A Custom Golf Club Fitting System & Golf Shaft Mechanics

Custom golf club fitting has been around for many years. Custom golf club fitting in the past has dealt with selecting club length, club lie and grip size by specific measurements. The most important component, the stiffness of the Golf Shaft, was selected by trial and error, or more recently by club head speed. Even though players may have the same club head speed, they don't have the same club release or swing timing. "FitChip" which employs a computer chip and accelerometer records the acceleration pattern from which it can derive the shaft loading pattern from which we can identify club release, ball impact, and other critical swing timing parameters. Using this information during the computer analysis phase, FitChip identifies the exact cycle per minute frequency for the golf shaft, thus insuring that it will return the shaft to straight and  square at ball impact. This insures the greatest combination of  distance and accuracy. This is the only system that considers where the shaft is at impact. It is important to have that shaft back to straight where you will realize your best accuracy and clubhead speed.

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What the Custom Clubmaker Should Know About Golf Shaft Mechanics

Most people in the industry consider the golf shaft to be the engine that drives the club head. This is true, one must have the correct shaft to achieve maximum performance. It is known the golf shaft "kick" can add 10% to 15% more club head speed over and above what a player can achieve using a rigid golf shaft. The most important part of achieving this peak performance is fitting the golf club, or golf shaft, or engine, for its peak performance under its conditions of operation. The conditions of operation for the golf shaft is the individual players swing. Since the golf shaft is a spring, that spring must be tuned to meet the operational requirements of the players swing or load and unload timing. You can load the spring by just pulling back on it, at whatever rate you are capable of applying the load. The shaft is loaded in the golf swing by accelerating the club in the down swing. Like a spring we pull back or load, it will not spring back or unload until we release it or let it go. When it is released it is driven by a spring action or timing we call natural frequency. The natural frequency of a shaft, or total club in this case, is the most accurate measurement to identify the correct golf club/shaft frequency for any player. The unloading, or load release that takes place during the swing, follows a quarter sine wave back to the point where the the golf shaft is straight, or the load is back to zero, and the spring reaches its highest speed. As long as this load release, in the form of a sine wave is not exceeded by the player reloading the shaft, it will continue to release on the sine wave described by the natural frequency of the club. It is the custom club makers job then to select the proper golf club fitting process to achieve the timing to get the golf shaft back to straight and square at ball impact. The golf club fitting process to achieve this proper golf shaft is not simple. In the past the best way to make this selection was by trial and error. There are three things wrong with the trial and error system:

1. Maintaining a good swing for the time it takes to try all the shaft possibilities.
2. The cost of buying all of the clubs one wants to test.
3. There is a limited range of shaft stiffnesses available off the shelf for testing (we find that only 40% of the players can be fit within the range of off the shelf shafts).

FitChip solves this problem  identifying the swing timing  interval between the shaft release point and ball impact, and the relationship of that time interval to the natural frequency of the golf club. As pictured below the critical golf shaft selection time or kick initiation, with a driver, occurs in a .05 second interval during the down swing. This interval represents the difference between selecting a 170 CPM (LLLL) golf shaft and a 320 CPM (XXXX) golf shaft for the player. Since the FitChip takes 25 readings during this interval, it is by far the most accurate method available for properly fitting golf clubs and shaft frequencies.

One must understand that the amount of load placed on the golf shaft is not important, it is only the time interval that makes this first basic frequency selection. Some people do not grasp this fact but it can be easily proved by putting a shaft in a frequency meter and deflecting it several different amounts, the frequency will always remain the same independent of how much you deflect or load it. I call this a basic frequency because there must be a correction made to this frequency to arrive at the final golf club fitting and golf shaft selection. The correction is based on the centrifugal force acting on the club head. If the golf shaft is flexed or curved during the down swing the centrifugal force is trying to straighten the golf shaft which reduces the amount of spring action needed to bring the golf shaft back to straight and square. If there was no centrifugal force the basic frequency would be the answer but since we are dealing with a golf swing that generates club head speed and as a result centrifugal force, we must reduce the necessary spring action or frequency as a function of the magnitude of the centrifugal force. Since club head speed is the precursor to centrifugal force the correction relationship can be derived as a direct function of club head speed. Therefore the relationship will describe the amount the frequency is to be reduced as the club head speed gets greater. This part of the golf shaft mechanics goes against the general shaft selection theory of the industry, because when two players have the same time interval between release and ball impact the one with the higher club head speed gets a softer golf shaft then the player with the lower club head speed. This is because the player with the higher club head speed is getting more help from centrifugal force and needs less spring action to bring the golf shaft back to straight. Having made this correction you now have the frequency for the club that matches the players swing timing or swing frequency through the highly accurate golf club fitting process FitChip. As an example of a poor golf club fitting process, the following pictures were taken from a video of a long drive competitor. This individual generated a club head speed of 134 mph. Of course, the golf industry would give this individual as stiff a golf shaft as possible. However the industry does not consider swing timing, but only club head speed.

