During impact, the ball is 1) "deformed/flattened" (due to inertia, Newton's First Law of Motion, and its elasticity) and 2) "carried" briefly on the clubface (due to acceleration, Newton's Second Law of Motion) and then 3) "reformed and bounced off" (due to force and counterforce, Newton's Third Law of Motion).
Let’s slow the process way way down. Upon collision, the whole swing unit, including the clubhead, loses part of its momentum to the ball and decelerates (conservation of momentum). One portion of that energy is stored in the ball (which will be released upon reformation) as being deformed on the clubface and absorbed by the clubshaft and body, which all dampen the impact and give the golfer the sensation of a soft resistance on the grip. Other portion contributes to its acquired speed as being carried on the clubface by the clubhead before taking off (separation). Additional ball speed is then gained when the stored elastic energy is released upon the reformation of the ball (depending on the Coefficient Of Restitution of the ball) and bounces it off the clubface by pushing back the clubhead (like pushing yourself away from a wall moving in the same direction) causing its further deceleration. In short, the ball gets accelerated twice (being moved and carried and bouncing off) at the expense of the clubhead being decelerated twice (deformation and reformation of the ball). In contrast, a clay, which has a COR of 0, only gets accelerated once (without bounce) during the same process and launches at the same speed as the clubhead at separation.
Let say the clubhead's sweet-spot approaches the ball in-line (square to the clubhead path) at 100 mph. It's decelerated to 80 mph, the speed the ball picking up while being carried. So both the clubhead and ball travel at 80 mph at this stage. Assume the COR of the ball is 0.8, which means the ball is supposed to bounce squarely off an “un-decelerable” surface at 80 mph upon reformation while being initially deformed at 100 mph. Depending on how “strong” the clubhead is in resisting against the second deceleration by ball reformation (bounce) and the angle of impact (the more square 3-dimentionally, the more efficient bounce and deceleration), let say it happens to bounce off at 70 mph (which is ~88% of COR) and the clubhead gets pushed (backward) and slowed down to maybe 70 mph (needs to be measured to be sure) at separation. In summary, the speed of the clubhead goes from 100 to 80 and ends up at 70 mph at separation, while the ball gets accelerated from 0 to 80 to 150 mph at separation.
Note that the numbers used above are arbitrary and just for the explanation of the event of impact. The real numbers needs to be measured precisely under controlled experimental condition. As mentioned above, there are a lots of factors needs to be considered during the event. I'm not sure if the ball simply "acquires only 70 % of the Clubhead approach speed and 100 % of the Clubhead separation speed" as Homer described in the book.
There are, however, several things to be sure: with a given ball,
1. Higher approaching clubhead speed + squarer impact (sustained line of deformation) = more deformation (stored ball energy) and carrying period and carrying speed of the ball.
2. "Heavier" clubhead (pushing the closed door vs. pushing the door closed) + more stressed shaft (both relating to "LAG") + sustained acceleration (full release/sustained LAG beyond impact) + square impact + longer carrying period (including horizontal hinge) = better against secondary deceleration (pushing back) = more efficient bounce (preserving and releasing the stored ball energy).
It seems that the relatively softer and more elastic the ball, the easier for it to be deformed with better stability during carry.
Thanks for your great post, JJ. Very little is written about this fleeting Moment of Truth we call Impact. I found two of your points especially interesting:
1. "Depending on how “strong” the clubhead is in resisting against the second deceleration by ball reformation (bounce) and the angle of impact (the more square 3-dimentionally, the more efficient bounce and deceleration)..."
I have not heard anyone make these points since Homer Kelley in his 1982 GSEM Class. Producing this Three-Dimensional Impact -- especially the Downward element -- brings a more Vertical Clubface into Impact. The Ball tends to separate at the same Angle and with greater Compression. He maintained that this Impact, in turn, was one of the great benefits of the Right Forearm Takeaway -- the "Pick-up" as he liked to describe it. Such a Start Up produces a "more perfect circle" and a far better Downward motion through Impact than the flatter path of the Clubface (both in Start Up and into Impact) produced by the Shoulder Turn Takeaway. This strongly Downward Impact eliminates unintended Clubface Layback during Impact -- which is what happens when the Clubface comes "scooting in along the ground behind the Ball." Thus, it is directly responsible for a minimum of, in Homer's words, "Clubface Wobble," or as you said, "how 'strong' the Clubhead is in resisting..." the violent forces of the Impact Collision.
