Abstract:
The holy grail of golf is to create a set of clubs that facilitate a consistent swing one where the golfer&#39;s tempo and/or ball striking accuracy remain relatively constant between clubs. The human body is such that tempo changes as shaft length and club head weight are varied. By measuring tempo at various length and weight combinations and forming a range of length/weight combinations that produce a consistent swing, it is possible to construct a set of golf clubs that meets target distances while maintaining tempo and accuracy.

Description:
RELATED APPLICATIONS  
       [0001]    The present application claims priority to U.S. Provisional Application No. 60/276,663, filed Mar. 16, 2001, the teachings of which are hereby incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to a method for creating a set of golf clubs with shaft lengths and club head weights that maintain a golfer&#39;s tempo and/or ball striking accuracy within an acceptable range.  
         BACKGROUND OF THE INVENTION  
         [0003]    The holy grail of golf is to create a set of clubs that facilitate a consistent swing one where the golfer&#39;s tempo and/or ball striking accuracy remains relatively constant across clubs. However, in order to produce different ball flights (distance and trajectory) most club makers vary the shaft lengths and head weights of clubs within a set. Each new length/weight combination implies a new angle of attack, which has led some to contend that the golf swing (ignoring putting which is a world unto itself) is really thirteen different swings, one for each club in the bag.  
           [0004]    The prior art has approached this problem in many ways. “Swing weighting” (see, for example, U.S. Pat. Nos. 5,228,688 to Davis and 4,674,324 to Benoit), “moments of inertia matching” (see, for example, U.S. Pat. Nos. 6,007,431 to Bloom, Jr.; 5,769,733 to Williams et al.; and 4,415,156 to Jorgensen) and “frequency matching” (see, for example, U.S. Pat. No. 5,591,091 to Hackman) attempt to make clubs of different lengths feel the same. Requiring that all clubs be the same length or that there be a limited number of different shaft lengths has also been proposed (see, for example, U.S. Pat. Nos. 4,784,390 to Horgen and 3,984,103 to Nix).  
           [0005]    None of these methods address the core issue. There is still a need for an effective method for determining an optimal range of shaft lengths and club head weights for each individual golfer that would maintain his tempo and/or ball striking accuracy within an acceptable range.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention starts with the premise that having a reliable and consistent “repeating” swing is a meaningful goal for most golfers. Repeatability and consistency has been identified with consistent tempo and/or ball striking accuracy. The present invention teaches that having thirteen different shaft lengths/club head weights is not necessarily a problem. Rather, it is the fact that length/weight combinations outside an optimal range adversely affect tempo and/or ball striking accuracy, which introduces a significant source of inconsistency in performance. It also teaches that too narrow a range of lengths/weights (e.g. only one, or a predetermined few) may needlessly constrain a golfer&#39;s potential. Determining a range of length/weight combinations within which a golfer is able to keep his tempo and/or ball striking accuracy within an acceptable tolerance is the solution. Within this range of length/weight combinations, other golf club parameters (e.g. loft, shaft flex, etc.) can be varied to create a set of golf clubs that has been customized to span a golfer&#39;s desired (and feasible) set of distances and trajectories.  
           [0007]    In one aspect of the invention, a golfer would swing clubs with a variety of length/weight combinations one or more times. Tempo and/or ball striking accuracy would be measured for each swing and a distribution of tempo and/or ball striking accuracy as a function of length/weight would be developed. In another aspect of the invention golfer performance data at particular length/weight combinations would be used as input to mathematical models that could then be used to project performance for other length/weight combinations.  
           [0008]    While a preferred embodiment of this invention deals with a full set of clubs, alternative embodiments deal with sub-sets including but not limited to: woods alone, irons alone, wedges alone, or any set of one or more clubs wherein it is desired to design the club(s) to maintain a consistent tempo and/or ball striking ability.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0009]    The invention is described with reference to the several figures of the drawing, in which:  
         [0010]    [0010]FIG. 1 is a representative three-dimensional graph of tempo as a function of both length and weight according to one embodiment of the invention;  
         [0011]    [0011]FIG. 2 is a representative two-dimensional graph of tempo as a function of length, holding weight constant, and a corresponding confidence interval according to one embodiment of the invention;  
         [0012]    [0012]FIG. 3 is a representative two-dimensional graph of tempo as a function of weight, holding length constant, and a corresponding confidence interval according to one embodiment of the invention; and  
         [0013]    [0013]FIG. 4 illustrates a piece of impact tape showing a dispersion of hit imprints for a golf club with a representative length/weight combination according to one embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    The present invention starts with the premise that having a reliable and consistent “repeating” swing is a meaningful goal for most golfers. Repeatability and consistency has been identified with consistent tempo and/or ball striking accuracy. The present invention teaches that having thirteen different shaft lengths/club head weights is not necessarily a problem. Rather, it is the fact that length/weight combinations outside an optimal range adversely affect tempo and/or ball striking accuracy, which introduces a significant source of inconsistency in performance. It also teaches that too narrow a range of lengths/weights (e.g. only one, or a predetermined few) may needlessly constrain a golfer&#39;s potential. Determining a range of length/weight combinations within which a golfer is able to keep his tempo and/or ball striking accuracy within an acceptable tolerance is the solution. Within this range of length/weight combinations, other golf club parameters (e.g. loft, shaft flex, etc.) can be varied to create a set of golf clubs that has been customized to span a golfer&#39;s desired (and feasible) set of distances and trajectories.  
         [0015]    It has been discovered that the optimal range of length/weights is often within a narrower range than that utilized by traditional golf clubs. This implies that the optimal range of other golf club parameters, for instance loft, needs to be wider than that utilized by traditional clubs.  
