Variable Diameter Crank System for Uniform Torque Transfer
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Solution Overview
Problem
Conventional bicycle drive train systems experience non-uniform torque distribution during pedaling, as the cyclic force application results in varying torque throughout the 360° rotation, with uniformity mainly occurring when the force is tangent to rotation.
Innovation Solution
A crank system with a rotating bar fixedly coupled to an axle, featuring crank assemblies and pedals aligned to rotate the wheel gear assembly optimally at zenith and nadir positions, ensuring consistent torque transfer through the use of adjustable radii and crank arm lengths for uniform pedaling motion conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional round chain wheel is used with moveable chain interface, then the wheel can rotate and the bicycle can move forward, but the torque provided to the wheel is not uniform throughout the 360° rotation cycle
Solution Approach 1:
The patent applies the dynamics principle by making the chain wheel geometry variable rather than fixed. The chain wheel comprises a first portion with a first effective diameter and a second portion with a second effective diameter, where the effective diameter changes along the circumference. This dynamic geometry allows the system to adapt the torque transmission characteristics during rotation, compensating for the non-uniform torque distribution inherent in conventional circular wheels and achieving more uniform overall torque delivery throughout the 360° cycle.
2Reliability
If the chain wheel is made with varying effective diameter portions, then torque uniformity is improved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the chain wheel into distinct portions along its circumference. The chain wheel comprises a first portion with a first effective diameter and a second portion with a second effective diameter, where each portion can be independently designed and manufactured. This segmentation allows the complex variable-diameter geometry to be broken down into manageable sections that can be produced using standard manufacturing techniques, reducing the overall complexity while maintaining the torque-uniforming function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves more uniform torque transfer to the wheel, enhancing pedaling efficiency and bicycle motion by aligning the rotating bar with the gear system at critical pedal positions, thereby improving the overall pedaling experience.
Implementation Method 1
A drive train system of a bicycle is designed to translate a bicyclist's rotational pedaling motion and the power related thereto into linear motion
Implementation Method 2
a first crank assembly coupled to the first end of the first axle and coupled to a first pedal, and a second crank assembly coupled to a second end of the first axle and a second pedal
Data Source
AI summary
A crank system of the present disclosure has a rotating bar that is fixedly coupled to a first end of a first axle and for actuating a wheel, a first crank assembly coupled to the first end of the first axle and coupled to a first pedal, and a second crank assembly coupled to a second end of the first axle and a second pedal. The first crank assembly and the second crank assembly are coupled to the first axle such that the rotating bar is aligned with a wheel gear assembly adapted for rotating the wheel when the first pedal and second pedal are at their zenith and nadir positions, alternatively.