In the first photo the club is at the top of swing, just reversing direction, with a slight load. The photographs have been marked with yellow to indicate the golf shaft straight position and head position with respect to the straight golf shaft. In the second photo the club is loading and showing significant deformation. In the third photo the golf shaft is still loaded but the slightly less deformation indicates unloading has begun.

In the fourth photo the golf shaft is back to essentially straight indicating the golf shaft has unloaded to the point where it has released its stored spring energy. This should occur at impact for the players best performance. The golf shaft is slightly ahead of the shaft as should be expected because of the Centrifugal Force affect. Photograph five shows the head substantially ahead of the golf shaft and much more then can be justified with the Centrifugal Force affect. Photograph six is even more dramatic when it shows the golf shaft with less forward deflection than in photo five indicating that the golf shaft is starting to recoil and losing speed with respect to the individuals input speed prior to impact. Such a dramatic golf shaft mismatch could cause a loss of 10% to 20% of the individuals potential club head speed. With the very early release of this golf shaft, the proper golf club fitting system would call for a much softer golf shaft for this individual. You can achieve this first mode frequency in any style or configuration of golf shaft.

Many people get concerned about kick points in the golf shaft. If the golf club fitting properly done for the players swing the high kick point golf shaft will provide the best club head speed because it will give more shaft deflection for a given frequency. The greater deflection results in greater club head speed when the golf shaft is back to straight. If the golf club fitting get the golf shaft back to straight at impact the launch angle is determined by the face angle irregardless of the kick point. Low kick points would be for those players that can not be fitted because of a wide variation of swing timing from swing to swing. The low kick point will cut down on the dispersion caused by golf shaft flex timing since there will be less flex or head movement. Golf shaft torque is another part of the golf shaft mechanics that most club makers do not fully understand. Steel golf shafts that have always been considered as having low torque values were never considered as feeling bad but many club makers feel that when a graphite golf shaft has the low torque value it has a bad feel. I believe feel is in the flex and timing of the shaft, not in its torque value. The greatest affect of golf shaft torque on club performance occurs when the player hits the ball off the sweet spot, resulting in greater dispersion. In this case every player can benefit from a low torque value. The deflection of the golf shaft in torque plays very small roll in squaring up the head at impact because this deflection is very small. Why is this deflection small? The golf shafts torque value is designed primarily to provide the strength needed to resist breakage of the golf shaft during toe impacts. By calculating the acceleration of the club head weight during the swing and the ball acceleration off the club face the torque from the toe impact is 8.75 times greater then the torque on the golf shaft during the swing. So, if you got 3 degrees on toe impact you would only get .34 degrees during the swing. Spine alignment is another aspect of golf shaft mechanics. There are two different shaft conditions that cause what has come to be called a golf shaft spine. There is also the possibility of the combination of the two types:

1. A golf shaft with a slight bow in it. The bow can be determined by rolling the golf shaft on a flat surface or on a spine alignment tool the bow will end up with the tip lower then the butt.
2. A golf shaft with a hard side or more material on one side then the other such as a seam or over lap of material might produce. The hard side will always be on top in a spine alignment tool.

If you align the Golf shaft in the club so that the golf shaft bows away from the target or the hard side of the shaft is toward the target, when the golf shaft flexes during the swing it will be stable and flex on a straight back path. If the golf shaft flexes back on a straight or stable path it will return to the ball on that path. When the golf shaft is not aligned as suggested it will flex to the inside or outside of the straight back or stable line causing the golf shaft to return to the ball off line.  Lotus Golf uses all of these factors in their golf club fitting process with "FitChip".