater mode of the rotorcraft drive system, when the main drive gear rotates in the second direction, the transmission gear A rotates in the first direction, the transmission gear B rotates in the second direction, the major axis rotates in the first direction, and the minor axis rotates in the second direction. Due to the presence of the self-locking bearing structure, the upper and lower rotor parts do not rotate with the value, and the marine propeller rotates in the first direction with the major axis;

[0049] The first direction is opposite to the second direction.

[0050] Furthermore, when the air mode is switched to the underwater mode, the folding servo of the blade folding mechanism pushes the connecting rod to drive the folding transmission pull ring, and the folding transmission pull ring drives the blades to fold the blades, thereby reducing the resistance of the drive system underwater.

[0051] When the drive system needs to switch from airborne working state to underwater working state, as shown in the attached Figure 6 The four servos that control the folding of the air blades work simultaneously, driving the folding rocker 20 to push the folding drive pull ring 21 toward the two ends of the drive system. The two folding drive pull rings drive the folding four-bar linkage of the upper rotor 11 and the folding four-bar linkage of the lower rotor 14 to fold the upper air blade 2 and the lower air blade 6. Next, the engine will change direction and the entire system will enter the underwater working mode. Figure 7 As shown, when main drive gear 34 rotates counterclockwise (viewed from the engine's bottom-up perspective), transmission gear A32 rotates clockwise, and transmission gear B31 rotates counterclockwise, causing major shaft 35 to rotate clockwise and minor shaft 30 to rotate counterclockwise. Due to the presence of the self-locking bearings in the structure, self-locking bearings B13 and C16 do not drive the upper rotor hub 12 and lower rotor hub 15 to rotate. At this point, only self-locking bearing A9 drives the marine propeller 1 clockwise, indicating the underwater operation of the invention.

Claims

1. A single-motor cross-medium composite rotorcraft drive system, characterized by: The drive system includes a main drive shaft, which is composed of a gear meshing transmission device, an aerial drive device, a major shaft, a minor shaft, a variable collective pitch control mechanism, a blade folding mechanism, a steering gear tray, an underwater drive device, and a self-locking bearing. The aerial drive device, the variable collective pitch control mechanism, and the variable collective pitch disc blade folding mechanism are symmetrically arranged with the motor tray as the center. The aerial drive device and the underwater drive device are both connected to the motor and driven by the motor. The aerial drive device includes two parts, an upper rotor and an lower rotor, which are symmetrically distributed with the motor tray as the center. The upper and lower rotor parts are composed of a hub, a blade rocker arm, a self-locking bearing, and a blade. In the lower rotor, the self-locking bearing C is connected to the short shaft by a key, the hub is connected to the blade rocker arm, and the blade rocker arm is connected to the blade; in the upper and lower rotors, the self-locking bearings B and self-locking bearings C are connected to the long shaft by a key, the hub is connected to the blade rocker arm, and the blade rocker arm is connected to the blade; through the positioning of the self-locking bearings B and C, the upper rotor and the lower rotor rotate in opposite directions; The steering gear tray is divided into two parts, the upper and lower rotors, which are connected to the long shaft; the underwater drive device includes a marine propeller and a self-locking bearing A, the marine propeller is connected to the long shaft through the self-locking bearing A, and the underwater drive device is limited to rotate in a single direction by the self-locking bearing A; The control method of the drive system includes two working modes: air mode and underwater mode; wherein, In the aerial mode of the rotorcraft drive system, when the main drive gear rotates in a first direction, the transmission gear A rotates in a second direction, the transmission gear B rotates in the first direction, the major axis rotates in the second direction, the minor axis rotates in the first direction, the upper rotor portion rotates along with the major axis in the second direction, the lower rotor portion rotates clockwise along with the minor axis, and the marine propeller does not rotate along with the major axis; when it is necessary to change the lift of the aircraft, the variable collective pitch control mechanism pushes the variable collective pitch rocker arm through the variable pitch servo, and the connecting rod pushes the variable collective pitch transmission disc, and the variable collective pitch transmission disc changes the collective pitch of the blades through the variable pitch pull rod, thereby changing the lift of the entire system and adjusting the height of the entire system; In the underwater mode of the rotorcraft drive system, when the main drive gear rotates in the second direction, the transmission gear A rotates in the first direction, the transmission gear B rotates in the second direction, the major axis rotates in the first direction, and the minor axis rotates in the second direction. Due to the presence of the self-locking bearings A, B, and C structures, the upper and lower rotor parts do not rotate with the value, and the marine propeller rotates in the first direction with the major axis; the first direction is opposite to the second direction.

2. The single-motor cross-medium composite rotorcraft drive system according to claim 1, characterized in that: The gear meshing transmission device includes a gear box, a main drive gear, a secondary drive gear and a transmission gear, wherein the main drive gear is directly meshed with the secondary drive gear and the transmission gear A, and the transmission gear B is directly meshed with the secondary drive gear, ensuring that the upper blade and the lower blade rotate in opposite directions at the same speed.

3. The single-motor cross-medium composite rotorcraft drive system according to claim 1, characterized in that: The long shaft is connected to the air drive device, the upper blade hub, the variable collective pitch disc, the steering gear tray, and the transmission gear A from top to bottom; the short shaft is connected to the lower blade hub and the transmission gear B.

4. The single-motor cross-medium composite rotorcraft drive system according to claim 1, characterized in that: The self-locking bearing A, self-locking bearing B and self-locking bearing C all include a stationary ring, a spring, a moving ring and a blocking block; the moving ring is connected to the major axis or the minor axis, the spring is located in the groove of the moving ring, and acts as a blocking block for the blocking block, the blocking block is connected to the stationary ring, and the stationary ring is connected to the propeller hub; when the moving ring protrudes toward the inside of the stationary ring and rotates, the blocking block will drive the stationary ring to rotate, thereby driving the propeller hub to rotate; when the moving ring rotates counterclockwise, the blocking block is compressed and moves toward the groove of the moving ring, thereby not driving the stationary ring to rotate.

5. The single-motor cross-medium composite rotorcraft drive system according to claim 1, characterized in that: The variable collective pitch control mechanism includes N collective pitch servos, N pitch change rods, a transmission disc and N rocker arms. Each servo is connected to a pitch change rod, the pitch change rod is connected to the variable collective pitch transmission disc, and the variable collective pitch transmission disc is connected to the variable collective pitch rocker arm through the pitch change rod. The variable collective pitch control mechanism is symmetrically distributed on the upper and lower rotor parts.

6. The single-motor cross-medium composite rotorcraft drive system according to claim 1, characterized in that: The blade folding mechanism includes N folding servos, N folding rocker arms, a blade folding pull ring, a folding pull rod and N groups of folding four-bar linkage mechanisms; the folding servos are connected to the blade folding pull ring through a connecting rod, the blade folding pull ring is connected to the folding rocker arm, the folding rocker arm is connected to the blade through a connecting rod mechanism, and the blade folding mechanism is symmetrically distributed on the upper and lower rotor parts.

7. The single-motor cross-medium composite rotorcraft drive system according to claim 1, characterized in that: The self-locking bearing A, self-locking bearing B, and self-locking bearing C are composed of a dynamic ring, a stationary ring, a spring, and a stop block. The stationary ring is fixed to the hub by bolts, and the dynamic ring is connected to the drive shaft. The self-locking bearing A, self-locking bearing B, and self-locking bearing C ensure that the hub rotates in a single direction.

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