Wrestplank Grain Orientation for Tuning Stability
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Solution Overview
Problem
Multi-laminate wood pin blocks in pianos often experience tuning instability due to excessive glue thickness or layer quantity, leading to rapid wear and loosening of tuning pins, which affects the instrument's ability to stay in tune.
Innovation Solution
A multilayer wrestplank design with specifically oriented grain directions in its working plies, including outer and median plies, provides a stable and secure tuning pin hole configuration, minimizing the 'slip-stick' phenomenon and maintaining dimensional stability, with a greater percentage of end grain bearing string loads to resist deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If multi-laminate wood planks with excessive glue thickness or excessive quantity of layers are used, then the pin block can be manufactured more easily, but tuning instability occurs
Solution Approach 1:
The patent specifies precise parameters for glue layer thickness (0.002 to 0.006 inches) and the number of wood layers (5 to 11 layers), transforming the manufacturing process from using excessive materials to using controlled, optimized quantities that maintain tuning stability while remaining manufacturable
Solution Approach 2:
The pin block uses a composite structure of multiple wood layers (maple, beech, bubinga) with controlled glue layers, where the alternating grain directions and specific layer compositions create a material that resists deformation and maintains tuning stability
2Ease of operation
If constant turning of the tuning pin occurs, then the tuning pin can be adjusted to different pitches, but the wood rapidly wears down and the tuning pin hole enlarges
Solution Approach 1:
The multi-layer wood composite structure with alternating grain directions creates a more durable material that resists wear from constant tuning pin rotation, preventing rapid hole enlargement while still allowing tuning adjustments
Solution Approach 2:
The patent uses different wood species (maple, beech, bubinga) with specific grain orientations in different layers, creating local variations in density and hardness that optimize resistance to wear at the tuning pin hole while maintaining overall pin block integrity
3Ease of manufacture
If the direction of grain in each layer is disposed at an angle of approximately 45° to the direction of grain in opposing surfaces of adjacent layers, then the pin block can be manufactured with standard lamination techniques, but tuning instability occurs
Solution Approach 1:
The patent changes the grain angle parameter from the conventional 45° to specific angles of 0°, 30°, 45°, 60°, or 90° with respect to the longitudinal axis, where at least one layer has 0° or 90° orientation, creating optimized grain patterns that improve tuning stability while remaining manufacturable
4Reliability
If seven or more laminations with grain directions substantially perpendicular to opposing surfaces are used, then the pin block structure becomes more complex, but tuning stability improves
Solution Approach 1:
The patent applies different grain orientations (0°, 30°, 45°, 60°, or 90°) to different layers based on their specific functional requirements, with outer layers having 0° or 90° orientations for stability and inner layers having varied orientations for wear resistance, creating a locally optimized structure
Solution Approach 2:
The patent optimizes the number of layers to a specific range (5 to 11 layers) rather than simply increasing complexity, and controls glue layer thickness to 0.002 to 0.006 inches, achieving tuning stability through parameter optimization rather than sheer complexity
Data Source
AI summary
A wrestplank for use in a stringed instrument including first and second median working plies stacked in between first and second outer working plies. Each working ply defines a direction of grain. The working plies collectively define a tuning pin hole configured to securely receive a tuning pin, whereby the tuning pin is substantially surrounded by and in engagement with end wood of the working plies. The directions of grain of the outer working plies are oriented substantially parallel with respect to a longitudinal axis defined by the wrestplank. The grain direction of the first median working ply is oriented at an angle of between about 60° and about 75° with respect to the longitudinal axis, and the grain direction of the second median working ply is oriented at an angle of between about 105° and about 120° with respect to the longitudinal axis.