Variable Valley Radius Sprocket for Higher Climbing Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cyclists face significant fatigue when climbing steep or long hills due to the constant pull of gravity, which is exacerbated by a decrease in pedaling cadence and an increase in torque output, leading to accelerated muscle exhaustion.
Innovation Solution
A sprocket design with varying gear tooth valley radii around the perimeter, featuring a combination of reduced and increased radii in alternating patterns, allowing for increased gear torque multiplication without changing the number of gear teeth, thereby maintaining a comfortable pedaling cadence and reducing fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a rider maintains a comfortable cadence while climbing, then fatigue is delayed, but the torque output increases leading to accelerated muscle exhaustion
Solution Approach 1:
The sprocket applies local quality by varying the valley radius at different circumferential positions. Specific valleys have reduced radii while others have increased radii, creating localized variations in the engagement characteristics. This allows different portions of the pedal stroke to experience optimized torque multiplication, enabling the rider to maintain comfortable cadence with reduced torque output at critical points.
2Force
If larger rear sprockets are used to increase gear torque multiplication, then climbing becomes easier, but the number of gear teeth increases
Solution Approach 1:
The invention changes the geometric parameter of the valley radius rather than increasing the number of teeth. By reducing the valley radius at specific locations, the effective lever arm is shortened, which increases the torque multiplication factor. This allows achieving higher gear torque multiplication with the same number of teeth, avoiding the need for larger sprockets with more teeth.
3Force
If the gear tooth valley radius is reduced to increase torque multiplication, then climbing performance improves, but the chain engagement smoothness may be affected
Solution Approach 1:
The sprocket employs asymmetry by having different valley radii at different circumferential positions rather than a uniform radius. This asymmetric configuration creates varying engagement characteristics throughout the rotation, where reduced valleys provide torque multiplication while increased valleys provide smoothness. The alternating pattern balances both requirements.
Solution Approach 2:
The valley radius variations are arranged in a periodic pattern around the sprocket circumference. This periodic alternation between reduced and increased valleys creates a rhythm in the chain engagement, where the chain experiences alternating phases of high torque multiplication and smooth engagement. This periodic action maintains overall engagement smoothness while providing enhanced torque at critical points.
Data Source
AI summary
A sprocket having a gear tooth valley radius which varies around the sprocket perimeter provides additional gear torque multiplication to a rider, which is especially beneficial when climbing hills. In some embodiments, the sprocket is a bicycle chainring with reduced gear tooth valley radius over at least a portion of the chainring. In other embodiments, the sprocket is a bicycle rear wheel cassette cog with increased gear tooth valley radius over at least a portion of the cassette cog. Regions of both reduced and increased gear tooth valley radius may be present on a given sprocket. The sprocket valley floor surface may be rounded or may include N segments adjoined by N vertices. The segments of the valley floor surface may be curved or straight. The vertices of the valley floor surface may be curved or angled. Embodiments for bicycles and motorcycles are presented.