         [0016]    It has also been discovered that some golfers (e.g. women, junior or senior golfers who have limited swing speed) would increase ball flight distance while maintaining tempo and/or ball striking accuracy by increasing club head weights beyond those traditionally provided for them.  
         [0017]    Choosing weights for each length within the optimal range could be accomplished by looking for a set of weights that match swing weight (or other balancing parameters) while maintaining tempo within the desirable range. Note that the shafts could also have additional balancing weights near the grip as discussed further in U.S. patent application Ser. No. 09/295,913 entitled “System for Optimization of Golf Clubs.” 
         [0018]    Tempo is usually identified with swing speed. One useful measure is the speed of the golfer&#39;s hands (which for purposes of standardization, could be measured at the left middle knuckle for a right-handed golfer, or at some other convenient reference point) observed at the point of impact of the golf club and golf ball. Several devices for measuring club head speed already exist and these can be easily modified to measure hand speed (e.g. by placing an indicator on the left middle knuckle that is picked up by a sensor at the point of impact) (see, for example, U.S. Pat. No. 4,059,270 to Sayers). Tempo could also be measured with a stopwatch, by analyzing videotape of a swing, or even by how fast or slow the swing felt to the golfer.  
         [0019]    Ball striking accuracy can be measured using impact tape as the dispersion of hits on the face of a club head, by analyzing golf club and ball impacts from video tape or by subjectively analyzing how the impact felt to the golfer (i.e. Did it feel solid?, Was it a toe or heel hit?, etc. . . . ).  
         [0020]    Referring now to the figures of the drawing, the figures constitute a part of this specification and illustrate exemplary embodiments to the invention. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention.  
         [0021]    [0021]FIG. 1 is a representative three-dimensional graph of tempo as a function of both length and weight according to one embodiment of the invention. In general, tempo decreases as length and weight of a golf club increase. The interplay of these characteristics varies among golfers, and each golfer will have an optimal range of characteristics that produces a desired tempo, accuracy and consistency.  
         [0022]    [0022]FIG. 2 is a representative two-dimensional graph of tempo as a function of length, holding weight constant. FIG. 3 is a representative two-dimensional graph of tempo as a function of weight, holding length constant. The human body is such that at very short and very long shaft lengths tempo and/or ball striking accuracy will drop off dramatically. These very short or very long lengths are depicted in the left and right segments of FIG. 2 and can be removed from consideration. Similarly, very light or very heavy weights which are depicted in the left and right segments of FIG. 3 can be removed from consideration. An appropriate statistical measure of variation such as standard deviation can be used to sort through the remaining length/weight combinations. Combinations with too much variation can be discarded. The level of variation can be determined subjectively or objectively (e.g. using a 95% confidence interval). The solid graph lines  20 ,  30  in FIGS. 2 and 3 represent a golfer with perfect precision in his golf swing while the dotted lines show representative lower  22 ,  32  and upper  24 ,  34  confidence intervals to indicate the variability in tempos on the respective graphs. In general, as tempo increases, the variation in tempo also increases thereby increasing the confidence interval. Similarly, as length and weight increase, variation in tempo also increases again increasing the confidence interval. The graphs show a representative interaction between these variables. A user may choose a desired tempo that is less than the maximum in order to take advantage of a smaller confidence interval and thus a smaller probability of tempo variation which translates into a more consistent swing.  
         [0023]    Ball striking accuracy also can be used as a filter for choosing length/weight combinations. FIG. 4 illustrates a piece of impact tape  40  showing a dispersion of hit imprints  42  for a golf club with a representative length/weight combination according to one embodiment of the invention.  
         [0024]    What remains after this culling process is a set of length/weight combinations that produces an acceptable range of tempos and/or ball striking accuracy for the individual golfer. Thus for example, the golfer may have experimented with shafts as long as 50 inches and as short as 32 inches but only accepted those in the range between 44 and 39 inches. Similarly, he might have experimented with weighs of 150 to 450 grams rejecting all of those outside of the range between 205 and 350 grams.  
         [0025]    Now the task is to build a set of 13 clubs (or any sub-set thereof) that spans a feasible set of distances for the particular golfer. This process could be facilitated by the use of a table which for standard shaft types tells how far (carry or carry plus roll) a typical golf ball will travel given a shaft length, club head weight and club head loft. (Other parameters such as club head shape, shaft flex and kick point could also be factored into the table). A strong golfer will be able to cover a greater range of distances than a weaker golfer. Here the golfer must be realistic. There may be no combination length/weight/loft that hits his drive as far as he wishes, given his tempo. It is convenient (but not necessary) to determine the longest feasible distance a golfer can consistently achieve (typically with a driver) and then design the 12 remaining clubs to achieve shorter targeted distances. For example, a reasonably proficient golfer may be able to hit his driver 250 yards and might specify 225, 200, 187.5, 175, 162.5, 150, 137.5, 125, 112.5, 100, 87.5, and 75 yards as his targeted distances. Lengths and weights from the optimal set together with loft angles can be chosen to achieve the desired targeted distances. Other characteristics can also be modified to achieve desired targeted distances as disclosed in U.S. patent application Ser. No. 09/248,515 entitled “Golf Club and Method of Design.” There may be different length/weight/loft angle combinations that achieve the same distance. In this case it will be desirable to seek a set of clubs that also provide a consistent feel. This can be accomplished by choosing among the desirable length/weight/loft angle combinations those that are balanced for swing weight, moment of inertia or other balance parameters.  
         [0026]    Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.