Side-Mounted Cycle Wheel Drive With Lateral Planetary Gear Layout
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Solution Overview
Problem
Existing side-mounted front wheel electric motor drives for bicycles face challenges with cantilevered mounting, leading to excessive weight, noise, and cost due to oversized components, and sub-optimal bearing spacing, which limits torque handling and increases noise and expense.
Innovation Solution
A drive system with a rotary wheel hub bearing positioned laterally between the electric motor and planetary gears, allowing for a larger diameter planetary gearbox using quiet plastic gearing and optimizing bearing spacing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the shaft diameter is increased to account for cantilevered bending force in single side mounted wheels, then the axle can withstand the bending force, but the motor and planetary gears become excessively larger in diameter and higher in weight
Solution Approach 1:
The patent repositions the planetary gearbox from a longitudinal arrangement (along the axle) to a lateral arrangement (perpendicular to the axle), allowing the gearbox to be mounted on the side of the motor housing rather than requiring a larger diameter shaft. This dimensional change enables the axle to maintain its original diameter while the gearbox components are accommodated in the lateral space between the motor and wheel hub.
2Strength
If high strength materials are used to overcome torque limitations in small gears, then the gears can handle higher torques, but noise levels of the gears are higher
Solution Approach 1:
The patent changes the material parameter of the planetary gears from metal to plastic, which inherently reduces noise generation while maintaining sufficient torque handling capability through proper plastic material selection and gear design. This material parameter change allows the system to achieve quiet operation without requiring high-strength metal materials.
Solution Approach 2:
By repositioning the gearbox laterally, the patent enables the use of larger diameter plastic planetary gears that can handle higher torques through increased gear tooth surface area and improved load distribution, rather than relying on high-strength metal materials. The lateral positioning provides the necessary radial space for larger plastic gears.
3Strength
If rotary bearings are mounted on an oversized shaft to contain the planetary gear drive, then the gears can be adequately sized, but the bearings become large and heavy and expensive
Solution Approach 1:
The patent moves the planetary gearbox from a longitudinal position (requiring large diameter bearings on the axle) to a lateral position (mounting bearings on the motor housing or dedicated gearbox housing). This repositioning allows the use of smaller, lighter bearings that support the gearbox laterally rather than requiring oversized axial bearings.
Solution Approach 2:
The patent extracts the planetary gearbox from the axle assembly and mounts it separately on the motor housing or wheel hub, eliminating the need for the axle to serve as the gearbox mounting structure. This separation allows the use of standard-sized bearings independent of the axle diameter.
4Length of moving object
If the distance between front hub bearings is constrained by the single sided fork mounting arm and wheel spokes, then the lateral width is minimized, but the bearing spacing is sub-optimal resulting in higher wheel runout and wobble
Solution Approach 1:
By positioning the planetary gearbox laterally between the motor and wheel hub rather than along the axle, the patent creates additional spatial flexibility. This allows the wheel hub bearings to be optimally spaced along the axle to minimize runout and wobble, while the gearbox occupies the lateral dimension that would otherwise be constrained by the single-sided fork mounting.
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
This configuration enables a compact, quiet, and cost-effective design with improved torque handling and reduced noise, while maintaining optimal bearing spacing for side-mounted wheel applications.
Implementation Method 1
a planetary gear reduction assembly positioned at least partially within the wheel hub and comprising one or more planetary gears
Implementation Method 2
a rotary wheel hub bearing rotatably coupling the wheel hub to the motor drive
Data Source
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AI summary
A drive system for a side mounted cycle wheel, comprising a wheel hub for mounting the side mounted cycle wheel; a motor drive for driving the side mounted cycle wheel, the motor drive comprising an electric motor and a planetary gear reduction assembly positioned at least partially within the wheel hub and comprising one or more planetary gears; and, a rotary wheel hub bearing rotatably coupling the wheel hub to the motor drive, wherein the rotary wheel hub bearing is positioned laterally between the electric motor and the planetary gears.