Gang Mower Suspension Tuned Mass Dampers
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Solution Overview
Problem
Riding mowers with gang configurations of cutting units often experience a harmonic up and down vertical motion, or 'bobbing motion', which decreases the quality of cut due to varying grass heights, particularly in reel cutting units designed for precise cutting at lower heights.
Innovation Solution
Each cutting unit is equipped with a separate suspension system that includes a lift and lower portion and a ground contour following portion, with a tuned mass damper installed adjacent to the connection between these portions to dampen the undesired vertical bobbing motion, allowing the cutting unit to independently follow ground contours and reduce harmonic motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tuned mass dampers are added to reel cutting units to decrease bobbing motion, then the quality of cut is improved, but the device complexity increases and the available space for the damper is limited
Solution Approach 1:
The tuned mass damper is nested within the existing suspension structure by integrating it with the ground contour following portion. The damper assembly fits within the spatial envelope already defined by the suspension arms and connection points, utilizing the existing structural cavity rather than adding external components. This nesting approach allows the damper to be housed within the suspension assembly without significantly increasing overall device complexity or requiring additional external space.
2Manufacturing precision
If larger tuned mass dampers are used to reduce bobbing motion amplitude, then the quality of cut is improved, but the operational clearance between cutting units and suspensions is reduced
Solution Approach 1:
The tuned mass damper is oriented with its motion axis aligned parallel to the ground contour following portion rather than perpendicular to it. This dimensional reorientation allows the damper to utilize vertical space within the suspension assembly that would otherwise be unused, enabling a larger damper mass to be accommodated without encroaching on the horizontal operational clearance between the cutting unit and suspension components.
3Adaptability or versatility
If the ground contour following portion is made more flexible to improve ground following ability, then the cutting unit's adaptability to terrain is improved, but the harmonic bobbing motion increases
Solution Approach 1:
The tuned mass damper acts as an intermediary element inserted between the ground contour following portion and the cutting unit frame. This mediator absorbs and dissipates the harmful harmonic vibrations that result from the flexible ground following motion, while still allowing the ground contour following portion to maintain its flexibility and adaptability. The damper selectively filters out the resonant frequencies that cause bobbing while permitting the necessary compliant motion for terrain following.
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 implementation of tuned mass dampers in the suspension system effectively reduces the amplitude of bobbing motion, enhancing the quality of cut by maintaining consistent grass height across the swath, particularly in reel cutting units.
Implementation Method 1
At least one tuned mass damper is installed in each suspension adjacent a connection between the ground contour following suspension portion and the lift and lower suspension portion for damping undesired vertical bobbing of the cutting unit.
Implementation Method 2
for damping undesired vertical bobbing of the cutting unit
Data Source
AI summary
A mower includes a plurality of grass cutting units, either reel or rotary, arranged in a gang configuration. Each cutting unit is connected to the mower by a separate suspension that includes a lift and lower portion for lifting and lowering the cutting unit out of and into contact with the ground, respectively. The suspension includes a ground contour following portion permitting the cutting unit to have one or more degrees of freedom relative to the lift and lower portion to independently follow the ground contours the cutting unit encounters. A tuned mass damper is installed in the ground contour following portion of the suspension or is adjacent to a connection between the ground contour following portion and the lift and lower portion for damping undesired vertical bobbing of the cutting unit.