This topic is always interesting to me, because while science will say one thing, a player may say something else.
Pure logic tells us that once the ball leaves the clubface, it’s over and nothing matters… and this rightfully would appear to be the case, because how can the ball be effected by what is happening at P4 or into finish?
But I suspect the answer does not lie in the CSI data collected by high speed camera’s, trackman or other scientific measuring devices… but instead lies in the more esoteric realm of probability.
In other words, the probability of proper golf shots being struck increases substantially when __________ this or _________ that occurs post impact.
I know from posting before on the subject of impacts elsewhere that it is for many frequently very much counter intuitive. The comparison with impacts involving moving trains, trucks or cars is just adding more confusion.
The crucial element is the extremely short time scale involved and also the simplicity of the objects colliding. This is the case for impact of a clubhead and golf ball. Complex items are deforming in very complex ways and mostly inelastic.
The impact forces occurring between clubhead and golf ball are extremely large, several thousand pounds. How can a few pounds due to a pre stressed club shaft compete ?
Maybe they have a moment of fun all by themselves. But the ball is still on the club face when that moment is over.
The speed of sound in steel is approx 5960 m/s. I assume that figure is applicable for the speed of the impact shock as well. So as long as you’re using a steel shaft that is shorter than about 93.7 inches the shock will reach your hands before impact is over. If we assume a driver with about half this lengt, your hands will be directly engaged in impact for about half the impact interval. You may not feel impact until it’s over, but you will put work in there nevertheless. I don’t know how fast a shock travels in the bone structure from the hands to the shoulders. Perhaps the ball is still on the clubface when that happens?
It takes only about 4 microseconds before the shock has traveled 1 inch up the shaft. So the first inch of the shaft will basically be part of impact for 99% of the impact interval. This first inch is moving mass as well. How fast it moves has an influence of the dynamic weight that gets into the ball. The next inch will have impact contact for approx 98% of the interval, the third for approx 97% and so on.We can continue all the way up to the hands, and the conclusion will be that the mass speed in the shaft makes a difference. So for that reason alone, hands speed at impact makes a difference.
And the hands are heavy! And forearms, and perhaps upper arms adds to the equation too.
The usual analysis of this topic deals with shaft flexing and bending, and the torque that the hands may apply to the shaft. But there’s more than shaft bending that goes into this. There is an axial force that runs through the shaft - from merely pulling the shaft through impact. In a proper golf stroke, this force doesn’t point towards the swing center. That is quitting and loss of lag pressure. No, the left arm is attached to the left shoulder, and the left shoulder is pulling from the left side of the swing center. So the pull from the left side is not only a centripetal force but also a radial force that pulls the club head forward. If, or say when, the club slows down at impact, the hands keeps going and keeps pulling the club forward (and not just inward) and this forward pull will be effective for at least half of the contact interval.
Does any of this make a difference in practice? I am convinced that it does. Freewheeling through teh ball gets you a long way if you hit it pure. But more weight and more force through impact equals more distance and more back spin. And also much better result on the “odd slightly missed the sweetspot” stroke.
The impact forces are so large that if we can simply show that the force exerted possibly by the shaft to be very much smaller in comparison than we can safely ignore it. Simply clamp a driver to a table from the grip end. Attach an object weighing a few pounds to the hosel and notice the substantial deflection occurring even for such a small weight.
Even assuming a bit of centrifugal stiffening of the shaft during a down swing and considering the actual small deflection of the shaft in the down swing and more specifically at impact, the shaft exerted force can safely be considered to be very small and consequently negligible in comparison to the huge impact forces.
A robot golfer and a human golfer don’t operate the same way due to the fairly large human reaction time with respect to the duration of the down swing.
Planning to do certain things past impact influences what occurs before and during impact.
I would estimate that when I am swinging my best, I can feel 5 pounds of pre stress on the clubshaft through impact. I base this off taking practice swings without hitting a ball or the ground, and what I feel in my hands at or near lowpoint and beyond. Taking that same sensation and pushing down on a digital postage scale is how I come to that number.
