Physics of a club shaft

Forgive the oddball thread here. In trying to learn more about what the right shaft for me is a number of things have struck me and it raised some questions.

Related good write up:
http://www.golfshaftreviews.info/understand-golf-shaft-stiffness-ratings/

Shafts are fundamentally sold by "senior", "regular", "stiff" etc. LARSX by the above explanation. Project X is more straight up about it and puts numbers to it related to frequency. You also have the EI graphs which have an impact on how the shaft bends which in turn affects launch angle and spin. As of today, its seems that fitting a shaft to you is picking the right frequency and EI curve to match or complement your swing. To me, there is a factor missing.

Imagine that you take a golf club and mount it vertically in a vice so that the grip cannot move. If you push the club head to the side with a force, the shape of the shaft would be determined by the EI curve. When you suddenly remove the force, the club head would oscillate back and forth at a frequency related to its stiffness. When we pick a stiffness, we effectively are trying to get a shaft that does half of a full oscillation (load to one side and return to center) in the amount of time it takes for our swing to go from the full lag position to ball contact.

To me, that only seems like 2/3 of the picture. The distance of deflection when the force is applied (or amplitude) isn't explicitly defined by this. This amplitude, when combined with the frequency would define the speed of the club at center while it was oscillating. The more deflection a club gets at a given frequency, the faster it is going to be moving as it unloads and we all know that faster is better. A club with the right frequency for your swing is going to hit the ball further with greater amplitude deflection.

Do shaft manufacturers watch this? Am I just unaware of how things are done?

I'm a total newbie so I expect that there are simple answers to this but when I read it online it seems like engineering vodoo. What am I missing?

Following Along for this because I too am a total novice in the science of shafts. When I went for my fitting he did that test on a horizontal vice thing, and measured the frequency.. my current shaft is the hzrdus black stiff and he put me in a kuro kage x stiff but to similar frequency but a little less stout maybe.. but yes interested in what those more knowledgeable have to say

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I don't quite get what you're asking here. Frequency is used when determining how stiff the shaft is at each point by clamping, but that's a measurement technique, and doesn't translate to how the shaft behaves during the swing. The swing defines the rate of loading and unloading of the shaft, not the properties of the shaft.

I agree with mpeterson. What you are talking about is going to be determined by a combination of your swing and the shaft flex. I think fitting is the attempt to maximize the effect of shaft bend and release for your particular swing.

mpeterson said:

I don't quite get what you're asking here. Frequency is used when determining how stiff the shaft is at each point by clamping, but that's a measurement technique, and doesn't translate to how the shaft behaves during the swing. The swing defines the rate of loading and unloading of the shaft, not the properties of the shaft.

Click to expand...

If you clamp down on the grip as tight as you can, the part out of your hands (shaft and club) will have a natural frequency. The stiffer the shaft, the faster it will oscillate. The golf world uses the term stiffness to roughly define this. From the time you start loading the shaft during the swing to when you make contact with the ball is a time period, or effectively a frequency also as the two are directly proportional.

I always assumed that when you got fit for a golf club, a big part of it was that you were matching your swing frequency with the club frequency. Am I wrong there?

The bigger observation is that I think that the amplitude of oscillation is also a variable somewhat independent of natural frequency. The bigger the amplitude, the further you will hit the ball on a properly timed strike.
Am I wrong there?
If not, do club shaft manufacturers evaluate this? Is it just part of the EI curve that I don't understand?

The frequency that we measure is the first natural mode of frequency of the shaft, in a rigid clamp. On a straight tube this is directly proportional to the EI. For a tapering tube, its a little more complicated, but the frequency is still related to EI, but the butt end (stiffer end) dominates. Frequency is simply a faster way to measure the stiffness of the shaft.

I vaguely followed what's been written so far. What do you want your ball to do? Higher? Lower? Less dispersion? More/less roll?

I'd love to help, but you have to help me help you first. Current setup and what you want the ball to do differently would be helpful. I don't really care what my club in a vice will do if I "twang" it. I care about what my golf ball does when it leaves the clubface.

Sorry if being overly blunt. I want to help but I'm not capable of building a Word Document that will explain it.

SmiterOfPv1x said:

I vaguely followed what's been written so far. What do you want your ball to do? Higher? Lower? Less dispersion? More/less roll?

I'd love to help, but you have to help me help you first. Current setup and what you want the ball to do differently would be helpful. I don't really care what my club in a vice will do if I "twang" it. I care about what my golf ball does when it leaves the clubface.

Sorry if being overly blunt. I want to help but I'm not capable of building a Word Document that will explain it.

Click to expand...

I want the ball to go further at the same "stiffness" (or what I called oscillation frequency). I'm trying to see if some shafts will load up and unload more creating a higher club face velocity at the same effective stiffness.