Golf swing analysis and method of custom trimming golf club shafts

• US 5,478,073 A
• Filed: 09/16/1994
• Issued: 12/26/1995
• Est. Priority Date: 12/30/1992
• Status: Expired due to Fees

• Current Assignee: Lloyd E Hackman
• Original Assignee: Lloyd E Hackman
• Inventors: Hackman, Lloyd E.
• Primary Examiner(s): Marlo, George J.
• Application Number:
  US08/307,917
• Time in Patent Office: 466 Days
• Field of Search: 273/77 A, 273/80 B
• US Class Current: 473/289
• CPC Class Codes: A63B 2220/40 Acceleration
• CPC Class Codes: A63B 2220/51 Force
• CPC Class Codes: A63B 2220/62 Time or time measurement used for time reference, time stamp, master time or clock signal
• CPC Class Codes: A63B 2220/64 Frequency, e.g. of vibration oscillation
• CPC Class Codes: A63B 2220/801 Contact switches
• CPC Class Codes: A63B 2220/803 Motion sensors
• CPC Class Codes: A63B 2220/833 Sensors arranged on the exercise apparatus or sports implement
• CPC Class Codes: A63B 53/10 Non-metallic shafts
• CPC Class Codes: A63B 60/002 Resonance frequency related characteristics
• CPC Class Codes: A63B 60/42 Devices for measuring, verifying, correcting or customising the inherent characteristics of golf clubs, bats, rackets or the like, e.g. measuring the maximum torque a batting shaft can withstand
• CPC Class Codes: A63B 69/3632 Clubs or attachments on clubs, e.g. for measuring, aligning A63B69/3614 takes precedence; clubs for swinging exercises in general A63B15/00

Abstract

A method of custom trimming golf club shafts comprising (i) measuring the frequency of oscillation, f_c, of a representative shaft at a plurality of different tipping amounts and effective shaft lengths, (ii) calculating the moment, m_c, of the replica shaft for each effective shaft length, (iii) performing a linear regression on the measured frequencies to obtain the coefficients A and B in the form

f.sub.c =A+C*tipping amount+B*m.sub.c,

(iv) selecting an inventory shaft having a known natural frequency, f_c, at a selected moment, m_c, and (v) calculating the constant C=f_c -B*m_c. The tipping amount is calculated from the equation

tipping amount=(f.sub.g -C-B*m.sub.g)÷A

where m_g is the desired moment and f_g is the desired natural frequency of a golfer'"'"'s finished golf club. A length of the narrow end of the inventory shaft equal to the tipping amount is removed and a length of the grip end of the inventory shaft may also be removed if necessary.

Claims

1. A method for custom trimming a golf club shaft at locations which form the shaft with both a length appropriate for an individual golfer'"'"'s golf club and a natural frequency of oscillation, f_g, in a cantilevered beam mode of oscillation in which a narrow end of the shaft oscillates along an arcuate path about a grip end of the shaft, wherein f_g has been predetermined for that golfer'"'"'s golf club, the method comprising:

(a) measuring the natural frequency of oscillation, f_c, of a replica shaft representative of a specified type of shaft at a plurality of different effective shaft lengths, and at a plurality of different tipping amounts for each effective shaft length over a range of effective shaft lengths and a range of tipping amounts;

(b) calculating the moment, m_c, of the replica shaft for each of said plurality of different effective shaft lengths;

(c) performing a linear regression on the frequency measurements to get the coefficients A, B and C for an equation algebraically approximating the measured natural frequency data in the form

space="preserve" listing-type="equation">f.sub.c =C+A*tipping amount+B*m.sub.c ;

(d) selecting, from inventory, a shaft which has been measured to determine its natural frequency of oscillation, f_c, at a selected moment;

(e) calculating the tipping amount of the inventory shaft from the equation

space="preserve" listing-type="equation">tipping amount=(f.sub.g -C-B*m.sub.g)÷

A

where m_g is the desired moment of the golfer'"'"'s golf club;

(f) removing a length of the narrow end of the inventory shaft equal to the tipping amount; and

(g) removing a length of the grip end of the inventory shaft equal to an initial shaft length minus both the tipping amount and the desired final shaft length.