The key here is that this pressure in the hands is absolutely significant to me as a player. It is this pressure that tells me exactly where the clubface is spacially in 3 dimensions… and the only way I can feel this is by firing stored clubshaft angles from P3 actively with the hands.
So again, whether the ball actually is effected significantly by pure impact physics or not… I feel quite confident that by holding shaft flex I am greatly increasing the probability of hitting another golf ball where I am aiming with both shot shape and trajectory in mind.
I can walk down a driving range and find a strong slashing hacker with a horrible swing that can on rare occasion connect into a perfect drive, maybe one out of 20 swings. Over accelerating the club will lose shaft flex before impact, therefore reducing the probability of that the player is going to be able to guess exactly how the club and shaft are going to react with the ball.
The long ball champions are not necessarily holding shaft flex. Pure velocity will win the physics game for long ball knocker… over lower speeds that bring in an accelerating clubhead, but they will not likely play better golf… and the more the golf course requires precision shot making, the less probable an over accelerator will find success.
I don’t think Homer’s work distinguished between the two… as far as impact physics. He did talk about a hitter’s objective of holding shaft flex or bringing a pre stressed clubshaft into impact… but I think he was in error that in his subjective opinion, that to do … or not to do… seemed equally capable.
There is a difference… however small, and I hope that at some point the science of impact physics could explain this to be in harmony with what good players or hitters and swingers experience. If science doesn’t… then it is falling short of what it should be doing accurately… and needs further recycling of the scientific method. It’s important to remember that golf is a game of extreme precision… yet somehow cultivated in a sensation of reckless abandonment. I think this is what Knudson described as “giving up control to gain control”.
I do want to say that I appreciate your posts here, as I know they are always interesting, and open deep and introspective discussions. It might be nice to have your own thread here dedicated to your findings that can be discussed, debated and so forth… I know at times I try to dig up one of your charts or diagrams and can’t remember which thread it was on or so forth. I particularly related to the one about flat vs upright lie angles.
Anyone thinking this is a good idea… please put forth your vote of approval… as it would be convenient to have access to the various scientific findings in a more user friendly way than having to search through old posts on forgotten threads.
I know there are a lot of TGM defectors here at ABS, that enjoy this kind of banter and for good reason.
A pulse only needs to go to and fro if you’re looking for a rubberband effect, where the shaft is first stretched and then conttracts like a rubber band while the club is still in contact with the ball. But that’s not what I’m talking about.
The extension phase is over when the shock has reached the hands. By then, the club shaft is carrying the sudden increase in axial force all the way up to the hands and the hands are in it.
Tests with hinging shafts and whippy shafts - shafts that doesn’t kick - have been undertaken , and have basically shown that shaft kick doesn’t influence resistance aganinst impact slowdown, although it can influence club head speed somehow. But these kickless shafts still carry the axial force. So these tests are only relevant to examine the role of shaft bending and unbending. It would require a club that disconnected the club head from the shaft at start of impact to empirically investigate what I’m talking about here. I have had shaft breakage during impact a couple of times. The ball flies lower and shorter. The distance has been reduced with roughly 1/4-1/3 of normal distance. If it was a “private moment” the ball should have it’s normal distance and trajectory. But it doesn,t.
I really do appreciate your compliments very much as I have rarely seen someone writing about golf with such intimate knowledge and eloquence and moreover showing a true appreciation of the typical paradoxical character of golf but I do not like the idea of having my special place on this forum. Usually my posts are in threads I started myself so things are already kind of organized not too badly. I only get sporadically interested in posting nowadays. I had lots of fun years ago posting on Brian Manzella’s forum where I had many battles to fight typically one against all but seeing the results I consider it to been time well spent.
The question that I always come back to in this discussion is if we can do nothing at the moment of impact, then when can you do something? Where and when is the force created to apply to the ball? I have my own workable ideas, but from a theoretical perspective, when and where does it happen? I agree that there is a divide between theory and what works, but understanding or listening to this stuff is helpful. Btw, I do think a mandrin thread would be helpful so that’s got my vote- can foreigners vote?
