Golf Club Head Stiffness Measurement Using Inverted Drop Test
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Solution Overview
Problem
Existing methods for measuring the stiffness characteristics of golf club heads, such as the pendulum test, face challenges in maintaining constant collision velocity and angle due to the integrated shaft and natural vibration, leading to reduced measurement accuracy and complexity in the manufacturing process.
Innovation Solution
A stiffness characteristic measurement method and device that adjusts the drop distance of a colliding object to maintain constant collision velocity across measurement points on a curved surface, using a holding mechanism, dropping mechanism, accelerometer, and drop distance changing unit to ensure accurate and stable measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pendulum test is used to measure stiffness characteristic of golf club head, then the measurement can be performed, but the shaft portion needs to be held which complicates the process and causes rotation instability
Solution Approach 1:
The invention extracts and removes the shaft from the measurement system, measuring only the golf club head. This eliminates the need to hold and stabilize the shaft, simplifying the measurement process while maintaining accuracy by focusing on the head's stiffness characteristics independently.
Solution Approach 2:
The measurement process is segmented into independent components: the golf club head is measured separately from the shaft. The head is held in a fixed jig at a specific position, allowing independent measurement without the complexity of integrating shaft handling and stabilization.
2Ease of operation
If the shaft is held during measurement, then the test can be performed, but the shaft is likely to rotate in the circumferential direction making it difficult to set constant collision angle
Solution Approach 1:
By removing the shaft from the measurement system entirely, the invention eliminates the rotation stability problem. Only the golf club head remains, which is securely held in a fixed jig, ensuring stable and repeatable collision angle settings without shaft interference.
3Measurement precision
If measurement is performed on integrated head and shaft, then the test can be conducted, but stiffness characteristic may change due to natural vibration of the shaft
Solution Approach 1:
The invention extracts the golf club head from the integrated head-shaft system, eliminating the shaft as a source of harmful vibrations. By measuring only the head in a fixed jig, the measurement is free from shaft natural vibration influences that would otherwise contaminate the stiffness characteristic data.
4Measurement precision
If pendulum collision method is used, then stiffness measurement can be performed, but it is difficult to hit stably at the lowest point due to head shape characteristics
Solution Approach 1:
Instead of moving the colliding object to hit different points on the curved face surface, the invention inverts the approach by moving the head itself to different positions relative to a fixed colliding object. This maintains stable collision conditions while achieving measurements at multiple face surface locations.
5Measurement precision
If measurement is performed at multiple measurement points on curved face surface, then comprehensive evaluation is achieved, but collision distance changes due to bulge and roll reducing measurement accuracy
Solution Approach 1:
The invention inverts the measurement approach by moving the head to different positions relative to a fixed colliding object, rather than moving the colliding object to different points on the curved surface. This maintains constant collision distance while enabling comprehensive evaluation of multiple face surface locations, resolving the accuracy-versus-coverage contradiction.
Data Source
AI summary
A stiffness characteristic measurement device holds a golf club head with a face surface facing upward, drops a collision rod vertically toward the face surface, and calculates the stiffness characteristic of the golf club head based on a detection value of an accelerometer attached to the collision rod. Every time the measurement point on the face surface is changed, a drop distance changing step of adjusting the drop distance of the collision rod is performed so that the collision velocity of the collision rod to the measurement point is substantially constant.