Prestressed Shaft and Impact Deceleration

[jmessner]

In a 1981 GSEM Class discussion, Homer Kelley referred to two types of Clubshaft Bend for Swingers. The first -- "Acceleration Bend" -- stresses the top of the Shaft during the Start Down. During the second -- "Release Bend" -- the stress is opposite the Acceleration Bend as the toe of the Club attempts to get in line with the #3 Pressure Point.

The Hitter's stress is at the back of the Shaft and does not vary.

It's interesting that he mentioned both of these bending features because some of the guys doing advanced shaft fitting take into account the bending characteristics at different points (zones) in the shaft. Specifically, the swing tempo may be considered for "Acceleration Bend" (using your terminology) and release quality for "Release Bend".

As I mentioned earlier the "Release Bend" is generally toward the target for almost all golfers (for full swings) and is caused by the centrifugal force due to the clubhead speed pulling outward on the shaft through it's center of gravity - thus, CoG wants to line up with the shaft axis bending the shaft forward. That's why offset heads tend to hit the ball higher and could slightly correct a fade because the CofG is further behind the shaft and the shaft will tend to bend more forward with these heads. Ok - maybe too much information there.

Still a little dubious on the impact deceleration concept - but it may be a "real vs feel" thing in that it helps to think about accelerating through impact to avoid quitting, throwaway, etc.

[Yoda]

It's interesting that he mentioned both of these bending features because some of the guys doing advanced shaft fitting take into account the bending characteristics at different points (zones) in the shaft. Specifically, the swing tempo may be considered for "Acceleration Bend" (using your terminology) and release quality for "Release Bend".

As I mentioned earlier the "Release Bend" is generally toward the target for almost all golfers (for full swings) and is caused by the centrifugal force due to the clubhead speed pulling outward on the shaft through it's center of gravity - thus, CoG wants to line up with the shaft axis bending the shaft forward.

"'Release Bend' is generally toward the target for almost all golfers."

Thanks, jmessner. Your insights help us all!

[lagster]

It's interesting that he mentioned both of these bending features because some of the guys doing advanced shaft fitting take into account the bending characteristics at different points (zones) in the shaft. Specifically, the swing tempo may be considered for "Acceleration Bend" (using your terminology) and release quality for "Release Bend".

As I mentioned earlier the "Release Bend" is generally toward the target for almost all golfers (for full swings) and is caused by the centrifugal force due to the clubhead speed pulling outward on the shaft through it's center of gravity - thus, CoG wants to line up with the shaft axis bending the shaft forward. That's why offset heads tend to hit the ball higher and could slightly correct a fade because the CofG is further behind the shaft and the shaft will tend to bend more forward with these heads. Ok - maybe too much information there.

Still a little dubious on the impact deceleration concept - but it may be a "real vs feel" thing in that it helps to think about accelerating through impact to avoid quitting, throwaway, etc.

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Some pictures showing these bends would be nice... or are they too subtle to see?

[Rhythm]

We have some footage of players at the Zurich taken with a very high speed camera. We have exactly the type of pictures you want to see. And they will blow your mind when you see how much the shaft is stressed during these points during the swing. I had no idea the shaft actually bends this much. If you can tell me how to post some sings from V1 I can show what I am talking about. Incredible.

[Yoda]

We have some footage of players at the Zurich taken with a very high speed camera. We have exactly the type of pictures you want to see. And they will blow your mind when you see how much the shaft is stressed during these points during the swing. I had no idea the shaft actually bends this much. If you can tell me how to post some sings from V1 I can show what I am talking about. Incredible.

Chris needs help to help us, Bambam. Go get'em!

[jmessner]

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Some pictures showing these bends would be nice... or are they too subtle to see?

I'll show a couple, but I'm looking forward to the high-speed images from Rhythm. Most video cameras take 60 fields (or 30 frames per second) and it's hard to get a good field at just before impact. I've taken a couple of images from my CSwing video analysis program and yes the bends are kind of subtle but they are there. See what you think. Scott Verplank and Zach Johnson.

[armourall]

Lynn, it would be great to see you in front of a high speed camera executing both Swinging and Hitting procedures to capture the shaft bend for each.

I know you have no problem with typing "a thousand words" to describe it, but wouldn't a picture be easier?

[Daryl]

This thread has me particularly concerned about what I'm reading. Maybe I'm confused. (I just got a headache and took three Advil) It has always been and still is my understanding that one of the most important concepts in TGM, and it may be what everything boils down to, is a Pre-Stressed Clubshaft at impact for both Swingers and Hitters. The Bend is in the shape of a crescent, with the clubhead trailing the bent shaft, not leading it as the pictures above illustrate.

The purpose of a pre-bent clubshaft is to guard against impact deceleration. It's been my understanding that if you fail to pre-stress (bend) the shaft, the impact certainly will, with a loss of clubhead mass and speed at separation. Without pre-stressing the clubshaft then all the pre-impact work was for almost nothing.

Lag pressure, including swingers, is needed not only to trace the plane line but to maintain the pre-stressed clubshaft through impact and even till follow through. One should be able to feel the bend, at all times throughout the swing, and especially between release and impact. That's what the yellow book is all about (the other 241 pages are important too).

If centrifugal force stiffens the clubshaft and replaces the need for a pre-stressed clubshaft, then I'm going to stop swinging and become a Hitter. (as a Switter, I'm half way there anyway) Clear the lesson book Ted.

[Yoda]

Lynn, it would be great to see you in front of a high speed camera executing both Swinging and Hitting procedures to capture the shaft bend for each.

I know you have no problem with typing "a thousand words" to describe it, but wouldn't a picture be easier?

There is an extremely good chance we will be doing something soon. The folks at the Titlelist Performance Institute in Oceanside, California, have invited a short list of us out to do just this kind of thing. Their camera runs at 10,000 frames per second.

That should do it!

[12 piece bucket]

I'll show a couple, but I'm looking forward to the high-speed images from Rhythm. Most video cameras take 60 fields (or 30 frames per second) and it's hard to get a good field at just before impact. I've taken a couple of images from my CSwing video analysis program and yes the bends are kind of subtle but they are there. See what you think. Scott Verplank and Zach Johnson.

Do y'all think we're seeing Sequenced Release here? Or are these cats playing with a 10-2-D grip?