Another question that I have is about ball compression. The club first makes contact with the ball at a point, but then it makes contact with more of it surrounding the area of initial impact. The club is moving forward as the ball is ‘going backwards’ in a way, and then the ball goes. I do believe that there’s a deceleration of the club head as a result of impact, but the compressing of the ball enables a continuation of the club’s journey which I think speaks to and adds merit to some of Lag’s thinking. Combine that with the flexing of the shaft and clearly you can keep moving as you were while the clubhead momentarily slows down to hang with the ball. I guess my point is that impact isn’t just one moment on one point of the ball and could at least conceivably be a non interruption on the journey of the club in a similar way to a bug not slowing down your car when it squashes on your grill.
I thought that the point of delivering a flexed shaft into and beyond impact more to do with the shaft itself releasing rather the actual transfer of energy. The later shaft releases the better in my mind, even if it is during the .00004 seconds, which to the ball must feel like a very long period of time.
Before you can all entangled in your axial theory trying to reinvent the wheel I should perhaps bring you up to date.
Over 40 years ago a British group of scientists, headed by Alastair Cochran did, between many other things, an experiment with a specially made 2-wood with a hinge in the shaft just above the head. At impact the hinge can give way completely.
From 'Search for the Perfect Swing” by Alastair Cochran and John Stobbs –
“The experiment proved to the satisfaction of the scientists, the point which theory had strongly suggested: during impact the clubhead acts as though quite disconnected from the player.”
Some other comments -
“An important consequence of the inability of the player to exert any positive influence on the ball during impact, is this: the only dynamic factor that mattes in producing distance is clubhead speed. A given clubhead making square contact with the ball at 100 miles per hour will send it the same distance whether it is accelerating , slowing down, or moving at constant speed.”
'… But what is certainly not true is that acceleration of the clubhead into impact will produce any effect whatsoever on the ball beyond that produced by pure speed at which it is travelling; and further more, in any full shot, acceleration through the ball is a sure sign of wasted effort which could have been used to produce greater speed at impact if it had been applied earlier.”
During the down swing kinetic energy is imparted to the clubhead due the effort employed by the golfer. When the clubhead collides with the ball one can consider the head to be almost a free body and there is sharing of this energy/momentum between ball and clubhead.
The force acting on the ball is almost totally due to the very large impact force generated, reaching several thousand pounds. Hence this very large force exerted on the ball sends it on its way, whereas an equal and opposite force is exerted onto the clubhead slowing it down a fair percentage.
Hence a golfer does not really apply any force on the ball. He does generates adequate speed for the clubhead during the downswing and the collision generated forces, between clubhead and ball, take care of the rest.
Another way to look at it. Consider the clubhead to be a solid mass. During impact the ball behaves like a spring being compressed and when maximum compression is reached this is subsequently released quickly and the ball literally jumps of the face of the clubhead.
Is it just me or does this quote contradict itself?
The last discussion we had where I was advocating for the value of pre impact acceleration your take on it was that it was a waste of time. I disagreed with that view, but it seems now, at least according to the second part of this quote, that you’re now advocating for that very thing.
In my view, the speed/strength/force you bring into impact is the key because of the reasons you’ve stated. Have you changed your mind on this issue from a scientific perspective?
I find that some of your explanations are incomplete in terms of the depth of questions being asked. That’s not to say that your thoughts aren’t helpful, it’s just that I still find that I’m wondering after reading your replies. Maybe I still wonder about the supposedly negligible effects that are brushed aside as irrelevant. If science has all the answers, then there should be no more questions. Some of the experiments done by scientists don’t specify how the club moves or how it’s being powered. From your previous posts, my conclusion is that you see a free moving clubhead, but that’s not really how the best strikers hit the ball. Speed isn’t worth a whole lot if it’s not supported- look at Tiger for example. I do think there’s a gap between scientific theory and practical knowledge of how to strike the ball well, and I think that gap can only be filled from the side of the person that knows how to do it. Ask any accomplished player and they’ll tell you that they can manipulate the club at points that theory supposedly doesn’t allow.
Again, I definitely find these discussions valuable and I appreciate your thinking, but I do still end up wondering.
Cheers,
BOM