2. "It seems that the relatively softer and more elastic the ball, the easier for it to be deformed with better stability during carry."
I have three questions regarding your conclusions about the all important Ball characteristic of Resilience. First, does "relatively softer and more elastic" mean a higher or lower Compression Ball?
Second, does "easier...to be deformed with greater stability during carry" necessarily mean a higher COR, i.e., a 'better Bounce?'
Third, given your conclusions, is there an 'ideal Compression' Ball for all golfers?
Please explain "to do this the ball must be travelling 150 mph"
I have no idea what this line means when Homer is talking about seperation speed of 70% of 100 mph
thanks
Homer is saying that a golf ball will separate itself from the clubface at a speed that is approximately 70% of a high approach speed. However, that is separation speed, which means faster than it was already travelling.
So, assume a clubhead approaching at 100 mph. It impacts the ball, which causes the clubhead to slow to about 80 mph. For a short time, the ball travels along "stuck" to a clubface travelling 80 mph. The ball then "springs" off the clubface at a speed 70 mph faster than it was travelling while it was "stuck" to the clubface. 80 mph + 70 mph = 150 mph separation speed.
Correct, Bobbywayne. The Ball picks up 70 percent of Clubhead Approach Speed and 100 percent of Clubhead Separation Speed. Impact causes the Clubhead to slow considerably, and without active resistance to this deceleration, the Clubhead will slow even more. That is why it is so important -- Hitter or Swinger -- to keep driving through Impact!
Topic:Right Forearm Alignments
Originally posted by Ringer
That may be the impression you get Yoda, but in fact it's rotational. The shoulders rotate to generate the uppercut. This same rotation occurs in the golf swing on an angled plane. This makes both motions similar but with slightly varying extensions and alignments of the arm. The behavior of the upper body is however similar. 2-H and 7-13 shows us that the shoulders have "crucial On Plane Functions".
My problem with this uppercut image is not that Clubhead Force and Motion is Rotational and On Plane. This is exactly correct per 1-L #9 and #11. My problem is that an uppercut punch -- no matter how explained -- still involves an Upward Thrust. And this is not how the Golf Stroke works.
What actually happens is that the Club is Driven through Impact by an On Plane Force moving toward the Plane Line (1-L #10). That On Plane Force is the Right Forearm (itself Driven by either Muscular Thrust or Centrifugal Force). And that Right Forearm Drives Down Plane directly at the Plane Line until the Bent Right Arm has become Straight. This Full Extension does not occur until the end of the Follow-Through (6-A-4), and this is after the Clubhead has passed Low Point and is already on its way back Up and In. Therefore, it is crucial that the Player continue to direct his On Plane Thrust strongly Downward (and also Outward) directly at the Plane Line -- which is on the Ground and not "up" in the air somewhere -- even though the Ball has long gone and the Club has already begun its Upward journey toward the Finish (1-L #15).
At the end of the Follow-Through, both Arms are Straight, the Left Wrist has Rolled (or, far less desirably, Bent) and the Flail (the Left Arm and Club) has entered its Deceleration Phase (2-K #3). Thus, only Momentum is available to carry the Club to the Finish.
Again, at no time is there an Upward Thrust. There is only a Downward and Outward Thrust. I promise you that 100 percent of the golfers who are told to employ an "Uppercut Punch" will misinterpret the advice. In other words, they will not Drive the Right Forearm Down and Out directly toward the Plane Line (on the Ground) until the Right Elbow has fully-Straightened and the Right Arm Thrust has been exhausted.
I think it would have been appropriate to add "during the release interval". Just a suggestion!!!
DG
My discussion of the proper Direction of Thrust was not limited to the Release Interval. It included all Stroke Sections from The Top to The Finish (8-6 through 8-12).
When Yoda hits a ball, cover your ears, the sound is deafening.
Pure.
Thanks, Hans. While my Action hasn't yet caused a run on earplugs, it is true
that a Three Dimensional Impact definitely sounds different, even on
Short Shots (including Putts!). And it is the Downward Dimension --
taking the Stroke through the Impact Point all the way to Low Point -- that
is most often missing from even a good player's Impact.
Hybrid Mode
