Nested Half-Sprocket Track Drive for Reduced Scrub Radius
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Solution Overview
Problem
Current track drives for outdoor power equipment face challenges such as lateral derailment, drive lug skipping, backlash during load and direction reversals, and high steering force requirements due to large scrub radius and footprint, limiting performance in vehicles like electric lawn maintenance vehicles.
Innovation Solution
A track drive system featuring nested interior and exterior half sprockets with a central support frame, hub bearing, and idler wheels, which reduces scrub radius and allows for easier installation and replacement, enabling improved traction and steering capabilities by distributing weight evenly and reducing bending moments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional unitary sprockets or removable sector sprockets are used, then track installation and removal is facilitated, but lateral derailment, drive lug skipping, and backlash impacts occur during load and direction reversals
Solution Approach 1:
The drive sprocket is divided into two separate half-sprockets (interior and exterior) that are positioned on opposite sides of the support frame. Each half-sprocket independently engages with the track, providing continuous engagement and eliminating backlash while maintaining ease of installation and removal.
Solution Approach 2:
The interior half-sprocket nests within the exterior half-sprocket, with both half-sprockets positioned on either side of the support frame. This nested configuration provides continuous track engagement from both interior and exterior sides, preventing lateral derailment and drive lug skipping while facilitating easy installation.
2Reliability
If conventional track drive configurations are used, then track engagement is achieved, but large scrub radius and footprint result in high steering force requirements
Solution Approach 1:
The half-sprockets are positioned on either side of the support frame in the vertical dimension, creating interior and exterior engagement points. This dimensional arrangement reduces the horizontal scrub radius while maintaining reliable track engagement, thereby reducing the steering force required.
Solution Approach 2:
The interior and exterior half-sprockets are positioned asymmetrically relative to the support frame, with the interior half-sprocket engaging from the inside and the exterior half-sprocket engaging from the outside. This asymmetric positioning optimizes the scrub radius and reduces steering force requirements while maintaining track engagement.
3Ease of operation
If removable sector sprockets are used, then installation and removal is easier, but track engagement continuity is compromised leading to backlash impacts
Solution Approach 1:
The drive sprocket is segmented into two permanent half-sprockets (interior and exterior) that are independently mounted on opposite sides of the support frame. This segmentation allows each half-sprocket to be independently installed and removed while maintaining continuous track engagement, eliminating backlash impacts without compromising ease of operation.
Solution Approach 2:
The support frame acts as an intermediary structure that holds both interior and exterior half-sprockets in fixed positions. This intermediary framework ensures continuous track engagement from both sides while allowing the half-sprockets to be independently installed or removed, maintaining both ease of operation and engagement continuity.
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 solution significantly reduces scrub radius, enhances steering efficiency, and maintains the same ground speed and handling characteristics as pneumatic tires, making the track drive system more steerable and reducing the need for gear adjustments.
Implementation Method 1
A hub bearing is mounted on the drive axle and the support frame enabling the drive axle to rotate relative to the support frame
Implementation Method 2
The drive sprocket is movably engaged with an endless track to transmit force to rotate the endless track and propel the outdoor power equipment
Data Source
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AI summary
A track drive for outdoor power equipment has a support frame with a centerline and a hub bearing attached to the support frame. A drive sprocket having a nesting interior half and exterior half is attached to the hub bearing, which enables the drive sprocket to rotate relative to the support frame. The drive sprocket is attached to an associated drive hub of a piece of outdoor power equipment. Drive sprocket teeth are spaced radially about the drive sprocket, with a first set of drive teeth attached to the interior half sprocket and located on an interior side of the support frame. A second set of drive teeth are attached to the exterior half sprocket and located on an exterior side of the support frame. The drive sprocket transmits a rotational force to an endless track to rotate the endless track and propel the outdoor power equipment.