2. A method for custom trimming a golf club shaft at locations which form the shaft with both a length appropriate for an individual golfer'"'"'s golf club and a natural frequency of oscillation, f_g, in a cantilevered beam mode of oscillation in which a narrow end of the shaft oscillates along an arcuate path about a grip end of the shaft, wherein f_g has been predetermined for that golfer'"'"'s golf club, the method comprising:

(a) measuring the frequency of oscillation, f_c, of a replica shaft representative of a specified type of shaft at a plurality of different effective shaft lengths and a plurality of different tipping amounts for each effective shaft length over a range of shaft lengths and a range of tipping amounts;

(b) calculating the moment, m_c, of the replica shaft for each of said plurality of different effective shaft lengths;

(c) calculating the quotient, A of (i) the difference between the measured frequencies for a pair of different tipping amounts at the same effective replica shaft length, and (ii) the difference between the same pair of tipping amounts;

(d) calculating the quotient, B of (i) the difference between a pair of measured frequencies for a selected tipping amount and (ii) the difference between two moments for the effective replica shaft lengths at the same pair of measured frequencies;

(e) selecting, from inventory, a shaft which has been measured to determine its natural frequency of oscillation, f_c, for a selected moment, m_c, and then calculating the constant, C for the inventory shaft, wherein

space="preserve" listing-type="equation">C=f.sub.c -B*m.sub.c ;

(f) calculating the tipping amount for the inventory shaft, wherein

space="preserve" listing-type="equation">tipping amount=(f.sub.g -C-B*m.sub.g)÷

A

where m_g is the desired moment of the golfer'"'"'s golf club;

(g) removing a length of the narrow end of the inventory shaft equal to the tipping amount; and

(h) removing a length of the grip end of the inventory shaft equal to the initial shaft length minus both the tipping amount and the desired final shaft length.

3. A method in accordance with claim 2, wherein data obtained for frequency, f_c, and moment, m_c, are graphed, forming a curve for each tipping amount and a plurality of curves for each shaft type.

4. A method in accordance with claim 3, wherein a plurality of curves are graphed for a plurality of different shaft types.

5. A method in accordance with claim 3, wherein the quotient, A is equal to (i) the difference between frequency measurements for a pair of different tipping amounts at the same effective replica shaft length divided by (ii) the difference between the same pair of tipping amounts.

6. A method in accordance with claim 5 wherein the quotient, B is equal to (i) the difference between a pair of frequency measurements for a selected tipping amount divided by (ii) the difference between two moments for the same effective replica shaft lengths as the pair of frequency measurements.

7. A method in accordance with claim 6, wherein the method is used to locate the cuts on a plurality of golf club shafts for forming a shaft of desired characteristics for each golf club in a set of clubs.

8. A method for custom trimming a golf club shaft at locations which form the shaft with both a length appropriate for an individual golfer'"'"'s golf club and a natural frequency of oscillation, f_g, in a cantilevered beam mode of oscillation in which a narrow end of the shaft oscillates along an arcuate path about a grip end of the shaft, wherein f_g has been predetermined for that golfer'"'"'s golf club, and wherein the constants A and B have been predetermined for a replica shaft representative of a specified type of shaft and the constant C has been predetermined for an inventory shaft, the method comprising:

(a) calculating the tipping amount of the inventory shaft, wherein

space="preserve" listing-type="equation">tipping amount=(f.sub.g -C-B*m.sub.g)÷

A

where m_g is the desired moment of the golfer'"'"'s golf club;

(b) removing a length of the narrow end of the inventory shaft equal to the tipping amount; and

(c) removing a length of the grip end of the inventory shaft equal to the initial shaft length minus both the tipping amount and the desired final shaft length.

9. A method for custom trimming a golf club shaft at locations which form the shaft with both a length appropriate for an individual golfer'"'"'s golf club and a natural frequency of oscillation, f_g, in a cantilevered beam mode of oscillation in which a narrow end of the shaft oscillates along an arcuate path about a grip end of the shaft, wherein f_g has been predetermined for that golfer'"'"'s golf club, the method comprising:

(a) estimating the tipping amount necessary to form a shaft having the desired natural frequency of oscillation, f_g ;

(b) removing a length of the narrow end of the shaft equal to the estimated tipping amount;

(c) measuring the natural frequency of oscillation, f_c, of the shaft by (i) attaching a weight to the narrow end of the shaft, (ii) rigidly mounting a portion of the grip end of the shaft with the distance between the center of the weight and the distal, mounted portion of the grip end being the appropriate length for the individual golfer'"'"'s club, (iii) displacing and subsequently releasing the narrow end and (iv) measuring the frequency of the oscillations of the narrow end along the arcuate path about the grip end;

(d) repeating the steps of estimating the tipping amount, removing a length of the narrow end of the shaft and measuring the natural frequency, f_c, if the measured natural frequency of oscillation, f_c, is substantially less than the desired natural frequency, f_g, of the golfer'"'"'s golf club, wherein the repeated measuring step further comprises rigidly mounting the shaft at a portion of the grip end spaced from the previous mounting portion a distance equal to the amount removed from the shaft to maintain the distance between the center of the weight and the distal, mounted portion of the grip end as the appropriate length for the individual golfer'"'"'s golf club; and

(e) removing a length of the grip end of the shaft equal to the initial shaft length minus both the tipping amount and the desired final shaft length.

10. A method in accordance with claim 9, wherein rigidly mounting the shaft further comprises firmly clamping the grip end.