Seal for bicycle crank with differential chainring motion
A seal for a bicycle drivetrain is configured to shield and protect part of the bicycle drivetrain from contamination by materials commonly found in the cycling environment, namely dirt, oil, water and other debris found on cycling surfaces. The seal is configured to shield the bicycle drivetrain from grit that may foul lockring interfaces, leading to seized threads, and cause difficulty removing the lock ring when it comes time to service the motor or replace the chainring.
1. A bicycle drive assembly comprising:
a. a bicycle motor comprising:
i. a motor chainring spindle; and
ii. a motor crank spindle;
b. a bicycle chainring installed onto the motor chainring spindle;
c. a drive side crank arm including a crank arm spindle hole installed onto the motor crank spindle; and
d. a seal ring fitted to a crank-seal mating surface of the drive side crank arm, wherein the crank-seal mating surface faces away from the crank arm spindle hole and toward the bicycle motor.
2. The bicycle drive assembly of claim 1 , wherein the motor chainring spindle and the motor crank spindle are concentric about a crank spindle axis of the bicycle drive assembly.
3. The bicycle drive assembly of claim 1 , wherein one or more crank seal retention lips of the seal ring mate with one or more arm seal grooves of the drive side crank arm to fit the seal ring to the drive side crank arm.
4. The bicycle drive assembly of claim 1 , wherein the drive side crank arm is fitted to the motor crank spindle by one or more arm clamp screws and an arm retention screw.
5. The bicycle drive assembly comprising:
a bicycle motor comprising:
i. a motor chainring spindle; and
ii. a motor crank spindle;
a bicycle chainring installed onto the motor chairing spindle;
a drive side crank arm including a clamp slot space and a crank arm spindle hole having a central axis, wherein the motor crank spindle is positioned at least partially through the crank arm spindle hole along the central axis, and further wherein a gap formed by the clamp slot space prevents the drive side crank arm from fully surrounding the crank arm spindle hole about the central axis; and
d. a seal ring fitted to a crank-seal mating surface of the drive side crank arm, wherein a crank slot tab of the seal ring extends into the clamp slot space of the drive side crank arm to provide a complete seal at the bicycle chainring.
6. The bicycle drive assembly of claim 5 , wherein the crank slot tab prevents rotation of the seal ring relative to the drive side crank arm about the crank spindle axis.
7. A seal ring configured for fitting to a crank arm of a bicycle for preventing environmental intrusion from contaminating a drive assembly of the bicycle, the seal ring comprising:
a. a seal through-hole having a central axis;
b. a seal-crank mating face that is non-parallel with the central axis for fitting a crank seal mating surface of the crank arm, wherein the seal-crank mating face faces toward the seal through-hole; and
c. one or more seal crank retention lips extending from a middle of the seal-crank mating face toward the central axis for mating with one or more arm seal grooves of the crank arm.
8. The seal ring of claim 7 , further comprising a seal crank slot tab.
9. The seal ring of claim 8 , wherein the seal crank slot tab of the seal ring fills a clamp slot space of the crank arm to provide a complete seal.
10. The seal ring of claim 8 , wherein the seal crank slot tab prevents rotation of the seal ring relative to the drive side crank arm about the crank spindle axis.
11. The seal ring of claim 7 , wherein the crank arm comprises a drive side crank arm.
12. The seal ring of claim 7 , wherein the bicycle comprises a motor.
13. A method of protecting a bicycle drive assembly from contamination, the method comprising:
installing a bicycle chainring onto a motor chainring spindle of a motor of the bicycle;
fitting a seal ring to a crank-seal mating surface of a crank arm spindle hole; and
installing the crank arm spindle hole of the crank arm onto a motor crank spindle of the motor of the bicycle such that the crank-seal mating surface faces away from the crank arm spindle hole and toward the motor.
14. The method of claim 13 , wherein the motor chainring spindle and the motor crank spindle are concentric about a crank spindle axis of the bicycle drive assembly.
15. The method of claim 13 , wherein one or more crank seal retention lips of the seal ring mate with one or more arm seal grooves of the drive side crank arm to fit the seal ring to the drive side crank arm.
16. The method of claim 13 , wherein the crank arm is fitted to the motor crank spindle by one or more arm clamp screws and an arm retention screw.
17. The method of claim 13 , wherein the crank arm comprises a drive side crank arm.
18. The method of protecting a bicycle drive assembly from contamination, the method comprising:
installing a bicycle chainring onto a motor chainring spindle of a motor of the bicycle;
fitting a seal ring to a crank-seal mating surface of a crank arm, the crank arm including a clamp slot space and a crank arm spindle hole having a central axis; and
positioning a motor crank spindle of the motor of the bicycle at least partially through the crank arm spindle hole along the central axis, wherein a gap formed by the clamp slot space prevents the drive side crank arm from fully surrounding the crank arm spindle hole about the central axis and a crank slot tab of the seal ring extends into the clamp slot space of the crank arm to provide a complete seal at the bicycle chainring.
19. The method of claim 18 , wherein the crank slot tab prevents rotation of the seal ring relative to the crank arm about the crank spindle axis.