Passive Hub Flapping Lock for Rotorcraft
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Solution Overview
Problem
Rotor flapping in rotorcraft can cause damage to the mast sleeve or rotor when they are stationary or rotating slowly, necessitating a lightweight, automatic prevention mechanism.
Innovation Solution
A passive hub flapping lock system comprising stop wedges, frames, rods, lever arms, weight sets, and pivot torsion springs that engage at low rotational speeds to prevent flapping and disengage at higher speeds, utilizing elastomeric materials and coatings to reduce friction and facilitate smooth motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flapping lock mechanism is installed to prevent rotor flapping, then rotor safety is improved, but device complexity increases
Solution Approach 1:
The flapping lock mechanism employs dynamic elements including lever arms that can pivot between engaged and disengaged positions, stop wedges that can be positioned to contact or clear the rotor, and weight sets that move in response to rotational speed changes. This dynamic configuration allows the system to automatically adapt to different operational conditions without requiring complex control systems.
Solution Approach 2:
The mechanism utilizes the rotor's own rotational speed to control the locking action through centrifugal force acting on the weight sets. When the rotor rotates below a predetermined speed, the weights remain in position to engage the stop wedges and prevent flapping. When rotation exceeds the threshold, centrifugal force automatically moves the weights outward, disengaging the lock. This self-regulating behavior eliminates the need for external sensors or actuators.
2Ease of operation
If friction-reducing coatings are applied to rod sleeves, then motion smoothness is improved, but manufacturing complexity increases
Solution Approach 1:
The invention modifies the surface properties of the rod sleeves by applying friction-reducing coatings that change the coefficient of friction between the rod and sleeve surfaces. This parameter change enables smoother relative motion during the engagement and disengagement of the flapping lock mechanism, reducing wear and improving operational reliability.
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
Effectively prevents rotor flapping at low rotational speeds and above, ensuring the safety and integrity of both the rotor and mast sleeve by automatically adjusting the position of stop wedges, thus reducing the risk of damage.
Implementation Method 1
one or more pivot torsion springs, each pivot torsion spring positioned at a pivot and biased to hold the flapping lock in an engaged position when stationary or at a rotational speed below a specified rotational speed
Implementation Method 2
the flapping lock is in a disengaged position when at a rotational speed above the specified rotational speed and the one or more weight sets move outward, rotating the one or more lever arms
Implementation Method 3
at least a portion of each of the one or more rod sleeves adjacent to a mast sleeve or a mast is coated with one or more substances to reduce a friction of a motion of the one or more rod sleeves against the mast sleeve or the mast
Data Source
AI summary
A passive hub flapping lock including: one or more lever arms, each lever arm rotatably coupled to a pivot and comprising a first lever arm end and a second lever arm end; one or more stop wedges; one or more frames coupled to the one or more stop wedges, each frame coupled to the first lever arm end of one of the one or more lever arms; one or more weight sets, each weight set comprising one or more weights coupled to the second lever arm end of one of the one or more lever arms; and one or more pivot torsion springs, each pivot torsion spring positioned at the pivot.