Carbide Insert Cleat Pedal Assembly Friction Control
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Solution Overview
Problem
Clipless pedals for off-road cycling often experience difficulties in engaging and releasing the cleat due to high stress, high load, and high friction, leading to potential seizing or cold-welding of metal contact surfaces, which can hinder the rider's ability to disengage safely, especially in wet or dirty conditions.
Innovation Solution
The use of materials with a hardness greater than hardened steel, such as carbides (silicon carbide, boron carbide, tungsten carbide, and titanium carbide), for the contacting surfaces of the cleat and pedal assembly, along with specific retainer configurations and cam surfaces, to reduce friction and prevent seizing, ensuring reliable engagement and release under various environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal contact surfaces (hardened steel) are used in the cleat and pedal assembly, then the material strength and durability are improved, but the coefficient of friction increases leading to seizing or cold-welding that prevents reliable release
Solution Approach 1:
A carbide insert is introduced as an intermediary component between the metal cleat and metal pedal contact surfaces. The carbide insert has a lower coefficient of friction compared to metal-on-metal contact, preventing seizing and cold-welding while maintaining the structural strength of the metal components. The insert is retained by a spring-loaded retainer mechanism that allows it to be pressed into place during engagement and automatically ejected during release.
Solution Approach 2:
The solution employs a composite structure combining metal (for strength) and carbide (for low friction). The carbide insert is made of material such as silicon carbide, boron carbide, tungsten carbide, or titanium carbide, which provides exceptional hardness and low friction properties. This composite approach allows the system to benefit from both the strength of metal and the low friction of carbide materials.
2Duration of action of stationary object
If the cleat and pedal contacting surfaces are made of hardened steel, then the wear resistance is improved, but the adhesive friction increases causing the cleat to seize and preventing safe disengagement
Solution Approach 1:
The carbide insert serves as a mediator between the hardened steel cleat and pedal surfaces. During engagement, the insert is pressed into the pedal cavity by a spring-loaded retainer, creating a low-friction interface. During disengagement, the spring force ejects the insert, allowing the cleat to release smoothly without adhesive friction, while the hardened steel components maintain their wear resistance.
Solution Approach 2:
The solution changes the friction parameter by introducing carbide material with inherently lower coefficient of friction. The spring mechanism dynamically changes the position of the carbide insert between engaged and disengaged states, optimizing both wear resistance during riding and ease of disengagement when needed.
Data Source
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AI summary
A pedal and cleat assembly comprises a pedal body having a first end and a second end, a first retainer mounted proximate the first end of the pedal body, and a second retainer mounted proximate the second end of the pedal body. The cleat assembly is configured to be releaseably coupled to the pedal assembly and comprises a cleat body having at least one coupling area, and at least one element shaped to be maintained within or disposed on the coupling area. The at least one coupling area is positioned at a forward or rearward end of the cleat body so that the at least one element can act as a cam surface against the first or second retainer. The at least one element is configured to rotate or articulate when maintained within or disposed on the coupling area to facilitate releasing the cleat assembly from the pedal assembly.