Adjustable Engine Accessory Mount for Thermal Expansion and Vibration
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Solution Overview
Problem
Conventional mounting arrangements for aircraft engine accessories, such as the '3-2-1' configuration, can lead to reduced stiffness and unwanted vibrations due to thermal expansion and stack-up issues, while attempts to increase stiffness through additional constraints may cause thermal expansion problems.
Innovation Solution
An adjustable mount system comprising a first bracket coupled to the engine accessory and a second bracket coupled to the engine, with a threaded stud and annular bushings that allow for axial adjustment and rotational movement, enabling the adjustment of the axial gap between the brackets to accommodate thermal expansion and reduce vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If additional constraints are added to attachment points to increase stiffness, then vibration resistance improves, but thermal expansion and stack-up issues worsen
Solution Approach 1:
The mounting bracket incorporates a spherical joint that enables dynamic adjustment of the mounting position. This allows the bracket to adapt its position in response to thermal expansion and stack-up variations, maintaining proper constraints without rigid fixed positions that would cause stress
Solution Approach 2:
The system allows changing the mounting position parameters through the spherical joint mechanism. By adjusting the position parameters dynamically, the system can accommodate thermal expansion while maintaining adequate stiffness through proper geometric constraint configuration
2Object-affected harmful factors
If fewer constraints are used in mounting arrangement, then thermal expansion accommodation improves, but stiffness and vibration control worsen
Solution Approach 1:
The spherical joint provides dynamic adaptability, allowing the mounting system to achieve adequate stiffness through optimal geometric configuration rather than relying on excessive fixed constraints. The dynamic positioning capability ensures thermal expansion accommodation while maintaining structural rigidity
3Manufacturing precision
If fixed mounting positions are used, then manufacturing precision is improved, but adaptability to thermal expansion and stack-up worsens
Solution Approach 1:
The spherical joint transforms the fixed mounting position into a dynamically adjustable position. The mechanism maintains precise mounting through controlled degrees of freedom while adapting to thermal expansion and stack-up variations, combining precision with flexibility
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 adjustable mount system effectively reduces vibrations and accommodates thermal expansion, improving the dynamic behavior and stiffness of the mounted accessory by allowing for adjustable positioning and constraint in multiple degrees of freedom.
Implementation Method 1
A typical mounting arrangement is known as a '3-2-1' arrangement... This arrangement may reduce stresses caused by stack-up or mismatches during assembly and thermal expansion during operation
Implementation Method 2
the first bracket includes a spherical bearing disposed about the bore in the first bracket such that the threaded stud extending axially through the first annular bushing is articulable relative to the spherical bearing
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A first bracket adapted (42) to be coupled to an aircraft engine accessory (30) has a first bore with a first annular bushing (54) with a threaded radially inner surface extending through the first bore. A second bracket (44) operatively coupled to an engine (10) at mounting location (L1) has a second bore with a second annular bushing (54) with a threaded radially inner surface extending through the second bore. A threaded stud (52) extends axially through the first and second bushings (54) and is engaged with their threaded inner surfaces. Rotation of the first and/or second bushings (54) varies the relative axial positions of the first and second bushings (54) on the stud, thereby adjusting an axial gap between first and second brackets (42, 44). First and second nuts (56) axially retain the mount (40', 40) together with the axial gap between the first and second brackets (42, 44) fixed.